Predictions And Observations Of Events And Configurations Occurringduring The Uranian Equinox

摘要

The occurrence of the Earth and Sun transits through the equatorial plane of Uranus will bring us the opportunity for observations only possible at that time: mutual events of the satellites, search for new faint satellites and measurement of the thickness of the rings. The predictions of the mutual events need a theoretical model of the motion of the satellites. The calculated occurrences of the occultations and eclipses highly depend on the model since these predictions are very sensitive to the relative positions of the satellites. A difference of 0.05arcsec in latitude may make an event inexistent and the accuracy of the theoretical models is around 0.1 arcsec. In order to be sure of the occurrence of each event, we made the predictions using three theoretical models: the first one is GUST86 made by Laskar and Jacobson in 1986, the second is GUST06 based on the former model fitted by Emelianov on new observations and the third one is LA06 based on a brand new theory with an accuracy 10 times better than GUST and fitted on recent observations made since 1950. This comparison shows that some events predicted with one model are not predicted using another one. We try to select the events which will occur surely in order to help the observers to catch the best phenomena. The search for new satellites and the measurement of the thickness of the rings are planned by means of observations at the time of the transit of the Earth in the ring plane.