Friday, February 17, 2017

Point Nemo: The Spacecraft Cemetery

Far off the east coast of New Zealand, about 3,300 kilometers out in the Pacific Ocean, lies one of the geekiest junkyard in the world. It’s located in the middle of nowhere, and there is certainly no island here —just water. But four kilometers beneath the waves, the ocean floor is littered with broken fragments and debris of old satellites, space stations and spacecraft. This is the “Spacecraft Cemetery”, where space agencies around the world send their decommissioned satellites and spaceships plunging back into the earth to die.

When a satellite or an orbiting space station reaches the end of its operational life, there are two different ways to retire it. If the satellite has a very high orbit, like in the case of geosynchronous satellites, then engineers will push them out farther into space, into what is known as the Graveyard Orbit. This orbit lies several hundred kilometers above the orbit of the highest operating satellites, where the probability of colliding with operational spacecraft is generally none.

For satellites that revolve close to earth, it is much easier and fuel-economic to slow it down and let it fall back into the earth. If the satellite is small, it will burn and disintegrate completely in the atmosphere, just like hundreds of meteors do everyday. But if the satellite is large and there is the possibility that it might not burn up completely in the air, then retiring them requires a bit more planning.

The idea is to guide the satellite down into the ocean away from any significant landmass and human habitation where there can be no risk of injury from falling debris. The chosen place must also be far from shipping lanes. Such a spot in the ocean exist, and geographers call it the “oceanic pole of inaccessibility”.

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