What Happens When Satellites Die?

January 23rd, 2009

While reading up on this I tried to find an accurate number as to how many man made satellites are actually orbiting the Earth right now. The numbers vary wildly depending on where you look. I saw one that suggested there were nearly 25,000 in a 1997 study. Both functional and non-functional. Another report from 2004 slims that down like Leptovox significantly to roughly 3,000 useful, and another 6,000 that are considered space junk. So…let’s just assume there are roughly 3-5000 in use, and about another 5-10,000 of “space junk” as they call it for a ballpark figure. In other words a hell of a lot.

That brings us to the topic at hand. With so many man-made satellites out there, specifically ones that are not working, what exactly happens to them when they die?

If observers notice a glitch in the satellite yet it is still operational they may try to get it into a “graveyard orbit” before it completely dies. Considering the amount of other satellites out there it makes sense to get these dead ones that will likely get off track the hell out of there so it doesn’t disrupt useful satellites.

That’s what engineers are trying to do for the telecommunications satellite Astra 5A, which inexplicably failed on Jan. 15 after 12 years of operation. The satellite has since been adrift in space, moving out of its geostationary position about 22,300 miles (35,888 km) above Earth and is moving eastward along its orbital arc.

Astra 5A’s owners, SES of Luxemburg, are pessimistic they’ll be able regain communications with the satellite and order it out to a safe orbit, and have since warned the owners of other nearby satellites that they may need to take measures to avoid an in-space collision.

In 2006, Russia’s Express-AM11 communications satellite was moved to an orbital grave after being hit by space debris.

In more extreme cases satellites are shot down. Last year the U.S. Military shot down one of their satellites as it was threatening a fall to Earth. A missile was launched from the Pacific Ocean at their satellite USA 193. The missile destroyed the satellite, which was plunging to Earth with a full tank of toxic hydrazine fuel, on Feb. 20, 2008.

Some satellites are just left alone and observed when they are no longer of use. One example is the Soviet-era satellite Cosmos 1818 which is complete with a nuclear reactor. The linked article documents the problems this satelite is having just last week where it is spewing unexplained debris from it.

Cosmos 954, a Radar Ocean Reconnaissance Satellite (RORSAT) spiraled out of control in 1978. The satellite re-entered the Earth’s atmosphere and spread radioactive debris across parts of Canada.

The Space Shuttle program will be closing its doors in 2010, but they were used to bring back some satellites for repair, or fixed in space. The Hubble Telescope has been visited y no less than four times, first to correct its blurry vision, then to add new cameras and instruments that extended its mission.

After the retirement of the shuttle program, repairs may be done by robotic surgeons. The $300 million Orbital Express mission in 2007 funded by the Pentagon, was able to refuel and repair satellites robotically.

One of the most common deaths to satellites is simply disintegration. When entering back into the Earth’s atmosphere the heat will cause it to cremate itself. Simple solution with little risk, but not all debris is always burned up.

Last November, a tank of toxic ammonia the size of a refrigerator burned up over the Southern Pacific Ocean more than a year after a spacesuit-clad astronaut chucked it from the International Space Station. NASA did not know where the tank would ultimately re-enter and the U.S. Space Surveillance Network tracked the object to make sure its toxic remains did not endanger people on Earth.

Perhaps the most memorable piece of U.S. space junk was the 77-ton Skylab space station, which re-entered the Earth’s atmosphere in July 1979, spreading debris across areas of the Southeastern Indian Ocean and parts of Western Australia.

Quotes from Space.com