The determination of the center of gravity of a planet from photographic plates |
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| Authors: | Jean-Eudes Arlot |
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| Institution: | (1) Service de Mécanique Céleste du Bureau des Longitudes, Equipe de Recherche Associée au CNRS, Paris, France |
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| Abstract: | The difficulty of the determination of the center of gravity of a planet depends on the fact that it has usually a large apparent diameter. On a photographic plate, the size of the image of a planet depends on the exposure time and, mainly, on the focal length. Moreover, the phase angle (Sun-Planet-Earth) makes the image of the planet dissymetric and the surface features-when existing-make its brightness not uniform.For a planet the position of the satellites of which is well known (for example, Jupiter), tests for the determination of the center of gravity have been made using different methods. These methods need a microdensitometric analysis of the plates and allow a better accuracy for the position of the center of gravity of the planet (referred to near stars) than the classical methods using manual measuring machines.Proceedings of the Conference on  Analytical Methods and Ephemerides: Theory and Observations of the Moon and Planets . Facultés universitaires Notre Dame de la Paix, Namur, Belgium, 28–31 July, 1980. |
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