I I I NEAR BARTH ASTEROID RETURNED SAMPLE MISSION I (NEARS) A. F. Cheng and S.R. Vernon* The Johns Hopkins University I Applied Physics Laboratory Laurel, Maryland 20723-6099 I I I I I I I I I I I I *Member, AIM I 1 I I I Abstract I NEARS is a small mission The NEARS mission will use to be proposed for the NASA a Delta II 7925 to launch in Discovery Program. It will January 2000 to the primitive I use a modified version of the (probably C-type) asteroid 4660 Near Earth Asteroid Rendezvous Nereus. Earth return occurs 4 spacecraft being developed by years later. The return the Johns Hopkins Applied capsule will use Pioneer Venus I Physics Laboratory. The NEARS heritage and will be supplied mission will return a set of by Martin Marietta Astrospace. samples from a near-Earth The pre-Phase A study of the I asteroid to Earth for analysis NEARS mission was supported by in terrestrial laboratories. the NASA Solar System NEARS will be the first sample Exploration Division. return from outside the We are currently I Earth-Moon system and will be a developing a sample acquisi tion pathfinder for future sample device that will be sui table returns from other small bodies for NEARS. This instrument I in the Solar System. NEARS development is supported by the will also be the first space NASA Planetary Instrument resource assessment beyond the Definition and Development I Moon and the first assessment Program. The sampler is a of the surface physical pyrotechnic device that will be properties of a small body. capable of obtaining a core With samples from a near-Earth sample from rock or regolith I asteroid, our laboratory surfaces. It does not require knowledge of materials from the spacecraft to tether itself specifically identified sources to the surface of the asteroid I will be extended beyond the and does not require a manned Moon to Earth's next nearest presence. The NEARS spacecraft neighbors. NEARS will will carry six of these establish the first detailed samplers, integrated with the I history for another body beyond return capsule, in a cluster the Earth and Moon and will be called the "six-shooter". We the decisive experiment for will present the NEARS mission I linking the fields of asteroid and spacecraft, the design and and meteorite science. test program for the sampler, and a systems integration and I packaging concept for the six-shooter. I I I 2 I I I

I Introduction preparation for the release of the first Discovery Mission AO. NEARS is a low cost planetary NEARS is a follow-on to the mission to be proposed to the NEAR mission (wi th which it I NASA Discovery Program. should not be confused; the S The Discovery Program will in NEARS stands for Sample) consist of small planetary that will return a set of bulk I missions costing no more than samples from a near-Earth $150 million to launch plus 30 asteroid to Earth for analysis days, in 1'Y92 dollars. The in terrestrial laboratories. I first two missions in the NEARS is the logical next step, Discovery Program are the Mars after NEAR, in the scientific Pathfinder and the Near Earth explora tion of primi tive bodies As teroid Rendezvous (NEAR) • in the inner solar system. I Both of these missions were started in PY94 and will launch NEARS Consortium in 1996. The third and I subsequent missions in the The NEARS mission will be Discovery Program will be performed by a consortium selected competitively via the involving uni versi ty, industry, I Announcemen t of Opportuni ty and government partners. The (AO) process. Principal Investigator will be Eugene Shoemaker, of the Lowell The Discovery Program is Observatory, and formerly of I modeled after the Explorer the u.S. Geological Survey. Program for astrophysics and The Johns Hopkins Universi ty space physics. It is intended Applied Physics Laboratory I to enable rapid response to (APL) will provide the emerging scientific spacecraft, which will be opportunities; to increase the designed, fabricated, and I breadth of activities in solar integrated at APL. APL will system exploration, to enhance also provide the sample timeliness of new information collection system for NEARS, return; to provide increased perform spacecraft integration I access to space; to expand and test, and carry out industrial, academic, and mission operations. The Earth public involvement in solar return capsule will be designed I system exploration missions; and fabricated by Martin and to facilitate cooperative Marietta Astrospace at Valley ventures with other space Porge, PA. Martin Marietta I agencies. Missions in the Astrospace provided the reentry Discovery Program will capsules for the Pioneer Venus emphasize focused science. mission as well as the Jupiter They will have rapid Probe Galileo • The NASA Deep I development cycles, < 36 Space Network will be used for months, and will use launch telecommunications, and the vehicles no larger than a Delta lunar sample facility at the I 2. NASA Johnson Space Center will be responsible for curation and The NEARS mission was one of 14 distribution of samples. I mission concepts funded by NASA for pre-phase A studies in I 3 I I

Science Rationale be extremely difficult to I establish clear relationships NEARS will be the first sample between specific meteorite return from outside the types and asteroid types on the I Earth-Moon system. It will basis of remote sensing of also be the first sample return asteroids. Only analysis of mission since the time of the asteroid samples in terrestrial Apollo missions. NEARS will be laboratories can definitively I a pathfinder for future robotic , . establish such a linkage, if in sample return missions and will fact any linkage exists. It is provide the first space quite possible that a returned I resource assessment from beyond asteroid sample will contain the Moon. With samples from a previously unknown material near Earth asteroid (NEA), our that is not currently I laboratory knowledge of represented in the meteorite extraterrestrial materials from collection. Any friable or specifically identified sources semi -volatile material on the will be extended beyond the surface of asteroids would most I Moon to Earth's next nearest likely not survive collisional neighbors. ejection from the asteroid and then hypersonic reentry through I The NEARS mission will return Earth's atmosphere, except in samples from multiple sites on the form of interplanetary dust an NEA and will lead to particles. I profound advances in our understanding of the early Mission Overview solar system and the processes and conditions leading to the NEARS will return to Earth I formation of the terrestrial samples of 10 to 100 grams each planets. NEARS will establish from four to six sites on a the first detailed history for near-Earth asteroid. It will I another body in the solar also perform a global sys tem beyond the Moon and wi 11 characterization of the be the decisive experiment for asteroid, including mass volume I linking the fields of asteroid and dens i ty determinations, and astronomy and meteorite it will study the geologic science. Meteorites are context of the sample sites. believed to be fragments of The obj ectives for NEARS are I asteroids, but it has proved to summarized in Table 1: I Table 1. Science Objectives

Provide the f'1I'St direct and detailed petrological, chemical, age, and isotopic I characterization of a near Earth asteroid. Relate the asteroidal material to terrestrial, lunar, and meteoric materials Sample the asteroid regolith and characterize any exotic fragments I Identify heterogeneity in the asteroid's isotopic properties, age, and elemental chemistry I

4 I I I I The prime target for the NEARS The prime launch opportuni ty mission will be the asteroid for NEARS occurs in January, I 4660 Nereus, which has been 2000 to the asteroid 4660 reported to be a primitive ... Nereus • The launch vehicle C-type asteroid. The type will be a Delta 11-7925. The I identification for Nereus is backup mission opportun i ty is a regarded as tentative, but it January 2002 launch to 4660 is established that Nereus is Nereus, which can be I not an S - type asteroid. The accomplished with an identical NEAR mission target, 433 Eros, flight system design. The is an S - type, as are the two trajectory for the January, target asteroids for the 2000 pr~e mission opportunity I Galileo flybys, 951 Gaspra and is plotted in Figure 1. Both 243 Ida. Our current knowledge of these are ballistic of Nereus is summarized in traj ectories to be performed I Table 2. using conventional bipropellant propulsion systems. We are Table 2. NEARS Target also studying electric I Nereus 4660 propulsion options that would use arcjet propulsion systems. I Figure 1. 2000 Launch (4660) Nereus I Type: C? (definitely not Type S) I.--=b DtIpIUt ~ Perihelion: 0.953 AU 1I1G111O 12fZ1J01 Cs-a.11cm'1a1 AV.550mIa ReIum Arrive.....,. I Aphelion: 2.03 AU 111'1104 10120/01 Inclination: 11.43° . 2AU I H Magnitude: 18.3 \ \ Size: 1-kmclass j I ! Rotation: Unknown " ,,' / "~" SImp" Relum I TI'IIjectory I I I 5 I Figure 2 sketches an overview sensor to signal contact with I of the NEARS mission. After the surface. The complete arrival at Uereus in October, sample collection system (the 2001, the spacecraft will Rsix-shooterR) will comprise execute a slow flyby of the four to six samplers and is I asteroid and then enter mounted, as a single unit, rendezvous orbit. A global wi thin the Earth return characterization of the capsule. Uo robotic I asteroid, including manipulator arm is required to determinations of the mass, transport samples into the density, shape, and spin state Earth return capsule. The I and a search for compositional landing phase will occupy heterogeneity, will be carried approximately the second month out. The sites for sample of the rendezvous with Uereus. collection will also be The spacecraft will touch down I selected during this orbital up to six times on the asteroid phase of the mission, which and obtain up to six samples will occupy approximately one from multiple sites. After each I month. touchdown, the spacecraft will re-establish orbit around the The landing phase of the asteroid and prepare for the I mission will then take place, next touchdown. NEARS will during which four to six include a Laser Al timeter to samples will be collected from assist in control of the various points on the asteroid. landings. I A Rtouch-and-goR sampling strategy will be used, in which After the landing phase the there is no long duration spacecraft will be boosted to I landing and contact with the an Earth return trajectory. surface is maintained for only Several hours before Earth a very short time, abou t a arrival, the return capsule I second. The sampler will be will be separated from the able to obtain samples from spacecraft. It will then either rock or regolith reenter through Earth's surfaces, using pyrotechnic atmosphere and descend on a I devices to fire core tubes into parachute to Earth's surface, the surface. Each sampler is a for land recovery. single shot device, and firing I is triggered by a proximity I I I I

6 I I I I Figure 2. Landing Scenario I I I NEARS MISSION OVERVIEW 2. LANDING PHASE

a. IARTH RETURN 2.. QUASI VERTICAL DESCENT I 1. ORBITAL SURVEY PHASE POINT FAN BEAM TO EARTH. 3.. SlPAIt4T1ON SAIO'LIR TO ASTDOID. :ea. OBORBIT D1JRN AND SUN WITHIN 70' or ruu. IIJ.UMINATION I T I I I ... ~ I (J I JOJ 30. LAND RICOVERY

20. TOUCH AND GO SAMPLING I NO LONG D'I1RATION LANDING, NO ROBOTIC MANIPULATOR ARM; OBTAIN TOTAL or SIX SAIO'LIS

POINT HIGH GAIN ANTENNA I TO EARTH INS1'RUMENTS TO ASTEROID. SUN WITHiN 70' or FULl. ILLlJIUNATION ---- I I I I I 7 I I

Mission Requirements particular, the maximum allowed I temperature of the samples The mission requirements are during reentry can be lODe, and summarized in Table 3. The the samples do not need to be I fundamental requirement is to kept in vacuum. A global return samples of 10 gram characterization of the minimum size from an asteroid asteroid is required during the surface. As the surface of an orbital phase. This will I asteroid is subjected to enhance the scientific tempera tures and condi tions interpretation of the asteroid comparable to those on the samples, and is also required I lunar surface, the asteroid for mission operations to samples can be handled like the ensure safe landings. lunar samples. In I I Table 3. NEARS Mission Requirements I -Sample multiple sites on an asteroid surface with a minimum sample size of 10 grams -Sample temperatures are not to exceed 100 C during reentry I -Obtain a global characterization of the asteroid, for sampling site selection and for establishing the geological context of sample sites I -Measurement of the target asteroid's mass, volume and density to within 10% I I I I I I I

8 I I I

I Strawman Instrument Payload not achieved because of a spacecraft failure; the The strawman payload is shown instruments were all in Table 4. In addition to the successful). One of the NEARS I sample collection system, Earth imagers will be a copy of the return capsule, and laser Clementine unit and will altimeter mentioned above, perform the global I NEARS will accommodate two characterization of the small imaging systems. These asteroid, including color unit will be copies or close mapping and site surveys. The I derivatives of the highly other imager will be slightly successful UV-Vis imager on modified to serve as a descent the Clementine mission, which imager to take close-up images was a Ballistic Missile Defense of the sample sites. I Organization (BlmO) mission that mapped the Moon (it was also planned to fly by an I asteroid, but this goal was Table 4. Strawman Payload I I Strawman Payload I Instrument Heritage Survey camera with filters BMDO - Clementine capable of lithologic discrimination flight spare unit I Descent Imager Clementine flight spare I Laser Altimeter NEAR LlDAR Sample Collector I Earth Return Capsule Pioneer Venus Probes I Radio Science Many missions I I I

I 9 I I I Spacecraft Summary minor modifications to the dual mode propulsion system used for The NEARS spacecraft will be NEAR. No change is required to I based on the NEAR spacecraft the following NEAR subsystems: design and will use many of the the power system, the telemetry same subsystems. Like NEAR, sys tem, the command and data I the NEARS spacecraft will be handling system, the guidance solar powered and three axfs 'and control system, and the stabilized, with both reaction attitude system. wheels and small thrusters I available for attitude control. Sampler Introduction The baseline design for NEARS will use a dual mode The NEARS Sample I bipropellant propulsion system collection system consists of (although an electric four to six independent propulsion option is under samplers packaged into a return study) with a spacecraft capsule. The intent of the I delta-v capability of 1475 m/s. design is to provide extremely The spacecraft will use X-band robust, simple mechanisms to telemetry to the NASA Deep minimize expensive testing and I Space Network. The maximum maximize flexibility as well as launch mass for NEARS is 792 redundancy. kg. I NEARS will involve the Sampler Design following modifications to the NEAR spacecraft design. The 60 Each Sampler will use a kg instrument payload on NEAR pyrotechnic charge to drive a I will be replaced with a hardened steel core tube into comparable mass payload on the surface to obtain a 10-100 NEARS that includes the sample gram sample depending on the I collection system, the Earth surface composition. A section return capsule, and the small view of the sampler in the Clementine-derived imaging "pre-fired" or launch systems. No robotic configuration is depicted in I manipulator arm is required for Figure 3. sample handling. As for spacecraft subsystems, the I baseline NEARS will require I ·1 I I 10 I I I I Figure 3. Layout of Sampler

I SHEAR PIN RETAINING RING

CORE TUBE I CAP OUTER HOUSING I I I I SHEAR RING '------TEFLON SEAL CAP I The teflon shear ring in surface be covered with a deep conjunction with the flange on layer of dust. Figure 4 depicts I the core tube act together to the sampler in the "fired" prevent the core tube from condi tion prior to retraction I exiting the housing should the into the re-entry capsule. Figure 4. Sampler in "Fired" Condition I I I I I I I 11 I I I Figure 7. Six-Shooter and Return Capsule Configuration (Cont.) I

Penetrator Retracted ______...., Cover Closed I I After firing, entire launcher (with penetrator extended) retracts Into the retum capsule I and a cover closea. I I I I Figure 8. I Six-Shooter and Return Capsule Configuration (Cont.) I Return capsule I I I I Alilauchera have been fired I 14 I I I

I Figure 9. I Six-Shooter and Return Capsule Configuration (Cont.) I I I I I I Configuration after separation

I Figure 10. Spacecraft Launch Configuration

I Instrument Deck Thruster Assembly I High Gain Antenna I Thruster

Capsule( I Penetrator Assembly I

I Solar Arrays (4) Shown Stowed I 1 Deleted for Clarity

I 15 I