ATV: An automatic success

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DATE:01/04/08
SOURCE:Flight International
ATV: An automatic success
By Rob Coppinger
As the European Space Agency's Automated Transfer Vehicle (ATV), named Jules Verne, embarks on the last few kilometres of its journey to dock at the International Space Station's Russian Zvezda module, a successful completion to the mission on 3 April will see ESA become the second agency to have a cargo-dedicated spaceship and the only space-faring organisation to have an entirely automatic resupply spacecraft.

The ATV journey began in 1995 when ESA member states agreed to join the ISS programme. Jules Verne, the first of a planned five of these expendable cargo spaceships, is scheduled to dock automatically on 3 April. The 10.3m (33.7ft) long, 4.5m diameter cylindrical spacecraft, with its 22.3m span X-shaped solar arrays, is designed to have a total mass of 20,500kg (45,100lb) and deliver 7,600kg of cargo. However on the first flight the vehicle's mass is 19,400kg, which includes just 6,400kg of cargo.

In comparison, NASA's Space Shuttle, which delivers 10,000kg of supplies using the Italian-built multi-purpose logistics modules, is manually piloted for its ISS docking. Russia's Progress cargo vehicle, which can deliver 2,500kg, is also under manual control during the final stages of its rendezvous.

Since its 9 March launch from Europe's French Guiana spaceport, using an EADS Astrium-built Ariane 5 Evolution Storable booster, the ATV has been undergoing a series of system tests. On 14 March it carried out its automated collision avoidance manoeuvre. This manoeuvre test was to show that the ATV could distance itself from the ISS if any problems arose during the final docking phase.

From a parking orbit 2,000km (1,240 miles) ahead of the ISS, on 27 March ATV was to move to a closer position to perform two days of rendezvous demonstrations, set for 29 and 31 March. While the ATV is automatic, these demonstrations involve ESA's ATV control centre (ATV-CC) in Toulouse, the Russian and US ISS partners and the ISS crew.

The ISS crew tasks include preparation of the Russian module for docking and issuing specific ATV commands. These are abort, hold, retreat or escape, when requested on 29 and 31 March and on docking day.

The two rendezvous demonstrations were to use waypoints near the ISS. On 29 March at 15:34 GMT the ATV's guidance and navigation system (GNC) was to be tested. Initiated from ATV-CC the vehicle was to move toward the ISS using relative GPS data to safely manoeuvre to waypoint S2, located 3.5km behind the ISS.

The results are assessed by the ESA Jules Verne ATV demonstration objectives report team and submitted to the ISS Mission Management Team. If the assessment led to a 30 March authorisation, the second demonstration would take place on 31 March at 13:40 to test the close-range sensors, the GNC and to practice the contingency procedures, commanded by ATV-CC and the ISS crew.

During this second test ATV was to be commanded to stop just over 10m from the Zvezda docking port, then go back to waypoint S4, which is 19m from the module, and finally to carry out an "escape manoeuvre" that will take Jules Verne away from and around the station.

If all goes to plan the docking is scheduled for 15:20 on 3 April. ESA's ATV-CC mission director, Alberto Novelli, said: "We are looking forward to an excellent first docking attempt on 3 April. It will be complex but after our successful launch and early orbit phase and the transfer to the parking orbit, the team...has gained a lot of confidence."

The docking procedure will begin at 12:44 with ATV starting from waypoint S3, 250m from the ISS. Its computers will carry out the automated final approach and docking. The vehicle will slow down to 70mm (3in)/s as it closes to within a few metres of the Russian module. ATV-CC mission controllers will direct the ATV in a step-by-step predefined approach, and will seek authorisation from the Russian mission control centre in Moscow before final contact is made.

Neither the USA nor Russia have this capability. Even NASA's Commercial Orbital Transportation Services programme, if successful in its goal of providing a resupply service by 2011, will not deliver a completely automatic docking system.