Physics / mechanism
SAR satellites emit microwave pulses (typically 1–12 GHz, X- to L-band) toward Earth and record backscattered returns. By coherently combining returns across the satellite’s flight path, an aperture synthetically far larger than the physical antenna is formed — enabling sub-meter resolution from LEO. Key parameters: center frequency (determines penetration depth vs. resolution trade-off), pulse repetition frequency, chirp bandwidth (drives range resolution; ~300 MHz = ~0.5 m), and platform velocity/altitude. Current SoA: Capella Space and ICEYE operate X-band LEO constellations with ~0.5 m resolution and <1 hr revisit; Umbra reaches 25 cm in spotlight mode. Unlike optical systems, SAR is weather- and daylight-independent.
Competitive landscape
Optical EO satellites (Maxar, Planet) are the primary commercial substitute — lower cost per image, easier interpretation, but cloud-blocked and daylight-constrained. GNSS-R (Spire, HawkEye 360) overlaps in maritime/soil-moisture applications. Hyperspectral adds material-class discrimination optical can’t match but SAR can’t replicate either.
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.