NSSDCA ID: 1970-025A-04
Mission Name: Nimbus 4The Nimbus 4 Satellite Infrared Spectrometer (SIRS) experiment was designed to determine the vertical temperature and water vapor profiles of the atmosphere by using a Fastie-Ebert fixed-grating spectrometer. The instrument measured the infrared radiation (11 to 36 micrometers) emitted from the earth and its atmosphere in 13 selected spectral intervals in the carbon dioxide and water vapor bands plus one channel in the 11-micrometer atmospheric window. The main components of the spectrometer consisted of (1) a plane, light-collecting mirror to provide one fixed and two variable earth-viewing angles, (2) a rotating chopping mirror that served alternately to collect space radiation and earth radiation, (3) a 2.5-in. diffraction grating with 1250 lines per inch, (4) 14 slits with associated interference filters, (5) 14 thermistor bolometers, and (6) a blackbody source for calibration purposes. The SIRS used a scan mirror to observe 12.5 deg to either side of the subsatellite track. The field of view directly below the SIRS was approximately 215 sq km. The carbon dioxide band radiation data were transformed to a temperature profile by a mathematical inversion technique. By a similar technique, this information could then be combined with the water vapor band data to obtain a water vapor profile. The 11-micrometer atmospheric window data yielded surface and/or cloudtop temperatures. For a complete description of the SIRS experiment, see Section 5 of "The Nimbus IV User's Guide" (TRF B06861), available from NSSDC. The SIRS experiment performed normally for several months after launch but began to deteriorate in early 1971. Problems in the SIRS instrument calibration after April 1971, in addition to spacecraft yaw problems, significantly reduced the number of useful soundings obtained. The archival data were produced through April 8, 1971. The experiment operated on a limited time basis until March 6, 1973, when it was placed operationally off. Both NSSDC and SDSD have data.
Mass: 31.5 kg
Power (avg): 30 W
Questions and comments about this experiment can be directed to: Coordinated Request and User Support Office
Name | Role | Original Affiliation | |
---|---|---|---|
Mr. D. T. Hilleary | Other Investigator | NOAA National Environmental Satellite, Data and Information Service | |
Dr. David Q. Wark | Principal Investigator | NOAA National Environmental Satellite, Data and Information Service |