Jovian satellite positions from Hubble Space Telescope images

• Published in: Icarus (New York, N.Y. 1962) N.Y. 1962), 2004-02, Vol.167 (2), p.320-329
• Main Authors: Mallama, Anthony, Aelion, Halley M, Mallama, Celeste A
• Format: Article
• Language: English
• Subjects: Astronomy; Data reduction techniques; Earth, ocean, space; Exact sciences and technology; Fundamental astronomy and astrophysics. Instrumentation, techniques, and astronomical observations; Image processing; Image processing (including source extraction); Jupiter; Observation and data reduction techniques. Computer modeling and simulation; Planets, their satellites and rings. Asteroids; Satellites of Jupiter; Solar system
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1016/j.icarus.2003.10.011

An accurate technique has been developed for measuring planetocentric positions of Jupiter's satellites from Wide Field/Planetary Camera images. Our method of finding the centers of the satellites and planet is based upon established limb-fitting techniques, but we have adapted those techniques to astrometry. We compare our limb-fitting results with previously published work and discuss its errors. A model ellipse is generated from the physical ephemeris of the planet including its phase defect. Then 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. A total of 76 positions of the galileans satellites, the small moon Amalthea, and the shadows of Io and Ganymede cast on Jupiter have been measured on 61 images. Comparison between the observational results and JPL satellite ephemerides demonstrates the validity of this new method of analysis. The accuracy of the galilean satellite measurements is estimated to be 0.04 arcsec in right ascension and in declination.