Position measurements of Phobos shadows in HRSC and MOC images and implications for the Phobos orbit

Kurzfassung

Discrepancies between orbit models and observed Phobos positions have renewed the interest in studies of the orbit evolution of this small Martian satellite. Hence, we have analyzed observations of Phobos' shadow on the ground to obtain more constraints on the current orbit of Phobos. Unlike direct observations of Phobos during spacecraft flybys, observations of the shadow position with respect to adjacent surface features at a given time do not suffer from uncertainties in the spacecraft orbit and pointing data. We evaluated shadow observations of HRSC (High Resolution Stereo Camera) on Mars Express, as well as those by MOC ( Mars Orbiter Camera) on Mars Global Surveyor.