2003-2004 Phoebe CCD astrometry

We used a large CCD detector (2048 x2048 pixels) mounted on the 1.56m astrometric reflector at the Sheshan Station, near Shanghai. In our reduction, an up-to-date catalogue of stars, UCAC2 (Zacharias et al., 2004, Cat. <I/289>), was chosen to ensure a proper astrometric calibration.

A comparison of our observations to three recently available, high quality ephemerides, including the JPL SAT185 by Jacobson (SAT185, JPL satellite ephemeris), has shown that most of our observed positions of Phoebe present an accuracy of some tens of mas, which appears to be a very high level for such a faint satellite.