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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 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 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 allowcalibration checks whenever the satellites overfly 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. 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 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.