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Detectability of Extraterrestrial Technological Activities


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Author Topic: Detectability of Extraterrestrial Technological Activities  (Read 706 times)
Jennifer Murdoch
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« Reply #15 on: February 04, 2010, 01:22:50 pm »

       and the distance  to  the  inhabited  planet  (R),  in order to have
       enough time to avoid the collision.

       One of the  most  important  issues   for   the   success   of  SETI
       observations on Earth is the ability of an observer to detect an ETC
       signal.  This factor is proportional to the received  spectral  flux
       density of the radiation.  That is, the power per unit area per unit
       frequency interval.  The  flux  density  will be proportional to the
       EIRP divided by the spectral bandwidth  of  the  transmitting  radar
       signals B.

       The EIRP is  defined  as  the product of the transmitted  power  and
       directive antenna gain  in  the  direction of the receiver as EIRP =
       PT.G, where PT is the transmitting  power  and  G  the antenna gain.
       This quantity has units of [W/Hz].

       According to the kind of object that the ETC wants to detect (nearby
       planetoids, comets, spacecraft, etc.), the distance  from  the radar
       system and the  selected  wavelength,  a  galactic civilization that
       wants to finish a full-sky survey  in only one year, will arise from
       a modest "Type 0" (w10exp13 W/Hz, Rw0.4 A.U., Dw5000 m, and lambdaw1
       m) to the  transition  from "Type I" to "Type II" (w2x10exp24  W/Hz,
       Rw0.4 A.U., Dw10 m, lambdaw1 mm).
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