The European Space Agency (ESA) says the mission has ended for Envisat, the largest Earth-monitoring satellite in history.

The satellite was launched in March 2002, but failed to call in as usual on April 8 of this year. Although only designed to function for five years, the eight-ton behemoth lasted twice as long, spending a decade measuring the land, oceans and ice of Earth.

While the ESA plans to launch more satellites for environmental monitoring, a controversy over their funding could mean delays. But scientists think such monitoring, especially for climate change, should remain a top priority.

A death in the family

After a month-long investigation and numerous attempts to re-establish contact with the satellite, the agency concluded that it had died due to a power failure.

Radar imaging showed the satellite was intact, but that it had not oriented its solar cells toward the sun, which would have allowed it to go into "safe mode" and provide an opportunity for continued contact.

Robert Meisner of the ESA says scientists think the satellite never even went into safe mode.

"We couldn't talk to it, so we couldn't do anything," Meisner told DW.

The ESA announcement read like a eulogy, paying tribute to the accomplishments of the defunct piece of technology.

"During those ten years, Envisat witnessed the gradual shrinking of Arctic sea ice and the regular opening of the polar shipping routes during summer months," the agency wrote.

"Together with other satellites, it monitored global sea-levels and regional variations, as well as global sea-surface temperatures," the statement continued.

Envisat also monitored the ozone layer and provided data on deforestation and pollution.

Although other satellites have assumed some of its duties, scientists think the demise of Envisat does not bode well for ongoing research.

'Huge gap'

John Burrows, an environmental physics professor at the University of Bremen, used the decade of data to map the hole in the ozone layer.

Burrows says that although about a third of atmospheric data-gathering is being conducted by other satellites, greenhouse gas and carbon dioxide measurements are currently not taking place.

And vertical profile data, used to determine emissions for ozone-depleting substances, has completely fallen off the map, says Burrows.

"There's a huge data gap at a critical point," Burrows told DW.

Funding issues cloud future

The ESA's Global Monitoring for Environment and Security program includes a set of satellites, named "Sentinels," which are hoped to fulfill many of Envisat's functions.

But funding issues within the European Union may put back the launch of the Sentinel satellites.

Under existing agreements, it was decided that the ESA would contribute 2.3 billion euros (3 billion dollars) to the development and construction of the Sentinel satellites.

The EU is expected to pick up the 5.8 billion euros (7.5 billion dollars) for their operation, services and later satellites.

Volker Liebig, director of earth observation programs for the ESA, said the expectation in ongoing negotiations was that the EU would include this funding in its general multi-year planning.

But the European Commission has now proposed that member countries pitch in on a sliding scale.

In an emailed statement, Carlo Corazza of the European Commission cited budgetary restrictions as the reason for not including the funding in the multi-annual financial framework.

Some suggest it is an attempt to use a popular program to get extra money.

In an interview with DW, Liebig said the demise of Envisat meant it was now time to "give up tactical games and join forces so we can launch a satellite as soon as possible."

Burrows also insisted that monitoring satellites were vital for governments and said that Envisat had provided strong data, particularly on climate change, which was used in the formulation of environmental policy.

"How can you develop policy without good evidence?" Burrows said. Earth-monitoring satellites "should be one of the first priorities to establish a sustainable future."

Sentinels on the way

Despite these concerns, the first Sentinel, Sentinel 1, is already partly assembled. And Sentinels 2 and 3 are being built in Friedrichshafen, Germany, Meisner said.

Provided operational funding is secured, Sentinel 2 could be launched in late 2012, and the next two could follow half a year later. The plan is for all the Sentinels to be in orbit by 2020.

The Sentinel satellites would "produce a lot more data, and provide much better coverage," according to Liebig.

And they would include mechanisms, allowing them to be de-orbited if necessary - unlike Envisat.

For now, though, and possibly for the next 100 years, Envisat will remain in space with all the other space trash circling our planet.

It's a sober ending for a hard-working satellite.

Author: Sonya Angelica Diehn
Editor: Zulfikar Abbany