'Johannes Kepler' space freighter launch delayed

By Jonathan Amos
Science correspondent, BBC News

Image caption,
The 200th Ariane on the launch pad

A technical problem prevented Europe's unmanned space freighter from launching to the space station on Tuesday.

The Johannes Kepler robotic truck was due to lift off from French Guiana on an Ariane 5 rocket.

But with barely four minutes left on the countdown clock, the mission was called off by the rocket's operator.

Telemetry suggested the Ariane had a measurement fault in its fuelling system. A Wednesday launch has now been set for 1850 local time (2150 GMT).

At more than 20 tonnes, the European Space Agency (Esa) truck is set to become the heaviest payload an Ariane rocket has ever lifted into the sky.

The robotic ship will be delivering food, air, fuel, experiments and other equipment to the International Space Station (ISS).

Another key task for the freighter in the coming months will be to push the orbiting platform to a higher altitude.

The ISS has a tendency to lose height over time as it brushes through the residual atmosphere still present 350km above the Earth.

Johannes Kepler will dock with the rear of the platform and use its propulsive might to boost the station's orbit.

One consequence of Tuesday's postponement at the Kourou spaceport is that Nasa's shuttle Discovery will also now be delayed in its mission to the ISS.

The freighter and the shuttle use the same data relay satellites in flight, and mission managers will not permit the two ships to be en route to the station at the same time.

With Discovery due to launch only a day after Kepler docks at the ISS, any hold up in the freighter's schedule immediately impacts the shuttle's timeline, too.

A Wednesday launch for Kepler would have it docking with the ISS on 24 February, with a Discovery launch from the Kennedy Space Center in Florida then taking place on 25 February.

The Ariane missions that launch telecommunications satellites enjoy an extended "window" in which to get the rocket off the ground, meaning the vehicle can be held for a few minutes if a technical issue arises that can be solved easily. But because the freighter must chase down the over-flying space station, its launch opportunity is necessarily instantaneous. If it does not launch in the moment, its ability to catch the platform in orbit is lost for that day.

Media caption,
An artist's impression of ATV2 Johannes Kepler flying over France

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