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NASA NTRS1991

Mapping the stability field of Jupiter Trojans

Jupiter Trojans are a remnant of outer solar system planetesimals captured into stable or quasistable libration about the 1:1 resonance with the mean motion of Jupiter. The observed swarms of Trojans may provide insight into the original mass of condensed solids in the zone from which the Jovian planets accumulated, provided that the mechanisms of capture can be understood. As the first step toward this understanding, the stability field of Trojans were mapped in the coordinate proper eccentricity, e(sub p), and libration amplitude, D. To accomplish this mapping, the orbits of 100 particles with e(sub p) in the range of 0 to 0.8 and D in the range 0 to 140 deg were numerically integrated. Orbits of the Sun, the four Jovian planets, and the massless particles were integrated as a full N-body system, in a barycentric frame using fourth order symplectic scheme.

Levison, H. F.↗

NASA NTRS2003

Probable Disastrous Consequences of Collision Between Unknown Small (100 m) Asteroids with Known (Approximately 1 km) Near Earth Orbiting (NEO) Asteroids

The long-term stability of the Solar System is not well understood. Ironically its stability is taken for granted even though our knowledge of all the constituents [comets, asteroids. (The Asteroid Belt between Mars and Jupiter, Trojan Asteroids, Kuiper belt, Ort Cloud), planetoids, planets, moons, etc], and its long-term dynamics cannot be easily computed. At best one might say that the solar system is chaotic, but much of the time it seems to exists near a quasi-stationary state. An asteroid that passes near the Earth regularly returns with clock-like precision. Taking into account every known detail of its path through the solar system, its orbit is calculated forward thousands of years with no untoward calamity on the horizon. And then one day, this passive visitor slams into the Earth during a sunny afternoon picnic! Can this happen? Unfortunately, this is a real possibility in the ordinary history of the solar system. In fact our knowledge of the solar system in the small is sketchy, as will be pointed out. Events, which lie outside our awareness, can precipitate disasters that we may perceive when it's too late to launch effective counter measures. In this work, one such scenario is described and the direct consequences for the Earth are calculated.

Smalley, Larry↗

NASA NTRS1986

Spectroscopy of asteroids in unusual orbits

Medium-resolution spectroscopy of a collection of nonmain-belt asteroids has been obtained in order to search for possible cometlike spectral features. The asteroids include nine earth approachers, two Trojans, and the unusual object 2060 Chiron. All spectra were obtained and reduced in the same manner as comet data in the McDonald Observatory Faint Comet Survey. No indication of cometary activity was found in any of the asteroids observed.

Cochran, W. D.↗

NASA NTRS1993

NEP Early Flight program: System performance and development considerations

A mission/system study of Nuclear Electric Propulsion (NEP) for early robotic planetary science mission applications has been conducted. Subject missions considered included a Mars orbiter with a Phobos and Deimos Rendezvous; a Comet Kopff Rendezvous; a Multiple Mainbelt Asteroid Rendezvous (MMBAR); an Asteroid (Vesta) Sample Return; a Trojan Asteroid (Odysseus) Rendezvous; and a Jupiter mini Grand Tour. The purpose of the study was to determine if 'near-term' NEP technology could be used on an early NEP flight to demonstrate the technologies while conducting a useful science mission. The analysis shows that, depending upon technology readiness date, the missions could be performed with low power NEP. The technology and system development costs associated with vehicle/stage development for a candidate mission are presented. The study assumed relatively mature space electric power and space electric propulsion technologies (more advanced technologies have been already shown by others to be enabling for many outer planetary missions). Thus, a very important first step in using NEP would be taken, which would contribute valuable solar system science, as well as reduce the risks associated with using NEP for more demanding outer planetary science mission applications.

Doherty, Michael P.↗

NASA NTRS1991

Outer planets and icy satellites

The resources offered by the outer bodies in the Solar System, starting with the main belt asteroids and Jovian System, are not only larger and more diverse but may even be easier to reach than, say, those of Mars. The use of their material, including water and organic matter, depends exclusively on the general strategy of exploration of the Solar System. Of major interest in this respect are the large ice satellites - Titan, Ganymede, and Callisto. Motion through the planetary magnetospheres excites in their ice envelopes megampere currents which, in the presence of rocky, etc., inclusions with electronic conduction should lead to the bulk electrolysis of ice and accumulation in it of 2H2 + O2 in the form of a solid solution. With the concentration of 2H2 + O2 reaching about 15 wt. percent, the solution becomes capable of detonation by a strong meteoritic impact. An explosion of Ganymede's ice envelope about 0.5 By ago could account for the formation of the Trojans and irregular satellites, all known differences between Ganymede and Callisto, and many other things. The explosion of a small icy planet with M approx less than 0.5 Moon created the asteroid belt. Two to three explosions occurred on Io, and two on Europa. The specific features of the longperiod comets close to Saturn's orbit permit dating Titan's envelope explosion as 10,000 yr ago, which produced its thick atmosphere, young Saturn's rings, as well as a reservoir of ice fragments saturated by 2H2 + O2, i.e., cometary nuclei between the orbits of Jupiter and Saturn. Thus these nuclei should contain, besides organic matter, also 2H2 + O2, which could be used for their transportation as well as for fuel for spaceships. Ices of such composition can reside deep inside Deimos, the Trojans, C-asteroids, etc. The danger of a future explosion of Callisto's electrolyzed ices, which would result in a catastrophic bombardment of the Earth by comets, may be high enough to warrant a revision of the priorities and strategy of space exploration.

Drobyshevski, E. M.↗

NASA NTRS1979

Notes on the origin of the Trojan asteroids

The dynamic plausibility of various ideas on the origin of the Trojans is briefly discussed. We take the point of view that the present, tightly bound population has secularly evolved through some mechanism from less to more tightly bound orbit configurations. The mechanisms considered are changes in the Jovian mass or semimajor axis during planetary formation, collisional interactions with external, asteroidal material, and cometary outgassing.

Yoder, C. F.↗

NASA NTRS1991

Visual and near-IR spectrophotometry of asteroids

We have been continuing our studies of the spectral properties of dark asteroids in the solar system. From these studies we expect to learn about the distribution of volatile materials, such as water in clay materials (water of hydration) and how the asteroids may relate to the comets. Our most recent work has been concentrating on simultaneous visual and near infrared photometry near Earth, main belt, and trojan asteroids. We have made observations of some unusual asteroids such as Chiron, which has recently shown cometary activity, and 944 Hidalgo, which has a comet-like orbit. We have also begun studies of the small, dark satellites of Mars and Jupiter in order to understand better how they may relate to the steroids. Could they actually be captured asteroids or comets?

Lebofsky, Larry A.↗

NASA NTRS2018

Multi-Planetary Systems: Observations and Models of Dynamical Interactions

More than 600 multi-planet systems are known. The vast majority of these systems have been discovered by NASA's Kepler spacecraft, but dozens were found using the Doppler technique, the first multi-exoplanet system was identified through pulsar timing, and the most massive system has been found using imaging. More than one-third of the 4000+ planet candidates found by NASA's Kepler spacecraft are associated with target stars that have more than one planet candidate, and the large number of such Kepler "multis" tells us that flat multiplanet systems like our Solar System are common. Virtually all of Kepler candidate multis are stable, as tested by numerical integrations that assume a physically motivated mass-radius relationship. Statistical studies performed on these candidate systems reveal a great deal about the architecture of planetary systems, including the typical spacing of orbits and flatness. The characteristics of several of the most interesting confirmed multi-exoplanet systems will also be discussed.HR 8799's four massive planets orbit tens of AU from their host star and travel on nearly circular orbits. PSR B1257+12 has three much smaller planets orbiting close to a neutron star. Both represent extremes and show that planet formation is a robust process that produces a diversity of outcomes. Although both exomoons and Trojan (triangle Lagrange point) planets have been searched for, neither has yet been found.

planet candidates↗

NASA NTRS1990

A computer search for stable orbits between Jupiter and Saturn

The present experiment with test particles placed in orbits at uniform intervals between 5.7 and 8.8 AU, with randomly distributed eccentricities between 0.0 and 0.02 and inclinations between 0.0 and 0.063 rad, leads to the perception that no stable niches exist in the Jupiter-Saturn zone other than the Lagrangian points of Jupiter. These points are populated by at least 26 Trojan asteroids. The primary implication of these results for future investigations of the Saturn-Uranus-Neptune zone is that experimental design should be as selective as the dynamics of the planetary system have been shown to be.

Weibel, W. M.↗

DOE OSTI2023

Novel constraints on fifth forces and ultralight dark sector with asteroidal data

Here, we study for the first time the possibility of probing long-range fifth forces utilizing asteroid astrometric data, via the fifth force-induced orbital precession. We examine nine Near-Earth Object (NEO) asteroids whose orbital trajectories are accurately determined via optical and radar astrometry. Focusing on a Yukawa-type potential mediated by a new gauge field (dark photon) or a baryon-coupled scalar, we estimate the sensitivity reach for the fifth force coupling strength and mediator mass in the mass range m ≃ (10 -21 -10 -15 ) eV, near the "fuzzy" dark matter region. Our estimated sensitivity is comparable to leading limits from equivalence principle tests, potentially exceeding these in a specific mass range. The fifth force-induced precession increases with the orbital semi-major axis in the small m limit, motivating the study of objects further away from the Sun. We also demonstrate that precession tests are particularly strong in probing long-range forces which approximately conserve the equivalence principle. We discuss future prospects for extending our study to more than a million asteroids, including NEOs, main-belt asteroids, Hildas, and Jupiter Trojans, as well as trans-Neptunian objects and exoplanets.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

NASA NTRS2020

Detection of a Satellite of the Trojan Asteroid (3548) Eurybates – A Lucy Mission Target

We describe the discovery of a satellite of the Trojan asteroid (3548) Eurybates in images obtained with the Hubble Space Telescope. The satellite was detected on three separate epochs, two in September 2018 and one in January 2020. The satellite has a brightness in all three epochs consistent with an effective diameter of d2=1.2±0.4km. The projected separation from Eurybates was s~1700-2300 km and varied in position, consistent with a large range of possible orbits. Eurybates is a target of the Lucy Discovery mission and the early detection of a satellite provides an opportunity fora significant expansion of the scientific return from this encounter.

K. S. Noll↗

NASA NTRS1979

A special class of planetary collisions - Theory and evidence

Collisions between comparable-sized planetary bodies are a special class of collisions, rarer than other collisions, but producing interesting products, such as unfractured dumbbell-shaped contact binaries, partly brecciated elongated bodies, totally brecciated spheroidal bodies, and perhaps co-orbiting binary pairs or swarms. Qualitative and rough quantitative theories are presented to indicate collision outcomes. Contact binaries or fractured elongated bodies as large as tens or hundreds of kilometers across can be produced - larger than hitherto considered. Lengths about 20 to 200 km are most probable for igneous or ordinary chondritic elongated objects formed by collision, but other lengths could result from tidal evolution of pairs. Though most elongated asteroids are probably collision fragments, as usually assumed, some may instead be accretionary products. Trojan asteroid 624 Hektor is a candidate. Some polymict, genomict, and monomict brecciated meteorites may be better explained by large-scale fragmentation and immediate gravitational re-assembly of parent bodies than by local-scale processes of cratering on parent-body surfaces.

Hartmann, W. K.↗

NASA NTRS1988

Research in planetary astronomy and operation of the Mauna Kea Observatory

Spectroscopic studies with ground-based telescopes at low resolution can give compositional information of the surfaces and atmospheres of planets, satellites, asteroids, and comets. Solid state absorptions in ices and minerals are measurable by the low-resolution spectrophotometric technique. This program includes spectroscopy of distant comets, asteroids of particular interest in various contexts (planet crossers, outer main belt, trojans, etc.), Pluto and Charon, and planetary satellites of particular interest (Iapetus, Io, Uranian satellites, etc.). In the case of planets, satellites, and comets, emphasis is placed on volatiles (ices and organics), while for asteroids the stress is on mineralogy and the connection with the meteorites. New spectra show that the IR signature of Triton has changed since 1980, in that the methane bands are significantly weaker. Spectral evidence for the presence of molecular nitrogen remains convincing. Also, the brightness of Triton throughout its orbital cycle was measured to higher precision than before and was found to be constant to better than 0.02 mag. Suggestive spectral evidence was found for the presence of the C-H stretching mode band in diffuse reflection on asteroid 130 Elektra.

Cruikshank, Dale P.↗

NASA NTRS1983

Finding 'paydirt' on the moon and asteroids

Lunar polar region water ice, the Trojan asteroids of the earth, accessible, volatile substance-rich near-earth asteroids, and lunar gas deposits, are theoretically identified extraterrestrial resources for application to space transportation whose existence and economical exploitability could be confirmed by explorations conducted with relatively simple spacecraft. Any of these resources could improve the economics of interorbit transportation, thereby permitting launch vehicle payloads to be devoted to the transport of revenue-generating or services-providing equipment, rather than to the large propellant volumes required for the placing of large payloads on station. Among the verification missions cited is a simple lunar prospector orbiter, carrying a gamma-ray spectrometer and an electromagnetic sounder, which could ascertain the presence of water ice at the lunar poles.

Staehle, R. L.↗

NASA NTRS1977

Orbit-orbit resonances in the solar system - Varieties and similarities

Descriptions of various orbit-orbit resonance mechanisms in the solar system are brought together in such a manner that the physical processes underlying the traditional mathematical presentations are apparent. A simple qualitative model based on the resonance between Saturn's satellites Titan and Hyperion is presented, the same resonance is analyzed quantitatively, and the small-eccentricity mechanism is examined. The following resonances are investigated in detail: Enceladus-Dione, Mimas-Tethys, Neptune-Pluto, and Rhea-Titan (secular resonance). Coupled librations of several asteroids near mean motions commensurable with Jupiter's are modeled, the Laplace relation involving Io, Europa, and Ganymede is studied, and the 1:1 resonance between the Trojan asteroids and Jupiter is discussed. Some higher-order commensurabilities involving asteroids are considered, including the 3:1 resonance between Alinda and Jupiter, the 13:5 resonance of Toro with Venus, the 8:5 resonance of Toro with earth, and the 11:28 resonance of Ivar with earth.

Greenberg, R.↗

NASA NTRS1998

Solar System Studies with the Space Infrared Telescope Facility (SIRTF)

SIRTF (Space Infrared Telescope Facility) is the final element in NASA's 'Great Observatories' program. It consists of an 85-cm cryogenically-cooled observatory for infrared astronomy from space. SIRTF is scheduled for launch in late 2001 or early 2002 on a Delta rocket into a heliocentric orbit trailing the Earth. Data from SIRTF will be processed and disseminated to the community through the SIRTF Science Center (SSC) located at the Infrared Processing and Analysis Center (IPAC) at Caltech. Some 80/% of the total observing time (estimated at a minimum of 7500 hours of integration time per year for the mission lifetime of about 4 years) will be available to the scientific community at large through a system of refereed proposals. Three basic instruments are located in the SIRTF focal plane. The Multiband Imaging Photometer (MIPS), the Infrared Array Camera (IRAC), and the Infrared Spectrometer (IRS), taken together, provide imaging and spectroscopy from 3.5 to 160 microns. Among the solar system studies suited to SIRTF are the following: 1) spectroscopy and radiometry of small bodies from the asteroid main belt, through the Trojan clouds, to the Kuiper Disk; 2) dust distribution in the zodiacal cloud and the Earth's heliocentric dust ring; 3) spectroscopy and radiometry of comets; and 4) spectroscopy and radiometry of planets and their satellites. Searches for, and studies of dust disks around other stars, brown dwarfs, and superplanets will also be conducted with SIRTF. The SORTIE web site (http://ssc.ipac.caltech.edu/sirtf) contains important details and documentation on the project, the spacecraft, the telescope, instruments, and observing procedures. A community-wide workshop for solar system studies with SIRTF is in the planning stages by the author and Martha S. Hanner for the summer of 1999.

Cruikshank, Dale P.↗

NASA NTRSDate not supplied

Lucy Optical Navigation Performance During The (152830) Dinkinesh Encounter

The Lucy Jupiter-Trojan asteroid mission launched in November 2021. Its original mission concept included six small-body encounters over its 12-year primary mission. In the fall of 2022, an additional target of opportunity encounter was proposed to be executed in the fall of 2023. The encounter with (152830) Dinkinesh (previously 1999 VD57) presented myriad imaging, navigation, engineering, and planning challenges, as well as a chance to exercise and further refine the Optical NavigationSystem concept of operations, interfaces, and tools. Dinkinesh would be the smallest and dimmest target Lucy would encounter, with a higher uncertainty in these physical parameters than for other targets. While the Op Nav system and instruments carried a high amount of heritage from the New Horizons and OSIRIS-REx missions, this would be the first use of these systems on Lucy for navigation purposes. Despite these additional challenges, the Lucy Dinkinesh encounter was a resounding success throughout which the navigational system exceeded requirements.1Optical Navigation was successfully performed and fed into the orbit determination and trajectory maneuver activities up to the final knowledge update. The Dinkinesh encounter also proved to be greatly scientifically interesting, if not additionally challenging, as the Dinkinesh system was discovered to be a binary system through imaging during closest approach, and the secondary body was itself found to be a contact binary. This added complexity notwithstanding, the OpNav and OD teams were able to re-construct the close-approach trajectory of Dinkinesh in cooperation and concert with the Lucy Science Team’s shape modelling efforts.

Erik Lessac-Chenen↗

DOE OSTI2022

A Deep and Wide Twilight Survey for Asteroids Interior to Earth and Venus

We are conducting a survey using twilight time on the Dark Energy Camera with the Blanco 4 m telescope in Chile to look for objects interior to Earth's and Venus' orbits. To date we have discovered two rare Atira/Apohele asteroids, 2021 LJ4 and 2021 PH27, which have orbits completely interior to Earth's orbit. We also discovered one new Apollo-type Near Earth Object (NEO) that crosses Earth's orbit, 2022 AP7. Two of the discoveries have diameters ≳1 km. 2022 AP7 is likely the largest Potentially Hazardous Asteroid (PHA) discovered in about eight years. To date we have covered 624 square degrees of sky near to and interior to the orbit of Venus. The average images go to 21.3 mag in the r band, with the best images near 22nd mag. Our new discovery 2021 PH27 has the smallest semimajor axis known for an asteroid, 0.4617 au, and the largest general relativistic effects (53 arcsec/century) known for any body in the solar system. The survey has detected ~15% of all known Atira NEOs. We put strong constraints on any stable population of Venus co-orbital resonance objects existing, as well as the Atira and Vatira asteroid classes. These interior asteroid populations are important to complete the census of asteroids near Earth, including some of the most likely Earth impactors that cannot easily be discovered in other surveys. Comparing the actual population of asteroids found interior to Earth and Venus with those predicted to exist by extrapolating from the known population exterior to Earth is important to better understand the origin, composition, and structure of the NEO population.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗