Planetary topography measurement by descent stereophotogrammetry

Digital Terrain Models (DTMs) provide valuable insights into the nature of solar system surfaces, facilitating geological analysis, landing site selection and characterisation, contextualising in situ measurements. For missions to bodies for which orbiters soft landed platforms are technologically or financially challenging achieve, low mass descent ascent probes (e.g. planetary penetrators) an alternative means by access atmosphere and/or surface, a platform from image surface range altitudes perspectives. This paper presents study concept large-coverage stereophotogrammetry, whereby stereo geometry vertically offset wide-angle images is used measure topography over region large extent. To do this, we simulate Mars' Gale Crater using coverage, high resolution DTM area, derive topographic measurements matching pairs simulated images. These compared directly with original characterise their accuracy, dependence elevation measurement accuracy on thus investigated. pair given altitude (corresponding its lower image), error found have minimum value at horizontal distance between 1 3 times altitude. point imaging location, 0.2 0.5 this achieve best accuracy. Surface appearance, change two pair, significant impact performance, limiting baseline length optimum 0.2–0.4 image's altitude, resulting occurrence occlusions blind spots, particularly oblique viewing angles.