Imaging geometry of a SAR acquisition. Due to the spacecraft velocity vs/c the pulses illuminate a swath parallel to the satellite track. The footprint of a single pulse is indicated by the dark-shaded area. The total SAR image starts in azimuth at the “early azimuth” time, and lasts until the “late azimuth” time. In range direction, it covers an interval from “near range” to “far range,” which corresponds to the light shaded area in the ground range.
SAR pulse transmitting and receiving mode. For the ERS configurations, a pulse emitted at position 1 is received between positions 10 and 11. The time interval between the pulse transmission is the PRF. Therefore, the spacecraft moves approximately 40m between transmitting and receiving pulse.