Instrument commissioning timeline for NASA-ISRO Synthetic Aperture Radar (NISAR)

The NASA-ISRO Synthetic Aperture Radar (NISAR) is a joint collaboration between NASA and India's national space agency, the Indian Space Research Organization (ISRO). This Earth-orbiting radar mission, which will be launched from Sriharikota (India) in December 2021 in a near-polar, sun-synchronous orbit, is designed to systematically and globally study solid Earth, ice masses, and ecosystems. Following NISAR's launch, the first 90 days will be dedicated to performing `in-orbit checkout', or the `commissioning' period, during which there will be a step-by-step buildup in capability to full observatory operations. Activities performed during commissioning will be aimed at demonstrating the full functionality of the radar instruments (L-band and S-band), the reflector antenna, spacecraft and flight systems, characterizing and confirming their nominal performance within specifications. All ground systems and infrastructure, including Ground Data Systems (GDS), Science Data Systems (SDS) and Mission Operations Systems (MOS), as well as the compatibility of all system interfaces, will be tested and validated. Calibration strategies for monitoring instrument stability will be tested during initial instrument calibrations. The scheduling of these initial instrument calibration activities takes into account factors like the satellite orbit and attitude after launch, requirements on specific instrument configurations for operation, required ground targets and the corresponding number and frequency of overflight times during a satellite repeat cycle (12 days). A timeline for NISAR instrument checkout that takes into account these factors and constraints is presented in this paper.