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.