Jill Tarter

We thought we had it! Peter Backus modified our observing software to look for fainter signals, buried deeper in the noise, and we used that last night. Just at the frequency where we predicted we’d find Pioneer 10, we did see a signal. A little middle-of-the-night elation—sadly all too short-lived. As always in this business, we did some checking. Fiddling with our hardware setup (note the technical term!) let us determine that the signal was a real signal (not noise), but it was intrinsic to our own equipment. The signal is always there, it’s usually ignored. Our software mods brought it to the attention of our observing system. Too bad. We’ll keep looking for P10 and E.T.

So far it has been a day of simple pleasures; local chinas (yellow-green oranges) and baby bananas bought from an old school bus that never leaves the side of the road, a shipment of Peet’s coffee arriving from home, and a little extra sleep. My observing shift ended a few hours early this morning, and we will not be observing tonight. Instead, Eric Splaver is doing a 22-hour marathon of pulsar timing. Pulsars are rapidly rotating neutron stars with special properties that make them act like radio lighthouses. Many times a second, a pulsar’s radio beacon sweeps across the Earth, and the Arecibo telescope hears a pulse. Each pulsar has its own unique rate of rotation, thus a signature period; some of them even have nicknames such as the “E-Flat” pulsar that is rotating over 650 times a second. Studying how these periods change over time helps to understand the physics of these remarkable objects. When they were first discovered, by Jocelyn Bell Burnell and Antony Hewish in 1967, they were called LGMs (for little green men) because at first it was hard to believe that astrophysics could produce such precisely periodic pulses. Alas, these beacons are natural, not artificial—I’m still looking for the latter! Like the solar-type stars that Project Phoenix points to, pulsars can be found in most parts of the sky. Thus pulsar astronomers and SETI researchers would use Arecibo all day, every day, if they could. We can’t. Other scientists want to conduct their observing programs. For now we have to divvy-up the time on the telescope, but in 2005 that will change.

The SETI Institute and the University of California Berkeley Radio Astronomy Lab are building a new radio telescope, thanks to the generous donations of Paul Allen and Nathan Myhrvold. The Allen Telescope Array (ATA) won’t be quite as big as Arecibo, but from my point of view it will be better. Since it’s being built by connecting together 500 small telescopes each of which is 5 meters in diameter, it will allow SETI researchers to use the array continuously, 24-7, at the same time as pulsar astronomers and other astronomers. No, we won’t each get a little antenna! The output from all 500 dishes will be combined together in different ways to make the array point simultaneously in the different directions where our target sources lie. This array is more about massive parallel processing than it is about the steel and aluminum of traditional radio telescopes. The number of beams on the sky that we can synthesize simultaneously is limited by how much computation we can afford. Thanks to the economics of Moore’s Law, that’s improving daily.

Until the ATA is available, I’ll keep coming back to Arecibo with my team for three weeks every six months. We’ll share the telescope and enjoy the simple pleasures here, and perhaps capture a signal from a distant technologist. 

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Note: On Tuesday, Slate posted an erroneous headline on the Table of Contents that described SETI’s work as “searching for UFOs.” SETI does no such thing, and click here to find out why not. Slate sincerely regrets the error.