AMTS

The Arctic Mesopause Temperature Study (AMTS) targeted the coldest part of the earth's atmosphere: the mesopause, about 85 kilometers (53 miles) above the North Pole in summer. The cold is caused by an upwelling of air over the polar caps, says principal investigator Chester Gardner (University of Illinois, UI).

Before AMTS, the highest altitude at which polar temperatures had been measured was about 30 km, using balloons. To sample the mesopause, Gardner collaborated with George Papen (UI), Jerry Gelbwachs (The Aerospace Corporation), and RAF to develop and deploy a new instrument, the Iron Boltzmann Lidar. It takes advantage of a layer of atomic iron in the mesosphere, the residue of meteors that burned up in this region. Iron absorbs light and re-emits it at certain wavelengths, giving a bright backscatter signal. The lasers in the lidar are tuned to two of those wavelengths. As the laser light passes through the iron layer, the resulting glow is detected by the lidar's two telescopes.