A photometric study of mutual phenomena of galilean satellites

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Using Kaare Aksnes' revised predictions, two mutual occultations and four mutual eclipses have been observed photoelectrically. The equipment used consists of a photoelectric photometer mounted on a 60cm Cassegrain reflector and a GG11 filter. Part 1. Mutual Occultations 1. Various criteria and formula for the occulted area S and the occulted brightness I j corresponding to various occultation configurations illustrated in Fig. AF are given in (2) – (20). Certain integral equations involving I j can be solved from the brightness distribution over the apparent disk of the occulted satellite f(R). Tables 4 and 5 show that the occuted satellite J2 has basically uniform disk with some limb brightening. It could be interpreted as having either no atmosphere or one so thin that no limb-darkening is caused. Its brightness distribution over the apparent disk is due to its surface features. One may imagine that a concave area exists near the center of the surface confronting the observer. The actual mesurement of the drop ΔV in visual magnitude is much larger than predicted. (See Tab. 2). The observations also show that Harris' albedo values for the Jovian satellites are questionable. A comparisons is made between the observed and the theoretical light curves (Tables 6 and 7). 2. Part 2. Mutual Eclipses Link's photometric theory of eclipse is generalised. A simplified method of computing is described in section 5. Three theoretical light curves so computed are compared with observed light curves. (Figs. 11–13). In the final part of this paper, the integral equations (90) and (91) of reduced curves are derived and the methods of solving these equations are discussed. The radius of J2 is computed by an iterative process from equation (1) '–(5)'. Using the observational material 102P of 1973. 8. 9.