EDP Sciences
Free access
Volume 389, Number 1, July I 2002
Page(s) 325 - 333
Section The solar system
DOI http://dx.doi.org/10.1051/0004-6361:20020544

A&A 389, 325-333 (2002)
DOI: 10.1051/0004-6361:20020544

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

R. Vasundhara

Indian Institute of Astrophysics, Bangalore 560034, India

(Received 12 February 2002 / Accepted 5 April 2002 )

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 $\approx$90 km East to $\approx$50 km West on Io and from $\approx$50 km East to $\approx$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 $\pm$ $20 \degr$; 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.

Key words: eclipses -- astrometry -- ephemerides -- occultations -- planets and satellites: general

© ESO 2002