8.10. Mars Express High Resolution Stereo Camera (HRSC)

The HRSC camera on the Mars Express satellite is a complicated system, consisting of multiple channels pointed in different directions plus another super resolution channel. The best option to create DEMs is to use the two dedicated stereo channels. These are pointed ahead of and behind the nadir channel and collect a stereo observation in a single pass of the satellite. Data can be downloaded from the Planetary Data System (PDS) http://pds-geosciences.wustl.edu/missions/mars_express/hrsc.htm or you can use the online graphical tool located at http://hrscview.fu-berlin.de/cgi-bin/ion-p?page=entry2.ion. Since each observation contains both stereo channels, one observation is sufficient to create a DEM.

HRSC data is organized into categories. Level 2 is radiometrically corrected, level 3 is corrected and mapprojected onto MOLA, and level 4 is corrected and mapprojected on to a DEM created from the HRSC data. You should use the level 2 data for creating DEMs with ASP. If you would like to download one of the already created DEMs, it may be easiest to use the areoid referenced version (.da4 extension) since that is consistent with MOLA.

What follows is an example for how to process HRSC data. One starts by fetching the two stereo channels from:


Fig. 8.7 Sample outputs from a cropped region of HRSC frame 1995. Left: Cropped input. Center: Block matching with subpixel mode 3. Right: MGM algorithm with cost mode 3.

8.10.1. Commands

You may need to download the HRSC kernel files in case using web=true with spiceinit does not work. You will also probably need to include the ckpredicted=true flag with spiceinit. HRSC images are large and may have compression artifacts so you should experiment on a small region to make sure your stereo parameters are working well. For this frame, the MGM stereo algorithm performed better than block matching with subpixel mode 3.

ISIS> hrsc2isis from=h1995_0000_s12.img to=h1995_0000_s12.cub
ISIS> hrsc2isis from=h1995_0000_s22.img to=h1995_0000_s22.cub
ISIS> spiceinit from=h1995_0000_s12.cub ckpredicted=true
ISIS> spiceinit from=h1995_0000_s22.cub ckpredicted=true
ISIS> parallel_stereo h1995_0000_s12.cub  h1995_0000_s22.cub \
         --stereo-algorithm 2 --cost-mode 3 mgm/out