Paris, France: 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. 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 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.
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.
With ten sophisticated sensors, Envisat has observed and monitored Earth’s land, atmosphere, oceans and ice caps during its ten-year lifetime, delivering over a thousand terabytes of data.
An estimated 2500 scientific publications so far have been based on this information, furthering our knowledge of the planet.