THE first concerted exploration of the cosmos for signs of aliens begins in Australia today. In preparation, a team of American astronomers took over the largest radio telescope in the Southern Hemisphere on January 23, and the first star to be the subject of study has just been settled. For humankind the outcome could potentially be momentous or a monumental flop. For Jill Tarter, this week marks the start of a long-delayed quest which has motivated her research for 20 years since she was a post-doctoral student - the search for extra-terrestrial intelligence (or SETI). This is no amateur probe into the universe by a bunch of space freaks. The 64-metre (210 ft) radio telescope at Parkes in New South Wales, 300 km (186 miles) west of Sydney, has now been handed over by Australia's national research agency, CSIRO, to Dr Tarter's team of scientists and engineers for their exclusive use in the next five months. Project Phoenix will begin at precisely 11am today as the giant dish wheels across the sky and locks on to signals from nu Phoenicis, a star in the constellation Phoenix. Systematic studies will follow another 211 stars only visible from the Southern Hemisphere. The enthusiastic Dr Tarter is undeterred by the possibility of failure. She justified the multi-million dollar quest: 'Personally, I find it the most important question we have to seek an answer to through astronomy. It affects everyone on Earth.' Getting to take-off point for the project hasn't been easy for the SETI Institute based in Silicon Valley, California. Nearly three years ago, Dr Tarter surveyed Parkes for its suitability as the site for the Southern Hemisphere leg of the project. It turned out to be one of the most 'radio quiet' places on Earth and, conveniently for the Americans, the Institute was being publicly funded with US$10 million (HK$78 million) annually through the American space agency, NASA. The project had just started its first search of stars in the Northern Hemisphere when the US Congress slashed NASA's funding and specified no continuance of support for SETI. The bottom nearly dropped out of Project Phoenix, as the Institute was forced to abandon it just after it had begun listening from the radiotelescope in Arecibo, Puerto Rico. It was saved from collapse by the Institute appealing successfully for private funds to take over the custom-built equipment and support a re-start of the search from Parkes. Many individuals have given small amounts, including science fiction writer Arthur C. Clarke. The bulk of the US$7.3 million raised so far has come from co-founders of successful computer companies in Silicon Valley where the SETI Institute is based. The project almost foundered again when the 1,000-tonne structure ground to a halt in November as metal started to shear off a vital roller bearing. Facing a six-month delay for making a new bearing from scratch, there was a frantic search around the world for a replacement. A successful repair was completed just before Christmas and Project Phoenix was delayed for only a fortnight. A 10-tonne container-load of equipment, the Mobile Research Facility known as MURF, arrived by sea earlier this month and has been integrated into the existing systems at Parkes. Until the end of June, Dr Tarter and her 20-strong team, supported by an equal number of Australians, will focus the football-field-sized dish, night and day, on the 212 'candidate' stars, one after another. These stars have been selected for the search from Parkes as they can be seen only from the Southern Hemisphere and are roughly the same age and temperature of the sun, giving the best chance of some having planetary systems. SETI astronomer, Dr Seth Shostak, said nu Phoenicis is slightly hotter than the Sun and lies 50 light years from Earth. He explained the search strategy: 'The search will include the star nearest to Earth, the triple alpha centauri (4.5 light years away) and other stars out to 150 light years away in our own galaxy (the Milky Way) which are old enough to have cooled to the Sun's temperature. 'We'll have a look at the centre of the galaxy, roughly 25,000 light years away, in case an advanced civilisation has placed a radio beacon there. We may also take a look at tau Ceti, one of two stars first studied by Frank Drake from the US for extraterrestrial life, unsuccessfully, in 1960.' Project Phoenix is looking for signs of highly intelligent civilisations which, in times past, have developed technologies akin to, or in advance of, our own. This would be evidenced by precisely controlled radio signals which stand out from the more random, natural radiation of parent stars. All the 'ifs' and 'coulds' about the existence of other intelligent life in space will remain the realm of conjecture until evidence is obtained which stands up to stringent scrutiny. This is why the scientists are being extra-careful in how they collect the billions of signals which naturally will arrive at Parkes. To start with, each star will be studied for half a day in two billion different frequencies. (For the technically minded, the system will automatically sample 29 million channels at a time, scanning from 1 to 3 Gigahertz, a range chosen as there is little interference from events in the cosmic background.) Interference from local, earth-bound transmissions is a much more serious problem. Dr Tarter said powerful computers have been programmed to eliminate the electronic garbage caused by cellular telephones, satellite transmissions and remote controllers for car locks and garage doors. Each day, Australian team leader Dr Kelvin Wellington expects about 12 signals might get past these electronic 'gate-keepers' and will stand out, because of very precise frequencies, as 'candidates' worthy of further study. Then, a system known as FUDDs (Follow Up Detection Devices) will be brought into play, using a second, smaller radio telescope at Mopra, 200 km north of Parkes. This is the project's secret weapon against astronomers being fooled into believing that a signal has come from a distant civilisation when, in fact, it originated from something mundane, like the local radio station. Because the two dishes are so far apart, any Earth-originated interference received at one can be cancelled out by the other. If, after passing checks from both dishes, a signal still stands out as 'promising', a bell will ring and display screens flash at the nerve centre at Parkes. Then, the adrenalin in the nerve centre will really flow as observers stop the automated scanning and focus entirely on making detailed measurements of the signal from the star in question. Although Dr Wellington acknowledges the team will be under immense pressure from the media to make announcements, scientific caution will temper the temptation to go public prematurely. 'We shall have to call on telescopes in other countries to verify our findings independently,' he said. 'But, since there are few radio dishes elsewhere in the Southern Hemisphere where the stars we are studying can only be seen, getting confirmation may take some time. We may need to ask NASA if they can use their satellite tracking dish at Tidbinbilla near Canberra.' Other astronomers will be told first of a positive discovery. If confirmed, the Secretary-General of the United Nations will be notified for announcement to the world. Dr Pockley writes on science from Sydney.