NISAR's Unique Challenges and Approach to Robust JPL/ISRO Joint Operations

The NASA-ISRO Synthetic Aperture Radar (NISAR) mission is the first major collaboration between NASA and the Indian Space Research Organisation (ISRO), and will return an unprecedented amount of science data (~5,000 terabytes during its prime mission). From a mean altitude of ~750km, the Observatory will use two distinct bands of SAR to provide detailed insight into the evolution and state of Earth's crust, including the abatement of glaciers, ecosystem changes, and natural and man-made disasters, such as earthquakes, hurricanes, and oil spills. JPL will provide NISAR's L-band SAR, GPS receivers, a payload data system, solid state recorder, and a high-rate Ka-band telecom system. ISRO will provide the satellite bus and an S-band SAR. With both JPL and ISRO providing key flight components, NISAR operations will be inherently interactive. This, combined with the substantial geographic and time differences, brings a unique set of operational challenges. How should the project weigh each Center's responsibility for operation of their specific flight and ground components against the need for both JPL and ISRO to maintain situational awareness of the Observatory and Ground System? In preparation for launch in January 2022, the NISAR Mission System has worked to find the right balance between inter-Center collaboration and each Center's individual responsibilities. With the goal of minimizing the complexity of operational interfaces, NISAR must still perform - integrated long and short-term science planning, - coordinated commanding necessary to execute joint SAR observations, - coordinated commanding necessary to carry out all of the Ka-band downlinks, and - anomaly response and recovery. This paper describes NISAR's approach to addressing each of these challenges to joint operation of the Observatory.