NASA-ISRO Synthetic Aperture Radar (NISAR): Towards Observatory-level Integration and Testing

The NASA-ISRO Synthetic Aperture Radar (SAR), or NISAR, is an Earth-observing dual-band radar mission being jointly developed by NASA and the Indian Space Research Organization (ISRO). As a pathfinder for NASA's Earth System Observatory (ESO), NISAR will make global measurements of land surface changes from its near-polar 12-day repeating orbit, for integration into Earth system models. NISAR measurements will provide scientists with a means of understanding globally, spatially- and temporally-complex solid-earth, cryosphere and ecosystem phenomena, and provide societally-relevant data that will enable investments to protect human life and property. The radar payload system, consisting of a NASA-developed L-band SAR, an ISRO-developed S-band SAR, a deployable 12m radar antenna and a high-capacity data handling and instrument control system, has been fully integrated as a flight system and has undergone extensive testing, from 2020 through 2022. This testing has included acoustic and sine-vibration dynamics and launch-configuration thermal vacuum tests, as well as the first Mission Scenario Tests (MST's) of the payload flight hardware and software with flight-like commanding. Prior to the 2023 delivery of the radar payload to ISRO's U. R. Rao Satellite Centre (URSC), the radar payload will undergo a science configuration (sans radar antenna) thermal vacuum test and a final round of MSTs focusing on joint operation of the two radars and instrument controller fault protection testing. Once at URSC, the radar payload will undergo system integration to the ISRO satellite mainframe bus, and observatory-level testing in Bangalore. Other major systems are also being readied for delivery by ISRO: the satellite bus, ground stations, science data processing systems and mission operations including Geosynchronous Satellite Launch Vehicle (GSLV) Mark II launch from ISRO's Satish Dhawan Space Centre (SDSC) launch complex. Four planned NASA Ka-band ground stations required to downlink 37 Tb/day average daily NISAR data volume are on track to be operational by 2023, as well. NASA and ISRO have made significant refinements to the observatory integration & test plans, to address the special test needs of this very complex instrument system. A series of operational readiness tests have been planned to demonstrate the readiness of the joint mission systems to support operations.