World's biggest Earth-observing satellite remains 'dead in space' - and other spacecraft are enlisted in last-ditch attempt to revive 8-tonne orbiter



Satellite has failed to enter 'safe mode' to preserve power

Unless it moves its solar panels, it could fail permanently

Radar images from Earth appear to show satellite is undamaged

High-resolution Pleiades satellite to inspect 'dead' craft on Sunday

Radio silence since it failed to make contact on Tuesday

Teams of engineers attempting to re-establish contact

Mystery has deepened around the eight-tonne Earth-observing Envisat satellite after the satellite fell silent - and has failed to enter the 'safe mode' expected of ailing space vehicles.

In 'safe mode', it would use its power to angle its solar panels towards the sun. Without it, it could fail permanently.



Scientists and engineers are scrambling to pinpoint the problems afflicting the satellite - radar images from Earth appear to show that it's intact.

If no other solution is found, a high-resolution imaging satellite, Pleiades, will scan the craft on Sunday.



'After 10 years of service, Envisat has stopped sending data to Earth. ESA's mission control is working to re-establish contact with the satellite,' says the European Space Agency

'We continue to try to re-establish contact with the satellite, and to collect more information on the satellite's status by ground radar images, from optical images, from telescopes, but also from other spacecraft,' said Professor Volker Liebig of ESA.

The satellite failed to radio to its controllers on April 8 - and a team of engineers, scientists and mission operators are now attempting to restore contact with the satellite.

"On Sunday, will try to program the satellite Pleiades to see if they can image Envisat, to give us more detailed knowledge on whether there is damage on the outside,' he said.



'After 10 years of service, Envisat has stopped sending data to Earth. ESA's mission control is working to re-establish contact with the satellite,' says the European Space Agency.



'The first sign that there was a problem came on 08 April when contact with the satellite was unexpectedly lost, preventing the reception of any data as it passed over the Kiruna ground station in Sweden.'



The eight-tonne Envisat had a planned lifetime of five years, but has doubled that - and the European Space Agency has celebrated the anniversary with a gallery of the unforgettable imagery captured by Envisat's eight sensors.



More than 2,000 scientific publications have been based on Envisat data.



Envisat's data has been used in 4,000 science projects in 70 countries, including landmark research into climate change.



Its study of ocean currents was used last year to simulate dispersal of nuclear pollution from the Fukushima accident, and it gained real-time images of the BP oil spill in the Gulf of Mexico in 2010.





Clouds south of the Canary Islands: A unique cloud formation was captured by Envisat in this false-colour image

With ten sophisticated optical and radar sensors, the satellite continuously observes and monitors Earth’s land, atmosphere, oceans and ice caps.



In 2010, the satellite’s orbit was changed to allow Envisat to continue operating for at least another three years - so its sudden silence is a worry for its ground team.

Its replacement -– the Sentinels – will become fully operational in 2013.

Envisat’s largest instrument is the Advanced Synthetic Aperture Radar, which can be used day or night because it sees through clouds and darkness.



This is particularly useful over polar regions, which are prone to long periods of bad weather and extended darkness.



Other instruments include the Radar Altimeter, which measures surface topography to an accuracy of a few centimetres, revealing the changes in sea-surface height over time.

A phytoplankton bloom in the South Atlantic Ocean east of the Falkland Islands

The Galapagos Islands, captured in a radar view that highlights minute changes in sea surface level











