Optical SETI Survey - Introduction (Part A)
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"Where no photon has gone before?"
To all members of OSU's RADOBS bulletin board from Stuart Kingsley:
I thought I would go through the exercise of listing (delineating) many of the areas I have investigated in my Optical SETI study, and my rationale. In order to make it easier for RADOBS members to read, digest and download this Survey, it has been split into seven roughly equal parts, which will be sequentially uploaded over the Christmas/New Year period. Each statement or question is concluded with a YES or NO response. Print out each part and circle your responses - it should be very revealing! I would appreciate receiving your comments and scores through email, through the post, or hearing about them by phone. Do not respond with your scores until the complete Survey is posted on RADOBS, as you may wish to go back and revise your earlier responses. A form is provided at the end of Part G to facilitate responding by mail or email. Hopefully, this series of communications should initiate a lively debate on RADOBS as to the merits of the optical approach to SETI, a critique of my rationale, and contributions from others to add to the Optical SETI rationale delineated herein.
I have believed for several decades that the universe is crawling with intelligent life, particularly, as even the Milky Way Galaxy alone is thought to contain 400 billion stars, and there are more galaxies in the universe than stars in our galaxy. As you are reading this introductory message, you obviously don't need to be convinced about the merits of the "search". I think that in time, mankind may well discover the means to take short-cuts across the galaxy and may develop sub-space communication techniques (ala Star-Trek) that overcome the limits of the speed of light. However, the latter is in the realms of science fiction. From our present state of knowledge, it would appear that in preference to physically travelling over the vast distances of interstellar space, with corresponding enormous expenditures of energy and time, electromagnetic radiation is the cheapest form of travel, and is the next best thing to actually being there.
The Optical SETI rational delineated in the Survey, is based on science as we know today, and a little imagination - admittedly somewhat anthropocentric. We assume that advanced technical civilizations (ATCs) still use electromagnetic communication technology in a big way, and have the desire to contact emerging technical civilizations (ETCs). It is also not out of the question that we might accidently intercept signals passing our way and not meant for our ears or eyes!
The real issue here is what form of electromagnetic communication technology would be used - on what type of photon would we hitch a ride? Would it be on microwave photons (radiation) which has the benefit of very low interstellar background noise, or would it be on optical photons (far- infrared to ultra-violet) that has the benefit of extremely high Effective Isotropic Radiated Powers (EIRPs), and compact transmitting/receiving antennas, but suffers from significant quantum noise.
I have never seen a field of science so flawed with misconceptions and half- truths. It is recognized that I will have to work very hard to convince the SETI Community that much of what they have believed for the past 30 years is in error. Many of the so-called problems with Optical SETI, e.g., very high Doppler shifts and drifts (chirp), have relatively simple technological fixes. I will let you be the best judge after you have worked through the following statements and questions. Even if you are not finally convinced that the optical approach to SETI is the best, I feel confident that it will be hard for you to escape the conclusion, that any serious SETI enthusiast who avoids looking in the optical regime, substantially diminishes the chance of the successful detection of Extraterrestrial Intelligence (ETI).
My Optical SETI study is mainly centered on space-based transmitting and receiving systems. Recent developments in ground-based adaptive telescope technology using laser guide stars would appear to indicate that within a few years, ground-based visible telescopes will be able achieve diffraction limited performance equivalent to that of space-based systems. This will probably have a profound affect on ground-based astronomy, and Optical SETI.
Studies also indicate that Optical SETI is the one branch of optical astronomy, save for solar astronomy, that can actually be done during the day, under a clear blue sky.
Please note, as explained in an earlier message, that my definition of the umbrella word "optical" is accordance with the popular optoelectronics or photonics definition, i.e., it covers the wavelength range from ultra-violet to far-infrared. This corresponds to wavelengths from about 300 nm to more than 30,000 nm. The Carbon Dioxide laser, which has many lines between 9,000 and 11,000 nm, is one of the most efficient and coherent lasers in existence, and CO2 is likely to be readily available to ETIs in their planetary atmospheres. Although the main Carbon Dioxide laser line of 10,600 nm (where there is an atmospheric window) would appear to be an optical "magic wavelength", I think that in time we will probably identify several "magic wavelengths" or their corresponding "magic frequencies" in the visible spectrum. Visible laser systems have the advantage of even greater EIRPs, though some argue that their beamwidths can be too small, making targeting very difficult.
Now read on for an adventure in imagination. Discover for yourself the probability that artificially-produced extraterrestrial optical photons have been falling on the Earth for millennia. The adventure begins . . . .
December 17, 1990 RADOBS.07A BBOARD No. 273
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Dr. Stuart A. Kingsley Copyright (c), 1990 * * AMIEE, SMIEEE * * Consultant "Where No Photon Has Gone Before" * * __________ * * FIBERDYNE OPTOELECTRONICS / \ * * 545 Northview Drive --- hf >> kT --- * * Columbus, Ohio 43209 \__________/ * * United States .. .. .. .. .. * * Tel. (614) 258-7402 . . . . . . . . . . . * * email@example.com .. .. .. .. .. * * CompuServe: 72376,3545 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *