AIM (Aeronomy of Ice in the Mesosphere) is a NASA Small
Explorer spacecraft launched April 25, 2007, into a high-inclination,
600-km altitude orbit for study of noctilucent clouds (also called Polar
Mesospheric Clouds) that occur at 80-90 km altitudes at high latitudes in
summer time and are thought to be formed by ice crystals.

AIM carried three instruments:

• The Cloud Imaging and Particle Size (CIPS) experiment
  that provides an average 5km x 5km resolution in downward-looking images.
• The Solar Occultation For Ice Experiment (SOFIE) for limb profiles of
  temperatures and absorptions for various molecules.
• The Cosmic Dust Experiment (CDE).