Washington - The Pentagon plans to shoot down a defective spy satellite with a tactical weapon to prevent it from hitting a populated area on Earth or spreading toxic fuel fumes, government officials said Thursday. The satellite has about 450 kilogrammes of hydrazine fuel, which could be lethal if inhaled in high concentrations, they said.
General James Cartwright, vice chairman of the joint chiefs of staff, said that the Pentagon had lost communication with the satellite shortly after it was launched in December 2006, putting it out of reach of ground controllers who could have brought it down safely.
The 2,270-kilogramme satellite will be targeted by a tactical standard missile-3 fired from a shipboard Aegis system within the next two weeks, but not until the Space Shuttle Atlantis has returned to Earth, now scheduled for Wednesday, Cartwright said in broadcast remarks.
Three ships would be deployed somewhere in the northern Pacific Ocean to fire the missile, which can reach "just beyond the atmosphere," Cartwright said.
Deputy National Security Advisor James Jeffrey said there was a "diplomatic rollout across the world" on Thursday to inform other states, as required under treaties regulating activities in space.
When China launched an anti-satellite missile to destroy an ageing weather satellite in orbit in January 2007, the United States, Japan and other countries lodged protests. Both the US and Soviet Union experimented with anti-satellite missile technology in the 1980s but abandoned their programmes out of fear that debris from such explosions in space could damage other satellites.
Jeffrey said that the situation with the US satellite was different from the Chinese case, which generated debris that has remained in orbit over a wide range of Earth's surface. Bringing down the spy satellite will generate debris that will fall out of orbit within weeks, he said.
US President George W Bush made the final decision. Jeffrey said there was "enough of a risk for the president to be quite concerned about human life."
While dozens of satellites and other man-made objects have fallen from space, Jeffrey said that this case was "a little bit different" because of the possible release of rocket fuel.
The noxious fuel, which is in a gaseous state, can be lethal as fumes that could spread over the area of several football fields, officials said.
An additional factor was the possibility the satellite could hit airborne objects including the orbiting space shuttle or International Space Station if left aloft.
Cartwright dismissed questions that the classified nature of the satellite was a factor.
The precise targeting will require the missile to hit "just prior" to the last moment before the satellite hits the Earth's atmosphere, so that some of the mass of the satellite will be burned up on re- entry and the rest fall into a safe ocean area.
"We'll use one missile with two backups," Cartwright said. "We'll have three ships on station."
The tough part could be deciding whether to take a second shot in case the satellite is only "grazed" but not directly hit, Cartwright said.
He said that the Pentagon has previously tested the standard missile 3 to intercept another missile.
