Accurate pressure observations in the Martian southern polar region: MVACS /MET-P

A.-M. Harri, J. Polkko, T. Siili (Finnish Meteorological Institute /GEO), D. Crisp (NASA /Jet Propulsion Laboratory)

Pressure observations are crucial for the success of the Meteorology (MET) package for the Mars Volatiles and Climate Surveyor (MVACS) expected to land on Mars in December 1999 ( tex2html_wrap16 tex2html_wrap17 tex2html_wrap18 ), nominally to the location 71 tex2html_wrap19 S, 210 tex2html_wrap19 W. The initial period of operation may last up to 210 sols. The MVACS/MET experiment will provide the first surface-based observations of atmospheric pressure, temperature, wind, and humidity in the southern hemisphere of Mars and in the polar regions.

The Martian atmosphere goes through a large scale atmospheric pressure cycle due to the annual condensation/sublimation of the atmospheric carbon dioxide. Pressure also exhibits short period variations associated with dust storms, tides and other atmospheric events. A series of pressure measurements can hence tell us about the large scale state and dynamics of the atmosphere. The shorter time scale phenomena are also important in contributing to our understanding of mixing and transport of heat, dust, and water vapor.

The sensing element of the MET-P will comprise four Barocap radiosonde sensors manufactured by the Vaisala Inc. These sensors were space qualified for the Mars-96 Small Stations and Penetrators. The same type of sensors will also fly onboard the Huygens/Cassini as a part of the atmospheric structure instrument.

The characteristics of the seasonal and shorter term pressure variations anticipated to take place place at the MVACS landing site, the design of the MET-P instrument and the predicted performance thereof are discussed.