High Resolution Tri-Frequency Synthetic Aperture Radar

R. Rincon
NASA Goddard Space Flight Center, United States

Keywords: High Resolution SAR, snow, X-band, Ku-band

A multi-frequency high resolution airborne synthetic aperture radar (SAR) system was recently developed at the NASA Goddard Space Flight Center for the estimation of snow water equivalent (SWE). The radar is part of the SWESARR (Snow Water Equivalent Synthetic Aperture Radar and Radiometer) instrument, an active passive microwave system specifically designed for the accurate estimation of SWE. The radar system is made up of three independent radar units that operate at 9.65 GHz, 13.6 GHz, and 17.25 GHz, respectively, with bandwidths up to 200 MHz. The three radars transmit vertically (V) polarized waveforms and receive returns with vertical and horizontal (VV, VH) polarizations (dual-polarization mode). The radar can operate at all three frequency bands simultaneously or interleaving them, depending on the application. The radar and the radiometer share an offset-fed reflector antenna, making the acquisition of collocated multi-frequency active/passive measurements possible. The reflector is fed by a “current sheet array” feed that operates from 8 to 40 GHz. The radar conducted its first test flights over the Grand Junction area in Colorado between December 1st and 4th, 2018. The area covered during the flights included the Grand Junction airport, where corner reflectors were deployed for radar calibration, and the Grand Mesa, a large flat top mountain which has been selected as a calibration site.