Photogrammetric co-registration and photometric analysis of HRSC Phobos images

HRSC images from Mars Express Phobos flybys are used to study the photometric character of the surface of the Martian satellite. This investigation involves measuring of surface reflectance and illumination angles for estimates of a phase curve, and fitting of theoretic photometric functions. As results we obtain information on multispectral and physical properties of the Phobos surface as well as photometrically corrected geomorphological and albedo maps

Spectrometric characteristics of the surface of Phobos from data obtained by HRSC on Mars Express

We investigate the spectral reflectance of the surface of Phobos using remote sensing data obtained by the HRSC on the European Mars Express mission. Color ratios reveal that the Phobos surface is heterogeneous, in agreement with previous studies based on Phobos-2 and Mars Reconnaissance Orbiter data

New Mars Moon Ephemerides in the Context of the December 2013 Mars Express Phobos Close Flyby

International audienceAlmost 70 years after its discovery (Sharpless 1945), Phobos tidal acceleration is still the only way to assess Mars tidal dissipation from observations. But monitoring the Phobos' and Deimos' motion has also important consequences for the success of space experiments. In particular, flyby of moons by spacecraft are the opportunity to quantify with great accuracy gravitational field parameters and to constrain their interior. On December 29th 2013, Mars Express (MEX) crossed Phobos' path at a daring distance of less than 50 km. Due to the satellite's small size, an accuracy of 100 meters on Phobos' position is mandatory to allow for a reliable gravity field estimation. To reach this goal, we reduced 340 astrometric observations acquired by the Super Resolution Channel (SRC) camera onboard of MEX during 38 flybys between May 2013 and February 2014. Moreover, efforts have been done to model the Mars moon dynamical environment with unprecedented accuracy. In particular, last results on Mars rotation as well as the introduction for the first time of asteroids perturbations on the motion of the Martian satellites have been considered. Last, improved trajectories of MEX during SRC observation times have been developed

New Mars Moon Ephemerides in the Context of the December 2013 Mars Express Phobos Close Flyby

International audienceAlmost 70 years after its discovery (Sharpless 1945), Phobos tidal acceleration is still the only way to assess Mars tidal dissipation from observations. But monitoring the Phobos' and Deimos' motion has also important consequences for the success of space experiments. In particular, flyby of moons by spacecraft are the opportunity to quantify with great accuracy gravitational field parameters and to constrain their interior. On December 29th 2013, Mars Express (MEX) crossed Phobos' path at a daring distance of less than 50 km. Due to the satellite's small size, an accuracy of 100 meters on Phobos' position is mandatory to allow for a reliable gravity field estimation. To reach this goal, we reduced 340 astrometric observations acquired by the Super Resolution Channel (SRC) camera onboard of MEX during 38 flybys between May 2013 and February 2014. Moreover, efforts have been done to model the Mars moon dynamical environment with unprecedented accuracy. In particular, last results on Mars rotation as well as the introduction for the first time of asteroids perturbations on the motion of the Martian satellites have been considered. Last, improved trajectories of MEX during SRC observation times have been developed

Physical librations and possible homogeneity of natural moons from astrometry

International audienceAstrometry is the discipline that aims to provide positions of celestial objects in space with the highest accuracy. Thanks to recent space missions like Mars Express and Cassini, astrometric measurements of moons have allowed the probing of the gravity environment of their systems with unprecedented resolution. Here we focus on the possible determination of physical librations on the rotation of the moons, by modelling their effects on the moons' orbits. Assuming a homogeneous density, a theoretical expectation of the main libration can be computed and compared with possible observed values obtained indirectly from the orbit. In this work, we obtain for Phobos a physical libration of 1.04 /- 0.02 degrees, in agreement with a homogeneous interior. The case of some of the inner moons of Saturn will be addressed, also

Physical librations and possible homogeneity of natural moons from astrometry

International audienceAstrometry is the discipline that aims to provide positions of celestial objects in space with the highest accuracy. Thanks to recent space missions like Mars Express and Cassini, astrometric measurements of moons have allowed the probing of the gravity environment of their systems with unprecedented resolution. Here we focus on the possible determination of physical librations on the rotation of the moons, by modelling their effects on the moons' orbits. Assuming a homogeneous density, a theoretical expectation of the main libration can be computed and compared with possible observed values obtained indirectly from the orbit. In this work, we obtain for Phobos a physical libration of 1.04 /- 0.02 degrees, in agreement with a homogeneous interior. The case of some of the inner moons of Saturn will be addressed, also

New astrometric observations of Deimos with the SRC on Mars Express

Between July 2005 and July 2011 Mars Express performed 50 Deimos approaches. 136 super resolution channel (SRC) images were acquired and used for astrometric (positional) measurements of the small Martian satellite. For this study, we have developed a new technique, in which the center-of-figure of the odd-shaped Deimos is determined by fitting the predicted to the observed satellite limb. The prediction of the limb was made based on the moon’s known shape model. The camera pointing was verified and corrected for by means of background star observations. We obtained a set of spacecraft-centered Deimos coordinates with accuracies between 0.6 and 3.6 km (1σ). Comparisons with current orbit models indicate that Deimos is ahead of or falling behind its predicted position along its track by as much as +3.4 km or  −4.7 km, respectively, depending on the chosen model. Our data may be used to improve the orbit models of the satellite