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SETI
- Allen Telescope Array
- Optical SETI
- Interstellar Message Construction
- Project Phoenix 1995-2004
- Background Science
- History of SETI
- Center for SETI Research Team
- Other people doing SETI
- Hollywood's View of SETI
Past Observing Campaigns:
Arecibo, Puerto Rico
t looks like the mother of all bird baths. A thousand feet across, the Arecibo Radio Telescope crouches within a natural bowl in the undulating limestone karst of northern Puerto Rico, its massive, unblinking aluminum eye fixed on the heavens. In a field where size does matter, the Arecibo instrument takes the cake: it is the world's most sensitive radio telescope by far. Project Phoenix has just begun its first observing run in Puerto Rico.
After more than a year of listening with the Green Bank 140 foot antenna, the Phoenix team is now scrutinizing nearby star systems with an instrument forty times more sensitive. A weak signal that could easily remain inaudible to other telescopes will become an unmistakable shout when Arecibo's giant metal ear is cupped in its direction.
For many of the team members, coming to Arecibo prompts bittersweet nostalgia. Almost exactly six years ago, the Targeted Search component of NASA's SETI program began here, accompanied by impressive pomp and fanfare.
A year later, with the search still getting under way, Congress stopped the NASA effort. But equipment developed as part of the canceled program is once more being fired up for use by SETI, as Project Phoenix picks up where the NASA experiment left off. The wide band L-band receiver now being used to eavesdrop on frequencies between 1.2 and 1.75 GHz was originally part of the NASA SETI program.
The current Phoenix run is scheduled to extend from September 10 to October 6, with a few days break around the equinox. The Mountain View scientists have the graveyard shift: the telescope is theirs from 6:00 pm to 6:00 am. Nearly every morning at 5 o'clock, the telescope's tightly focused beam is set on the Pioneer 10 spacecraft which plies the silent darkness of the outer solar system, more than one-and-a-half times the distance of Pluto. The spacecraft's transmitter, which after two decades of service broadcasts with only a few watts power, serves as a valuable target in an end-to-end test of the Phoenix system. The tests are good: Pioneer 10's signal has come in loud and clear. The search for more energetic transmitters, situated about other stars, has just begun.
Sept. 15
Every afternoon, sometime between 12:00 and 3:00 pm, the clouds roll in and relieve themselves on the telescope. This rainy ritual is usually accompanied by dramatic bursts of lightning and thunder claps like breaking redwoods. The storms are an inconvenience, producing mud and mosquitoes, but they do serve to moderate the torrid heat and humidity that normally drives visitors to the air conditioned refuge of the control room.
Despite the fact that this is Project Phoenix's first sojourn to Arecibo, the receiving system came to life quickly. This is somewhat unexpected, given the fact that this highly complex system of amplifiers, digital analyzers, and a few hundred thousand lines of computer code must be connected to telescopes in Arecibo and Jodrell Bank. The latter instrument, the 250 foot antenna that is England's largest radio dish, serves to check out interesting signals that are first found with Arecibo's 1,000 foot metal ear. But the easy start made by Phoenix down the road of discovery has become bumpy. For the last two nights, observations, particularly at frequencies outside the protected band that surrounds 21 cm wavelength, have been hobbled by cacophonous interference. Some of this was traced to a noisy multimeter which produced a nice comb of signal spikes every 187 MHz on the dial.
Switching off the offending piece of hardware was easy once it was found, but other sources of interference continue to dismay the Phoenix astronomers. There are strong radars in Puerto Rico whose signals inevitably leak into the receivers. Some bands are so clogged with terrestrial noisemakers that they are simply skipped.
Other teething troubles have occurred. The Phoenix system takes charge of both the Arecibo and Jodrell Bank telescopes, first directing them to the star under observation, and then tracking these stellar neighbors as they parade across the sky. This requires that the Phoenix software talk to the local telescope software. The latter doesn't always listen. Other problems include recalcitrant bits of hardware at both sites, and a power supply that opted to commit suicide. It didn't leave a note.
A reporter covering the start of Project Phoenix in Arecibo claimed to be surprised by the complexity of a SETI experiment. It is this complexity, involving specialized hardware, software, and the assorted paraphernalia of two major telescopes, that makes it all the more remarkable when the system works. And more and more often, it does.
Sept. 17
It was near midnight when observation of a routine star, number 4079 in the Phoenix list, became very non-routine. This star, whose slightly more familiar name is EQ Pegasi, is an M-dwarf, a bit smaller than our own sun, and 21 light-years distant. Otherwise unremarkable. Jill and I were stepping up the band on this star for less than an hour, taking data in 20 MHz chunks every four minutes. On our methodical climb up the spectral ladder, we had just reached 1210 MHz. I noticed that the system control software had scheduled a "confirmation off" observation. The programs do this whenever a signal is detected that survives all the automatic tests conducted at both Arecibo and Jodrell Bank. There is little notice and no fanfare, for after all, such a signal is found a few times a night. During the off observation, the Arecibo telescope is re-pointed and aimed away from the star system under scrutiny. Any real alien signal would, of course, go away. Terrestrial interference, on the other hand, which could be leaking into the telescope from the sides, probably wouldn't. Nodding the telescope is a good way to sort E.T. wheat from earthly chaff.
This time, the signal did go away, an unusual occurrence. The Phoenix software, oblivious and unemotional, reacted accordingly and it scheduled a "confirmation on." The telescope beam was slewed back in the direction of 4079, checking to see if the suspicious radio tone would come back. By now, the silent drama unfolding on the computer screens had my full attention. The center display was slowly being painted with a sea of radio noise. Immediately, a faint, narrow line became conspicuous, wending its way across the graphic, and drifting determinedly to higher frequencies. This is precisely the sort of signal we expect from the extraterrestrials.
Jill and I stood out of our chairs, watching the thin white line. Its drift rate was high, suggesting that the transmitter responsible was either on a very rapidly rotating planet, or more prosaically on a rapidly orbiting satellite. The rate of drift was also changing, introducing a strong curvature into the line now being traced on the screen. After four minutes, the Phoenix system said, "yes, I see this signal in the on position," and promptly scheduled another "off" scan.
This was the crucial test. If the signal so obvious to us now was also visible in the "off" position, then it was just another bit of annoying interference. If not, then there was a real chance we had found neighbors 21 light-years from Puerto Rico. Had Jill and I stared any harder at that display screen, we would have bored holes in the phosphor.
The signal was still there. No aliens. Despite being clearly visible to our eyes, the heavy curvature of this signal meant that the detection software would occasionally miss it. Indeed, it had done exactly that during the first "off" scan. Such emissions were a challenge for the signal detection team, but I wasn't thinking of them. I was thinking about being on the prow of a ship of discovery. Squinting at the horizon, I thought I saw the first indistinct outlines of a new coast. But it was only a mirage. This time.
Sept. 23
The order came on Sunday morning. The observatory was shutting down to prepare for the hurricane. We too, had to button-up and tie down our gear to protect it from the expected wind and rain.
We've been running our equipment with a rented diesel generator. It is a temporary fix until we get a new motor-generator set to provide uninterrupted power. Temporary installations don't fare well in a hurricane. With the help of the observatory staff, we lashed down the fuel tank and secured the temporary power cables from the generator to the mobile research facility (MRF) that contains the signal processing equipment. The MRF itself is heavy and snugly positioned near the control building, but it too needed some protective measures. Before the power was cut off, we backed-up all computers and shut them down in an orderly fashion. Once the power was shut down, we covered the openings in the MRF air conditioner. The fiber optic cables that connect the MRF electronics and computers with the rest of the system are somewhat fragile. The canvas shroud that protects them from normal weather conditions was not designed for a hurricane. The cables were disconnected and pulled back into a conduit. We then installed a plywood box over the conduit.
Then it was time to either get out or wait it out. Two Phoenix team members elected to stay at the observatory. Others headed back to California. This was actually just a day in advance of a planned break in the observations, so the hurricane canceled only one day of observing (so far). The observing team for the second half of the session was scheduled to fly on Tuesday, the 22nd. Those plans are, excuse the expression, up in the air.
We have just heard from Bud Hill at the observatory. The eye of the hurricane passed very close to the observatory. As of this writing, power is still out on most of the island. The observatory is running off its own diesel generator. It is still unknown whether the telescope sustained any significant damage. Some of the flooring panels are missing from the catwalk, so no one has inspected the feed platform yet. Since the platform is about 150 meters (450 feet) above the dish, caution is prudent.
Project Phoenix was scheduled to resume observing on the evening of the 25th. However, we do not know how long it will take for the observatory to recover from this terrible storm.
Sept. 28
We received news from Arecibo that the control arm for the Gregorian tertiary reflector has been damaged and that repair work will extend into next week. Since our observing time is scheduled to end Tuesday morning, we are canceling the remainder of the run.
The new Gregorian reflector system is a set of specially shaped radio mirrors that correct for the spherical shape of the 305 meter dish and cause the radio waves to be focussed to a point. The tertiary mirror must be positioned very accurately in order to focus all of the radio waves collected by the dish.
Our next observing session begins March 1999, so there is much to be done to prepare the system for the hiatus. We will run tests to characterize the state of the system (it hasn't been turned on since the hurricane). Spare computers and equipment must be packed away to make room for other observers. Some computers and test equipment will be sent back to the Institute.