Closed Loop Analysis of Space Systems (CLASS) a modular test system for small satellite verification and validation

Closed Loop Analysis of Space Systems (CLASS) is a modular, closed-loop satellite test system developed at the Laboratory for Advanced Space Systems at Illinois (LASSI). This thesis presents the technical details of the initial engineering development stages of CLASS. The CubeSat concept is now twenty-one years old, yet a significantly high number of mission failures (i.e., 33% for commercial developers and 55% for academic developers) are still being experienced. By employing hardware-in-the-loop testing driven by closed-loop simulations, critical aspects of validation and verification can be achieved with improved fidelity in an attempt to enhance the mission success rate of CubeSats. CLASS is composed of real-time satellite orbital mechanics and rigid body dynamics simulations executing on a Raspberry Pi 4. The satellite attitude dynamics, orbital mechanics, and space environment properties are computed by the CLASS software reliably and rapidly. It has the ability to interface with the satellite’s flight computer, sensors, and actuators. If individual flight hardware elements are not available, as may be the case early in a CubeSat’s integration flow, emulators for such components as magnetometers and gyroscopes, executing on Arduino boards, are easily configurable by the user to match the behavior and properties of the actual hardware. The theory behind the dynamic simulation programmed in CLASS is presented. CLASS updates the attitude of the satellite and environmental properties every five milliseconds and the orbital elements every sixty seconds. The performance and validity of the simulation algorithms are also presented. Finally, the results from a closed-loop test for the attitude determination and control system of one of the LASSI CubeSats, CAPSat, is demonstrated. CLASS is playing a critical role in the development of CAPSat by validating the design of a state feedback controller for nadir pointing, identifying hardware limitations, and enabling the correction of software errors. CLASS will serve as a general purpose and easily configurable test system for all CubeSats and space systems developed at the University of Illinois