6. Conclusion

The data reported in this paper show how useful a campaign to observe mutual events can be. Unfortunately the data from a few observers could not be used. In order to avoid such accidents in future campaigns, observers are reminded that:

1. the time in UTC is essential and we have to be sure of the scale of time within at least half-a-second;
2. in order to use observations made in difficult conditions (small clouds, ...) the recording of a reference object and of the sky-background simultaneously with the eclipsed or occulted satellites is absolutely necessary. Many lightcurves are of good quality only because of such recordings (cf. Fig. 2 (click here)) and some have been rejected because of the absence of such recordings.

After the PHEMU91 campaign, we look forward for future campaigns: first, we will make a special effort to observe the events of the satellites of Saturn in 1995-1996. They are fainter than the Galilean satellites and larger telescopes should be used; however these events occur only every 15 years which justifies the international campaign we organize and called PHESAT95.

Second we will apply our techniques to observe the mutual events which will occur during the next favorable period in 1997: we will use the experience of the 1991 observations in order to improve the data obtained. If you are interested in joining us for the next campaigns and if you like to receive technical notes in order to help you to observe, please, write to us.

Acknowledgements

These observations have been made possible thanks to the CNRS (Centre National de la Recherche Scientifique), the INSU (Institut National des Sciences de l'Univers) and the CNES (Centre National d'Etudes Spatiales) through the PNP (Programme National de Planétologie) who supports the PHEMU91 campaign, the Bureau des Longitudes and the Observatories where observations were made. We thank amateur astronomers J. Juan-Samso, S. Torrell, F. Gallego, J. Blasco, R. Guarro, C. Gallart, J. Foch, J.V. Piqueras, F. Campos and D. Fernandez for observing these events. We also wish to thank the staff of the observatories where observations were made, especially M.M. Bretagne, Gravallon, Mevolhon, Leydet, Rambaud, Rau and Richaud from Observatoire de Haute-Provence for their help during this campaign and Mrs. Derouazi and Baron for the type-writing of the tables.