Phoebe’s orbit from ground-based and space-based observations^⋆,⋆⋆

¹ Shanghai Astronomical Observatory, Nandan Road 80, The Chinese Academy of Science, 200030 Shanghai, PR China
² IMCCE – Observatoire de Paris, UPMC, UMR 8028 CNRS, 77 avenue Denfert-Rochereau, 75014 Paris, France
e-mail: desmars@imcce.fr
³ College of Science, Wuhan University of Science and Technology, 430065 Wuhan, PR China
⁴ Laboratoire AIM, UMR 7158, Université Paris Diderot – CEA IRFU – CNRS,Centre de l’Orme les Merisiers, 91191 Gif-sur-Yvette Cedex, France
⁵ Department of Computer Science, Jinan University, Guangzhou 510632, PR China

Received: 16 January 2013
Accepted: 25 February 2013

Abstract

Context. The ephemeris of Phoebe, the ninth satellite of Saturn, is not very accurate. Previous dynamical models were usually too simplified, the astrometry is heterogeneous and, the Saturn’s ephemeris itself is an additionnal source of error.

Aims. The aim is to improve Phoebe’s ephemeris by using a large set of observations, correcting some systematic errors and updating the dynamical model.

Methods. The dynamical model makes use of the most recent ephemeris of planets and Saturnian satellites. The astrometry of Phoebe is improved by using a compilation of ground-based and space-based observations and by correcting the bias in stellar catalogues used for the reduction.

Results. We present an accurate ephemeris of Phoebe with residuals of 0.45 arcsec and with an estimated accuracy of Phoebe’s position of less that 100 km on 1990–2020 period.