Astrometry from CCD photometry of mutual events of Jovian satellites from VBO during 1997

Indian Institute of Astrophysics, Bangalore 560034, India

Corresponding author: rvas@iiap.ernet.in

Received: 12 February 2002
Accepted: 5 April 2002

Abstract

Astrometric results of CCD observations of the mutual events of the Galilean satellites of Jupiter from the Vainu Bappu Observatory are presented. The shifts in the photo-centers on the disks of Io and Europa due to albedo variations inferred from the available mosaics of Galileo imagery are determined. The estimated shifts from ≈90 km East to ≈50 km West on Io and from ≈50 km East to ≈30 km West for Europa during one orbital period are comparable to the accuracies provided by the present-day ephemerides. In a given mutual event series, the mutual events involving a given satellite pair dominate in number and occur nearly at the same orbital longitude within ± ; all the events are therefore delayed or all of them advanced depending on the direction of the shift of the photo-center. The implications of including these cumulative and sustained longitude residuals on the constructed ephemerides are discussed.