Detectability Of ETI Pulsed Beacons

9402-001

This (2-dimensional) diagram, first reproduced in the 45th International Astronautical Congress paper presented in Jerusalem, shows the photon count possibilities for both large and small telescopes according to the pulsed beacon rationale by Kingsley.

This diagram illustrates the photon-count for an attention-getting ETI laser pulse of 1 ns duration at a repetition rate of 1 Hz.  It is assumed that the ETI civilization is capable of producing an EIRP = 3.2 x 10³³ W.  The photon-count rates are shown for ranges of 10, 100 and 1,000 light years, with the very modest assumption that the detection efficiency is only 1%.  A star like out Sun appears as a 2nd magnitude object at a range of 10 light years. During each 1ns pulse, the laser outshines the ETI's star by approximately ten million times.  Not only is the detectability of the pulse not affected by the stellar background noise, but light pollution has little effect if a spatial filter is employed to confine the field-of-view to that surrounding the star under observation.

• Jeff Hecht's Laser Focus World article

Copyright (c), 1996