An alternative concept of docking for the ConeXpress satellite

ConeXpress is an affordable multi-mission platform that will be launched as auxiliary payload on the Ariane 5 launcher and as such it exploits the excess launch capacity of Ariane 5 for easy access to space. The satellite can be used for different missions depending on the payload placed in it. The primary objective of ConeXpress is to perform in-orbit servicing. Two years ago the company Orbital Recovery Ltd started to pursue the market of in-orbit servicing and has now teamed with Dutch Space to develop ConeXpress as an Orbital Recovery System. ConeXpress Orbital Recovery System will prolong the operational life of telecommunication satellites by supplying guidance, navigation and propulsion for station keeping and attitude control for an additional 8-10 years. This Master’s Thesis is concerned with the docking phase of the ConeXpress project. The model for the baseline docking phase is currently being developed at Dutch Space and the main mechanical element of the docking system is the Capture Tool, constructed by DLR in Germany. The Capture Tool is inserted into the apogee kick engine nozzle of a client satellite where it expands and locks in the throat of the engine nozzle. This Master’s Thesis will deal with a possible alternative concept to the docking phase. This approach will reduce the mass of the satellite by using only sensors and control and not any mechanical structures that would complicate the docking. Using the alternative concept for docking the Capture Tool could be abandoned and also the high position and orientation control requirements associated with it. The work started with an investigation of possible alternative docking concepts and after a trade-off the most suitable concept, a 3D Laser Camera System from the Canadian company Neptec, was chosen for further investigation. In order to test the performance a model of the camera system needed to be implemented in the DSF, the Design Simulation Facility (based on MATLAB/Simulink): the simulation environment used in the ConeXpress project. To get acquainted with the program, simulations were first made on the original docking concept and also on the rendezvous phase. After this, simulations for the docking phase using the Neptec 3D Laser Camera System were started. A simplified version of the System, based on the docking camera with range, field of view and resolution adapted for the Neptec system was implemented in the simulator. The results from this simple model clearly showed first of all that the control system of the satellite in the simulator needed to be improved to be able to handle the higher speeds and longer range during the docking phase, but also that the Neptec 3D Laser Camera System handles the procedure well. It is therefore an interesting alternative to the Capture Tool docking approach and should be investigated further.Validerat; 20101217 (root