Eavesdropping: The Radio Signature of the Earth
Television leakage from the earth allows detection of our civilization at interstellar distances.
W.T.Sullivan III,
S.Brown,
C.Wetherill
Published in
Science, Vol.199, Num.4327,
p.377, 27 Jan 1978.
Summary.
In addition to searches for purposeful signals, those attempting interstellar
communication should also consider the possibility of eavesdropping on radio
emissions inadvertently "leaking" from other technical civilizations. To
understand better the information which might be derivable from radio leakage,
the case of planet earth is considered. The most detectable and useful escaping
signals arise in a few BMEWS-type radar systems and in normal television
broadcasting. A model including over 2000 television transmitters is used
to demonstrate the wealth of astronomical and cultural information available
from a distant observer's careful monitoring of frequency and intensity
variations in individual video carriers (program material is not
taken to be detectable).
