ATV Jules Verne, the European Space Agency’s first resupply and reboost vehicle, has successfully performed a fully automated docking with the International Space Station (ISS). This docking marks the beginning of Jules Verne’s main servicing mission to deliver cargo, propellant, water, oxygen and propulsion capacity to the Station, as well as ESA’s entry into the restricted club of the partners able to access the orbital facility by their own means.The 19-ton unmanned spaceship manoeuvred from a holding position 39 km behind the 275-ton space outpost and conducted a 4-hour staged approach with several stops at reference points for checks. It autonomously computed its own position through relative GPS (comparison between data collected by GPS receivers both on the ATV and the ISS) and in close range it used videometers pointed at laser retroreflectors on the ISS to determine its distance and orientation relative to its target. Final approach was at a relative velocity of 7 cm/s and with an accuracy of less than 10 cm, while both the ATV and the ISS were orbiting at about 28000 km/h, some 340 km above the Eastern Mediterranean. ATV Jules Verne’s docking probe was captured by the docking cone at the aft end of Russia’s Zvezda module at 16:45 CEST (14:45 GMT). Docking was completed with hooks closing at 16:52 CEST (14:52 GMT). GTD has played a crucial role in the ATV’s vehicle. Our company has been subcontracted by Astrium to realize the Rendez-Vous & Docking on board software. GTD has also participated in the assembly and tests of the whole system.A million lines of code of maximum safety Class A SoftwareThe ATV flight software matches the complexity of the vehicle and its mission. The complexity of this software is due to the quantity and intrinsic complexity of the algorithms required to ensure an autonomous rendezvous, as well as the volume of data processed, and the number of possible configurations. Ultimately, this software represents: lmost a million lines of Ada code and configuration data lines (more than five times the amount for the Ariane 5 flight programme): · To comply with the safety and availability constraints, the electrical and digital (avionics) architecture of the ATV is quadruplex (quadruple redundancy) and contains no less than 50 items of equipment, such as nominal and redundant sensors and actuators, which are controlled by a fault tolerant central computer. This computer is composed of three data processing units each running the FAS (Flight Application Software) in parallel. · From its separation from the Ariane 5 launcher until de-orbiting and re-entry, via the phases of rendezvous, docking/undocking and support to the ISS during the attached phase, the ATV mission consists of almost 100 different operating modes.
