Digital twin of thermal controls and design for NISAR

NASA-ISRO Synthetic Aperture Radar (NISAR) is a joint project between NASA and Indian Space Research Organization (ISRO). NISAR consists of both L-Band and S-band synthetic aperture radar (SAR). JPL has been developing and integrating L-band radar, Ka-band communication subsystem, GPS receiver, solid-state recorder, payload-data subsystems with the spacecraft system. ISRO would provide and integrate spacecraft bus, S-band radar, data handling, propulsion/attitude control. In addition to L and S band electronics, NISAR is equipped with large solar array, multi-stage deployable structural components with hinge/actuator mechanism and a wide range radar antenna reflector. This makes the spacecraft a unique example of collaborative engineering development with complex thermal controls system. The spacecraft requires heating at different structural and electronics components by using mechanically controlled heaters. Multistage deployment of the spacecraft during its initial lifecycle requires to comply various thermal requirements at both extreme cold and hot conditions. With so many moving parts and complex passive thermal controls system, it is very important to capture heat transfer mechanism accurately. Hence, in this paper primary focus has been given on thermal modeling and analysis of NISAR using a combination of tools. Discussion has been done to demonstrate an efficient approach to correlate and validate the model with support from thermal vacuum test (TVAC). Significance of digital twin would be established through exercising orbital validation and post-launch flight predictions using a robust thermal model. This article would be able to provide a clear methodology for digital twin of a generic large-scale low earth orbit satellite in its various life cycle for future missions.