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Space Topics: Search for Extraterrestrial Intelligence

The Search for Extraterrestrial Intelligence: A Short History

Part 13: SETI after NASA

The cancellation of NASA's SETI program in 1993 was a severe shock to the SETI community. For although HRMS was a very small project by NASA standards, it dwarfed all other SETI efforts combined. As long as NASA was a part of SETI, it was clearly the dominant player, and its demise left a void that was difficult to fill.

NASA, nevertheless, was never the sole sponsor of SETI. In the shadow of HRMS grew a variety of private groups that devoted their resources to SETI, and sometimes joined forces with NASA. When HRMS was unexpectedly cancelled, these groups stepped forward to save what they could and preserve SETI research. Two of these private organizations stand out in particular for their leadership role in preserving SETI in difficult times: The SETI Institute, headquartered in Northern California's Silicon Valley, and The Planetary Society, based in Pasadena.

Jill Tarter SETI Director at the SETI Institute. Credit: The SETI Institute

The SETI Institute was founded in 1984 to sponsor and conduct research on SETI and life in the universe. The Institute included among its founders and sponsors SETI veterans such as Frank Drake of Project Ozma fame, and fellow "Dolphin" Bernard Oliver. But it also included a new generation of investigators such as Jill Tarter and Seth Shostak. Most of the Institute's earlier projects were funded by NASA, and it played a significant role in the targeted search program that was based at NASA Ames in nearby Moffett Field.

When HRMS was cancelled in 1993, the SETI Institute stepped in to save the targeted search, and became its main sponsor. It quickly acquired much of the NASA Ames' SETI equipment, and set about establishing its own privately funded project. In February 1995 it launched Project Phoenix, a highly advanced targeted search based on the defunct NASA program.

For their search, Phoenix scientists compiled a list of 1000 stars that seemed the most likely to be homes of alien civilizations. They are mostly solar-type stars at a distance of no more than 200 light years from Earth and older than 3 billion years, as well as the very closest stars regardless of type. When stars are discovered to have planets, they are also added to the list. Each targeted star can be monitored for signals at any wavelength between 1000 and 3000 MHz. For comparison, the now popular SETI@home monitors a frequency band of only 2.5 megahertz, which is just over one-thousandth of Phoenix's capabilities. Phoenix computers then analyze this enormous bandwidth with razor-thin resolution, and can recognize a signal with a width of only 0.7 Hz. This is crucial for recognizing intelligent signals, because no known naturally occurring signal is less than 300 Hz wide.

The 64 meter dish at the Parkes Observatory in New South Wales, Australia. Credit: CSRIO and Seth Shostak

Project Phoenix is a mobile operation. Its advanced custom-made electronics hardware is packed into a truck trailer, which can pitch camp at any of the major radio observatories around the world. Its first stop was the 64 meter (210 foot) dish at the Parkes Observatory in Australia, and in September 1996 it moved to the National Radio Astronomy Observatory in Green Bank, West Virginia. There it shared time for a year and a half on the 43 meter (140 foot) dish, only a short distance from the 85 foot dish used by Frank Drake in the pioneering Project Ozma. Since 1998 Project Phoenix has been camped at Arecibo in Puerto Rico, where it makes use of the 305 meter (1000 foot) radio telescope, the largest in the world.

As a targeted search, Phoenix can monitor particular stars with remarkable precision and breadth, unmatched by other searches. Working at "real time" with other observatories around the world, it can offer almost immediate verification of any signal it may detect. This is important both because it helps eliminate the possibility of Earthly interference, and because signals from deep space can disappear quickly due to interstellar scintillation. Its main limitation is that is has to share observing time with other radio-astronomy projects at the major radio observatories. At Arecibo, for example, it can only run 20 observing sessions of 12 hours each every six months, meaning that it is "on the air only a fraction of the time. Nevertheless, after almost seven years of operation, Project Phoenix is going strong, and gearing up for a receiver upgrade sometime in 2002.
 
Whereas the SETI Institute continued the HRMS targeted search, The Planetary Society took a different approach to SETI in the post-NASA years. Even before the cancellation of HRMS, The Planetary Society had shown a marked preference for "all sky surveys" in preference to targeted searches. This approach reflected the views of Bruce Murray, the future president of The Planetary Society, who consistently argued that we should not make any assumption about the nature of an alien civilization, and that we should therefore not limit our search to stars that appear hospitable to our human sensibilities. As director of the Jet Propulsion Laboratory from 1976 to 1982 Murray was largely responsible for establishing the "all sky survey" element of NASA's SETI project at JPL.

The Planetary Society, unlike the SETI Institute that concentrated its efforts on one highly sophisticated search, spread its resources among various groups trying out different techniques. Since the early 1980s the Society had been supporting several SETI ventures led by Paul Horowitz of Harvard University. In October of 1995, with Planetary Society funding, Horowitz launched Project BETA - an all-sky radio survey at the "water hole" frequency range. BETA, or the Billion-channel Extra-Terrestrial Assay, is based at the Harvard-Smithsonian Observatory in the town of Harvard, Massachusetts, where it makes use of the 26 meter (85 foot) radio telescope. BETA had completed several surveys of the skies visible from Harvard when the dish was damaged in a storm in March of 1999. With help from The Planetary Society, repairs are under way.

Since 1996 The Planetary Society has also been supporting Project SERENDIP, a radio all-sky survey led by Dan Werthimer of U.C. Berkeley. Like Project Phoenix, the SERENDIP receiver is based at the Arecibo Observatory, but unlike Phoenix it doesn't need to wait for highly-prized observation time-slots. Instead, it is permanently perched above the Arecibo dish, scanning whichever part of the sky the dish happens to be pointed at and moving through the sky with the rotation of the Earth. While this approach would not work for a targeted search, it is well suited for an all-sky survey like SERENDIP.

Optical SETI Observatory The new Planetary Society-sponsored Optical SETI observatory in Harvard, Massachusetts. Credit: Paul Horowitz, The Planetary Society

An offshoot of SERENDIP is the wildly successful SETI@home project - the distributed computing venture that sends radio data packets to millions of users around the world. These then use their own personal computers to analyze the data for an alien signal. When SETI@home founders were looking for a sponsor in 1998, The Planetary Society stepped in and provided the needed seed money. The Society has remained the main sponsor for the project ever since. SETI@home uses the data collected by the SERENDIP receiver, but focuses on a narrower bandwidth, centered on the 1420 KHz hydrogen line. With over three million personal computers at its disposal, SETI@home can analyze its data at a depth and detail impossible in more conventional approaches. Like SERENDIP the project is based at U.C. Berkeley and is led by project director David Anderson and chief scientist Dan Werthimer.

The Planetary Society has also branched out beyond radio searches, sponsoring Optical SETI ventures that look for concentrated laser signals from the stars. In 1998 it began supporting two targeted searches, based in Harvard and U.C. Berkeley, which look for very short light bursts coming from candidate stars. Since the end of 2000 The Society has supplemented these projects by funding the construction of the largest dedicated Optical SETI observatory in the world, in Harvard, Massachusetts. When completed ometime in 2002, the observatory will be used for the first all-sky Optical SETI survey.

--Amir Alexander

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