Temperature, pressure, and wind instrumentation in the Phoenix meteorological package

The meteorological package (MET) on the Phoenix Lander is designed to provide information on the daily and seasonal variations in Mars near-polar weather during Martian late spring and summer. The present paper provides some background on the temperature, pressure, and wind instrumentation on the Phoenix MET station and their characterization. A separate paper addresses the MET lidar instrument. Laboratory studies in a Mars wind tunnel confirm estimates that the time constant of the thermocouples should be less than 0.5 s for wind speeds of 5 m s(-1) or greater. Solar radiation falling on the thermocouples could raise the reported temperatures by up to 0.7 K for wind speeds of 5 m s(-1). The increase will be wind speed dependent and will increase to 0.8 K at U = 3 m s(-1) under peak solar radiation. Pressure sensors will give Mars surface pressures accurate to 10 Pa or better while Telltale deflections should provide reliable wind speed information up to at least 10 m s(-1). The paper also discusses, to a limited extent, how the MET instruments will be used in conjunction with other instruments on the Phoenix Lander to provide an enhanced meteorological data set. We also describe instrumentation related to the Atmospheric Structure Experiment during entry, descent, and landing (EDL). These instruments will provide deceleration data. Together with drag coefficient information and a surface pressure measurement from MET, these data will allow us to infer the density, pressure, and temperature structure throughout the vertical column during EDL.