The $2.9 billion Envisat is the world’s largest civilian Earth-observing satellite, originally designed for a five year mission spent taking high-res images of Earth from above. Envisat outlasted its expiration date by a further five years, turning in a solid decade of service.

 

But on April 8, its run of good luck came to an end when ESA officials say it stopped communicating with ground stations. For the past month agency engineers have been trying to restore contact to no avail. The satellite may have experienced a short circuit that kicked it over into a safe mode from which it cannot escape for whatever reason. Or a power regulator may have failed, or any number of other things may have happened.

The bottom line: at 16 feet wide and 46 feet long, Envisat--once the ESA’s scientific workhorse--is now a 17,600 pound orbiting space junk risk, and will remain one for the next 150 years or so, experts say.