10th May 2012 Envisat satellite operations end.

Just weeks after celebrating its tenth year in orbit, communication with the Envisat satellite was suddenly lost on 8 April. Following rigorous attempts to re-establish contact and the investigation of failure scenarios, the end of the mission is being declared.

A team of engineers has spent the last month attempting to regain control of Envisat, investigating possible reasons for the problem. Despite continuous commands sent from a widespread network of ground stations, there has been no reaction yet from the satellite. As there were no signs of degradation before the loss of contact, the team has been collecting other information to help understand the satellite’s condition. These include images from ground radar and the French Pleiades satellite. With this information, the team has gradually elaborated possible failure scenarios.

One is the loss of the power regulator, blocking telemetry and telecommands. Another scenario is a short circuit, triggering a ‘safe mode’ – a special mode ensuring Envisat’s survival. A second anomaly may have occurred during the transition to safe mode, leaving the satellite in an intermediate and unknown condition.

Although chances of recovering Envisat are extremely low, the investigation team will continue attempts to re-establish contact while considering failure scenarios for the next two months. The outstanding performance of Envisat over the last decade led many to believe that it would be active for years to come, at least until the launch of the follow-on Sentinel missions.

However, Envisat had already operated for double its planned lifetime, making it well overdue for retirement. Envisat delivered over a thousand terabytes of data. An estimated 2500 scientific publications so far have been based on this information.

Now with the end of Envisat's mission, the launch of the upcoming GMES Sentinel satellites has become even more urgent to ensure the continuity of data to users, improve the management of the environment, understand and mitigate the effects of climate change and ensure civil security.

See also Press Release on the ESA Portal at http://www.esa.int/esaCP/SEM1SXSWT1H_index_0.html

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