A University of Colorado at Boulder experiment designed to gather
precise data on the sun’s ultraviolet output and the response of
Earth’s upper atmosphere to solar radiation is slated to be launched
aboard a NASA spacecraft on Dec. 7.

The Solar Extreme Ultraviolet Experiment, or SEE, is one of four
instruments on NASA’s Thermosphere-Ionosphere-Mesosphere-Energetics-
Dynamics, or TIMED, spacecraft. TIMED is scheduled to be launched
aboard a Delta vehicle from Vandenberg Air Force Base, Calif., for a
planned two-year mission.

SEE was designed and built at CU-Boulder’s Laboratory for Atmospheric
and Space Physics under principal investigator Tom Woods, a senior
research associate at LASP. Schaeffer Magnetics Inc. of Chatsworth,
Calif., also assisted with the SEE development by providing the
pointing technology for the instrument.

The purpose of the mission is to study a part of the atmosphere
located approximately 40 to 110 miles above the Earth’s surface. This
tenuous region of the atmosphere is where energy from the sun is first
deposited into Earth’s environment.

The sun’s energy can have profound effects on Earth’s upper atmospheric
regions, heating it and changing its chemical composition. These
effects are particularly strong during solar maximum — the peak of
the sun’s 11-year cycle when it releases enormous amounts of UV
radiation, said Woods.

SEE will use a spectrometer and a suite of photometers to measure the
highly variable solar UV radiation, one of the primary types of energy
deposited into the upper atmosphere. The spacecraft will orbit the
Earth at an altitude of 388 miles, allowing SEE to accurately measure
the sun’s UV output before it strikes Earth’s atmosphere.

SEE will observe the sun once per orbit, for about three minutes each,
while the sun’s entire disk is in full view. At other times, it will
help scientists measure the atmosphere’s density by viewing the solar
light during sunsets.

The sun puts out a range of different frequencies of UV light,
including far-UV, extreme-UV and soft X-rays — the latter of which
are less energetic than those used in a doctor’s office.

Scientists know little about the sun’s output of soft X-rays and
have not been able to measure this part of the solar spectrum with
much accuracy until now. This makes the soft X-ray photometer, an
instrument on SEE, especially important as it will study this
difficult region of the solar soft X-ray spectrum.

The primary objectives of SEE are to precisely measure the sun’s UV
output, to study how it varies and how it affects Earth’s atmosphere.
The instrument will help establish a baseline of observations for
improving solar and atmospheric models.

The SEE science team includes several scientists from CU-Boulder,
the National Center for Atmospheric Research in Boulder, the Naval
Research Laboratory in Washington, D.C., the University of Alaska
in Fairbanks and Space Environment Technologies in Pacific Palisades,

Total cost for the SEE instrument is $6.5 million, with funding
provided by the Johns Hopkins University Applied Physics Laboratory
in Laurel, Md.

TIMED is sponsored by NASA Headquarters, Office of Space Science,
Washington, D.C., and is managed by the NASA Goddard Space Flight
Center’s Solar Terrestrial Probes Program Office in Greenbelt, Md.
The Johns Hopkins University Applied Physics Laboratory designed,
built and will operate the spacecraft and lead the project’s science
effort during its 2-year, on-orbit mission.

Photos and additional information may be found at the official Web
site, http://lasp.colorado.edu/see .