Contents
Use of Signals in Seti
by
Jagabathula Srikanth(02007005)
Salim Dewani (02007004)
Abstract:
The Search for Extra-terrestrial Intelligence (SETI) is an ongoing project directed towards determining the existence of intelligent life beyond our planet. This is done through the detection and analysis of signals from outer space. This document describes the application of signal processing in SETI. The following topics are covered:1. Origin and brief history of SETI.
2. Nature of signals sought by SETI.
3. Detection and Analysis of these signals.
4. Optical SETI project and its comparative advantages.
5. Current status of research and exciting future prospects of SETI.
Motivation:
The ideas of galactic civilizations and alien landscapes have been elegantly built by science fiction writers over the years. The SETI project seeks to investigate these ideas scientifically. The use of simple concepts in signal analysis such as the discrete Fourier transform and the Doppler shift in the search for extra-terrestrial intelligence is a fascinating realworld application of the concepts of the EE210 course.So what is SS technology?
The SETI project can be traced back to 1959 when Cornell physicists Giuseppi Cocconi and Philip Morrison published their findings regarding the potential for using microwave radio to communicate between the stars. Another astronomer, Frank Drake, in the spring of 1960 began a series of experiments which turned out to be the first microwave radio search for signals from other solar systems. He used a single-channel receiver tuned to the magic frequency of the 21 cm (1,420 MHz) line of neutral hydrogen. This came to be known as Project Ozma and it subsequently captured the interest of astronomers worldwide in spite of failing to detect any indicative signals. Thus began an era of Soviet dominated SETI that used antennas to observe large areas of the sky, assuming that some very advanced civilizations might be capable of radiating enormous amounts of transmitter power.In the early 1970's, NASA conducted a comprehensive study for known as Project Cyclops. The Cyclops report provided an analysis of SETI science and technology issues that is the foundation upon which much subsequent work is based. Radio astronomers now conducted searches employing steadily improving technology. Amongst these are the Planetary Society's Project META, the University of California's SERENDIP project, and a longstanding observing program at Ohio State University. In 1989 NASA withdrew its involvement and SETI continued its large-scale programs with private funding.
Why do we believe in Extra terrestrial Life:
Drake's Equation:Frank Drake came up with an equation to estimate the number of communicating civilizations in our Milky Way. The equation is given below: N = R * f(p) * n(e) * f(l) * f(i) * f(c) * L
Here:
1. N = the number of communicating civilizations in our Milky Way galaxy.
2. R = the rate of "suitable" star formation in the galaxy.
3. f(p) = the fraction of stars that have planets.
4. n(e) = the number of these planets around any star within the suitable ecosphere of the star.
5. f(l) = the fraction of suitable planets on which life actually appears.
6. f(i) = the fraction of life bearing planets on which intelligent life emerges.
7. f(c) = the fraction of those planets where intelligent life develops a technology and attempts communication.
8. L = the length of time that an intelligent, communicating civilization lasts.
(An "ecosphere" is a shell surrounding a star within which the conditions suitable for life are observed to exist.) Let us estimate the value of N and see if it is worthwhile to search for extra-terrestrial intelligence. The rate of star formation is about 20 stars per year (R=20). We can safely say that one-half of the stars form planetary systems and the other half form binary star systems (f(p) = 0.5). Since small stars are at lower temperatures, planets capable of life have to revolve very close to the star. Such planets may be locked in position such that one side always faces the star leaving the other side very cold. Also huge stars have a short life and so they have no chance to promote life on their revolving planets. An average sized star like the sun has 2 planets that support life. Lets take n(e)=1. Also we can conservatively estimate f(l)=0.2. Assuming that the development of intelligent life is a part of evolution we can say that f(i) = 1. We see human beings making attempts to communicate with extra-terrestrial intelligence while other moderately intelligent species on earth don't do so. We could once again estimate f(c) to be equal to 0.5.
Substituting the above estimates in the Drake equation yields: N=L
It is indeed interesting to note that the number of intelligent communicating civilizations in the galaxy equals the number of years that such a civilization lasts. Using the fact that humans are successfully using technology over the last 50 years, we may say that L might at least be 50. We thus see that scientific reasoning tells us that there is indeed a strong possibility of the existence of extra-terrestrial life trying to communicate with us.
