PARIS — The European Space Agency’s (ESA) Envisat spacecraft remains stable in orbit after unexpectedly ceasing communication with ground stations April 8, according to optical, radar and laser observations of the spacecraft.

With a recovery effort under way, ESA and its international partners are attempting to determine whether the Earth-observation satellite has entered “safe mode” — an indication that it could be revived. But efforts to reestablish contact with Envisat have so far been unsuccessful.

The French space agency CNES turned its new high-resolution Pleiades satellite on Envisat April 15 and has been snapping images of the disabled spacecraft, which passed at a distance of roughly 100 km (62 mi.). Flight specialists and engineers are now using the images from the EADS Astrium-built spacecraft to determine the orientation of Envisat’s power-providing solar panel.

“If the panel is in a suitable position for sufficient exposure to the Sun, enough power is being generated to put Envisat into safe mode, and could allow for re-establishing communications with Earth,” ESA said in an April 20 news release. 

The Fraunhofer Institute for High-Frequency Physics and Radar Techniques in Wachtberg, Germany, is also providing images to help determine Envisat’s orientation. Images from the TIRA ground-based tracking and imaging radar show the satellite’s body, solar panel and radar antenna.

The U.S. Joint Space Operations Center at Vandenberg AFB, Calif., along with multiple laser-ranging ground stations, is providing data on Envisat’s orbit.

The 8,000-kg (17,600-lb.) satellite lofted to low Earth orbit in 2002 is the largest civil satellite ever launched. In March, Envisat marked its 10th year in operation, more than double its five-year design life.

The potential loss of Envisat services has disrupted the flow of critical climate and other environmental-monitoring data to the global Earth-observation community.

ESA officials say the interruption underscores the urgent need to fund Europe’s Global Monitoring for Environment and Security program, a flagship Earth-observation mission that could be delayed if the European Commission excludes €5.8 billion ($7.6 billion) in operations costs within the framework of its next seven-year spending cycle, which begins in 2014.