Ultraviolet Imager to Help Explore
Complex Region of Atmosphere

EL SEGUNDO, Calif. (8/11/99) -- The least explored and least understood region of Earth's atmosphere -- a place too high for balloons and too low for satellites -- will be explored next year when a remote-sensing spacecraft bearing a payload developed with the leadership of The Aerospace Corporation is launched from Vandenberg Air Force Base as part of a two-year NASA mission.

The mission, known as TIMED (Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics), will study the influence of humans and the sun on the mesosphere and lower thermosphere and ionosphere. This is a region 40 to 110 miles above Earth's surface where solar X-rays and extreme ultraviolet radiation are absorbed.

TIMED will carry a four-instrument payload including the Global Ultraviolet Imager (GUVI), a collaborative effort between The Aerospace Corporation and the Applied Physics Laboratory at Johns Hopkins University.

"GUVI has been delivered on schedule, has been installed and is now undergoing further calibration," said Dr. Andrew Christensen, principal director of the Space and Environment Technology Center and principal investigator on the $8 million program.

Christensen's responsibilities include the design, fabrication and operation of the instrument and analysis of flight data. Other Aerospace efforts centered on software and electronics for the GUVI payload. The three other TIMED instruments are being built elsewhere and will be integrated into the satellite during the next few months.

GUVI will measure composition and temperature profiles of the region as well as high-latitude auroral energy input.

"This is the most complex region of the atmosphere, a transition region," Christensen said. "It is difficult to get there and difficult to model. This region is the last to get a comprehensive global study."

Participating in the TIMED GUVI project were teams from the University of Alaska, the Naval Research Laboratory, Southwest Research Institute, University of Colorado and Computational Physics, Inc.