comprehensive search ever undertaken. Early work in 1995 involved a five-month observation of the southern sky with the Parkes 210-foot diameter radio telescope in Australia, which focused on 200 Sun-like stars. After the Australian search the Phoenix receiving equipment was stationed at the 1,000-foot diameter Arecibo telescope in Puerto Rico until the end of the decade. The frequency coverage of Phoenix is the quietest part of the microwave window, between 1 and 3 GHz.

NASA’s SETI collapse did not herald the demise of the search: on the contrary, SETI projects are springing up around the world. Harvard University and Ohio State University, which have well-established independent programmes, were joined by others in the Argentine, France, Australia, Italy and India.

One of the current searches is the University of California’s SERENDIP III, which has been ‘piggy-backing’ on the Arecibo telescope in Puerto Rico. The University of California search is using the SERENDIP III spectrum analyser, which examines 4.2 million channels every 1.7 seconds in a 12 MHz-wide band. The Argentinian Institute of Radio Astronomy has two 30-m radio telescopes built to study southern hemisphere galaxies. It has operated a listening programme since 1986. Among the European searches is one led by François Biraud, who has been using the radio telescope at Nancy since 1981, and is monitoring 300 of the closest Sun-like stars. In Italy the Large Northern Cross, at Bologna, is sweeping the sky’s northern hemisphere.

With off-the-shelf equipment the modern SETI amateur can search as much as the professionals did twenty years ago. SETI is rapidly becoming a branch of science that can attract low-budget researchers. Moreover, if amateurs link up they can obtain a much larger field of view. Hence the SETI League, which was founded in 1993 after the withdrawal of US government funds from NASA’s search, originally intended to have over 5,000 amateur searches underway by 2001. This was known as Project Argus, after the giant from Greek mythology who had 100 eyes. On 16 May 1998, a project called SETI at Home was initiated, with an original objective to involve over 100,000 volunteers who would scan data from radio searches with their PCs. SETI at Home captured the public’s imagination, with numerous individuals and schools participating. By the beginning of 2000 over 1 million people were involved with the project, and by May of that year it had attracted over 2 million participants.

Yet these searches can only cover a fraction of the available space. For reasons  of budgetary control the original HRMS was to be conducted below 10GHz (one-tenth of the microwave window) and limited to operations on the surface of the Earth. Because of this restraint on location, a search above the 10GHz limit would be frustrated by considerable background noise from water vapour and molecular oxygen in the Earth’s atmosphere. Until the search can be conducted  from stations located in space the best available is the ground-based portion of the microwave window. But even within these parameters a systematic search of every possible frequency in the 1–10GHz range is impossible. Suppose the channels 1–10 are broken up so that each could be listened to simultaneously.

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The problem is that within the 1–10 window are 9,000 million possible 1Hz-wide channels, 4,500 2Hz-wide channels and 9 million 1KHz-wide channels. With present technology it is impossible to manufacture a spectrometer with 9,000 million channels, although the current goal of SETI research is to produce one with a capacity for 10 million channels. But even this number cannot be adequately searched simultaneously. So current technology is geared to better pattern recognizing software to reduce the scope of the search and computers designed with greater speed and larger memories. Thus efforts towards greater computer speed together with facilities to ‘recognize’ interesting patterns which may be indicative of ETI, will be an important feature of the project. A new generation of super-computers with parallel search and enhanced memory might just take SETI to the starting point.

If an intelligent signal is received, scientific methodology would require its verification and repeated confirmation of it. Previous searches have recorded dozens of unexplained signals but none have been repeatedly observed. The signal must also be independently detectable by other scientists. This is partly because of the need to protect against hoaxes. Once confirmed,  the  SETI protocol requires that, first, another researcher with suitable equipment that can confirm its authenticity is contacted. Second, the International Astronomical Union and the Secretary General of the United Nations must be informed. Third, a press conference is to be called, ensuring that the information is disseminated correctly. Fourth, if the signal can be translated, the protocol warns against an immediate reply: ‘no response to a signal should be sent until appropriate international consultations have taken place’ (Henbest, 1992a: 13). The International Academy of Astronautics in the USA has produced a document entitled the Declaration of Principles Concerning Activities Following the Detection of Extraterrestrial Intelligence, which requires global cooperation in the formulation of a response to a signal or landing.

It is expected that the report of a contact would occupy newspaper headlines for a few days and then be quietly forgotten. Apart from a few sensational newspaper stories – of which there are many already – the full consequences of contact might not be very dramatic in the early stages. There would be excitement among the scientific community in response to the recognition that it was an artificial signal. This would be followed by the major difficulties encountered when trying to interpret it. (We might not even know what they mean by intelligent communication.) During this period we would be shielded from the full culture shock anticipated with the discovery of ETI. Like many great discoveries, knowledge of the existence of ETI may be either initially ignored or misrepresented, but gradually accepted as other beliefs are transformed. Just as it took time to fully accept the existence of virus or black holes, acceptance of ETI is likely to accumulate as bits of evidence emerge together with a gradual shift in beliefs. The long-term effects, however, are considered to be profound. After the first authentic signal many others would follow because once there is success the search will intensify. Optimists would look forward to

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