Mutual events of Jupiter's satellites observed in 1997 at the Bordeaux Observatory

¹ Observatoire Aquitain des Sciences de l'Univers, UMR 5804, Laboratoire d'Astrodynamique, d'Astrophysique et d'Aéronomie de Bordeaux (L3AB), 2 rue de l'Observatoire, 33270 Floirac, France e-mail: dourneau@obs.u-bordeaux1.fr
² Observatoire Midi Pyrénées, 14 avenue Edouard Belin, 31400 Toulouse, France

Received: 2 July 2004
Accepted: 21 February 2005

Abstract

We present photometric observations of mutual events of the Galilean satellites of Jupiter made in 1997 at the Bordeaux Observatory as part of the international PHEMU97 campaign. We observed 21 events which provided 14 high quality light curves with the CCD camera mounted on the 62 cm telescope. From these curves, we determined observed values and errors for the maximum intensity drop and the time of this light minimum. Phase correction was applied to this time for a proper comparison to theoretical values. Residuals between observed and computed values of both of these parameters have been derived from Arlot's G5 ephemerides. The discussion of errors and residuals shows that these observational parameters generally are so accurately determined that they lead to satellite positions with an angular precision of about ten milliarcseconds, never obtained with classical astrometry. In addition, some theoretical results have been derived from the analysis of our set of observations. The main result concerns the satellite J1 for which our observations of the time of maximum event suggest an advance in longitude of 269 km with respect to G5. Also, for the satellite J4, we similarly obtain a delay of about 170 km which appears to be a real effect.