6 Conclusions

The results reported in this paper can be used directly to refine the orbital elements of the Galilean satellites. It should be kept in mind that a refined set of satellite orbital elements can be inferred from the entire data base of available observations of these satellites. The new portion of observational data obtained as a result of the observational campaign performed contributes significantly to the overall data base of the events considered.

The estimates made in this paper show that the satellite positional data inferred from photometric observations of mutual occultations and eclipses of the satellites considered proves to be several tens to several hundreds of times more accurate than the results of the best ground-based photographic observations. We obtained our data with rather modest observational equipment available at the observatories that took part in the campaign.

A preliminary analysis of the accuracy estimates reported in this paper and inspection of plots illustrating the observationa results led us to the following conclusions. In some cases the discrepancies between the results of observations of the same event at different observatories exceed the estimated internal errors of each observation, which is indicative of certain systematic errors

The greatest error in positional data inferred from such external estimates is due to errors of photometric measurements Only in some specific cases have there been significant discrepancies between observing times. This leads us to a preliminary conclusion that such observations require more accurate allowance for interfering factors. The latter can include scattered light falling into photometer or distortions introduced by the detector. A more detailed analysisof observations is needed. We can finally conclude that the observing campaign carried out by observatories in Kazakhstan, Russia, and Ukraine in 1997 yielded the expected result. The number of successful attempts increased substantially compared to previous similar observations carried out in 1995 and earlier. To improve this very efficient technique for extracting astrometric information about planetary satellites, the observatories need to be provided with new observing equipment.

Acknowledgements

This work was supported by the Russian Foundation for Basic Research, project No. 97-02-16551.