A month after losing communications with the satellite Envisat, ESA has decided to declare its mission closed.

The Envisat (Environmental Satellite) was launched on March 1, 2002 using an Ariane 5 rocket and entered into a polar orbit at an altitude of about 790 km (about 470 miles). In the ’90s, the ERS (European Remote-Sensing) satellites were launched to observe the Earth, Envisat was equipped with more advanced versions of the instruments used by the ERS satellites and by others. Ten instruments in total were intended to gather information about land, water, ice and atmosphere of the planet.

Envisat was the most advanced satellite for environmental observations and the largest satellite for civilian use – it has the size of a bus – ever launched. Its development, launch and the first 5 years of operations cost about 2.3 billion Euros but that was money well spent because Envisat gathered important data on the melting of Arctic ice, on the level and temperature of the seas, on ocean currents, on air pollution levels, on the geologic consequences of earthquakes and volcanic eruptions and even on deforestation.

The Envisat satellite was designed primarily for scientific research but the data collected have been important over time even in case of floods and accidents involving oil spills. It’s been among the sources of information used to help authorities in the interventions in the event of natural disasters but also in the ones caused by humans.

The Envisat satellite mission was supposed to last 5 years but it was renewed because its instruments kept on working normally. At the completion of its tenth year, Envisat seemed to be able to keep on providing valuable information on the environment but on April 8, 2012 it suddenly stopped communicating.

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For a month, a group of engineers tried to resume communications with the Envisat satellite by sending a series of commands from different ground stations. Unfortunately no attempt has been successful.

The ESA engineers have also used images of Envisat obtained using other satellites to try to figure out if there was any visbile damage but the cause of the problem remains obscure.

It’s possible that there has been a failure of the power regulator that blocked telemetry and telecommands. Another possibility is that a short circuit made Envisat enter “safe mode”, a state that’s supposed to ensure the satellite’s survival but another anomaly may have stopped the transition leaving it in an intermediate state.

Although the ESA has declared the end of the Envisat mission, other attempts will still be made to re-establish contact with the satellite while the possibilities of failure will be examined.

The Envisat satellite has provided a wealth of information within the European Global Monitoring for Environment and Security (GMES) program. This program has the launch of the first satellites in the Sentinel series scheduled for the next year. At this point that becomes even more important to keep on monitoring the Earth’s environment.