Not the usual channels

摘要

On July 1st, a spacecraft called Cassini went into orbit around Saturn-the first probe to visit the planet since 1981. While the rockets that got it there are surely impressive, just as impressive, and much neglected, is the communications technology that will allow it to transmit its pictures millions of kilometres back to Earth with antennae that use little more power than a light-bulb. To perform this transmission through the noisy vacuum of space, Cassini employs what are known as error-correcting codes. These contain internal tricks that allow the receiver to determine whether what has been received is accurate and, ideally, to reconstruct the correct version if it is not.