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Radar observations and shape model of asteroid 16 Psyche

Shepard, Michael K. and Richardson, James and Taylor, Patrick A. and Rodriguez-Ford, Linda A. and Conrad, Al and de Pater, Imke and Ádamkovics, Mate and de Kleer, Katherine and Males, Jared R. and Morzinski, Katie M. and Close, Laird M. and Kaasalainen, Mikko and Viikinkoski, Matti and Timerson, Bradley and Reddy, Vishnu and Magri, Christopher and Nolan, Michael C. and Howell, Ellen S. and Benner, Lance A. M. and Giorgini, Jon D. and Warner, Brian D. and Harris, Alan W. (2017) Radar observations and shape model of asteroid 16 Psyche. Icarus, 281 . pp. 388-403. ISSN 0019-1035. doi:10.1016/j.icarus.2016.08.011.

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Using the S-band radar at Arecibo Observatory, we observed 16 Psyche, the largest M-class asteroid in the main belt. We obtained 18 radar imaging and 6 continuous wave runs in November and December 2015, and combined these with 16 continuous wave runs from 2005 and 6 recent adaptive-optics (AO) images (Drummond et al., 2016) to generate a three-dimensional shape model of Psyche. Our model is consistent with a previously published AO image (Hanus et al., 2013) and three multi-chord occultations. Our shape model has dimensions 279 × 232 × 189 km (± 10%), D_(eff) = 226 ± 23 km, and is 6% larger than, but within the uncertainties of, the most recently published size and shape model generated from the inversion of lightcurves (Hanus et al., 2013). Psyche is roughly ellipsoidal but displays a mass-deficit over a region spanning 90° of longitude. There is also evidence for two ∼50–70 km wide depressions near its south pole. Our size and published masses lead to an overall bulk density estimate of 4500 ± 1400 kgm^(−3). Psyche's mean radar albedo of 0.37 ± 0.09 is consistent with a near-surface regolith composed largely of iron-nickel and ∼40% porosity. Its radar reflectivity varies by a factor of 1.6 as the asteroid rotates, suggesting global variations in metal abundance or bulk density in the near surface. The variations in radar albedo appear to correlate with large and small-scale shape features. Our size and Psyche's published absolute magnitude lead to an optical albedo of pv = 0.15 ± 0.03, and there is evidence for albedo variegations that correlate with shape features.

Item Type:Article
Related URLs:
URLURL TypeDescription
Shepard, Michael K.0000-0002-8441-2488
Conrad, Al0000-0003-2872-0061
de Pater, Imke0000-0002-4278-3168
de Kleer, Katherine0000-0002-9068-3428
Close, Laird M.0000-0002-2167-8246
Nolan, Michael C.0000-0001-8316-0680
Harris, Alan W.0000-0001-7431-2013
Additional Information:© 2016 Elsevier. Available online 12 August 2016. The Arecibo Observatory is operated by SRI International under a cooperative agreement with the National Science Foundation (AST-1100968), and in alliance with Ana G. Méndez-Universidad Metropolitana, and the Universities Space Research Association. The Arecibo Planetary Radar Program is supported by the National Aeronautics and Space Administration under Grant No. NNX12AF24G issued through the Near Earth Object Observations program. We thank the Arecibo operators and staff for their help in observing. Some of this work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This material is based in part upon work supported by the National Aeronautics and Space Administration (NASA) under the Science Mission Directorate Research and Analysis Programs. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This paper also includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. Funding for PDS observations, analysis, and publication was provided by NASA grant NNX13AP56G. Work on the asteroid lightcurve database (LCDB) was also funded in part by National Science Foundation grant AST-1507535.
Group:Astronomy Department
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:Asteroids; Asteroids Composition; Surfaces Asteroids; Radar
Record Number:CaltechAUTHORS:20190424-103201183
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Official Citation:Michael K. Shepard, James Richardson, Patrick A. Taylor, Linda A. Rodriguez-Ford, Al Conrad, Imke de Pater, Mate Adamkovics, Katherine de Kleer, Jared R. Males, Katie M. Morzinski, Laird M. Close, Mikko Kaasalainen, Matti Viikinkoski, Bradley Timerson, Vishnu Reddy, Christopher Magri, Michael C. Nolan, Ellen S. Howell, Lance A.M. Benner, Jon D. Giorgini, Brian D. Warner, Alan W. Harris, Radar observations and shape model of asteroid 16 Psyche, Icarus, Volume 281, 2017, Pages 388-403, ISSN 0019-1035, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94929
Deposited By: George Porter
Deposited On:24 Apr 2019 19:55
Last Modified:16 Nov 2021 17:08

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