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Description
Photometry of mutual events between natural satellites has been verified to be a most effective and accurate ground-based method for obtaining accurate astrometric data through fitting the light curves observed during these events, and it will be valuable to develop the orbital models of the natural satellites. Mutual occultations of J2 Europa by J1 Io (Aug 28, 2009), J1 Io by J2 Europa (Nov 9 and Dec 11, 2009) and J1 Io by J3 Ganymede (Nov 28, 2009) were observed at Yunnan Observatory during the PHEMU09 international campaign. We will calculate the astrometric data of satellites by analyzing and fitting the light curves we got. The same model proposed by N.V. Emelianov (2003SoSyR..37..314E) was used to fit the light curves, with the Lommel-Seeliger scattering law taking into account. Dynamical quantities, such as the deviation of the observed relative satellite motion from the theoretical motion provided by the relevant ephemeris denoted as Dx and Dy, impact parameter and mid-time corresponding to the impact parameter, were obtained for each event respectively. These results have an accuracy of about several mas to 90mas for Dx and Dy and 0.31-2.97s for mid-time. The residuals in determination of longitude shifts (delta(l1) for J1 Io and delta(l2) for J2 Europa) explaining the shifts of the mid-times of the events, were also calculated in the section of discussion which is around 10km with the best ephemerides.
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