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EP: Fachverband Extraterrestrische Physik

EP 4: Poster Session

EP 4.2: Poster

Tuesday, February 26, 2013, 11:15–12:45, Poster OG

Arecibo message: Fatigue due to diffraction effects ? — •Erhard K. Schweizer — D-97980 Bad Mergentheim, Neunkircher Str. 46

In 1974 the Arecibo message was sent toward M13, 25'000 light years away with a radiated power of 1 MW. Taking diffraction effects into account, the signal from the 305m-Arecibo-antenna is shaped to a conical, modified Bessel lobe showing a cone angle of 0,017°. This minute divergence results in a circular spread of 18.3AU after 1 year of travel. The 1MW starting power is diluted to a power strength of less than 5E-20 W/m*, 1 light year away. Further propagation weakens the signal quadratically with distance, so ET needs sophisticated devices to detect the MW-Arecibo message at all. Acchievable signal strength for our extraterrestrial neighbours are discussed as a function of antenna size, radiated power, frequency and sender-recipient distance.