A disabled U.S. spy satellite is likely to break into small pieces when it falls to Earth within weeks, posing little danger to humans, U.S. government officials said Monday.
Most, if any, debris that survives the intense heat of re-entry would likely fall into the oceans, which cover more than 70 percent of the planet, White House National Security Council spokesman Gordon Johndroe said. But he said the U.S. government was monitoring the satellite’s descent from orbit and examining different options to “mitigate any damage.”
The U.S. military could potentially use a missile to destroy the minivan-sized satellite in space, but one senior U.S. defense official told Reuters that was unlikely for several reasons, including concern about creating space debris, as China did when it shot down one of its satellites last year.
“Given that 75 percent of the Earth is covered in water and much of the land is uninhabited, the likely percentage of this satellite or any debris falling into a populated area is very small,” Johndroe said.
Pentagon spokesman Bryan Whitman said more than 17,000 human-made objects have re-entered Earth’s atmosphere over the past 50 years without major incident.
“We are monitoring it ... we take our obligations seriously with respect to the use of space,” Whitman said, noting the satellite was expected to return to Earth “over the next several weeks ... late February, early March.”
Never became operational
The satellite is a classified National Reconnaissance Office spacecraft launched from Vandenberg Air Force Base in California in 2006, four senior U.S. officials who asked not to be named told Reuters.
The satellite, known as L-21, has been out of touch since shortly after reaching its low-Earth orbit. Built by Lockheed Martin at a cost of hundreds of millions of dollars, the satellite has fallen more than 43 miles (70 kilometers) to an orbit at around 174 miles (280 kilometers) above Earth. U.S. and European astronomers estimate it is dropping at an accelerating rate of 5 miles (8 kilometers) a day.
Because the satellite never became operational, it has toxic rocket fuel on board that would have been used to maneuver the satellite in space. It could pose a danger if the fuel tank does not explode upon re-entry.
Thousands of space objects fall to Earth each year, but they generally scatter over a huge area and there have never been any reported injuries, two U.S. officials said.
Occasionally, bigger objects survive, including a 563-pound (255-kilogram) stainless-steel fuel tank from a Delta 2 rocket that landed 50 yards (meters) from a farmer’s home in Texas in 1997.
This L-21 satellite is much smaller, and more likely to burn up as it enters the atmosphere, scientists said.
The U.S. military has no weapon designed to shoot down a satellite, but it demonstrated the ability to do that in the mid-1980s, and could cobble together a plan to do so again fairly quickly, said the senior defense official.
Such a move appears unlikely, given global dismay about China’s use of a missile to destroy a much bigger satellite at a higher orbit, which scattered nearly 1,000 pieces of debris throughout space, the official said.
Not the first time
The largest uncontrolled re-entry by a NASA spacecraft was Skylab, the 78-ton abandoned space station that fell from orbit in 1979. Its debris dropped harmlessly into the Indian Ocean and across a remote section of western Australia.
In 2000, NASA engineers successfully directed a safe de-orbit of the 17-ton Compton Gamma Ray Observatory, using rockets aboard the satellite to bring it down in a remote part of the Pacific Ocean.
In 2002, officials believe debris from a 3.5-ton science satellite smacked into Earth's atmosphere and rained down over the Persian Gulf, a few thousand miles from where they first predicted it would plummet.
This report includes information from Reuters and The Associated Press.