Page last updated at 17:00 GMT, Monday, 16 March 2009

Gravity satellite launch delayed

By Jonathan Amos
Science reporter, BBC News, Frascati

Goce (Esa)
Goce has had to overcome many technical hurdles to get to the launch pad

The launch of a European Space Agency (Esa) gravity mapping satellite, called Goce, has been delayed.

Controllers suspended the countdown when the service tower protecting its rocket failed to move clear of the pad and allow a lift-off.

Engineers hope to fix the problem, which should allow another launch attempt to be made on Tuesday.

Goce will give scientists new insights into how the interior of the planet is structured and how the oceans move.

Service tower (Esa)
The tower is supposed to pull back from the rocket to allow it to launch
Researchers will also use the satellite's data to frame a universal system to measure height anywhere on Earth.

The super-sleek spacecraft was due to go into orbit at 1421 GMT on a modified intercontinental ballistic missile, known as a Rockot, from the Plesetsk Cosmodrome in north-west Russia.

Matthias Oehm from Eurockot, the company which markets the vehicle, said giant doors on the service tower should have opened before the whole structure moved back. They did not. "The exact reason, whether this is a mechanical problem or an electric problem, is being looked at by the space forces at Plesetsk," he explained.

Volker Liebig, the director of Esa's Earth Observation Programmes, said Goce and its launch vehicle were safe, and were ready to proceed with another attempt when a new opportunity arose.

Plesetsk Cosmodrome (BBC)

"All is on green," he added. "You have to understand that we have a launch window that is practically [instantaneous], and then we have to wait 24 hours because we have to inject the spacecraft into exactly the right orbit."

The delay will frustrate scientists waiting for Goce's data, but they have become accustomed to slippage on this particular mission.

The Gravity Field and Steady-State Ocean Circulation Explorer (Goce) initially fell two years behind schedule because engineers had to work through immense technical difficulties in building its sensitive instrumentation.

The satellite was then due to go into orbit a year ago, before a succession of technical issues were raised about the performance of the Rockot vehicle. Each one had to be resolved before Monday's launch date was approved.

The launch of Goce is delayed just before lift-off

"For 10 years we have been preparing for this mission, and for five years we've had dry runs; and now it's really time that this baby got into orbit," commented Reiner Rummel from the Technical University of Munich, Germany, and one of the researchers who conceived the mission.

Esa is particularly anxious about this launch because of what happened to its Cryosat spacecraft in 2005.

The ice mapping spacecraft, which is also part of the agency's new Earth Explorer programme, was destroyed when its Rockot failed just a few minutes into its flight, dumping the wreckage into the Arctic Ocean.

Although Goce is being lofted from Plesetsk, officials from Esa are following the launch campaign at the agency's Earth observation HQ here in Frascati, Italy.

GRAVITY FIELD AND STEADY-STATE OCEAN CIRCULATION EXPLORER
GOCE (Esa)
1. The 1,100kg Goce is built from rigid materials and carries fixed solar wings. The gravity data must be clear of spacecraft 'noise'
2. Solar cells produce 1,300W and cover the Sun-facing side of Goce; the near side (as shown) radiates heat to keep it cool
3. The 5m-by-1m frame incorporates fins to stabilise the spacecraft as it flies through the residual air in the thermosphere
4. Goce's accelerometers measure accelerations that are as small as 1 part in 10,000,000,000,000 of the gravity experienced on Earth
5. The UK-built engine ejects xenon ions at velocities exceeding 40,000m/s; Goce's mission will end when the 40kg fuel tank empties
6. S Band antenna: Data downloads to the Kiruna (Sweden) ground station. Processing, archiving is done at Esa's centre in Frascati, Italy
7. GPS antennas: Precise positioning of Goce is required, but GPS data in itself can also provide some gravity field information

Jonathan.Amos-INTERNET@bbc.co.uk

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