 Evidence
suggests that Earth and its atmosphere are changing due to both
natural and human-induced effects. Scientists need to understand
current atmospheric processes so they will be better able to
determine future changes and assess the consequences for society.
The upper atmosphere is one of the least explored regions of Earth,
making accurate information about it essential for global climate
change studies. A new NASA spaceborne instrument called SABER
(Sounding of the Atmosphere using Broadband Emission Radiometry)
will allow researchers to learn more about the upper atmosphere by
helping produce the first comprehensive global measurements of this
region. It will provide a never before seen view of the atmosphere
and pave the way for a new area of science. SABER, built by Utah
State University Space Dynamics Laboratory and managed by NASA
Langley Research Center, is one of four instruments on the TIMED
(Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics)
spacecraft scheduled to begin its 2-year mission with launch in
late 2001.
The TIMED mission will study the natural variability of the
Mesosphere and Lower Thermosphere/Ionosphere or the MLTI region.
The technique that SABER will use to sound, or make measurements in
the atmosphere, has never before been used to study the MLTI region
in such detail. SABER’s limb measurements are made as the
instrument views radiation emitted by the atmosphere such as in the
form of airglow. (Fig. 1) These limb scans provide measurements of
the temperature and chemical structure of the atmosphere between 10
and 110 miles in altitude. The experiment will provide fundamental
information on the radiation budget, chemistry and dynamics of the
upper atmosphere.
The Upper Atmosphere’s Radiation Budget
SABER will enhance knowledge of the radiation budget—the
balance between Earth’s incoming and outgoing energy—by
making the first comprehensive global measurements of the energy
balance in Earth’s upper atmosphere. SABER will measure
infrared radiation or heat emitted by the atmosphere over a broad
altitude and spectral range in this region. It will also accurately
determine how strongly the upper atmosphere is heated by
ultraviolet radiation from the Sun. SABER’s observations will
lay the foundation for a new area of science in radiation budget
studies. Its measurements in an altitude range where the energy and
chemistry are unique from other atmospheric regions are the first
of their kind. As compared to lower atmospheric regions, there are
fewer molecules in the MLTI, affecting how the atmos-phere radiates
and absorbs heat. New research in the area will influence how
scientists understand the warming and cooling of the Earth in the
MLTI region.
Key Gases in the Upper Atmosphere
Ozone, water vapor and carbon dioxide are important gases that
warm and cool the MLTI region through absorption of solar radiation
and emission of infrared radiation (heat energy). SABER will
measure the vertical distribution of these gases by directly
observing the infrared energy they emit. These observations will
significantly enhance our knowledge of how these gases influence
the temperature and chemistry of the upper atmosphere—an area
where these processes are least understood due to the previous lack
of measurements. SABER, for example, will make the first-ever
measurements of the global distribution of carbon dioxide
concentrations in the MLTI region. It will also measure the
infrared energy emitted by nitric oxide, a chemically active gas
that strongly influences the natural cooling of the upper
atmosphere. SABER will also provide the first measurements of ozone
during the day and at night in the MLTI region.
Atmospheric Structure and Dynamics
SABER’s comprehensive global measurements of the flow of
energy in Earth’s upper atmosphere will also greatly increase
what scientists know about the structure and the motion of air
(dynamics) of the atmosphere. SABER’s observations will
provide new information about how temperature, density and pressure
change with altitude. They will also track the movement of air
between the poles, from lower to upper atmospheric regions, from
season to season and around the globe. During the mission, SABER
will produce a global picture of how the MLTI region changes over
time.
 For more LASE information, please contact:
NASA Langley Research Center
Office of Public Affairs
Mail Stop 115
Hampton, VA 23681-2199
757-864-6124
Or see the SABER Home Page at:
http://asd-www.larc.nasa.gov/saber/ASDsaber.html
for additional information.
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