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News  Successful tests of ATV rendezvous replicate the 2007 Jules Verne mission
A milestone in the development of the Automated Transfer Vehicle (ATV) was passed earlier this summer at Europe’s largest ship hull test facility, west of Paris. It involved tests conducted on the critical final phase of the automated rendezvous and docking system of ATV by using state-of-the-art sensors and flight control software. "For the first time, to replicate the Jules Verne ATV rendezvous, ATV flight sensors were used successfully in life-size rendezvous conditions, feeding measurements into the flight control computer. At the same time, a simulator calculates the dynamic motion corresponding to how the vehicle behaves in space. A third system replicates physically this computation into a relative motion between the sensors, carried by an industrial robot, and their targets carried by a mobile platform. The integration of all these systems into a closed-loop test, as we call it, worked exceptionally well from start of the rendezvous – at some 250 metres – all the way to docking," said ESA ATV engineer Stein Strandmoe, who supervised this series of rendezvous test campaigns.
To realistically check the flight hardware videometer capabilities – in acquisition and targeting – the tests are conducted in a research facility of the French defence agency 'Délégation Générale pour l'Armement' (DGA), located in Normandy.
Inside a 600-metre long building, a 120-tonne mobile platform controlled with millimetre precision, enables the continuous tri-dimensional approach between the two space vehicles, from a range of several hundred metres to within docking contact conditions. On the platform, a set of passive rendezvous targets (retroreflectors), identical to the ones installed on ISS, face the sensors mounted on an articulated industrial robotic arm. This platform replicates the closing motion between ATV and ISS, and the robot replicates the relative rotation and lateral motion between the two vehicles. The relative motion achieved is identical to the one expected during next year's rendezvous between Jules Verne and ISS.
“When the ATV is targeting and getting closer to the ISS, the Station has its own oscillations due to the firing of ISS attitude control jets. So the ATV must adjust constantly like two dancing partners who remain constantly in phase in their movements”, said ESA astronaut Jean-François Clervoy, senior advisor to the ATV programme.
To make this rendezvous testing as realistic as possible, a 4.15 metre diameter mock-up of the aft end of the ISS Service Module is placed on the facility's moving platform. It includes the docking port, the Russian-made thermal blankets and the retro-reflective targets. The facility also can simulate the Sun using a 24kW electrical spot-light during the simulations.
“These tests are very important because it is the first time ever that we can really test the whole system for the rendezvous and docking. This is the only facility in the world which allows us to simulate the whole rendezvous, from the time Jules Verne starts coming in – using the optical sensors – right through to docking. And this system works in complete closed-loop conditions where all aspects of the spacecraft are either represented for real – software, sensors, trajectories – or simulated such as Jules Verne inertia, thrusters firing etc...", said John Ellwood, ESA’s ATV Project Manager.
Jules Verne, the first flight model of a series of ATVs foreseen to service the International Space Station (ISS), is currently at the ESA facility in the Netherlands is undergoing final integration.
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