31st Annual Meeting of the DPS, October 1999
Session 47. Mars Surface: Spectra Posters
Poster Group II, Thursday-Friday, October 14, 1999, , Kursaal Center

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[47.11] The MVACS Soil Temperature Probe

S. E. Wood (Univ. of Washington), D. A. Paige, A. Nguyen (UCLA), D. Crisp, R. Alleruzzo, C. Labaw, C. Mahoney, R. Vargas, H. Gunderson, D. Braun, J. Slostad, R. Manvi, K. Brown, E. Oakes (JPL)

As part of the Mars Volatiles and Climate Surveyor (MVACS) payload on Mars Polar Lander, currently on its way to a Dec. 3, 1999 landing on the south polar layered deposits, the Soil Temperature Probe (STP) will make direct measurements of the temperatures and thermophysical properties of soils and/or ices accessible by the Robotic Arm (RA). The STP consists of a thin, rigid fiberglass tube 15 cm long containing 2 platinum resistance temperature sensors; one in the metal tip which can be heated (PRT-1), and another inside the tube (PRT-2). It is mounted on the side of the scoop at the end of the RA. To make measurements, the RA places the STP in the desired location on or beneath the surface, and Robotic Arm Camera (RAC) image(s) are taken to verify its position, using ruler markings on the STP to measure its depth. The temperatures of both PRT's are recorded every 3 seconds. Data and commanding are handled through the meteorology instruments (MET) electronics package.

Measurement of thermophysical properties can be done actively or passively. In active mode, PRT-1 is heated at a constant rate (~10 mW). The thermal conductivity of the surrounding soil can be derived from the asymptotic temperature rise. The thermal diffusivity (\alpha) can be derived from the transient response. In passive mode \alpha can also be determined by measuring the change in the amplitude and phase of the diurnal thermal wave at different depths.

The temperature and thermophysical property measurements obtained with the STP will be very useful for interpreting other MVACS observations including air temperature and humidity, the presence or absence of subsurface ice, the identity of any surface frosts (CO2 or H2O), and Thermal Evolved Gas Analyzer soil sample analysis. These STP measurements will also provide invaluable "ground truth" for comparison with data from orbiting spacecraft such as Mars Global Surveyor and Mars Climate Orbiter.

If you would like more information about this abstract, please follow the link to http://www.marspolarlander.com. This link was provided by the author. When you follow it, you will leave the Web site for this meeting; to return, you should use the Back comand on your browser.

The author(s) of this abstract have provided an email address for comments about the abstract: sewood@atmos.washington.edu

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