|Spacecraft Proximity Operations Testbed (SPOT). This testbed is used by researchers to investigate robotics, control and computer vision technologies enabling spacecraft proximity operation tasks, such as inspection maneuvers, rendezvous and docking, robotic capture of a tumbling target, and on-orbit assembly of large structure. SPOT consists of two air-bearing spacecraft platforms operating in close proximity on a 2.4 m x 3.7 m granite surface. The use of air bearing on the platforms reduces the friction to a negligible level. Both platforms are actuated by a reaction wheel and compressed air expelled through miniature air nozzles, to provide three degree-of-freedom (3DOF) control authority. The motion of both platforms is measured in real-time through LEDs which are tracked by an eight-camera motion capture system. This provides highly accurate ground truth position and attitude data to evaluate the performance of the new robotics, control and computer vision technologies.
|GPS-Based Formation Flying Testbed. The centerpiece of this real-time hardware-in-the-loop (HIL) testbed is a GPS simulator that executes a real-time high fidelity simulation of the entire GPS satellite constellation, to compute, based on the actual spacecraft attitude and orbit, the GPS signals that would be received by a GPS receiver installed on that spacecraft. The radio frequency (RF) signal generator inside the GPS simulator then generates this signal and sends it to an actual GPS receiver connected to its RF output. The GPS receiver is connected to a target computer which runs the GN&C software and propagates the attitude and orbital dynamics, which are then used to steer the GPS simulator. Up to two GPS receivers can be connected to the GPS simulator, enabling the HIL validation of formation flying GN&C algorithms and related software.