DRAKE
EQUATION N = R * x f p x n e x f l x f i
x f c x L The terms in the equation can be explained as follows o N -
Number of communicative civilizations o R* - Average rate of formation of
stars over the lifetime of the galaxy (10 to 40 per year) o fp - Fraction
of those stars with planets (0 < fp <1, estimated at 0.5 or 50 percent)
o ne - Average number of earth-type planets per planetary system (0 <
ne <1, estimated at 0.5 or 50 percent) o fl - Fraction of those planets
where life develops (0 < fl <1, estimated at 1 or 100 percent) o fi
- Fraction of life that develops intelligence (0 < fi <1, estimated at 0.1
or 10 percent) o fc - Fraction of planets where intelligent life develops
technology such as radio (0 < fc <1, estimated at 0.1or 10 percent)
o L - Lifetime of the communicative civilization in years (estimates are highly
variable, from 100s to 1000s of years, approximately 500 years for example purposes)
BASIC PROBLEMS IN SEARCH
"
How to search such a large area of sky " Where to look on the radio dial
for ET " How to make the best use of the limited radio-telescope resources
available for SETI
Large vs. Small
Areas of Sky Wide-field search - In this method large chunks of the sky
are searched at a low resolution within a short period of time. Targeted
search - In this method, intensive investigations of a limited number of sun-like
stars are made for ET signals. What's the Frequency? In the 1- to 10-gigahertz
(GHz) range of frequencies, there are two frequencies: 1.42 GHz, caused by hydrogen
atoms, and 1.65 GHz, caused by hydroxyl ions. This area is called as the water
hole.
Limited Radio-telescope Resources
" Conduct limited observing runs on existing radio telescopes "
Conduct SETI analyses of radio data acquired by other radio astronomers (piggyback
or parasite searches) " Build new radio telescopes that are entirely
dedicated to SETI research