The High Resolution Stereo Camera (HRSC) of Mars Express and its approach to science analysis and mapping for Mars and its satellites
Résumé
The High Resolution Stereo Camera (HRSC) of ESA's Mars Express is designed to map and investigate the
topography of Mars. The camera, in particular its Super Resolution Channel (SRC), also obtains images of
Phobos and Deimos on a regular basis. As HRSC is a pushbroom scanning instrument with nine CCD line
detectors mounted in parallel, its unique feature is the ability to obtain along-track stereoimages and
four colors during a single orbital pass.The sub-pixel accuracy of 3D points derived from stereo analysis
allows producing DTM swith gridsize of up to 50 m and height accuracy on the order of one image
ground pixel and better,as well as corresponding orthoimages.Such data products have been produced
systematically 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 between
laser 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 to
an overview of the status and evolution of the experiment, provides are view of relevant methods
applied for 3D reconstruction and mapping, and respective achievements. We will also review the
methodology of specific approaches to science analysis based on joint analysis of DTM and orthoimage
information, or benefitting from high accuracy of co-registration between multiple datasets, such as
studies using multi-temporal or multi-angular observations, from the fields of geomorphology,structural
geology, compositional mapping,and atmospheric science. Related exemplary results from analysis of
HRSC data will be discussed.After10 years of operation, HRSC covered about 70% of the surface by
panchromatic images at10–20 m/pixel, and about 97% at better than100m/pixel. As the areas with
contiguous coverage by stereodata are increasingly abundant,we also present original data related to the
analysis of image blocks and address methodology aspects of newly established procedures for the
generation of multi-orbit DTMs and image mosaics.The current results suggest that multi-orbit DTMs
with grid spacing of 50m can be feasible for large parts of the surface, as well as brightness-adjusted
image mosaics with co-registration accuracy of adjacent strips on the order of one pixel,and at the
highest 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.