Aeronomy of Ice in the Mesosphere

The Aeronomy of Ice in the Mesosphere (AIM) is a satellite to conduct a 26-month study of noctilucent clouds (NLCs). It is the ninetieth Explorer program mission and is part of the NASA-funded Small Explorer program (SMEX). On April 25, 2007 AIM was boosted into a 600 km high polar orbit by a Pegasus-XL rocket, which was air-launched from the Lockheed L-1011 Stargazer aircraft operated by Orbital Sciences.

Spacecraft and instruments
The AIM satellite is a 200 kg, 1.4 m by 1.1 m spacecraft, powered by two solar arrays, carrying three instruments:


 * Cloud Imaging and Particle Size (CIPS)
 * Cosmic Dust Experiment (CDE)
 * Solar Occultation for Ice Experiment (SOFIE)

The Cloud Imaging and Particle Size (CIPS) instrument has four cameras positioned at different angles, which provide multiple views of the clouds from different angles and will allow a determination of the sizes of the ice particles that make up the cloud.

The Cosmic Dust Experiment (CDE) records impacts from cosmic dust particles as they enter Earth's upper atmosphere. The instrument uses fourteen polyvinylidene fluoride detectors, which emit a pulse of charge when impacted by a hypervelocity dust particle (velocity 1 km/s). A measurement of the value and variability of the cosmic dust input will allow scientists to determine the role the particles have in PMC (Polar Mesospheric Cloud) formation. CDE is a nearly identical replica to the Student Dust Counter on the New Horizons mission.

The Solar Occultation for Ice Experiment (SOFIE) uses solar occultation to measure cloud particles, temperature and atmospheric gases involved in forming the clouds. The instrument will reveal the mixture of chemicals that prompt NLC's formation, as well as the environment in which the clouds form.

Noctilucent clouds
The noctilucent clouds AIM is to study, also known as polar mesospheric clouds, occur in the Earth's atmosphere at high altitudes of roughly 80 km above the surface, far higher than other clouds. The AIM mission will help determine what factors — temperature, water vapor, and dust particles — lead to the formation of these clouds. The clouds seem to be a relatively recent phenomenon: they were first seen in 1885, and lately seem to be occurring more frequently. The clouds always occur during the summer season near the poles and the Northern season always starts around the same time. Scientists have found that the start of the Southern season can vary up to a month however.