Defunct Satellite To Fall From the Sky

Front page first-timer EmLomBeeNo sends word of a 6.5-ton satellite that will soon be making a quick and fiery return to Earth. From Space.com: "The huge Upper Atmosphere Research Satellite (UARS) is expected to re-enter Earth's atmosphere in an uncontrolled fall in late September or early October. Much of the spacecraft is expected to burn up during re-entry, but some pieces are expected to make it intact to the ground, NASA officials said. The U.S. space agency will be taking measures to inform the public about the pieces of the spacecraft that are expected to survive re-entry." According to a NASA press conference today, you have a 1-in-21 trillion chance of being hit by falling debris. Who's feeling lucky?

Yeah, so I don't understand the decision here

[JoshuaZ]

So apparently they used the remaining fuel a few years ago to move it into a more rapidly decaying orbit. If they had enough fuel to do that why not just deorbit the whole thing in a controlled fashion and aim it at an ocean? We've done that before. Obviously these are some very smart people but it seems weird that they'd have exactly enough fuel to put it into a rapidly decaying orbit but not enough fuel to handle that last little bit.

On the bright side, the danger from deorbiting satellites is pretty small. The biggest actual problem that has occurred when a Soviet satellite with radioactive material decided to scatter itself over a large part of Canada back in the 1970s http://en.wikipedia.org/wiki/Kosmos_954 [wikipedia.org]. When the US space station Skylab pulled a similar stunt over Australia, the local government fined NASA a few hundred dollars for littering.

Re:Chance

[Ruke]

Yep. TFA [space.com] puts the odds at about 1:3200, actually.

Re:Odds?

[jandrese]

The actual odds for shuttle failure on each launch were calculated to be about 1 in 100, which ended up being pretty close to reality.