Astrometric observations of Phobos and Deimos with the SRC on Mars Express

Observations of Phobos and Deimos, carried out by the SRC ( Super Resolution Channel) on the Mars Express spacecraft between May 2004 - April 2005, were used to determine the center-of-figure positions of the two Satellites with accuracies of 0.5 - 5 km (Phobos) and 1.0 km ( Deimos). We find that the Phobos and Deimos orbit predictions from NASA-JPL ( Jet Propulsion Laboratory) and ESA-ESOC ( European Space Operation Center) differ substantially among each other and also do not agree with the actually observed positions of the satellites. Hence, our new astrometric data may motivate new efforts for Phobos and Deimos orbit modeling.