The U.S. military plans to try to blast a malfunctioning satellite out of the sky by the end of the month to prevent the bus-size hunk of metal from leaking highly hazardous fuel into the atmosphere as it falls to Earth. The U.S. Department of Defense says the Navy will use surface-to-air missiles to knock it out sometime after February 20, when the space shuttle Atlantis is scheduled to return from its mission to the International Space Station.
The satellite, launched by the National Reconnaissance Office in December 2006 is not expected to hit a populated area, James Jeffery, deputy national security advisor, said yesterday during a press conference. But he added that President Bush decided to it should be destroyed to prevent leakage of highly toxic hydrazine fuel on its return. (For a transcript of the press conference, click here.)
In late January the U.S. government notified other nations that the satellite was unresponsive and would make an uncontrolled reentry later this month or in early March. Now the Navy is planning to intercept it prior to reentry at about 150 miles (240 kilometers) altitude, so that the unused hydrazine will be dispersed before it reaches the atmosphere. The weapon of choice: three modified Standard Missile (SM) 3 surface-to-air missiles launched from Aegis ships located somewhere in the North Pacific (the military would not be more specific). The window for shooting down the satellite opens in the next three or four days and will remain open for as many as eight days, according to Marine Gen. James Cartwright, vice chairman of the Joint Chiefs of Staff.
The Defense Department estimates that if the satellite is not intercepted, a sizable 2,800-pound (1,270-kilogram) chunk (about half its total weight) will survive reentry. The vehicle's 20-inch (50-centimeter) round fuel tank holds about 1,000 pounds (450 kilograms) of hydrazine that would have been spent during a successful mission; it was not, however, because ground control lost contact with it soon after launch. The Washington Post reported today that the shuttle Columbia contained a canister of hydrazine when it ripped apart during reentry over Texas in 2003, but that most of the toxic fuel had already burned because the doomed shuttle had nearly completed its mission.
Cartwright said that if the satellite is not shot down, its hydrazine could disperse over an area roughly the size of two football fields. He noted that anyone who inhaled the chemical, which can severely damage lung tissue, would need medical attention.
Military officials refused to release certain details—insisting that information such as the manufacturer, mission and price tag of the failed satellite is "classified." But they insist that the strike against the vehicle is not an effort to keep debris that survives the impact from falling into the wrong hands and divulging military secrets.
Cartwright positioned the situation by saying, "the worst that could happen is that we miss" (although this doesn't take into account the impact that failure could have on the environment). "If we hit the hydrazine tank, then we've improved the potential to mitigate that threat," he added. "The regret factor of not acting clearly outweighed the regret factor of acting."
The largest uncontrolled reentry by a U.S. spacecraft was NASA's abandoned 91-metric ton (200,600-pound) Skylab space station in 1979. China sparked international outrage last year when it was discovered that it had used a ground-based ballistic missile to destroy a target satellite about 600 miles (375 kilometers) above Earth. The U.S., Japan and Australia expressed concerns that China was demonstrating its ability to shoot down spy satellites and the destroyed vehicle's debris is hazardous to other orbiting spacecraft. The U.S. is hoping its concern over its errant satellite's fuel will obviate international criticism.