Where do spacecraft go to die?

THERE is no “nice farm in the country” for old spacecraft. Instead, space agencies have two options for satellites, rovers and probes whose missions have come to the end: to leave them out there or send them hurtling into the atmosphere of the nearest planet, where they will die a fiery, spectacular death.

The first option is a popular one. Earth’s orbit is clogged with more than 500 000 pieces of space junk the size of a marble or larger, according to Nasa. These bits of trash travel at up to 28 164km/h and include abandoned launch vehicle stages, space station trash, stuff astronauts lost (gloves, tool bags, a spatula), as well as abandoned satellites and spacecraft. Most space debris eventually falls out of orbit and burns up as it re-enters Earth’s atmosphere, but plenty more is still out there. Vanguard I, a solar-powered US satellite, has been hurtling around our planet since it was launched in 1958.

All this orbiting trash poses a threat to spacecraft that are still operational. In 1999, a French satellite was damaged after being struck by debris from a rocket that had exploded 10 years earlier. A window on the International Space Station was chipped by a fleck of paint.

“The greatest risk to space missions is from non-trackable debris,” said Nicholas Johnson, former Nasa chief scientist for orbital debris.

For that reason, space agencies have been collaborating to find better ways of dealing with defunct spacecraft. One option is to send them up to an orbit so high above the Earth that they are out of the way of most active spacecraft. This requires that ageing satellites save a bit of juice at the end of their lives for a burn that will boost them into their high-altitude final resting place. Nearly 325km above crowded low Earth orbit, they can spin through space for eternity.

Other spacecraft are programmed to slow down after their mission. In 25 years, they will start falling towards Earth, burning up from the heat generated by friction as they hit the atmosphere.

If engineers can’t be certain that the spacecraft will burn up before they reach the ground, they are required to program the machines to fall into the “spacecraft cemetery” – an uninhabited expanse of the South Pacific Ocean. – Washington Post