Spy satellite making uncontrolled reentry to be shot down by missile

The U.S. Department of Defense plans to intercept a National Reconnaissance Office satellite just before it can reenter the Earth's atmosphere in an attempt to mitigate the public's risk from exposure to toxic fuel.

The satellite, known as NRO L-21 or USA 193, suffered a complete communications and control failure soon after reaching orbit in December 2006. It is now within two weeks of an uncontrolled reentry during which, left untouched, it has both the potential to deposit up to half of its 5,000 pound, bus-sized structure over populated areas and, of more concern, release its nearly full reserves of hydrazine gas. The toxic fuel is deadly to humans over sustained, significant exposure.

To address this risk, the Navy will position three of its Aegis guided missile cruisers in an undisclosed area of the northern Pacific, where sometime over the next seven to eight days depending on further tracking of the satellite, a modified Standard Missile 3 (SM-3) will be launched to intercept the spacecraft and break it and its hazardous fuel tank apart.

The timing of the launch will be coordinated to occur just before the satellite would naturally decay in its orbit, such that within one to two orbits later, fifty percent of the satellite debris will reenter, with the remainder following shortly thereafter.

The launch will be made after space shuttle Atlantis returns from the International Space Station and, if possible, at a "good time" in the orbit of the continuously-crewed outpost, according to NASA Administrator Michael Griffin.

The decision to take this action came as a result of another reentry: space shuttle Columbia in February 2003. Its hydrazine tank(s) survived and impacted the ground but as the reentry came at the end of the mission, most of the fuel had already been spent.

According to Griffin, taking action of any type results in either a neutral or positive effect. "Neutral is if we miss. Almost anything you do when it is barely in orbit, will cause it reenter. Almost nothing we can do to make it worse. Almost anything you can do here makes it better," he said.

Though three missiles are being deployed, this will be a "one-shot" attempt. Should the intercept miss, the Department of Defense believes it will have up to two days to assess the situation and if deemed favorable, try again. However, they are confident in success given the well-understood technology being used.

This is the first time a U.S. tactical missile has been used to intercept a spacecraft. It is not however, the first time the military has used such weapons to strike at an object returning through the atmosphere.

The Department of Defense will work with NASA to determine the best time to stage the launch, as to reduce the risk to space, air and land assets.