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Last Updated: Monday, 10 March 2008, 11:39 GMT
Space truck orbits despite fault
By Jonathan Amos
Science reporter, BBC News

ATV artist's impression (Astrium)
Engineers are looking to recover the propulsion chain
Europe's new ATV space truck is up and running following Sunday's launch, although one propulsion glitch means a back-up system is currently being used.

The freighter is sitting in a 260km high orbit and is due to deliver just under five tonnes of supplies to the space station on 3 April.

The anomaly has shut down seven of the 28 attitude control jets and one of the space truck's four main engines.

Engineers are now investigating with a view to getting them all back online.

Even if they cannot, the vehicle is more than capable of completing its approach and docking to the space station, say European Space Agency (Esa) officials.

The ATV cannot approach the orbiting platform until after space shuttle Endeavour, due for launch on Tuesday, has completed its mission.

Ariane 5 climbs through the clouds (Esa)
It was a perfect launch for ATV's Ariane 5 rocket from Kourou

This gave engineers plenty of time to resolve the anomaly, explained Esa's ATV project manager John Ellwood.

"We're sitting and thinking about this; we're not in a rush to do manoeuvres," he told reporters in Kourou.

"We have the 10-day margin before we need to start going into [demonstration manoeuvre] days at the end of the month."

The problem came to light when a Propulsion Drive Electronics (PDE) control unit picked up a difference in pressures between the oxidiser and the fuel going through one of the ATV's four "propulsion chains". These are complex networks of pipes and valves leading from the fuel tanks to the thrusters.

The PDE immediately switched over to a back-up chain, and it also shut itself down just in case the anomaly was a problem in the electronics rather than in the physical system itself.

The issue is now being studied at the ATV control room in Toulouse, France, and at prime contractor EADS Astrium's Functional Simulation Facility at Les Mureaux north west of Paris. The latter has an engineering model of the ATV on which fixes can be tested before a patch is tried on the real spacecraft in orbit.

ATV at Kourou (Esa/Arianespace)
Total cargo: 4,860kg
1,340kg - 'dry' supplies
20kg - air (oxygen/nitrogen)
280kg - drinking water
860kg - propellant for ISS
2,360kg - re-boost propellant
The ship itself has 3,490kg of propellant for rendezvous, re-boost and de-orbit manoeuvres

It is possible something became dislodged or bent out of shape in the physical stress of Sunday's climb to orbit on the Ariane 5 rocket.

Engineers stressed, however, that the ATV was in good shape.

"The attitude control system works absolutely perfectly," said EADS Astrium's ATV project chief, Nicolas Chamussy. "Attitude control is stabilised. The system is qualified to work with three chains."

All other systems on the spacecraft are reported to be working normally. Its navigation systems quickly had the ATV pointing in the right direction. Antennas were deployed rapidly and the four solar arrays which power the spacecraft all unfolded properly.

The ATV must raise its orbit over the next few weeks. It will approach the station from behind.

The approach and docking will be entirely automated - there will be no manual assistance from the ground or from astronauts on the station.

A series of practice manoeuvres will be performed before the freighter is given final clearance to move in.

ATV at the ISS (Astrium)

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