Development of a Hardware-In-The-Loop Testbed for Rotating Synthetic Aperture Telescopes

CubeSats and small satellites offer the opportunity to deliver scientific payloads into space at a much cheaper cost and faster cadence than traditional large-scale spacecraft. While the mass and cost budgets allocated to science payloads on CubeSats and small satellites inherently decreases compared to traditional large-scale spacecraft, it is undesirable to sacrifice measurement quality. This has resulted in a demand to optimize the areal cost of imaging payloads while maintaining, or even improving, measurement performance. Rotating synthetic aperture (RSA) telescopes respond to this demand by employing a rectangular strip mirror that is rotated about the imaging system's principal optical axis. RSA telescopes use only a fraction of the volume of an equivalent-sized circular aperture and offer the potential to super-resolve portions of the complete image. However, this concept requires more complex and dynamically active guidance, navigation, and control (GNC) algorithms for precisely pointing and tracking targets. This paper describes the development of a hardware-in-the-loop testbed for testing GNC algorithms designed for an RSA telescope concept. The testbed includes typical spacecraft sensors and actuators, such as reaction wheels, an IMU, and a star tracker surrogate camera. The interfaces between algorithms, sensors, and actuators is handled using the Robot Operating System due to its flexibility for prototyping embedded systems. Performance characterizations of each subsystem are presented in the context of a nominal RSA mission operating environment. The presented results establish subsystem performance metrics to be used in closed loop tests for nominal RSA observing maneuvers.