NRL Providing Data Analysis and Modeling for NASA AIM Mission

4/26/2007 - 28-07r
Contact: Public Affairs Office, (202) 767-2541

NASA's Aeronomy of Ice in the Mesophere (AIM) satellite is a two-year mission that launched April 25 to study Polar Mesospheric Clouds (PMCs), the Earth's highest clouds, which form an icy layer 50 miles above the surface at the edge of space. Once data is collected from the experiments onboard AIM, the Upper Atmospheric Physics Branch of the Naval Research Laboratory's Space Science Division will apply its expertise in data analysis and modeling to the AIM project.

Among the datasets which motivated the AIM project and convinced NASA to fund the mission were those from NRL's Middle Atmosphere High Resolution Spectrograph Investigation (MAHRSI) which flew on the space shuttle twice to measure hydroxyl (OH) in the middle atmosphere. The second mission in August 1997 yielded unprecedented insight on the distribution of water vapor (H2O) and PMCs in the Arctic summer mesosphere that has led to new ideas on PMCs and their formation environment. The Space Science Division has recently just launched a follow-on instrument to MAHRSI, called SHIMMER, which will also make some PMC observations that will be coordinated with AIM.

These clouds, which are visible from the ground with the naked eye, form in the spring and summer at high latitudes and have been seen for over a century, reflecting the Sun's light in the twilight sky. While one and the same phenomenon, they are called Noctilucent Clouds (NLCs) when observed from the ground at twilight and PMCs when viewed from space platforms with instruments that can sense their presence at any time of the night or day. Previous satellites have inferred the presence of PMCs but were not designed to determine their properties.

Noctilucent Clouds were first observed in 1885 by an amateur astronomer and have been becoming brighter, more frequent and appear to be moving to lower latitudes in recent years. The primary goal of the AIM mission is to explain why PMCs form in the first place and what is causing the mysterious changes in their behavior.

AIM will carry three state-of-the-art instruments: Cloud Imaging and Particle Size (CIPS), Solar Occultation For Ice Experiment (SOFIE) and the Cosmic Dust Experiment (CDE). Each will take precise measurements of NLCs and related parameters in the Earth's upper atmosphere.

CIPS has four cameras positioned at different angles, allowing scientists a 2-D look at the clouds as the satellite looks forward, passes by and looks back at them. Multiple views of the clouds from different angles allow a determination of the sizes of the ice particles that make up the cloud. The cameras will provide panoramic PMC images of the polar cap daily.

SOFIE will use solar occultation to measure cloud particles, temperature and atmospheric gases involved in forming the clouds. The instrument will reveal the recipe of chemicals that prompt PMCs' formation. It will provide the most accurate and comprehensive look to date of ice particles and chemicals within the clouds as well as of the environment in which the clouds form.

CDE records the amount of space dust that enters the atmosphere from the cosmos. It will allow scientists to determine the role the particles have in PMC formation.

AIM is a NASA-funded SMall EXplorers (SMEX) mission led by the Center for Atmospheric Sciences at Hampton University in Virginia. The Laboratory for Atmospheric and Space Physics (LASP), University of Colorado at Boulder, built the CIPS and CDE instruments, manages the AIM mission and will control the satellite after launch. The Space Dynamics Laboratory, Utah State University, built the SOFIE instrument and has one co-investigator. Other research institutions involved include Virginia Tech, Blacksburg, VA; Gats, Inc., Newport News, VA; NRL; George Mason University, Fairfax, Va.; and the British Antarctic Survey, Cambridge UK. Orbital Sciences Corporation, Dulles, VA, designed, manufactured and tested the AIM spacecraft.

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