Fall 2002 Issue

Small amateur radio telescopes such as this one are springing up in backyard gardens all around the world as part of the Project Argus all-sky survey for signals of intelligent extra-terrestrial origin. (SETI League photo)

DR. SETI’s
STARSHIP

Searching For The Ultimate DX

 By Dr. H. Paul Shuch,* N6TX

Before its funding was terminated by Congress in 1993, NASA’s two-tined SETI (Search for Extra-Terrestrial Intelligence) program relied on a pair of distinct but complementary research elements: a targeted search of nearby Sun-like stars, and an all-sky survey for interesting signals of unknown origin.

The former, which involves aiming at likely candidate stars for long periods of time, is well suited to large, steerable dishes with their narrow beamwidths and high sensitivities. Frank Drake’s Project Ozma effort of 1960, which we discussed in the summer issue of CQ VHF, was a targeted search, concentrating on two nearby sun-like stars for evidence of technological life.

It was a sensible way to launch modern SETI. After all, if we guess right as to which stars constitute likely candidates, the targeted search will provide us with the greatest likelihood of immediate success. However, we know of only a limited number of relatively nearby candidate stars. Thus, concentrating our search in their direction may cause us to miss an equally good star of which we happen to be unaware.

An all-sky survey, on the other hand, makes no a priori assumptions as to the most likely direction to explore. The sky survey seeks to sweep out the entire sky as seen from a given location. No antenna tracking is required because it is the entire sky, rather than individual stars, which we scan. While target-search antennas must constantly be moved, sky-survey radio telescopes are operated in what is called drift-scan, or meridian transit mode. It is the Earth’s rotation which turns them.

The best known of all the all-sky surveys was conducted for a quarter of a century from the Big Ear radio telescope, built by the late Dr. John Kraus, W8JK, at the Ohio State University radio observatory. That telescope sadly is gone now, an historical loss which will be the subject of a future column.

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