Complementary astrometry of Cassini Imaging Science Subsystem Images of Phoebe

Abstract

Phoebe is the only major satellite of Saturn with a retrograde orbit. The Cassini Imaging Science Subsystem (ISS) took a lot of Phoebe images between 2004 and 2017, but only a selection of them has been reduced. In this paper, we reduced the remaining ISS images of Phoebe. In the reduction, the Gaia EDR3 catalogue was used to provide the reference stars' positions, and the modified moment was used to measure the centre of image stars and Phoebe. Finally, a total of 834 ISS images of Phoebe have been reduced successfully. Compared with the JPL ephemeris SAT375, Phoebe's positions are consistent. The average residuals in the right ascension and declination are 0.08" and $-0.05$", and the standard deviations of the residuals are about 0.2". In terms of residuals in linear units, the means in the right ascension and declination are about 5 km and $-2$ km, respectively; The standard deviations are about 11 km. Compared with the JPL ephemeris SAT427 and IMCCE ephemeris PH20, our measurements show a strong bias and a large dispersion.

arXiv comment8 Pages, 5 figures, Journal article

References in corpus (7)

• The Gaia mission
• The VizieR database of Astronomical Catalogues
• Resonance locking in giant planets indicated by the rapid orbital expansion of Titan
• Astrometric positions for 18 irregular satellites of giant planets from 23 years of observations
• Cassini ISS Mutual Event Astrometry of the Mid-sized Saturnian Satellites 2005-2012
• Phoebe's orbit from ground-based and space-based observations
• The first observed stellar occultations by the irregular satellite (Saturn IX) Phoebe and improved rotational period

Cited by in corpus (3)

• A Centroiding Algorithm for Point-source Trails
• Astrometric Reduction of Saturnian Satellites with Cassini-ISS Images Degraded by Trailed Stars
• Background Intensity Estimation for Cassini-ISS Image Using Deep Learning-Based Diffusion Model