A Tone From the Deep

March 7, 2002

by Seth Shostak - Senior Astronomer

Arecibo, Puerto Rico
Once again, the SETI institute has returned to the world's largest telescope to continue its research. Follow the institute's progress in Puerto Rico here at SPACE.com with Project Phoenix astronomer Seth Shostak's reports from the front. This is the first installment.

We’re baaack!

Once again, members of the Project Phoenix team have returned to the big antenna on the small island of Puerto Rico, continuing their search for radio whispers from distant civilizations. Outside the window of my office, only a few dozen yards away, hulks the Arecibo radio telescope.  It is a twenty-acre nerve ending of aluminum mesh, exposed to the sky and carefully attuned to regularities in the radio noise that pervades the cosmos.  For three weeks, we will aim this enormous metal neuron at nearby star systems, hunting for signals produced by extraterrestrial intelligence.

The Phoenix equipment – specialized digital electronics capable of sifting through 57 million channels at a time – sits in a trailer outside the Arecibo control room.  We never move the trailer, but simply fire it up each time we come to the telescope.  This requires both time and expertise, as the Phoenix team coaxes a mass of squirrelly electronics out of dormancy.  A crucial part of the startup is to make tests, to be sure that this complicated system is working as advertised.

The most compelling of these tests are the short observations of the far-off planetary probe, Pioneer 10.  Launched in 1972, NASA’s first emissary to the outer solar system is still capable of making weak radio broadcasts, and its distant signal is a perfect ping for our system.

Unfortunately, Pioneer 10’s on-board reference oscillator failed in 2000, twenty-eight years into a five-year mission.  The craft’s radio squeal became unpredictable and impossible for us to find.  But thankfully, not all was lost.  NASA can still prod Pioneer 10 into transmission by sending it a reference tone from Earth.  Of course, since Pioneer 10 doesn’t speak unless spoken to, we have to rely on the space agency to turn on its cheeky chirper.

In anticipation of our return to Arecibo, Phoenix team leader Peter Backus rang up NASA’s Pioneer office in December, to see if they had plans to bestir the spacecraft.  “No dice,” was the reply.  NASA’s world-wide phalanx of communication antennas – the Deep Space Network (DSN) – was already heavily booked, with no opportunity for any wakeup call to Pioneer 10.  It looked as if our best test was simply not going to be available.

This discouraging story took a turn for the better when someone at NASA realized that March 2 would be the 30th anniversary of the spacecraft’s launch.  Why not make a celebratory contact to mark humankind’s first mission to Jupiter and beyond?  The DSN managed to paw some room in their schedule, and prepared for a three-hour broadcast to Pioneer 10.

Hearing the news, Backus sought permission for some extra telescope time at Arecibo and at our confirmation telescope at Jodrell Bank, England. He got it. The next step was to cajole the Phoenix hardware back to life, while simultaneously dealing with such major annoyances as a dead power generator at Arecibo and a mechanical failure at Jodrell Bank. Large radio telescopes are, after all, complex devices that sit out in the weather. Malfunctions and mechanical difficulties come with the territory.

Despite the hurdles, all systems were “go” at Arecibo on March 2, and the signal from Pioneer 10 came booming in like a Valkyrie. It was not E.T., but the signal from this spacecraft was still impressive: a broadcast from 7.4 billion miles away, nearly twice Pluto’s distance, and one that takes 11 hours to make its way to Earth. Thanks to the Pioneer test, the Phoenix team can now search for alien transmissions with confidence. Watch this space for additional reports that will chronicle our current observing run.

“It was like seeing an old friend,” says Peter Backus, speaking of the Pioneer 10 test.  But can you call a thirty-year old spacecraft ‘old’?  “Sure,” Peter says with a smile.  “After all, it’s not the age – it’s the mileage.”