168 lines
8.6 KiB
Plaintext
168 lines
8.6 KiB
Plaintext
SUBJECT: THE SEARCH FOR EXTRATERRESTRIAL INTELLIGENCE FILE: UFO39
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(S E T I)
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Our Milky Way Galaxy is only one of 10 billion galaxies in the
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presently observable universe. Our Sun is just one of some 300
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billion stars in our galaxy alone. Astronomers have confirmed that
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the Sun and the galaxy, which make our existence possible, are not
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unusual or basically different from other galaxies and stars.
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A few generations ago, astronomers believed that planetary systems
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were extremely rare--that our solar system and our Earth with its
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life-supporting environment might well be unique. Chemists and
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biologists knew little if anything about the processes that led to
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the origin of life. In the last fifteen years, however, a number
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of important discoveries have strongly suggested that there is a
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fundamental relationship between the origin and evolution of life
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and the origin and evolution of the universe.
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Advances in astronomy and physics have given renewed support to the
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concept that planets are not rare exceptions, but are a natural
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part of the star formation process and may number in the hundreds
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of millions in our galaxy alone. [In December 1984, the National
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Science Foundation announced that a team of Arizona astronomers had
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detected a possible solar system around Beta Pictoris, a star 53
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light years from Earth.] Recent biological experiments applying
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natural energy sources to molecules have produced some of the
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organic building blocks that make up the chemistry of life. Radio
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astronomers have discovered that many organic molecules exist even
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in the depths of interstellar space. Elements identified in these
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molecules include hydrogen, nitrogen, oxygen, carbon, silicon, and
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phosphorus. Earth has been without life only a small fraction of
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its age, which leads many scientists to look upon the formation of
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life on other suitable planets as very likely. Once begun, and
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given billions of years of relative stability, life may achieve
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intelligence and, in some cases, may evolve into a technological
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civilization.
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One direct way of testing whether intelligent life exists beyond
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our solar system is to search for an artificially generated radio
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signal coming from interstellar space. As an example, ultrahigh
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frequency and microwave radio signals emanating from Earth are
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expanding into space at the speed of light. This radio, radar, and
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television "leakage" of ours currently fills a sphere nearly 100
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light-years in diameter. The same phenomenon would serve to
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announce the presence of other intelligent life. Moreover, advanced
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civilizations might be operating radio beacons, possibly to attract
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the attention of emerging societies and bring them into contact
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with a community of long-established intelligent societies existing
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throughout the galaxy.
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Either type of signal (leakage or beacon) would be easiest to
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detect at frequencies where the background radio noise is minimal.
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One of the quietest regions of the electromagnetic spectrum is the
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"microwave window" that lies in the frequency band between 1000 and
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10,000 megahertz (MHz). It is reasonable to assume that others
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wishing to establish interstellar contact by radio might choose
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this band.
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The search for extraterrestrial intelligence (SETI) is not new,
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having first been proposed by U.S. scientists in 1959. Since that
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time, numerous scientific and technical studies have been made on
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an international scale, and more than 30 radio searches have been
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attempted, covering only a minute area of search space. What is new
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today is the available technology. Radio telescopes on Earth are
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sufficiently sensitive to detect signals no stronger than some
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leaving Earth at distances of a thousand light-years or more. The
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305 meter (1000-ft) diameter radio telescope at Arecibo, Puerto
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Rico, could detect transmissions from nearby stars that are less
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powerful but similar to our own television and radars. Advances in
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computers and data processing techniques now make it possible to
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search automatically through millions of incoming radio signals
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each second and, if it is present, to identify a signal transmitted
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by an intelligent society.
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The NASA SETI Program is nearing the end of a 5-year research and
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development phase, using existing radio telescopes and advanced
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electronic techniques to develop prototype SETI instrumentation.
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The program is being jointly carried out by the Jet Propulsion
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Laboratory (JPL) at Pasadena, California, and the NASA Ames
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Research Center at Moffet Field, California. Leading radio
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scientists from the national laboratories and academic community
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have also joined together in the SETI Science Working Group to
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assist the JPL-Ames team in developing the instrumentation and the
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search strategy.
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The proposed plan involves two complementary search modes that are
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designed to cover a range of possibilities. One mode is an all-sky
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survey that will search the entire celestial sphere over a wide
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frequency range (1200 to 10,000 MHz plus spot bands up to 25,000
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MHz) to cover the possibility that there may be a few civilizations
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transmitting strong signals, possibly as interstellar beacons.
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Longer observing times may be allocated to directions that include
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a large number of stars, especially the galactic plane. The radio
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telescopes employed will be the 34-meter (112-ft) diameter antennas
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that are part of NASA's Deep Space Network. The survey will be
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conducted by moving the telescope across the sky at a constant
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rate. It will cover at least 10,000 times more frequency space than
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all previous survey attempts, will be about 300 times more
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sensitive, and will take about 5 years to complete.
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The second mode is a high-sensitivity targeted search that will
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look for weak signals originating near solar-type stars within 80
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light-years distance from Earth. The objective is to examine the
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possibility that nearby civilizations may have radio transmitters
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no more powerful than our own. Some stellar clusters and nearby
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galaxies will also be observed. The frequency range covered will
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be 1200 to 3000 MHz plus spot bands between 3000 and 10,000 MHz.
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To achieve very high sensitivity, the targeted search will use some
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of the largest radio telescopes available, including the 305-meter
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(1000-ft) diameter antenna at Arecibo, Puerto Rico, and the Deep
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Space Network's 64-meter (210-ft) diameter antennas. The number of
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targets covered will be much larger than previous searches and the
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range of frequencies covered will be thousands of times greater.
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The targeted search is expected to take about 3 years to complete.
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Current astrophysical knowledge and the available technology make
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the SETI observing program both timely and feasible. Timeliness
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also relates to the rapidly-increasing sources of radio frequency
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interference (RFI) in the microwave band. Portions of the microwave
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spectrum that directly concern SETI ar subject to allocation to
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numerous users worldwide, emphasizing the need to proceed with SETI
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while it remains economically possible with our current technology.
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If the use of the microwave spectrum continues to increase at its
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present rate, the greatest exploration opportunity in the history
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of mankind may be placed economically and technologically beyond
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our reach for the foreseeable future.
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S E T I SEARCH SUMMARY
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_________________________________________________________________
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SEARCH PARTICULARS SKY SURVEY TARGET SEARCH
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_________________________________________________________________
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Area Coverage All directions 1000 stars,
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regions
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Signal search Continuous Wave Pulses, drifting
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CW
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Frequency coverage 1200-10,000 MHz + 1200-3000 MHz +
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spot
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spot bands bands
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Frequency resolution 1000, 32 Hz 1000, 32, 1 Hz
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Receiver bandwidth Wide (~250 MHz) Narrow (~10 MHz)
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Observing time per
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direction at each 0.3 - 3 sec 100-1000 sec
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frequency setting
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Channels analyzed ~10 million ~10 million
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per second
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Antenna diameter 34 meters 305 and 64 meters
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Search duration ~5 years ~3 years
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_________________________________________________________________
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SETI, THE SEARCH FOR EXTRATERRESTRIAL INTELLIGENCE, NASA/JPL
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400-265, 9/85
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**********************************************
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* THE U.F.O. BBS - http://www.ufobbs.com/ufo *
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********************************************** |