HRIR Nimbus-3
change note: 2015-05-12 13:19:52.0 [saritz] Changed Nimbus to mixed case. update AltLabel (High-Resolution Infrared Radiometer on Nimbus-3); update PrefLabel (HRIR Nimbus-3);
in scheme: instruments
definition: [Source: National Space Science Data Center, http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1969-037A-02 ] The Nimbus 3 High-Resolution Infrared Radiometer (HRIR) was designed (1) to map the earth's nighttime cloud cover and thus to complement the daytime television (AVCS) coverage and (2) to measure the radiative temperatures of cloud tops and surface terrain. The Nimbus 3 HRIR was a modified version of previous experiments on Nimbus 1 and 2. It used a dual band-pass filter which transmitted reflected solar radiation in the 0.7- to 1.3-micrometer band as well as emitted thermal radiation in the 3.4- to 4.2-micrometer band. By detecting reflected solar radiation in the 0.7- to 1.3-micrometer band, the radiometer could also map the earth's cloud cover during the daytime. Radiant energy from the earth was collected by a flat scanning mirror inclined at 45 deg to the optical axis. The mirror rotated at 48 rpm and scanned in a plane normal to the spacecraft velocity. The radiation reflected from the scan mirror was chopped at the focus of a 10.2-cm f/1 modified Cassegrain telescope. The modulated energy was then refocused on a lead selenide detector cell that transformed the received radiation into an electrical output. The output was amplified and recorded on magnetic tape for subsequent playback to a ground acquisition station. Using the direct readout infrared radiometer (DRIR) system, nighttime and daytime data could be transmitted by the real-time transmission system (RTTS) to ground APT stations. A ground resolution of 8.5 km could be obtained at nadir. The HRIR measured radiance temperatures between 210 and 330 deg K to a general accuracy of 1 deg K. For a more detailed description, see Section 3 of "The Nimbus III User's Guide" (TRF B03409). The experiment was successful until August 1969, when noise in the tape recorder system gradually reduced the quality of the data. Routine processing of HRIR data was terminated after January 31, 1970. All experiment…
type: Concept

Radiometers
type: Concept