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Euro climate probe Envisat silenced, boffins baffled

ESA loses contact with ageing space workhorse

Engineers at the European Space Agency have lost contact with their environment-studying satellite Envisat, which stopped sending data five days ago.

Envisat, the largest Earth observation spacecraft ever built, has been beaming back information about our world's land, atmosphere, oceans and ice caps for the last ten years. The satellite has been in orbit for twice as long as the agency expected, but boffins hoped to hang onto the craft until its successors, the Sentinels, blasted off into space.

Sentinel 1 is due to launch next year on its polar-orbiting, all-weather, 24-hour radar imaging mission, while Sentinel 2 will monitor the land and Sentinel 3 will examine sea-surface topography. Sentinel 5 is going to monitor the atmosphere and is scheduled to blast off in 2014, with Sentinel 4, another atmosphere-watching sat, going up in 2019.

"The interruption of the Envisat service shows that the launch of the GMES Sentinel satellites, which are planned to replace Envisat, becomes urgent," said Volker Liebig, ESA director of Earth Observation Programmes, in a canned statement.

The ESA first realised Envisat was in trouble on 8 April when the satellite didn't send any data as it passed over the Kiruna ground station in Sweden. Mission controllers immediately declared a spacecraft emergency and asked other ESA tracking stations to make contact with the probe.

In an effort reminiscent of attempts by Roscosmos last year to revive the doomed Russian spacecraft Phobos-Grunt, the ESA's recovery team has been trying to re-establish communications with their craft as it stays in a stable orbit around Earth. Boffins have yet to figure out what went wrong with Envisat.

Envisat was the ESA's follow-up to ERS and was launched in 2002. The satellite, which has cost the agency around €2.3bn (£1.9bn, $3bn) over its lifetime, was only expected to last five years. ®

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