Winter 2004 Issue

 By Dr. H. Paul Shuch,* N6TX

Anomalous signal detected by SETI League members Ken Chattenton, G4KIR, and Trevor Unsworth, GØECP, on May 10, 1996, at 1471.5 MHz, using a surplus 3.5-meter dish. The signal exhibited clearly audible digital modulation, with a 270-Hz bandwidth. Its Doppler shift of –25 Hz/min. marks it as RFI from a Low Earth Orbit (LEO) satellite. Though clearly not of extra-terrestrial origin, this signal gave Project Argus its first real workout, testing both the sensitivity of our receiving stations and our ability to recognize terrestrial and satellite interference. (GØECP image)

“We’re getting a carrier, all right,” confirmed Trevor, who was barely able to conceal his excitement.
Ken’s fingers flew over the keyboard, his eyes never leaving the monitor. “Frequency?” he asked.

“Fourteen seventy-one point five,” answered Trevor, tweaking the tuning dial on the ICOM 7000 receiver. “It’s steady at S2. I’ve marked the local sidereal time. Shall I ring up the BBC?”

“Are you daft, man? Let’s not forget the verification protocols! Check for modulation, and be quick about it.”

“It’s CW. . . . No, there are sidebands. Looks kind of like modem tones. Low baud.”

The two English radio amateurs were manning their radio telescope, much as they had during every spare waking hour for the past three weeks, in search of an intelligent signal from the stars. As UK Co-Coordinators for Project Argus, the all-sky survey launched by The SETI League on Earth Day, April 21, 1996, their job was to assist other British hams in building sensitive microwave listening posts. Their 3.5-meter diameter dish and associated electronics were put together as a demonstration station, and now they were demonstrating the patience and deliberation for which their 100 combined years had uniquely prepared them. They were systematically analyzing an anomaly.
“Doppler’s kind of high. Tens of Hertz per minute. I’m betting it’s a LEO.”

Ken’s colleague knew that Low Earth Orbit satellites were the bane of SETI, the scientific Search for Extra-Terrestrial Intelligence. Fortunately, their Doppler shift, a change in radio frequency caused by their motion relative to the Earth, made such manmade sources readily distinguishable from signals of interstellar origin. Still, there was something odd about this particular signal.

The Argus concept had been born in the States a year and a half earlier, in response to Congress canceling all of NASA’s SETI funding. For just a couple of years NASA had conducted a modestly funded SETI effort from headquarters at the Ames Research Center in Mountain View, California. Consuming just one tenth of one percent of NASA’s science budget, or about five cents per American per year, NASA SETI promised to be one of the best scientific bargains of all time. Then the budget-balancers axed it, reducing the US national debt in the process—by point zero zero zero six percent.
A group of American microwave experimenters was not about to let the search die for lack of intelligence in Washington. Ken Chattenton, G4KIR, and Trevor Unsworth, GØECP, had heard about their amateur effort at the World Science Fiction Convention in Glasgow the previous summer, and they were the first Europeans to sign on. Now their many months of effort and training were being put to the test.
 

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