US officials over the weekend announced that they had lost control of a US spy satellite and that it is expected to fall to Earth sometime next month. They have no idea where it will impact and unlike other reentries of space hardware -- this one can't be controlled since the vehicle is not responding. According to a New York Times article, people who follow spy satellites think that the satellite they are referring to is an experimental imagery satellite built by Lockheed Martin and launched on a Delta II in December of 2006. The article also quotes Jonathan McDowell, creator of the Johnathon Space Report that independently tracks all space launches for his expert opinion. His comment? The orbit has already dropped to 275 km, an altitude that is impractical due to the heavy atmospheric drag.
This won't be the first time a satellite has fallen out of the sky. In 1978, a soviet nuclear powered spy satellite fell in northwest Canada (in a very sparsely populated region). Other satellites have fallen into the ocean (a high probability given how much of the Earth is covered in oceans).
Well, not 'fall out of the sky' exactly. It is more like slowly de-orbit. Each orbit the spacecraft, now with no ability to re boost itself when necessary slowly loses altitude (McDowell claims it dropped 15-20 km in the last few weeks). As the spacecraft gets lower it starts to hit more an more of the upper atmosphere which slows it down even more. A spacecraft like the Russian Progress vehicle, used to carry cargo to and remove garbage from the International Space Station, can be brought down so that it is sure to burn up in the atmosphere.
A satellite that we do not have control over would just de-orbit on its own and could potentially not burn up completely on reentry but rather leave bits of the spacecraft bus that can hit the Earth.
Larger structures like the US Skylab facility and the Russian Mir space station were too large to burn up completely on reentry, but the Russians were able to uses thrusters to de-orbit Mir in the largest expanse of ocean they could find, the South Pacific. Skylab teams however had to confront a completely uncontrolled de-orbit for Skylab, luckily the structure hit in a remote part of Australia.
Any bets on where this one will hit? Where ever it is, don't take home the pieces, hydrazine reaction control thruster fuel and batteries can be bad for your health...
US warns satellite will fall to Earth soon [LA Times]
US Spy Satellite, Power Gone, May Hit Earth [New York Times]
