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1993-05-03
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PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011
FOR IMMEDIATE RELEASE
The prototype measuring station of NASA's proposed
Network for the Detection of Stratospheric Change has
completed an important test validating its laser remote-
sensing technique for measuring atmospheric ozone. The data
acquired by this station will help to determine trends in the
ozone concentration overhead.
Operated by the Jet Propulsion Laboratory at its
Table Mountain Facility at an altitude of 7,500 feet in the
San Gabriel Mountains in California, the station made
concurrent measurements with a mobile ground laser system,
two orbiting satellites, sounding rockets, and balloon
sondes. Just-reduced data show good agreement between the
readings from the diverse sources.
This operation also culminated a year of
observations by the laser instrument. "It means that Earth-
based and satellite measurements of mid-latitude ozone trends
can be correlated," said Dr. Stuart McDermid, scientist in
charge of the Table Mountain instrument and of the test. The
proposed NASA network of ground-based instruments will not
only complement satellite ozone measurements but will allow
calibration checks whenever the satellites overfly a ground
station. "We also have validated our first year's ozone
trend data," McDermid added.
Ozone in the upper atmosphere absorbs harmful
ultraviolet radiation from the Sun. The JPL instrument uses
an excimer laser and generates ultraviolet light at two
wavelengths absorbed differentially by ozone. Some of this
light is reflected back toward the ground by gases in the
atmosphere. A large telescope with very sensitive
ultraviolet detectors collects and measures part of the
backscattered light, and the amount of ozone is calculated by
comparing the two return signals. The laser generates very
short pulses, and their return to the telescope is timed to
give an accurate altitude profile, in the manner of radar.
Although much attention has recently been given to
polar ozone problems because of the dramatic ozone hole,
monitoring ozone in the mid-latitudes is equally important,
Dr. McDermid pointed out. "This is where we live," he noted.
Other ozone instruments involved in the joint test
were a mobile laser-based system from NASA Goddard Space
Flight Center, remote sensors aboard NOAA and Nimbus
satellites managed by NASA Langley Research Center, and
direct chemical sensors on weather balloons and ultraviolet-
detecting rocket sondes supported by NASA's Wallops Flight
Facility.
The activity is part of NASA's Upper Atmosphere
Research Program, managed by Dr. Robert T. Watson of theNASA Office of Space Science and Applications.
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2/3/89 JHW