By Greg Taylor of The Daily Grail
Another program, 'Project SERENDIP', has got around some of the problems faced by Project PHOENIX by 'piggybacking' an extra receiver onto an existing radio telescope. This shared search is therefore capable of, in theory at least, running continuously, although it cannot control where it is aimed (due to it being the secondary user). Project SERENDIP is thus a sky survey that listens to 168 million channels, each 0.6 hertz wide, in a 100-megahertz band focused on the magic frequency of 1.42 gigahertz (MacRobert & LePage 1999). The weakness in the SERENDIP program is that there is no real-time follow up; that is, if a signal is found the telescope cannot be directed back to the point immediately to check whether it is genuine, it must be done elsewhere later. One problem that SERENDIP has addressed ingeniously however, is how to process huge volumes of data on narrow-band signals - by using the power of distributed computing.
As technology advanced, SETI projects were able to scan growing numbers of channels through the use of MCSA's (Multi-channel spectrum analysers (Cullers et al 1985, p. 39)): compare Project Ozma's single channel versus Project Phoenix's two billion. The problem soon became not that enough channels were available, but that there wasn't enough computer processing power to analyse each channel for a genuine signal. This problem has been solved in part recently by the SETI@home program, which utilises the power of distributed computing. Volunteers download a program for their home computer which installs itself as the default screensaver. While the computer is not being used the program processes a 'work unit' of SETI information; once done, it uploads it to the SETI@home site and downloads a new work unit. Each work unit represents 107 seconds of listening time and only 10 kilohertz of bandwidth: every 256 work units covers SETI@home's 2.5 megahertz search band (centred once again on the magic frequency of 1.42 gigahertz) for this time period (MacRobert & LePage 1999). As every 107 seconds represents a strip of sky 0.1 by 0.3 degrees in area, it is obvious that a lot of volunteers are necessary. Fortunately for SETI@home, they have had at least over four hundred thousand volunteers in their program (MacRobert & LePage 1999).
There are a number of other programs running as well, though not on the scale of SERENDIP, SETI@home and Project Phoenix, such as META (Million-channel Extra-Terrestrial Assay), META II and BETA (Billion-channel Extra-Terrestrial Assay). There is also amateur participation, such as Project BAMBI (Bob and Mike's Big Investment) and Project Argus, a coordinated effort organised by the SETI League. The most revolutionary programs at the moment, however, are probably the various Optical SETI projects. COSETI (Columbus Optical SETI) is conducting a targeted search of hundreds of stars for both narrowband laser signals as well as pulsed signals at visible wavelengths (MacRobert & LePage 1999). The COSETI Observatory has continually argued against the proposition that optical SETI is scientifically illogical (Kingsley 1999). The Director of COSETI, Stuart Kingsley, states on his website his belief that laser transmitters are the superior form of interstellar communication. This view is gradually gaining acceptance - other Optical SETI programs are being carried out at the University of California and also at Harvard University.
Nevertheless, orthodox SETI continues with the 'sequel' to Project PHOENIX. The SETI Institute, working with funds donated by Microsoft co-founder Paul Allen, is constructing their very own radio instrument, the Allen Telescope Array (ATA). The ATA can be used 24 hours a day for simultaneous observations by radio astronomers and SETI researchers. The technique used by the ATA is novel: hundreds of "satellite" dishes will be wired together to form an instrument that's the equivalent of a single, massive, 100 meter-wide radio telescope.
Despite the many approaches currently being undertaken in SETI, and the optimism of those involved, there remain many problems in this area of research. One of the largest, and not at all scientific, is the problem of funding. The 'giggle factor' inherent in SETI discussion remains a difficulty for those pursuing government funding, with politicians deeming it trivial and unworthy (SETI Faces Uncertainty on Earth and in the Stars 1992). All programs at the moment are funded either by educational institutions or through donations. The success of SETI@home argues that the public is interested in supporting searches however, so perhaps this situation will change (indeed, Paul Allen's recent involvement may be a watershed). The lack of funding contributes to another problem: budget-oriented shared programs lack real-time follow up on promising signals. Without this feature we may always be left wondering whether a signal that cannot be re-acquired was a missed chance of detecting an extraterrestrial signal. Also, the growth of interference from Earthly technologies makes the job of listening in more difficult each year. For microwave searches, a major problem also lies in the 'cosmic haystack' feel (Billingham and Tarter 1993, p. 255) which is inherent in scanning narrow-band signals within a very wide total bandwidth. This problem may be alleviated as search technology advances and computing power increases though.
Finally, some problems are always going to be inherent in any attempt we make to communicate over long distances. If we detect a signal from a source 1000 light years away, by the time of receiving it the civilisation from which it originated may no longer exist. Communication therefore, will probably not be between individuals, but between civilisations. And perhaps we are wrong with our assumptions: we have selected certain forms of communication and certain frequencies as ideal, whereas advanced civilisations elsewhere may use technology outside of our sphere of thinking. Alternative writer Terence McKenna once pointed out this anthropocentric problem
To search expectantly for a radio signal from an extraterrestrial source is probably as culture bound a presumption as to search the galaxy for a good Italian restaurant.
In response though, SETI enthusiasts may quote pioneers Cocconi and Morrison (1959), who said at the very beginnings of SETI:
The probability of success is difficult to estimate; but if we never search, the chance of success is zero.
In the past forty years, the search for extraterrestrial intelligence has taken great leaps forward in both theory and practice. Drake's Equation has become a standard method of working out the number of communicating civilisations (although still debated hotly), and perhaps more importantly, has lent a legitimacy to the SETI effort as a scientific process. Considering methods of communication which might be employed by an extraterrestrial civilisation has led to interesting theoretical discussions of technologies which may be employed. On the practical side, evidence of improvement is obvious when comparing the capabilities of Project Ozma and Project Phoenix (Project Phoenix matched Project Ozma in a fraction of a second of operation). At the rate technology is changing, we soon may be able to achieve truly comprehensive searches of the microwave spectrum. Also, new developments such as Optical SETI and SETI@home offer new and exciting ideas to the search. Many problems still face SETI programs, but strong organisation and a desire to succeed may be enough to ensure their survival. The only question remaining, perhaps truly the only question, is whether anybody is out there.