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AAS/AIAA Astrodynamics Specialist Conference

July 31 ‐ August 4, 2011 Girdwood, Alaska

AAS General Chair AIAA General Chair Ryan P. Russell William Todd Cerven Georgia Institute of Technology The Aerospace Corporation

AAS Technical Chair AIAA Technical Chair Hanspeter Schaub Brian C. Gunter University of Colorado Delft University of Technology

final post conference print version: .pdf created 8/8/2011 12:42 PM

Cover images:

Top right: Conference Location: Aleyska Resort in Girdwood Alaska.

Middle left: Cassini looking back at an eclipsed Saturn, Astronomy picture of the day 2006 Oct 16, credit CICLOPS, JPL, ESA, NASA;

Middle right: Shuttle shadow in the sunset (in honor of the end of the Shuttle Era), Astronomy picture of the day 2010 February 16, credit: Expedition 22 Crew, NASA.

Bottom right: Comet Hartley 2 Flyby, Astronomy picture of the day 2010 Nov 5, Credit: NASA, JPL-Caltech, UMD, EPOXI Mission

Table of Contents Registration ...... 5 Schedule of Events ...... 6 Conference Center Layout ...... 7 Conference Location: The Hotel Alyeska ...... 8 Transportation Info ...... 9 Activities Near the Hotel ...... 9 BE PREPARED! What to Pack ...... 10 Photos Of Area And Activities ...... 11 Hotel Alyeska Map ...... 12 Girdwood Map ...... 13 Anchorage Area Map ...... 14 Special Events ...... 15 Early Bird Reception ...... 15 Tram Ride/Dinner at Glacier Express Restaurant * ...... 15 Award Ceremony/Keynote Address Banquet* ...... 15 Additional Information ...... 16 Speaker Orientation ...... 16 Volunteers ...... 16 Presentations ...... 16 Preprinted Manuscripts ...... 16 Conference Proceedings ...... 16 Satisfaction Survey ...... 17 Committee and Subcommittee Meetings ...... 17 Session 1: Asteroid & NEO I ...... 18 Session 2: Orbital Debris I ...... 20 Session 3: Dynamical Systems Theory ...... 22 Session 4: Special Topic: Autonomous ...... 24 Session 5: Asteroid & NEO II ...... 26 Session 6: Trajectory Optimization I ...... 28 Session 7: Formation Flying I ...... 30 Session 8: Special Topic: Conjunction Assessment ...... 32 Session 9: Non- Orbiting Missions ...... 34 Session 10: Formation Flying II ...... 36 Session 11: Estimation I ...... 38 Session 12: Special Topic: ARTEMIS Mission ...... 40

Session 13: Planetary Mission Studies ...... 42 Session 14: Spacecraft GN&C ...... 44 Session 15: Constellations ...... 46 Session 16: Special Topic: MESSENGER at Mercury ...... 48 Session 17: Trajectory Optimization II ...... 50 Session 18: Attitude D&C I...... 52 Session 19: Orbit Estimation II ...... 54 Session 20: Spacecraft Autonomy ...... 56 Session 21: Orbital Debris II ...... 58 Session 22: Attitude D&C II ...... 59 Session 23: Orbit Estimation III ...... 60 Session 24: Space Environment ...... 61 Session 25: Trajectory Optimization III ...... 62 Session 26: Large Space Structures and Tethers ...... 64 Session 27: Optimal Control ...... 66 Session 28: Rendezvous ...... 68 Author Index ...... 70 Papers Sorted By Time Slot ...... 74 Record of Meeting Expenses ...... 77 Conference Satisfaction Survey ...... 79

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AAS/AIAA ASTRODYNAMICS SPECIALIST CONFERENCE INFORMATION

REGISTRATION

Registration Site (https://aas.pxi.com/registration/reg/ )

In order to encourage early registration, we have implemented the following conference registration rate structure: Register before July 1, 2011 and save $50!

Category Early Registration Standard (before July1, 2011) Registration Full - AAS or AIAA Member $505 $555 Full - Non-member $605 $655 Retired* $150 $200 Student* $150 $200 Tues night Tram Ride/Dinner Ticket $50 $50 Tues night Tram Ride/Dinner Ticket: Child age 5-12 (4 $25 $25 years and under is free) Wed night Awards/Keynote Speaker Banquet Ticket $50 $50 *does not include Tues or Wed night special events The Sunday night reception is included for all registrants. The Tues. and Wed. night Special Events are included only for Full registration fees. Space is limited and on-site sales of special event tickets may not be available (it is recommended to pay for tickets at the time of web registration) The Special Event on Tuesday night is a tram ride to the Glacier Express restaurant on top of the ski mountain (located at the resort). The event will include dinner and has no formal program, ideal for families. As the sun sets late there in the summer, guests are encouraged to bring their hiking shoes (and other precautions: jackets water bottles etc; see ‘BE PREPARED! What to Pack’ section of the program) and take the opportunity to explore some of the mountain. The Special Event on Wed night is a banquet dinner hosted at the conference site and will include the Breakwell student award ceremony and a Keynote address by Dr. Robert Braun, NASA’s current Chief Technologist.

On-site packet pick up and registration will be available on the following schedule: Sunday July 31 3:00 PM - 6:00 PM Monday Aug. 1 7:30 AM - 2:00 PM Tuesday Aug. 2 8:00 AM - 2:00 PM Wednesday Aug. 3 8:00 AM - 2:00 PM Thursday Aug. 4 8:00 AM - 10:00 AM

We will accept registration and payment on-site for those who have not pre-registered online, but we strongly recommend online registration before the conference in order to avoid delays (see URL above). Pre-registration also gives you free access to pre-print technical papers. On-site payment by credit card will be only through the AAS website using a computer at the registration table. Any checks should be made payable to the “American Astronautical Society.”

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SCHEDULE OF EVENTS

Day Start End Function Room

3pm 6 pm Registration Columbia Foyer July

Sun. 31 Sun. 6pm 9 pm Early Bird Reception Kahiltna Court

Day Start End Function Room 7am 8 am Speakers Breakfast Pond Cafe (upper balcony) 7:30 am 2 pm Registration Columbia Foyer 8am 11:50 am Session 1: Columbia A 8am 11:50 am Session 2: Columbia B 8am 11:50 am Session 3: Columbia C

8am 11:50 am Session 4: Kahiltna Court 9:40am 10:10 am Morning Break Columbia Foyer Noon 1:15 pm AAS Spaceflight Mechanics Committee Portage Board Room and Monday Monday 1 August Lunch Salon 1:20 pm 5:10 pm Session 5: Columbia A 1:20 pm 5:10 pm Session 6: Columbia B 1:20 pm 5:10 pm Session 7: Columbia C 1:20 pm 5:10 pm Session 8: Kahiltna Court 3:00 pm 3:30 pm Afternoon Break Columbia Foyer 7:00 pm 9:00 pm Student and Young Professional Reception Kahiltna Court

Day Start End Function Room 7am 8am Speakers Breakfast Pond Cafe (upper balcony) 8 am 2 pm Registration Columbia Foyer 8 am 11:50 am Session 9: Columbia A 8 am 11:50 am Session 10: Columbia B 8 am 11:50 am Session 11: Columbia C

8 am 11:50 am Session 12: Kahiltna Court 9:40am 10:10 am Morning Break Columbia Foyer Noon 1:15pm AIAA Astrodynamics Technical Committee Portage Board Room and Tuesday Tuesday 2 August Lunch Salon 1:20 pm 5:10 pm Session 13: Columbia A 1:20 pm 5:10 pm Session 14: Columbia B 1:20 pm 5:10 pm Session 15: Columbia C 1:20 pm 5:10 pm Session 16: Kahiltna Court 3:00pm 3:30pm Afternoon Break Columbia Foyer around 6pm 10 pm Glacier Express Event* Tram ride to mt. top *requires ticket. Trams will start running at 6PM and will run both ways all evening. There is no formal program, just a tram ride, dinner, and chance to socialize with a great view. Dinner will be served throughout evening so there is no hurry to be there at 6PM. There is space around the restaurant to hike and explore the mountain. Bring hiking shoes and appropriate gear (see ‘BE PREPARED! What to Pack’ section of the program) if interested.

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Day Start End Function Room 7am 8am Speakers Breakfast Pond Cafe (upper balcony) 8 am 2 pm Registration Columbia Foyer 8am 11:50 am Session 17: Columbia A 8am 11:50 am Session 18: Columbia B 8am 11:50 am Session 19: Columbia C 8am 11:50 am Session 20: Kahiltna Court 9:40am 10:10 am Morning Break Columbia Foyer

Noon 1:15 pm Joint Technical Committee Lunch Columbia Patio 1:20 pm 3:00 pm Session 21: Columbia A 1:20 pm 3:00 pm Session 22: Columbia B 3 August Wednesday Wednesday 1:20 pm 3:00 pm Session 23: Columbia C 1:20 pm 3:00 pm Session 24: Kahiltna Court 3:00pm 3:30 pm Afternoon Break Columbia Foyer 3:30 pm 4:30 pm Conference Administration Subcommittee Portage Board Room and Salon 3:30 pm 4:30 pm Technical Administration Subcommittee Kahiltna Court 3:30 pm 4:30 pm Website Administration Subcommittee Bering 6:00 pm 7:00 pm Pre-banquet cocktails Kahiltna Court 7:00 pm 9 pm Awards/Keynote Banquet (requires ticket) Columbia ABC

Day Start End Function Room 7am 8am Speakers Breakfast Pond Cafe (upper balcony) 8 am 10 pm Registration Columbia Foyer

8 am 11:30 am Session 25: Columbia A 8 am 11:30 am Session 26: Columbia B 4 August Thursday Thursday 8 am 11:30 am Session 27: Columbia C 8 am 11:30 am Session 28: Kahiltna Court 9:40am 10:10 am Morning Break Columbia Foyer

CONFERENCE CENTER LAYOUT

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CONFERENCE LOCATION: THE HOTEL ALYESKA The website is excellent and informant, see http://www.alyeskaresort.com

Welcome to The Hotel Alyeska, Alaska’s premier year-round resort destination. Nestled in a lush valley surrounded by mountain peaks, hanging glaciers and spectacular ocean views, The Hotel Alyeska offers our guests luxurious accommodations and convenient access to the magnificent Alaskan wilderness. We first opened our doors to guests in 1994. Today, our newly renovated chateau-style hotel makes the perfect base camp for your Alaskan vacation. During your stay here, you’ll experience supreme comfort with perfect modern touches and rich Native influences, bringing the natural beauty of Alaska’s great outdoors inside.

And with our average annual snowfall of 650 inches with 2,500 vertical feet of diverse terrain, and short lift lines, Alyeska Resort lives up to – and helps define – Alaska’s spectacular “steep and deep” reputation. And, Alyeska offers a mountain experience for all levels of skiers and riders.

Featured Guest Amenities: • 60-passenger aerial scenic tram • Saltwater pool, whirlpool & fitness center • Seven Glaciers Restaurant - AAA Four Diamond award-winning mountain-top dining • The Spa at Alyeska • Unique, world-class dining & shops • High-speed internet access in guest rooms • Complimentary high-speed wifi in common areas • Easy access to open space, nature trails & walking paths • StarbucksTM in-room coffee

Average Hi/Low Temperature in August 63oF/46oF August 2, 2011, Sunrise 5:33 AM; Sunset 10:39 PM

Alyeska Resort is located just 40 miles south of Anchorage along the scenic Seward Highway. The highway follows the Turnagain Arm, part of the Cook Inlet. To reach Alyeska Resort, follow signs to the town of Girdwood.

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TRANSPORTATION INFO

To and From the Airport Ted Stevens Anchorage International Airport (ANC) is a metropolitan hub serviced by multiple carriers year- round. The airport has close to 200 flights arriving daily with direct and connecting flights from most major US cities plus many international locations. The conference chairs recommend renting a car (parking is free at the Hotel Alyeska), however there are options for chauffeured transportation and can be arranged through the Concierge Desk at the Resort. You can reach the Concierge at 907-754-2108. Chauffeured options include a Sedan option (~$95 one way for up to 3 passengers), a Van option (~$120 one way for up to 6 passengers and ~$170 one way for over 6 passengers), and a Bus option for large number of passengers with varying prices. Guest are responsible for coordinating transportation to and from the airport.

Around Girdwood For public transportation in and around the Resort and the town of Girdwood, learn more about the Glacier Valley Transit. This service is complimentary for guests staying at The Hotel Alyeska.

Around Alaska The Alaska Railroad offers a scenic way to see the Alaska coastline and other major attractions. For your convenience, Girdwood has its own train station and hotel guests can arrange for pick-up and drop-offs depending on your itinerary. Popular Railroad Destinations:  Spencer Glacier (1/2 day)  Portage Glacier & Whittier  Seward & Kenai Fjords National Park  Denali National Park & Preserve The Alaska Railroad offers transportation-only fares as well as signature activity packages including a float trip, glacier viewing and dinner trains. Please contact the Concierge for more information and to make reservations, call 907-754-2108.

ACTIVITIES NEAR THE HOTEL Explore all that Alaska has to offer with the help of our travel experts at the Hotel Concierge Desk. In addition to the outdoor adventures right here at Alyeska Resort, Concierge connects our guests with adventures and activities for all interests and ages all year-round. The friendly and knowledgeable Concierge team (907-754- 2108) work with a variety of local and regional adventure providers, tour operators and other travel partners to ensure the best customer service and quality experience for your time and money.

Summer Activities Naturalist Walks Glacier Hikes Wildlife & Glacier Cruises Paragliding Flightseeing Mountain Biking Wildlife Viewing

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BE PREPARED! WHAT TO PACK

Alaska is known for ever-changing weather and a laid-back attitude. We recommend packing with a “Mountain Casual” style focused on comfort and convenience. When you venture outdoors, dress in layers to be prepared for the variable weather. The temperate coastal climate here at Alyeska Resort is characterized by long summer days with temperatures in the high 60’s but can quickly turn quite cold in the event of a weather front.

Suggested Summer Packing List:

 Rainproof wind-breaker with hood and pants  Insulation layer such as a fleece jacket or vest, and non-cotton base layesr such as long-underwear and tops. Please note: If you thinking of participating in any water sports (such as rafting or kayaking), it is important that you bring items that are not cotton. Good choices are polypropylene, nylon, and fleece.  Sturdy shoes & warm socks  Light ski hat, scarves & gloves. May seem silly in the summer but these items will really keep you warm if it gets unseasonably cold, or if you’re feeling the effects of glacier-chilled wind, without adding a lot of weight.  Sun Protection: lightweight, brimmed hat (sun and rain); sunglasses and sunscreen  Backpack or Tote Bag  Water Bottles  High protein snacks  Small First-Aid Kit  Binoculars

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PHOTOS OF AREA AND ACTIVITIES

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HOTEL ALYESKA MAP

http://www.alyeskaresort.com/Alyeska/SiteAssets/files/resort/summer_trail_map_10-11.pdf

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GIRDWOOD MAP

http://www.girdwoodchamber.com/assets/Uploads/maps/map.png

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ANCHORAGE AREA MAP

http://www.alyeskaresort.com/Alyeska/SiteAssets/files/travel-plans/VG07SouthcentralAlaskaMap.pdf

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SPECIAL EVENTS

EARLY BIRD RECEPTION Sunday, July. 31 6 – 9 PM Location: Kahiltna Court

TRAM RIDE/DINNER AT GLACIER EXPRESS RESTAURANT * Tues, Aug 2 around 6 pm– 10:00 pm Location: Top of the Aerial Tram at Glacier Express Restaurant

*requires ticket. Trams will start running at 6PM and will run both ways all evening. There is no formal program, just a tram ride, dinner, and chance to socialize with a great view. Dinner will be served throughout evening so there is no hurry to be there at 6PM. There is space around the restaurant to hike and explore the mountain. Bring hiking shoes and appropriate gear (see ‘BE PREPARED! What to Pack’ section of the program) if interested. Tickets are limited and will likely not be available after registration. We advise that guest tickets and non-full registrant tickets be purchased in advance through the website registration process.

AWARD CEREMONY/KEYNOTE ADDRESS BANQUET* Wed, 3 August 6:00pm -6:30pm (cocktails in foyer), 6:30-9 pm (banquet) Location: Columbia A/B/C

*requires ticket. Tickets are limited, we advise that guest tickets and non full registrant tickets be purchased in advance through the website registration process.

Breakwell Student Award Winners The following students will be honored as recipients of the Breakwell Travel Award:  Julie Parish, Texas A&M University, Advisor: John Hurtado  Carl Seubert, University of Colorado, Advisor: Hanspeter Schaub  Nitin Arora, Georgia Institute of Technology, Advisor: Ryan P. Russell

Best Paper Award Kohei Fujimoto and Daniel J. Scheeres will be honored for their Paper AIAA 2010-7975 entitled “Correlation of Optical Observations of Earth-Orbiting Objects by Means of Probability Distributions” that was voted as Best Paper from the AAS/AIAA Astrodynamics Specialist Conference and Exhibit in Toronto, Canada, Aug 2010.

Keynote Speaker Robert D. Braun: NASA Chief Technologist As NASA’s Chief Technologist, Braun serves as the principal advisor and advocate on matters concerning agency-wide technology policy and programs.

Braun has more than 20 years experience performing design and analysis of planetary exploration systems as a member of the technical staff at NASA's Langley Research Center in Hampton, Va., and as a faculty member in the Guggenheim School of at Georgia Institute of Technology. His research has focused on systems' aspects of planetary exploration, where he contributed to the design, development, test and operation of several robotic space flight systems Braun received a B.S. in Aerospace Engineering from Penn State in 1987, M.S. in Astronautics from the George Washington University in 1989, and Ph.D. in Aeronautics and Astronautics from Stanford University in 1996. Braun has received the 1999 AIAA Lawrence Sperry Award, two NASA Exceptional Achievement Medals, two NASA Inventions and Contributions Team Awards, and seven NASA Group Achievement Awards. He is an AIAA Fellow and the principle author or co-author of over 175 technical publications.

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ADDITIONAL INFORMATION

SPEAKER ORIENTATION On the day of their sessions, authors making presentations meet with their session chairs in the upper balcony of the Pond Cafe at 7:00 am each morning. A continental breakfast will be served. Speaker attendance is mandatory.

VOLUNTEERS Volunteers are requested to help staff the registration table during the conference. Please inquire at the registration table. THANKS!

PRESENTATIONS Each presentation is limited to 15 minutes. An additional five minutes is allotted between presentations for audience participation and transition. Session chairs shall maintain the posted schedule to allow attendees the option of joining a parallel session. Each room is equipped with a microphone, a laser pointer, an electrical outlet, and a video projector that can be driven by a computer. Presenters shall coordinate with their Session Chairs regarding the computing equipment, software, and media requirements for the session; however, each presenter is ultimately responsible for having the necessary computer and software available to drive the presentation. Microsoft PowerPoint and PDF are the most common formats. "No-Paper, No-Podium" Policy Completed manuscripts shall be electronically uploaded to the submission site before the conference, limited to 20 pages in length, and conform to the AAS conference paper format. If the completed manuscript is not contributed on time, it will not be presented at the conference. If there is no conference presentation by an author, the contributed manuscript shall be withdrawn.

PREPRINTED MANUSCRIPTS Physical copies of preprinted manuscripts are no longer available or required for the Space Flight Mechanics Meetings or the Astrodynamic Specialist Conferences. Electronic preprints are available for download at least 72 hours before the conference at https://events.pxi.com/aas/reg/ for registrants who use the online registration system. The hotel provides conference guests with free wireless internet access in guest rooms and the conference meeting space. Registrants without an internet-capable portable computer, or those desiring traditional paper copies should download and print preprint manuscripts before arriving at the conference.

CONFERENCE PROCEEDINGS All FULL registrants will receive a CD of the proceedings mailed to them after the conference (extra copies are available for $45 during the conference). However, the hardbound volume of Advances in the Astronautical Sciences covering this conference will be available to attendees at a reduced pre-publication cost, if ordered at the registration desk. After the conference, the hardbound proceedings will more than double in price, although authors will still receive a special 50% discount even if they delay their order until after the conference. Cost of Proceedings: Conference Rate $290 (approx.) Conference Rate (international shipping) $360 (approx.)

Although the availability of hardcopy proceedings enhances the longevity of your work and elevates the importance of your conference contribution, please note that conference proceedings are not considered an

Page 16 2011 AAS/AIAA Astrodynamics Specialist Conference, Girdwood, Alaska archival publication. Authors are encouraged to submit their manuscripts after the meeting to one of the relevant journals, such as: Journal of Guidance, Control and Dynamics Editor-in-Chief: George T. Schmidt, Massachusetts Institute of Technology Manuscripts can be submitted via: http://www.writetrack.net/aiaa/ Journal of Spacecraft and Rockets Editor-in-Chief: E. Vincent Zoby, NASA Langley Research Center Manuscripts can be submitted via: http://www.writetrack.net/aiaa/ Journal of the Astronautical Sciences Editor-in-Chief: Kathleen C. Howell [email protected]

SATISFACTION SURVEY Registrants are highly encouraged to record their level of satisfaction and conference preferences in an anonymous survey taken throughout the time of the conference. Please return the survey form included in this program to the registration table before departing from the conference.

COMMITTEE AND SUBCOMMITTEE MEETINGS Committee seating is limited to committee members and invited guests. Committee and subcommittee meetings will be held according to the schedule at the beginning of the program

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Aug 1, 2011 Columbia A Session 1: Asteroid & NEO I Chair: Ryan Park, JPL

08:00 AAS 11 - 400 An Analysis of Multiple-Revolution Third Body Driven Plane Change Maneuvers Eric Trumbauer and Benjamin Villac, Ph.D., University of , Irvine. Third-body forces can greatly affect the of spacecraft orbiting moons and small bodies. These forces can be harnessed to induce controlled orbital maneuvers such as plane changes. Previous studies have focused on a single revolution to effect these maneuvers. This paper extends this by considering multiple periapsis passages before recircularization. The performance envelope is evaluated and compared to previous studies. While the gains are modest in feasible cases, interesting structures emerge in relation to escape, capture, and libration point dynamics. These present opportunities for mapping nearby regions suitable for transfers to and from scientifically interesting near-polar .

08:20 AAS 11 - 402 Application of Wide-Field Integration of Optic Flow to Proximity Operations and Landing for Space Exploration Missions Michael A. Shoemaker and Shinji Hokamoto, Kyushu University New advances in vision-based navigation for micro air vehicles (MAVs) have been inspired by the biological systems of flying insects. These biologically-inspired optical sensor systems for MAVs are computationally efficient and have low mass and low power consumption. The characteristics that make these vision-based methods useful for MAVs may also make them useful for spacecraft, especially small, low-cost vehicles. This study explores the applicability of these navigation systems that use insect-vision-based processing of optic flow, specifically wide-field integration of optic flow, to space exploration missions. The examples considered include proximity operations and descent and landing phases on small-bodies and planets. 08:40 AAS 11 - 403 Comparison of Fragmentation/Dispersion Models for Asteroid Nuclear Disruption Mission Design Brian D. Kaplinger and Bong Wie; Iowa State University This paper considers developing orbit predictions of near-Earth object (NEO) fragmentation for nuclear disruption mission design. The critical component of NEO fragmentation is developed for a momentum-preserving hypervelocity impact. The results of the fragmentation process are compared to static models and results from complex hydrodynamic code simulations, developing benchmark conditions for orbital prediction. The problem is examined in a way that enables GPU acceleration of the resulting system, and the mission design fidelity is improved to allow for self-gravity and collision models between NEO fragments. Improvements to model efficiency are demonstrated using a range of orbits to assess mission effectiveness. 09:00 AAS 11 - 404 Dynamics and Stability in a Triple Asteroid System Julie Bellerose, Carnegie Mellon University Silicon Valley / NASA ARC We now count two triple asteroid systems in the Near-Earth Asteroid population. There is a need to understand the scale of perturbations and stability for spacecraft applications in such environment. We look at the dynamics of triple systems, starting from a two-body and a restricted three body dynamical models, where the mass distribution of one of the bodies is taken into account. We numerically investigate the importance of an added component, and on a point mass or spacecraft, and numerically look at the long-term stability of such systems. 09:20 AAS 11 - 405 Implementation of the NSTAR thruster to support Gravity-Tractor operations Dario O. Cersosimo, University of Missouri The NSTAR ion engine model, designed for the DS1 and Dawn missions, is implemented in a gravity- tractor spacecraft to support hovering operations. The model takes under consideration the operational limits of the thruster as well as the Isp profile for varying throttling levels. A gravity-tractor system was modeled and subject to operate under different guidance laws over a variety of asteroid configurations. Our results indicate the importance of an accurate propulsion system model for the gravity-tractor by showing that under certain scenarios, the propellant efficiency of the dynamic hovering laws is improved with respect to the classical inertial hovering. 09:40 Break

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10:10 AAS 11 - 406 Validation of a Finite Sphere Gravitation Model with Applications to Comet 67P/Churyumov-Gerasimenko Paul V. Anderson and Bogdan Udrea, Embry-Riddle Aeronautical University Improved finite element methodology for estimating small body gravitational fields is validated through numeric analyses of asteroid Itokawa. The model implements uniform spherical elements of two sizes to obtain a fill ratio that approximates the asteroid shape model geometry to nearly 100% efficiency. The gravitational model is applied to the geometry of comet 67P/Churyumov-Gerasimenko and employed to analyze orbital dynamics and stability of ESA's Rosetta spacecraft during initial stages of the comet mapping and characterization phase in the comet environment. 10:30 AAS 11 - 408 Earth-Impact Probability Computation of Disrupted Asteroid Fragments Using GMAT/STK/CODES Alan Pitz, Chris Teubert, and Bong Wie, Iowa State University There is a nationally growing interest in the use of a high-energy nuclear disruption/fragmentation option for mitigating the impact threat of near-Earth objects (NEOs) with a short warning time. Consequently, the orbital dispersion and impact probability computation problem of a disrupted/fragmented NEO has been examined with high-fidelity visualizations using several computer programs, called General Mission Analysis Tool (GMAT) developed by NASA, AGI’s Satellite Tool Kit (STK), and Jim Baer’s Comet/asteroid Orbit Determination and Software (CODES). Our current research effort will result in an engineering tool to study the consequence of a high-energy nuclear disruption mission for hazardous NEOs. 10:50 AAS 11 - 409 The Probability of Asteroid-Earth Collisions by way of the Positional Uncertainty Ellipsoid Christopher J. Polito and David B. Spencer, The Pennsylvania State University An alternative to the conventional method for determining impact probability by an asteroid is presented that utilizes the positional uncertainty ellipsoid. This method is used commonly for Earth- orbiting satellite collision probability. In the scaling up process, the gravitational influence of one of the bodies in the collision is taken into account, namely that of the Earth. The restricted three-body problem is sufficient to provide a backdrop for the probability analysis, while making sure to note thatthe results are only hypothetical given a simplified dynamic model. Uncertainty is represented mathematically by the covariance matrix and is propagated into the future.

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Aug 1, 2011 Columbia B Session 2: Orbital Debris I Chair: Dr. Thomas Starchville, The Aerospace Corporation

08:00 AAS 11 - 410 100-Year Debris Population Model Alan B. Jenkin, Marlon E. Sorge, Glenn E. Peterson, John P. McVey, Bernard B. Yoo, The Aerospace Corporation This paper presents a process to generate discrete future low Earth orbit debris populations for input to space system performance simulations. This process has several features that are different from previously developed debris prediction models, including use of the IMPACT breakup model and logarithmic down- sampling. Results show that the debris population caused by the current tracked population will grow even without future launches. Intact objects were ranked in terms of their potential to result in debris creation. Results preliminarily indicate that collisions between large and small untracked objects may generate signifi- cant amounts of second generation debris.

08:20 AAS 11 - 411 Analyzing The Criteria For A Stable Environment Benjamin Bastida Virgili. and Holger Krag, ESA Office. ESA/ESOC. The number of human made objects in space has not stopped increasing since the beginning of spaceflight. Latest model predictions show that the population has already reached a point, where the number of objects would increase even without further human interaction. This means that also current mitigation measures are insufficient to stop this growth. In this study, with the help of an environment prediction model, we will investigate the drivers for the instability and propose solutions to achieve the stability based on a reformulation of the mitigation measures and on active removal missions. 08:40 AAS 11 - 412 Automated Ballistic Coefficient Estimation Technique to Analyze the Debris from the COSMOS-2251 and IRIDIUM-33 Collision John McVey and Chia-Chun Chao, The Aerospace Corporation The collision of the Cosmos-2251 and Iridium-33 generated thousands of debris fragments. A ballistic coefficient estimation technique was developed to analyze these fragments and to extract information about the debris clouds for use in fragmentation models and other analyses. In order to characterize debris clouds, an automated estimation process was developed. The resulting ballistic coefficient estimate distributions from these debris clouds are distinctly different from each other and could yield information about the characteristics of the collision, which will aid in the determination of the characteristics of future collisions. 09:00 AAS 11 - 413 Determination of Orbit Cross-Tag Events and Maneuvers With Orbit Detective D.L. Oltrogge and Sal Alfano, Analytical Graphics Inc. Cross-tag and orbit maneuver events can often be detected using a low-pass based upon pre- and post-event statistics accumulation. In this paper we exam-ine the implementation of such a filter in the Orbit Detective tool, and we apply it to the Galaxy 15mission to determine cross-tag frequency of occurrence. Ma-neuver detection and calibration are also demonstrated on a few cases. 09:20 AAS 11 - 414 Effect Of Future Space Debris On Mission Utility And Launch Accessibility Glenn E. Peterson, The Aerospace Corporation This paper examines the effect that future growth of space debris in Low Earth Orbit will have on two aspects of space operations: on-orbit mission utility and launch accessibility. Three size regimes of debris are examined: >10 cm (cur-rently tracking capability), >5 cm (future upgraded tracking system), and >1 cm (potentially destructive to vehicle). Results show that the number of actions (i.e., extra requests for tracking, maneuvers, etc.) for certain orbit regimes may be large enough to affect mission and launch operations as will the potential amount of closures. 09:40 Break

10:10 AAS 11 - 415 Effects on Orbit Decay due to CO2 Growth in the Atmosphere C. C. Chao and B. B. Yoo, The Aerospace Corporation Based on a 3-stage linear model for CO2 growth, effects on orbit lifetime of LEO spacecraft were estimated using a semi-analytic orbit propagation tool, LIFETIME. Orbit lifetime can increase from 5% to as large as 67% depending on initial orbit altitude, ballistic coefficient and launch date. The Inter- Agency Space Debris Coordination Committee (IADC) requires that a spacecraft must reserve adequate fuel to lower the perigee at end of life for natural reentry due to atmosphere drag decay within 25 years. The significantly increased orbit lifetime will result in increased fuel requirement for ensuring the natural decay time of a spacecraft.

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10:30 AAS 11 - 416 Getting to Know Our Space Population From the Public Catalog D.L. Oltrogge and T.S. Kelso, Analytical Graphics, Inc. Our space population continues to increase as satellites are launched and debris-producing catastrophic events occur. For operators and policy makers, a periodic examination of the publicly- available space population is useful. In this paper, bivariate distributions and visualizations of orbital elements and simple spatial density metrics clearly delineate regions of higher collision risk. For the highest risk region, benefits ob-tained by application of ISO orbital debris mitigation standards are discussed. Application of concentric spherical zone "Ring Shells" governed in latitude by object maximum latitude distribution helps provide a more realistic spatial density and collision probability picture compared with previous analyses. 10:50 AAS 11 - 417 Laser Tracking of Space Debris for Precision Orbit Determination Craig Smith, Yue Gao, Jizhang Sang and Ben Greene, EOS Space Systems The threat posed by space debris to operational space craft was clearly demonstrated by the 2009 collision between an active Iridium satellite and the defunct Cosmos spacecraft. Even though both objects are routinely tracked by the US Space Surveillance Network, the orbital information provided was not of sufficient accuracy to allow reliable prediction of the crash. Active laser tracking of space objects offers very high precision orbit determination, locating uncooperative objects to within a few meters. This paper will describe the laser tracking systems and provide some results from some tracking demonstrations and precision orbit determinations. 11:10 AAS 11 - 418 Mitigating Potential Orbital Debris: The Deorbit of a Commercial Spacecraft Tim Craychee, Applied Defense Solutions; Shannon Sturtevant, Independent In the spring of 2011, a commercial spacecraft (object # 27838) performed a final maneuver that sent the spacecraft into Earth's lower atmosphere resulting in a reentry event beginning over the southern Pacific Ocean. While it is not known if any debris of the spacecraft survived reentry, if any pieces did survive, the final orbit was designed such that they would impact within a "safe zone" defined in the Pacific Ocean. The purpose of this paper is to report the deorbit trajectory design and implementation. 11:30 AAS 11 - 419 Satellite collision probability computation for long term encounters Juan-Carlos Dolado and Xavier Pena, French space agency (cnes); Romain Garmier and Bruno Revelin, cs-si; Paul Legendre, cemaes With the significant increase on the number of satellite constellations and GEO objects, long term encounters become common. Such geometries are characterized by a curvilinear relative motion and important position and velocity uncertainties. We first determine the relative velocity limits between the linear and non-linear encounters and the limits between negligible or not negligible velocity uncertainties. We then proposed an algorithm combining a monte carlo and an important sampling method to compute the collision probability for the curvilinear domain. We finally apply this algorithm on various encounters to demonstrate its efficiency in terms of accuracy and computation time.

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Aug 1, 2011 Columbia C Session 3: Dynamical Systems Theory Chair: Jon Sims, Jet Propulsion Laboratory

08:00 AAS 11 - 420 A New Look at the Planar Dynamics of Libration-Orbit Coupling for Spacecraft Jay McMahon and Daniel Scheeres, University of Colorado - Boulder In this paper, we present a new analysis for the stability of planar dynamics of a librating spacecraft in Earth orbit. Due to the small amount of coupling, many studies separately analyze the orbit and attitude dynamics. Here, we keep the dynamics coupled and study the limits of the librational and orbital motion for different energy and angular momentum levels. We present a comprehensive analysis of the initial conditions which lead to a gravity gradient spacecraft beginning to circulate (reaching libration angles of greater than 90 degrees), in terms of state variables and their relationship to orbital elements

08:20 AAS 11 - 421 Applications of trajectories in the vicinity of Sun-Earth L3 for a solar observation mission Jon F.C. Herman and Ron Noomen, Delft University of Technology; Kathryn E. Davis and George H. Born, University of Colorado This paper investigates trajectories in the vicinity of the Sun-Earth L3 for solar observation purposes. The research aims for a better understanding of trajectories in the vicinity of L3, which to date has been studied to a limited extent in any three-body system. The increasing interest for solar science missions includes a desire for prolonged observations of the far side and the higher latitude regions of the Sun, which may be possible by placing a single spacecraft in the vicinity of L3. Additionally, results obtained in this research may be translated to other three-body systems, such as the Earth- Moon system. 08:40 AAS 11 - 423 Comparison of Low-Energy Lunar Transfer Trajectories to Invariant Manifolds Rodney L. Anderson and Jeffrey S. Parker, Jet Propulsion Laboratory In this study, transfer trajectories from the Earth to the Moon that encounter the Moon at various flight path angles are examined, and lunar approach trajectories are compared to the invariant manifolds of selected unstable orbits in the circular restricted three-body problem. Previous work focused on lunar impact and landing trajectories encountering the Moon normal to the surface, and this research extends the problem with different flight path angles in three dimensions. The costs for a range of Jacobi constants are computed, and approaches to the Moon via invariant manifolds from unstable orbits are analyzed directly for different energies. 09:00 AAS 11 - 424 Estimation Strategies for Dynamical Systems with Equality Constraints Julie J. Parish and John E. Hurtado, Texas A&M University Constrained dynamical systems are common in spacecraft and aerospace robotics. For the class of systems subject to equality constraints, monitoring constraint violation is useful for determining the more appropriate dynamical model of the system. In this paper, two strategies for sequentially estimating the states and constraint are presented with examples. The first method constructs the constraint estimate and variance from the linearized constraint relationship and state estimates, whereas the secondmethod directly estimates both the constraint and variance. The constraint variance is then used to calculate uncertainty bounds for determining constraint violation and subsequently selecting the appropriate system model. 09:20 AAS 11 - 425 Flybys in the circular, restricted, three-body problem Stefano Campagnola, Jet Propulsion Laboratory, Ryan P. Russell, Georgia Tech; Paul Skerritt, California Institute of Technology This paper presents a new analysis of the flyby in the planar, circularm restricted three-body problem that is inspired by the Keplerian map and by the Tisserand-Poincare' graph. The analysis gives new insight on the flyby dynamics and on the accuracy of the linked-conics model. It also suggest a simple way to design multiple flyby trajectories on the T-P graph, which will be presented in a follow-up paper. 09:40 Break

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10:10 AAS 11 - 426 Input-Output Identification of Discrete-Time Bilinear State-Space Models Haris Celik, Ericsson and Royal Institute of Technology; Minh Q. Phan, Dartmouth College This paper presents a technique to identify the input-output maps of discrete-time bilinear state-space models. The new method requires input-output data from only one experiment, the input data need not be of special types such as sinusoidal or multiple pulses, and the initial conditions can be non- zero and unknown. Recent methods, on the other hand, require data from multiple experiments, specialized input signals, and zero initial conditions. The identified input-output model can be used to predict thebilinear system response directly without having to return to the bilinear state-space format. Numerical examples are provided to illustrate the identification method. 10:30 AAS 11 - 427 Multi-Body Capture to Low-Altitude Circular Orbits at Europa Daniel J. Grebow and Anastassios E. Petropoulos, Jet Propulsion Laboratory Assuming the final science orbit of NASA's Jupiter-Europa Orbiter is a 200-km circular Europan orbit, we present the results of a methodical search for efficient capture trajectories in the Jupiter-Europa Restricted Three-Body Problem. The insertion cost can be significantly reduced by exploiting multi- body effects, in some cases saving up to 40% of the delta-v computed from the patched-conic, two- body problem. The transfer trajectories are evaluated in terms of apojove performance, and, based on current mission planning and geometry, capture trajectories are selected and attached to a fully integrated n-body baseline mission. 10:50 AAS 11 - 428 Poincaré Maps and Resonant Orbits in the Restricted Three-Body Problem Mar Vaquero and Kathleen C. Howell, Purdue University The application of dynamical systems techniques to mission design has demonstrated that employing invariant manifolds and resonant flybys enables previously unknown trajectory options and potentially reduces the delta-V requirements. An analysis of planar resonant orbits, as well as the computation and visualization of the associated invariant manifolds is explored in this analysis. Poincaré maps are an effective tool in the search for unstable resonant orbits and potential resonant transitions. Connections between the invariant manifolds associated with two-dimensional unstable resonant orbits for different energy levels are identified in the Saturn-Titan system. Resonant periodic homoclinic- and heteroclinic-type connections are also summarized.

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Aug 1, 2011 Kahiltna Ct Session 4: Special Topic: Autonomous Aerobraking Chair: Angela Bowes, NASA LaRC

08:00 AAS 11 - 473 Autonomous Aerobraking: A Design, Development, and Feasibility Study Jill L. Prince and Dan Murri, NASA Langley Research Center; Richard W. Powell, Analytical Mechanics Association Aerobraking is used to deliver a spacecraft into orbit around a planetary body with a significant atmosphere utilizing atmospheric drag to decelerate the spacecraft. A study in autonomous aerobraking development has been sponsored by the NESC to determine initial feasibility of equipping a spacecraft with the onboard capability for autonomous aerobraking, thus saving millions of dollars in staff and DSN coverage. This paper describes the need for autonomous aerobraking, the development and preliminary results of the Autonomous Aerobraking Development Software that includes an ephemeris estimator and maneuver calculation, and the plan forward for continuation of this study.

08:40 AAS 11 - 474 Autonomous Aerobraking: Thermal Analysis and Response Surface Development John A. Dec and Mark N. Thornblom, NASA Langley Research Center A high fidelity thermal model of the Mars Reconnaissance Orbiter has been developed for use in an autonomous aerobraking simulation study. Response surface equations are derived from the high fidelity thermal model and integrated into the autonomous aerobraking simulation software. The high fidelity thermal model was developed using the Thermal Desktop software and the software was used in all phases of the analysis. The use of Thermal Desktop exclusively represents a change from previously developed aerobraking thermal analysis methodologies. Comparisons are made between the Thermal Desktop solutions and those developed for the previous aerobraking thermal analysis performed on the Mars 09:00 AAS 11 - 478 The Next Generation of Mars-GRAM and Its Role in the Autonomous Aerobraking Development Plan Hilary L. Justh, NASA Marshall Space Flight Center; Carl G. Justus, Dynetics; Holly S. Ramey, Jacobs ESTS Group The Mars Global Reference Atmospheric Model (Mars-GRAM) is an atmospheric model widely used for diverse mission applications. Mars-GRAM was used during , Mars Odyssey and Mars Reconnaissance Orbiter aerobraking operations. In previous versions, Mars-GRAM was less than realistic when used for sensitivity studies at large, user-specified optical depth values (e.g. tau=3). Mars-GRAM 2010 includes adjustment factors that correct this inaccuracy. These factors were derived by a comparison analysis between Mars-GRAM, and Thermal Emission Spectrometer (TES) and aerobraking data from the Planetary Data System. The new Mars-GRAM factors result in improved density estimates versus latitude, and time of year. 09:20 AAS 11 - 477 Onboard Atmospheric Modeling and Prediction for Autonomous Aerobraking Missions Robert H. Tolson, North Carolina State University Jill L. H. Prince, NASA Langley Research Center Successful autonomous aerobraking requires onboard estimation of density profiles of past aerobraking passes and onboard prediction of the density profile for future passes. Mars, Venus and Titan are potential targets for autonomous aerobraking missions. Mars provides a challenging environment for aerobraking due to the large orbit to orbit variability in atmospheric density. High variability is expected on Venus' night side. Little is known about relevant variability at Titan. Methods are evaluated for representing density profiles, for recovering profile parameters from IMU data, and for optimal combinations of profiles for prediction. Algorithms simplicity and robustness are maintained to accommodate onboard limitations. 09:40 Break

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10:10 AAS 11 - 476 Implementation and Simulation Results Using Autonomous Aerobraking Development Software Robert W. Maddock, Alicia Dwyer Cianciolo, Angela Bowes, Jill L. Prince, NASA Langley Research Center; Robert H. Tolson, National Institute of Aerospace; Richard W. Powell, Analytical Mechanics Associates Autonomous Aerobraking is under development with support from the NASA Engineering and Safety Center to move typically ground-based functions to onboard an aerobraking space-craft, reducing risk and mission cost. The suite of software that will employ autonomous aero-braking is the Autonomous Aerobraking Development Software (AADS) and consists of an ephemeris model, onboard atmosphere estimator, temperature/loads prediction, and maneuver calculation. Resultant maneuver timing and magnitude is sent to the spacecraft to maintain peri- parameters within design structural load and thermal constraints. The AADS is tested in simulation at Mars, Venus, and Titan. 10:30 AAS 11 - 471 Autonomous Aerobraking Algorithm Testing In Flight Software Simulation Environment David Carrelli, James Kaidy, Daniel O’Shaughnessy and Thomas Strikwerda, Johns Hopkins University/Applied Physics Laboratory Aerobraking has been used successfully for achieving the desired spacecraft orbit for a number of missions, but it requires significant resources for tracking, navigation, modeling and maneuver planning. NASA is now exploring the transition of the technology to a spacecraft environment to enable autonomous aerobraking. This paper describes the modifications to flight and testbed software from an actual interplanetary mission that were made to incorporate aerobraking and navigation algorithms. The flight algorithm architecture will be presented along with the timeline for a typical orbit and preliminary simulation results from one or more candidate bodies and a range of conditions.

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Aug 1, 2011 Columbia A Session 5: Asteroid & NEO II Chair: Dr. Shyam Bhaskaran, Jet Propulsion Laboratory

13:20 AAS 11 - 440 A new approach on the long term dynamics of NEO's under Yarkovsky effect Jesus Pelaez, Hodei Urrutxua, Isabel Perez-Grande and Claudio Bombardelli, Technical University of Madrid To calculate the force associated with the Yarkovsky effect the temperature distribution on the surface of the asteroid should be determined; it depends on the asteroid orbit, size and shape, spin axis orientation and period, mass, density of surface layers, albedo, thermal conductivity, capacity and IR emissivity of the material. The uncertainty of many of these parameters invites to develop simplified methods to calculate the influence of the Yarkovsky effect on long term dynamics of asteroids. In this paper we present one of this method based in a special procedure developed in our group.

13:40 AAS 11 - 441 A Survey of Human-Precursor Robotic Asteroid Missions Michael Cupples, Raytheon Missile Systems; Roberto Furfaro, Dan Wibben and John Kidd, ; Carl Hergenrother, University of Arizona Lunar Planetary Laboratory A survey of conceptual robotic asteroid missions that are precursor to potential human asteroid missions is provided, yielding a set of parametric data that can be used for preliminary robotic mission planning. For a set of nineteen carefully chosen asteroids, this study generated a table of delta-v and trajectory data that extends over a range of launch opportunity dates and a range of total transfer times. Further work develops a set of corresponding conceptual Human missions related to the nineteen asteroids that includes parameterization of total mission time and asteroid stay time on mission delta-v. 14:00 AAS 11 - 444 Methodology and Results of the Near-Earth Object (NEO) Human Space Flight (HSF) Accessible Targets Study (NHATS) Brent Wm. Barbee and Ronald G. Mink, NASA-GSFC; Daniel R. Adamo, Astrodynamics Consultant Near-Earth Asteroids (NEAs) have been identified by the administration as potential destinations for human explorers during the mid-2020s. Planning such ambitious missions requires selecting potentially accessible targets from the growing known population of over 7,800 NEAs. NASA is therefore conducting the Near-Earth Object (NEO) Human Space Flight (HSF) Accessible Targets Study (NHATS). While the NHATS algorithms have identified hundreds of NEAs which satisfy purposely inclusive trajectory constraints, only a handful offer attractive mission opportunities. In this paper we will detail the NHATS algorithms, present current study results, and discuss mission design for future human missions to NEAs. 14:20 AAS 11 - 443 Launch Analysis Supporting Human-Precursor Robotic Asteroid Missions Badejo Adebonojo, Michael Cupples, Raytheon Missile Systems; Roberto Furfaro, University of Arizona. For a set of nineteen carefully selected asteroids, analyses have been conducted determining impact on LV performance in reaching the optimal Earth departure conditions for missions to the asteroids. The impact to launch vehicle payload delivery will be analyzed in response to reaching the required Declination of the Launch Asymptote (DLA) for the optimal mission C3. Analysis results will be presented utilizing the launch vehicle vendor data to assess the capability of the launch vehicles of achieving the designed optimal launch asymptote. Impact of the effects of launch azimuth on range safety for for the mission will also be considered. 14:40 AAS 11 - 445 Mission Analysis and Transfer Design for the European Student Moon Orbiter Willem van der Weg and Massimiliano Vasile, University of Strathclyde The European Student Moon Orbiter is scheduled for launch in 2014-2015, making it the first lunar micro-satellite designed entirely by students, and the only currently planned ESA mission to the Moon. The limited deltaV budget and the requirement to be a piggyback payload made the design of feasible transfers to the Moon challenging. To fully study the launch window, a generation algorithm was created to make a large database of WSB transfers. Between launch and departure ESMO will perform a series of maneuvers that exploit natural perturbations to inject into a trans-lunar transfer within the limits of the propulsion system. 15:00 Break

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15:30 AAS 11 - 446 Near-Earth Asteroids Accessible to Human Exploration with High-Power Electric Propulsion Damon Landau and Nathan Strange, Jet Propulsion Laboratory The diverse physical and orbital characteristics of near-Earth asteroids provide progressive stepping stones on a flexible path to Mars. Beginning with cis-lunar exploration capability, the variety of accessible targets steadily increases as technology is developed for eventual missions to Mars. Noting the potential for solar electric propulsion to dramatically reduce launch mass for Mars exploration, we apply this technology to expand the range of candidate asteroid missions. A robust and efficient exploration program emerges where a potential mission is available once per year (on average) with technology levels that span cis-lunar to Mars-orbital capabilities. 15:50 AAS 11 - 447 Orbit Options for an Orion-Class Spacecraft Mission to a Near-Earth Object Nathan C. Shupe and Daniel J. Scheeres, University of Colorado at Boulder This study seeks to identify candidate orbit options for a crewed mission to a Near-Earth Object (NEO) using an Orion-class spacecraft. A model including multiple perturbations (solar radiation pressure, solar gravity, non-spherical mass distribution of the central body) to two-body dynamics is constructed to numerically integrate the motion of a satellite in close proximity to a small body in an elliptical orbit about the Sun. Simulations about NEOs possessing various physical parameters (size, shape, rotation period) are then used to empirically develop general guidelines for establishing orbits of an Orion-class spacecraft about a NEO. 16:10 AAS 11 - 448 Small-Body Gravity Field Approximation Methods Patel Parv, Phillips Robert and Bogdan Udrea, Embry-Riddle Aeronautical University Small celestial bodies such as asteroids and comets are the target of space exploration missions, which have revived pronounced interest in aerospace communities for the design of orbits. Characterizing their orbital environmental is essential in planning such missions, requiring precise gravity field models. These bodies typically possess very irregular shapes, which poses a challenging astrodynamics problem. This paper offers alternative approaches for modeling the gravity fields of these bodies by using variable element definitions. In addition, the various simulated gravity field models are compared with that of a polyhedron shape model to verify their accuracy and feasibility for practical applications. 16:30 AAS 11 - 449 Why Atens Enjoy Enhanced Accessibility For Human Space Flight Daniel R. Adamo, Independent Astrodynamics Consultant; Brent Wm. Barbee, NASA Goddard Spaceflight Center Near-Earth objects can be grouped into multiple orbit classifications, among them being the Aten group, whose members have orbits crossing Earth's with semi-major axes less than 1 astronomical unit. Atens comprise well under 10% of known near-Earth objects. This is in dramatic contrast to results from recent human space flight near-Earth object accessibility studies, where the most favorable known destinations are typically almost 50% Atens. Geocentric dynamics explain this enhanced Aten accessibility and lead to an understanding of where the most accessible near-Earth objects reside. Without a comprehensive space-based survey, however, highly accessible Atens will remain largely unknown.

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Aug 1, 2011 Columbia B Session 6: Trajectory Optimization I Chair: David Dunham, KinetX, Inc.

13:20 AAS 11 - 450 Hypersonic, Aerodynamically Controlled, Path Constrained Reentry Optimization Using Pseudospectral Methods Christopher L. Ranieri, The Aerospace Corporation; Anil V. Rao, University of Florida Hypersonic, aerodynamically controlled reentries are optimized with the GPOPS package. The reentries incorporate state and control path constraints and interior waypoint constraints to address heating and stability constraints and no-fly zones. GPOPS was used to determine the booster size needed to safely complete the desired mission objectives without being significantly oversized. GPOPS's newly developed mesh refinement scheme is used to adaptively adjust the mesh size and spacing to increase solution accuracy. The accuracy improvements afforded by the mesh refinement scheme are highlighted and the solution process is compared with past efforts on this problem using a different tool, SOCS.

13:40 AAS 11 - 451 A Design Method for Low Altitude, Near-Equatorial Lunar Orbits Laura Plice, Logyx LLC; Tim Craychee, Applied Defense Solutions In 2013 the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission will return to an orbital regime not visited since Apollo. The orbit required for LADEE poses unique challenges to the mission designer: low, retrograde, near circular, near equatorial, 100 days duration, with the line of apsides aligned near the solar terminator. The lunar mascons create havoc on the LADEE orbit, perturbing the eccentricity and line of apsides while the semi-major axis remains largely unchanged. LADEE uses a novel approach to allow the orbit designer to predict altitude decay and shifts in the periapsis for planning orbit maintenance maneuvers. 14:20 AAS 11 - 453 New Dynamic Model For Lunar Probe And Its Application To Quasi-periodic Orbit About The Translunar Libration Point Yingjing Qian, Inseok Hwang, and Jian Wei,Purdue University; Wuxing Jing, Harbin Institute of Technology; A new dynamic model with the standard ephemerides that describes the relative motion of a lunar probe is presented. Compared with other high-order models, the complexity of the proposed model is lower. More specifically, the proposed model considers the influences of direct and indirect sun's perturbation, and the eccentricity of moon's orbit. In the second part, Lunar L2 quasi-periodic orbit design is presented as an application of the proposed model. The initial conditions are calculated by using the Lindstedt-Poincare technique. An iteration method which introduces the sun's influence gradually and the differential correction are utilized to adjust the initial conditions. 14:40 AAS 11 - 454 Lunar-Resonant Trajectory Design For The Interstellar Boundary Explorer (IBEX) Extended Mission John Carrico Jr., Lisa Policastri, John Carrico III, Tim Craychee, Don Dichmann, John Ferreira, Marissa Intelisano, Ryan Lebois, Travis Schrift, and Ryan Sherman, Applied Defense Solutions, Inc.; Mike Loucks, Space Engineering Exploration This paper describes the trajectory design and analysis performed to ensure the success of the IBEX extended mission. In order to minimize the radiation dose, improve science collection, and avoid long eclipses, the authors designed a transfer to a new orbit with a period of about 9.1 days, which yields a 3:1 resonance with the Moon’s orbit. In June, 2011, the IBEX flight team commanded IBEX to perform three maneuvers which successfully transferred IBEX to this new Lunar-resonant orbit. This paper gives the details of the analysis, the trade-offs that were made, and the constraints that governed the operations. 15:00 Break

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15:30 AAS 11 - 455 Optimal Earth-Moon Transfer Trajectory Design Using Impulsive and Continuous Thrust Daero Lee, Tae Soo No , Ji Marn Lee and Gyeong-Eon Jeon, Chonbuk National University, Republic of Korea In this paper, results of Earth-Moon transfer trajectory studies are presented. Planar, circular, restricted three body formulation is adopted to represent the system dynamics, and use of mixed thrust, that is, impulsive thrust at Earth departure, continuous thrust during Earth-Moon transfer and Moon capture is assumed. This continuous and dynamic optimization problem is reformulated as a discrete optimization one by using the method of direct transcription and collocation, and then is solved using the nonlinear programming software. As a performance index, we choose to use the sum of initial Delta V required for the departure from the Earth (parking) orbit. 15:50 AAS 11 - 456 Parametric Study of Earth-to-Moon Transfers with Hybrid Propulsion System with Dedicated Launch Giorgio Mingotti, Universität Paderborn, Germany. This work concerns preliminary parametric design of Earth-to-Moon transfers, exploiting both chemical (high-thrust) and solar electric (low-thrust) propulsion. Starting from a GTO to a around the Moon, WSB trajectories with initial lunar swingby are evaluated in terms of propellant mass consumption and flight time. A dedicated launch strategy is investigated. This research has been conducted during an internship at the European Space Operations Centre, in the Mission Analysis Section, within the AstroNet framework. 16:10 AAS 11 - 457 Research of the Free-Return Trajectories Between the Earth-Moon Qinqin Luo, Jianfeng Yin and Chao Han, Beihang University A new design method for the free-return lunar flyby trajectories between the Earth and the Moon is developed in this paper. The pseudostate theory is adopted to get the initial result of the free-return trajectory. On the basis of the initial result, an imporved differential-correction method is employed to find the final solution in a more complicated dynamic model. The global features of the free-return lunar flyby trajectories are studied via the design method proposed in this paper, and some valuable results are obtained. 16:30 AAS 11 - 459 Targeting Low-Energy Transfers to Low Jeffrey S. Parker and Rodney L. Anderson, Jet Propulsion Laboratory, California Institute of Technology A targeting scheme is presented to build trajectories from a particular Earth to a particular low lunar orbit via a low-energy transfer and up to two maneuvers. The total transfer Delta-V is characterized as a function of the Earth parking orbit inclination and the departure date for transfers to each given low lunar orbit. The transfer Delta-V cost is characterized for transfers constructed to low lunar polar orbits with any longitude of ascending node, and for transfers that arrive at the Moon at any given time during a month. 16:50 AAS 11 - 470 Atmospheric Entry Guidance Via Multiple Sliding Surfaces Control For Mars Precision Landing Scott Selnick, Raytheon Missile Systems; Roberto Furfaro and Daniel R. Wibben, University of Arizona A Multiple Sliding Surface Guidance (MSSG) approach for Mars entry guidance has been developed for a class of low-lift landers. The guidance scheme is based on higher order sliding mode control theory adapted to account for the specific 2-sliding mode order exhibited by the longitudinal motion of the entry vehicle guided using bank angle variations and the ability of the system to reach the sliding surface in a finite time. Unlike more standard methods, the proposed scheme does not require any off-line trajectory generation. Preliminary results show that the proposed guidance is feasible.

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Aug 1, 2011 Columbia C Session 7: Formation Flying I Chair: Dr. Aaron Trask, Apogee Integration

13:40 AAS 11 - 462 An Operational Methodology for Large Scale Deployment of Nanosatellites into Low Earth Orbit Dr. Justin A. Atchison and Aaron Q. Rogers, The Johns Hopkins University Applied Physics Laboratory; Steven J. Buckley, Operationally Responsive Space Office The on-orbit deployment of large numbers of nanosatellites is cast in terms of the relative motion equations, augmented with differential drag. Using this framework, we develop a methodology for minimizing the likelihood of re-contact or interference among the deployed nanosatellites. This approach is evaluated on the Operationally Responsive Space Office's Launch Enabler Mission, which is planning to deliver 25 small payloads to orbit in the late 2012 timeframe. By strategically varying the deployment order, timing, and initial attitude, we demonstrate net separation among each of the nanosatellites for the first three weeks, as validated by high fidelity simulations.

14:00 AAS 11 - 463 Control Of Relative Motion Via State-Dependent Riccati Equation Technique Giuseppe Di Mauro, Pierluigi Di Lizia and Michèle Lavagna, Politecnico di Milano In this paper, development of a nonlinear controller based on State-Dependent Riccati Equation (SDRE) technique is investigated to solve relative motion control problem involving the docking phase between two Earth orbiting spacecraft. This method allows to generate a sub-optimal control law to regulate the tracking error in relative position and attitude. Therefore the relative coupled translational and attitude dynamics are modeled. Numerical simulations are performed to demonstrate the effectiveness of this control formulation. Two iterative methods (Kleinman algorithm and Power Series Formulation) are used to solve algebraic Riccati equation, and their effects on computational cost of control technique are analyzed. 14:20 AAS 11 - 464 Curvilinear Coordinates for Covariance and Relative Motion Operations David A Vallado and Salvatore Alfano, Center for Space Standards and Innovation Relative motion studies have traditionally focused on linearized equations, and inserting additional force models into existing formulations to achieve greater fidelity. The sim-plest approach is to numerically integrate the two satellite positions and then convert to the Hills frame as necessary. Recent works have introduced some approaches for this transformation, with some approximations. We develop an exact transformation between Cartesian and curvilinear frames and thoroughly test the results for various orbital classes. The transformation has applicability to covariance operations which we also investigate. Finally, we examine how the transformation affects depiction of the covariance matrix. 14:40 AAS 11 - 465 Effective Sphere Modeling For Electrostatic Forces On A Three-Dimensional Spacecraft Shape Lee Jasper and Hanspeter Schaub, University of Colorado, Boulder Satellite formations utilizing Coulomb forces have been studied recently due to their potential for their extremely low-fuel, low-power close formation flying control. While prior studies have assumed point mass/point charge models, this paper develops amethod to model complex geometries as finite spheres based upon finite element electrostatic field solutions for force interactions between a sphere and a non-spherical body. The effective sphere model is shown to accurately model and predict force behavior of complex geometries at separation distances beyond 3-4 craft radii. Further properties of this method are discussed and a brief formation control development is presented. 15:00 Break

15:30 AAS 11 - 466 Relative Motion Control for Two-Spacecraft Electrostatic Orbit Corrections Erik Hogan and Hanspeter Schaub, University of Colorado at Boulder The charged relative motion dynamics and control of a two-craft system is investigated if one vehicle is performing a low-thrust orbit correction using inertial thrusters. The nominal motion is an along- track configuration where active electrostatic charge control is maintaining an attractive force between the two vehicles. In this study the charging is held fixed, and the inertial thruster of the tugging vehicle is controlled to stabilize the relative motion to a nominal fixed separation distance. The resulting control law is shown to be asymptotically stabilizing. Simulations are performed to illustrate control system performance.

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15:50 AAS 11 - 467 Nonlinear Analytical Solution Of Relative Motion Subject To J2 Perturbation Using Volterra Kernels Ashraf Omran and Brett Newman, Old Dominion University This paper introduces Volterra theory to orbit mechanics. The paper presents a novel nonlinear analytical solution for the relative motion subject to J2 perturbation with a circular reference orbit. First, the nonlinear equations of the relative motion are expanded in a polynomial form using the Knocker operator. Carleman bilinearization is then used to compute Volterra kernels analytically in terms of the orbit parameters and the deputy initial conditions. The resultant solution based on these analytical Volterra kernels is compared to the linear solution showing a significant reduction in the error, when the nonlinear simulation is considered as the benchmark.

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Aug 1, 2011 Kahiltna Ct Session 8: Special Topic: Conjunction Assessment Chair: Ryan Frigm, a.i. solutions, Inc.

13:20 AAS 11 - 430 A Tuned Single Parameter For Representing Conjunction Risk D. Plakalovic, M.D. Hejduk, and R.C. Frigm, a.i. solutions, Inc.; L.K. Newman, NASA GSFC Satellite conjunction assessment risk analysis is a subjective enterprise that can benefit from quantitative aids, and to this end NASA/GSFC has developed a fuzzy logic construct - called the "F- value" - to attempt to provide a statement of conjunction risk that amalgamates multiple indices and yields a more stable intra-event assessment. This construct has now sustained an extended tuning procedure against heuristic analyst assessment of event risk. The tuning effort has resulted in modifications to the calculation procedure and the adjustment of tuning coefficients, producing a construct with both more predictive force and a better statement of its error.

13:40 AAS 11 - 431 Analysis of Collision Avoidance Maneuver for COMS-1 satellite Hae-Dong Kim, Young-Joo Song, Haeyeon Kim, Bang-Yeop Kim and Hak-Jung Kim, Korea Aerospace Research Institute; Eun-Hyuk Kim, University of Science and Technology The COMS-1 (Communication, Ocean and Meteorological Satellite 1) is a South Korean satellite which was launched into in June, 2010. Russia's RADUGA 1-7 satellite has come close to the COMS-1 satellite, where is staying at a longitude of 128.2 degrees East since last January 2011. In this paper, the preparations and results of collision avoidance maneuver for COMS- 1 satellite are presented. we introduce the NORAD TLE based ground orbit determination strategy and an effort to increase the position accuracy of RADUGA 1-7 based on the proposed strategy is also presented. 14:00 AAS 11 - 432 Assessment Of Uncertainty-Based Screening Volumes For Nasa Robotic Leo And Geo Conjunction Risk Assessment S.W. Narvet, R.C. Frigm, and M.D. Hejduk, a.i. solutions, Inc. Conjunction Assessment operations require screening assets against the space object catalog by placing a pre-determined spatial volume around each asset and predicting whether and when another object will violate that volume. Analysis of several years of data has shown that current volumes used at NASA / GSFC may result in under-screening for some spacecraft, especially those in low-altitude orbits. This analysis is intended to better characterize the combined primary-secondary uncertainties in LEO andGEO orbit regimes and thereby determine appropriate screening sizes for those regimes based on the risk tolerance that spacecraft Owner/Operators are willing to accept in their mission. 14:20 AAS 11 - 433 Collision Avoidane in Near Real Time Joshua Wysack, SpaceNav Operational collision threat characterization is a fundamental component of routine satellite operations. The threat characterization process starts with the generation of close approach predictions and ends with an action/no-action decision from mission stakeholders. As the size of the space object catalog increases, satellite operators will be faced with more conjunction events to evaluate. Thus more sophisticated collision threat characterization and collision avoidance strategies must be implemented. This paper presents an avoidance maneuver planning strategy that simultaneously accounts for, and mitigates numerous conjunction events. The approach employed in our solution is to directly target an n-order reduction in the probability value. 14:40 AAS 11 - 434 Requirements and Guidance for Conjunction Assessment David Finkleman, Analytical Graphics, Inc.; David Berry, Jet Propulsion Laboratory This paper will review development of the content, format, implementation, and opera- tional use of timely information for mitigating the consequences of conjunctions among satellites and trace the elements of information to requirements for dealing with threat- ening events. Stakeholders are developing essential elements of data, transmission for- mats, and operational guidance for managing close approaches (conjunctions) among satellites, preventing collisions, and mitigating the consequences of orbitalevents. The satellite operations community is also developing guiding principles for dealing with potential collisions in space. 15:00 Break

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15:30 AAS 11 - 435 Probability of Collision with Special Perturbations Dynamics Using the Monte Carlo Method Chris Sabol, Air Force Research Laboratory; Christopher Binz, Alan Segerman, Naval Research Laboratory; Kevin Roe, Maui High Performance Computing Center; Paul W. Schumacher, Jr., Air Force Research Laboratory Special perturbations-based Monte Carlo methods were used for estimating the probability of collision between two satellites. Sample populations for each satellite are produced via the covariance at , then the closest point of approach between each pair of samples is determined. Comparisons are made against an analytical method and a two-body Monte Carlo method for LEO and GEO orbit cases. Additionally, the impact of covariance realism is considered through the introduction of a scale factor to the covariance matrix A high performance computing framework called Collision and Conjunction Analysis (CoCoA), using shared or distributed memory, was utilized to generate results. 15:50 AAS 11 - 436 Intelsat Experience on Satellite Conjunctions and Lessons Learned Joseph Chan, Intelsat This paper will present Intelsat's experience on satellite conjunctions for the past years. We will present our experiences with SDA (Space Data Association) and JSpOC (Join Space Operation Center) and our end-to-end process to validate close approaches and if necessary to plan maneuvers to increase miss distances. We will also discuss issues we have encountered and ideas for moving forward. We will be addressing different ideas including data sharing, data fusion, conjunction detection algorithm, miss distance monitoring and … We will present the different studies and analyses that we have conducted to improve satellite conjunction monitoring and mitigations. 16:10 AAS 11 - 437 Sequential Probability Ratio Test for Collision Avoidance Maneuver Decisions Based on a Bank of Norm-Inequality-Constrained Epoch State Filters J. R. Carpenter and F. L. Markley, NASA GSFC; K.T. Alfriend, Texas A&M University Sequential probability ratio tests explicitly allow decision makers to incorporate false alarm and missed detection risks, and are potentially less sensitive to modeling errors than a procedure that relies solely on a probability of collision threshold. Recent work on constrained Kalman filtering has suggested an approach to formulating an SPRT for CAM decisions: a filter bank with two norm- inequality-constrained epoch-state EKF's. One filter models the null hypothesis that the miss distance is inside the combined hard body radius (HBR) at the predicted time of closest approach, and one filter models the alternative hypothesis. 16:30 AAS 11 - 438 Toroidal Path Filter Salvatore Alfano, Center for Space Standards and Innovation For satellite conjunction analysis containing many objects, timely processing can be a concern. Various filters are used to identify orbiting pairs that cannot possibly come close enough over a prescribed time period to be considered hazardous. One such filter is the orbit path filter (also known as the geometric pre-filter), designed to eliminate pairs of objects based on characteristics of orbital motion. Rather than using a single distance bound, this work presents a toroidal approach, providing versatility by allowing the user to specify different in-plane and out-of-plane bounds for the path filter. 16:50 AAS 11 - 439 Verifying Observational for Real-world Space Situational Awareness David A. Vallado, Center for Space Standards and Innovation In practice, Space Situational Awareness requires precise knowledge of all objects in orbit. A complete, robust and accurate SSA system in necessary for accurate conjunction analysis (CA) and Radio Frequency Interference (RFI) de-termination. The Space Data Association fuses data from multiple sources to support state-of-the-art CA and RFI operations. Implementation requires signifi- cant work including a detailed verification effort to monitor and ensure interop-erability and capability. This paper summarizes the various data assembly, conversion, and OD operations to support this effort. The attention to detail required at each step is shown, including the effect that time and coordinate systems.

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Aug 2, 2011 Columbia A Session 9: Non-Earth Orbiting Missions Chair: Dennis Byrnes, Jet Propulsion Lab

08:00 AAS 11 - 479 A 3D Shape-Based Approximation Method for Low-Thrust Trajectory Design Bradley Wall, Embry-Riddle Aeronautical University, Prescott, AZ; Daniel Novak, University of Glasgow Mission design using low-thrust propulsion requires a method for approximating the spacecraft's trajectory and its cost. The approximating method can be for the purpose of evaluating a large search space or for providing a suitable initial guess to be used with more-accurate trajectory optimizers. A shape-based method is derived here that is capable of determining such trajectories in three dimensions. Additionally, a throttle parameter is introduced such that the thrust acceleration equation of motion is satisfied. The algorithm is tested on an Earth-Mars rendezvous mission.

08:20 AAS 11 - 480 Comparisons Between Newton-Raphson and Broyden's Methods for Trajectory Design Problems Matthew Berry, Analytical Graphics, inc. Broyden's method, a generalized-secant method for root-finding, was recently added as an option in the STK/Astrogator maneuver planning and trajectory design software module. The software previously used a Newton-Raphson approach with numerical partials to solve shooting problems. In this paper the two methods are compared for a wide variety of problems, including station-keeping, orbit transfers, and interplanetary trajectories. For most use-cases Broyden's method has a faster performance than Newton-Raphson. 08:40 AAS 11 - 481 End-to-end trajectory design for a chemical mission including multiple fly-by's of Jovian Trojan asteroids Angéla Mithra, Atos Origin; Elisabet Canalias and Denis Carbonne, Centre National d'Etudes Spatiales. Missions to Jupiter's L4 Trojan asteroids have been recently proposed by several space agencies. A methodology for the end-to-end trajectory design of a chemical mission with a Soyuz launch and including as many fly-by's of Trojan asteroids as possible has been developed at CNES. Different options have been considered for the interplanetary cruise. Moreover, a branch-and-prune algorithm has been implemented for determining the fly-by sequences inside the cloud. Our results include a large amount of sequences of three and four asteroids, as well as some with five fly-by's, which is a considerable achievement for a middle-size mission using classical propulsion. 09:00 AAS 11 - 486 Navigation of the EPOXI Spacecraft to Comet Hartley 2 S. Bhaskaran, M. Abrahamson, S. Chesley, M. Chung, R. Haw, C. Helfrich, D. Jefferson, B. Kennedy, T. McElrath , W. Owen, B. Rush, J. Smith, C. Yen, Jet Propulsion Laboratory On November 4, 2010, the EPOXI spacecraft flew by the comet Hartley 2, marking the fourth time that a NASA spacecraft successfully captured high resolution cometary nucleus. This is the extended- mission of the Deep Impact mission, which delivered an impactor on comet Tempel-1 on July 4, 2005. This paper presents an overview of the design of the trajectory which accomplished the science objectives, the challenges of determining the spacecraft and comet orbit, and the maneuver strategy to achieve the desired targeting conditions. 09:20 AAS 11 - 482 EPOXI Trajectory and Maneuver Analyses M. J. Chung, S. Bhaskaran, S. R. Chesley, C. A. Halsell, C. E. Helfrich, D. C. Jefferson, T. P. McElrath, B. P. Rush, T. M. Wang, and C. L. Yen, Jet Propulsion Laboratory. The EPOXI mission is a NASA Discovery Mission of Opportunity combining two separate investigations: Extrasolar Planet Observation and Characterization (EPOCh) and Deep Impact eXtended Investigation (DIXI). Both investigations reused the DI instruments and spacecraft that successfully flew by the comet Tempel-1 (July 2005). For EPOCh, the goal was to find exoplanets with the high resolution imager, while for DIXI it was to fly by the comet Hartley-2 (November 2010). This paper focuses primarily on the navigation experience of the earlier maneuver analyses critical for the EPOXI mission including delta-v contour mapping, avoiding the vectorization of maneuvers, and statistical delta-v analysis. 09:40 Break

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10:10 AAS 11 - 483 Ground Optical Navigation for the Stardust-NExT Mission to Comet 9P Tempel 1. S. D. Gillam, J. Ed. Riedel, W. M. Owen Jr., T. M. Wang, R. A. Werner, S. Bhaskaran, S. R. Chesley, P. F. Thompson, and A. A. Wolf, Jet Propulsion Laboratory Ground-based optical navigation (OpNav) using pictures taken by the Stardust spacecraft contributed to targeting maneuvers during its approach to comet Tempel 1. Hardware problems, limited downlink bandwidth, and changes in the flight profile affected the OpNav picture schedule; sometimes in near- real time. The Stardust navigation camera and attitude control presented challenges, and picture- processing techniques were developed during approach to deal with them. 10:30 AAS 11 - 484 Hayabusa: Navigation Challenges during Earth Return R. J. Haw, S. Bhaskaran, E. Graat, W. Strauss, P. Williams, S. Ardalan, C. Ballard, P. Menon, E. Sklylanskiy, J. Smith, Jet Propulsion Laboratory; J. Kawaguchi, M. Yoshikawa, JAXA; T. Ohnishi, Fujitsu Corp. The Hayabusa asteroid sample-return mission returned to Earth in June 2010. Spacecraft navigation during the return voyage was a collaboration between personnel from both JAXA and NASA-JPL. The navigation challenges encountered on this return journey were overcome by combining the talents from both agencies. 10:50 AAS 11 - 485 Long Term Missions at the Sun-Earth Libration Point L1: ACE, SOHO, and WIND Craig E. Roberts, a. i. solutions, Inc. Three heliophysics missionsthe Advanced Composition Explorer (ACE), Solar Heliospheric Observatory (SOHO), and the Global Geoscience WIND have been orbiting the Sun-Earth interior libration point L1 continuously since 1997, 1996, and 2004, respectively. ACE and WIND (both NASA missions) and SOHO (an ESA-NASA joint mission) are all operated from the Goddard Space Flight Center. While ACE and SOHO have been dedicated libration point orbiters since launch, WIND prior to 2004 flew a remarkable 10-year deep-space trajectory including 36 lunar flybys. The L1 orbits and mission history of ACE, WIND, and SOHO are reviewed, and the stationkeeping maneuver techniques and experience are presented. 11:10 AAS 11 - 487 Particle levitation, trajectories, and mass transfer in the quasi-statically charged, planar circular restricted four body problem Jared M. Maruskin, Lara Mitchell, Macken Wong, David Richardson, Douglas Mathews, Jennifer Murguia, Tri Nguyen, Raquel Ortiz, Usha Watson, and Gina Ma, San Jose State University; Julie Bellerose, Carnegie Mellon University We discuss levitation conditions, orbits, and mass transfer of charged particles in a binary asteroid system, in which the asteroids are electrically charged due to solar radiation pressures. The surface potential of the asteroids possesses a positive potential on the sunlit half and negative potential on the shadow half. We derive the nonautonomous equations of motion for charged particles and an analytic representation for their levitation conditions. Particle trajectories and temporary relative equilibria are examined in relation to their osculating forbidden regions. Finally, we use a Monte Carlo simulation to quantify expected mass transfer and loss rates between the asteroids. 11:30 AAS 11 - 488 Sun-Earth Based Spin Axis Determination for Interplanetary Missions and Its Application to IKAROS Yuichi Tsuda, Takanao Saiki, Yuya Mimasu, Ryu Funase, Japan Aerospace Exploration Agency This paper describes an attitude determination strategy for spinner spacecraft based on sun and Earth angles. This method realizes a complete spin vector determination using only one sun sensor. Thus this method is suitable for low cost, resource-limited spacecraft with a moderate attitude determination accuracy requirement. The method has been developed for and is actually used in IKAROS, which is a Japanese interplanetary solar sail demonstration mission. This paper introduces theoretical backgrounds ofSun-Earth based attitude determination and shows how the actual implementation was done for IKAROS mission. Then the attitude determination performance achieved during the actual operation is evaluated.

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Aug 2, 2011 Columbia B Session 10: Formation Flying II Chair: Bo Naasz, NASA GSFC

08:00 AAS 11 - 489 Carrier Phase Differential GPS for LEO Formation Flying – The PRISMA and TanDEM-X Flight Experience Montenbruck O., D’Amico S., Ardaens J.-S., and Wermuth M., DLR/GSOC The paper describes the techniques for GPS based real-time and/or offline navigation employed at DLR/GSOC for the PRISMA and TanDEM-X formation flying missions. Flight results from the first year of operation are presented and the methodologies for assessing the achieved accuracies are described. Specific aspects of each mission (antennas, receivers, maneuvers, etc.) and their impact on the relative navigation are discussed to provide guidelines for the design of relative navigation systems in future formation flying missions.

08:20 AAS 11 - 490 Fixed-Duration, Free Departure Time Satellite Formation Transfer Problem Weijun Huang, University of Missouri Satellite transfer between two satellite formations has its own features compared to satellite transfer between two earth-centered orbits. Based on these features, this paper formulates the transfer between two satellite formations as a fixed-duration, free departure time satellite transfer problem. General necessary conditions and transversality conditions of an extremal are given for this new type of problem. Simplified statements of this new problem are provided for three types of satellite engines. Moreover, analytic solutions at two specific cases are derived and used to support the theory of this paper 08:40 AAS 11 - 491 Formation Flying Along a with Control Constraints Mai Bando, Kyoto University; Akira Ichikawa, Nanzan University The magnitude of the control input is also an important factor in impulse control and pulse control. In this paper, formation flying along a circular orbit with L1-performance and L-infty-constraint is considered. The design of feedback controllers is based on the linear quadratic regulator theory using the property of null controllabilty with vanishing energy of the Hill-Clohessy-Wiltshire equations, and the dependency of the feedback gain on the weight parameter on the control input is examined analytically, and suboptimal controllers in the sense of L1-norm which satisfy the magnitude constraint are designed. 09:00 AAS 11 - 492 Metrics for Mission Planning of Formation Flight Shawn E. Allgeier and Norman G. Fitz-Coy, University of Florida; R. Scott Erwin and T. Alan Lovell, Air Force Research Laboratory This paper considers the analysis of relative motion between two spacecraft in orbit. Specifically, the paper seeks to provide bounds for relative spacecraft position- and velocity- based measures which impact spacecraft formation flight mission design and analysis. Two metrics for formation flight are presented, the cross track (out of plane) separation and relative speed. A methodology for bounding the two metrics is presented. The extremal equations for the relative speed metric are formulated as an affine variety and solved using a Gr¨obner basis reduction. A numerical example is included to demonstrate the efficacy of the method. 09:20 AAS 11 - 493 Natural Regions Near The Sun-Earth Libration Points Suitable For Space Observations With Large Formations Aurelie Heritier and Kathleen C. Howell, Purdue University This investigation explores regions near libration points that might prove suitable for space observation with large formations. Recent analyses have considered occulters located at relatively large distances from the telescope near the L2 Sun-Earth libration point for detection of exoplanets. During the science mode, the telescope-occulter distance, as well as the pointing direction toward the star, are typically fixed. Quasi-periodic Lissajous trajectories are employed as a tool to determine regions near the telescope orbit where the large formation can be easily maintained. By placing the occulter in these locations, the control required to maintain the line of sight is reduced. 09:40 Break

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10:10 AAS 11 - 495 Osculating Relative Orbit Elements Describing Relative Satellite Motion About an Eccentric Orbit Joshuah A. Hess, NASIC/SMSM; Douglas D. Decker, NASIC/SMD; Thomas Alan Lovell, AFRL/RVES Relative orbit elements (ROEs) based on a circular chief satellite orbit are erroneous when applied to a perturbed, non-circular reference orbit. In those situations, the ROEs will encounter geometric instability and drift. To counter this, a set of time-variant ROEs have been derived to describe the relative orbit for the unperturbed, elliptical chief using analytical state substitution. The result is a geometric parameterization that allows an instantaneous visualization of the relative trajectory. 10:30 AAS 11 - 496 Osculating Relative Orbit Elements Describing Relative Satellite Motion with J2 Perturbations Joshuah A. Hess, NASIC/SMSM; Douglas D. Decker, NASIC/SMD; Thomas Alan Lovell, AFRL/RVES Relative orbit elements (ROEs) based on a circular chief satellite orbit are erroneous when applied to a perturbed, non-circular reference orbit. In those situations, the ROEs will encounter geometric instability and drift. To counter this, a set of time-variant ROEs have been derived to describe the relative orbit for the J2 perturbed, circular chief using analytical state substitution. The result is a geometric parameterization that allows an instantaneous visualization of the relative trajectory. 10:50 AAS 11 - 497 Satellite Relative Motion in Elliptical Orbit Using Relative Orbit Elements Chao Han and Jianfeng Yin, Beihang University In this paper, using the spherical geometry, the relative orbit elements are strictly defined through the employment of a projection rule. The exact transformation equations between relative orbit elements and absolute orbit elements are deduced. A new relative motion model with no singularity based on relative orbit elements is derived, which is suitable for both elliptical and near-circular cases. The characteristics of elliptical relative motion are analyzed. The proposed method and conclusions are validated through numerical examples. The basic theory of relative orbit elements is improved and a unified model of both elliptical and near-circular relative motion is developed. 11:10 AAS 11 - 498 Circular Orbit Radius Control Using Electrostatic Actuation For 2-Craft Configurations Hanspeter Schaub and Lee E. Z. Jasper; University of Colorado Electrostatic static actuation of free-flying spacecraft is being considered to directly control the relative motion. This paper investigates the effectiveness of using active electrostatic charging to perform orbit altitude adjustments of a nominally circular orbit. Coulomb forces are employed to gently pull a second charged object in the along track direction. The pulling configuration is shown to provide larger electrostatic forces over a pushing configuration due to the coupled capacitance modeling. Variational equations are developed to estimate the semi-major axis changes. Kilo-Volt levels of potential are sufficient to achieve kilometer level radius changes per orbit for geosynchronous orbit regimes.

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Aug 2, 2011 Columbia C Session 11: Orbit Estimation I Chair: Dr. Michael Gabor, Northrop Grumman

08:00 AAS 11 - 499 Advanced Navigation Strategies for an Asteroid Sample Return Mission J. Bauman, B. Williams, and K. Williams, KinetX Inc.; K. Getzandanner, NASA Goddard Space Flight Center Flyby and rendezvous missions to asteroids have been accomplished using navigation techniques derived from experience gained in planetary exploration. The proper balance between ground-based navigation and on board autonomous navigation is determined in this analysis by studying the evolution of the uncertainty in the relevant dynamic parameters. These parameters include the spacecraft position and velocity relative to the asteroid and the asteroid spin state and gravity. This paper presents analysis ofadvanced navigation strategies required for an example mission to acquire a sample from the asteroid 4660 Nereus and return it to Earth.

08:40 AAS 11 - 501 Fast, Efficient and Adaptive Interpolation of the Geopotential Nitin Arora and Ryan P. Russell , Georgia Institute of Technology Conventional high-fidelity geopotential computations rely on expensive spherical harmonics (SH) series. Here, we propose an interpolation scheme that classically improves compute speed at the expense of memory. The approach is exact as the accelerations are calculated naturally as the gradient of the fitted potential, and continuity and smoothness are ensured across local cells using the Junkins weight functions, while the interpolating functions are chosen with a new adaptive method that minimizes coefficient storage subject to a maximum error threshold. For example, a model fitting the 200x200 field requires 1.3 Gigabytes, and achieves ~300x speedups over a Pines SH implementation. 09:00 AAS 11 - 502 Gravity Error Compensation Using Second-Order Gauss-Markov Processes Jason M. Leonard, Felipe G. Nievinski and George H. Born, University of Colorado at Boulder Earth science satellite missions currently require orbit determination solutions with position accuracies to within a few centimeters. The estimation of empirical accelerations has become commonplace in precise orbit determination (POD) for Earth-orbiting satellites. Dynamic model compensation (DMC), utilizes an exponentially time-correlated system noise process, known as a first-order Gauss-Markov process (GMP1) to estimate un-modeled accelerations. In this work, we address the use of a second- order Gauss-Markov process to compensate for higher order spherical harmonic gravity accelerations, beyond J3. Improvements in POD and orbit prediction through the implementation of an optimal GMP2 for empirical acceleration estimation will be demonstrated. 09:20 AAS 11 - 503 Navigation Analysis for an L5 Mission in The Sun-Earth System Pedro J. Llanos de la Concha and Gerald R. Hintz, University of Southern California; James K. Miller, Navigation Consultant In a previous paper, we characterized a typical mission in a planar orbit around L5 to observe the Sun. We indicated that such a mission is feasible. We provide a maneuver and orbit determination analysis for a L5 mission. This study will be performed for both the transfer trajectory and the Trojan orbit around L5. Orbit determination will be needed to have a more accurate estimation of the trajectory of the spacecraft at different stages: launch, mid-course and arrival. We will analyze the required propulsion maneuvers needed to compensate primarily for injection errors at launch and station-keeping maneuvers around L5. 09:40 Break

10:30 AAS 11 - 506 Orbit Determination results of Akatsuki (Planet-C) Mission -Venus Climate Orbiter Tsutomu Ichikawa, Nobuaki Ishii, Hiroshi Takeuchi, Makoto Yoshikawa, Takaji Kato1,JAXA; Chiaki Aoshima, Tomoko Yagami,Yousuke Yamamoto ,and Nobuhiro Miyahara; Fujitsu Limited Venus Climate Orbiter, "Akatsuki", has been launched on May 21, 2010 on H-IIA booster from Japanese launch side. And arrived at Venus in December 6, 2010 without trouble after the cruising interplanetary approximately seven months. The operation sequence specifies four phases for different parts of the mission, (1) Launch, separation and initial health check, (2) Cruise trajectory to Venus after midcourse navigation and final course adjustment, (3)VOI by burning on OME, (4) Nominal Venus Observation by mission instruments. In this paper, the orbit determination result, the estimation methods, and experiences during the period from the launch through the VOI phase.

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10:50 AAS 11 - 507 Re-Examination of Pioneer 10 Tracking Data Including Spacecraft Thermal Modeling Modenini, Dario and Tortora, Paolo, University of Bologna The Pioneer anomaly refers to a drift in the radio-metric tracking Doppler signals received by Pioneer 10 and 11 spacecrafts which can be ascribed to a constant sunward acceleration, as firstly reported by Anderson and al in 1998. As a result of an independent analysis performed by the authors, the manuscript will focus on two aspects: the detailed thermal modelling of the spacecrafts and the re- examination in light of this model of the available tracking data using Jet Propulsion Laboratory's Orbit Determination Program (ODP). Our preliminary results show a significant decrease of the unexplained residual acceleration. 11:10 AAS 11 - 508 Validation of COMS Satellite Orbit Determination Based on Single Station Antenna Tracking Data Yoola Hwang and Byoung-Sun Lee, ETRI; Hae-Yeon Kim and Bang-Yeop Kim, KARI; Haedong Kim, Sejong University COMS-1 has been successfully operated by Satellite Ground Control System (SGCS) since the launch of Jun 28, 2010. Since COMS satellite is located near ground control center, there is a singularity of geometry observability in azimuth direction. This paperpresents a study of azimuth bias estimation for measurement correction using external station and covariance analysis. The accuracy of geostationary Earth orbiter (GEO) orbit determination (OD) for COMS satellite is validated using optical scanning pucture pucture. Also, the accuracy of COMS OD using single station tracking data satisfies within 4-5 km RSS given by specifications when compared with two-way ranging OD.

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Aug 2, 2011 Kahiltna Ct Session 12: Special Topic: ARTEMIS Mission Chair: Mr. David Folta, NASA GSFC

08:00 AAS 11 - 510 ARTEMIS Mission Overview: From Concept to Operations David Folta, NASA/Goddard Space flight Center; Theodore Sweetser, Jet Propulsion Laboratory ARTEMIS (Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun) repurposed two spacecraft to extend their useful science (Angelopoulos, 2010) by moving them via lunar gravity assists from elliptical Earth orbitsto L1 and L2 lunar libration orbits and then to lunar orbits by exploiting the Earth-Moon-Sun dynamical environment. This paper describes the complete design from conceptual plans using weak stability transfer options and lunar to the implementation and operational support of the Earth-Moon libration and lunar orbits. The two spacecraft of the ARTEMIS mission will have just entered lunar orbit at this paper's presentation.

08:20 AAS 11 - 511 Design and Implementation of the ARTEMIS Lunar Transfer Using Multi-body Dynamics David Folta and Mark Woodard, NASA / Goddard Space Flight Center; Theodore Sweetser and Steve Broschart, Jet Propulsion Laboratory; Daniel Cosgrove, University of California at Berkeley The use of multi-body dynamics to design the transfer of spacecraft from Earth elliptical orbits to the Earth-Moon libration (L1 and L2) orbits has been successfully demonstrated by the Acceleration Reconnection and Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) mission. Operational support of the two ARTEMIS spacecraft is a final step in the realization of a design process that can be used to transfer spacecraft with restrictive operational constraints and fuel limitations. The focus of this paper is to describe in detail the processes and implementation of this successful approach. 08:40 AAS 11 - 515 Station-keeping of the First Earth-Moon Libration Orbiters: the ARTEMIS Mission David Folta and Mark Woodard, NASA / Goddard Space Flight Center; Daniel Cosgrove

University of California at Berkeley Libration point orbits near collinear locations are inherently unstable and must be controlled. For Acceleration Reconnection and Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) Earth-moon operations, stationkeeping is challenging because of short time scales, large of the secondary, and solar gravitational and radiation pressure perturbations. ARTEMIS is the first NASA mission continuously controlled at both Earth- moon L1 and L2 locations and uses a balance of optimization, spacecraft implementation and constraints, and multi-body dynamics. Stationkeeping results are compared to pre-mission research including mode directions. 09:00 AAS 11 - 509 ARTEMIS Lunar Orbit Insertion and Science Orbit Design through 2013 Stephen B. Broschart, Theodore H. Sweetser and Vassilis Angelopoulos, Jet Propulsion Laboratory; David Folta and Mark Woodard, Goddard Space Flight Center The ARTEMIS mission plans to transfer two spacecraft from lunar Lissajous orbits around L1 into highly-eccentric lunar science orbits beginning in late-June of 2011. The nominal plan for the transfer from Lissajous, lunar orbit insertion maneuvers, and science orbits through 2013 is presented. The design accommodates large perturbations from Earth's gravity and restrictive constraints from spacecraft capabilities to enable opportunities for a range of Heliophysics and planetary science measurements. Since ARTEMIS plans the most eccentric lunar science orbit to date, the dynamics- driven approach used for ARTEMIS may inform the design of future planetary moon missions.

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09:20 AAS 11 - 514 Orbit Determination of Spacecraft in Earth-Moon L1 and L2 Libration Point Orbits Mark Woodard and David Folta, NASA GSFC; Daniel Cosgrove, Jeff Marchese and Brandon Owens, UCB/SSL; Patrick Morinelli, HTSI The ARTEMIS mission is the first to fly spacecraft in the Earth-Moon Lissajous regions. The two ARTEMIS spacecraft spent nearly a year in Lissajous orbits about Earth-Moon L1 & L2. To perform weekly stationkeeping maneuvers, orbit determination solutions were required with accuracies of 0.1 km in position and 0.1 cm/s in velocity. We will present results from flight data showing the DSN and GN tracking data requirements to meet those accuracies. We will confirm the results with covariance analysis. We will compare batch-least-squares and orbit determination techniques. We will present the force model error contributions. 09:40 Break

10:10 AAS 11 - 516 Strategy for Long-Term Libration Point Orbit Stationkeeping in the Earth-Moon System Thomas A. Pavlak and Kathleen C. Howell, Purdue University Given the continuing success of the first Earth-Moon libration point mission, ARTEMIS, it is likely that the Earth-Moon libration points will continue to be employed as platforms for space communications and scientific observations in the future. This work discusses a long-term stationkeeping strategy for Earth-Moon libration point orbits that does not require strict adherence to a baseline trajectory but retains the capability to meet a specific set of end-of-mission objectives at a planned lunar orbit insertion. The method is sufficiently general and is applied to various trajectories in both the circular restricted three-body and higher-fidelity ephemeris models. 10:30 AAS 11 - 513 Evaluating Orbit Determination Post-Processing Methods for Operational Artemis Data Bradley W. Cheetham and George H. Born, University of Colorado at Boulder; David Folta and Mark Woodard, NASA Goddard Space Flight Center The unique operational experience and data from the Artemis mission's time maintaining Libration Point Orbits (LPOs) in the Earth-Moon system holds significant potential to enable future exploration and utilization of this orbital regime. It provides an opportunity to evaluate operational constraints using real data which was previously not available. As a precursor to post-processing these orbit solutions for higher accuracy and to recover un-modeled accelerations, this paper will document preliminary work using simulated data to evaluate various methods of processing the raw mission data with known errors in the measurement and dynamics models.

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Aug 2, 2011 Columbia A Session 13: Planetary Mission Studies Chair: Brent Buffington, Jet Propulsion Laboratory / California Institute of Technology

13:20 AAS 11 - 517 Modeling and On-orbit Performance Evaluation of Propellant-free Attitude Control System for Spinning Solar Sail via Optical Parameter Switching Ryu Funase, Yuya Mimasu, Yoji Shirasawa, Yuichi Tsuda, Takanao Saiki and Junichiro Kawaguchi, Japan Aerospace Exploration Agency; Yoshikazu Chishiki, The University of Tokyo A fuel-free attitude control system for a spinning solar sail which utilizes solar radiation pressure was developed. This system consists of thin-film devices attached to the sail that electrically control their optical parameters such as reflectivity, and the attitude control torque is generated by switching their optical parameters synchronizing with spin motion. Attitude control torque model for a sail of arbitrary shape and deformation was derived. The control system was implemented for Japanese interplanetary solar sail demonstration spacecraft IKAROS and the on-orbit attitude control performance was rigorously evaluated.

13:40 AAS 11 - 518 Evaluating Periodic Orbits for the JEO Mission at Europa in Terms of Estimation Metrics Dylan Boone and Daniel J. Scheeres, University of Colorado at Boulder This work examines the relationship between orbit lifetime and stability and science measurement performance for the Jupiter Europa Orbiter. High-inclination orbits at planetary satellites decay rapidly. Periodic orbits are desirable for their potential to extend orbit lifetime and provide crossover measurements for improving altimetry. Candidate orbits are found and differentially corrected in the Restricted Three Body Problem. These orbits are evaluated using a covariance analysis in termsof the uncertainty in the tidal Love numbers and the lifetime of the orbit. 14:00 AAS 11 - 519 Mars Sample Return - Launch and Detection Strategies for Orbital Rendezvous Ryan C. Woolley, Richard L. Mattingly, Joseph E. Riedel, and Erick J. Sturm, Jet Propulsion Laboratory This study sets forth conceptual mission design strategies for the ascent and rendezvous phase of the proposed NASA/ESA joint Mars Sample Return Campaign. The current notional mission architecture calls for the launch of an acquisition/caching rover in 2018, an Earth return orbiter in 2022, and a fetch rover with ascent vehicle in 2024. Strategies are presented to launch the sample into a coplanar orbit with the Orbiter which facilitate robust optical detection, orbit determination, and rendezvous. Repeating ground track orbits exist at 457 and 572 km which provide multiple launch opportunities with similar geometries for detection and rendezvous. 14:20 AAS 11 - 520 Mid-Course Plane-Change Trajectories Expanding Launch Windows for Mars Missions Including Venus Flyby Opportunities Takuto Ishimatsu, Olivier de Weck and Jeffrey Hoffman, Massachusetts Institute of Technology We can expect to see an increasing number of robotic explorations of Mars over the next several decades, eventually followed by human missions. The ability to design and analyze Mars transfer trajectories is an important planning tool. Looking at the delta-V porkchop pattern of each launch window, it can be seen that there are two "craters" of local minima and a steep "mountain wall" between them. However, a mid-course plane-change trajectory gives additional opportunities. Although mid-course plane-change trajectories do not have an advantage in terms delta-V, expanding launch windows could be advantageous from the space logistics perspective. 14:40 AAS 11 - 521 Navigation Support at JPL for the JAXA Akatsuki (Planet-C) Venus Orbiter Mission Mark Ryne, Neil Mottinger, Stephen Broschart, Tung-Han You, Earl Higa, Cilfford Helfrich, Jet Propulsion Laboratory This paper details the orbit determination activities undertaken at JPL in support of the Akatsuki (a.k.a. Planet-C) mission. The JPL navigation team's role was to provide independent navigation support as a point of comparison with the JAXA generated orbit determination solutions. Topics covered will include a mission and spacecraft overview, small forces modeling, cruise and approach orbit determination results, and the international teaming arrangement. Significant time will also be dedicated to discussion of the events surrounding the unsuccessful Venus orbit insertion maneuver. 15:00 Break

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15:30 AAS 11 - 522 Passive Aerogravity Assisted Trajectories for Mars Atmospheric Sample Return Missions Evgeniy Sklyanskiy, Jet Propulsion Laboratory; Neil Cheatwood, Alicia Dwyer Cianciolo, Angela Bowes, NASA Langley Research Center A number of studies have demonstrated that during the planetary low altitude atmospheric flyby a produced lift can increase the Vinf bending and the total delta-V achievable during gravity assist maneuver. This type of Aero-Gravity Assist (AGA) trajectory requires a significantly high spacecraft lift-to-drag (L/D) ratio and a fairly robust close-loop guidance algorithm capable of providing a desired control authority for leveled, nearly constant altitude atmospheric flight. The AGA concept has been described in some previous publications as one of the techniques for Mars and Venus atmospheric sample return mission design strategies1. Most recent analysis has proven that passive, ballistic 15:50 AAS 11 - 523 Plans and Progress for Updating the Models used for Orbiter Lifetime Analysis Mark A. Vincent, Raytheon Intelligence and Information Systems; Todd A. Ely and Theodore H. Sweetser, Jet Propulsion Laboratory Three research areas related to Mars Planetary Protection will be discussed. The first one involves updates to the currently used simplified Mars atmosphere model using new tracking data and analysis. Second, new modeling for propagating Mean element has been proposed to account for multiple resonances such as the one seen while analyzing the behavior of the Mars Odyssey spacecraft. The third area involves automating the "Trinomial Method" which is a highly efficient probabilistic method that has been used on the MGS and Odyssey. 16:10 AAS 11 - 524 Selection of Mercury's surface features coordinates for the BepiColombo Rotation Experiment Alessandra Palli and Paolo Tortora, University of Bologna The knowledge of Mercury's rotational state is critical for constraining the planet's interior and is one of the key goals of the Mercury Orbiter Radioscience Experiment hosted on-board the BepiColombo's Mercury Planetary Orbiter. The experiment is accomplished by the combined operation of different payloads, for precise orbit reconstruction and observation of surface landmarks at different epochs, to derive Mercury's obliquity and librations. As the definition of an optimal observation strategy is crucial for mission planning, implementation of pattern matching algorithms and estimation procedures, a software simulator was implemented and several simulations performed to identify optimal selection criteria. 16:30 AAS 11 - 526 Stationkeeping stragegy for Laplace-JGO science phase around Ganymede Mirjam Boere and Arnaud Boutonnet, ESA-ESOC The ESA Jupiter Ganymede Orbiter mission envisages a spacecraft in low altitude polar orbit around Ganymede. Due to the combined effect of Ganymede's gravity potential and Jupiter's attraction, an initially circular orbit rapidly becomes eccentric. A method analytically combining the effect of Jupiter's attraction and all zonal terms of the gravity potential is presented in this paper. It allows finding an unstable equilibrium point around which stationkeeping is performed. Numerical integration, including the full gravity potential, validates the approach. Frequency of manoeuvres and DeltaV cost are assessed in the frame for the JGO. Orbit determination and manoeuvres uncertainties are added.

2011 AAS/AIAA Astrodynamics Specialist Conference, Girdwood, Alaska Page 43

Aug 2, 2011 Columbia B Session 14: Spacecraft GN&C Chair: Dr. Yanping Guo, APL

13:20 AAS 11 - 527 A General Event Location Algorithm with Applications to Eclipse and Station Line-Of-Sight Joel J. K. Parker and Steven P. Hughes, NASA GSFC A general-purpose algorithm for the detection and location of orbital events is developed. The proposed algorithm reduces the problem to a global root-finding problem by mapping events of interest (such as eclipses, station access events, etc.) to continuous, differentiable event functions. A stepping algorithm and a bracketing algorithm are used to detect and locate the roots. Examples of event functions and the stepping/bracketing algorithms are discussed, along with results indicating performance and accuracy in comparison to commercial tools across a variety of trajectories.

13:40 AAS 11 - 528 Cassini Solstice Mission Maneuver Experience: Year One Sean V. Wagner, Juan Arrieta, Christopher G. Ballard, Yungsun Hahn, Paul W. Stumpf and Powtawche N. Valerino, JPL/Caltech The Cassini-Huygens spacecraft began its four-year Prime Mission to study Saturn's system in July 2004. Two tour extensions followed: a two-year Equinox Mission beginning in July 2008 and a seven- year Solstice Mission starting in September 2010. This paper highlights Cassini maneuver activities from June 2010 through June 2011, covering the transition from the Equinox to Solstice Mission, and included 38 scheduled maneuvers, nine targeted Titan flybys, three targeted Enceladus flybys, and one close Rhea flyby. In addition, beyond the demanding nominal navigation schedule, numerous unforeseen challenges further complicated maneuver operations, and will be discussed. 14:00 AAS 11 - 529 Earth Orientation Parameter Considerations for Precise Spacecraft Operations Ben K. Bradley, Aurore Sibois and Penina Axelrad, University of Colorado at Boulder David A. Vallado, Analytical Graphics Inc. Earth orientation parameters (EOP) are crucial for correctly executing the GCRF/ITRF frame transformations, affecting parameters such as station coordinates, satellite positions, and non- spherical gravitational acceleration vectors. EOP interpolation methods and ocean tide corrections have been shown to have a notable impact on these precise frame transformations. This paper provides information regarding the accuracies and speeds of available methods that should be considered when using EOPs, allowing satellite operators and astrodynamicists to make informed decisions when choosing the best implementation for their individual needs. 14:20 AAS 11 - 530 Flight Path Control Design for the Cassini Solstice Mission Christopher G. Ballard, Juan Arrieta, Yungsun Hahn, Paul W. Stumpf, Powtawche N. Valerino, and Sean V. Wagner, JPL/Caltech The Cassini spacecraft has been in orbit around Saturn for nearly 6 years, with a planned 7-year extension, called the Solstice Mission, which started on October 1, 2010. The Solstice Mission includes 205 maneuvers and 70 flybys which consist of the moons Titan, Enceladus, Dione, and Rhea. This paper presents an overview of the planned maneuvers for the Solstice Mission along with the statistical predictions and analysis. 14:40 AAS 11 - 531 GNC Algorithm Design for Asteroid Intercept Missions with Precision Targeting Requirements Matt Hawkins, Yanning Guo and Bong Wie, Iowa State University Rendezvous and intercept missions to smaller asteroids require precision guidance and control in the terminal mission phase. The Zero-Effort Miss distance (ZEM) and Zero-Effort Velocity (ZEV) information are used to formulate autonomous feedback guidance laws. A terminal-phase guidance strategy for a variety of intercept missions is developed. Different types of navigation information assumed to be available from different spacecraft configurations and hardware choices. Guidance laws are developed for different mission configuration options. Guidance laws for both rendezvous and impact are studied. Fuel-optimized guidance laws are also investigated for asteroid intercept/rendezvous missions. Simulations show the effectiveness of the various guidance laws. 15:00 Break

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15:30 AAS 11 - 532 Guidance and Navigation Linear Covariance Analysis for Lunar Powered Decent Travis J. Moesser, ATK; David K. Geller, and Shane Robinson, Utah State University A linear covariance analysis is conducted to assess closed-loop guidance, navigation, and control system (GN&C) performance of the Altair vehicle during lunar powered descent. Guidance algorithms designed for lunar landing are presented and incorporated into the closed-loop covariance equations. Navigation-based event triggering is also included in the covariance formulation to trigger maneuvers and control dispersions. Several navigation and guidance trade studies are presented demonstrating the influence of triggering and guidance and study parameters on the vehicle GN&C performance. 15:50 AAS 11 - 533 Low-Thrust Adaptive Guidance Scheme Accounting For Engine Performance Degradation Iman Alizadeh, Solmaz Sajjadi-kia and Benjamin Villac, University of California at Irvine This paper aims at designing an indirect adaptive guidance scheme based on Modified-Gain Extended Kalman Filter (MGEKF) and an Extended Linear Quadratic Gaussian (ELQG) controller to generate control laws that are robust to large perturbations from the nominal performance. The method is applied to the problem of Variable Specific Impulse (VSI) low-thrust spacecraft transfer subject to engine performance degradation. In the Jupiter-Europa system, it is shown that the proposed guidance scheme has better recovery characteristics and can indeed reduce the risk of impact due to large changes in the engine operating conditions which is typical for low-thrust engines. 16:10 AAS 11 - 534 Preliminary Analysis for the Navigation of Multiple-satellite-aided Capture Sequences at Jupiter Alfred Lynam and James Longuski, Purdue University Multiple-satellite-aided capture employing gravity assists of more than one Galilean moon can help capture a spacecraft into orbit about Jupiter. Each additional moon flyby reduces the propulsive delta- v required for Jupiter capture. While the existence of these trajectories has been demonstrated deterministically, the challenges associated with actually navigating a spacecraft through several close flybys in rapid succession are nontrivial. This paper addresses these navigational challenges by using simulated observations to estimate a spacecraft's orbit as it approaches Jupiter and by targeting trajectory correction maneuvers to guide the spacecraft through multiple-satellite-aided capture sequences. 16:30 AAS 11 - 535 Radar Altimetry and Velocimetry for Inertial Navigation: A Lunar Landing Example Todd Ely and Alexandra Chau, Jet Propulsion Laboratory The traditional role that altimetry and velocimetry have played in spacecraft landings is to provide a direct measure of the spacecraft's surface altitude and surface relative velocity; however, their role in determining an inertial position and velocity has seen limited investigation. In this study, inertially sensitive measurement models for altimetry and velocimetry are formulated that include relevant instrument and environment error models. These models are applied and simulated for a realistic lunar landing scenario that is based on recent work for NASA's Altair lander. The results indicate that inertial landing accuracies of several meters are possible. 16:50 AAS 11 - 536 Variable State Size Optimization Problems In Astrodynamics: N-Impulse Orbital Maneuvers Troy Henderson, Virginia Tech; Dario Izzo, ESA This paper details recent results in variable state size optimization problems in astrodynamics. The application presented in this paper is optimal N-impulse orbital maneuvers. Previous work required the user to choose the number of impulses, N, while the current work considers N as a variable to be optimized, making the state size a variable throughout the optimization process.

2011 AAS/AIAA Astrodynamics Specialist Conference, Girdwood, Alaska Page 45

Aug 2, 2011 Columbia C Session 15: Satellite Constellations Chair: Dr. Ossama Abdelkhalik, Michigan Tech University

13:20 AAS 11 - 538 Constellation Design for Space Based Situational Awareness Applications: An Analytical Approach A.D. Biria and B.G. Marchand, The University of Texas at Austin Optimization processes rely on the availability of a pre-defined cost function. Generally, such representations are often analytically available. However, when considering optimal constellation design for space situational awareness applications, a closed-form representation of the cost index is only available under specific assumptions. The present investigation focuses on a subset of cases that admit exact representations. In this case, geometrical arguments are employed to establish an analytical formulation for the coverage area provided and the coverage multiplicity. These results are essential in validating numerical approximations that are able to address more complex configurations.

13:40 AAS 11 - 539 Coverage Analysis of Specified Area for an Agile Earth Observation Satellite Shenggang Liu, Chao Han, Beihang University, China The agile Earth observation satellite is a new generation of remote sensing satellite with high ability of attitude maneuver in the observing activities. Coverage analysis is an essential but difficult problem in its mission design, plan and scheduling. In this paper, geometry models of coverage analysis are built for different observing mode of an agile satellite in low earth orbit (LEO).According to the capability feature of on-board instruments, a method of specified area projection transformation and dynamic decomposition is proposed for analyzing the coverage problem. A numerical simulation was presented to demonstrate the feasibility and validity of the proposed method. 14:00 AAS 11 - 540 Deriving global time-variable gravity from precise orbits of the Iridium NEXT constellation Brian C. Gunter, J. Encarnacao, P. Ditmar, R. Klees, L. Van Barneveld and P. Visser, Delft University of Technology The goal of this study will be to investigate whether the precise positioning required for gravity field modeling can be achieved for the planned Iridium NEXT satellites. The focus will be on identifying the various sources of orbit error that might be expected for the Iridium NEXT mission, and to assess whether such errors can be mitigated through improved knowledge of certain spacecraft properties or with the addition of extra spacecraft sensors. 14:20 AAS 11 - 541 Estimation of Atmospheric and Ionospheric Effects in Multi-Satellite Orbit Determination Using Crosslinks Joanna Hinks and Mark Psiaki, Cornell University A method is proposed for determining the orbits of multiple satellites in the same orbital plane using both downlink and crosslink radio-navigation signals. This scheme considers orbit perturbations due to atmospheric drag and ionospheric delay effects on crosslink ranging measurements. By simultaneously estimating satellite orbits and density distributions for the atmosphere and ionosphere, orbit accuracy is improved while variations in the space environment are sensed. The satellites encounter roughly the same density features with a time delay, which implies that errors due to both atmospheric drag and ionospheric delay are spatially correlated. This correlation is exploited rather than ignored. 14:40 AAS 11 - 542 Numerical Continuation of Optimal Spacecraft Placements for LiAISON Constellations Channing Chow, University of Southern California; Benjamin Villac, University of California, Irvine An anticipated need for continuing space exploration is space-based infrastructure that provides navigation and communications support to space traffic in the larger cislunar region. This study leverages previous work that establishes the methodology for selecting candidate orbits and determining optimal satellite configurations for LiAISON constellations. While the previous work provides pointwise analysis, this study presents algorithms to efficiently extend solutions to larger design spaces by employing numerical continuation techniques and parallel processing enhancements to circumvent computational bottlenecks. Two case studies are presented of three and four spacecraft over the subset of periodic orbits in the restricted Earth-Moon system. 15:00 Break

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15:30 AAS 11 - 543 Optimal Constellation Design for Space Based Situational Awareness Applications: A Numerical Approach A.T. Takano and B.G. Marchand, The University of Texas at Austin Modern space situational awareness (SSA) is focused on the detection, tracking, identification, and characterization (DTI&C) of passive and active resident space objects (RSO's). In the past, the DTI&C of RSO's relied primarily on ground-based sensors. However, difficulties arise when smaller RSO's are considered, in the nano- or pico-satellite range for instance. To supplement ground sensing capabilities, a constellation of space based sensors is envisioned. In this study, concepts from computer graphicsand numerical optimization are fused into a unique constellation design approach for Space Based Space Situational Awareness (SBSSA) applications. 15:50 AAS 11 - 544 Strategy for Mitigating Collisions Between Landsat 5 and the Afternoon Constellation Joshua A. Levi and Eric J. Palmer, a.i. solutions, Inc. The NASA Goddard Space Flight Center Earth Science Mission Operations project, the French space agency Centre National d'Etudes Spatiales, and the Geological Survey all operate spacecraft in sun-synchronous frozen orbits. The orbits are planned to not place any of the spacecraft at risk of colliding with another. However as the Landsat 5 and Afternoon Constellation orbits evolved, this compromised the safe interaction between each spacecraft. This paper analyzes the interactions between the Landsat 5 spacecraft and the Afternoon Constellation over a period of 6 years, describing the current risk and plan to mitigate collisions in the future. 16:10 AAS 11 - 545 The Implementation Of MPI In The Autonomous Navigation Of Constellation Xiaofang Zhao and Chao Han, Beihang University. The autonomous navigation of constellation can be decoupled into the autonomous orbit determination and time synchronization through dual directional range measurements. The computation is of complexity, huge burden of computation and low speed which requires high performance on-board computer. In accordance with this character, the Messaging Passing Interface is inducted to parallelize the constellation navigation. The process is simulated based on MPI and speedup and parallel efficiency are used to evaluate algorithm performance. Simulation results show that the algorithm speedups the computation and it is meaningful to use parallel navigation algorithm when the constellation has more member satellite.

2011 AAS/AIAA Astrodynamics Specialist Conference, Girdwood, Alaska Page 47

Aug 2, 2011 Kahiltna Ct Session 16: Special Topic: MESSENGER at Mercury Chair: Mr. James McAdams, JHU/Applied Physics Laboratory Mr. Kenneth Williams, KinetX, Inc.

13:20 AAS 11 - 546 MESSENGER - Six Primary Maneuvers, Six Planetary Flybys, and 6.6 Years to Mercury Orbit James V. McAdams, Dawn P. Moessner, and Daniel J. O'Shaughnessy, The Johns Hopkins University Applied Physics Laboratory; Kenneth E. Williams, Anthony H. Taylor, and Brian R. Page, KinetX, Inc. On 18 March 2011, the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft became the first probe to orbit Mercury. The spacecraft's 6.6-year journey to Mercury orbit included six large trajectory-correction maneuvers and six planetary flybys. These planetary gravity assists imparted the vast majority of velocity change required to transform the spacecraft trajectory from Earth orbit departure to Mercury arrival. This paper will summarize the design and performance of all planetary flybys and course-correction maneuvers through orbit insertion, as well as the results of targeting the planetary-flyby aim points using acceleration on the spacecraft due to solar radiation pressure.

13:40 AAS 11 - 547 The MESSENGER Spacecraft's Orbit-Phase Trajectory Dawn P. Moessner and James V. McAdams, The Johns Hopkins University Applied Physics Laboratory After MESSENGER's 18 March 2011 Mercury orbit insertion (MOI), the spacecraft began its year-long primary science mission. Trajectory perturbations from solar gravity, Mercury gravity field variation, and solar radiation pressure shift orbit periapsis higher in altitude and Mercury latitude. Five orbit correction maneuvers (OCMs) will either lower periapsis altitude or increase orbit period. After the primary mission, MESSENGER will either drift until impacting Mercury or begin an extended mission. A potential extended mission requires that OCMs minimize deviation from the desired orbit. Final results for MOI and the first OCM will be presented along with nominal and extended mission trajectories. 14:00 AAS 11 - 548 Achievable Force-Model Accuracies for MESSENGER While in Mercury Orbit Dale R. Stanbridge, Kenneth E. Williams, Anthony H. Taylor, Brian R. Page, Christopher G. Bryan, David W. Dunham, Peter J. Wolff and Bobby G. Williams KinetX; James V. McAdams and Dawn P. Moessner, Johns Hopkins University Applied Physics Laboratory The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission is the seventh mission in NASA's Discovery Program. The spacecraft, launched from Cape Canaveral in August 2004, will arrive in orbit about Mercury in March 2011 to begin a one-year scientific investigation. While in orbit, the spacecraft will be subject to a variety of forces, including Mercury and solar gravity, solar and planetary radiation effects, and propulsive events associated with orbit correction and momentum desaturation. This paper describes the challenges of achieving the highest accuracy possible for force models to support orbit determination and reconstruction over the Mercury orbital phase. 14:20 AAS 11 - 549 Applying Experience from Mercury Encounters to MESSENGER's Mercury Orbital Mission Phase Brian R. Page, KinetX, Kenneth E. Williams, Anthony H. Taylor, Dale R. Stanbridge, Christopher G. Bryan, Peter J. Wolff and Bobby G. Williams, KinetX; Daniel J. O'Shaughnessy, Sarah H. Flanigan, Johns Hopkins University Applied Physics Laboratory The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission is the seventh mission in NASA's Discovery Program. The spacecraft was launched in August 2004 to begin an interplanetary cruise to arrive in orbit about Mercury in March 2011 for a one-year scientific investigation. The cruise phase included six planetary gravity-assist flybys. Since the first Mercury encounter, solar sailing has been employed successfully for trajectory correction. This paper describes the navigation performance achieved for the three Mercury flybys and how experiences gained during cruise phase have been applied to support Mercury orbit insertion and maintenance during the Mercury orbital phase.

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14:40 AAS 11 - 550 Guidance and Control of the MESSENGER Spacecraft in the Mercury Orbital Environment Sarah H. Flanigan, Robin M. Vaughan, and Daniel J. O'Shaughnessy, The Johns Hopkins University Applied Physics Laboratory The MESSENGER spacecraft faces a demanding environment while in orbit about Mercury. During the one-year-long orbit phase the guidance and control subsystem faces challenging constraints, most of which were not encountered during the cruise phase, and must incorporate the planning and approval of each weekly command load within only a three-week period. This paper details the analyses that were performed to develop a streamlined and effective methodology for adhering to orbital constraints. The methodology, which has proven effective in ensuring spacecraft health and safety while in orbit about Mercury, is detailed. 15:00 Break

15:30 AAS 11 - 551 MESSENGER Spacecraft Pointing Performance during the Mission's Mercury Orbital Phase Robin M. Vaughan, Daniel J. O'Shaughnessy, Sarah H. Flanigan, The Johns Hopkins University Applied Physics Laboratory A number of attitude changes are executed daily by the MESSENGER spacecraft in orbit about Mercury to collect and return science measurements to Earth. Prior to orbit insertion in March 2011, several analyses were performed and a flight test was executed by the spacecraft in August 2010 to verify that the guidance and control system is capable of executing the orbital attitude profiles within the required accuracy. This paper compares the desired attitude profiles with profiles obtained from ground simulations and with attitude telemetry from the flight test and from selected weeks in orbit between March and July of 2011. 15:50 AAS 11 - 552 Modeling the Effects of Albedo and Infrared Radiation Pressures on the MESSENGER Spacecraft Christopher J. Scott, James V. McAdams, Dawn P. Moessner, and Carl J. Ercol, The Johns Hopkins University Applied Physics Laboratory While MESSENGER is in orbit about Mercury, the navigation team will refine a spherical harmonic gravity-field model that requires accurate estimation of all perturbing accelerations including those induced by Mercury's surface albedo and infrared radiation. The incident flux on each spacecraft surface is estimated and converted into perturbing accelerations, which are then incorporated into a propagation model within the STK (Satellite Tool Kit) Astrogator module. This paper outlines the calculation andpredicted effects of these perturbing accelerations on the MESSENGER spacecraft throughout the mission's Mercury orbital phase.

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Aug 3, 2011 Columbia A Session 17: Trajectory Optimization II Chair: Dr. Chris Ranieri, The Aerospace Corporation

08:00 AAS 11 - 553 2011 Mars Science Laboratory Launch Period Design Fernando Abilleira, Jet Propulsion Laboratory The Mars Science Laboratory mission set to launch in the fall of 2011 has the primary objective of landing the most advanced rover to date to the surface of Mars to assess if Mars ever was, or is still today, able to sustain carbon-based life. Arriving at Mars in August 2012, the Mars Science Laboratory will also demonstrate the ability to deliver large payloads to the surface of Mars, land more precisely in a 20-km by 25-km ellipse, and traverse up to 20 km. This paper discusses the final launch/arrival strategy selected.

08:20 AAS 11 - 555 Approximation of Constraint Low-Thrust Space Trajectories using Fourier Series Ehsan Taheri and Ossama Abdelkhalik, Michigan Tech University Finite Fourier series is implemented for rapid low-thrust rendezvous trajectory approximation, in the presence of thrust acceleration constraints. The new representation along with the constraint handling capability makes this method suitable for low-thrust trajectory feasibility assessments, which is crucial in mission planning. In addition, the resulting solutions are good initial guesses for direct optimization techniques. Two rendezvous example problems are analyzed: a simple Earth-Mars problem and a typical LEO-to-GEO. Results, clearly depicts the advantage of this method as a general method applicable to a wide range of problems. 08:40 AAS 11 - 556 Closed-form and numerically-stable solutions to problems related to the optimal two-impulse transfer between specified terminal states of Keplerian or Juan S. Senent, NASA Johnson Space Center Houston The first part of the paper presents some closed-form solutions to the optimal two-impulse transfer between fixed position and velocity vectors on Keplerian orbits when some constraints are imposed on the magnitude of the initial and final impulses. Additionally, a numerically-stable gradient-free algorithm with guaranteed convergence is presented for the minimum delta-v two-impulse transfer. In the second part of the paper, cooperative bargaining theory is used to solve some two-impulse transfer problemswhen the initial and final impulses are carried by different vehicles or when the goal is to minimize the delta-v and the time-of-flight at the same time. 09:00 AAS 11 - 557 Coast Arcs in Optimal Multiburn Orbital Transfers Binfeng Pan and Zheng Chen, Northwestern Polytechnical University, China; Ping Lu, Iowa State University The determination of the durations of the coast arcs in an optimal finite-thrust, multiple-burn orbital transfer problem is investigated in detail in this paper.The conclusions arrived in the paper provide some sharp contrast to recently published results. Unlike existing approaches which rely on relatively crude numerical searches for the correct switching time and suffer from potential failures, this paper shows that the correct zero of the switching function can either be obtained in closed form under a linear gravity model, or determined accurately and reliably by solving a polynomial of at most degree 5 under the inverse-square gravity model. 09:20 AAS 11 - 558 Implicit Solution for the Low-thrust Lambert Problem by Means of a Perturbative Expansion of Equinoctial Elements G. Avanzini, Università del Salento; A. Palmas, University of Glasgow; E. Vellutini, Politecnico di Torino This paper discusses a method for solving the so-called low-thrust Lambert's problem. The problem is formulated as a boundary value one, where the initial and final points are provided in terms of equinoctial variables. A first-order perturbative method is used for evaluating the variation of orbital elements induced by the low-thrust propulsion system, which acts as a perturbative parameter with respect to the reference, Keplerian motion (zero-thrust case). An implicit formulation is thus obtained which allows for the determination of the low-thrust transfer trajectory driving the equinoctial parameters from the initial to their final values in a prescribed time. 09:40 Break

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10:10 AAS 11 - 559 Optimization of Stable MultiI-Impulse Transfers Navid Nakhjiri and Benjamin Villac, University of California at Irvine This paper addresses the optimization of stable multi-impulse transfers. These transfers allow a spacecraft to coast near families of stable periodic orbits while staying within the associated stability region. They result in fail-safe transfers with respect to miss-thrust and may provide an interesting strategy for human mission to small bodies. The optimization problem considered consists of the minimization of sequences of small impulses transferring a spacecraft between two given periodic orbits within a stable family, under path and impulse constraints to stay within the stability region. A two-level optimization strategy is proposed that results in locally optimal transfers. 10:30 AAS 11 - 560 Trajectory Optimization Employing Direct Implicit Integration of 2nd Order Dynamical Systems and Non-Linear Programming Stephen W. Paris, Boeing Research & Technology Typically numerical solutions of 2nd order dynamical systems are accomplished by transforming the 2nd order dynamics into an equivalent 1st order system. Implicit integration can allow for efficient direct solution of 2nd order dynamical systems. This combined with nonlinear programming provides a more efficient technique for trajectory optimization. Compact schemes based on implicit integration for solving optimal trajectory problems based on 1st and order 2nd dynamical systems are presented. Computationexperiences are given for applying and comparing these trajectory optimization methods to aerospace problems. The results demonstrate significant computational efficiencies by direct solution of the native 2nd order dynamical system. 10:50 AAS 11 - 452 Ephemeris Model Optimization of Lunar Orbit Insertion From a Free Return Trajectory Mark Jesick and Cesar Ocampo, The University of Texas at Austin With the discovery of water ice at the moon's south pole, future human lunar exploration will likely occur at polar sites and, therefore, require high inclination orbits. This work details an automated architecture for constructing minimum-fuel lunar orbit insertion sequences while ensuring crew safety by maintaining a ballistic Earth return trajectory, which is free to vary during optimization. The Jacobian of the constraints is derived analytically to eliminate the need for finite difference approximations; where necessary, gradients are determined with linear perturbation theory. The impulsive solution's optimality is confirmed with primer vector theory before conversion to a finite thrust model. 11:10 AAS 11 - 562 Low-Thrust Control of Lunar Orbits Nathan Harl and Henry J. Pernicka, Missouri University of Science & Technology A technique for stationkeeping low-altitude lunar orbits using continuous low-thrust is presented. The method involves the use of a general performance index, which is designed to minimize the difference between the instantaneous orbital elements of the spacecraft and some desired set of orbital elements. To minimize the user-defined performance index, a Sequential Quadratic Programming algorithm is used. The primary application of the general controller design in this study is the problem of generating and maintaining low-altitude, polar, Sun-synchronous orbits about the Moon. Such orbits are useful for lunar mapping missions, such as with NASA's Lunar Reconnaissance Orbiter (LRO) mission. 11:30 AAS 11 - 612 Taylor Series Trajectory Calculations Including Oblateness Effects and Variable Atmospheric Density James R. Scott, NASA Glenn Research Center Taylor series integration is implemented in NASA Glenn's Spacecraft N-body Analysis Program, and compared head-to-head with the code's existing 8th-order Runge-Kutta Fehlberg time integration scheme. This paper focuses on trajectory problems that include oblateness and/or variable atmospheric density. Taylor series is shown to be significantly faster and more accurate for oblateness problems up through a 4x4 field, with speedups ranging from a factor of 2 to 12. For problems with variable atmospheric density, speedups average 25 for atmospheric density alone, and average 1.6 to 8.4 when density and oblateness are combined.

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Aug 3, 2011 Columbia B Session 18: Attitude D&C I Chair: Dr. Don Mackison, University of Colorado

08:00 AAS 11 - 563 Attitude Motion of Spacecraft with Geometrically Distributed Multiple Liquid Stores Jun Hyung Lee , Youchul Hwang , Hyunsu Kim, Ja-Young Kang and Byeong-Sun Yoo, Korea Aerospace University In this study, we will develop physical and mathematical models for attitude motion of a spacecraft which is equipped with l thrusters, m control wheels and n liquid propellant tanks, and perform computer simulations for various parameters values. Finally some analytical work will be made for a brief understanding the slosh effect on the attitude motion of the spacecraft. We will also investigate how slosh mass changes mass properties of the system such as c.g. and moments of inertia during maneuvers.

08:20 AAS 11 - 564 Attitude Propagation for a Slewing Angular Rate Vector with Time Varying Slew Rate Russel Patera, The Aerospace Corporation A method is proposed that can accurately propagate aerospace vehicle attitude using its angular rate vector that is slewing with a time dependent slew rate. The method involves transforming the attitude propagation problem to one or more slewing coordinate frames in which the angular rate remains nearly fixed in direction. Once solved in the slewing frame, the attitude is transformed to the initial vehicle frame. For pure coning motion with a time dependent slew rate magnitude, the method yields an analytical solution. The method can be used in vehicle simulations or in flight computers using angular rates or angular rate 08:40 AAS 11 - 565 Automatic mass balancing for small Three-Axis spacecraft simulator using sliding masses only Simone Chesi, Veronica Pellegrini and Qi Gong, University of California Santa Cruz; Marcello Romano and Roberto Cristi, Naval Postgraduate School. Small satellites spacecraft simulator is a very useful tool for developing, improving and verifying spacecraft attitude control algorithms. Accurate ground testing of spacecraft attitude dynamics and control requires a frictionless and space-like environment that is simulated using spherical air bearing. The major disturbance torque is due to misalignment between the spacecraft center of gravity and center of rotation. This paper introduces a novel automatic mass balancing technique that allows to drastically reduce the gravitational torque by real-time relocation of the spacecraft center of mass into the center of rotation, using adaptive dynamical nonlinear feedback control law. 09:00 AAS 11 - 566 Evaluating the Robustness to Model Error of Multi-period Repetitive Control Edwin S. Ahn and Richard W. Longman, Columbia University; Jae J. Kim, Naval Postgraduate School Spacecraft often have reaction wheels or control moment gyros. Slight imbalance in each can cause spacecraft vibrations with three or four different periods associated with each wheel's rotation. Previous publications developed the theory for multiple period repetitive control systems. This paper examines the stability robustness of such multiple period repetitive control to model errors. Techniques are developed to understand the tolerance to model error which is necessarily much more complicated than the single period case. The effects of various design parameters on the stability robustness are also investigated. 09:20 AAS 11 - 567 Nonlinear Control Analysis Of A Double Gimbal Variable Speed Control Moment Gyro Daan Stevenson and Hanspeter Schaub; University of Colorado Boulder A double gimbal variable speed control moment gyro (DG) is considered as a method of spacecraft attitude control. The system's equations of motion and control theory are developed, with gimbal and wheel accelerations prescribed as control inputs. Analysis of the control theory suggests that the same torque amplification effects exist as in a single gimbal control moment gyro, but control by a single DG device is not robust due to potential singularity configurations. Cross products containing the desired control variables encumber the control law, but when these terms are feedback compensated, a simulation with successful reference trajectory tracking is achieved. 09:40 Break

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10:10 AAS 11 - 568 Single-axis pointing of a magnetically actuated spacecraft: a non-nominal Euler axis approach Emanuele Luigi de Angelis and Fabrizio Giulietti, University of Bologna; Giulio Avanzini, University of Salento The problem of attitude control can be expressed in terms of Euler axis/angle, where a nominal Euler axis rotation directly takes the spacecraft from an initial attitude to a desired final one. When three independent control torques are not available, e.g. when magnetic torquers are the only attitude effectors, the nominal rotation cannot be performed. Nonetheless a feasible rotation around a 'non- nominal' axis allows exact pointing of a given body-fixed axis towards any prescribed target direction. This geometric property results into a control law that enables magnetically actuated spacecraft to align and spin around a desired direction. 10:30 AAS 11 - 569 Solution of Spacecraft Attitude Via Angular Momentum in Body and Inertial Frames Mohammad A. Ayoubi, Santa Clara University; Damon Landau, Jet Propulsion Laboratory; and James M. Longuski, Purdue University Attitude solutions for spin-stabilized rigid spacecraft are presented that are direct functions of the torque and angular momentum vectors in the body and in the inertial frame. Two solutions are found: an approximate solution and an exact algebraic solution. Unfortunately, in applications, the algebraic method is not practical because the torque and angular momentum vectors usually are not precisely known in the inertial frame. The approximate method, which tolerates approximate values is verified numerically for a spin-stabilized rigid spacecraft in the following three maneuver cases: 1) the spinning, thrusting problem, 2) the thrust ramp-up problem, and 3) the spin-up problem. 10:50 AAS 11 - 603 Star Tracker Only Attitude and Rate Estimation Tom Dzamba, Christy Fernando, John Enright; Ryerson University Star trackers have the potential to be an enabling technology for small satellites as they can provide three-axis attitude determination from a single sensor. In addition to this, many studies have shown that it is possible to achieve rate determination capabilities from a star tracker. We develop an algorithm for angular rate determination that utilizes the size of the imaged point spread functions and two sequential star images. We utilize these measurements in an extended Kalman filter and compare the performance of this star tracker only attitude determination system to a conventional star tracker/rate gyro combination. 11:10 AAS 11 - 572 Magnetometer-Only Attitude Determination Using Two-Step Kalman Filter Jason Searcy and Henry Pernicka, Missouri University of Science and Technology A flexible and computationally efficient method for solving the spacecraft attitude using only an inexpensive and reliable magnetometer would be very useful for satellite missions, particularly those with modest budgets. The primary challenge is that magnetometers only instantaneously resolve two axes of the spacecraft attitude. Typically, magnetometers are used in conjunction with other sensors to resolve all three axes. However, by using a filter over an adequately long orbit arc, the magnetometer data can yield full attitude, and in real time. The method presented solves the problem using a two-step extended Kalman filter. 11:30 AAS 11 - 571 Attitude Control Of The Spacecraft With Swiveling Orbit Control Engine During The Propulsion Wenshu Wei, Wuxing Jing, and Yingjing Qian, Harbin Institute of Technology A research is presented to solve the problem that the thrust vector of swiveling engine on variable- mass vehicle could not only track changes of centroid position but also point to a fixed direction in inertial space. In this paper, the variable-mass vehicle is considered to be consisted of two parts - a two-way swiveling engine and a variable-mass platform. The mathematical model of the complex variable-mass system is established by using the Reynolds Migration Theorem. Besides, during the control system design, quaternion is converted into three quasi-Euler angles by means of a linear transformation and the on-off control law is designed on

2011 AAS/AIAA Astrodynamics Specialist Conference, Girdwood, Alaska Page 53

Aug 3, 2011 Columbia C Session 19: Orbit Estimation II Chair: Dr. Thomas Eller, Astro USA, LLC

08:20 AAS 11 - 574 Applications of the Admissible Region to Space-Based Observations K. Fujimoto and D. J. Scheeres, The University of Colorado-Boulder Situational awareness of Earth-orbiting particles such as active satellites and space debris is highly important for all current and future space-faring nations. Fujimoto and Scheeres have proposed a correlation and initial orbit determination technique for ground based optical observations where multiple admissible region maps are intersected in the Poincare orbit element space. In this paper, we introduce a new application of the admissible region to space-based observations. A modification must be made to the correlation process as the observer's state is always a valid solution. Numerical examples for several observation scenarios are discussed, including LEO-on-GEO and GEO-on-GEO observations.

08:40 AAS 11 - 575 Coupling of Nonlinear Estimation and Dynamic Sensor Tasking Applied to Space Situational Awareness Patrick S. Williams and David B. Spencer, The Pennsylvania State University; R. Scott Erwin, Air Force Research Laboratory This paper examines the effect of nonlinear filter selection on sensor tasking decisions and overall estimation performance in Space Situational Awareness (SSA). The SSA system is characterized by the fact that the number of objects tracked severely outnumbers available sensors, complicating both the estimation and tasking processes by potentially creating long periods of unobservability. A closed loop system of estimation using both an Extended Kalman Filter and Unscented Kalman Filter, alongside a tasking algorithm utilizing Fisher Information and Lyapunov Exponent analysis to help understand performance discrepancies between success in this particular method of tasking, and choice of nonlinear estimator. 09:00 AAS 11 - 576 Covariance-Driven Sensor Network Tasking for Diverse Space Objects Keric Hill, PaulSydney, Randy Cortez and Daron Nishimoto, Pacific Defense Solutions, LLC Previous studies have shown that using covariance information for scheduling observations of resident space objects (RSOs) can lead to significant improvements in orbit determination accuracy. That was done by maximizing the effectiveness of observations in reducing some measure of uncertainty in the RSO orbit state, but results were shown for a limited set of RSOs which were all in similar orbits. In this study, methods are presented that use covariance to drive the sensor scheduling for observations andwhich are applicable to RSOs in diverse orbit regimes and where some RSOs are given a higher priority than others. 09:20 AAS 11 - 578 Maneuver Event Detection and Reconstruction Using Body-Centric Acceleration/Jerk Optimization D.L. Oltrogge, Analytical Graphics, Inc. Maneuver detection and calibration for arbitrary satellites observed using Non-Cooperative Tracking techniques is a challenging problem. In this paper, we derive a new burn reconstruction model better suited to Earth-pointing satellites capable of performing long-duration maneuver in the body frame. We then at-tempt to reconstruct unknown maneuvers using only the pre- and post-burn ephemerides and the new reconstruction technique. Maneuver start and stop time are determined by minimizing the weighted position and velocity residuals at the end of the burn. We then compare the optimized burn conditions with simulated actual burn conditions. 09:40 Break

10:10 AAS 11 - 579 Satellite Location Uncertainty Prediction Felix R. Hoots, The Aerpace Corporation The location of a satellite in space is typically described by an element set or state vector at some epoch time and the uncertainty is described by a covariance. The probability density function is usually assumed to be Gaussian. Nonlinearities introduce significant errors in the propagation of the covariance and have been a topic of several recent papers. We have developed a method to remove most of the nonlinearities and provide accurate propagation of the covariance for 30 days or more. The accuracy of the covariance is within a few percent when compared to Monte Carlo simulation.

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10:30 AAS 11 - 580 Simulating Space Surveillance Networks David A. Vallado, Center for Space Standards and Innovation; Jake Griesbach, Analytical Graphics Inc. The Chinese anti-satellite test in January 2007 and Iridium collision in February 2009 produced thousands of pieces of debris, straining many tracking and orbit determination capabilities. It created an instant need for accurate simulations to understand the changing environment for future satellite collisions. While many tools exist, a comprehensive listing of sensor locations and characteristics is difficult to find. In addition, operational start and stop dates are not well known. This paper summarizes open source data to establish a baseline of sensor locations, primarily using Google Earth. These data will provide a common baseline from which to simulate satellite observations, 10:50 AAS 11 - 581 Solar Radiation Pressure Binning for the Geosynchronous Orbit Matthew D. Hejduk, a.i. solutions, inc. The effect of atmospheric drag on satellites can be characterized by an orbital energy dissipation rate, a construct that combines both atmospheric density and satellite frontal area characteristics; groupings defined by this parameter are good predictors of orbital maintenance difficulty. A similar framework can be defined for solar radiation pressure, combining incident solar flux, exposed area, and reflectivity into a single parameter from which groupings can be defined. Solar radiation pressure and orbit accuracy are examined for all of the catalogued geosynchronous satellites to define solar radiation pressure groups to serve as predictors of vector accuracy and thus tracking requirements. 11:10 AAS 11 - 582 Space Object Tracking in the Presence of Attitude-Dependent Solar Radiation Pressure Effects Kyle J. DeMars and Moriba Jah, Air Force Research Laboratory; Robert H. Bishop, Marquette University The tracking of space objects (SOs) is often accomplished via measurement systems such as optical telescopes; however, the actual observations occur infrequently, which leads to long time periods during which the SO uncertainty must be propagated. Given that the uncertainty associated with an SO is described by a probability density function (pdf), the infrequent measurements and subsequent long arcs of propagation lead to difficulties in reacquiring the SO due to inaccurate methods for the propagation of the pdf. This paper examines improvements to uncertainty prediction when attitude- dependent solar radiation pressure effects are present using a splitting Gaussian mixtures algorithm.

2011 AAS/AIAA Astrodynamics Specialist Conference, Girdwood, Alaska Page 55

Aug 3, 2011 Kahiltna Ct Session 20: Spacecraft Autonomy Chair: Dr. Craig McLaughlin, University of Kansas

08:00 AAS 11 - 583 Application of Artificial Potential Function Methods to Autonomous Space Flight S.K Scarritt and B.G. Marchand, The University of Texas at Austin The goal of this investigation is to identify a systematic approach for the determination of accurate startup arcs for autonomous spacecraft path planning and guidance. This capability is of particular interest for on-demand onboard determination. Artificial potential function methods are common in the field of path planning. However, the resulting control requirements are not always feasible in practice due to various hardware and mission constraints. Still, the general concept is useful in the determination of suitable startup arcs for autonomous algorithms that are capable of addressing these actuator constraints on demand.

08:20 AAS 11 - 584 Autonomous Optimal Deorbit Guidance Morgan Baldwin, AFRL; Ping Lu, Iowa State University This work presents a study on autonomous guidance of deorbit maneuvers. The problem is for a vehicle to autonomously execute a minimum-fuel, finite-time deorbit maneuver that achieves desired entry interface conditions. This work explores the different finite-time burn maneuvers to yield the optimal deorbit guidance solution. More specifically, the differences between the single and multiple burn(s) are explored. General entry interface targeting conditions are formulated to allow variable dependence among flight path angle, velocity, and range-to-go. For numerical solutions, an analytical multiple-shooting algorithm is used. Numerical simulation results are provided to demonstrate the method. 08:40 AAS 11 - 585 Autonomous Precision Orbit Control For Earth-Referenced Flight Path Repeat Toru Yamamoto, Isao Kawano, Takanori Iwata, Yoshihisa Arikawa, Hiroyuki Itoh, Japan Aerospace Exploration Agency; Masayuki Yamamoto, Ken Nakajima, Mitsubishi Space Software Co., Ltd. Recently satellites with synthetic aperture radars (SAR) have stringent requirements to achieve precise orbit control of Earth-referenced repeating orbits for effective repeat-pass SAR interferometry. Frequent orbit maneuvers are necessary and it can be a burden for daily ground operations. To achieve high accuracy with low workload, the new autonomous orbit control method has been studied. Both in-plane and out-of-plane maneuvers are performed autonomously. The "maneuver slots" concept is applied to let the on-board algorithm decide the maneuver timing and avoid conflicts with mission observation. The outcome of this research is planned to be implemented for Japanese Earth observation satellite ALOS-2. 09:00 AAS 11 - 586 Design and Flight Implementation of Operationally Relevant Time-Optimal Spacecraft Maneuvers Mark Karpenko and I. M. Ross, Naval Postgraduate School; S. Bhatt and N. Bedrossian, Charles Stark Draper Laboratories This paper presents the design and implementation of several operationally relevant time-optimal maneuvering experiments carried out on the TRACE spacecraft. The time-optimal maneuvers are designed by constructing an appropriate optimal control problem formulation from a detailed model of the spacecraft dynamics and reaction wheel-based attitude control system. The optimization model is solved using the pseudospectral method and includes practical constraints on the spacecraft performance including the nonlinear reaction wheel torque-momentum envelope. The flight results clearly show that the application of optimal control theory for maneuver design extends the capabilities of the spacecraft over a wide envelope. 09:20 AAS 11 - 587 Designing Stable Iterative Learning Control Systems from Frequency Response Based Repetitive Control Designs Benjamas Panomruttanarug, King Mongkut's University of Technology; Richard W. Longman, Columbia University; Minh Q. Phan, Dartmouth College Repetitive control (RC) and iterative learning control (ILC) design control systems that aim for zero error in repeating situations. ILC applies to spacecraft problems that perform repeated scanning maneuvers with a fine pointing instrument. Very effective RC design methods use steady state frequency response approaches. This work converts this RC design method to apply to the ILC problem. ILC wants zero error in a finite time maneuver, and hence steady state frequency response does not apply. We show that adjusting only a few gains in the ILC gain matrix can achieve stable and effective ILC laws from the RC designs.

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09:40 Break

10:10 AAS 11 - 588 Optimal Feedback Guidance Algorithms for Asteroid Proximity Operations Yanning Guo, Matt Hawkins, and Bong Wie, Iowa State University Optimal feedback guidance algorithms, which can be employed for asteroid or planetary proximity operations with a variety of terminal constraints, are investigated in this paper. Although classical optimal feedback guidance algorithms, such as Constrained Terminal Velocity Guidance (CTVG) and Free Terminal Velocity Guidance (FTVG), have been known in the literature, we present some new results. It is shown that for the FTVG, there exists a local minimum solution for an optimal time-to-go under a certain set of initial conditions. It is also shown that a simple combination of the CTVG and FTVG results in a Terminal Velocity Pointing Guidance (TVPG). 10:30 AAS 11 - 589 On Multi-Input Multi-Output Repetitive Control Design Methods Kevin Xu and Richard W. Longman, Columbia University; Jer-Nan Juang, National Cheng Kung University; Minh Q. Phan, Dartmouth College Repetitive control (RC) can address the common spacecraft jitter problem for fine pointing equipment resulting from small imbalance in reaction wheels or CMG's. This problem required multi-input, multi- output (MIMO) RC design methods. A previous papers by the authors developed a rather comprehensive MIMO RC theory. This paper examines four different design approaches. One stays on the MIMO level optimizing a MIMO frequency based cost function. Other methods reduce MIMO problem to a set of single-input, single-output problems, and design with SISO methods. The SISO methods are seen to have an advantage, and can be applied directly from input-output data. 10:50 AAS 11 - 590 Satellite Position And Attitude Control By On-Off Thrusters Considering Mass Change Yasuhiro Yoshimura, Takashi Matsuno and Shinji Hokamoto, Department of Aeronautics and Astronautics Kyushu University This paper deals with the two-dimensional position and attitude control of a satellite by two on-off thrusters. The thrusters are fixed with the satellite's body and generate the constant force magnitudes. Considering the mass change due to the thruster usage, this paper proposes the two-dimensional position and attitude control law using the two on-off thrusters. First, the approximate analytical solutions of the satellite's motion are derived utilizing Fresnel Integrals. Then, we propose the position and attitude control procedure by two on-off thrusters. Finally, the numerical simulations are shown to verify the effectiveness of the proposed controller. 11:10 AAS 11 - 591 Stabilizing Intersample Error in Iterative Learning Control Using Multiple Zero Order Holds Each Time Step Te Li, Richard W. Longman, Yunde Shi, Columbia University, New York, NY Iterative learning control (ILC) aims for zero tracking error in a control system that performs the same tracking command repeatedly. Spacecraft applications include repeated scanning maneuvers with fine pointing equipment. Previous research shows that zero tracking error every step results in unstable control action, with the error between time steps growing exponentially. This paper considers a general hold, using e.g. 4 zero order hold values each step. These extra control actions minimize a quadratic penalty function on error and control effort. This approach is studied mathematically and in simulations, and shown to make a promising method of addressing the problem. 11:30 AAS 11 - 592 Tracking Control of Nanosatellites with Uncertain Time Varying Parameters D. Thakur and B. G. Marchand, The University of Texas at Austin The focus of this study is an adaptive control scheme that maintains consistent satellite attitude tracking performance in the presence of uncertain time-varying inertia parameters. Potentially large variations in the inertia matrix may occur due to changes in fuel mass, fuel slosh, and deployable payload such as booms and solar arrays. As such, the assumption of a constant inertia matrix may not suffice for precise tracking maneuvers. The present investigation develops an appropriate description for a class of time-dependent inertia uncertainty. An adaptive control law is implemented to recover closed-loop stability and accurate attitude and angular velocity tracking in the face of such parametric uncertainty.

2011 AAS/AIAA Astrodynamics Specialist Conference, Girdwood, Alaska Page 57

Aug 3, 2011 Columbia A Session 21: Orbital Debris II Chair: Dr. Felix Hoots, The Aerospace Corporation

13:20 AAS 11 - 593 Attitude Control and Orbital Dynamics Challenges of Decommissioning the First 3-Axis Stabilized Tracking and Data Relay Satellite as a Spinner abo Charles A. Benet, Orbital Sciences Corporation Launched in 1983 on board Space Shuttle Challenger, the First Tracking and Data Relay Satellite (TDRS-1) vacated the Geosynchronous Orbit (GEO) on June 27th 2010 . To meet NASA requirements to limit Orbital Debris, TDRS-, originally designed as a 3-axis stabilized satellite, was decommissioned as a Spinner due to a variety of constraints. This paper focuses on the challenges encountered to maintain adequate spinning dynamics and disposal orbit characteristics while repetitively firing thrusters to meet the fuel depletion requirement.

13:40 AAS 11 - 594 Averaged Dynamics of HAMR Objects: Effects of Attitude and Earth Oblateness Aaron Rosengren and Daniel Scheeres, University of Colorado at Boulder HAMR objects in high-Earth orbit are subject to strong SRP effects in addition to higher-order Earth gravity field and luni-solar perturbations. The dynamics of these objects have been explored in recent years, finding extreme variations in eccentricity and inclination due to these combined effects. This paper will describe the effects of attitude on the averaged solution to the SRP perturbed orbiter problem. We show that if the orientation changes with respect to the Sun-line, the object can evolve through a variety of solutions characterized by the SRP perturbation angle. Finally, we discuss modifications to include perturbations from the Earth's oblateness. 14:00 AAS 11 - 595 Effective Strategy to Identify Origins of Fragments from Breakups in GEO Masahiko Uetsuhara and Toshiya Hanada, Kyushu University; Yukihito Kitazawa, IHI Corporation This paper proposes a search strategy to effectively detect and identify fragments from confirmed and/or unconfirmed breakups in GEO based upon orbital debris modeling techniques. The modeling techniques describe debris generation and propagation to predict population and motion of fragmentation debris from breakups. This search strategy is superior to the existing survey observations in terms of the efficiency on origin identification of fragments from breakups. This paper demonstrates how the search strategy identifies the origin of detected objects and confirms the effectiveness of the search strategy. 14:40 AAS 11 - 597 Uncertainty In Lifetime Of Highly Eccentric Transfer Orbits Due To Solar Resonances Alan B. Jenkin and John P. McVey, The Aerospace Corporation Disposal orbit studies performed by the authors over many years have shown that highly eccentric transfer orbits can have significant variability in orbital lifetime. The resulting uncertainty in predicted lifetime has made it difficult to assess compliance with disposal requirements. In this study, the cause of the lifetime variability was investigated by multi-processor precision long-term in- tegration and inspection of the orbital element equations of variation. Results showed that lifetime variability is caused by solar resonances. The effect of these resonances cannot be predicted for commonly used transfer orbits, making it difficult to assure disposal compliance. 15:00 Break

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Aug 3, 2011 Columbia B Session 22: Attitude D&C II Chair: Renato Zanetti, The Charles Stark Draper Laboratory

13:20 AAS 11 - 598 An Extended Kalman Smoother for the DICE Mission Attitude Determination Post Processing with Double Electrical Field Probe Inclusion Mikulas Jandak, Cranfield University, Rees Fullmer, Utah State University This paper describes a post-processing attitude determination tool for the spin-stabilized DICE spacecraft based on two optimal quaternion-based Kalman filters. Those filters are combined into a fixed-interval extended Kalman smoother. Simulated results showed that the extended Kalman smoother can effectively reduce the covariance of the estimation by 40%. The integration of the electrical field science probes with a magnetometer is shown to improve the attitude accuracy about 3.5 times in the eclipse on average. The simulated results also show that the improvement in the estimation is not constant but it depends on the spacecraft position on the orbit.

13:40 AAS 11 - 599 Experimental Testing of the Accuracy of Attitude Determination Solutions for a Spin-Stabilized Spacecraft Keegan Ryan, Rees Fullmer, Steve Wassom, Utah State University Spin-stabilized spacecraft rely on sun and three-axis magnetic field sensor measurements for attitude determination. This study experimentally determines the accuracy of attitude determination solutions using modest quality sensors. The experimental testing quantifies the contributing error sources from the sensors, errors associated with their integration, and the propagation of these errors into the estimation solution. A test spacecraft will collect data during spinning motion and the attitude estimates will be compared to the experimentally measured attitude. Once validated, this approach will be used to test the accuracy of the attitude determination system of the DICE spacecraft as built by SDL/USU. 14:00 AAS 11 - 600 Initial Attitude Analysis of the RAX Satellite John C. Springmann and James W. Cutler, University of Michigan This paper discusses calibration and attitude estimation techniques used on flight data from the Radio Aurora Explorer (RAX) satellite, which was launched November 19, 2010 on a mission to study plasma irregularities in the ionosphere. RAX utilizes a passive magnetic attitude control system and magnetometers, coarse sun sensors, and a three-axis rate gyro for attitude determination. We have extended on-orbit, attitude-independent magnetometer calibration algorithms to include time-varying affects from the electrical power system, and use attitude-independent techniques to study sun sensor performance. An extended Kalman filter is used for attitude estimation. Resulting accuracies of the determination system are discussed. 14:40 AAS 11 - 602 Spectral Star Tracker using Bayer Filter APS Geoffrey McVittie and John Enright, Ryerson University In this study, star tracker operation is extended by measuring star spectral characteristics in combination with position. Spectral information is obtained with a bayer pattern active pixel sensor (APS), providing a three colour component measurement. Estimation of star spectra is performed using a least squares fit to the observed point spread function. Effectiveness of the spectral estimation techniques are considered with respect to different PSF models, detector noise, variation in the observed point spread function (PSF), and stellar magnitude. Validation is provided via a combination of simulation, laboratory testing and empirical observations. 15:00 Break

2011 AAS/AIAA Astrodynamics Specialist Conference, Girdwood, Alaska Page 59

Aug 3, 2011 Columbia C Session 23: Orbit Estimation III Chair: Bob Glover, AT&T

13:20 AAS 11 - 604 Application of the Transformation of Variables Technique for Uncertainty Mapping in Nonlinear Filtering Ryan M. Weisman, Manoranjan Majji, and Kyle T. Alfriend, Texas A&M University This research addresses how nonlinear observations of state variables corrupt the accuracy of state estimation algorithms with emphasis on the uncertainty associated with the state estimate. This work applies the transformation of variables technique to exactly map the measurement uncertainty distribution into the state variable domain. This mapping produces knowledge of the system likelihood distribution allowing for a better idea of where the true system state values lie in the state domain. Since the likelihood distribution is exactly mapped between domains, Bayesian estimation is able to be more appropriately carried out given the state prior distribution is appropriately characterized.

13:40 AAS 11 - 605 Computational Efficiency of a Hybrid Mass Concentration and Spherical Harmonic Modeling Nathan Piepgrass and David Geller, Utah State University Through Spherical Harmonics, one can describe complex gravitational fields. However as the order and degree of the spherical harmonics increases, the computation speed rises exponentially. A partial and feasible solution was to supplant the spherical harmonic models in the flight software. The spherical harmonics gravity model can be replaced by a hybrid model, a mass concentrations model and a secondary (lesser degree or order) spherical harmonics model. That hybrid model can lead to faster processing speeds. The accuracy and improvement in processing speed between the hybrid model and a lunar spherical harmonic model are evaluated. 14:00 AAS 11 - 606 Evaluation of the Information Content of Observations with Application to Sensor Management for Orbit Determination Kyle J. DeMars and Moriba Jah, Air Force Research Laboratory Information regarding the state of a space object (SO) is typically gathered via measurement systems such as optical telescopes or radar systems. As measurement systems become more advanced, a greater number of SOs can be detected which leads to an ever-increasing number of tracked SOs. As such, the efficient utilization of tracking resources becomes a vital concern so that valuable sensor resources are used to their full extent. This work examines information-theoretic approaches to determining the information content of observations and compares the different methods to an existing scheme in the context of assessing the measurement utility for orbit determination. 14:20 AAS 11 - 607 QQ-Plot for Sequential Orbit Determination James R Wright, Analytical Graphics, Inc. Use of the Kalman measurement update theorem incurs the requirement that each post-fit measurement residual ratio is Normal. When the residual sample size is small, comparison to the normal curve is not useful because small-sample normal distributions do not resemble the infinite- distribution normal curve, and because quantitative bounds are not available for the comparison. My problem is to define and demonstrate a normality test to either accept or reject any ensemble of measurement residual ratios. Thequantile-quantile (QQ) plot with Royston-Michael acceptance boundaries is useful for small and large ensembles. Application of the QQ-Plot to measurement residual ratios is new. 14:40 AAS 11 - 608 Sparse Grid-Based Orbit Uncertainty Propagation Matthew D. Navels, Bin Jia, Ming Xin, and Yang Cheng, Mississippi State University A sparse grid-based orbit uncertainty propagation method is presented. The idea of the sparse grid method is to represent the initial orbit uncertainty by a six-dimensional sparse grid, propagate each and every sparse grid points individually through the nonlinear orbit dynamics, and compute the statistical moments, e.g., mean and covariance, of the orbit from the propagated sparse grid points. The Smolyak rule is used to generate the sparse grid through linear combinations of low-level tensor products. The sparse grid method is a generalization of the Unscented Transformation (UT) of the Unscented Kalman Filter and can achieve higher accuracy than UT. 15:00 Break

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Aug 3, 2011 Kahiltna Ct Session 24: Space Environment Chair: Dr. Matthew Berry, Analytical Graphics, inc

13:20 AAS 11 - 609 Density and Ballistic Coefficient Estimation Revisited Piyush M. Mehta and Craig A. McLaughlin, The University of Kansas. Orbit determination for low Earth orbit satellites depends highly on atmospheric density modeling. This paper examines the effects of ballistic coefficient errors in using precision orbit ephemerides (POE) as measurements to estimate total density along the satellite orbit. A precision orbit determination process is used to estimate density using the Challenging Minisatellite Payload and Gravity Recovery and Climate Experiment precision orbit data. The paper also examines the simultaneous estimation of density and ballistic coefficient. POE derived densities correlate well with accelerometer derived densities, but density error does have some correlation with estimated ballistic coefficient.

13:40 AAS 11 - 610 Global Atmospheric Density Esitmaton using a Sequential Filter/Smoother James Woodburn and John Seago, Analytical Graphics, Inc. The application of sequential methods to the estimation of corrections to global atmospheric density models is investigated. Potential advantages over least squares include the ability to estimation correction parameters as time varying quantities, the elimination of discontinuities in correction estimates at fit boundaries and reduced computational burden. An optimal sequential filter and a variable lag smoother are utilized to determine the effect of model parameterization on observability and recovery of temperature errors within the reference density model and the relationship between the latency and accuracy of the correction estimates. 14:00 AAS 11 - 611 Mini-satellite for Drag Estimation (MinDE): A Satellite as a Sensor System Kyle Fanelli, Justin Rothenberg, Kyle Gradeless, Rayna Thompson, James McCarthy, David Kornblum, Dr. Bogdan Udrea, Embry Riddle Aeronautical University; Federico Herrero, NASA Goddard Space Flight Center Determining an accurate model of the atmosphere between 200-500km requires accurate measurements of total densities and composition. To do this, drag coefficients must be predicted with a level of accuracy surpassing previous drag satellites. This is achieved using the momentum transfer ratio and expressing the drag coefficient in terms of measurable momentum transfer parameters, and simulated using rarefied gas dynamics. The goal is to use a satellite with a complex shape which has a very well defined drag coefficient, along with highly accurate accelerometers and miniaturized mass spectrometers, to reduce the uncertainty of the drag measurement to 1% or less. 14:20 AAS 11 - 475 Combining Precision Orbit Derived Density Estimates Dhaval Mysore Krishna and Craig A. McLaughlin, The University of Kansas This paper attempts to create continuous datasets and improve the atmospheric density estimates obtained from the precision orbit ephemerides (POE) for the Challenging Minisatellite Payload, and Gravity Recovery And Climate Experiment satellite. Two approaches are followed; the first method is to blend the density data during the overlap period using the linear weighted blending technique and the second method is to blend the POE position vectors using the same technique, and use them as measurements in an optimal orbit determination technique to estimate the densities. The results showed that the first method was more accurate for both the satellites. 14:40 AAS 11 - 613 Time Periods of Anomalous Density for GRACE and CHAMP Craig A. McLaughlin, Eric Fattig, Travis Locke and Piyush M. Mehta, University of Kansas While developing precision orbit ephemeris (POE) derived densities for GRACE and CHAMP, several periods have been found when the correlation between the POE derived density and accelerometer derived density is very low. The primary time period where this occurs is from October 2005 to January 2006 for GRACE. This time period includes the maneuvers required for the GRACE satellites to switch positions, but extend well before and after this event. The low correlations also exist between HASDM and accelerometer derived densities for this time period. This paper characterizes these time periods and attempts to explain the anomalous behavior. 15:00 Break

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Aug 4, 2011 Columbia A Session 25: Trajectory Optimization III Chair: Roby Wilson, JPL

08:00 AAS 11 - 614 A Linear Correction Approach For Precision Interplanetary Transfer Trajectory Design Zhong-Sheng Wang, Embry-Riddle Aeronautical University. The iteration may not converge when linear correction is applied in precision interplanetary transfer trajectory design since it is dealing with a nonlinear dynamic system. This paper proposed a revised 2-step procedure for precision transfer trajectory design: first, find the approximate values of perigee parameters using 2-body analysis (lunar mission) or patched conic analysis (Mars mission); secondly, apply the "rope-climbing" algorithm. The algorithm works by transforming the targeting problem of anonlinear dynamic system to a series of linear corrections. Numeric examples show that this procedure works effectively.

08:20 AAS 11 - 615 A Survey of Mission Opportunities to Kuiper Belt Objects Ryan McGranaghan, Brent Sagan, Gemma Dove, Aaron Tullos, Dr. J.E. Lyne and Joshua Emery, University of Tennessee; Jerry Horsewood, Spaceflight Solutions This paper details the design of mission trajectories to the large Kuiper Belt Objects Quaoar, Sedna, Makemake, and Haumea. Optimization parameters include the total delta-V, trip time, and Vinf on arrival. The best trajectories identified have values for these parameters comparable to those of the New Horizons mission to Pluto. Results of a trade study will be presented to show the injected mass capability for various commercial launch vehicles and the mass margins they provide for different mission scenarios; scientific objectives and and instrumentation necessary to fulfill the mission's goals will be discussed. 08:40 AAS 11 - 616 Application of Multiobjective Design Exploration to SOLAR-C Orbit Design Akira Oyama and Yasuhiro Kawakatsu, Japan Aerospace Exploration Agency; Kazuko Hagiwara, Mitsubishi Space Software Co. Ltd. Multiobjective design exploration (MODE) framework is applied to the trajectory design problem for SOLAR-C Plan A SEP option. Present approach revealed some important design knowledge such as tradeoff information among maximization of final mass, maximization of final velocity, and maximization of minimum distance from the Sun. Present study also shows possibility of simultaneous design of trajectory and spacecraft. 09:40 Break

10:10 AAS 11 - 620 Multi-Gravity-Assist Trajectories Optimization: Comparison between the Hidden Genes and the Dynamic-Size Multiple Populations Genetic Algorithms Ossama Abdelkhalik, Michigan Tech University The problem of optimal design of a multi-gravity-assist space trajectory, with free number of deep space maneuvers (MGADSM), poses a multi-modal cost function. In the general form of the problem, the number of design variables is solution dependent. This paper presents a comparison between two recently developed genetic-based methods to handle global optimization problems where the number of design variables vary from one solution to another. The first method is the hidden genes genetic algorithms (HGGA) and the second method is the dynamic-size multiple populations genetic algorithms (DSMPGA). 10:30 AAS 11 - 621 Orbital Stability around Planetary Satellites as Optimization Problem G.Orlando, E.Mooij and R.Noomen, Delft University of Technology This paper explores the problem of orbital stability of spacecraft around planetary satellites (i.e. moons) under the influence of the gravitational pull of the primary planet and the currently available methods to define long-term stable orbits through analytical evaluation of the initial osculating orbital parameters. Two new methods that are presented here aim to treat the problem of long-term orbital stability around planetary satellites as an optimization problem. The new methods differ in terms of definition of the objective function, thus providing differences in performance and applications. Numerical results for a ”Mission to Triton” study case are given and discussed.

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10:50 AAS 11 - 622 Optimal Transfer and Science Orbit Design in the Proximity of Small Bodies Christopher J. Scott and Martin T. Ozimek, The Johns Hopkins University Applied Physics Laboratory This study details a robust and systematic approach for generating science orbits connected by fuel optimal transfers in the small body regime. The Clohessy-Wiltshire equations provide an analytical means to globally interpret the design space allowing a designer to quickly investigate families of science orbits and obtain closed-form optimal transfer. Solutions are refined with multiple shooting and nonlinear programming to transition the results into Hill's equations, and finally, a high-fidelity ephemeris model including plate model gravity. The final result is an accurate solution retaining the initial design characteristics with further fuel savings that are available from exploiting the high-fidelity perturbations. 11:10 AAS 11 - 623 Trajectories to Uranus Using Gravity-Assists from Venus, Earth, Mars, Jupiter, and Saturn Christopher M. Spreen and James M. Longuski, Purdue University The goal of this paper is to compile a catalogue of trajectories to Uranus for launch between the years 2020 and 2060. Ballistic gravity-assist trajectories are identified using patched-conic techniques. Classical trajectories, as well as less conventional trajectories, are considered and compared. Only trajectories with flight times of 15 years or less are considered. The best trajectories in terms of parameters such as time of flight, launch date, and delta-V cost are presented and discussed. Thesetrajectories are then numerically integrated and optimized (for minimum delta-V or minimum time of flight) using JPL's Computer Algorithm for Trajectory Optimization (CATO).

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Aug 4, 2011 Columbia B Session 26: Large Space Structures and Tethers Chair: Dr. David Spencer, Penn State University

08:00 AAS 11 - 625 Analysis Of The Out-Of-Plane Dynamics Of A Tether Sling Stationed On A Rotating Body Steve Tragesser, University of Colorado at Colorado Springs; Luis Baars, Braxton Technologies LLC Previous studies on the design of a tether sling have suggested that such a facility must be located at the poles of a moon or asteroid in order to align the angular momentum vectors of the moon and tether. This paper analyzes the out-of-plane motion induced from rotation of the body on which the facility is stationed. While large out-of-plane oscillations are present in the open-loop behavior, the motion stabilizes about a limit cycle with a relatively small amplitude. The mechanism for this stabilization is considered and the out-of-plane oscillation amplitude is characterized with respect to system parameters.

08:20 AAS 11 - 626 Asteroid Diversion Using Tethers M.J. Mashayekhi and Arun K.Misra; McGill University Potential earth impact threats posed by asteroids have motivated researchers to find effective NEO diversion techniques. Several means to perturb the motion of an asteroid have been discussed in the literature. Attaching a long tether and ballast mass to the asteroid can effectively alter its trajectory. In this paper it is shown that cutting the tether at an appropriate time can enhance the diversion achieved. The instant of cutting the tether significantly affects the final orbit of the asteroid and thus the resulting diversion. The best cut point is decided via optimization. Optimization results are also presented in this paper. 08:40 AAS 11 - 627 Attitude Controllability of an Underactuated Flexible Spacecraft Wang Dongxia, Jia Yinghong and Jin Lei, Beihang university This paper studies the attitude controllability of an underactuated flexible spacecraft, which has only two thrusters and a flexible beam having merely one degree of freedom. Firstly, we establish the dynamical model using the assumed mode method. Secondly, neglecting the elastic deformations of the beam, we analyze the state controllability of the corresponding rigid system according to weakly positively Poisson stable and Lie algebra rank condition. Finally, the impact of flexible beam reckoned in, the vibration controllability of the system is discussed through the controllability matrix judgment theorem. The article offers the preconditional guide on designing the control law. 09:20 AAS 11 - 629 Deployment Dynamics of a Large Solar Array Paddle Takanori Iwata, Japan Aerospace Exploration Agency; Kiyoshi Fujii and Kazuro Matsumoto, NEC TOSHIBA Space Systems The Advanced Land Observing Satellite (ALOS) successfully deployed its large solar array paddle on orbit, which is one of the largest single-wing paddle and accomplished the largest passive deployment of a rigid paddle. This paper describes a design optimization for the ALOS's paddle deployment with various practical constraints, and presents ground verification results including deployment analyses and deployment tests. An effect of attitude motion was assessed, and deployment robustness analyses assuming off-nominal conditions were performed to identify margins and critical failures. Flight data including telemetries and monitor camera images were analyzed to correlate them with the pre-flight analyses. 09:40 Break

10:10 AAS 11 - 630 Dynamics Of A Moon-Anchored Tether With Variable Length Anna D. Guerman University of Beira Interior, Alexandre Burov and Ivan Kosenko, Computing Center of the Russian Academy of Sciences; We consider dynamics of spacecraft tethered to the surface of a planet, planet moon or asteroid. We study the possibility to provide some particular solutions to the equations of motion for future application as nominal motions in the respective control system. We show that these solutions can be implemented by variation of the system's parameters, e.g., the length of the tether.

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10:30 AAS 11 - 631 Effects of J2 Perturbations on Multi-Tethered Satellite Formations G. Avanzini, Università del Salento; M. Fedi, Universitat Politècnica de Catalunya This paper discusses the relevance of J2 effects induced by Earth's oblateness on a tethered formation, when a massive cable model is included in the dynamic analysis of a multi-tethered satellite formation. The formations examined in this study are Hub-And-Spoke (HAS) and Closed- Hub-And-Spoke (CHAS) configurations for In-Plane and Earth-Facing spin planes. Some configurations present a cluster with deputies affected differently by the J2 potential depending on their initial position with respect to the orbital plane. The differences in stability, elongation of tethers and shapes of the formations under the J2 potential are compared with those in absence of the perturbation. 10:50 AAS 11 - 632 Analysis of a Tethered Coulomb Structure Applied to Close Proximity Situational Awareness Carl R. Seubert, Stephen Panosian and Hanspeter Schaub; University of Colorado at Boulder A unique tether application for situational awareness at geosynchronous altitudes is investigated. The relative dynamics between a small sensor platform tethered to a large spacecraft is examined. Charging both craft to |30|kV holds the relative dynamics fixed in the presence of gravitational and solar radiation forces. Numerical simulations illustrate multiple tether connections increase the stiffness and allow 10m separated craft to yield relative variations less than 50mm in translation and 5 degrees in attitude. It is also shown that in nominal plasma conditions less than 20W of power along with only grams of propellant are required to maintain spacecraft potentials. 11:10 AAS 11 - 633 Orbit Control Method for Solar Sail Demonstrator IKAROS via Spin Rate Control Yuya Mimasu, Masaki Nakamiya, Ryu Funase, Takanao Saiki, Yuichi Tsuda, Osamu Mori, and Jun'ichiro Kawaguchi, Japan Aerospace Exploration Agency (JAXA); Tomohiro Yamaguchi, The Graduate University for Advanced Studies; The Japan Aerospace Exploration Agency (JAXA) launched the world's first operational solar sail IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) on May, 2010. Although the attitude control of IKAROS is nominally performed by using a rhumb-line control, we found in the actual operation that the spin-axis direction also can be changed by controlling its spin rate under the SRP torque. The main achievement of this study is to construct the theory of this orbit control method under the photon attitude drift motion by controlling the spin rate, based on the actual flight results of the IKAROS.

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Aug 4, 2011 Columbia C Session 27: Optimal Control Chair: Rao Vadali, Texas A&M University

08:00 AAS 11 - 634 A Dynamic-Static Mesh Refinement Strategy for Solving Optimal Control Problems Camila Francolin, Michael A. Patterson, and Anil V. Rao, University of Florida A mesh refinement strategy for solving optimal control problems is presented. The refinement strategy consists of a dynamic and a static component running sequentially. The dynamic component is run on a coarse global mesh and attempts to capture discontinuities in the state and control through the analysis of active path constraints. Consecutively, the static component of the refinement improves on the accuracy of the solution by increasing the degree of the approximating polynomial or through further segmentation of the solution. Three benchmark examples were investigated and show that this method is very effective in capturing discontinuities, giving greater solution accuracies.

08:20 AAS 11 - 635 A Minimum Delta-V Orbit Maintenance Strategy for Low-Altitude Missions Using Burn Parameter Optimization Aaron Brown, NASA Johnson Space Center Orbit maintenance is the series of burns performed during a mission to ensure the orbit satisfies mission constraints. Low-altitude missions often require non-trivial orbit maintenance dV due to sizable orbital perturbations and minimum altitude thresholds. A strategy is presented for minimizing this dV using impulsive burn parameter optimization. An initial estimate for the burn parameters is generated by considering a feasible solution to the orbit maintenance problem. An example demonstrates the dVsavings from the feasible solution to the optimal solution. 09:00 AAS 11 - 637 An Exploration of the Optimum Two-Impulse Planar Transfers to Cyclers in the Earth-Moon System Saghar H.Sianaki and BenjaminVillac, University of California at Irvine This paper explores the optimum two-impulse transfer problem in a PCRTBP framework between a low Earth orbit and cyclers. We can find the feasible transfers by employing the Lambert's problem to provide effective initial guess to optimize the error in target position. Once the feasible trajectories are found, the impulse is a function of transfer time and the end points' phases. Next, impulse is optimized over transfer time for fixed end points. As end points are varied, we can study the optimal solutionsby contours. It is shown that Lambert does not work as initial guess for some regions. 09:20 AAS 11 - 639 Experimental Investigations of Trajectory Guidance and Control for Differential Games Neha Satak, Kurt Cavalieri, Clark Moody, Anshu Siddarth, and John E Hurtado, Texas A&M Univeristy; Rajnish Sharma, University of Alabama Pursuit-evasion games are multiplayer differential games that can commonly be posed as optimal control problems. Throughout the years, a number of optimal control techniques have been used to solve these differential game problems. The focus of this work is to compute feedback-based guidance and control strategies that are amenable for real-time implementation for differential game scenarios. These techniques will then be used to demonstrate the applicability of the control methods for a differential gameusing robotic platforms. The goal is also to study the performance of the techniques to practical implementation issues and suggest improvements and enhancements. 09:40 Break

10:10 AAS 11 - 640 Exploiting Sparsity in Direct Collocation Pseudospectral Methods for Solving Optimal Control Problems Michael A. Patterson and Anil V. Rao, University of Florida In a direct collocation pseudospectral method, a continuous-time optimal control problem is transcribed to a finite-dimensional nonlinear programming problem. Solving this nonlinear programming problem as efficiently as possible requires that sparsity at both the first and second- derivative levels be exploited. In this paper a computationally efficient method is developed for computing the first and second derivatives of the nonlinear programming problem functions arising from a pseudospectral discretization of a continuous-time optimal control problem. Specifically, expressions are derived for the objective function gradient, constraint Jacobian, and Lagrangian Hessian arising from the previously developed Radau pseudospectral method.

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10:30 AAS 11 - 641 Optimal Cooperative Deployment of a Two-Satellite Formation into a Highly Guido Colasurdo and Alessandro Zavoli, La Sapienza University; Lorenzo Casalino and Francesco Simeoni, Politecnico di Torino The indirect optimization of a two-spacecraft deployment into a highly elliptic orbit (HEO) is presented. The necessary condition for the optimality of the formation deployment are fully derived and a peculiar shooting technique, based on the Newton method, is described. An exhaustive numerical analysis has been carried out considering the unperturbed keplerian model; some results, taking the Lunisolar perturbation and the Earth Asphericity into account, are also presented. 10:50 AAS 11 - 642 Optimal Nonlinear Feedback Control For Control Constraints Problems With Terminal Constraints: An SDRE Approach Neha Satak, Texas A&M University; Rajnish Sharma ,University of Alabama; and John E. Hurtado, Texas A&M University This paper discusses new feedback control methods for finite-horizon optimal control problems (OCPs) with terminal and control constraints. The method of solution is based on an LQ type formulation that extends the SDRE approach of handling the finite-time OCPs with terminal constraints. Transforming the strict control constraints into smooth control functions is thoroughly analyzed with numerous examples. The methodology is further investigated to facilitate the new guidance laws using game-theoretic approach and the numerical solutions are compared with the respective results obtained by using open-loop methods. The main applications are shown in the areas of pursuit and evasion, trajectory optimization. 11:10 AAS 11 - 643 Spacecraft Proximity Maneuver Guidance Based on Inverse Dynamic and Sequential Gradient-Restoration Algorithm Marco Ciarcia and Marcello Romano, Naval Postgraduate School In the last decades real-time trajectory optimization is a research topic that has captured the attention of many research groups. While some methods have been developed to solve this task, few of them can allege full suitability in real-world application. In this work we couple the inverse dynamic in the virtual domain technique with the sequential gradient-restoration algorithm to generate, in real-time, suboptimal trajectories for close proximity maneuvers between a chaser and a moving non- cooperative target. Exhaustive sets of simulations have proven the suitability of the presented approach.

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Aug 4, 2011 Kahiltna Ct Session 28: Rendezvous Chair: Dr. Thomas Lovell, AFRL

08:00 AAS 11 - 644 A Comparison of Fixed-Terminal Direction Guidance Laws for Spacecraft Rendezvous Renato Zanetti and Fred D. Clark, The Charles Stark Draper Laboratory This work examines and compares two fixed-terminal direction guidance laws to rendezvous with a target in circular orbit. Both laws exactly satisfy the constraint. The first algorithm is based on the optimization of a quadratic performance index. The second algorithm has as many constraints as degrees of freedom and is the guidance law utilized by the Space Shuttle. Similarities and differences between the two approaches are discussed and numerical simulations are presented.

08:20 AAS 11 - 645 A Quadratically-Constrained LQR Approach for Finite-Thrust Orbital Rendezvous with Collision Avoidance Gregory Lantoine and Richard Epenoy, Centre National d'Etudes Spatiales. This paper focuses on the design of a quadratically-constrained Linear-Quadratic Regulator for finite- thrust orbital rendezvous. The original Linear-Quadratic optimal control problem is subject to maximum thrust magnitude and polyhedral collision avoidance constraints. Thrust arcs are approximated by impulsive velocity in-crements and the Yamanaka-Ankersen transition matrix propagates the state vector. An explicit closed-loop solution is obtained by performing high-order series expansions of the HJB equation on sub-regions of the state-space associated with specific sets of ac-tive constraints. A rendezvous in an elliptical orbit is considered to demonstrate the application of this method. 08:40 AAS 11 - 647 Asteroid Precision Landing Via Multiple Sliding Surfaces Guidance Techniques Roberto Furfaro and Daniel R. Wibben, University of Arizona Autonomous, close proximity operations in asteroids low-gravity environment is particularly challenging. A novel non-linear landing guidance scheme has been developed for spacecrafts that are required to execute autonomous closed-loop guidance to a designated point on the asteroid surface. Based on High Order Sliding Mode control theory, the proposed Multiple Sliding Surface Guidance (MSSG) algorithm has been designed to take advantage of the ability of the system to reach the sliding surface in a finite time. Preliminary results on Eros-based asteroid models show that the MSSG law is able to drive the spacecraft to the designated point with zero velocity. 09:00 AAS 11 - 649 HTV Relative Approach Performance Evaluation Based On On-orbit Rendezvous Flight Result Satoshi Ueda, Toru Kasai and Hirohiko Uematsu, Japan Aerospace Exploration Agency The H-II Transfer Vehicle (HTV), as an unmanned vehicle, conducts automatic rendezvous flight to the manned space station, therefore strict safety requirements are applied. During the HTV final approach along the R-bar, the HTV GN&C system continuously controls relative position so that its trajectory must keep within predefined approach corridor. For final robotic capture, fine position hold and attitude control performances are required when the HTV reaches about 10 m below the space station. This paper presents the HTV GN&C design for R-bar approach, analysis and test results, and the HTV 1st and 2nd flight on-orbit performance evaluation. 09:20 AAS 11 - 650 Multi-Maneuver Clohessy-Wiltshire Targeting David P. Dannemiller, NASA-Johnson Space Center A non-iterative method is presented for targeting a rendezvous scenario that includes a sequence of maneuvers and relative constraints. This method is referred to as Multi-Maneuver Clohessy-Wiltshire Targeting (MM_CW_TGT). When a single maneuver is targeted to a single relative position, the classic CW targeting solution is obtained. The MM_CW_TGT method involves manipulation of the CW state transition matrix to form a linear system. Solution of the linear system includes the straight- forward inverse of asquare matrix. Example solutions are presented for several rendezvous scenarios to illustrate the utility of the method. 09:40 Break

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10:10 AAS 11 - 651 Optimal Finite-Thrust Rendezvous Trajectories Found via Particle Swarm Algorithm Mauro Pontani, University of Rome "La Sapienza"; Bruce ConwayUniversity of Illinois at Urbana-Champaign The particle swarm optimization (PSO) technique represents an intuitive methodology for optimization. It mimics the stochastic motion of bird flocks while searching for food. This research applies the technique to determining optimal finite-thrust rendezvous trajectories in a rotating Euler- Hill frame. Hamiltonian methods are employed to translate the related optimal control problems into parameter optimization problems. Thus the parameters sought by the PSO are primarily initial values of the costates and the time intervals corresponding to thrust arcs. The PSO is extremely easy to program. Nevertheless, it is effective, reliable, and numerically accurate in solving the optimization problems of interest 10:30 AAS 11 - 652 Out-of-Plane Post-Escape Strategy for the ATV Arnaud Boutonnet, ESA-ESOC; Laurent Arzel, Booz&Co at ESA-ESOC; Emilio De Pasquale, ESA-ESOC While rendezvousing with the ISS, the ATV might trigger an escape manoeuvre to safely fly away from the ISS. A post-escape strategy is then performed to re-initiate the rendezvous. Reference strategy is in-plane: if the rendezvous is along minus Vbar, the ATV first flies below and then above the ISS. A new approach is proposed in this paper: by combining eccentricity vector, inclination vector and semi-major axis deviations, it is possible to fly around the ISS in a helix trajectory. This new approach permits reducing the DeltaV cost while increasing the safety margins 10:50 AAS 11 - 653 Precise Guidance and Landing Strategy of Space Probe by using Multiple Markers in Asteroid Exploration Mission Naoko Ogawa, Fuyuto Terui and Jun'ichiro Kawaguchi, Japan Aerospace Exploration Agency This paper proposes a novel strategy for a space probe to descent and land on the asteroid surface with high accuracy of a few meters by utilizing several artificial markers deployed from the probe. Results of a numerical experiment indicated that the proposed method showed higher performance than conventional one. It will allow us to guide the probe with high mobility to the desired points such as small craters, which will be of great significance for understanding local geology and geography of the asteroid, or avoiding boulders and too rough regions.

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AUTHOR INDEX

Author Author Session Author Session Session Boutonnet, A. 28 DeMars, K. 23 Abdelkhalik, O. 17 Bowes, A. 4 Di Lizia, P. 7 Abdelkhalik, O. 25 Bowes, A. 13 Di Mauro, G. 7 Abilleira, F. 17 Bradley, B. 14 Dichmann, D. 6 Abrahamson, M. 9 Broschart, S. 12 Ditmar, P. 15 Adamo, D. 5 Broschart, S. 13 Dolado, J. 2 Adebonojo, B. 5 Brown, A. 27 Dove, G. 25 Ahn, E. 18 Bryan, C. 16 Duncan, M. 8 Alfano, S. 2 Buckley, S. 7 Dunham, D. 16 Alfano, S. 7 Burov, A. 26 Dwyer Cianciolo, A. 4 Alfano, S. 8 Campagnola, S. 3 Dzamba, T. 18 Alfriend, K. 8 Canalias, E. 9 Ely, T. 13 Alfriend, K. 23 Carbonne, D. 9 Ely, T. 14 Alizadeh, I. 14 Carpenter, J. 8 Emery, J. 25 Allgeier, S. 10 Carrelli, D. 4 Encarnaç‹o, J. 15 Anderson, P. 1 Carrico III, J. 6 Enright, J. 18 Anderson, R. 3 Carrico, J. 6 Enright, J. 22 Anderson, R. 6 Casalino, L. 27 Epenoy, R. 28 Angelopoulos, V. 12 Cavalieri, K. 27 Ercol, C. 16 Aoshima, C. 11 Celik, H. 3 Erwin, R. 10 Ardaens, J. 10 Cersosimo, D. 1 Erwin, R. 19 Arikawa, Y. 20 Chan, J. 8 Fanelli, K. 24 Arora, N. 11 Chao, C. 2 Fattig, E. 24 Arrieta, J. 14 Chau, A. 14 Fedi, M. 26 Arzel, L. 28 Cheatwood, N. 13 Fernando, C. 18 Atchison, J. 7 Cheetham, B. 12 Ferreira, J. 6 Avanzini, G. 17 Chen, Z. 17 Finkleman, D. 8 Avanzini, G. 18 Cheng, Y. 23 Fitz-Coy, N. 10 Avanzini, G. 26 Chesi, S. 18 Flanigan, S. 16 Axelrad, P. 14 Chesley, S. 9 Folta, D. 12 Ayoubi, M. 18 Chishiki, Y. 13 Francesco, S. 27 Baars, L. 26 Chow, C. 15 Francolin, C. 27 Baldwin, M. 20 Chung, M. 9 Frigm, R. 8 Ballard, C. 14 Cianciolo, A. 13 Fujii, K. 26 Bando, M. 10 Ciarcia, M. 27 Fujimoto, K. 19 Barbee, B. 5 Clark, F. 28 Fullmer, R. 22 Bastida Virgili, B. 2 Colasurdo, G. 27 Funase, R. 9 Bauman, J. 11 Conway, B. 28 Funase, R. 13 Bedrossian, N. 20 Cortez, R. 19 Funase, R. 26 Bellerose, J. 1 Cosgrove, D. 12 Furfaro, R. 5 Bellerose, J. 9 Craychee, T. 2 Furfaro, R. 6 B_net, C. 21 Craychee, T. 6 Furfaro, R. 28 Berry, M. 9 Cristi, R. 18 Gao, Y. 2 Bhaskaran, S. 9 Cupples, M. 5 Garmier, R. 2 Bhatt, S. 20 Cutler, J. 22 Geller, D. 14 Binz, C. 8 D'Amico, S. 10 Geller, D. 23 Biria, A. 15 Dannemiller, D. 28 Getzandanner, K. 11 Bishop, R. 19 Davis, K. 3 Gillam, S. 9 Boere, M. 13 de Angelis, E. 18 Gong, Q. 18 Bombardelli, C. 5 De Pasquale, E. 28 Gradeless, K. 24 Boone, D. 13 de Weck, O. 13 Grebow, D. 3 Born, G. 3 Dec, J. 4 Greene, B. 2 Born, G. 11 Decker, D. 10 Griesbach, J. 19 Born, G. 12 DeMars, K. 19 Guerman, A. 26 Boutonnet, A. 13

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Author Session Author Session Author Session Gunter, B. 15 Jah, M. 19 Leonard, J. 11 Guo, Y. 14 Jah, M. 23 Levi, J. 15 Guo, Y. 20 Jalali Mashayekhi, M. 26 Li, T. 20 Hagiwara, k. 25 Jandak, M. 22 Liu, S. 15 Hahn, Y. 14 Jasper, L. 7 Llanos, P. 11 Halsell, C. 9 Jasper, L. 10 Locke, T. 24 Han, C. 6 Jefferson, D. 9 Longman, R. 18 Han, C. 10 Jenkin, A. 2 Longman, R. 20 Han, C. 15 Jenkin, A. 21 Longuski, J. 14 Hanada, T. 21 Jeon, G. 6 Longuski, J. 18 Harl, N. 17 Jesick, M. 17 Longuski, J. 25 Haw, R. 9 Jia, B. 23 Lovell, T. 10 Hawkins, M. 14 Jia, Y. 26 Lu, P. 17 Hawkins, M. 20 Jin, L. 26 Lu, P. 20 Hejduk, M. 8 Jing, W. 6 Luo, Q. 6 Hejduk, M. 19 Jing, W. 18 Lynam, A. 14 Helfrich, C. 9 Juang, J. 20 Lyne, J. 25 Helfrich, C. 13 Justh, H. 4 Ma, G. 9 Henderson, T. 14 Justus, C. 4 Maddock, R. 4 Hergenrother, C. 5 Kahle, R. 10 Majji, M. 23 Heritier, A. 10 Kaidy, J. 4 Marchand, B. 15 Herman, J. 3 Kang, J. 18 Marchand, B. 20 Herrero, F. 24 Kaplinger, B. 1 Marchese, J. 12 Hess, J. 10 Karpenko, M. 20 Markley, F. 8 Higa, E. 13 Kasai, T. 28 Maruskin, J. 9 Hill, K. 19 Kato, T. 11 Mathews, D. 9 Hinks, J. 15 Kawaguchi, J. 13 Matsumoto, K. 26 Hintz, G. 11 Kawaguchi, J. 26 Matsuno, T. 20 Hoffman, J. 13 Kawaguchi, J. 28 Mattingly, R. 13 Hogan, E. 7 kawakatsu, Y. 25 McAdams, J. 16 Hokamoto, S. 1 Kawano, I. 20 McCarthy, J. 24 Hokamoto, S. 20 Kelso, T. 2 McGranaghan, R. 25 Hoots, F. 19 Kidd, J. 5 McLaughlin, C. 24 Horsewood, J. 25 Kim, B. 8 McMahon, J. 3 Hosseini Sianaki, S. 27 Kim, B. 11 McVey, J. 2 Howell, K. 3 Kim, E. 8 McVittie, G. 22 Howell, K. 10 Kim, H. 8 Mehta, P. 24 Howell, K. 12 Kim, H. 11 Miller, J. 11 Huang, W. 10 Kim, H. 18 Mimasu, Y. 9 Hughes, S. 14 Kim, J. 18 Mimasu, Y. 13 Hurtado, J. 3 Kitazawa, Y. 21 Mimasu, Y. 26 Hurtado, J. 27 Klees, R. 15 Mingotti, G. 6 Hwang, I. 6 Kornblum, D. 24 Mink, R. 5 Hwang, Y. 11 Kosenko, I. 26 Misra, A. 26 Hwang, Y. 18 Krag, H. 2 Mitchell, L. 9 Ichikawa, A. 10 Landau, D. 5 Mithra, A. 9 Ichikawa, T. 11 Landau, D. 18 Miyahara, N. 11 Intelisano, M. 6 Lantoine, G. 28 Modenini, D. 11 Ishii, N. 11 Lavangna, M. 7 Moesser, T. 14 Ishimatsu, T. 13 Lee, B. 11 Moessner, D. 16 Itoh, H. 20 Lee, D. 6 Montenbruck, O. 10 Iwata, T. 20 Lee, J. 6 Moody, C. 27 Iwata, T. 26 Lee, J. 18 Mooij, E. 25 Izzo, D. 14 Legendre, P. 2 Mori, O. 26

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Author Session Author Session Author Session Morinelli, P. 12 Phan, M. 3 Scott, J. 17 Mottinger, N. 13 Phan, M. 20 Seago, J. 24 Murguia, J. 9 Phillips, R. 5 Searcy, J. 18 Murri, D. 4 Piepgrass, N. 23 Segerman, A. 8 Mysore Krishna, D. 24 Pitz, A. 1 Selnick, S. 6 Nakajima, K. 20 Plakalovic, D. 8 Senent, J. 17 Nakamiya, M. 26 Plice, L. 6 Seubert, C. 26 Nakhjiri, N. 17 Polito, C. 1 Sharma, R. 27 Narvet, S. 8 Pontani, M. 28 Shaughnessy, D. 16 Nevels, M. 23 Powell, R. 4 Shi, Y. 20 Newman, B. 7 Prince, J. 4 Shirasawa, Y. 13 Newman, L. 8 Psiaki, M. 15 Shoemaker, M. 1 Nievinski, F. 11 Qian, Y. 6 Shupe, N. 5 Nishimoto, D. 19 Qian, Y. 18 Sibois, A. 14 No, T. 6 Ramey, H. 4 Siddarth, A. 27 Noomen, R. 3 Ranieri, C. 6 Skerritt, P. 3 Noomen, R. 25 Rao, A. 6 Sklyanskiy, E. 13 Novak, D. 9 Rao, A. 27 Smith, C. 2 O'Shaughnessy, D. 4 Revelin, B. 2 Song, Y. 8 O'Shaughnessy, D. 16 Riedel, J. 9 Spencer, D. 1 Ocampo, C. 17 Riedel, J. 13 Spencer, D. 19 Ogawa, N. 28 Roberts, C. 9 Spreen, C. 25 Oltrogge, D. 2 Robinson, S. 14 Springmann, J. 22 Oltrogge, D. 19 Roe, K. 8 Stanbridge, D. 16 Omran, A. 7 Rogers, A. 7 Stevenson, D. 18 Orlando, G. 25 Romano, M. 18 Strange, N. 5 Owen Jr., W. 9 Romano, M. 27 Strikwerda, T. 4 Owens, B. 12 Rosengren, A. 21 Strum, E. 13 Oyama, A. 25 Ross, I. 20 Stumpf, P. 14 Ozimek, M. 25 Rothenberg, J. 24 Sturtevant, S. 2 Page, B. 16 Russell, R. 3 Sweetser, T. 12 Palli, A. 13 Russell, R. 11 Sweetser, T. 13 Palmas, A. 17 Ryan, K. 22 Sydney, P. 19 Palmer, E. 15 Ryne, M. 13 Taheri, E. 17 Pan, B. 17 Sabol, C. 8 Takano, A. 15 Panomruttanarug, B. 20 Sagan, B. 25 Takeuchi, H. 11 Panosian, S. 26 Saiki, T. 9 Taylor, A. 16 Paris, S. 17 Saiki, T. 13 Terui, F. 28 Parish, J. 3 Saiki, T. 26 Teubert, C. 1 Parker, J. 3 Sajjadi-Kia, S. 14 Thakur, D. 20 Parker, J. 6 Sang, J. 2 Thompson, P. 9 Parker, J. 14 Satak, N. 27 Thornblom, M. 4 Parv, P. 5 Scarritt, S. 20 Tolson, R. 4 Patera, R. 18 Schaub, H. 7 Tortora, P. 11 Patterson, M. 27 Schaub, H. 10 Tortora, P. 13 Pavlak, T. 12 Schaub, H. 18 Tragesser, S. 26 Pel‡ez, J. 5 Schaub, H. 26 Trumbauer, E. 1 Pellegrini, V. 18 Scheeres, D. 3 Tsuda, Y. 9 Pena, X. 2 Scheeres, D. 5 Udrea, B. 1 Perez-Grande, I. 5 Scheeres, D. 13 Udrea, B. 5 Pernicka, H. 17 Scheeres, D. 19 Ueda, S. 28 Pernicka, H. 18 Scheeres, D. 21 Uematsu, H. 28 Peterson, G. 2 Scott, C. 16 Uetsuhara, M. 21 Petropoulos, A. 3 Scott, C. 25 Urrutxua, H. 5

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Author Session Valerino, P. 14 Vallado, D. 7 Vallado, D. 8 Vallado, D. 14 Vallado, D. 19 van Barneveld, L. 15 van der Weg, W. 5 Vaquero, M. 3 Vasile, M. 5 Vaughan, R. 16 Vellutini, E. 17 Villac, B. 1 Villac, B. 14 Villac, B. 15 Villac, B. 17 Villac, B. 27 Vincent, M. 13 Visser, P. 15 Wagner, S. 14 Wall, B. 9 Wang, D. 26 Wang, Z. 25 Wassom, S. 22 Wei, J. 6 Wei, W. 18 Weisman, R. 23 Wibben, D. 5 Wibben, D. 6 Wibben, D. 28 Wie, B. 1 Wie, B. 14 Wie, B. 20 Williams, B. 11 Williams, K. 11 Williams, K. 16 Williams, P. 19 Woodard, M. 12 Woodburn, J. 24 Woolley, R. 13 Wright, J. 23 Xin, M. 23 Xu, K. 20 Yamamoto, T. 20 Yin, J. 6 Yin, J. 10 Yin, J. 26 Yoo, B. 18 Yoshimura, Y. 20 You, T. 13 Zanetti, R. 28 Zavoli, A. 27 Zhao, X. 15

2011 AAS/AIAA Astrodynamics Specialist Conference, Girdwood, Alaska Page 73

PAPERS SORTED BY TIME SLOT

DAY 1: DATE TIME SESSION RM PAPE AUTHORS TITLE 1-Aug 08:00 1 Asteroid & NEO I A 400 Trumbauer Villac An Analysis of Multiple-Revolution Third Body Driven Plane Change Maneuvers 1-Aug 08:00 2 Orbital Debris I B 410 Jenkin 100-Year Low Earth Orbit Debris Population Model 1-Aug 08:00 3 Dynamical Systems Theory C 420 McMahon Scheeres A New Look at the Planar Dynamics of Libration-Orbit Coupling for Spacecraft 1-Aug 08:00 4 Autonomous Aerobraking K 473 Prince Murri Powell Autonomous Aerobraking: A Design, Development, and Feasibility Study 1-Aug 08:20 1 Asteroid & NEO I A 402 Shoemaker Hokamoto Application of Wide-Field Integration of Optic Flow to Proximity Operations and Landing for Space Exploration Mission 1-Aug 08:20 2 Orbital Debris I B 411 Bastida Virgili Krag Analyzing The Criteria For A Stable Environment 1-Aug 08:20 3 Dynamical Systems Theory C 421 Herman Born Davis et al Applications of trajectories in the vicinity of Sun-Earth L3 for a solar observation mission 1-Aug 08:20 4 Autonomous Aerobraking K 472 Skinner Maddock Autonomous Aerobraking Ephemeris Estimator 1-Aug 08:40 1 Asteroid & NEO I A 403 Kaplinger Wie Comparison of Fragmentation/Dispersion Models for Asteroid Nuclear Disruption Mission Design 1-Aug 08:40 2 Orbital Debris I B 412 McVey Chao Automated Ballistic Coefficient Estimation Technique to Analyze the Debris from the COSMOS-2251 and IRIDIUM-33 C 1-Aug 08:40 3 Dynamical Systems Theory C 423 Anderson Parker Comparison of Low-Energy Lunar Transfer Trajectories to Invariant Manifolds 1-Aug 08:40 4 Autonomous Aerobraking K 474 Dec Thornblom Autonomous Aerobraking: Thermal Analysis and Response Surface Development 1-Aug 09:00 1 Asteroid & NEO I A 404 Bellerose Dynamics and Stability in a Triple Asteroid System 1-Aug 09:00 2 Orbital Debris I B 413 Oltrogge Alfano Determination of Orbit Cross-Tag Events and Maneuvers With Orbit Detective 1-Aug 09:00 3 Dynamical Systems Theory C 424 Parish Hurtado Estimation Strategies for Dynamical Systems with Equality Constraints 1-Aug 09:00 4 Autonomous Aerobraking K 478 Justh Justus Ramey The Next Generation of Mars-GRAM and Its Role in the Autonomous Aerobraking Development Plan 1-Aug 09:20 1 Asteroid & NEO I A 405 Cersosimo Implementation of the NSTAR thruster to support Gravity-Tractor operations 1-Aug 09:20 2 Orbital Debris I B 414 Peterson Effect Of Future Space Debris On Mission Utility And Launch Accessibility 1-Aug 09:20 3 Dynamical Systems Theory C 425 Campagnola Russell Skerritt Flybys in the circular, restricted, three-body problem 1-Aug 09:20 4 Autonomous Aerobraking K 477 Tolson Prince Onboard Atmospheric Modeling and Prediction for Autonomous Aerobraking Missions 9:40 MORNING BREAK 1-Aug 10:10 1 Asteroid & NEO I A 406 Anderson Udrea Validation of a Finite Sphere Gravitation Model with Applications to Comet 67P/Churyumov-Gerasimenko 1-Aug 10:10 2 Orbital Debris I B 415 Chao Effects on Orbit Decay due to CO2 Growth in the Atmosphere 1-Aug 10:10 3 Dynamical Systems Theory C 426 Phan Celik Input-Output Identification of Discrete-Time Bilinear State-Space Models 1-Aug 10:10 4 Autonomous Aerobraking K 476 Maddock Bowes Dwyer Cia et al Implementation and Simulation Results Using Autonomous Aerobraking Development Software 1-Aug 10:30 1 Asteroid & NEO I A 408 Wie Pitz Teubert Earth-Impact Probability Computation of Disrupted Asteroid Fragments Using GMAT/STK/CODES 1-Aug 10:30 2 Orbital Debris I B 416 Oltrogge Kelso Getting to Know Our Space Population From the Public Catalog 1-Aug 10:30 3 Dynamical Systems Theory C 427 Grebow Petropoulos Multi-Body Capture to Low-Altitude Circular Orbits at Europa 1-Aug 10:30 4 Autonomous Aerobraking K 471 Kaidy Carrelli O'Shaughnet al Autonomous Aerobraking Algorithm Testing In Flight Software Simulation Environment 1-Aug 10:50 1 Asteroid & NEO I A 409 Spencer Polito The Probability of Asteroid-Earth Collisions by way of the Positional Uncertainty Ellipsoid 1-Aug 10:50 2 Orbital Debris I B 417 Smith Gao Greene et al Laser Tracking of Space Debris for Precision Orbit Determination 1-Aug 10:50 3 Dynamical Systems Theory C 428 Vaquero Howell Poincaré Maps and Resonant Orbits in the Restricted Three-Body Problem 1-Aug 11:10 2 Orbital Debris I B 418 Craychee Sturtevant Mitigating Potential Orbital Debris: The Deorbit of a Commercial Spacecraft 1-Aug 11:10 6 Trajectory Optimization I B 470 Selnick Furfaro Wibben Atmospheric Entry Guidance Via Multiple Sliding Surfaces Control For Mars Precision Landing 1-Aug 11:30 2 Orbital Debris I B 419 Dolado Garmier Legendre et al Satellite collision probability computation for long term encounters LUNCH 1-Aug 13:20 5 Asteroid & NEO II A 440 Peláez Bombardell Perez-Gra et al A new approach on the long term dynamics of NEO's under Yarkovsky effect 1-Aug 13:20 6 Trajectory Optimization I B 450 Ranieri Rao Hypersonic, Aerodynamically Controlled, Path Constrained Reentry Optimization Using Pseudospectral Methods 1-Aug 13:20 7 Formation Flying I C 460 Condurache A Closed Form Solution Of The Two Body Problem In Non-Inertial Reference Frame 1-Aug 13:20 8 Conjunction Assessment K 430 Plakalovic Frigm Hejduk et al A Tuned Single Parameter For Representing Conjunction Risk 1-Aug 13:40 5 Asteroid & NEO II A 441 Cupples Furfaro Hergenrothet al A Survey of Human-Precursor Robotic Asteroid Missions 1-Aug 13:40 6 Trajectory Optimization I B 451 Plice Craychee A Design Method for Low Altitude, Near-Equatorial Lunar Orbits 1-Aug 13:40 7 Formation Flying I C 462 Atchison Buckley Rogers An Operational Methodology for Large Scale Deployment of Nanosatellites into Low Earth Orbit 1-Aug 13:40 8 Conjunction Assessment K 431 Kim Kim Kim et al Analysis of Collision Avoidance Maneuver for COMS-1 satellite 1-Aug 14:00 5 Asteroid & NEO II A 444 Barbee Adamo Mink Methodology and Results of the Near-Earth Object (NEO) Human Space Flight (HSF) Accessible Targets Study (NHAT 1-Aug 14:00 6 Trajectory Optimization I B 452 Jesick Ocampo Ephemeris Model Optimization of Lunar Orbit Insertion From a Free Return Trajectory 1-Aug 14:00 7 Formation Flying I C 463 Di Mauro Di Lizia Lavangna Control Of Relative Motion Via State-Dependent Riccati Equation Technique 1-Aug 14:00 8 Conjunction Assessment K 432 Narvet Frigm Hejduk Assessment Of Uncertainty-Based Screening Volumes For Nasa Robotic Leo And Geo Conjunction Risk Assessment 1-Aug 14:20 5 Asteroid & NEO II A 443 Cupples Adebonojo Furfaro Launch Analysis Supporting Human-Precursor Robotic Asteroid Missions 1-Aug 14:20 6 Trajectory Optimization I B 453 Qian Hwang Jing et al New Dynamic Model For Lunar Probe And Its Application To Quasi-periodic Orbit About The Translunar Libration Poin 1-Aug 14:20 7 Formation Flying I C 464 Vallado Alfano Curvilinear Coordinates for Covariance and Relative Motion Operations 1-Aug 14:20 8 Conjunction Assessment K 433 Duncan Collision Avoidane in Near Real Time 1-Aug 14:40 5 Asteroid & NEO II A 445 van der Weg Vasile Mission Analysis and Transfer Design for the European Student Moon Orbiter 1-Aug 14:40 6 Trajectory Optimization I B 454 Carrico Carrico III Craychee et al Lunar-Resonant Trajectory Design For The Interstellar Boundary Explorer (IBEX) Extended Mission 1-Aug 14:40 7 Formation Flying I C 465 Schaub Jasper Effective Sphere Modeling For Electrostatic Forces On A Three-Dimensional Spacecraft Shape 1-Aug 14:40 8 Conjunction Assessment K 434 Finkleman Requirements and Guidance for Conjunction Assessment 15:00 AFTERNOON BREAK 1-Aug 15:30 5 Asteroid & NEO II A 446 Landau Strange Near-Earth Asteroids Accessible to Human Exploration with High-Power Electric Propulsion 1-Aug 15:30 6 Trajectory Optimization I B 455 No Jeon Lee et al Optimal Earth-Moon Transfer Trajectory Design Using Impulsive and Continuous Thrust 1-Aug 15:30 7 Formation Flying I C 466 Hogan Schaub Relative Motion Control for Two-Spacecraft Electrostatic Orbit Corrections 1-Aug 15:30 8 Conjunction Assessment K 435 Binz Alfriend Roe et al Estimating Probability of Collision Using High-Performance Computing and the Monte Carlo Method 1-Aug 15:50 5 Asteroid & NEO II A 447 Shupe Scheeres Orbit Options for an Orion-Class Spacecraft Mission to a Near-Earth Object 1-Aug 15:50 6 Trajectory Optimization I B 456 Mingotti Parametric Study of Earth-to-Moon Transfers with Hybrid Propulsion System with Dedicated Launch 1-Aug 15:50 7 Formation Flying I C 467 Omran Newman Nonlinear Analytical Solution Of Relative Motion Subject To J2 Perturbation Using Volterra Kernels 1-Aug 15:50 8 Conjunction Assessment K 436 Chan Intelsat Experience on Satellite Conjunctions and Lessons Learned 1-Aug 16:10 5 Asteroid & NEO II A 448 Phillips Parv Udrea Small-Body Gravity Field Approximation Methods 1-Aug 16:10 6 Trajectory Optimization I B 457 Luo Han Yin Research of the Free-Return Trajectories Between the Earth-Moon 1-Aug 16:10 7 Formation Flying I C 469 Hao Baojun Peng et al Two-Point Boundary Value Problem Of The Relative Motion 1-Aug 16:10 8 Conjunction Assessment K 437 Carpenter Alfriend Markley Sequential Probability Ratio Test for Collision Avoidance Maneuver Decisions Based on a Bank of Norm-Inequality-Co 1-Aug 16:30 5 Asteroid & NEO II A 449 Adamo Barbee Why Atens Enjoy Enhanced Accessibility For Human Space Flight 1-Aug 16:30 6 Trajectory Optimization I B 459 Parker Anderson Targeting Low-Energy Transfers to Low Lunar Orbit 1-Aug 16:30 8 Conjunction Assessment K 438 Alfano Toroidal Path Filter 1-Aug 16:50 8 Conjunction Assessment K 439 Vallado Verifying Observational for Real-world Space Situational Awareness END OF SESSIONS FOR DAY

Page 74 2011 AAS/AIAA Astrodynamics Specialist Conference, Girdwood, Alaska

DAY 2: DATE TIME SESSION RM PAPE AUTHORS TITLE 2-Aug 08:00 9 Non-Earth Orbiting Missions A 479 Wall Novak A 3D Shape-Based Approximation Method for Low-Thrust Trajectory Design 2-Aug 08:00 10 Formation Flying II B 489 Montenbruck Ardaens D'Amico et al Carrier Phase Differential GPS for LEO Formation Flying – The PRISMA and TanDEM-X Flight Experience 2-Aug 08:00 11 Orbit Estimation I C 499 Getzandanne Bauman Williams et al Advanced Navigation Strategies for an Asteroid Sample Return Mission 2-Aug 08:00 12 ARTEMIS Mission K 510 Folta Sweetser ARTEMIS Mission Overview: From Concept to Operations 2-Aug 08:20 9 Non-Earth Orbiting Missions A 480 Berry Comparisons Between Newton-Raphson and Broyden's Methods for Trajectory Design Problems 2-Aug 08:20 10 Formation Flying II B 490 Huang Fixed-Duration, Free Departure Time Satellite Formation Transfer Problem 2-Aug 08:20 11 Orbit Estimation I C 500 Villalba Born Evaluation of Linked Autonomous Interplanetary Satellite Orbit Navigation (LiAISON) in the Earth-Moon Regime Using 2-Aug 08:20 12 ARTEMIS Mission K 511 Folta Broschart Cosgrove et al Design and Implementation of the ARTEMIS Lunar Transfer Using Multi-body Dynamics 2-Aug 08:40 9 Non-Earth Orbiting Missions A 481 Mithra Canalias Carbonne End-to-end trajectory design for a chemical mission including multiple fly-by's of Jovian Trojan asteroids 2-Aug 08:40 10 Formation Flying II B 491 Bando Ichikawa Formation Flying Along a Circular Orbit with Control Constraints 2-Aug 08:40 11 Orbit Estimation I C 501 Arora Russell Fast, Efficient and Adaptive Interpolation of the Geopotential 2-Aug 08:40 12 ARTEMIS Mission K 515 Folta Cosgrove Woodard Station-keeping of the First Earth-Moon Libration Orbiters: the ARTEMIS Mission 2-Aug 09:00 9 Non-Earth Orbiting Missions A 486 Bhaskaran Abrahamso Chesley et al Navigation of the EPOXI Spacecraft to Comet Hartley 2 2-Aug 09:00 10 Formation Flying II B 492 Allgeier Erwin Fitz-Coy et al Metrics for Mission Planning of Formation Flight 2-Aug 09:00 11 Orbit Estimation I C 502 Leonard Born Nievinski Gravity Error Compensation Using Second-Order Gauss-Markov Processes 2-Aug 09:00 12 ARTEMIS Mission K 509 Broschart Angelopoul Folta et al ARTEMIS Lunar Orbit Insertion and Science Orbit Design through 2013 2-Aug 09:20 9 Non-Earth Orbiting Missions A 482 Chung Bhaskaran Chesley et al EPOXI Trajectory and Maneuver Analyses 2-Aug 09:20 10 Formation Flying II B 493 Heritier Howell Natural Regions Near The Sun-Earth Libration Points Suitable For Space Observations With Large Formations 2-Aug 09:20 11 Orbit Estimation I C 503 Llanos Hintz Miller Navigation Analysis for an L5 Mission in The Sun-Earth System 2-Aug 09:20 12 ARTEMIS Mission K 514 Woodard Cosgrove Folta et al Orbit Determination of Spacecraft in Earth-Moon L1 and L2 Libration Point Orbits 9:40 MORNING BREAK 2-Aug 10:10 9 Non-Earth Orbiting Missions A 483 Gillam Bhaskaran Chesley et al Ground Optical Navigation for the Stardust-NExT Mission to Comet 9P Tempel 1. 2-Aug 10:10 10 Formation Flying II B 495 Hess Decker Lovell Osculating Relative Orbit Elements Describing Relative Satellite Motion About an Eccentric Orbit 2-Aug 10:10 11 Orbit Estimation I C 505 Karimi Mortari Orbit Determination Based on Variations of Orbital Elements 2-Aug 10:10 12 ARTEMIS Mission K 516 Pavlak Howell Strategy for Long-Term Libration Point Orbit Stationkeeping in the Earth-Moon System 2-Aug 10:30 9 Non-Earth Orbiting Missions A 484 Haw Hayabusa: Navigation Challenges during Earth Return 2-Aug 10:30 10 Formation Flying II B 496 Hess Decker Lovell Osculating Relative Orbit Elements Describing Relative Satellite Motion with J2 Perturbations 2-Aug 10:30 11 Orbit Estimation I C 506 Ichikawa Aoshima Ishii et al Orbit Determination results of Akatsuki (Planet-C) Mission -Venus Climate Orbiter 2-Aug 10:30 12 ARTEMIS Mission K 513 Cheetham Born Folta et al Evaluating Orbit Determination Post-Processing Methods for Operational Artemis Data 2-Aug 10:50 9 Non-Earth Orbiting Missions A 485 Roberts Long Term Missions at the Sun-Earth Libration Point L1: ACE, SOHO, and WIND 2-Aug 10:50 10 Formation Flying II B 497 Yin Han Satellite Relative Motion in Elliptical Orbit Using Relative Orbit Elements 2-Aug 10:50 11 Orbit Estimation I C 507 Modenini Tortora Re-Examination of Pioneer 10 Tracking Data Including Spacecraft Thermal Modeling 2-Aug 11:10 9 Non-Earth Orbiting Missions A 487 Maruskin Bellerose Ma et al Particle levitation, trajectories, and mass transfer in the quasi-statically charged, planar circular restricted four body pro 2-Aug 11:10 10 Formation Flying II B 498 Schaub Jasper Circular Orbit Radius Control Using Electrostatic Actuation For 2-Craft Configurations 2-Aug 11:10 11 Orbit Estimation I C 508 Hwang Kim Kim et al Validation of COMS Satellite Orbit Determination Based on Single Station Antenna Tracking Data 2-Aug 11:30 9 Non-Earth Orbiting Missions A 488 Tsuda Funase Mimasu et al Sun-Earth Based Spin Axis Determination for Interplanetary Missions and Its Application to IKAROS LUNCH 2-Aug 13:20 13 Planetary Mission Studies A 517 Funase Chishiki Kawaguch et al Modeling and On-orbit Performance Evaluation of Propellant-free Attitude Control System for Spinning Solar Sail via O 2-Aug 13:20 14 Spacecraft GN&C B 527 Parker Hughes A General Event Location Algorithm with Applications to Eclipse and Station Line-Of-Sight 2-Aug 13:20 15 Satellite Constellations C 538 Marchand Biria Constellation Design for Space Based Situational Awareness Applications: An Analytical Approach 2-Aug 13:20 16 MESSENGER at Mercury K 546 McAdams Moessner O'Shaughnet al MESSENGER - Six Primary Maneuvers, Six Planetary Flybys, and 6.6 Years to Mercury Orbit 2-Aug 13:40 13 Planetary Mission Studies A 518 Boone Scheeres Evaluating Periodic Orbits for the JEO Mission at Europa in Terms of Estimation Metrics 2-Aug 13:40 14 Spacecraft GN&C B 528 Wagner Arrieta Ballard et al Cassini Solstice Mission Maneuver Experience: Year One 2-Aug 13:40 15 Satellite Constellations C 539 Liu Han Coverage Analysis of Specified Area for an Agile Earth Observation Satellite 2-Aug 13:40 16 MESSENGER at Mercury K 547 McAdams Moessner The MESSENGER Spacecraft's Orbit-Phase Trajectory 2-Aug 14:00 13 Planetary Mission Studies A 519 Woolley Mattingly Riedel et al Mars Sample Return - Launch and Detection Strategies for Orbital Rendezvous 2-Aug 14:00 14 Spacecraft GN&C B 529 Bradley Axelrad Sibois et al Earth Orientation Parameter Considerations for Precise Spacecraft Operations 2-Aug 14:00 15 Satellite Constellations C 540 Gunter Ditmar Encarnaçãet al Deriving global time-variable gravity from precise orbits of the Iridium NEXT constellation 2-Aug 14:00 16 MESSENGER at Mercury K 548 Stanbridge Bryan Dunham et al Achievable Force-Model Accuracies for MESSENGER While in Mercury Orbit 2-Aug 14:20 13 Planetary Mission Studies A 520 Ishimatsu de Weck Hoffman Mid-Course Plane-Change Trajectories Expanding Launch Windows for Mars Missions Including Venus Flyby Opportu 2-Aug 14:20 14 Spacecraft GN&C B 530 Ballard Arrieta Hahn et al Flight Path Control Design for the Cassini Solstice Mission 2-Aug 14:20 15 Satellite Constellations C 541 Hinks Psiaki Estimation of Atmospheric and Ionospheric Effects in Multi-Satellite Orbit Determination Using Crosslinks 2-Aug 14:20 16 MESSENGER at Mercury K 549 Page Bryan Flanigan et al Applying Experience from Mercury Encounters to MESSENGER's Mercury Orbital Mission Phase 2-Aug 14:40 13 Planetary Mission Studies A 521 Ryne Broschart Helfrich et al Navigation Support at JPL for the JAXA Akatsuki (Planet-C) Venus Orbiter Mission 2-Aug 14:40 14 Spacecraft GN&C B 531 Hawkins Guo Wie GNC Algorithm Design for Asteroid Intercept Missions with Precision Targeting Requirements 2-Aug 14:40 15 Satellite Constellations C 542 Chow Villac Numerical Continuation of Optimal Spacecraft Placements for LiAISON Constellations 2-Aug 14:40 16 MESSENGER at Mercury K 550 Flanigan Shaughnes Vaughan Guidance and Control of the MESSENGER Spacecraft in the Mercury Orbital Environment 15:00 AFTERNOON BREAK 2-Aug 15:30 13 Planetary Mission Studies A 522 Sklyanskiy Bowes Cheatwoodet al Passive Aerogravity Assisted Trajectories for Mars Atmospheric Sample Return Missions 2-Aug 15:30 14 Spacecraft GN&C B 532 Robinson Geller Moesser Guidance and Navigation Linear Covariance Analysis for Lunar Powered Decent 2-Aug 15:30 15 Satellite Constellations C 543 Marchand Takano Optimal Constellation Design for Space Based Situational Awareness Applications: A Numerical Approach 2-Aug 15:30 16 MESSENGER at Mercury K 551 Vaughan Flanigan Shaughne MESSENGER Spacecraft Pointing Performance during the Mission's Mercury Orbital Phase 2-Aug 15:50 13 Planetary Mission Studies A 523 Vincent Ely Sweetser Plans and Progress for Updating the Models used for Orbiter Lifetime Analysis 2-Aug 15:50 14 Spacecraft GN&C B 533 Alizadeh Sajjadi-Kia Villac Low-Thrust Adaptive Guidance Scheme Accounting For Engine Performance Degradation 2-Aug 15:50 15 Satellite Constellations C 544 Levi Palmer Strategy for Mitigating Collisions Between Landsat 5 and the Afternoon Constellation 2-Aug 15:50 16 MESSENGER at Mercury K 552 Scott Ercol McAdams et al Modeling the Effects of Albedo and Infrared Radiation Pressures on the MESSENGER Spacecraft 2-Aug 16:10 13 Planetary Mission Studies A 524 Palli Tortora Selection of Mercury's surface features coordinates for the BepiColombo Rotation Experiment 2-Aug 16:10 14 Spacecraft GN&C B 534 Lynam Longuski Preliminary Analysis for the Navigation of Multiple-satellite-aided Capture Sequences at Jupiter 2-Aug 16:10 15 Satellite Constellations C 545 Zhao Han Liu The Implementation Of MPI In The Autonomous Navigation Of Constellation 2-Aug 16:30 13 Planetary Mission Studies A 526 Boutonnet Boere Stationkeeping stragegy for Laplace-JGO science phase around Ganymede 2-Aug 16:30 14 Spacecraft GN&C B 535 Ely Chau Radar Altimetry and Velocimetry for Inertial Navigation: A Lunar Landing Example 2-Aug 16:50 13 Planetary Mission Studies A 525 Bannihatti Pa N.S N.V et al Stability Analysis of a Highly Eccentric Orbit Around Mars 2-Aug 16:50 14 Spacecraft GN&C B 536 Henderson Izzo Variable State Size Optimization Problems In Astrodynamics: N-Impulse Orbital Maneuvers END OF SESSIONS FOR DAY

2011 AAS/AIAA Astrodynamics Specialist Conference, Girdwood, Alaska Page 75

DAY 3: DATE TIME SESSION RM PAPE AUTHORS TITLE 3-Aug 08:00 17 Trajectory Optimization II A 553 Abilleira 2011 Mars Science Laboratory Launch Period Design 3-Aug 08:00 18 Attitude D&C I B 563 Kang Hwang Kim et al Attitude Motion of Spacecraft with Geometrically Distributed Multiple Liquid Stores 3-Aug 08:00 20 Spacecraft Autonomy K 583 Marchand Scarritt Application of Artificial Potential Function Methods to Autonomous Space Flight 3-Aug 08:20 17 Trajectory Optimization II A 555 Abdelkhalik Taheri Approximation of Constraint Low-Thrust Space Trajectories using Fourier Series 3-Aug 08:20 18 Attitude D&C I B 564 Patera Attitude Propagation for a Slewing Angular Rate Vector with Time Varying Slew Rate 3-Aug 08:20 19 Orbit Estimation II C 574 Fujimoto Scheeres Applications of the Admissible Region to Space-Based Observations 3-Aug 08:20 20 Spacecraft Autonomy K 584 Baldwin Lu Autonomous Optimal Deorbit Guidance 3-Aug 08:40 17 Trajectory Optimization II A 556 Senent Closed-form and numerically-stable solutions to problems related to the optimal two-impulse transfer between specified 3-Aug 08:40 18 Attitude D&C I B 565 Chesi Cristi Gong et al Automatic mass balancing for small Three-Axis spacecraft simulator using sliding masses only 3-Aug 08:40 19 Orbit Estimation II C 575 Spencer Erwin Williams Coupling of Nonlinear Estimation and Dynamic Sensor Tasking Applied to Space Situational Awareness 3-Aug 08:40 20 Spacecraft Autonomy K 585 Yamamoto Arikawa Itoh et al Autonomous Precision Orbit Control For Earth-Referenced Flight Path Repeat 3-Aug 09:00 17 Trajectory Optimization II A 557 Lu Chen Pan Coast Arcs in Optimal Multiburn Orbital Transfers 3-Aug 09:00 18 Attitude D&C I B 566 Ahn Kim Longman Evaluating the Robustness to Model Error of Multi-period Repetitive Control 3-Aug 09:00 19 Orbit Estimation II C 576 Hill Cortez Nishimoto et al Covariance-Driven Sensor Network Tasking for Diverse Space Objects 3-Aug 09:00 20 Spacecraft Autonomy K 586 Karpenko Bedrossian Bhatt et al Design and Flight Implementation of Operationally Relevant Time-Optimal Spacecraft Maneuvers 3-Aug 09:20 17 Trajectory Optimization II A 558 Avanzini Palmas Vellutini Implicit Solution for the Low-thrust Lambert Problem by Means of a Perturbative Expansion of Equinoctial Elements 3-Aug 09:20 18 Attitude D&C I B 567 Stevenson Schaub Nonlinear Control Analysis Of A Double Gimbal Variable Speed Control Moment Gyro 3-Aug 09:20 19 Orbit Estimation II C 578 Oltrogge Maneuver Event Detection and Reconstruction Using Body-Centric Acceleration/Jerk Optimization 3-Aug 09:20 20 Spacecraft Autonomy K 587 Longman Panomrutta Phan Designing Stable Iterative Learning Control Systems from Frequency Response Based Repetitive Control Designs 9:40 MORNING BREAK 3-Aug 10:10 17 Trajectory Optimization II A 559 Nakhjiri Villac Optimization of Stable MultiI-Impulse Transfers 3-Aug 10:10 18 Attitude D&C I B 568 de Angelis Avanzini Single-axis pointing of a magnetically actuated spacecraft: a non-nominal Euler axis approach 3-Aug 10:10 19 Orbit Estimation II C 579 Hoots Satellite Location Uncertainty Prediction 3-Aug 10:10 20 Spacecraft Autonomy K 588 Hawkins Guo Wie Optimal Feedback Guidance Algorithms for Asteroid Proximity Operations 3-Aug 10:30 17 Trajectory Optimization II A 560 Paris Trajectory Optimization Employing Direct Implicit Integration of 2nd Order Dynamical Systems and Non-Linear Program 3-Aug 10:30 18 Attitude D&C I B 569 Landau Ayoubi Longuski Solution of Spacecraft Attitude Via Angular Momentum in Body and Inertial Frames 3-Aug 10:30 19 Orbit Estimation II C 580 Vallado Griesbach Simulating Space Surveillance Networks 3-Aug 10:30 20 Spacecraft Autonomy K 589 Longman Juang Phan et al On Multi-Input Multi-Output Repetitive Control Design Methods 3-Aug 10:50 18 Attitude D&C I B 603 Dzamba Enright Fernando Star Tracker Only Attitude and Rate Estimation 3-Aug 10:50 19 Orbit Estimation II C 581 Hejduk Solar Radiation Pressure Binning for the Geosynchronous Orbit 3-Aug 10:50 20 Spacecraft Autonomy K 590 Yoshimura Hokamoto Matsuno Satellite Position And Attitude Control By On-Off Thrusters Considering Mass Change 3-Aug 11:10 17 Trajectory Optimization II A 562 Harl Pernicka Low-Thrust Control of Lunar Orbits 3-Aug 11:10 18 Attitude D&C I B 572 Searcy Pernicka Magnetometer-Only Attitude Determination Using Two-Step Kalman Filter 3-Aug 11:10 19 Orbit Estimation II C 582 DeMars Bishop Jah Space Object Tracking in the Presence of Attitude-Dependent Solar Radiation Pressure Effects 3-Aug 11:10 20 Spacecraft Autonomy K 591 Longman Li Shi Stabilizing Intersample Error in Iterative Learning Control Using Multiple Zero Order Holds Each Time Step 3-Aug 11:30 17 Trajectory Optimization II A 612 Scott Taylor Series Trajectory Calculations Including Oblateness Effects and Variable Atmospheric Density 3-Aug 11:30 18 Attitude D&C I B 571 Wei Jing Qian Attitude Control Of The Spacecraft With Swiveling Orbit Control Engine During The Propulsion 3-Aug 11:30 19 Orbit Estimation II C 570 Henderson Rogers System Identification Using Evolutionary Algorithms 3-Aug 11:30 20 Spacecraft Autonomy K 592 Marchand Thakur Tracking Control of Nanosatellites with Uncertain Time Varying Parameters LUNCH 3-Aug 13:20 21 Orbital Debris II A 593 Bénet Attitude Control and Orbital Dynamics Challenges of Decommissioning the First 3-Axis Stabilized Tracking and Data 3-Aug 13:20 22 Attitude D&C II B 598 Fullmer Jandak An Extended Kalman Smoother for the DICE Mission Attitude Determination Post Processing with Double Electrical Fie 3-Aug 13:20 23 Orbit Estimation III C 604 Weisman Alfriend Majji Application of the Transformation of Variables Technique for Uncertainty Mapping in Nonlinear Filtering 3-Aug 13:20 24 Space Environment K 609 Mehta McLaughlin Density and Ballistic Coefficient Estimation Revisited 3-Aug 13:40 21 Orbital Debris II A 594 Rosengren Scheeres Averaged Dynamics of HAMR Objects: Effects of Attitude and Earth Oblateness 3-Aug 13:40 22 Attitude D&C II B 599 Fullmer Ryan Wassom Experimental Testing of the Accuracy of Attitude Determination Solutions for a Spin-Stabilized Spacecraft 3-Aug 13:40 23 Orbit Estimation III C 605 Piepgrass Geller Computational Efficiency of a Hybrid Mass Concentration and Spherical Harmonic Modeling 3-Aug 13:40 24 Space Environment K 610 Woodburn Seago Global Atmospheric Density Esitmaton using a Sequential Filter/Smoother 3-Aug 14:00 21 Orbital Debris II A 595 Uetsuhara Hanada Kitazawa Effective Strategy to Identify Origins of Fragments from Breakups in GEO 3-Aug 14:00 22 Attitude D&C II B 600 Springmann Cutler Initial Attitude Analysis of the RAX Satellite 3-Aug 14:00 23 Orbit Estimation III C 606 DeMars Jah Evaluation of the Information Content of Observations with Application to Sensor Management for Orbit Determination 3-Aug 14:00 24 Space Environment K 611 Fanelli Gradeless Herrero et al Mini-satellite for Drag Estimation (MinDE): A Satellite as a Sensor System 3-Aug 14:20 21 Orbital Debris II A 596 Agapov KhutorovskyMolotov et al HAMR Space Debris in GEO - 6 years experience of tracking and analysis 3-Aug 14:20 23 Orbit Estimation III C 607 Wright QQ-Plot for Sequential Orbit Determination 3-Aug 14:20 24 Space Environment K 475 Mysore KrishnMcLaughlin Combining Precision Orbit Derived Density Estimates 3-Aug 14:40 21 Orbital Debris II A 597 Jenkin Uncertainty In Lifetime Of Highly Eccentric Transfer Orbits Due To Solar Resonances 3-Aug 14:40 22 Attitude D&C II B 602 McVittie Enright Spectral Star Tracker using Bayer Filter APS 3-Aug 14:40 23 Orbit Estimation III C 608 Cheng Jia Nevels et al Sparse Grid-Based Orbit Uncertainty Propagation 3-Aug 14:40 24 Space Environment K 613 McLaughlin Fattig Locke et al Time Periods of Anomalous Density for GRACE and CHAMP 15:00 AFTERNOON BREAK END OF SESSIONS FOR DAY DAY 4: DATE TIME SESSION RM PAPE AUTHORS TITLE 4-Aug 08:00 25 Trajectory Optimization III A 614 Wang A Linear Correction Approach For Precision Interplanetary Transfer Trajectory Design 4-Aug 08:00 26 Large Space Structures and TetheB 625 Tragesser Baars Analysis Of The Out-Of-Plane Dynamics Of A Tether Sling Stationed On A Rotating Body 4-Aug 08:00 27 Optimal Control C 634 Rao Francolin A Dynamic-Static Mesh Refinement Strategy for Solving Optimal Control Problems 4-Aug 08:00 28 Rendezvous K 644 Zanetti Clark A Comparison of Fixed-Terminal Direction Guidance Laws for Spacecraft Rendezvous 4-Aug 08:20 25 Trajectory Optimization III A 615 McGranaghanDove Emery et al A Survey of Mission Opportunities to Kuiper Belt Objects 4-Aug 08:20 26 Large Space Structures and TetheB 626 Jalali Mashay Misra Asteroid Diversion Using Tethers 4-Aug 08:20 27 Optimal Control C 635 Brown A Minimum Delta-V Orbit Maintenance Strategy for Low-Altitude Missions Using Burn Parameter Optimization 4-Aug 08:20 28 Rendezvous K 645 Lantoine Epenoy A Quadratically-Constrained LQR Approach for Finite-Thrust Orbital Rendezvous with Collision Avoidance 4-Aug 08:40 25 Trajectory Optimization III A 616 Oyama Hagiwara kawakatsu Application of Multiobjective Design Exploration to SOLAR-C Orbit Design 4-Aug 08:40 26 Large Space Structures and TetheB 627 Wang Jia Jin Attitude Controllability of an Underactuated Flexible Spacecraft 4-Aug 08:40 27 Optimal Control C 636 Rao Patterson A Modular MATLAB Software for Solving Multiple-Phase Optimal Control Problems 4-Aug 08:40 28 Rendezvous K 647 Furfaro Wibben Asteroid Precision Landing Via Multiple Sliding Surfaces Guidance Techniques 4-Aug 09:00 25 Trajectory Optimization III A 618 Wagner Wie GPU Accelerated Grid Search for Multiple Gravity-Assist and Impulsive Delta-V Maneuvers 4-Aug 09:00 26 Large Space Structures and TetheB 628 Liu Xu Backstepping Adaptive Control For Flexible Space Structure With Noncollocated Sensors And Actuators 4-Aug 09:00 27 Optimal Control C 637 Hosseini SianVillac An Exploration of the Optimum Two-Impulse Planar Transfers to Cyclers in the Earth-Moon System 4-Aug 09:00 28 Rendezvous K 649 Ueda Kasai Uematsu HTV Relative Approach Performance Evaluation Based On On-orbit Rendezvous Flight Result 4-Aug 09:20 25 Trajectory Optimization III A 619 Petropoulos Landau Interplanetary Trajectory Opportunities in the Decade 2018-2028 for the Jupiter Europa Orbiter Mission 4-Aug 09:20 26 Large Space Structures and TetheB 629 Iwata Fujii Matsumoto Deployment Dynamics of a Large Solar Array Paddle 4-Aug 09:20 27 Optimal Control C 639 Satak Cavalieri Hurtado et al Experimental Investigations of Trajectory Guidance and Control for Differential Games 4-Aug 09:20 28 Rendezvous K 650 Dannemiller Multi-Maneuver Clohessy-Wiltshire Targeting 9:40 MORNING BREAK 4-Aug 10:10 25 Trajectory Optimization III A 620 Abdelkhalik Multi-Gravity-Assist Trajectories Optimization: Comparison between the Hidden Genes and the Dynamic-Size Multiple 4-Aug 10:10 26 Large Space Structures and TetheB 630 Guerman Burov Kosenko Dynamics Of A Moon-Anchored Tether With Variable Length 4-Aug 10:10 27 Optimal Control C 640 Rao Patterson Exploiting Sparsity in Direct Collocation Pseudospectral Methods for Solving Optimal Control Problems 4-Aug 10:10 28 Rendezvous K 651 Pontani Conway Optimal Finite-Thrust Rendezvous Trajectories Found via Particle Swarm Algorithm 4-Aug 10:30 25 Trajectory Optimization III A 621 Orlando Mooij Noomen Orbital Stability around Planetary Satellites as Optimization Problem 4-Aug 10:30 26 Large Space Structures and TetheB 631 Avanzini Fedi Effects of J2 Perturbations on Multi-Tethered Satellite Formations 4-Aug 10:30 27 Optimal Control C 641 Colasurdo Casalino Francesco et al Optimal Cooperative Deployment of a Two-Satellite Formation into a Highly Elliptic Orbit 4-Aug 10:30 28 Rendezvous K 652 Boutonnet Arzel De Pasqua Out-of-Plane Post-Escape Strategy for the ATV 4-Aug 10:50 25 Trajectory Optimization III A 622 Scott Ozimek Optimal Transfer and Science Orbit Design in the Proximity of Small Bodies 4-Aug 10:50 26 Large Space Structures and TetheB 632 Seubert Panosian Schaub Analysis of a Tethered Coulomb Structure Applied to Close Proximity Situational Awareness 4-Aug 10:50 27 Optimal Control C 642 Sharma Hurtado Satak Optimal Nonlinear Feedback Control For Control Constraints Problems With Terminal Constraints: An SDRE Approach 4-Aug 10:50 28 Rendezvous K 653 Ogawa Kawaguchi Terui Precise Guidance and Landing Strategy of Space Probe by using Multiple Markers in Asteroid Exploration Mission 4-Aug 11:10 25 Trajectory Optimization III A 623 Spreen Longuski Trajectories to Uranus Using Gravity-Assists from Venus, Earth, Mars, Jupiter, and Saturn 4-Aug 11:10 26 Large Space Structures and TetheB 633 Mimasu Funase Kawaguch et al Orbit Control Method for Solar Sail Demonstrator IKAROS via Spin Rate Control 4-Aug 11:10 27 Optimal Control C 643 Ciarcia Romano Spacecraft Proximity Maneuver Guidance Based on Inverse Dynamic and Sequential Gradient-Restoration Algorithm END OF SESSIONS

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RECORD OF MEETING EXPENSES

AAS/AIAA Astrodynamics Specialist Conference July 31 - August 4, 2011 Girdwood, Alaska

Name:______Organization: ______

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Conference Proceedings (Hard Cover)1 ___ @ $360 $______

Extra CD Conference Proceedings1 ___ @ $45 $______

Special Event Ticket(s) $______

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1 Digital Proceedings on Compact Disk (CD) are provided after conference at no extra cost for full registrants 2011 AAS/AIAA Astrodynamics Specialist Conference, Girdwood, Alaska Page 77

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Page 78 2011 AAS/AIAA Astrodynamics Specialist Conference, Girdwood, Alaska

CONFERENCE SATISFACTION SURVEY The organizing committee welcomes your comments. Please fill out this questionnaire and return it to the registration desk or to a session chair. Thank you!

General Technical Content

 Please tell us if you registered as:  How satisfied were you regarding the overall technical content?  Student Retired Member Non-member   1 2 3 4 5  Please tell us if you think the conference was well Unsatisfied Satisfied organized.  How satisfied were you with the printed materials   received? Very Poorly Poorly Average Good Very Well    Please tell us if you think that the conference 1 2 3 4 5 information site was adequate in presenting all Unsatisfied Satisfied necessary information.  How do you feel about the publisher’s 20-page   limit on papers? Very Poor Poor Average Good Excellent   Approximately how many conference of this type Too Long Just Right Too Short Don’t Care do you attend annually?  How do you feel about having 72 hours before the   conference to download/print preprints? Maybe 1 1-2 3-4 4-5 >5   Where do you think our conference fee typically Too Long Just Right Too Short Don’t Care falls in terms of value?  How many presentations did you attend?   1 2 3 4 5   Unsatisfied Satisfied <10 10-20 21-30 31-40 >40 Registration  What meeting length ideally matches your ability to attend?  Overall, how satisfied were you with the online registration process?  <3 days 3 days 3.5 days 4 days   If your ideal meeting length cannot accommodate 1 2 3 4 5  all accepted papers, which do you prefer most? Unsatisfied Satisfied  Overall, how satisfied were you with the online     abstract/paper submission process? Increase Hold More Than Shorten Reject Meeting 3 Concurrent Presentation More   Length Sessions Length Papers 1 2 3 4 5 Unsatisfied Satisfied Social Events

 How much does the registration fee influence your  How satisfied were you with the receptions? decision or ability to regularly attend these conferences?   1 2 3 4 5   Unsatisfied Satisfied 1 2 3 4 5  How satisfied were you with the offsite event? Unsatisfied Satisfied   Venue 1 2 3 4 5  Overall, how satisfied were you with the Unsatisfied Satisfied conference location?  How do you feel about how many social events are   held? 1 2 3 4 5  Unsatisfied Satisfied Too Few Just Right Too Many Don’t Care

2011 AAS/AIAA Astrodynamics Specialist Conference, Girdwood, Alaska Page 79

Additional Survey Comments  General

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