TOWARDS SPACECRAFT DOCKING EMULATION USING HARDWARE-IN-THE-LOOP SIMULATION Eric Martin 1 , Kourosh Parsa 1 , S´ ebastien Laurier Chapleau 1 , and Luc Baron 2 1 Canadian Space Agency, 6767 route de l’A´ eroport, St-Hubert (QC), Canada, J3Y 8Y9 e-mail: eric.martin@space.gc.ca 2 ´ Ecole Polytechnique, C.P. 6079, Succ. CV, Montr´ eal (QC), Canada, H3C 3A4 ABSTRACT Many demonstration missions such as Orbital Ex- press, DART, XSS-11, TECSAS, and the possible robotic servicing/decomissioning of Hubble have re- cently been planned. A common, important element to many of these missions is the necessity of me- chanically interfacing the spacecrafts involved. The Canadian Space Agency targets the utilization of a hardware-in-the-loop simulation (HLS) to emulate the satellite-docking procedure. This paper describes the spacecraft models implemented in the simulator, the orbital mechanics module, as well as the attitude and orbit control systems. The simulator can be used in one of the pure simulation or the HLS modes. In the former, a contact-dynamics model computes the forces and moments involved in the docking, whereas the actual docking hardware is used in the latter to obtain the contact forces and moments. 1. INTRODUCTION On-orbit servicing has recently received renewed at- tention with planned demonstration missions such as Orbital Express ∗ , DART † , XSS-11 ‡ , TECSAS [1] and the possible robotic servicing/decomissioning of Hubble [2]. These missions are respectively funded by the Defense Advanced Research Projects Agency (DARPA), the National Aeronautics and Space Ad- ministration (NASA), the United State Air Force (USAF), the German Space Center (DLR), and NASA. In addition, there are a few studies and de- velopment work on servicing commercial satellites. A common, important element to most of these mis- sions is the necessity of docking the spacecrafts in- volved. As for all other space applications, all tasks ∗ www.darpa.mil/tto/programs/oe.html † www.nasa.gov/mission pages/dart/main ‡ www.vs.afrl.af.mil/FactSheets/XSS11-MicroSatellite.pdf and procedures related to satellite docking have to be verified on earth prior to their execution in space. Therefore, reliable test facilities are needed. An alternative is faithful modelling of the dynam- ics of contact during docking. However, this op- tion seems elusive because the accuracy of the re- sults of any such contact-dynamics model is strongly dependent on the accuracy of the contact parame- ters identified. Hence, most organizations use exper- imental test facilities to test their hardware. As an example, the state-of-the-art end-effector developed by MDA Space Missions is shown in Figure 1 along with the testbed used to test this end-effector. In this setup, the end-effector is mounted on a driven carriage. This carriage can be moved at various ap- proach speeds in order to emulate the motion of the arm as the chasing spacecraft approaches the target spacecraft. On the other hand, the target spacecraft is floating on air-bearing pads, allowing for axial and lateral translation, and yaw rotation. Figure 1. End-effector and test-bed developed by MDA Space Missions for the Canadian Space Agency Proc. of 'The 8th International Symposium on Artifical Intelligence, Robotics and Automation in Space - iSAIRAS’, Munich, Germany. 5-8 September 2005, (ESA SP-603, August 2005)