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Instrument: HRIR NIMBUS-1 : High-Resolution Infrared Radiometer on NIMBUS-1
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Associated Platforms

Spectral/Frequency Information
Wavelength Keyword: Infrared > Thermal
Spectral/Frequency Coverage/Range: 3.5 ?m - 4.1 ?m

Related Data Sets
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[Source: National Space Science Data Center, ]

The Nimbus 1 High-Resolution Infrared Radiometer (HRIR) was designed (1) to map the earth's nighttime cloudcover and thus to complement the daytime television (AVCS) coverage and (2) to measure the radiative temperatures of cloud tops and surface terrain. Mounted on the earth-oriented sensory ring, the radiometer measured thermal radiation in the 3.5- to 4.1-micrometer "window" region. The HRIR subsystem consisted of (1) an optical system, (2) an infrared detector (lead selenide photoconductive material), (3) electronics, (4) a magnetic tape recorder, and (5) a filter to minimize attenuation effects of water vapor and carbon dioxide. In contrast to the AVCS camera, no image was formed within the radiometer. The HRIR sensor merely transformed the received radiation into an electrical voltage, which was recorded on the tape recorder for subsequent playback when the satellite came within range of an acquisition station. The radiometer had an instantaneous field of view of about 1.5 deg, which at a nominal spacecraft altitude corresponded to a ground resolution of approximately 8 km at nadir. The radiometer was capable of measuring radiance temperatures from 210 to 330 K. Since the radiometer operated in the 3.5- to 4.1-micrometer region, the daytime pictures include reflected solar radiation in addition to the emitted surface IR radiation. However, the reflected solar radiation did not saturate the instrument, and a usable output was still obtained. In spite of a short operational lifetime (3.5 weeks), the HRIR system successfully demonstrated the feasibility of complete surveillance of surface and cloud features on a global scale during nighttime. With its improved spatial resolution, the radiometer yielded more detailed visual data on the structure of the Intertropical Convergence Zone (ITCZ) and on the formation of tropical storms and frontal systems than had previously been possible. For a more detailed description and an index of the data, see "Nimbus I High Resolution Radiation Data Catalog and Users' Manual" (TRF B04500), available from NSSDC.

Online Resources

Instrument Logistics
Instrument Owner: USA/NASA