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Medium-Resolution Infrared Radiometer

NSSDCA ID: 1969-037A-05

Mission Name: Nimbus 3
Principal Investigator:Mr. Andrew W. McCulloch


The Nimbus 3 Medium-Resolution Infrared Radiometer (MRIR) experiment measured the intensity and distribution of the electromagnetic radiation emitted by and reflected from the earth and its atmosphere in five selected wavelength intervals from 0.2 to 23 micrometers. Data on the heat balance of the earth-atmosphere system were obtained as well as water vapor distribution data, surface or near-surface temperatures, and data on seasonal changes of stratospheric temperature distribution. The five wavelength regions were (1) the 6.5- to 7.0-micrometer channel, which covered the 6.7-micrometer water vapor absorption band, (2) the 10- to 11-micrometer band, which operated in the atmospheric window, (3) the 14.5- to 15.5-micrometer band, which covered the 15-micrometer carbon dioxide absorption band, (4) the 20- to 23-micrometer channel, which covered the spectral region containing the broad rotational absorption bands of water vapor, and (5) the 0.2- to 4.0-micrometer channel, which yielded information on the intensity of reflected solar energy. Radiant energy from the earth was collected by a flat scanning mirror inclined at 45 deg to the optical axis. The mirror rotated at 8 rpm and scanned in a plane perpendicular to the direction of motion of the satellite. Each of the five channels contained a 4.33-cm diameter folded telescope with a 2.8-deg field of view and a thermistor bolometer. The collected energy was modulated by a mechanical chopper to produce an ac signal. The signal was then amplified and recorded on magnetic tape for subsequent playback to a ground acquisition station. At a satellite altitude of 1100 km, a horizontal resolution of 45 km was obtained. The MRIR experiment was successful, in spite of a telemetry conflict that caused the experiment to be periodically turned off. During August and September 1970 (hurricane season), the MRIR was on essentially full time to cover the area from the equator to 70 deg N and from 10 deg E to 100 deg W. On September 25, 1970, the satellite's rear horizon scanner failed, making it impossible to determine where the MRIR sensor was pointing. The experiment was operated periodically until January 22, 1972, when all spacecraft operations were terminated.

Alternate Names

  • MRIR
  • Nimbus3/MRIR

Facts in Brief

Mass: 9.5 kg
Power (avg): 7.4 W

Funding Agency

  • NASA-Office of Space Science Applications (United States)


  • Earth Science: Atmospheric Dynamics
  • Earth Science: Land Surface Processes

Additional Information

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



NameRoleOriginal AffiliationE-mail
Mr. Andrew W. McCullochPrincipal InvestigatorNASA Goddard Space Flight Center
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