Measurement of Air Pollution from Satellites
Project DescriptionThe MAPS experiment measures the global distribution of carbon monoxide (CO) in the free troposphere. Because of MAPS' previous flights on board the Space Shuttle, Earth system scientists now know that carbon monoxide concentrations in the troposphere are highly variable around the planet, and that widespread burning in the South American Amazon region and the African savannas are major global sources of carbon monoxide in the troposphere.
MAPS consists of an electro-optical sensor, an electronics module, a digital tape dsata record, and an aerial camera. The 92 kg MAPS package is 90 cm long, 76 cm wide, and 58 cm high. The hardware is coupled to a cold plate and mounted on the Multi-Purpose Experiment Support Structure (MPESS) which is installed at the forward end of the cargo bay. The electro-optical sensor incorporates two gas cells, one containing 350 hPa of CO and another containing 149 hPa of N2O; their corresponding detectors; a direct radiation detector; and external balance and gain check system; and an internal balance system.
The electronics module of MAPS consists of the signal processors, the balance system controls, and the circuitry required to operate the system. The space-qualified Lockheed Mark V tape recorder records the experiment data at an average rate of 43 bits per second. The Flight Research 35-mm aerial camera, equipped with a light sensor, photographs the groundtrack during sunlit portions of the orbit.
When the Space Shuttle attains Earth-viewing position, the MAPS instrument pallet (shown in the lower right hand corner) power is supplied and the instrument is commanded on. After a 30-minute warmup, the instrument executes a balance cycle and gain check before it begins to take data. MAPS continues to operate throughout the Earth- observing period. Balance and gain check recur at 12-hour intervals or upon command from the Earth-based experiment team. The three instrument signals (two difference channel signals and one direct radiometer signal) and various "housekeeping" signals are digitized, formatted, and stored on the experiment's tape recorder. These signals are also telemetered to the ground via the Space Shuttle telemetry system. When the Payload Operations Control Center receives the telemetered signals, the MAPS operations team evaluates the instrument operation and processes the signals to provide "quick look" carbon monoxide mixing ratios along the shuttle ground track.
The aerial camera mounted next to the MAPS electro-optical head provides information on cloud cover and terrain over which the data are gathered. Operation of the camera and tape recorder can be inhibited during periods when the Shuttle is not in proper Earth-viewing attitude.
The MAPS experiment is conducted by a team led by Principal
Investigator Henry G. Reichle, Jr. of NASA's Langley Research
Center. The MAPS science team, which advises the experiment team and
assists in evaluation of MAPS data, consists of V. Connors, NASA
Langley Research Center; W. Hesketh, Space Tec Ventures;
P. Kasibhatla, Georgia Institute of Technology; V. Kirchoff, Instituto
Nacional de Pesquisas Espaciais (INPE), Brazil; J. Logan, Harvard
University; R. Newell, Massachusetts Institute of Technology;
R. Nicholls, York University, Canada; L. Peters, University of
Kentucky; W. Seiler, Fraunhofer-Institut Fur Atmospharische
Umweltforschung, Germany; H. Wallio, NASA Langley Research Center.
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[Summary provided by NASA]