Medium-Resolution Infrared Radiometer

Description

The Nimbus 2 Medium-Resolution Infrared Radiometer (MRIR) experiment measured the intensity and distribution of electromagnetic radiation emitted by and reflected from the earth and its atmosphere in five selected wavelength intervals from 0.2 to 30 micrometers. Data for heat balance of the earth-atmosphere system were obtained, as well as measurements of water vapor distribution, surface or near-surface temperatures, and seasonal changes of stratospheric temperature distribution. The five wavelength regions were (1) the 6.4- to 6.9-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- to 16-micrometer band, which covered the 15-micrometer carbon dioxide absorption band, (4) the 5- to 30-micrometer band, which measured the emitted long-wavelength infrared energy for heat budget purposes, and (5) the 0.2- to 4.0-micrometer channel, which yielded information on the intensity of reflected solar energy (albedo). 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 55 km could be obtained. The MRIR experiment was successful, and good data were obtained from launch until the recorder failed on July 29, 1966. For more detailed information of the experiment and the index of data, see Section 4 of "Nimbus II Users' Guide" (TRF B03406), "The Nimbus II Medium Resolution Infrared Pictorial Data Catalog" (TRF B06580), and "The Nimbus II Data Catalog" (TRF B06573), available from NSSDC.