Sometimes I envy the folks who figure they can establish extraterrestrial contact by standing in the backyard waiting for spacecraft to land. After all, the required infrastructure is pretty simple: one count em, one backyard.

Project Phoenix demands a bit more. To begin with, you need a large radio telescope -- a mammoth assemblage of steel and aluminum. The Arecibo antenna amply fills that role. But the list of necessary equipment continues: A low-noise amplifier poised at the focus, a series of intermediate amplifiers to boost the incoming cosmic static to useful levels, digitizers to convert the static to handy ones and zeroes, spectral analyzers to break up the band into 56 million channels, signal-detection algorithms, massive arrays of hard disksthe checklist is long and wearisome. But if you dont expect aliens in the backyard, this is what you need.

Its complex work, and it involves complicated equipment. Whats worse, every link in the chain has to function.

The Phoenix built-in test tone, as it appears on the projects display screens (detail -- click here for full test tone).

This is a particularly stiff requirement for SETI research. If you study pulsars and dont observe a signal pouring out of the scope, you have good reason to suspect that something is awry. But SETI signals are elusive indeed, weve yet to find a confirmed extraterrestrial broadcast. So when Project Phoenix scientists see the equivalent of blank screens, theyre not immediately alarmed.

But how do they know they shouldnt be?

Its a worrisome prospect, resulting in short fingernails all around. As a partial fix, the Phoenix engineers have arranged for a test tone to be injected into the signal path, one thats a bit like a canary in a coal mine. The tone serves to verify that both hardware and software are up and running. But there are, unavoidably, places where the test tone doesnt go and signal conditions that it doesnt create. Whats needed is a much better canary, an "end-to-end" test capable of ascertaining whether the whole kit and caboodle amplifiers to signal confirmation software is up to operational snuff.

Next page: bouncing a test signal off the Moon

~

NASA was kind enough to provide us with such an end-to-end test object: the Pioneer 10 spacecraft. Now 7 billion miles from Earth and counting, Pioneer 10s faint signal has been used for years to corroborate the correct workings of the Phoenix system. Once a day, wed swing the scope in its direction and verify an "extraterrestrial signal" from the crafts 8-watt onboard transmitter.

Alas, Pioneer 10 has gone AWOL. No one has heard its weak whine since August. NASA theorizes that the plutonium-powered transmitter may finally have died (after two dozen years), or perhaps the spacecraft is slightly turned so that its antenna no longer points to Earth.

The Galileo spacecraft, seen here near Jupiters moon Europa, was a prospective test object for SETI. Unfortunately, its signal has been tweaked in a way that makes it less useful for calibrating the Phoenix system.

Irrespective of the reason, weve lost our best canary. So weve tried to press some other NASA birds into service. In particular, the Galileo spacecraft now pirouetting around Jupiter and its moons might serve as a distant, test transmitter. Unfortunately, Galileo hasnt worked out. Its carrier signal has been deliberately suppressed. Doing this has improved the data rate for Galileos photo reconnaissance of the Jovian system, but makes the spacecraft hard to use as a SETI calibrator.

So now were trying something else: were going to look at the Moon. Paul Shuch and Richard Factor of the SETI League an organization that has put together a very clever SETI search by amateurs have been kind enough to try bouncing a test signal off the Moon when that fabled orb is overhead in Puerto Rico. Theyre doing so with a quad helix array antenna near Factors home in Kinnelon, New Jersey and feeding it with 10 watts of power.

Ten watts bounced off the Moon may not sound like much. And it isnt. In fact, only about 10 milliwatts of the transmitted power even hits the Moon, and this weak signal is then bounced back in all directions (not just toward Earth.) Imagine shining a laser pointer at the Moon in the hope of seeing the reflected light.

Fortunately, radio technology is good. You can work it out yourself, but the amount of signal coming back from the SETI Leagues Moon bounce should be about one thousand billion-billionth of a watt per square meter. Its not going to heat the grass. But even this incredibly weak signal is a piece of cake for the Phoenix system at Arecibo: its about a thousand times more powerful than the detection threshold.

It may be our best hope this observing run for a system test. Theres no doubt about it: the backyard approach to alien discovery doesnt require too much equipment checkout. But a scientific observing program does. So in the coming days well be periodically aiming Earths biggest "satellite" dish at, well, Earths biggest satellite.