Closed Loop Analysis of Space Systems (CLASS): A Modular Test System for CubeSat Development

Closed Loop Analysis of Space Systems (CLASS) is a small satellite test system engineered and maintained by the Laboratory for Advanced Space Systems at Illinois (LASSI), which is affiliated with the Department of Aerospace Engineering at the University of Illinois at Urbana-Champaign. CLASS is designed to be modular and user-friendly while providing the capability to perform accurate and reliable closed-loop tests. Commercial and academic CubeSat developers struggle to implement adequate testing procedures because of the relatively short development timeline and the sophisticated and inaccessible nature of space systems test equipment. Hardware-in-the-loop testing offers a convenient “test-as-you-fly, fly-as-you-test” validation and verification option for CubeSats. CLASS features a customizable real-time satellite orbital mechanics and rigid body dynamics simulation programmed to execute on the widely used Raspberry Pi 4 (RPi4). The RPi4 can be successfully interfaced with numerous hardware elements including the satellite’s actual flight computer, sensors, and actuators. In case certain flight hardware components, such as the magnetometers and gyroscopes, are not available for testing, CLASS offers the option of using Arduino boards that are programmed to emulate satellite sensors and actuators. Using CLASS, closed-loop tests on the Attitude Determination and Control System of CAPSat, a LASSI 3U CubeSat, proved to be critical for the validation of a state feedback Earth-pointing controller