The SAR instrument on board JERS-1 measured in L-band (1.275 GHz) in HH polarisation.

The instrument consisted of the following subsystems: antenna, transmitter/receiver, and signal processor. The SAR antenna was composed of eight 2.2 m x 1.5 m panels, measuring 2.2 m x 11.9 m in total. A honeycomb sandwich structure was used.

The signal processor performed several functions. First, it performed the A/D conversion of I and Q video signals from the transmitter/receiver. Secondly, after formatting the A/D converted I and Q data plus other data necessary for processing on the ground, it transmitted the I and Q channel data. Finally, it controlled itself and the transmitter/receiver based on commands received from the ground stations.

The range of incidence angles within a typical image was fixed at between 32° at near range and 38° at far range. SAR transmitted 1500 pulses a second from the antenna with a mean off-nadir angle of 35° to right side of satellite. The L-band SAR of JERS-1 also demonstrated two-pass SAR-interferometry, for change detection.