In The New and Improved SETI, the SETI Institute’s Seth Shostak weighs in on the Allen Telescope Array, the radio telescope installation that should give a boost to the SETI search as well as offering key research tools to more conventional astronomy. Shostak lists three advantages the ATA will offer SETI researchers, perhaps the most important being the array’s ability to make maps of the sky. “In other words,” says Shostak, “it’s like a radio camera, producing images.” Here’s his explanation of one ATA advantage:
…the ability to break up a large field of view into small (radio) pixels is also good for the SETI crowd. Consider this: you’re a radio astronomer, and your day job is mapping stuff like the Andromeda galaxy. You want your radio pixels to be in a regular, row-and-column matrix, like the members of a marching band. It’s a pixel arrangement similar to what your digital camera’s CCD has.
Fine. But for SETI purposes, you could spread the pixels around a bit, like a few grains of sand thrown onto a black piece of paper. The idea is to arrange those pixels to land on nearby stars – the very neighborhoods you wish to search for alien-generated signals. So now instead of having one soda straw to view the sky, you have a fist-full, each carefully aimed at a likely stellar system.
Another benefit of this capability is that, since these radio pixels are produced with computation, rather than being etched on silicon, you can make negative pixels – small patches of sky where you don’t pick up any signals. That’s useful not so much for blocking unsavory signals from tasteless extraterrestrials, but rather for blocking the interfering screech of our own, orbiting telecommunications satellites.
Shostak’s other points: ATA will offer an extremely wide field of view and will be far less expensive to build than a single, huge dish because the mass of steel needed to keep a big radio reflector from collapsing increases dramatically with size. Shostak says that ATA will grow to 33 dishes by spring; its first SETI assignment will be a slow scan of the inner regions of the Milky Way. “This is a test bed project certainly, but it’s also a valuable SETI experiment,” Shostak adds. “And as the ATA continues to expand, so do its speed and abilities.”
On the horizon for SETI: a new feed at the Arecibo dish will speed searches by seven times. And a Harvard instrument designed to look for extraterrestrial laser signals will soon add optical SETI to the repertoire.