Didn't we just do this? A two-ton German space telescope will crash back to earth today or tomorrow, but scientists can't determine where it will land. The satellite, launched in 1990, will likely break up into 30 or so pieces as it goes through the atmosphere. The largest single piece, the telescope's mirror, is heat resistant and weighs about 1.7 tons. It comes just weeks after Nasa's six-ton UARS satellite crashed back to Earth, landing in the Pacific Oceans. Nasa was unable to predict where UARS would land, but the odds of it hitting a populated area were infinitesimal.