The US government's official reason for shooting down the failed satellite last year doesn't fly, say some.
The blind spy satellite may harbor more than one mystery.
Last month, the Monitor reported that Pentagon officials still do not know why a 5,000 pound US spy satellite ceased functioning shortly after being placed in orbit in December 2006. After going blank, the satellite slowly began losing altitude. On Feb. 20, 2008, it was destroyed by a missile launched from a US Navy cruiser in the Pacific Ocean.
The official explanation for its destruction was that the US wanted to prevent the toxic contents of the spacecraft's fuel tank from harming people on the ground.
But no technical studies have ever been released to support this claim, according to Yousaf Butt, a staff scientist in the High-Energy Astrophysics Division at the Harvard-Smithsonian Center for Astrophysics.
The fuel was hydrazine, a substance Pentagon officials described as similar to ammonia, in that it is deadly when inhaled in large enough quantities.
In response to a Freedom of Information Act request from Dr. Butt, the National Aeronautics and Space Administration (NASA) released a white paper on the survivability of a titanium fuel tank filled with frozen hydrazine. Butt's reading of this report is that it does not support NASA's contention that the tank might have survived intact all the way to the ground.
Independent studies of the tank's re-entry hold that it would have ruptured prior to impact, he adds.
Butt, who published a technical analysis of the NASA document, says that it should be presumed that the public health reason for the satellite's destruction was legitimate, but that the US government has not released information that supports this claim.
This secrecy may only feed suspicions that the satellite was shot down for other reasons: as a test of US anti-satellite capabilities, for instance, or perhaps as a response to China's test of an Anti-Satellite Weapon in January 2007.
For now, the mysteries surrounding the blind spy satellite involve both why it failed – and why it was shot down.
"While we may never know the cause of the failure, the other mystery is being unnecessarily perpetuated by government secrecy," says Butt in an e-mail.