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Daniel J Scheeres - One of the best experts on this subject based on the ideXlab platform.
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Temporarily Captured Asteroids as a Pathway to Affordable Asteroid Retrieval Missions
Journal of Guidance Control and Dynamics, 2015Co-Authors: Hodei Urrutxua, Daniel J Scheeres, Claudio Bombardelli, Juan Luis Gonzalo, Jesús PeláezAbstract:The population of “temporarily captured Asteroids” offers attractive candidates for asteroid retrieval missions. Once naturally captured, these Asteroids have lifetimes ranging from a few months up to several years in the vicinity of the Earth. One could potentially extend the duration of such temporary capture phases by acting upon the asteroid with slow deflection techniques that conveniently modify their trajectories, allowing for an affordable access and in situ study. In this paper, a case study on asteroid 2006 RH120 is presented, which was temporarily captured during 2006–2007 and is the single known member of this category to date. Simulations estimate that deflecting the asteroid with 0.27 N for less than six months and a change of velocity, ΔV of barely 32 m/s would have sufficed to extend the capture for over five additional years. The study is extended to another nine virtual Asteroids, showing that low-ΔV (less than 15 m/s) and low-thrust (less than 1 N) deflections initiated a few years in...
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the strength of regolith and rubble pile Asteroids
Meteoritics & Planetary Science, 2014Co-Authors: Paul Sanchez, Daniel J ScheeresAbstract:We explore the hypothesis that, due to small van der Waals forces between constituent grains, small rubble pile Asteroids have a small but non-zero cohesive strength. The nature of this model predicts that the cohesive strength should be constant independent of asteroid size, which creates a scale dependence with relative strength increasing as size decreases. This model counters classical theory that rubble pile Asteroids should behave as scale-independent cohesionless collections of rocks. We explore a simple model for asteroid strength that is based on these weak forces, validate it through granular mechanics simulations and comparisons with properties of lunar regolith, and then explore its implications and ability to explain and predict observed properties of small Asteroids in the NEA and Main Belt populations, and in particular of asteroid 2008 TC3. One conclusion is that the population of rapidly rotating Asteroids could consist of both distributions of smaller grains (i.e., rubble piles) and of monolithic boulders.
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The Fate of Asteroid Ejecta
2002Co-Authors: Daniel J Scheeres, Daniel D. Durda, Paul E. GeisslerAbstract:The distribution of regolith on asteroid surfaces has only recently been measured directly by in situ observations from spacecraft. To the surprise of many researchers, most of the classical predictions for the distribution of asteroid impact ejecta have not rung true, with regoliths appearing to be geologically active at small scales on asteroid surfaces. This indicates that significant insight into geological processes on Asteroids may be inferred by detailed studies of the distribution of impact ejecta on Asteroids. This chapter has been written to support these future investigations, by trying to identify and clarify all the important elements for such a study, to point to the recent history of such studies, and to indicate the current gaps in our understanding. The chapter begins with a discussion of the initial conditions of ejecta fields generated from impacts on the asteroid surface. Then the relevant physical laws and forces affecting asteroid ejecta, in orbit and on the surface, are reviewed and the basic dynamical equations of motion for ejecta are stated. Some general results and constraints on the solutions to these equations are given, and a classification scheme for ejecta trajectories is given. Finally, recent studies of asteroid ejecta are reviewed, showing the application of these techniques to asteroid science.
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solar sail orbit operations at Asteroids
Journal of Spacecraft and Rockets, 2001Co-Authors: Esther Morrow, Daniel J Scheeres, Dan LubinAbstract:The inherent capabilities of solar sails and the fact that they need no onboard supplies of fuel for propul- sion make them well suited for use in long-term, multiple-objective missions. They are especially well suited for the exploration of Asteroids, where one spacecraft could rendezvous with a number of aster- oids in succession. The orbital mechanics of solar sail operations about an asteroid, however, have not yet been studied in detail. Building on previous stud- ies that consider the equations of motion, we find both hovering points and orbiting trajectories about various sized Asteroids using equations of motion for a solar sail spacecraft. These hovering points are stabilizable using feedback control to sail attitude alone. The orbiting trajectories are stable and offer good coverage of the asteroid surface, although re- strictions on sail acceleration are needed for smaller Asteroids.
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dynamics about uniformly rotating triaxial ellipsoids applications to Asteroids
Icarus, 1994Co-Authors: Daniel J ScheeresAbstract:Abstract The general problem of satellite and particle dynamics about a uniformly rotating triaxial ellipsoid with constant density is formulated. The study of this problem can shed light on the dynamics of particles and satellites when orbiting irregularly shaped bodies such as Asteroids. The physical specification of an asteroid modeled as a triaxial ellipsoid can be reduced to two nondimensional shape parameters (the eccentricities of the triaxial ellipsoid) and one nondimensional parameter which is a function of the body density, shape, and rotation rate. All these parameters may be measured or inferred from groundbased observations. Using these three parameters, the rotating ellipsoid may be classified into Type I or Type II ellipsoids depending on whether or not all synchronous orbits about the body are unstable. This classification of the ellipsoid has significant consequences for the dynamics of bodies in orbits which are near-synchronous with the asteroid rotation. Asteroids classified as Type I have stable motion associated with near-synchronous orbits. Asteroids classified as Type II have unstable motion associated with near-synchronous orbits. Families of planar periodic orbits are computed for two specific ellipsoids based on the Asteroids Vesta and Eros. The stability of these families are computed and related to the type classification of the ellipsoid. Notes are also made on the existence of stable and unstable periodic orbits about the asteroid Ida. Analytic approximations are also introduced under some assumptions, leading to a simplified description of orbits about a triaxial ellipsoid. Finally, a table of parameters and classifications for a few known Asteroids and comets are given.
B Carry - One of the best experts on this subject based on the ideXlab platform.
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olivine dominated a type Asteroids in the main belt distribution abundance and relation to families
Icarus, 2019Co-Authors: Francesca E Demeo, Richard P. Binzel, D Polishook, B Carry, Brian Burt, Henry H Hsieh, Nicholas Moskovitz, T H BurbineAbstract:Abstract Differentiated Asteroids are rare in the main asteroid belt despite evidence for ∼ 100 distinct differentiated bodies in the meteorite record. We have sought to understand why so few main-belt Asteroids differentiated and where those differentiated bodies or fragments reside. Using the Sloan Digital Sky Survey (SDSS) to search for a needle in a haystack we identify spectral A-type asteroid candidates, olivine-dominated Asteroids that may represent mantle material of differentiated bodies. We have performed a near-infrared spectral survey with SpeX on the NASA IRTF and FIRE on the Magellan Telescope. We report results from having doubled the number of known A-type Asteroids. We deduce a new estimate for the overall abundance and distribution of this class of olivine-dominated Asteroids. We find A-type Asteroids account for less than 0.16% of all main-belt objects larger than 2 km and estimate there are a total of ∼ 600 A-type Asteroids above that size. They are found rather evenly distributed throughout the main belt, are even detected at the distance of the Cybele region, and have no statistically significant concentration in any asteroid family. We conclude the most likely implication is the few fragments of olivine-dominated material in the main belt did not form locally, but instead were implanted as collisional fragments of bodies that formed elsewhere.
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Solar System evolution from compositional mapping of the asteroid belt
Nature, 2014Co-Authors: F. E. Demeo, B CarryAbstract:Advances in the discovery and characterization of Asteroids over the past decade have revealed an unanticipated underlying structure that points to a dramatic early history of the inner Solar System. The Asteroids in the main asteroid belt have been discovered to be more compositionally diverse with size and distance from the Sun than had previously been known. This implies substantial mixing through processes such as planetary migration and the subsequent dynamical processes. The main asteroid belt, once regarded as a sort of dumping ground for the spent remnants of planet formation, has emerged in recent years as a region of dynamic activity that provides a window on the processes that are still shaping our Solar System and the many extrasolar planetary systems across the Universe. Francesca DeMeo and Benoit Carry review recent advances in the discovery and characterization of Asteroids. More than half a million Asteroids have been discovered and mapped since the 1980s, revealing remarkable diversity in size, composition and orbit. New evidence has demonstrated substantial mixing through planetary migration and the subsequent dynamical processes. Next year NASA's Dawn space probe is due to rendezvous with Ceres, the largest body in asteroid belt and one recently proven to contain water, so many new developments in this field can be expected. Unexpected diversity in the Asteroids in the main asteroid belt holds clues to mixing via planetary migration in the early Solar System.
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Asteroids physical models from combined dense and sparse photometry and scaling of the yorp effect by the observed obliquity distribution
Astronomy and Astrophysics, 2013Co-Authors: J Hanus, B Carry, J ďurech, M Brož, A Marciniak, Brian D Warner, Frederick Pilcher, Robert D Stephens, R Behrend, D CapekAbstract:The larger number of models of asteroid shapes and their rotational states derived by the lightcurve inversion give us better insight into both the nature of individual objects and the whole asteroid population. With a larger statistical sample we can study the physical properties of asteroid populations, such as main-belt Asteroids or individual asteroid families, in more detail. Shape models can also be used in combination with other types of observational data (IR, adaptive optics images, stellar occultations), e.g., to determine sizes and thermal properties. We use all available photometric data of Asteroids to derive their physical models by the lightcurve inversion method and compare the observed pole latitude distributions of all Asteroids with known convex shape models with the simulated pole latitude distributions. We used classical dense photometric lightcurves from several sources and sparse-in-time photometry from the U.S. Naval Observatory in Flagstaff, Catalina Sky Survey, and La Palma surveys (IAU codes 689, 703, 950) in the lightcurve inversion method to determine asteroid convex models and their rotational states. We also extended a simple dynamical model for the spin evolution of Asteroids used in our previous paper. We present 119 new asteroid models derived from combined dense and sparse-in-time photometry. We discuss the reliability of asteroid shape models derived only from Catalina Sky Survey data (IAU code 703) and present 20 such models. By using different values for a scaling parameter cYORP (corresponds to the magnitude of the YORP momentum) in the dynamical model for the spin evolution and by comparing synthetics and observed pole-latitude distributions, we were able to constrain the typical values of the cYORP parameter as between 0.05 and 0.6.
Hutao Cui - One of the best experts on this subject based on the ideXlab platform.
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Proposal for a multiple-asteroid-flyby mission with sample return
Advances in Space Research, 2012Co-Authors: Dong Qiao, Pingyuan Cui, Hutao CuiAbstract:Asteroid exploration provides a new approach to study the formation of the solar system and the planetary evolution. Choosing a suitable target and designing of feasible profile for asteroid mission are challenging due to constraints such as scientific value and technical feasibility. This paper investigates a feasible mission scenario among the potential candidates of multiple flybys and sample return missions. First, a group of potential candidates are selected by considering the physical properties and accessibility of Asteroids, for the sample return missions. Second, the feasible mission scenarios for multiple flybys and sample return missions to various spectral-type Asteroids are investigated. We present the optimized design of preliminary interplanetary transfer trajectory for two kinds of missions. One is the single sample return mission to Asteroids with various spectral types. The other is the multiple flybys and sample return mission to several Asteroids. In order to find the optimal profiles, the planetary swing-by technique and Differential Evolution algorithm are used. ?? 2012 COSPAR. Published by Elsevier Ltd. All rights reserved.
C. M. Hartzell - One of the best experts on this subject based on the ideXlab platform.
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Craters, boulders and regolith of (101955) Bennu indicative of an old and dynamic surface
Nature Geoscience, 2019Co-Authors: K. J. Walsh, R.-l. Ballouz, E. B. Bierhaus, H. C. Connolly, J. L. Molaro, M. Delbo’, Olivier S. Barnouin, Erica R. Jawin, T J Mccoy, C. M. HartzellAbstract:Small, kilometre-sized near-Earth Asteroids are expected to have young and frequently refreshed surfaces for two reasons: collisional disruptions are frequent in the main asteroid belt where they originate, and thermal or tidal processes act on them once they become near-Earth Asteroids. Here we present early measurements of numerous large candidate impact craters on near-Earth asteroid (101955) Bennu by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer) mission, which indicate a surface that is between 100 million and 1 billion years old, predating Bennu’s expected duration as a near-Earth asteroid. We also observe many fractured boulders, the morphology of which suggests an influence of impact or thermal processes over a considerable amount of time since the boulders were exposed at the surface. However, the surface also shows signs of more recent mass movement: clusters of boulders at topographic lows, a deficiency of small craters and infill of large craters. The oldest features likely record events from Bennu’s time in the main asteroid belt.Near-Earth rubble-pile asteroid Bennu has an unexpectedly old surface, with numerous candidate impact craters and morphologically diverse boulders, according to early observations by the OSIRIS-REx mission.
P. Finneran - One of the best experts on this subject based on the ideXlab platform.
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The OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS): Spectral Maps of the Asteroid Bennu
Space Science Reviews, 2018Co-Authors: D. C. Reuter, A. A. Simon, J. Hair, A. Lunsford, S. Manthripragada, C. Brambora, E. Caldwell, G. Casto, Z. Dolch, P. FinneranAbstract:The OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) is a point spectrometer covering the spectral range of 0.4 to 4.3 microns (25,000–2300 cm^−1). Its primary purpose is to map the surface composition of the asteroid Bennu, the target asteroid of the OSIRIS-REx asteroid sample return mission. The information it returns will help guide the selection of the sample site. It will also provide global context for the sample and high spatial resolution spectra that can be related to spatially unresolved terrestrial observations of Asteroids. It is a compact, low-mass (17.8 kg), power efficient (8.8 W average), and robust instrument with the sensitivity needed to detect a 5% spectral absorption feature on a very dark surface (3% reflectance) in the inner solar system (0.89–1.35 AU). It, in combination with the other instruments on the OSIRIS-REx Mission, will provide an unprecedented view of an asteroid’s surface.
