Slopes from Photoclinometry for the Mars InSight Landing Site Selection Process

Abstract:

Evaluating meter-scale slopes on the Martian surface continues to be an important activity for ascertaining the safety of potential landing sites and for characterizing terrains and their formation and modification processes. The Mars InSight lander is targeting a landing site in Elysium Planitia and the application of the point photoclinometry algorithm that correctly estimated the slope parameters for MER (Beyer et al., 2003) and for MSL (Beyer and Kirk, 2012) is also being applied to HiRISE imagery within the potential landing ellipses being considered. This allows rapid evaluation of slope parameters and also provides a consistency check with terrain models derived from stereo data. The largest source of error in the photoclinometry estimates of slope is the value of the atmospheric haze to subtract for each image. When a stereo-derived terrain model (either from HiRISE or CTX) is present, the slope statistics from that terrain model are used to help 'tune' the photoclinometry-derived slopes for images that overlap that terrain model. In this way better slope data can be extrapolated into nearby regions than the photoclinometry technique alone would be able to accomplish.