The near-death of the Huygens probe

You know the Doppler effect? It’s the way that waves emitted by a moving object will appear to change as the object races by you. The most common example is the way an ambulance siren appears to rise in pitch as it approaches you, then fall as it moves away. As the ambulance approaches, the waves are hitting you more and more quickly; as it recedes, they hit you more and more slowly. Spacecraft and satellites, which move at incredibly fast speeds, continually run into the Doppler effect, so astrophysicists are pretty accustomed to dealing with it.

But apparently the Huygens probe was nearly doomed by the Doppler effect. The Hyugens probe, as you may recall, is the little planetary explorer that is currently riding along on the school-bus-sized Cassini probe as it orbits Saturn. In January, Huygens will detach from Cassini and descend to the surface of the Saturnian moon Titan. And that’s where the trouble begins. According to IEEE Spectrum Online, the communications equipment between the Cassini and Huygens was badly designed — such that the Doppler effect would render unintelligible any data coming from Huygens. If the probe discovered enormous tentacled methane-breathing telepathic squid-based life-forms, we’d never know, because the probe’s signal would be indecipherable. Sucky, eh?

But the really cool thing is how the error was discovered. It was all the work of a lone Swedish engineer, who discovered the error late one night — and had barely hours to design a set of experiments to prove it would really screw the Hyugens mission. Sure, it’s a story about spectrum engineering — but it reads like a page-turner thriller by Michael Crichton. Check it out online here!

The upshot is that the error was fixed, in the nick of time. But, as the lead engineers admitted:

We have a technical term for what went wrong here,” one of Huygens’s principal investigators, John Zarnecki of Britain’s Open University, would later explain to reporters: “It’s called a cock-up.”

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I'm Clive Thompson, the author of Smarter Than You Think: How Technology is Changing Our Minds for the Better (Penguin Press). You can order the book now at Amazon, Barnes and Noble, Powells, Indiebound, or through your local bookstore! I'm also a contributing writer for the New York Times Magazine and a columnist for Wired magazine. Email is here or ping me via the antiquated form of AOL IM (pomeranian99).

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