The Nasa-Isro Sar (Nisar) Mission Dual-Band Radar Instrument Preliminary Design

The National Aeronautics and Space Administration (NASA) in the United States and the Indian Space Research Organisation (ISRO) are developing a synthetic aperture radar (SAR) mission to map Earth's surface every 12 days, known as the NASA-ISRO SAR (NISAR) Mission. NISAR has completed its preliminary design and successfully passed its Preliminary Design Review in June 2016. This paper describes the radar instrument design, engineering model hardware development status, test results, and the plans for future maturation toward the Critical Design Review in late 2018. NISAR has two radars sharing a mechanical structure and reflector, one operating at L-band (24 cm wavelength) and the other at S-band (10 cm wavelength). To achieve wide-swath observations at both wavelengths, NISAR is designed as a reflector-feed system where the feed aperture elements are individually sampled to allow a scan-on-receive capability. In the partnership, NASA provides the instrument structure for both L-and S-band electronics, the L-band electronics, the reflector and associated boom, and an avionics payload to interface with the radar including a solid-state data recorder, high-rate Ka-band telecommunication link, and a GPS receiver. In addition to providing the spacecraft and launch vehicle for the mission partnership, ISRO is also providing S-band radar electronics, and an additional high-rate Ka-band telecom package. This paper will describe aspects of this technically and logistically complex international instrument and mission development, one that requires careful definition of interfaces, tracking of resources, joint analysis of designed capabilities, and detailed integration and test plans.