DOCSLIB.ORG

The Effects of Orbital Precession on Remote Climate Monitoring

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Effects of Orbital Precession on Remote Climate Monitoring 4330 JOURNAL OF CLIMATE VOLUME 14 The Effects of Orbital Precession on Remote Climate Monitoring STEPHEN S. LEROY* Danish Meteorological Institute, Copenhagen, Denmark (Manuscript received 22 January 2001, in ®nal form 30 May 2001) ABSTRACT The effect of the diurnal cycle when monitoring the climate from low earth orbit is examined brie¯y. Equations are derived that relate the harmonics of the diurnal cycle to temporal sampling error and drift rates in that error. Special attention is given to nodal precession of satellite orbits. Using an insolated blackbody as a simple model for the diurnal cycle, roughly simulating subtropical desert surface temperature, the effects of orbital precession are examined numerically. From an initial con®guration, wherein satellites are evenly spaced in nodal crossing time, minor differences in precession rates lead to biases proportional to the amplitude of the semidiurnal cycle and inversely to the square root of the number of satellites. Overall biases for a single mission can be dramatically reduced by ¯ying in a formation wherein the satellites' orbits are evenly distributed in their equator-crossing times. To monitor surface temperature, it is suggested that at least six satellites be ¯own in formation and that their precession rates be controlled to well within 25 min. The tolerance for monitoring any other variable can be scaled according to the size of its semidiurnal cycle. 1. Introduction Oceanic and Atmospheric Administration weather sat- ellites, notably the Microwave Sounding Unit (MSU; Several organizations throughout the world are con- Spencer and Christy 1992a,b). Individual MSUs have templating placing instruments into low Earth orbit in been shown to measure hermispheric mean temperatures an attempt to monitor trends in the climate system. For with a precision of 0.01 K, but the accuracy of the MSU example, the European Organisation for the Exploitation measurements is not completely understood. In the fu- of Meteorological Satellites (Eumetsat) Polar System ture, the Metop and NPOESS series of satellites are will monitor the climate by means of a series of Me- expected to monitor the climate, and alternative, lower- teorological Operational (Metop) satellites, and the U.S. cost instruments also are being considered. (Goody et Interagency Program Of®ce (IPO) will implement the al. 1998). These alternatives are a constellation of or- National Polar-Orbiting Operational Environmental Sat- biting interferometers obtaining high-resolution infrared ellite System (NPOESS) series for similar purposes. The spectra and a constellation of orbiting global positioning tightest constraint on any climate observing system must system (GPS) receivers collecting occultations of the be that it can measure either very small climate trends atmosphere (Melbourne et al. 1994). Two constellations over the course of its lifetime or that it has negligible of GPS occultation receivers are being considered: the systematic bias so that it can be directly compared with Constellation Observing System for Meteorology, Ion- future measurements using the same technique. As an osphere, and Climate of Taiwan (Rocken et al. 2000), upper limit, it would be desireable to monitor the warm- and the Atmospheric Chemistry Explorer mission of the 21 ing of the climate, with an accuracy of ø0.01 K yr , European Space Agency (ESA) (Hoeg and Leppelmeier typical of model predictions (Kattenberg et al. 1996). 2000). In the past, many attempts to monitor trends in tro- Whenever one formulates a time series by averaging pospheric temperature were done with instruments in data derived from satellite measurements over short in- the Television Infrared Observational Satellite (TIROS) tervals of time, one must contend with the inability of Operational Vertical Sounder suite aboard the National that satellite to measure at all times of day at every location on the globe. In geostationary orbit, a tempo- * Permanent af®liation: Jet Propulsion Laboratory, California In- rally continuous dataset can be obtained, but spatial uni- stitute of Technology, Pasadena, California. formity cannot be obtained. Conversely, in low earth orbit (LEO), a satellite can obtain spatial uniformity but not a temporally uniform dataset. In the latter case, ev- Corresponding author address: Stephen S. Leroy, Danish Mete- orological Institute, Lyngbyvej 100, DK-2100 Copenhagen é, Den- ery position on the globe is sampled 2 times daily sep- mark. arated by almost exactly 12 h, once when the satellite E-mail: [email protected] is on the ascending branch of its orbit and then when q 2001 American Meteorological Society Unauthenticated | Downloaded 09/30/21 03:13 PM UTC 15 NOVEMBER 2001 LEROY 4331 solar time must be obtained to suppress sampling error due to the diurnal cycle. There are other effects related to the harmonics of the diurnal cycle that complicate the temporal sampling error. For one, even the 24-h-period ¯uctuations might contribute to sampling error biases and trends at high latitudes because in these regions the twice-daily sam- pling is not separated by exactly 12 h for sun-synchro- nous orbits, whose inclinations are typically 988. Fur- thermore, all odd-number harmonics of the diurnal cycle are expected to be removed by twice-daily sampling, but all even-numbered harmonics are expected to con- tribute to the temporal sampling error. Because the diurnal cycle as forced by insolation can be expected to be systematic over monthly timescales, the temporal sampling error of measurements by a sin- gle-LEO measuring system is examined given that the ¯uctuations are those due to a solar-forced diurnal cycle. Whether the sampling error can be suppressed if mul- tiple LEOs are used is also examined. Last, the effects FIG. 1. Plots of the hour displacement as a function of latitude for of both single LEO and multiple-LEO sampling systems various inclinations. A sun-synchronous orbit has an inclination of 98.28 corresponding to the solid curve. in con®gurations that precess even only slightly are ex- amined. Here the term ``climate monitoring'' refers to using satellite data as a kind of thermometer of the earth's the satellite is on its descending branch. With only these climate system. The equations presented here apply to measurements, when constructing a bias-free time series any geophysical scalar variable of the climate, mainly one would have to assume that temporal ¯uctuations those geophysical variables that are likely to contain a that occur exactly when the measurements are taken do signature of the diurnal forcing by solar insolation. Oth- not affect a long-term average of the measurements of ers have examined the sampling error in measurements that quantity. Fluctuations do occur, though, and dom- of outgoing longwave radiation (OLR) likely to be in- inant among systematic temporal ¯uctuations that might curred by single-satellite systems (Salby 1982a,b). A affect a twice-daily measuring system are those asso- geophysical variable whose diurnal signature strongly affects OLR is cloud cover (Bergman and Salby 1996). ciated with the diurnal cycle of the quantity being mea- Stratospheric trace species also have a strong diurnal sured. signature that hampers their monitoring by the Upper- A LEO can largely eliminate ¯uctuations that occur Atmosphere Research Satellite (Salby 1987). with a 24-h period, but it cannot eliminate ¯uctuations In this paper, an analytic formulation is given for that occur with a 12-h period. Because measurements translating a diurnal cycle into the biases it would pro- are separated by 12 h, the ¯uctuation from a true daily duce through temporal sampling error of an arbitrary mean of one observation is exactly the opposite of the multisatellite climate sampling system. This formulation ¯uctuation from a true daily mean of the other obser- can be applied to analyze the likely impacts of a diurnal vation, provided that its period is 24 h. If the ¯uctuation cycle in midtropospheric temperature in the MSU da- has a period of 12 h though, the ¯uctuation of the ®rst taset; however, this would require a season-long con- observation has the same sign as the ¯uctuation of the tinuous record of midtropospheric in situ temperature second observation; thus, the twice-daily cycle of the data at intervals of minutes, a project to be done in ¯uctuation adds a systematic bias onto the true climate another paper. In the next section, the formulation is mean, and this bias is a major component of the tem- applied to a simple model of the diurnal cycleÐthat of poral sampling error of this particular sampling pattern. surface temperature in a tropical desert regionÐand (In truth, temporal sampling error can also arise from compare the sampling error as produced by a single- undersampling cycles other than the diurnal cycle, but satellite system to that produced using a multisatellite in this paper only the diurnal cycle is directly ad- observing system. In the ®nal section, a summary and dressed.) The sampling error can also take the form of discussion of the implications of this work is given and a trend because of aliasing of the diurnal cycle by nodal recommendations for future climate monitoring exper- precession of satellites' orbits. Thus, because even the iments are made. most stable sun-synchronous orbits precess, the tem- poral sampling error can be exhibited as a trending bias 2. Formulation in any climate monitoring system. Should a multisatel- The most general con®guration assumed is m different lite system be used, however, enough coverage in local satellites in orbits with different inclinations, ascending Unauthenticated | Downloaded 09/30/21 03:13 PM UTC 4332 JOURNAL OF CLIMATE VOLUME 14 FIG. 2. Filter function for three evenly spaced orbits with inclination 98.28, time t 5 0. Squares indicate the real part of the ®lter and diamonds the imaginary part. The latitude is (a) 23.458N, (b) 66.558N. 2 nodes, and nodal precession rates.
Load more

Recommended publications
  • 6 Orbit Relative to the Sun. Crossing Times
    6 Orbit Relative to the Sun. Crossing Times We begin by studying the position of the orbit and ground track of an arbi- trary satellite relative to the direction of the Sun. We then turn more specif- ically to Sun-synchronous satellites for which this relative position provides the very definition of their orbit. 6.1 Cycle with Respect to the Sun 6.1.1 Crossing Time At a given time, it is useful to know the local time on the ground track, i.e., the LMT, deduced in a straightforward manner from the UT once the longitude of the place is given, using (4.49). The local mean time (LMT) on the ground track at this given time is called the crossing time or local crossing time. To obtain the local apparent time (LAT), one must know the day of the year to specify the equation of time ET. In all matters involving the position of the Sun (elevation and azimuth) relative to a local frame, this is the time that should be used. The ground track of the satellite can be represented by giving the crossing time. We have chosen to represent the LMT using colour on Colour Plates IIb, IIIb and VII to XI. For Sun-synchronous satellites such as MetOp-1, it is clear that the cross- ing time (in the ascending or descending direction) depends only on the latitude. At a given place (except near the poles), one crossing occurs during the day, the other at night. For the HEO of the Ellipso Borealis satellite, the stability of the crossing time also shows up clearly.
    [Show full text]
  • Some Special Types of Orbits Around Jupiter
    aerospace Article Some Special Types of Orbits around Jupiter Yongjie Liu 1, Yu Jiang 1,*, Hengnian Li 1,2,* and Hui Zhang 1 1 State Key Laboratory of Astronautic Dynamics, Xi’an Satellite Control Center, Xi’an 710043, China; [email protected] (Y.L.); [email protected] (H.Z.) 2 School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an 710049, China * Correspondence: [email protected] (Y.J.); [email protected] (H.L.) Abstract: This paper intends to show some special types of orbits around Jupiter based on the mean element theory, including stationary orbits, sun-synchronous orbits, orbits at the critical inclination, and repeating ground track orbits. A gravity model concerning only the perturbations of J2 and J4 terms is used here. Compared with special orbits around the Earth, the orbit dynamics differ greatly: (1) There do not exist longitude drifts on stationary orbits due to non-spherical gravity since only J2 and J4 terms are taken into account in the gravity model. All points on stationary orbits are degenerate equilibrium points. Moreover, the satellite will oscillate in the radial and North-South directions after a sufficiently small perturbation of stationary orbits. (2) The inclinations of sun-synchronous orbits are always bigger than 90 degrees, but smaller than those for satellites around the Earth. (3) The critical inclinations are no-longer independent of the semi-major axis and eccentricity of the orbits. The results show that if the eccentricity is small, the critical inclinations will decrease as the altitudes of orbits increase; if the eccentricity is larger, the critical inclinations will increase as the altitudes of orbits increase.
    [Show full text]
  • Tilting Saturn II. Numerical Model
    Tilting Saturn II. Numerical Model Douglas P. Hamilton Astronomy Department, University of Maryland College Park, MD 20742 [email protected] and William R. Ward Southwest Research Institute Boulder, CO 80303 [email protected] Received ; accepted Submitted to the Astronomical Journal, December 2003 Resubmitted to the Astronomical Journal, June 2004 – 2 – ABSTRACT We argue that the gas giants Jupiter and Saturn were both formed with their rotation axes nearly perpendicular to their orbital planes, and that the large cur- rent tilt of the ringed planet was acquired in a post formation event. We identify the responsible mechanism as trapping into a secular spin-orbit resonance which couples the angular momentum of Saturn’s rotation to that of Neptune’s orbit. Strong support for this model comes from i) a near match between the precession frequencies of Saturn’s pole and the orbital pole of Neptune and ii) the current directions that these poles point in space. We show, with direct numerical inte- grations, that trapping into the spin-orbit resonance and the associated growth in Saturn’s obliquity is not disrupted by other planetary perturbations. Subject headings: planets and satellites: individual (Saturn, Neptune) — Solar System: formation — Solar System: general 1. INTRODUCTION The formation of the Solar System is thought to have begun with a cold interstellar gas cloud that collapsed under its own self-gravity. Angular momentum was preserved during the process so that the young Sun was initially surrounded by the Solar Nebula, a spinning disk of gas and dust. From this disk, planets formed in a sequence of stages whose details are still not fully understood.
    [Show full text]
  • Orbital Dynamics and Numerical N-Body Simulations of Extrasolar Moons and Giant Planets
    ORBITAL DYNAMICS AND NUMERICAL N-BODY SIMULATIONS OF EXTRASOLAR MOONS AND GIANT PLANETS. A Dissertation Presented to the Faculty of the Graduate School of Cornell University in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy by Yu-Cian Hong August 2019 c 2019 Yu-Cian Hong ALL RIGHTS RESERVED ORBITAL DYNAMICS AND NUMERICAL N-BODY SIMULATIONS OF EXTRASOLAR MOONS AND GIANT PLANETS. Yu-Cian Hong, Ph.D. Cornell University 2019 This thesis work focuses on computational orbital dynamics of exomoons and exoplanets. Exomoons are highly sought-after astrobiological targets. Two can- didates have been discovered to-date (Bennett et al., 2014, Teachey & Kipping, 2018). We developed the first N-body integrator that can handle exomoon orbits in close planet-planet interactions, for the following three projects. (1) Instability of moons around non-oblate planets associated with slowed nodal precession and resonances with stars.This work reversed the commonsensical notion that spinning giant planets should be oblate. Moons around spherical planets were destabilized by 3:2 and 1:1 resonance overlap or the chaotic zone around 1:1 resonance between the orbital precession of the moons and the star. Normally, the torque from planet oblateness keeps the orbit of close-in moons precess fast ( period ∼ 7 yr for Io). Without planet oblateness, Io?s precession period is much longer (∼ 104 yr), which allowed resonance with the star, thus the in- stability. Therefore, realistic treatment of planet oblateness is critical in moon dynamics. (2) Orbital stability of moons in planet-planet scattering. Planet- planet scattering is the best model to date for explaining the eccentricity distri- bution of exoplanets.
    [Show full text]
  • Astro 250: Solutions to Problem Set 5 by Eugene Chiang
    Astro 250: Solutions to Problem Set 5 by Eugene Chiang Problem 1. Precessing Planes and the Invariable Plane Consider a star of mass mc orbited by two planets on nearly circular orbits. The mass and semi-major axis of the inner planet are m1 and a1, respectively, and those of the outer planet, m2 = (1/2) × m1 and a2 = 4 × a1. The mutual inclination between the two orbits is i 1. This problem explores the inclination and nodal behavior of the two planets. a) What is the inclination of each planet with respect to the invariable plane of the system? The invariable plane is perpendicular to the total (vector) angular momentum of all planetary orbits. Neglect the contribution of orbital eccentricity to the angular momentum. Call these inclinations i1 and i2. The masses and semi-major axes of the two planets are so chosen as to make the arithmetic easy;√ the norm of each planet’s angular momentum is the same as the other, |~l1| = |~l2| = m1 Gmca1. Orient the x-y axes in the invariable plane so that the y-axis lies along the line of intersection between the two orbit planes (the nodal line). Then in the x-z plane, the total angular momentum vector lies along the z-axis, while ~l1 lies (say) in quadrant II and makes an angle with respect to the z-axis of i1 > 0, while l~2 lies in quadrant I and makes an angle with respect to the z-axis of i2 > 0. Remember that the mutual inclination i = i1 + i2.
    [Show full text]
  • Retrograde-Rotating Exoplanets Experience Obliquity Excitations in an Eccentricity- Enabled Resonance
    The Planetary Science Journal, 1:8 (15pp), 2020 June https://doi.org/10.3847/PSJ/ab8198 © 2020. The Author(s). Published by the American Astronomical Society. Retrograde-rotating Exoplanets Experience Obliquity Excitations in an Eccentricity- enabled Resonance Steven M. Kreyche1 , Jason W. Barnes1 , Billy L. Quarles2 , Jack J. Lissauer3 , John E. Chambers4, and Matthew M. Hedman1 1 Department of Physics, University of Idaho, Moscow, ID, USA; [email protected] 2 Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA, USA 3 Space Science and Astrobiology Division, NASA Ames Research Center, Moffett Field, CA, USA 4 Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC, USA Received 2019 December 2; revised 2020 February 28; accepted 2020 March 18; published 2020 April 14 Abstract Previous studies have shown that planets that rotate retrograde (backward with respect to their orbital motion) generally experience less severe obliquity variations than those that rotate prograde (the same direction as their orbital motion). Here, we examine retrograde-rotating planets on eccentric orbits and find a previously unknown secular spin–orbit resonance that can drive significant obliquity variations. This resonance occurs when the frequency of the planet’s rotation axis precession becomes commensurate with an orbital eigenfrequency of the planetary system. The planet’s eccentricity enables a participating orbital frequency through an interaction in which the apsidal precession of the planet’s orbit causes a cyclic nutation of the planet’s orbital angular momentum vector. The resulting orbital frequency follows the relationship f =-W2v , where v and W are the rates of the planet’s changing longitude of periapsis and longitude of ascending node, respectively.
    [Show full text]
  • [Astro-Ph.EP] 3 Jul 2020 Positions of Ascending Nodes of the Orbits
    MNRAS 000,1{24 (2020) Preprint 7 July 2020 Compiled using MNRAS LATEX style file v3.0 Evidence for a high mutual inclination between the cold Jupiter and transiting super Earth orbiting π Men Jerry W. Xuan,? and Mark C. Wyatt Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK Accepted 2020 July 2. Received 2020 June 4; in original form 2020 April 1. ABSTRACT π Men hosts a transiting super Earth (P ≈ 6:27 d, m ≈ 4:82 M⊕, R ≈ 2:04 R⊕) discovered by TESS and a cold Jupiter (P ≈ 2093 d, m sin I ≈ 10:02 MJup, e ≈ 0:64) discovered from radial velocity. We use Gaia DR2 and Hipparcos astrometry to derive the star's velocity caused by the orbiting planets and constrain the cold Jupiter's sky- ◦ projected inclination (Ib = 41 − 65 ). From this we derive the mutual inclination (∆I) between the two planets, and find that 49◦ < ∆I < 131◦ (1σ), and 28◦ < ∆I < 152◦ (2σ). We examine the dynamics of the system using N-body simulations, and find that potentially large oscillations in the super Earth's eccentricity and inclination are suppressed by General Relativistic precession. However, nodal precession of the inner orbit around the invariable plane causes the super Earth to only transit between 7-22 per cent of the time, and to usually be observed as misaligned with the stellar spin axis. We repeat our analysis for HAT-P-11, finding a large ∆I between its close-in Neptune and cold Jupiter and similar dynamics. π Men and HAT-P-11 are prime examples of systems where dynamically hot outer planets excite their inner planets, with the effects of increasing planet eccentricities, planet-star misalignments, and potentially reducing the transit multiplicity.
    [Show full text]
  • Nodal Precession (Regression)
    National Aeronautics and Space Administration GDC Orbit Primer Michael Mesarch [email protected] October 10, 2018 c o d e 5 9 5 NAVIGATION & MISSION DESIGN BRANCH NASA GSFC www.nasa.gov Outline Orbital Elements Orbital Precession Differential Rates String of Pearls In-Plane Drift ΔV Calculations Orbital Decay Radiation Dosage NAVIGATION & MISSION DESIGN BRANCH, CODE 595 GDC Orbit Primer NASA GSFC October 10, 2018 2 Earth Orbital Elements Six elements are needed to specify an orbit state Semi-major Axis (SMA, a) Half the long-axis of the ellipse Perigee Radius (Rp) – closest approach to Earth Apogee Radius (Ra) – furthest distance from Earth SMA = (Rp + Ra)/2 Eccentricity (e) – ellipticity of the orbit e = 0 Circle 0 < e < 1 Ellipse e = 1 Parabola e = Ra/a -1 or e = 1 – Rp/a Inclination (i) Angle orbit makes to Earth equator Argument of Periapsis (ω) – angle in Angle between orbit normal vector and North Pole orbit plane from ascending node to Right Ascension of Ascending Node (Ω) perigee Angle in equatorial plane between Ascending Node True Anomaly (TA) – angle in orbit and Vernal Equinox plane from perigee to orbital location NAVIGATION & MISSION DESIGN BRANCH, CODE 595 GDC Orbit Primer NASA GSFC October 10, 2018 3 Nodal Precession (Regression) The Earth’s equatorial bulge imparts an out-of-plane force on the orbit which causes a gyroscopic precession of the line of nodes 2 푑Ω −3푛퐽2푅퐸푐표푠푖 rad/sec 푑푡 2푎2(1−푒2)2 where Polar orbits have no nodal precession R – Earth Radius When nodal precession is equal to
    [Show full text]
  • Dynamics and Control of Spacecraft Formations: Challenges and Some Solutions Journal of the Astronautical Sciences
    Dynamics and Control of Spacecraft Formations: Challenges and Some Solutions Kyle T. Alfriend and Hanspeter Schaub Simulated Reprint from Journal of the Astronautical Sciences Vol. 48, No. 2, April–Sept., 2000, Pages 249-267 A publication of the American Astronautical Society AAS Publications Office P.O. Box 28130 San Diego, CA 92198 Journal of the Astronautical Sciences Vol. 48, No. 2, April–Sept., 2000, Pages 249-267 Dynamics and Control of Spacecraft Formations: Challenges and Some Solutions Kyle T. Alfriend ∗ and Hanspeter Schaub † Abstract Presented is an analytic method to establish J2 invariant relative orbits, that is, relative orbit motions that do not drift apart. Working with mean orbit elements, the secular relative drift of the longitude of the ascending node and the argument of latitude are set equal between two neighboring orbits. Two first order conditions constrain the differences between the chief and deputy momenta elements (semi-major axis, eccentricity and inclination angle), while the other three angular differences (ascending node, argument of perigee and mean anomaly), can be chosen at will. Several challenges in designing such relative orbits are discussed. For near polar orbits or near circular orbits enforcing the equal nodal rate condition may result in impractically large relative orbits if a difference in inclination angle is prescribed. In the latter case, compensating for a difference in inclination angle becomes exceedingly difficult as the eccentricity approaches zero. The third issue discussed is the relative argument of perigee and mean anomaly drift. While this drift has little or no effect on the relative orbit geometry for small or near-zero eccentricities, for larger eccentricities it causes the relative orbit to enlarge and contract over time.
    [Show full text]
  • Formation and Evolution of Planetary Systems in Presence of Highly Inclined Stellar Perturbers Konstantin Batygin1,2, Alessandro Morbidelli1, and Kleomenis Tsiganis3
    Astronomy & Astrophysics manuscript no. ms c ESO 2018 October 29, 2018 Formation and Evolution of Planetary Systems in Presence of Highly Inclined Stellar Perturbers Konstantin Batygin1;2, Alessandro Morbidelli1, and Kleomenis Tsiganis3 1 Departement Cassiopee:´ Universite de Nice-Sophia Antipolis, Observatoire de la Coteˆ dAzur, 06304 Nice, France 2 Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 3 Section of Astrophysics, Astronomy & Mechanics, Department of Phyiscs, Aristotle University of Thessaloniki, GR 54 124 Thessaloniki, Greece Preprint online version: October 29, 2018 ABSTRACT Context. The presence of highly eccentric extrasolar planets in binary stellar systems suggests that the Kozai effect has played an important role in shaping their dynamical architectures. However, the formation of planets in inclined binary systems poses a con- siderable theoretical challenge, as orbital excitation due to the Kozai resonance implies destructive, high-velocity collisions among planetesimals. Aims. To resolve the apparent difficulties posed by Kozai resonance, we seek to identify the primary physical processes responsible for inhibiting the action of Kozai cycles in protoplanetary disks. Subsequently, we seek to understand how newly-formed planetary systems transition to their observed, Kozai-dominated dynamical states. Methods. The main focus of this study is on understanding the important mechanisms at play. Thus, we rely primarily on analytical perturbation theory in our calculations. Where the analytical approach fails to suffice, we perform numerical N-body experiments. Results. We find that theoretical difficulties in planet formation arising from the presence of a distant (˜a ∼ 1000AU) companion star, posed by the Kozai effect and other secular perturbations, can be overcome by a proper account of gravitational interactions within the protoplanetary disk.
    [Show full text]
  • Valuation of On-Orbit Servicing in Proliferated Low-Earth Orbit Constellations
    Valuation of On-Orbit Servicing in Proliferated Low-Earth Orbit Constellations The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation Luu, Michael and Daniel E. Hastings. "Valuation of On-Orbit Servicing in Proliferated Low-Earth Orbit Constellations." Accelerating Space Commerce, Exploration, and New Discovery Conference, November 2020, virtual event, American Institute of Aeronautics and Astronautics, November 2020. © 2020 Michael Luu and Daniel Hastings As Published http://dx.doi.org/10.2514/6.2020-4127 Publisher American Institute of Aeronautics and Astronautics Version Author's final manuscript Citable link https://hdl.handle.net/1721.1/130620 Terms of Use Creative Commons Attribution-Noncommercial-Share Alike Detailed Terms http://creativecommons.org/licenses/by-nc-sa/4.0/ Valuation of On-Orbit Servicing in Proliferated Low-Earth Orbit Constellations Michael A. Luu1 and Daniel E. Hastings2 Massachusetts Institute of Technology, Cambridge, MA, 02139, United States On-orbit servicing (OOS) presents new opportunities for refueling, inspection, repair, maintenance, and upgrade of spacecraft (s/c). OOS is a significant area of need for future space growth, enabled by the maturation of technology and the economic prospects. This congestion is leading s/c operators to explore how they can leverage OOS. OOS missions for s/c in geostationary orbit (GEO) are currently underway. This is being driven by the closure of the business case for refueling long lived monolithic chemically propelled GEO assets. However, there are currently no plans for OOS of low-earth orbit (LEO) s/c, aside from technology demonstrations, because of their shorter design life and lower cost.
    [Show full text]
  • Investigation of Satellite Constellation Configuration for Earth Observation Using Sierra Nevada Dream Chaser® Spacecraft
    Investigation of Satellite Constellation Configuration for Earth Observation Using Sierra Nevada Dream Chaser® Spacecraft Undergraduate Thesis Presented in Partial Fulfillment of the Requirements for Graduation with Research Distinction from the Department of Mechanical and Aerospace Engineering The Ohio State University Spring, 2018 Author Andrew John Steen Defense Committee Dr. John M. Horack [Advisor] Dr. Datta V. Gaitonde i ii Abstract As the global climate crisis continues to drive extreme weather conditions, the need for increasingly robust systems to deliver unprecedented Earth Observation (EO) data will become a major economic concern for nations worldwide. The need exists for an international open platform for EO that can be utilized by small, less economically or technologically advanced nations for data acquisition as they attempt to deal with environmental disasters. The purpose of this project is therefore to develop an orbital strategy for the construction and utilization of an EO constellation of satellites, using as its platform the Sierra Nevada Corporation’s Dream Chaser® spacecraft after its supply missions are completed at the International Space Station. In this paper I summarize the current international access to highly temporally, spectrally, and spatially precise EO for close to real-time disaster response and the apparent lack thereof, I introduce the benefits of a collaborative and dynamic international platform under the initial context of a fleet of Dream Chaser orbital platforms, and detail the orbital mechanics theory and approach to enabling passively and actively responsive EO for the chosen relevant case study of the South East-Asian region. Initial results indicate that such a system could enable needed disaster response efforts from space in regions of the world with the least access to them but the highest need for them due to the onslaught of extreme weather patterns created by global climate change.
    [Show full text]