Both were launched in 1978, with the Seasat mission lasting less than six months until failure of the primary bus.
It measured dual-polarized microwave radiances, at 6.63, 10.69, 18.0, 21.0, and 37.0 GHz, from the Earth's atmosphere and surface.
The final few months of operation were considerably fortuitous as they allowed the calibration of the radiometers and their products with the first results from the SSMI.
Jezek, K.C., C. Merry, D. Cavalieri, S.Grace, J. Bedner, D. Wilson and D. Lampkin 1991: Comparison between SMMR and SSM/I passive microwave data collected over the Antarctic Ice Sheet.
Byrd Polar Research Center, The Ohio State university, Columbus, OH., BPRC Technical Report Number 91-03, ISSN 1056-8050.