Rory Johnston
Operators of Earth satellites will be holding their breath on November 17 as Earth sails into the worst meteor storm for 33 years. Particles travelling at 240 000km/h will crash into virtually every satellite, and the damage could be slight or it could be enough to put satellites out of commission entirely.
Every November, Earth crosses a stream of comet debris circling the sun. The meteors we see then are called Leonids, as they appear to emanate from the constellation Leo. But, every 33 years, Earth encounters a clump of debris thousands of times denser.
The significance of the imminent encounter is that in 1966 there were fewer than 100 satellites orbiting Earth. There are now more than 500 and they have become crucial to telephone and television communication, to say nothing of navigation, weather forecasting and defence systems.
Last week, aerospace engineers from around the world met in Los Angeles to explore the size of the problem and what can be done about it. Chairing the conference was David Lynch of the Aerospace Corporation, a think-tank funded by the United States government to advise the air force and private organisations. He points out that while the meteoroids are travelling very fast, most are small. “One the size of a grain of sand would be considered large,” he says.
This means that few will actually smash their way into or through a satellite. Instead, the energy of the impact can generate an electromagnetic pulse that is enough to disrupt the electronics of the satellite. The heat of the collision can also vaporise the particle and part of the spacecraft skin to a highly corrosive plasma that causes electrical discharge. “This can affect many aspects of the spacecraft,” says Lynch.
At this late stage it is not possible to launch space “umbrellas” to protect satellites, but engineers are exploring a number of precautions. One is to turn a satellite so that it is flying sideways into the storm, presenting the slimmest possible target. The Hubble space telescope will turn its precious mirror away from the stream.
Another step is to power down a satellite so that there is no electrical activity to disrupt. The danger with that, Lynch points out, is that you might not be able to turn it on again.
Some large satellites, mainly military, have manoeuvring jets that could be used to move them to safer orbits. All these are options the operators will have to juggle with, balancing the losses from a satellite being switched off for a few hours to the risk of losing it permanently.
Organisations such as Intelsat will have “tiger teams” of experts standing by to take remedial action if damage occurs.
And having got through November 17 this year, they will then have to face the same date in 1999, which some astronomers think could be even worse.