Marita Wählisch

Mars Express HRSC Data Processing - Methods and Operational Aspects

Automated procedures for ground processing of Mars Express HRSC data have been developed and are applied systematically immediately after download in order to provide calibrated data sets as well as photogrammetric image and 3D data products within a short time frame. Multi-spectral orthoimages in scales of 10 - 50 m/pixel and digital terrain models of 200 m raster width are generated within days even for large orbits covering areas of several hundred thousand square kilometers. An even higher image resolution of up to 2.3 m/pixel provided by HRSCs Super Resolution Channel (SRC) extends the potential of the HRSC camera experiment.

HRSC on Mars Express - Photogrammetric and Cartographic Research

The High Resolution Stereo Camera (HRSC) on the European spacecraft Mars Express is the first camera on a planetary mission especially designed for photogrammetric and cartographic purposes. Since January 2004 the camera has been taking image data from the Martian surface, characterized by high-resolution, stereo capability and color. These data provide an enormous potential for the generation of 3D surface models, color orthoimages, topographic and thematic maps, and additional products. The image data acquired undergo calibration and systematic processing to orthoimages and 3D data products. Within the international HRSC Science Team the members of the Photogrammetric/Cartographic Working Group are concerned with further refinements in order to achieve highest quality data products. These activities comprise improvements of the exterior orientation of the camera, various approaches to enhance DTM quality, and the generation of maps in the standard scale of 1:200 000 and larger scales as well. The paper reports on these activities and the results achieved so far.

New astrometric observations of Phobos with the SRC on Mars Express

Aims. From April 2008 to August 2011 Mars Express carried out 74 Phobos flybys at distances between 669 and 5579 km. Images taken with the Super Resolution Channel (SRC) were used to determine the spacecraft-centered right ascension and declination of this Martian moon. Methods. Image positions of Phobos were measured using the limb-fit and control-point measurement techniques. Camera pointing and pointing drift were controlled by means of background star observations that were compared to corresponding positions from reference catalogs. Blurred and noisy images were restored by applying an image-based point spread function in a Richardson-Lucy deconvolution. Results. Here, we report on a set of 158 Phobos astrometric observations with estimated accuracies between 0.224 and 3.405 km circular w.r.t. the line of sight to the satellite. Control point measurements yield slightly more accurate results than the limb fit ones. Our observations are in good agreement with the current Phobos ephemerides by the Jet Propulsion Laboratory (JPL) and the Royal Observatory of Belgium (ROB) with mean offsets of up to 335 m. Our data can be used for the maintenance and update of these models.

The Mapping Performance of the HRSC/SRC in Mars Orbit

The images obtained by the HRSC (High Resolution Stereo Camera) on Mars Express show excellent potential for topographic mapping of the planet. The derived stereo models agree with topographic data obtained earlier by MOLA (Mars Orbiter Laser Altimeter) on the Mars Global Surveyor: For the image scenes from the Mars Express commissioning phase that were studies, we find absolute difference in heights as small as 50 m and laterial positional differences along MOLA tracks of about 100 m. We show that HRSC effectively fills the gap between the MOLA tracks. SRC (Super Resolution Channel) images as well placed at their nominal geometric positions and reveal further detail within the HRSC context images. However, many of the images, fall short of the expected image quality for reasons to be examined.