The precipitation radar (PR) onboard the Tropical Rainfall Measuring Mission (TRMM) satellite is the first spaceborne radar to measure precipitation from space. The PR, operating at 13.8 GHz, is a 128-element active phased array that allows a fast and sophisticated cross-track scanning over a swath width of 215 km with a cross-range spatial resolution of about 4.3 km. The PR has a minimum detectable rain rate of 0.5 mm/h with range resolution of 250 m. In order to achieve a reliable and accurate rain echo data for three years mission life, functions for internal and external calibrations are implemented. Through a series of PR flight-model tests on the ground and an initial checkout just after the TRMM launch, it is confirmed that the PR functions properly and meets the performance requirements to quantitatively measure three-dimensional (3D) precipitation distribution from space.

The spaceborne synthetic aperture radar (SAR) to be launched on the Japanese Earth Resources Satellite-1 is described. The SAR is operated in the L-band. The mission is mainly dedicated to geological applications. The ground resolution of the processed image is designed as 18 m and the off-nadir angle required to meet geological applications is 35 degrees . The design and performance of the key system parameters are discussed, along with the reasons for choosing such design parameters. The antenna is a thin-flat-foldable configuration that has a 11.9-m by 2.2-m aperture when extended in orbit. The transmitter, receiver, and signal processor are all of the solid-state type to achieve high reliability of operation. They transmit an 1100-W peak (minimum) chirp pulse and receive the return echos and process the echo signals into in-phase and quadrature data streams.>