The High Resolution Stereo Camera (HRSC) of Mars Express and its approach to science analysis and mapping for Mars and its satellites

International audienceThe High Resolution Stereo Camera (HRSC) of ESA's Mars Express is designed to map and investigate thetopography of Mars. The camera, in particular its Super Resolution Channel (SRC), also obtains images ofPhobos and Deimos on a regular basis. As HRSC is a pushbroom scanning instrument with nine CCD linedetectors mounted in parallel, its unique feature is the ability to obtain along-track stereoimages andfour colors during a single orbital pass.The sub-pixel accuracy of 3D points derived from stereo analysisallows producing DTM swith gridsize of up to 50 m and height accuracy on the order of one imageground pixel and better,as well as corresponding orthoimages.Such data products have been producedsystematically for approximately 40% of the surface of Mars so far,while global shape models and a near-global orthoimage mosaic could be produced for Phobos.HRSC is also unique because it bridges betweenlaser altimetry and topography data derived from other stereoimaging instruments, and provides geo-detic reference data and geological context to a variety of non-stereo datasets.This paper, in addition toan overview of the status and evolution of the experiment, provides are view of relevant methodsapplied for 3D reconstruction and mapping, and respective achievements. We will also review themethodology of specific approaches to science analysis based on joint analysis of DTM and orthoimageinformation, or benefitting from high accuracy of co-registration between multiple datasets, such asstudies using multi-temporal or multi-angular observations, from the fields of geomorphology,structuralgeology, compositional mapping,and atmospheric science. Related exemplary results from analysis ofHRSC data will be discussed.After10 years of operation, HRSC covered about 70% of the surface bypanchromatic images at10–20 m/pixel, and about 97% at better than100m/pixel. As the areas withcontiguous coverage by stereodata are increasingly abundant,we also present original data related to theanalysis of image blocks and address methodology aspects of newly established procedures for thegeneration of multi-orbit DTMs and image mosaics.The current results suggest that multi-orbit DTMswith grid spacing of 50m can be feasible for large parts of the surface, as well as brightness-adjustedimage mosaics with co-registration accuracy of adjacent strips on the order of one pixel,and at thehighest image resolution available.These characteristics are demonstrated by regional multi-orbit data products covering the MC-11(East) quadrangle o fMars, representing the first prototype of a newHRSC data product level