History of SETI
Early efforts to detect signals of extraterrestrial intelligence focused on searching for signals from Mars. Nikola Tesla attempted to detect radio signals from Mars in 1899,[1] and the United States made a similiar effort during an opposition of Mars in 1924, going so far as to declare a "National Radio Silence Day" and assign a cryptographer to translate any potential Martian messages[2][3].
In 1960, Frank Drake performed the first modern SETI experiment, named "Project Ozma", using a radio telescope 26 meters in diameter at Green Bank to examine the stars Tau Ceti and Epsilon Eridani. [4]
From 1973-1995, the Ohio State University Radio Observatory used its telescope, the "Big Ear", to search for extraterrestrial radio signals under the Ohio State University SETI program. The program gained fame on August 15, 1977, when Jerry Ehman, a project volunteer, witnessed a startlingly strong signal received by the telescope. He quickly circled the indication on a printout and scribbled the exclamation "Wow!" in the margin. Dubbed the Wow! signal, it is considered by some[who?] to be the best candidate for a radio signal from an artificial, extraterrestrial source ever discovered, but it has not been detected again in several additional searches.[5]
Credit: The Ohio State University Radio Observatory and the North American AstroPhysical Observatory (NAAPO).
In the early 1980s, digital spectrum analyzers begun to be used to search for SETI transmissions. Harvard University physicist Paul Horowitz took the next step and proposed the design of a Spectrum_analyzer specifically intended to search for SETI transmissions. The first generation of this technology was a portable spectrum analyzer named "Suitcase SETI" that had a capacity of 131,000 narrow band channels, which began operations in 1983 using the 26-meter (85 ft) Harvard/Smithsonian radio telescope at Oak Ridge Observatory in Harvard, Massachusetts. Suitcase SETI was followed in 1985 by Project "META", for "Megachannel Extra-Terrestrial Assay", which was capable of analyzing 8.4 million channels. This was followed by META II in Argentina in 1990, to search the southern sky. META II is still in operation, after an equipment upgrade in 1996. META was followed in 1995 by "BETA", for "Billion-channel Extraterrestrial Assay", which was capable of analyzing 250 million channels. BETA ceased operations in 1999 when telescope it was using was blown over by strong winds and seriously damaged.[6]
From 1995 to 2004 Project Phoenix conducted radio observations of 800 stars using the Parkes radio telescope, the Green Bank Telescope and the Arecibo Telescope.