"I'm not aware that we have a security issue," he said. "It's really just a big thing falling on the ground that we want to make sure we're prepared for."
The satellite includes some small engines that contain a toxic chemical called hydrazine - which is rocket fuel. But Renuart said they are not large booster engines with substantial amounts of fuel.
Video images of the satellite captured by John Locker, a British amateur satellite watcher, show it to be about 13 feet to 16.5 feet across. He believes it weighs a maximum of 10,000 pounds. Locker calculated its size with data on its altitude and location provided by other amateur satellite watchers, using the International Space Station as a yardstick.
Satellite watchers - a worldwide network of hobbyists who track satellites for fun - have been plotting the satellite's degradation for a year. They estimate it is now at an altitude of about 173 miles, and Locker believes it is dropping about 1,640 feet a day.
Where it lands will be difficult to predict until the satellite falls to about 59 miles above the 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. From that point on, he said, it will take about 30 minutes to fall.
In the past 50 years of monitoring space, 17,000 manmade objects have re-entered the Earth's atmosphere.
