DTM generation from STC-SIMBIO-SYS images

The research group with the responsibility of the STereo Camera (STC) for the ESA BepiColombo mission to Mercury, has realized an innovative and compact camera design in which the light collected independently by two optical channels at ±20° with respect to the nadir direction converges on unique bidimensional detector. STC will provide the 3Dmapping of Mercury surface, acquiring images from two different perspectives. A stereo validation setup has been developed in order to give a much greater confidence to the novel instrument design and to get an on ground verification of the actual accuracies in obtaining elevation information from stereo pairs. A series of stereo-pairs of an anorthosite stone sample (good analogue of the hermean surface) and of a modelled piece of concrete, acquired in calibration clean room by means of an auxiliary optical system, have been processed in the photogrammetric pipeline using image correlation for the 3D model generation. The stereo reconstruction validation has been performed by comparing the STC DTMs (Digital Terrain Models) to an high resolution laser scanning 3D model of the stone samples as reference data. The latter has a much higher precision (ca. 20 μm) of the expected in-lab STC DTM (190 μm). Processing parameters have been varied in order to test their influence on the DTM generation accuracy. The main aim is to define the best illumination conditions and the process settings in order to obtain the best DTMs in terms of accuracy and completeness, seeking the best match between the mission constraints and the specific matching aspects that could affect the mapping process.