An artist's concept of the TIMED saatellite deployed in space. Photo: JHU/APL

A NASA mission will soon reveal the well-kept secrets of a mysterious region situated 40 to 110 miles (about 60 to 180 kilometers) above the Earth called the Mesosphere and Lower Thermosphere/Ionosphere (MLTI), where electrical currents surge and auroras cast an eerie glow over the Northern and Southern hemispheres.

The Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) mission will uncover the mysteries of this region by producing the very first set of comprehensive, global measurements of the MLTI.

Studying the MLTI was nearly impossible until now. Conventional airplanes and balloons cannot reach this high altitude, and it is too low for direct satellite measurements. Satellites traveling at orbital speeds encounter enough particles to burn up, and sub-orbital rockets are limited to studying just one specific area before falling back to Earth after only a few minutes.

This first in a series of six Solar Terrestrial Probes will study the MLTI region from a very high location -- a 388-mile (approximately 625-kilometer) circular orbit around the Earth. TIMED will "share" its launch vehicle with an oceanography mission called Jason-1.

"It is imperative that we learn more about the dynamics of the MLTI because the Sun's energy often has profound effects on the areas directly above and below this region," said Sam Yee, TIMED project scientist at The Johns Hopkins University Applied Physics Laboratory (JHU/APL) in Laurel, Md. "With TIMED, scientists will be able to develop better predictive models of space weather's effects on communications, satellite tracking, spacecraft lifetimes and degradation of spacecraft materials."

TIMED will gather data on the MLTI using four instruments:

• Global Ultraviolet Imager (GUVI). GUVI is an ultraviolet spectrograph designed to measure the composition and temperature profiles of the MLTI region, as well as its auroral energy inputs.
  
  
• Solar Extreme Ultraviolet Experiment (SEE). This instrument will observe solar ultraviolet irradiance (the primary energy that is deposited into the MLTI region). SEE will determine how much this energy varies and how it affects the atmosphere and changes its composition.
  
  
• TIMED Doppler Interferometer (TIDI). TIDI will measure winds and temperature of the MLTI, determining wind speed and direction by examining minuscule changes in the color of light emitted from chemical constituents in the atmosphere.
  
  
• Sounding of the Atmosphere using Broadband Emission Radiometry (SABER). This multi-channel infrared radiometer will measure a wide range of infrared light emitted by the atmosphere at several altitudes.

A unique feature of the TIMED mission is its interdisciplinary approach. The four instrument Principal Investigators, or PIs, will have direct control of their instruments and experiments from the Payload Operations Centers at JHU/APL; NASA Langley Research Center, Hampton, Va.; the University of Colorado, Boulder; and the University of Michigan, Ann Arbor. Each PI institution will send daily commands to the TIMED Mission Operations Center located at JHU/APL, where instructions for the instruments and spacecraft will be gathered and uplinked daily to the TIMED spacecraft. Six interdisciplinary investigators participating in the TIMED mission will analyze and interpret data acquired by the instrument PIs throughout the mission.

NASA and the National Science Foundation are jointly sponsoring a program that will enable the TIMED spacecraft team to closely collaborate with other scientific community members studying the MLTI. The program takes advantage of the synergy between ground- and space-based instruments and of the scientific contributions made by data assimilation and modeling. One of the most significant contributions of the collaborative investigators' program will be to provide ground-based data complementary to that provided by the TIMED spacecraft.

The TIMED mission cost of $193 million includes the spacecraft, instrument payload, and launch vehicle. An additional $42 million has been reserved for data analysis and ground/mission operations. The Solar Terrestrial Probes Program Office at NASA's Goddard Space Flight Center, Greenbelt, Md., manages the TIMED mission for the Office of Space Science, Washington. JHU/APL designed, built and will operate the spacecraft and lead the science effort for NASA during the mission.