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The Upper Atmosphere Research Satellite Program

The state of the ozone layer, which protects us from harmful solar ultraviolet radiation, has become the subject increasing concern to the science community and the general public. Studies such as the recent investigations into the annual stratospheric ozone depletion and recovery over Antarctica yield insight into the potential for change in the chemical composition of the upper atmosphere. these changes may have profound long-term effects on the habitability of the earth. 

In the 1976 NASA Authorization Act and the 1977 Clean Air Act amendments, Congress directed NASA to develop a research program for improving our understanding of the upper atmosphere, determining the methods needed to maintain its physical and chemical integrity, and developing techniques for early detection of detrimental changes in the ozone layer. Responding to these congressional directives, NASA developed a comprehensive upper atmospheric research program with the Upper Atmosphere Research Satellite (UARS) as its central element. 

Scheduled to be deployed by the Space Shuttle in the fall of 1991, UARS is the first satellite devoted solely to providing integrated, global measurements of the chemistry, dynamics, and energetics of the stratosphere, mesosphere, and lower thermosphere. The goals of the UARS program are to understand the mechanisms that control the structure and variability of the upper atmosphere, to determine the response of the upper atmosphere to natural and anthropogenic influences, and to define the role of the upper atmosphere in climate and climate variability. To accomplish these goals, the UARS program is designed specifically to investigate the photochemistry, dynamics, and energy inputs and losses in the upper atmosphere; the coupling between these three processes; and the coupling between the upper and lower atmospheres.

The timely launch of UARS is a central recommendation of the NASA Advisory Council's Earth System Sciences Committee. The UARS missions would be an integral part of the recommended long-range national plan to study the roles of the atmosphere, oceans, and biosphere as they relate to global change. 

The program will employ satellite measurements, theoretical investigation and model analysis, and correlative measurements to accomplish its scientific objectives. Nine instruments will be carried aboard UARS to provide accurate measurements of chemical species and temperature, energy input, and winds. A tenth instrument will make continuous measurements of the solar constant. 

The UARS program is international in scope, with contributors from U.S. and foreign universities, government agencies, and private industry groups. The science team, selected through NASA's Announcement of Opportunity process in 1981, consists of nine experimental investigative teams providing the instruments and ten theoretical investigative groups with specific areas of responsibility for data analysis and interpretation.

An extensive program of correlative measurements is being developed to confirm the results of UARS measurements and to establish confidence in modeling and data analysis techniques by direct comparisons to alternate experimental methods. Correlative measurements will be obtained from a variety of sources including balloons, sounding rockets, airborne systems, shuttle under flights, and instruments flown on other satellites.

A dedicated UARS data system will provide near-real-time access by all investigators to all UARS data. using this system, scientists will be unable to access raw and processed instrument data, as well as the resulting standardized and catalogued geophysical parameters, directly from the UARS central data handling facility through the use of remote analysis computers (RACs) located at institutions around the world. Scientists will also use their RACs fro interactive data processing and as a communications link among all investigators.

For additional information on the UARS program, contact Michael Luther, UARS Program Manager, Earth Science and Applications Division, Code EE, NASA Headquarters, Washington, D.C. 20546, USA.

[[Table]]
UARS Instruments

Energy Input Measurements: | SOLSTICE: Solar Stellar Intercomparison Experiment
SUSIM: Solar Ultraviolet Spectral Irradiance Monitor
PEM: Particle Environment Monitor
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Chemical Species and Temperature Measurements: | CLAES: Cryogenic Limb Array Etalon Spectrometer
ISAMS: Improved Stratospheric and Mesospheric Sounder
MLS: Microwave Limb Sounder
HALOE: Halogen Occulation Experiment
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Wind Measurements: | HRDI: High Resolution Doppler Interferometer
WINDII: Wind Imaging Interferometer
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Instrument of Opportunity: | ACRIM II: Active Radiometer Irradiance Monitor

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