Validating spacecraft docking to the International Space Station through distributed simulation over an ATM network

Stuttgart, 02 November 98 The French experts from Aérospatiale are co-operating with the Deutsches Zentrum für Luft- und Raumfahrt (DLR) and the Rechenzentrum Universität Stuttgart (RUS) in an Esprit funded project for space systems' validation. This kind of task has to be performed through shared and complex simulation between geographically dispersed aerospace centre facilities. The use of Asynchronous Transfer Mode (ATM) technology, which is available via the current European networking infrastructure, has allowed the project partners to successfully demonstrate the potential of distributed simulation with hardware in the loop for a specific validation mission, consisting in the docking of the Automated Transfer Vehicle (ATV) spacecraft with the International Space Station (ISS). This new approach holds in store a faster and cost-saving integration of space systems thanks to a more efficient use of functional simulation facilities.

The building and launching of space systems involves expensive and delicate business. The aerospace industry simply cannot afford to learn from first flight failures in a trial and error process. It is therefore of vital importance to seriously test the new spacecrafts on beforehand in a severe validation procedure to check out the accurate integration of each single component and to evaluate the entire system against all of the operational requirements, in order to face any imaginable situation out there in space. The prime contractors and vessel manufacturers perform this challenging job in Functional Simulation Facilities (FSF). These types of infrastructure host costly platforms with all the necessary electrical and hydraulic equipment, wired links and accompanying software.

The partners within the ATV-DSD (Automated Transfer Vehicle - Distributed Simulation Demonstration) project cherish the ambition to turn the platform systems into distributed interactive simulation facilities (DISF) by exploiting existing High Performance Computing and Networking (HPCN) technology, based on recent ATM developments. High speed networks are able to provide efficient and high quality delivery of large volume data which will facilitate co-operation between the various FSF sites and avoid duplication of costs. The ATV spacecraft mission rehearsal, for instance, requires more than 100 Mecu for each facility in France and Germany. The validation process will take at least 2 years, without considering the future astronauts and ground controllers training.

The ATV spacecraft has been planned by the European Space Agency (ESA) as a servicing and logistics vehicle with a modular architecture for supply of the International Space Station (ISS) at regular intervals. In 2002, ATV will be launched by Ariane5 for the very first time in a docking mission with the future ISS. Every 17 months, a new flight will be programmed until 2013. ATV will be used to refuel and reboost the ISS, by increasing the station's orbit altitude with the vehicle's propulsion system. The spacecraft will also provide the ISS with life-supporting cargo, such as compressed air, water, and pressure payloads consisting of food and experiments, as well as free the station from waste in turn. ATV measures 8 metres in length and has a diameter of 4.57 metres.

The French manufacturer Aérospatiale is the prime contractor for the system engineering, flight software, integration and testing of ATV. Logically, this aerospace specialist equally is responsible for the management of the ATV-DSD project. Together with the German partners DLR and RUS, the ATV docking procedure will be validated through the remote usage of three geographically distributed FSF sites at Les Mureaux in France, and both at Oberpfaffenhofen (DLR) and the University of Stuttgart in Germany. After launch, the following scenario will be developed: the ATV separates from the launcher and attains a circular orbit. After 46 hours of phasing, the rendez-vous with the ISS will be prepared. Docking will take place on the side of the Russian service module. After a period of six months, the ATV will separate from the ISS and disintegrate if it reaches again the Earth's atmosphere.

The operators of the FSF site in Les Mureaux will organize the actual simulation of the docking procedure by running the optical rendez-vous sensor (RVS) in real time with the other sub-components within the space system. The dynamic behaviour and the relative position of the ATV in the process of separating from the ISS is simulated at the European Proximity Operations Simulator (EPOS) FSF site in Oberpfaffenhofen. The powerful ATM based networking infrastructure will allow access to on-demand resources which can be applied with sufficient bandwidth capacity to simultaneously execute the complex simulations with minimum transmission delays. In this way, the work for the ATV-DSD project constitutes an excellent preparation for the EDISON initiative, which will further explore the potential of DISF or Distributed Interactive Simulation Facilities under the wings of the Esprit programme. For more details, please consult the ATV-DSD home page.

Leslie Versweyveld