When SMART-1, the European Space Agency’s first mission to the moon, launched in September 2003, astronomers hailed it as the testing ground for a revolutionary and efficient solar-electric-propulsion technology. While this technological leap absorbed the attention of scientists and the news media, a second, quieter revolution aboard SMART-1 went almost unheralded. Only a small band of mathematicians and engineers appreciated the quantum leap forward for digital communications. Incorporated into SMART-1’s computers was a system for encoding data transmissions that, in a precise mathematical sense, is practically perfect.
Space engineers have long grappled with the problem of how to reliably transmit data, such as pictures and scientific measurements, from space probes back to Earth. How can messages travel hundreds of millions of miles without the data becoming hopelessly garbled by noise? In a less extreme situation, as any cell phone user can attest, noise is also an issue for communication systems on Earth.