A dead US spy satellite in a deteriorating orbit is expected to hit the Earth during the first week of March, officials said.
Where the satellite will hit is not known. Officials familiar with the situation say about half of the 2,270 kilograms spacecraft is expected to survive its blazing descent through the atmosphere and will scatter debris, some potentially hazardous, over several hundred miles. The officials spoke on condition of anonymity because of the sensitivity of the matter.
The satellite is outfitted with thrusters, small engines used to position it in space, that contain the toxic rocket fuel hydrazine. Hydrazine can cause harm to anyone who comes into contact.
The satellite, known by its military designation US193, was launched in December 2006. It lost power and its central computer failed almost immediately afterward, leaving it uncontrollable. It carried a complex and secret imaging sensor.
US officials do not want the equipment to be recovered by people who should not have control of it.
Where it lands will be difficult to predict until the satellite descends to about 59 miles above Earth and enters the atmosphere. It will then begin to burn up, with flares visible from the ground, said Ted Molczan, a Canadian satellite tracker.