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- [Source: National Space Science Data Center, http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1966-040A-03 ]
Nimbus 2 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. 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. Some HRIR data were also transmitted in a real-time mode by the APT transmitter. The radiometer had an instantaneous field of view of about 0.5 deg, which at an altitude of 1100 km 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 it operated in the 3.5- to 4.1-micrometer region, the daytime pictures included 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. The experiment was a success, and good data were obtained until the HRIR tape recorder failed on November 15, 1966. The failure of the spacecraft recorder on July 26, 1966, necessitated the use of the HRIR recorder on a part-time basis to record selected telemetry data, which resulted in a 15% reduction of available HRIR data thereafter. For more detailed information of the experiment and the index of data, see Section 3 of "Nimbus II Users' Guide" (TRF B03406), "The Nimbus II High Resolution Infrared Data World Montage Catalog" (TRF B06578), and "The Nimbus II Data Catalog" (TRF B06573), available from NSSDC.
Group: Instrument_Details
Entry_ID: HRIR NIMBUS-2
Group: Instrument_Identification
Instrument_Category: Earth Remote Sensing Instruments
Instrument_Class: Passive Remote Sensing
Instrument_Type: Spectrometers/Radiometers
Instrument_Subtype: Radiometers
Short_Name: HRIR NIMBUS-2
Long_Name: High-Resolution Infrared Radiometer on NIMBUS-2
End_Group
Group: Associated_Platforms
Short_Name: NIMBUS-2
End_Group
Group: Spectral_Frequency_Information
Wavelength_Keyword: Infrared > Thermal
Spectral_Frequency_Coverage_Range: 3.5 μm - 4.1 μm
End_Group
Online_Resource: http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1964-052A-03
Online_Resource: http://atmospheres.gsfc.nasa.gov/nimbus/
Online_Resource: http://nasascience.nasa.gov/missions/nimbus
Group: Instrument_Logistics
Instrument_Owner: USA/NASA
End_Group
End_Group
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