Goldstone and Arecibo radar observations of (99942) Apophis in 2012-2013

被引：54

作者：

Brozovic, Marina ^{[1
]}

Benner, Lance A. M. ^{[1
]}

McMichael, Joseph G. ^{[1
]}

Giorgini, Jon D. ^{[1
]}

Pravec, Petr ^{[2
]}

Scheirich, Petr ^{[2
]}

Magri, Christopher ^{[3
]}

Busch, Michael W. ^{[4
]}

Jao, Joseph S. ^{[1
]}

Lee, Clement G. ^{[1
]}

Snedeker, Lawrence G. ^{[5
]}

Silva, Marc A. ^{[5
]}

Slade, Martin A. ^{[1
]}

Semenov, Boris ^{[1
]}

Nolan, Michael C. ^{[6
]}

Taylor, Patrick A. ^{[7
]}

Howell, Ellen S. ^{[6
]}

Lawrence, Kenneth J. ^{[1
]}

机构：

[1] CALTECH, Jet Prop Lab, 4800 Oak Grove Dr,Mail Stop 301-121, Pasadena, CA 91109 USA

[2] Acad Sci Czech Republ, Astron Inst, Prague, Czech Republic

[3] Univ Maine Farmington, Preble Hall, Farmington, ME 04938 USA

[4] SETI Inst, Mountain View, CA 94043 USA

[5] SAITECH, Goldstone Deep Space Commun Complex, Ft Irwin, CA 92310 USA

[6] Univ Arizona, Tucson, AZ 85721 USA

[7] Univ Space Res Assoc, Arecibo Observ, Arecibo, PR 00612 USA

来源：

ICARUS | 2018年 / 300卷

基金：

美国国家航空航天局;

关键词：

EARTH ENCOUNTERS; SPIN-STATE; ASTEROIDS; ALBEDO; MODEL; SHAPE;

D O I：

10.1016/j.icarus.2017.08.032

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

We report radar observations of Apophis obtained during the 2012-2013 apparition. We observed Apophis on fourteen days at Goldstone (8560 MHz, 3.5 cm) and on five days at Arecibo (2380 MHz, 12.3 cm) between 2012 December 21 to 2013 March 16. Closest approach occurred on January 9 at a distance of 0.097 au. We obtained relatively weak echo power spectra and delay-Doppler images. The highest range resolution was achieved at Goldstone, 0.125 mu s or similar to 20 m/px. The data suggest that Apophis is an elongated, asymmetric, and possibly bifurcated object. The images place a lower bound on the long axis of 450 m. We used the Pravec et al. (2014) lightcurve-derived shape and spin state model of Apophis to test for short axis mode (SAM) non-principal axis rotation (NPA) and to estimate the asteroid's dimensions. The radar data are consistent with the NPA spin state and they constrain the equivalent diameter to be D = 0.34 +/- 0.04 km (1 sigma bound). This is slightly smaller than the most recent IR observation estimates of 375((-10))((+14)) m and 380-393 m, reported by Muller et al. (2014) and Licandro et al. (2016) respectively. We estimated a radar albedo of 0.25 +/- 0.11 based on Goldstone data, and an optical albedo, pv, of 0.35 +/- 0.10. Licandro et al. (2016) reported pv in the range of 0.24-0.33. The radar astrometry has been updated using a 3-D shape model. The Yarkovsky acceleration has not been detected in the current orbital fit, but if the position error during the 2021 encounter exceeds 8-12 km, this could signal a detection of the Yarkovsky effect. (C) 2017 Elsevier Inc. All rights reserved.

引用

页码：115 / 128

页数：14

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