Scanning Multichannel Microwave Radiometer (SMMR)

Description

The primary purpose of the Scanning Multichannel Microwave Radiometer (SMMR) experiment was (1) to provide all-weather measurements of ocean surface temperature and wind speed, and (2) to obtain integrated liquid water column content and atmospheric water vapor column content for path length and attenuation corrections to the ALT and SASS observations. Microwave brightness temperatures were observed with a 10-channel (five-frequency dual polarized) scanning radiometer operating at 0.8-, 1.4-, 1.7-, 2.8-, and 4.6-cm wavelengths (37, 21, 18, 10.7, and 6.6 GHz). The antenna was a parabolic reflector offset from nadir by 0.73 rad. Motion of the antenna reflector provided observations from within a conical volume along the ground track of the spacecraft. The SMMR had a swath width of about 600 km and the spatial resolution ranged from about 22 km at 37 GHz to about 100 km at 6.6 GHz. The absolute accuracy of sea surface temperature obtained was 2 K deg with a relative accuracy of 0.5 K deg. The accuracy of the wind speed measurements was 2 m/s for winds ranging from 7 to about 50 m/s. The same experiment was flown on Nimbus 7. A more detailed description can be found in E. Njoku, et al., "The Seasat Scanning Multichannel Microwave Radiometer (SMMR): instrument description and performance," IEEE J. Oceanic Eng., v. OE-5, pp. 100-115, 1980. The instrument operated continuously in orbit from July 6, 1978 for a period of 95 days, until the spacecraft failed on October 10, 1978. Data are available from SDSD.