Aeronomy of Ice in the Mesosphere
Launch Date: April 25, 2007
Mission Project Home Page - http://aim.hamptonu.edu/
Fifty miles above the ground, Earth's highest clouds form an icy membrane at the edge of the atmosphere. In 2007, NASA launched the Aeronomy of Ice in the Mesosphere (AIM) mission to study these mysterious Polar Mesospheric Clouds (PMC's) over the course of two years.
Unlike the more common clouds that form at about five miles above Earth's surface, PMC's can only be seen near twilight. They usually form only at high latitudes near the North and South Poles. In recent years, however, these clouds are being seen at lower latitudes more frequently. They are of special interest to scientists because the increased sightings may be related to climate change.
First seen in 1885, two years after the powerful eruption of the Indonesian volcano Krakatoa, scientists originally thought PMC's formed from the plumes of ash propelled into the sky during that eruption. But the clouds have persisted long after the effects of Krakatoa were felt. These days, some scientists think they're caused by space dust, while others believe that modern-day PMC's are indicators of Earth's changing climate. One thing is for certain: PMC's are shaped by the meteorology of the mesosphere, which does appear to be changing.
NASA's AIM spacecraft produced this composite UV-wavelength image on June 11, 2007 showing what noctilucent clouds (NLCs) look like from a vantage point 600 km over Earth's north pole.
The primary goal of the AIM mission is to help scientists understand whether the clouds' ephemeral nature, and their variation over time, is related to Earth's changing climate - and to investigate why they form in the first place. By measuring the thermal, chemical and other properties of the environment in which the mysterious clouds form, the AIM mission will provide researchers with a foundation for the study of long-term variations in the mesosphere and its relationship to global climate change. In addition to measuring environmental conditions, the AIM mission will collect data on cloud abundance, how the clouds are distributed, and the size of particles within them.
With its three onboard instruments, the AIM spacecraft will collect data continuously as it orbits the globe. The instruments include:
- Cloud Imaging and Particle Size Experiment (CIPS), an imager that will take pictures of the clouds to show when and where they exist, as well as what they look like at various stages of formation.
- Solar Occultation for Ice Experiment (SOFIE), which will use solar occultation to measure the temperature and makeup of the surrounding environment.
- Cosmic Dust Experiment (CDE), which will record how much dust enters the mesosphere from meteors. Some have proposed that water vapor latches onto these dust particles, freezing and helping to form PMC's.
AIM launched April 25, 2007 aboard a Pegasus rocket from Vandenberg Air Force Base, California. The expected mission life is 26 months.