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Blasting the spy satellite: The secret’s out

  • February 19, 2008 7:59 AM |  
  • By Quirks

By Bob McDonald, host of the CBC science radio program Quirks & Quarks.

The U.S. military will soon shoot down one of its own spy satellites, before it falls uncontrollably back to Earth. Pentagon officials say the interception of the wayward satellite is for safety reasons, but it’s also an opportunity to test their controversial missile defense system.

According to the military’s internal newsletter, the errant spy satellite was launched in Dec 2006 and immediately lost communication and control from the ground. Since then, the bus-sized instrument has been tumbling uselessly through space, a very expensive piece of space junk.

Of course, there are no specific details on the satellite because it is, after all, for spy purposes. But it is big, with a mass of seven or eight metric tonnes. The biggest problem, officials say, is the fuel tank, which is still full of rather nasty stuff called Hydrazine.
More importantly, there is the hazard posed by the fact that this uncontrollable piece of military hardware could come down anywhere in the world.

Spy satellites tend to follow polar orbits, which carry them around the Earth in a north-south direction, passing over each pole on every orbit. While the satellite maintains this orientation, the Earth turns under it; so every 24 hours, the satellite sees the entire surface of the planet. That’s great for spying because no part of the Earth is out of sight.

The satellites are also on very low orbits, usually just a few hundred kilometers up, so their cameras can get the best resolution images of enemy bases, training camps or any other place the military finds interesting.

Normally, dead satellites are driven into the Pacific Ocean where any debris that doesn’t burn up in the atmosphere falls into uninhabited waters. But this satellite is completely out of control, which means it could come down anywhere on the planet, and no one can predict where it will hit until its final orbit. The satellite will be brought down by friction with the Earth’s atmosphere, but an un-aerodynamic shape tumbling into an atmosphere that changes daily has a huge uncertainty factor. In other words, ground zero won’t be known until about an hour before impact.

By the way, the impact of this satellite won’t involve a flaming fireball that shoots down from the sky, wiping out a city, as depicted in Hollywood movies. Most of it will burn up high in the atmosphere. But some of the hardier pieces, including the fuel tank, could make it to the ground as a rain of debris. Think of throwing a bunch of car parts off a very tall building. While not as dramatic, it’s still not something you want landing on your head as you walk down the street.

And of course, some of that debris may contain some highly sensitive spy technology, which the U.S. wouldn’t want to fall into the wrong hands.

Shooting down a dead satellite isn’t an easy matter, for two reasons. First, you’re not allowed to blow it up because of international space treaties; and second, just trying to hit it is really hard. Actually, sending up a high-explosive warhead to destroy the satellite would be somewhat easy because when it comes to bombs, close counts. But the 1967 Outer Space Treaty, which the U.S. has signed, prohibits placing weapons of mass destruction in space.

So, to get around that treaty the clever folks at The Pentagon have designed the Missile Defense System to send up something that simply collides with another satellite at high speed. And in space, speed is no problem. Satellites in low orbit are moving more than 30,000 kilometres per hour, or 10 times the speed of a rifle bullet.

But hitting something moving that fast with another high-speed object is like trying to hit a bullet with a bullet. There is absolutely no room for error.

Satellites have been knocked out of orbit before. Last year, the Chinese blew away an old weather satellite, an act that was highly criticized by the U.S.

The U.S. claimed that the destruction was a violation of Weapons In Space Agreements and the debris produced by the destroyed satellite posed a hazard to other spacecraft, including the International Space Station and the Space Shuttle. On that last point, they were right. The Chinese satellite was in a much higher orbit and its debris will remain in space for years. This current one will be struck just before it enters the atmosphere and is expected to be completely down in less than a week.

But now the U.S. has to eat some crow by admitting that it, too, has anti-satellite technology - even if it doesn’t involve high explosives. And while the officials right up to the White House are saying it’s being done for safety reasons, there are surely people in the Pentagon rubbing their hands together with glee over the opportunity to put their space weapons to a real test.

Is this the new space race?

- Bob McDonald

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