کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5486940 | 1523491 | 2018 | 44 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Goldstone and Arecibo radar observations of (99942) Apophis in 2012-2013
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موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
علوم فضا و نجوم
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
We report radar observations of Apophis obtained during the 2012â2013 apparition. We observed Apophis on fourteen days at Goldstone (8560â¯MHz, 3.5â¯cm) and on five days at Arecibo (2380â¯MHz, 12.3â¯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 µs or â¼20â¯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 450â¯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 = 0.34â¯Â±â¯0.04â¯km (1Ï bound). This is slightly smaller than the most recent IR observation estimates of 375(â10)(+14)m and 380-393â¯m, reported by Müller et al. (2014) and Licandro et al. (2016) respectively. We estimated a radar albedo of 0.25â¯Â±â¯0.11 based on Goldstone data, and an optical albedo, pV, of 0.35â¯Â±â¯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 8-12â¯km, this could signal a detection of the Yarkovsky effect.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Icarus - Volume 300, 15 January 2018, Pages 115-128
Journal: Icarus - Volume 300, 15 January 2018, Pages 115-128
نویسندگان
Marina BrozoviÄ, Lance A.M. Benner, Joseph G. McMichael, Jon D. Giorgini, Petr Pravec, Petr Scheirich, Christopher Magri, Michael W. Busch, Joseph S. Jao, Clement G. Lee, Lawrence G. Snedeker, Marc A. Silva, Martin A. Slade, Boris Semenov,