Upper Atmosphere Research Satellite

Project Description
NASA officially announced its intent to develop the Upper Atmosphere
Research Satellite (UARS) in 1979. Nine instruments and a group of
theoretical investigators were chosen by an open proposal selection
process. An additional instrument, ACRIM, was given a flight of
opportunity on the UARS spacecraft. Due to funding delays and the
Challenger accident, UARS was not launched until 1991. UARS is
considered the first of the Mission to Planet Earth (now Earth Science
Enterprise) series of NASA spacecraft.

UARS was launched on September 15, 1991 by the Space Shuttle
Discovery. It is 35 feet long, 15 feet in diameter, weighs 13,000
pounds, and carries 10 instruments. UARS orbits at an altitude of 375
miles with an orbital inclination of 57 degrees. Designed to operate
for three years, eight of its ten instruments are still
functioning. UARS measures ozone and chemical compounds found in the
ozone layer which affect ozone chemistry and processes. UARS also
measures winds and temperatures in the stratosphere as well as the
energy input from the Sun. Together, these help define the role of the
upper atmosphere in climate and climate variability.

The UARS Project Mission Objectives are to study the
a) energy input and loss in the upper atmosphere
b) global photochemistry of the upper atmosphere
c) dynamics of the upper atmosphere
d) coupling among these processes
e) coupling between the upper and lower atmosphere

Four UARS instruments were devoted to measurements of constituents
that spectroscopically determine the concentrations of many different
chemical species and derived the variation of atmospheric temperature
with altitude by observing infrared emissions from carbon dioxide
(CO2). The instruments are:
1) Cryogenic Limb Array Etalon Spectrometer (CLAES)
2) Improved Stratospheric and Mesospheric Sounder (ISAMS)
3) Microwave Limb Sounder (MLS)
4) Halogen Occultation Experiment (HALOE)

Two instruments, utilizing high-resolution interferometry, will studied
upper-atmosphere winds by sensing the Doppler shift in light absorbed
by or emitted from atmospheric molecules. The wind instruments are:
1) High Resolution Doppler Imager (HRDI)
2) Wind Imaging Interferometer (WINDII)

An additional four investigations obtained estimates of the energy
incident on the atmosphere by measuring solar ultraviolet radiation
and the flux of charged particles from the Earth's magnetosphere.
These are:
1) Solar-Stellar Irradiance Comparison Experiment (SOLSTICE)
2) Solar Ultraviolet Spectral Irradiance Monitor (SUSIM)
3) Particle Environment Monitor (PEM)
4) Active Cavity Radiometer Irradiance Monitor (ACRIM II)


References:
1. Reber, Carl A., The Upper Atmosphere Research Satellite, EOS Trans.
AGU, 71, 1867, 1990.
2. Reber, C. A., C. E. Trevathan, R. J. McNeal, and M. R. Luther, The
Upper Atmosphere Research Satellite (UARS) Mission, J. Geophys. Res.
98, D6, 10643-10647, 1993.
3. Geophysical Research Letters, Vol. 20, 1993.
4. Upper Atmosphere Research Satellite, A Program to Study Global Ozone
Change, NASA publication, 1989.
5. Mission Operations Report, Upper Atmosphere Research Satellite
(UARS), NASA Report S-678-48-91-01.

For more information, see the UARS Home Page:
http://umpgal.gsfc.nasa.gov/

For more information on the Earth Science Enterprise (ESE), see:
http://www.earth.nasa.gov/

For more information on the Earth Observing System (EOS), see:
http://eospso.gsfc.nasa.gov/