Tropospheric Emission Spectrometer
The Tropospheric Emission Spectrometer (TES) is one of four science instruments aboard NASA's Aura satellite, which was launched from Vandenberg Air Force Base, California on July 15, 2004. The satellite flies at an altitude of 705 km (438 miles) in an orbit that takes it near Earth's North and South Poles. With each orbit, the spacecraft advances 22° westward. After 233 orbits (16 days), it is back at its starting point and the pattern repeats. Thus, every 16 days, Aura re-examines the same portions of the atmosphere, and its instruments are able to measure changes that may have occurred in each sampled area. The satellite and its instruments are scheduled to perform their atmospheric studies for five years.
Summary provided by http://tes.jpl.nasa.gov/