The Pressure Modulator Infrared Radiometer (PMIRR) is an atmospheric instrument that will fly aboard the Mars Climate Orbiter in January 1999. PMIRR's scientific mission is to study the atmosphere for a full Martian year, giving us the most complete picture of the Martian weather yet. The PMIRR data will allow scientists to derive atmospheric factors such as temperature, water vapor levels, and dust content, from the Martian surface level through altitudes as high as 50 miles. Such information helps produce more accurate global models of the Martian environment, a necessary precursor for future robotic and human exploration missions.