The evolution of the SEASAT imaging radar

The paper describes the design parameters and development of a synthetic aperture radar for use on the SEASAT spacecraft. This imaging radar is designed to operate at altitudes of 800 km with an orbital inclination of 108 deg, a nominal resolution of 25 m, and a swath width of 100 km. The design evolved from planetary imaging radar studies conducted over many years where an L-band imaging radar was developed and tested on aircraft flights as a prototype system to map the surface of Venus. A solid-state transmitter is used where the pulse repetition frequency is a function of altitude and will be about 2kHz for a 12-m long antenna. The receiver consists of the receiver protector, input filters, the gain control, and the RF amplifier. The ground station uses the standard NASA receiver with a 10-m antenna. The correlator, either optical or digital, must be able to compensate for the pitch and yaw variations of the spacecraft as well as the inherent effective yaw caused by the rotation of the earth, and extract the range curvature and range walk effects.