ESA GNC Conference Papers Repository
End-to-end simulation and verification of GNC and robotic systems considering both space segment and ground segment
The rendezvous and docking/berthing (RvD/B) phase is one of the most complex and critical parts of future on-orbit servicing and debris removal missions. Especially the operations during the final approach (separation distance < 20m) have to be verified and tested in detail. Such tests involve the on-board GNC and docking/capturing systems, the communication system and the ground segment. In the framework of a project called 'On-Orbit Servicing End-to-End Simulation', the final approach to and capture of a tumbling client satellite is simulated. The necessary components are developed and the entire chain will be tested and verified. This involves both on-board and on-ground systems. Concerning the space segment, this involves rendezvous sensors (CCD camera, PMD camera and LiDAR), the on-board guidance, navigation and control software, a robotic arm for grasping the client and a stereo camera for visual servoing mounted on the robotic arm. A software satellite simulator is employed which emulates the physical environment of the two spacecraft. Apart of the dynamical simulator, the satellite simulator contains also the entire on-board data handling system. Two robotic test facilities, the European Proximity Operations Simulator (EPOS 2.0) at DLR-German Space Operations Center and the OOS Simulator (OOS-Sim) at DLR-Robotics and Mechatronics Center are used. The hardware components are mounted on the robots of the hardware-in-the-loop test facilities. The robots move according to the resulting relative position and orientation of the two satellites computed by the numerical satellite simulator. The first part, the controlled approach to the final hold point will be performed using the EPOS facility. Then a switch to the OOS-Sim facility will be done, followed by a capture of the target. In the project, the ground infrastructure is established as for a real servicing mission including three consoles: a standard satellite bus console, a rendezvous console and a robotic console. Both standard telemetry like numerical housekeeping data and non-standard science telemetry such as telepresence status, camera images, etc. can be visualized and monitored at the special rendezvous and robotic consoles. Further, standard telecommands like high-level commands and science telecommands like telepresence commands can be generated at the consoles. In a control room, the consoles are prepared, and all necessary operational applications and interfaces are developed. During the simulation of the telerobotic operation, it is important to provide realistic communication environment with different parameters like they occur in the real-world. This includes values of delay and jitter, loss or corruption of data at different times during the mission. Since the telerobotic mission is also a real-time scenario, the entire communication channel has to be set up as close to the real scenario as possible. This paper describes the entire concept of the end-to-end rendezvous and berthing simulation, provides details on the implemented systems, and presents results of first integration tests.