| Abstract |
AIM is a minisatellite mission within NASA's SMEX (Small Explorer) program designed to provide frequent, low-cost access to space for a variety of missions (the AIM mission was selected in July 2002 with final approval in May 2004). The objective of AIM is to study the causes of Earth's highest-altitude clouds, which occur on the very edge of space. These clouds, referred to as PMCs (Polar Mesospheric Clouds), form in the coldest part of the atmosphere, about 50-90 km above the polar regions, every summer.
PMCs are of special interest as they are sensitive to both global change and solar/terrestrial influences (study of the coupling between the heliosphere and the Earth's atmosphere). Recorded sightings of these silvery-blue, noctilucent or "night-shining" clouds (NLCs) were first reported in 1885 at high latitudes. They have been increasing in frequency and extending to lower latitudes over the past four decades.
The AIM mission will observe PMCs in their thermal, chemical and dynamic environment in which they form in order to determine the connection between PMCs and the meteorology. Specific parameters of the polar mesosphere to be measured are: PMC abundances, spatial distribution, particle size distributions, gravity wave activity, cosmic dust influx to the atmosphere and precise, vertical profile measurements of temperature, H2O, OH, CH4, O3, CO2, NO, and aerosols. The results from this mission will provide the basis for study of long-term variability in the mesospheric climate.
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