HIRS+SCAMS/Nimbus6 Merged Level-2 Radiation, Temperature and Humidity Sounding Data for GARP V001 (HIRSSCAMSN6L2GARP)

HIRS was a multi-channel filter radiometer with a Cassegrain telescope before the chopper assembly. The instrument scanned in the cross track direction with 21 scans on each side of the subtrack point with about 30 km x 55 km resolution at nadir. HIRS measured radiances primarily in five spectral regions: (1) seven channels near the 15-micrometer CO2 absorption band, (2) two channels (11.1 and 3.7 micrometers) in the IR window, (3) two channels (8.2 and 6.7 micrometers) in the water vapor absorption band, (4) five channels in the 4.3-micrometer band, and (5) one channel in the visible 0.69-micrometer region.

The SCAMS experiment on Nimbus-6 was a follow on to the successful Nimbus-5 NEMS experiment. SCAMS continuously monitored emitted microwave radiation at frequencies of 22.235, 31.65, 52.85, 53.85 and 55.45 GHz. The three channels near the 5.0-mm oxygen absorption band were used primarily to deduce atmospheric temperature profiles.

The two channels near 10 mm permitted water vapor and cloud water content over calm oceans to be estimated separately. The instrument, a Dicke-superheterodyne type, scanned +/- 45 degrees normal to the orbital plane with a 10 degree field of view. The three oxygen channels shared common signal and reference antennas.

Both water vapor channels had their own signals and reference antennas. The absolute rms accuracy of the oxygen channels was better than 2 Kelvin and that of the water vapor channels better than 1 Kelvin. The HIRS Principal Investigator was Mr.

W. L. Smith from the NOAA National Environmental Satellite Service. The SCAMS Principal Investigator was Prof. David H. Staelin from MIT.

The Nimbus-6 HIRS and SCAMS merged data are available from August 17, 1975 through March 4, 1976. These data were previously archived at NASA NSSDC under the entry ID ESAD-00017 together with the merged retrieval data set.