文章基本信息

标题：Arecibo Radar Astrometry of the Galilean Satellites from 1999 to 2016
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作者：Marina Brozović ; Michael C.Nolan ; Christopher Magri 等
期刊名称：The Astronomical journal
印刷版ISSN：0004-6256
电子版ISSN：1538-3881
出版年度：2020
卷号：159
期号：4
页码：2001-2011
DOI：10.3847/1538-3881/ab7023
语种：English
出版社：American Institute of Physics
摘要：Harmon et al.Arecibo radar observations from 1992 provided some of the most precise line-of-sight distance (ranging) measurements of Ganymede and Callisto to date.We report 18 new ranges obtained at Arecibo from 1999 to 2016, among which are the first measurements of Io and Europa.We also report accompanying line-of-sight velocity (Doppler frequency) measurements.In 2015, we detected Europa, Ganymede, and Callisto with time-delay (range) resolutions as fine as 10 μs (1.5 km) while Io was detected with 70 μs (10.5 km) resolution.We estimated residuals for the radar measurements with respect to the latest JPL satellite ephemeris JUP310 and planetary ephemeris DE438.We found that the rms of the time-delay residuals are 29 μs for Io, 21 μs for Europa, 58 μs for Ganymede, and 275 μs for Callisto.When normalized by the measurement uncertainties, these correspond to the rms of 0.82, 1.25, 2.17, and 3.17 respectively.As such, the orbit of Callisto has the largest residuals and may benefit from an orbital update that will use radar astrometry.All Doppler residuals were small and consistent with their 1σ uncertainties.
关键词：Astrometry;Radar astronomy;Galilean satellites