Cassini ISS astrometry of the Saturnian satellites: Tethys, Dione, Rhea, Iapetus, and Phoebe 2004–2012^⋆

¹ IMCCE, Observatoire de Paris, UMR 8028 du CNRS, UPMC, Université de Lille 1, 77 av. Denfert-Rochereau, 75014 Paris, France
² Department of Astronomy, Cornell University, 326 Space Sciences Building, Ithaca, NY 14853, USA
e-mail: tajeddine@astro.cornell.edu
³ Astronomy Unit, Queen Mary University of London, Mile End Road, London E1 4NS, UK

Received: 31 December 2014
Accepted: 19 January 2015

Abstract

Context. The Cassini spacecraft has been orbiting Saturn since 2004 and has returned images of satellites with an astrometric resolution as high as a few hundred meters per pixel.

Aims. We used the images taken by the Narrow Angle Camera (NAC) of the Image Science Subsystem (ISS) instrument on board Cassini, for the purpose of astrometry.

Methods. We applied the same method that was previously developed to reduce Cassini NAC images of Mimas and Enceladus.

Results. We provide 5463 astrometric positions in right ascension and declination (α, δ) of the satellites: Tethys, Dione, Rhea, Iapetus, and Phoebe, using images that were taken by Cassini NAC between 2004 and 2012. the mean residuals compared to the JPL ephemeris SAT365 are of the order of hundreds of meters with standard deviations of the order of a few kilometers. The frequency analysis of the residuals shows the remaining unmodelled effects of satellites on the dynamics of other satellites.