A spacecraft that will explore one of the last frontiers in Earth’s atmosphere is nearing launch. NASA’s TIMED (Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics) spacecraft was shipped May 30, 2001 from The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., where it was designed and built, to Vandenberg Air Force Base, Calif. The spacecraft is currently scheduled to launch from Vandenberg’s Western Range on Aug. 10, 2001.
The 2-year TIMED mission will study the effects of the sun and human-induced activities on the least explored and understood portion of Earth’s atmosphere, known as the Mesosphere and Lower Thermosphere/Ionosphere (MLTI) — a gateway between Earth’s environment and space. TIMED will focus on a portion of this atmospheric region located approximately 40-110 miles (60-180 kilometers) above Earth’s surface, studying its basic structure and how energy is transferred into and out of this area.
"Compared to other layers of our atmosphere, we know very little about this region, which is located just a few miles above our heads," says Sam Yee, TIMED project scientist from APL, who is leading the science team’s efforts throughout the mission. "A comprehensive global study of the MLTI as an integrated system has never before been accomplished." The region is too high for balloons and rockets can only provide a brief snapshot of the area’s activity near the rocket, according to Yee. Ground-based instruments can only observe a small portion of the upper atmosphere located over an observation site.
Employing advances in remote-sensing technology, the TIMED spacecraft will be the first to conduct a global study of the MLTI and will establish a baseline against which future studies of changes within this area can be compared and analyzed. "TIMED’s instrument suite will work with a worldwide network of ground-based observation sites to obtain an unprecedented set of comprehensive global measurements of the region’s temperature, pressure, wind and chemical composition, along with its energy inputs and outputs," says Yee.
"This mission will help scientists gain a better understanding of the MLTI region’s structure and how it varies," continues Yee, "which will help the space science community predict its effects on communications, satellite tracking, spacecraft lifetimes and on spacecraft reentering Earth’s atmosphere."
TIMED is the initial mission in NASA’s Solar Terrestrial Probes Program, part of NASA’s initiative to lower mission costs and provide more frequent access to space to systematically study the sun-Earth system.
The TIMED mission is sponsored by NASA’s Office of Space Science in Washington, D.C., and managed by NASA’s Goddard Space Flight Center, Greenbelt, Md. APL designed, built and will operate the spacecraft and lead the project’s science effort during the mission.
For more information about TIMED, visit the mission Web site at http://www.timed.jhuapl.edu. Images of the spacecraft and its journey to Vandenberg Air Force Base, Calif., will be made available online.
Materials provided by Johns Hopkins University Applied Physics Laboratory. Note: Content may be edited for style and length.
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