Imaging Spectrometers/Radiometers
type: Concept

ESMR
type: Concept
change note: 2016-05-10 14:38:21.0 [saritz] update AltLabel (Electrically Scanning Microwave Radiometer);
change note: 2016-05-10 14:37:49.0 [saritz] update AltLabel (Electically Scanning Microwave Radiometer);
definition: The Nimbus 6 Electrically Scanning Microwave Radiometer (ESMR) measured the earth's microwave emission to provide the liquid water content of clouds, the distribution and variation of sea ice cover, and gross characteristics of land surfaces (vegetation, soil moisture, and snow cover). The two-channel scanning radiometer operated in a 250-MHz band centered at 37 GHz. One channel was used to measure the vertical polarization and the other measured the horizontal polarization. The antenna beam array, a 90- by 20- by 12-cm box-like structure, was mounted on top of the spacecraft sensory ring and was pointed in the direction of the spacecraft's forward motion and tilted down 45 deg from the satellite antenna axis. The antenna beam scanned the earth in 71 discrete steps for various angles extending up to 35 deg on either side of the orbital plane. The deduced brightness temperatures were expected to be accurate to within 3-5 deg K. Spatial resolution was 20 km in the cross-track direction and 45 km in the direction parallel to the subpoint track. For a more detailed description, see Section 5 of "The Nimbus 6 User's Guide" (TRF B23261), available from NSSDC. The ESMR performance was satisfactory until September 15, 1976, when the horizontal channel output was zero due to a failure of the Ferrite-Dicke switch. Selected ESMR images were presented in "The Nimbus 6 Data Catalog" (TRF B26731), also available from NSSDC. Additional information available at "http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1975-052A&ex=3" [Summary provided by NASA]
in scheme: instruments