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Space Topics: Search for Extraterrestrial IntelligenceThe Search for Extraterrestrial Intelligence: A Short HistoryPart 5: Project Ozma - The Search For its time, Ozma was on the cutting edge of technology. It utilized an experimental parametric amplifier, donated by Microwave Associates, and the novel maser technology. By combining these with an 85 ft dish, Drake and his team were able to achieve a degree of sensitivity a thousand times greater than anything previously possible. The output mechanism was conventional - a simple chart recorder and a tape recorder. At the last minute the Ozma crew added a loudspeaker as well, just in case… Ozma began operations on April 8, 1960, with the aim of searching for signals from the two closest sun-like stars - Tau Ceti and Epsilon Eridani. Throughout the first morning the 85-foot dish tracked Tau Ceti and recorded radio emissions that seemed to be coming from its direction at or about the hydrogen line. Despite the early excitement, not meaningful signal was detected. In the afternoon the radio telescope was shifted to Epsilon Eridani.
In a 1981 interview Drake recalled what happened next: "A few minutes went by. Then it happened. Wham! Suddenly the chart recorder started banging off the scale. We heard bursts of noise coming out of the loudspeaker eight times a second, and the chart recorder was banging against its pin eight times a second . . . We all looked at each other wide-eyed. Could it be this easy?" It was not to be that easy. The signal disappeared, and would not be heard for several more days. When it did suddenly reappear ten days later, the Ozma team was ready: the signal, they found, was just as strong on a simple antenna rigged through the window, as it was on the big radio telescope. It was clearly of Earthly origin, most likely the emissions of a military electronic warfare plane on an exercise run. Project Ozma operated for a month, rested for another month, and then returned for another (final) month of observations. In all, it devoted 200 hours of observation to its two targets, Tau Ceti and Epsilon Eridani. It scanned 7200 channels divided equally between the 2 stars, each with a bandwidth of 100 Hz. The entire search was conducted around the central frequency of 1420 MHz, with deviations to both sides to look for Doppler drifts in the transmission frequency due to the relative motions of the Earth and the supposed source planet. While Ozma did not find a signal from an extraterrestrial society, it did become the model for most future SETI projects. --Amir Alexander |
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