Berkeley – June 10, 1998 – SETI researchers at California's Berkeley University have completed the most sensitive sky survey ever conducted in search of intelligent signals from outer space. The survey, called SERENDIP III, employed a detector mounted on the world's largest radio telescope, the 1,000-foot dish at Arecibo, Puerto Rico. The instrument analyzed 500 trillion signals in the last six years and recorded information on three billion of them.
"At our level of sensitivity, there was nothing we could uniquely
identify as an extraterrestrial signal," said project leader
Stuart Bowyer, a professor in the graduate school at UC Berkeley
and an astronomer at the campus's Space Sciences Laboratory.
Nevertheless, the SERENDIP (Search for Extraterrestrial Radio
Emissions from Nearby Developed Intelligent Populations) team
already has embarked on a new generation search using an improved
instrument mounted a year ago on the Arecibo radio telescope.
"Our negative results don't rule out the possibility of
civilizations out there because we are still only covering a
small part of the radio spectrum," said Dan Werthimer,
co-director of SERENDIP. "We are continually getting better.
Since we started the project 20 years ago, our ability to survey
the sky has grown by a factor of a million. Our newest
instrument, SERENDIP IV, will give us 40 times more coverage than
SERENDIP III."
Sabine Airieau, a junior member of the SERENDIP team who
graduated from UC Berkeley last year, presented a status report
on SERENDIP III at the June 7-11 meeting of the American
Astronomical Society in San Diego, Calif.
During their sky survey, the team also looked for signals from
six recently discovered extrasolar planets: 51 Pegasi, 70
Virginis, 55 Cancri, Tau Bootes, HD114762 and Rho Corona
Borealis. No signals were detected.
SERENDIP is one of the world's longest running searches for
extraterrestrial intelligence, known as SETI projects. SERENDIP
III, which collected data from 1992 until this year, employed a
third-generation instrument piggybacking on the large radio dish
at Arecibo.
The SERENDIP III instrument scanned about a third of the sky
every six months, looking in a radio band centered around a
wavelength of 70 centimeters — a radio region typically used for
communications, and which includes UHF and mobile phone channels.
A fourth-generation instrument, SERENDIP IV, was installed on the
Arecibo telescope in May of 1997, designed to scan the same
region of the sky but in a frequency band centered on a
wavelength of 21 centimeters. That wavelength is considered by
many the most likely at which a civilization would broadcast its
presence.
When a new receiver comes on line at Arecibo later this year, the
SERENDIP IV instrument should be able to analyze 40 times more
signals than SERENDIP III.
The search is conducted by looking for repeating signals. Thus,
the more often they look at a given area of sky, the greater the
chance of detecting an extraterrestrial signal — if there is one.
With specially designed computer circuitry and software, SERENDIP
IV will simultaneously examine 168 million frequency channels
every 1.7 seconds. The 168 million signals are analyzed
immediately for radio intensities above background levels. Those
found are immediately transmitted to UC Berkeley, where they are
analyzed to eliminate the ones caused by interference from
Earth-based or near-space radio sources.
"Ninety-nine percent of recorded signals are rejected at this
point," said SERENDIP software director Jeff Cobb. "Those that
remain will be studied closely for patterns consistent with an
artificial signal from space."
"When and if we find something that is compelling, we will call
up the telescope director and ask for time to take a longer look
at that area of the sky," Werthimer said.
Despite piggybacking on the world's most sensitive radio
telescope, he said, the instrument could not detect random radio
noise emanating from a civilization like ours, which has been
leaking radio and TV signals for less than 100 years. For
SERENDIP and most other SETI projects to detect a signal from an
extraterrestrial civilization, the civilization would have to be
beaming a powerful signal directly at us.
"With available instruments we are unlikely to detect Earthlike
planets or civilizations," Airieau said. "This sort of detection
will not come within our realm for another few decades."
Werthimer added, "The first civilization Earthlings detect is
likely to be more advanced than ours — perhaps 10,000 to billions
of years old."
SERENDIP was started in 1978 by Bowyer and astronomer Michael
Lampton on a UC Berkeley radio telescope located in Hat Creek,
Calif. SERENDIP II followed with two years of observations
(1986-88) at the National Radio Astronomy Observatory in Green
Bank, W. Va., using a 300-foot telescope that collapsed several
years ago. SERENDIP III was mounted at the Arecibo Observatory in
1992.
SERENDIP is supported by the Planetary Society and the SETI
Institute of Mountain View, Calif., with major donations from
numerous companies and from the Friends of SERENDIP, a group led
by novelist Arthur C. Clarke.
