NASA selects atmospheric sounder for EOS space platform (Forwarded)
Peter E. Yee
Headquarters, Washington, D.C. January 23, 1989
Jim Wilson
Jet Propulsion Laboratory, Pasadena, Calif.
RELEASE: 89-9
NASA SELECTS ATMOSPHERIC SOUNDER FOR EOS SPACE PLATFORM
NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif.,
has established a new scientific instrument project office to
develop and design a major new system for observing Earth's
atmosphere. Scientists expect it to support a quantum leap in
weather forecasting and in understanding our climate.
The instrument, called the Atmospheric Infrared Sounder
(AIRS), was selected by NASA in late November 1988 to ride aboard
the Earth Observing System (EOS) polar orbiting platform, as a
facility instrument, beginning in the 1990s. This platform is an
element of NASA's Space Station Freedom and proposed "Mission to
Planet Earth" programs. EOS also is one of several Earth-
orbiting scientific platforms planned by the U.S. and other
nations.
The AIRS system will provide global, three-dimensional
information on the temperature and composition distributions in
the atmosphere (including humidity and clouds) as well as
climate-related properties of the sea and land. It also will
measure and help map ozone and various other "greenhouse"
gases. AIRS will observe both day and night.
The instrument is designed to scan 45 degrees East and West
from the North-South suborbital track aboard the EOS platform. It
is being planned to operate 435 miles above the Earth in a 100-
minute, circular orbit. AIRS will observe the atmosphere and
surface in elements about 10 square miles and perceive the
atmosphere in mile-thick vertical layers. It will be designed to
read the temperature in each of these elements to an accuracy of
approximately 1 degree Celsius (about 2 degrees Fahrenheit).
The value of AIRS will be the continuous long-term record it
compiles of climate change. "We can see and measure changes in
global temperature over periods of one or more solar cycles,"
says Dr. Moustafa Chahine, JPL's chief scientist and an
atmospheric physicist. "We will have records of trends in the
greenhouse effect, both in the composition and movement of gases
which cause it and in regional patterns of moisture and air
circulation which may result from it. These are long-term
changes, in contrast to weather patterns and are very subtle."
These measurements will be derived from infrared radiation
data. The Earth emits electro-magnetic radiation which peaks in
the infrared wavelength region. Some of this radiation is
absorbed by gases in the atmosphere. The atmospheric gases
themselves also radiate in the infrared. Determining wavelength
bands the gases absorb and radiate and how intense the radiation
is in the various bands will help determine such things as
composition and temperature. AIRS will be able to make
measurements in 256 spectral channels in the infrared spectrum
(from 3 to 17 microns in wavelength). Accurate temperature
mapping may require the use of 50 to 100 of these channels.
Data processing will be the key to AIRS. Scientists have
been developing the algorithms (the complex of formulas used by
scientists and their computers to turn the measurements into
useful parameters) needed to process, use and understand AIRS
data. These include computer models of the atmosphere which AIRS
will help to refine as well as use in generating maps of the
parameters retrieved after the use of the algorithms. It is
anticipated that processing and interpreting the large
constellation of AIRS measurements will call for large-scale
computers in the "super" class, possibly parallel-processor
designs.
AIRS is similar in some respects to the ATMOS experiment
flown aboard a Shuttle flight in the spring of 1985 and planned
for another Shuttle mission as part of the Atlas 1 mission.
There are substantial differences in the two systems in their
resolutions (how small an element of atmosphere each can pick
out) and in the length of their observing periods. "ATMOS can
observe the makeup of the upper atmosphere better than AIRS for a
short period, but only AIRS can stay at its post observing
changes year in and year out," says project manager Fred
O'Callaghan, who is in charge of both efforts at JPL. "With
refurbishments, we hope to get 15 years or more out of the AIRS
instrument".
AIRS will be a "facility" instrument aboard the EOS
platform. That is, it will function more like a laboratory or
observatory than an instrument designed and operated by a single
scientist or single team.
A scientific committee to be selected by NASA will oversee
its use and data records will be archived for later research as
well as for immediate use.
The AIRS project is part of JPL's Office of Space Science
and Instruments. The EOS scientific program is administered by
Dr. Shelby Tilford of NASA's Office of Space Science and
Applications, Washington, D.C. and the first orbiting platform
will be managed by NASA's Goddard Space Flight Center, Greenbelt,
Md.
Tom Neff
Station? Is that just the budget cubbyhole? Also, how does NASA plan
to "refurbish" AIRS if it's in polar orbit? Is this dependent on a
working OMV? Surely a polar Shuttle mission would be too expensive
for a purpose like this.
--
Tom Neff tn...@well.UUCP
or tn...@dasys1.UUCP
Henry Spencer
>How can something like EOS - in polar orbit - be "part of" the Space
As both the NRC and me -- two illustrious authorities :-) -- have pointed
out, nothing in polar orbit has any rational connection with the space
station whatsoever.
--
Allegedly heard aboard Mir: "A | Henry Spencer at U of Toronto Zoology
toast to comrade Van Allen!!" | uunet!attcan!utzoo!henry he...@zoo.toronto.edu