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A. Mallama (Raytheon ITSS), H. M. Aelion (The Key School)
A new technique has been developed for measuring planetocentric positions for Jupiter’s satellites from HST Wide Field/Planetary Camera images. The planetary terminator and limb are located, and a correction is applied to account for the phase defect along the terminator. The geometric distortion of the camera optics, orientation of the CCD chip, and the spacecraft roll angle are factored in. A model ellipse is generated from the physical ephemeris of the planet. Finally, the planet center coordinates are computed by fitting the model to the limb observations using the method of least squares. A satellite position is determined similarly, and its offset from the planet is calculated. Several dozen images of Jupiter with one or more of its satellites have been processed in this way. A comparison between the measured satellite planetocentric coordinates and JPL satellite ephemerides demonstrates the validity of this new method of analysis.
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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.