SP-419 SETI: The Search for Extraterrestrial Intelligence


A portion of the star field taken from the same photographic plate as shown on the cover is reproduced on the right with the addition of designations of stellar type for some of the stars.

[ii-iii] A portion of the star field taken from the same photographic plate as shown on the cover is reproduced on the right with the addition of designations of stellar type for some of the stars. The letter designation (e.g., A) indicates the spectral type of the star. The conventional spectral types are 0, B, A, F, G, K, and M, with O-stars being the hottest (effective surface temperatures in excess of 30,000 K) and M-stars being the coolest (effective surface temperatures of 3,000 to 4,000 K; the effective surface temperature of the Sun is about 5,800 K). The prefix ''g'' indicates that a star is a giant star, a star that has moved away from the main sequence. Stars indicated only with the spectral designation are main sequence stars, deriving their energy primarily from the conversion of hydrogen into helium. The two important aspects of the figure are first that stars like the Sun, spectral type G, are very numerous in the Galaxy, and second, in any typical group of stars, most stars are of spectral types G, K, and M. These types of stars are long lived (10 billion years or greater). The figure shows that viewed from the perspective afforded by interstellar distances, the Sun would be a rather common and ubiquitous type of object. This suggests that the Sun's retinue of planetary companions, and perhaps the intelligent life forms existing on one of these planets, may also be common and ubiquitous phenomena.


[xi] TABLE OF CONTENTS

 

Foreword.
Workshop Members.
Preface, Philip Morrison, Chairman.
 
I. CONSENSUS.
Introduction.
The Impact of SETI.
Conclusions.
1. It is both timely and feasible to begin a serious search for extraterrestrial intelligence.
2. A significant SETI program with substantial potential secondary benefits can be undertaken with only modest resources.
3. Large systems of great capability can be built if needed.
4. SETI is intrinsically an international endeavor in which the United States can take a lead.
 
II. COLLOQUIES.
 
1. Cosmic Evolution.
Ichtiaque S. Rasool, Donald L. De Vincenzi, and John Billingham
2. Cultural Evolution.
Mark A. Stull
3. Detection of Other Planetary Systems.
Jesse L. Greenstein and David C. Black,
4. The Rationale for a Preferred Frequency Band: The Water Hole.
Bernard M. Oliver
5. Search Strategies.
Charles L. Seeger
6. The Science of SETI.
David C. Black and Mark A. A

 

[xii] III. COMPLEMENTARY DOCUMENTS

 
1. Alternative Methods of Communication.
John H. Wolfe
2. Notes on Search Space.
Charles L. Seeger
3. Parametric Relations in a Whole Sky Search.
Bernard M. Oliver
4. Stellar Census.
Charles L. Seeger
5. Summary of Possible Uses of an Interstellar Search System for Radio Astronomy.
Jeffrey N. Cuzzi and Samuel Culkis
6. SETI Related Scientific and Technological Advances.
David C Black and Mark A. Stull
7. A Preliminary Parametric Analysis of Search Systems.
Roy Basler
8. Radio Frequency Interference.
Mark A. Stull and Charles L. Seeger
9. Protection of a Preferred Radio Frequency Band.
Mark A. Stull
10. Responses to a Questionnaire Sent to Leading Radio Observatories.
Philip Morrison
11. The Soviet CETI Report.
12. Searches to Date.
13. The Maintenance of Archives.
Charles L. Seeger
14. Selected Annotated Bibliography.
15. Workshop Members, Biographical Information, Workshop Meetings.
 
[xiii] BRIEF TITLES FOR ILLUSTRATIONS
 
Annotated Star Field.
View of Arecibo Observatory in Puerto Rico.
Frequency scan of a [alpha]-Ophinchi.
The Orion Nebula.
Arecibo search for ETI in M33.
Antennas at NASA Mohave R & D site.
Westerbork synthesis map of M51.
Concept of 300-m space SETI system.
 
BRIEF TITLES FOR FIGURES
 
SECTION II-4
Figure 1 - Free space microwave window.
Figure 2 - Terrestrial microwave window.
Figure 3 - Free space temperature bandwidth index.
Figure 4 - Terrestrial temperature bandwidth index.
 
SECTION II-5
Figure 1 - Some frequency allocations in the microwave window.
Figure 2 - Major parameters of signal detection.
 
SECTION III-2
Figure 1 - Pulsar signature.
 
SECTION III-3
Figure 1 - Off-axis signal detection scheme.
Figure 2 - System sensitivity relations.
Figure 3 - Antenna size requirements.
 
SECTION III-8
Figure 1 - Bi-static radar range for ISS receiver.
Figure 2 - Peak side lobe levels of radiation patterns for large antennae.
 
[xiv] BRIEF TITLES FOR TABLES
 
SECTION II-5
Table 1 - High power terrestrial radiations.
 
SECTION III-1
Table 1 - Mass ratios for two-way trip to a[alpha]-Centauri.
 
SECTION III-2
Table 1 - Typical antenna gains.
Table 2 - Origin of system noise.
Table 3 - Powerful radars.
 
SECTION III-3
Table 1 - System parameters.
Table 2 - Detection sensitivity and cost.
 
SECTION III-5
Chart 1 - Capabilities of large SETI systems.
 


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View of Arecibo Observatory in Puerto Rico with its 300 m dish- the world's largest. A small fraction of its observation time is devoted to ETI searches.

View of Arecibo Observatory in Puerto Rico with its 300 m dish- the world's largest. A small fraction of its observation time is devoted to ETI searches.

Cover and frontispiece kindly provided by Prof. Jesse L. Greenstein, California Institute of Technology, Hale Observatory, Pasadena, California.