-2001 MARS ODYSSEY THEMIS-
THEMIS has two multi-band (multi-spectral) cameras. One measures visible and the other thermal infrared images. Here we give some information on the thermal infrared camera and the data release plans.
The THEMIS infrared system measures 9 bands using 10 channels (two of the channels measure the same band). Images have 100-m ground sampling distance. The detector is an uncooled, silicon micro-bolometer array, and is 320 pixels cross-track by 240 pixels along-track, with a 50-µm pitch. The data are digitized to 8 bits.
To provide multi-spectral coverage, filter stripes directly cover the array in the cross-track direction. In order to build a multi-spectral image, multiple images are measured, and then a single, multi-band image can be constructed by offsetting the measured images. This technique is called time delay integration. The technique increases the sensitivity (signal-to-noise ratio), but it can cause striping artifacts.
Additional details are in the
Proposal Information Package and the
Functional Requirements documents (both are PDF).
THEMIS primary goals are to:
• identify localized deposits of aqueous alteration minerals when the deposits cover at least 10% of a 100 meter pixel, and thus identify high priority sample return sites;
• provide a higher spatial resolution link to the Mars Global Surveyor TES by utilizing partial overlap of spectral coverage (~6-12 µm for THEMIS vs. ~6-50 µm for TES);
• study geomorphology and landing site characteristics;
• search for pre-dawn thermal anomalies.
A more detailed description is in the Proposal Information Package (a PDF file).
THEMIS began measuring standard mapping data in Feb. 2002. The first TES/THEMIS team proprietary period ended in October 2002, when the instrument team began allowing community access to some of the data for research through the NASA Planetary Data System (PDS).
After the initial October data release, the instrument team is scheduled to release data for research regularly. They plan to age the data a minimum of 6 months and a maximum of 9 months at release. The PDS
Geoscience Node web site has the archive plan documentation and data release schedule. The site also explains how to register to receive notification when THEMIS data are released. Scientists who have comments or questions about the data archive can contact the
PDS Geoscience Node,
or Mark Sykes, who heads the community's panel that advises the PDS (firstname.lastname@example.org).
Additional information is in two 2003 Lunar and Planetary Science Conference abstracts:
Murray et al.: 2001 Mars Odyssey THEMIS Data Archive
Slavney et al.: 2001 Mars Odyssey Science Data Archives