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Visible Infrared Spin-Scan Radiometer

NSSDC ID: 1975-011A-04
Mission Name: SMS 2

Description

The visible infrared spin-scan radiometer (VISSR) flown on SMS 2 provided day/night observations of cloud cover and earth/cloud radiance temperature measurements from a synchronous, spin-stabilized, geostationary satellite for use in operational weather analysis and forecasting. The two-channel instrument was able to take both full and partial pictures of the earth's disk. The infrared channel (10.5 to 12.6 micrometers) and the visible channel (0.55 to 0.70 micrometer) used a common optics system. Incoming radiation was received by an elliptically shaped scan mirror and collected by a Ritchey-Chretien optical system. The scan mirror was set at a nominal angle of 45 deg to the VISSR optical axis, which was aligned parallel to the spin axis of the spacecraft. The spinning motion of the spacecraft (approximately 100 rpm) provided a west-to-east scan motion when the spin axis of the spacecraft was oriented parallel with the earth's axis. The latitudinal scan was accomplished by sequentially tilting the scanning mirror north to south at the completion of each spin. A full picture took 18.2 min to complete and about 2 min to retrace. During each scan, the field of view on the earth was swept by a linear array of eight visible-spectrum detectors, each with a ground resolution of 0.9 km at zero nadir angle. A mercury-cadmium-telluride detector sensed the infrared portion of the spectrum with a horizontal resolution of approximately 8 km at zero nadir angle. The infrared portion of the detector measured radiance temperatures between 180 and 315 deg K with a proposed sensitivity between 0.4 and 1.4 deg K. The VISSR output was digitized and transmitted to the National Oceanographic and Atmospheric Administration (NOAA) Command and Data Acquisition Station (CDA), Wallops Island, Va. There, the signal was fed into a "line stretcher," where it was stored and time-stretched for transmission back to the satellite at reduced bandwidth for re-broadcast to data utilization stations (DUS). The VISSR data were handled by NOAA, and the majority of data were archived by the Satellite Data Service Division, National Climatic Center, NOAA, Washington, D.C. Limited amounts of research-oriented data were collected by NASA and are maintained at NSSDC.

Alternate Names

  • VISSR

Facts in Brief

Mass: 69.7 kg
Power (avg): 25.5 W

Funding Agency

  • NOAA National Environmental Satellite Service (United States)

Discipline

  • Earth Science: Atmospheric Dynamics

Additional Information

Questions or comments about this experiment can be directed to: Coordinated Request and User Support Office.

 

Personnel

NameRoleOriginal AffiliationE-mail
Mr. William E. ShenkOther InvestigatorNASA Goddard Space Flight Center 
Principal InvestigatorNOAA National Environmental Satellite, Data and Information Service 
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