SATSIM—A real-time multi-satellite simulator for test and validation in formation flying projects

The satellite simulator SATSIM was developed during the experimental PRISMA multi-satellite formation flying project and was primarily aimed to validate the Guidance, Navigation and Control system (GNC) and the on-board software in a simulated real-time environment. The SATSIM system has as a main feature the ability to simulate sensors and actuators, spacecraft dynamics, intra-satellite communication protocols, environmental disturbances, solar illumination conditions as well as solar and lunar blinding. The core of the simulator consists of MATLAB/Simulink models of the spacecraft hardware and the space environment. The models run on a standard personal computer that in the simplest scenario may be connected to satellite controller boards through a CAN (Controller Area Network) data bus. SATSIM is, in conjunction with the RAMSES Test and Verification system, able to perform open-loop, hardware-in-the-loop as well as full-fledged closed-loop tests through the utilisation of peripheral sensor unit simulators. The PRISMA satellites were launched in June 2010 and the project is presently in its operational phase. This paper describes how a low cost but yet reliable simulator such as the SATSIM platform in different configurations has been used through the different phases of a multi-satellite project, from early test of onboard software running on satellite controller boards in a lab environment, to full-fledged closed-loop tests of satellite flight models.