Spaceborne
SAR Metrics 
"First-of-a-kind" Scientific and Technological Advances
Since the launch of SeaSAT in 1978, the spaceborne SAR program at JPL has followed a path of first-of-a-kind innovation, as measured through a metric called "radar capability." SeaSAT was a single frequency, single polarization system. With the advent of the age of the Space Shuttle, when NASA requested that large instruments design for the shuttle, JPL developed the SIR-A, B, and C series of instruments that were unique: the first shuttle-based SAR (SIR-A), the first multi-incidence angle SAR (SIR-B), and the first fully polarimetric, multi-frequency SAR (SIR-C). The Shuttle Radar Topography Mission was the next level of innovation, as the first fixed-baseline radar interferometer in space, the first ScanSAR interferometer in space, and the first mission to map the entire Earth interferometrically twice in 10 days (within + 60 degrees of latitude). This continued innovative exploitation of electromagnetic parameter space has led to a measurable increase in usage of NASA spaceborne radar data by the science community. In addition to these general metric improvements, area coverage has widened over the years, and resolutions have become finer.
The two planetary radars are each first-of-a-kind. Magellan was the first SAR orbiting another planet, the first S-band spaceborne SAR, and the first burst-mode spaceborne SAR. Cassini Radar continued in innovation as the first multi-beam spaceborne SAR, and the first Ku-band spaceborne SAR. The improvement in scientific knowledge afforded by these systems is immense.
Paul Rosen and Scott Hensley
April 2003