The Mars Polar Lander's Meterological Package (MET) will function as a Martian weather station. A similar instrument was valuable a part of the Mars Pathfinder Lander, providing daily temperature information, however this instrument will also give wind and water vapor data. The instrument is a collection of sensors at different heights on the lander, that will provide an accurate picture of the temperature, wind, and water vapor from the surface to about 2 meters high. With this information, scientists can understand the cycle of volatiles between the atmosphere and the surface. These will be the first surface-based observations of weather in the southern hemisphere of Mars and the first in the polar regions. The humidity sensor is capable not only of measuring the amount of water vapour in the atmosphere, but also of measuring the abundances of certain atomic isotopes, which may provide key information about the evolution of the Martian atmosphere. As well as providing insight into atmospheric processes over a wide range of scales, the package will provide environmental information that will aid in lander operations and in the interpretation of data from other MVACS instruments.

Parts of the MET and Their Function:

• The MET Mast
  The 1.2 meter mast will measure wind speed and direction, and air temperature. There are 3 temperature sensors at different heights along the mast, a wind speed and direction sensor, and a Tunable Diode Laser (TDL). The TDL measures the amounts of water vapor in the air, and the amounts of water and CO₂.
  
  

• The Secondary MET Mast
  This is an important aspect of the MET because it is one of the first instruments to record the temperature and wind speed and direction near the surface
  
  

• The Robotic Arm Elbow Temperature Sensor
  This sensor, located on the "elbow" of the Robotic Arm will allow scientists to read the temperature at any level, just by moving the Robotic Arm.
  
  

• The Soil Temperature Probe (STP)
  The STP is located on the back of the Robotic Arm Scoop, and can be pushed into the ground to measure the temperature of the Martian soil. This will also allow scientists to record the temperature of the soil that is deposited in the TEGA. When in the soil, the black and white markings indicate the depth at which it is taking measurements.
  
  

• The Pressure Sensor
  The MET Pressure Sensor, located in the Payload Electronics Box, will measure the changes in the atmospheric pressure near the surface. No surface pressure data have ever been taken in this hemisphere. Because of the relatively short life of the MVACS mission (nominally 90 days) a full annual record cannot be obtained, however the mission is long enough to measure some seasonal variability which we should be able to compare with records of the Viking Pressure Sensor.