Researchers Unable to Revive Europe's Envisat

Gone silent. Ground controllers haven't been able to contact Envisat since 8 April.

European Space Agency

Things are not looking good for Europe's flagship Earth observation satellite Envisat. Ground controllers lost contact with the craft on 8 April and so far have been unable to re-establish contact. Envisat, the largest ever civilian Earth observing satellite, carries a battery of sensors for scanning land, sea, and atmosphere, and has been the mainstay of European environmental researchers for the past 10 years.

Following the loss of contact, controllers have aimed a laser at retroreflectors on the craft and found that it is still in a stable orbit and not spinning; that rules out a collision. Images from a ground-based radar show that the craft's own radar antenna and solar array are both intact. On 15 April, the French Space Agency spun round its recently-launched Pleiades Earth observation satellite to point upward and snap an even more detailed picture of Envisat from just 100 kilometers away. This again showed no sign of damage and gave no clues to what is wrong.

The European Space Agency (ESA) had hoped that Envisat would last another couple of years until it launches its next-generation Sentinel satellites, starting next year. In the meantime, researchers must find other sources of data. ESA already has an agreement to get radar imaging data from Canada's Radarsat. Those using Envisat's radar altimeter also have alternatives. "We at least for the time being have [ESA's] CryoSat-2 to ensure continuity of polar altimetry," says climate physicist Seymour Laxon of University College London. But for those studying air quality and atmospheric science, "there is nothing to replace [Envisat's instruments]," says Robert Meisner of ESA's Earth observation program. The next generation of these instruments are due to fly on Sentinel 3, slated for launch in 2014.

"Envisat was a big success. We celebrated its tenth birthday just a few weeks ago. We're disappointed that it's just gone," says Meisner. Ground controllers are continuing to try different ways to re-establish contact and are not saying how long it will be before they give up. If the mission has to be abandoned, Meisner says the craft is in a stable orbit and is unlikely to re-enter the atmosphere for 100 years.