Spacecraft to Explore Atmospheric Frontier Set for December Launch

A spacecraft destined to explore one of the last frontiers in Earth's atmosphere is scheduled to launch Dec. 7, 2001, at 7:07 a.m. PST aboard a Delta II rocket from Vandenberg Air Force Base, Calif.

Built and operated for NASA by The Johns Hopkins University Applied Physics Laboratory (APL), in Laurel, Md., the 2-year TIMED (Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics) mission will study the influences of the sun and humans on the least explored and understood portion of Earth's atmosphere — 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 the 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. 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.

But through advances in remote-sensing technology, this mission will be the first to conduct a global study of the MLTI and will establish a baseline for future studies of this area. "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, chemical composition and energy inputs and outputs," says Yee.

As society has become increasingly dependent on satellite technology and communications, through devices such as cell phones and pagers, it's vital to understand the ever-changing nature of this region. "It's important that we learn more about the dynamics of this atmospheric region because the sun's energy often has profound effects on the areas directly above and below this area," says Yee. "TIMED will help scientists develop better predictive models of space weather's effects on communications, satellite tracking, spacecraft lifetimes and degradation of spacecraft materials."

TIMED's unique interdisciplinary approach allows each of the four instruments and their experiments to be controlled independently from four Payload Operations Centers located across the country. Each of these centers will send commands daily to the Mission Operations Center, located at APL, where instructions for the instruments and spacecraft will be uplinked to the spacecraft once a day. TIMED's payload consists of:

GUVI (Global Ultraviolet Imager), a collaborative effort between APL and the Aerospace Corporation in El Segundo, Calif., is a spatial scanning, far-ultraviolet spectrograph that will globally measure the composition and temperature profiles of the MLTI region, as well as its auroral energy inputs. APL will maintain the instrument's Payload Operations Center from its campus in Laurel, Md.

SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) is a multi-channel infrared radiometer designed to measure heat emitted by the atmosphere over a broad altitude and spectral range. SABER will also measure global temperature profiles and sources of atmospheric cooling such as the "air glow," which occurs when energy is radiated back into space. Hampton University, Hampton, Va., is leading SABER's science team from the instrument's Payload Operations Center at NASA Langley Research Center, also located in Hampton. Utah State University, Logan, Utah, built the instrument for NASA Langley Research Center.

SEE (Solar Extreme Ultraviolet Experiment) is a spectrometer and a suite of photometers designed to measure solar ultraviolet radiation — the primary energy deposited into the MLTI atmospheric region — which includes solar soft X-rays and extreme-ultraviolet and far-ultraviolet radiation. SEE was built by the University of Colorado in Boulder where the instrument's Payload Operations Center is also located.

TIDI (TIMED Doppler Interferometer) will globally measure the wind and temperature profiles of the MLTI region. TIDI was built by the University of Michigan in Ann Arbor where the Payload Operations Center is also located.

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 the NASA Goddard Space Flight Center's Solar Terrestrial Probes Program Office, Greenbelt, Md. The Johns Hopkins University Applied Physics Laboratory (APL), in Laurel, Md., designed, built and will operate the spacecraft and lead the project's science effort during the mission.

For more information about the TIMED mission, visit www.timed.jhuapl.edu.

The Applied Physics Laboratory, a division of The Johns Hopkins University, meets critical national challenges through the innovative application of science and technology. For information, visit www.jhuapl.edu.