OSETI - Optical Search for Extra-terrestrial Intelligence Kristina Krylova: kkrylova@buffalo.edu, University at Buffalo – SUNY

Dr. Corbin Covault: corbin.covault@cwru.edu, Case Western Reserve University

Abstract

Over the last decade, the optical search for extraterrestrial intelligence has become a subject of research in various locations in the US including Case Western Reserve University. When coming up with a design for a detector to activate when it sees an extraterrestrial signal the main issues are to ensure that it will not falsely trigger due to light from cosmic ray air showers nor from the random fluctuations of the night sky background. For my REU at Case I have simulated the night sky background for various detector layouts in order to determine the optimal design and threshold of the detector so that it will effectively eliminate background and yet be sensitive enough to detect an optical signal.

History Timeline

1959: Giuseppe Cocconi and Philip Morrison had the idea that an extraterrestrial intelligence might be communicating with us via high frequency radio wavesMay 16, 1960: Theodore Maiman made the first operational laser in Hughes Research Laboratory, California1961: Robert Schwartz and Charles Townes published a paper suggesting the possibility of interstellar communication via the emission of a light pulse such as a laserstill the use of radio waves persisted for several decades until the laser technology was improved1993: Columbus Optical SETI Observatory in Bexley, Ohio directed by Stuart Kingsley was the first observatory to become operational in North AmericaOctober 19, 1998: the Harvard telescope joined the OSETI effortssince 1999: UC Berkley’s Leuschner telescope; the same year Princeton joined the Harvard groupDecember 27, 2000: Lick Observatory in University of California2007: Corbin Covault at Case Western Reserve University

Detector Facts

Each elementary detector will consist of the following features:one Fresnel lens having the dimensions of 1.40m by 1.05mfour 1.5 inch in diameter photomultiplier tubes each observing only a certain region of the skythe photomultiplier tubes will record data every 4 nanoseconds

Elementary detector’s procedure for determining the amount of light it sees:

Double detector setup:see Figure 1 right sideone mega detector consists of nine elementary detectorsthe signals from all photomultiplier tubes from the nine component detectors are combined to an analog sum of one huge detector signalif the total signal is greater than a certain threshold, then the mega detector signals an external device indicating that it saw somethingtwo mega detectors are set up a distance apart and an external device interprets when both detectors trigger at the same time thereby limiting the number of times the setup is set off by accidentif both detectors send a signal within a certain time interval, it means that they saw an unusual amount of photons at the same time so there is potential that it was due to an unnatural source

The whole setup will be installed at Kent State in Ashtabula, Ohio due to location’s minimal urban activity thereby lowering the amount of background light.

Night Sky Background Simulation

Conclusion

Looking at the night sky background for various detector setups one can conclude that the quad mega detector would be most effective in lowering the number of times the detector will falsely trigger for each threshold. This improves the sensitivity of the system which will allow us to see a dimmer signal coming from an extraterrestrial source. On the other hand, the quad mega detector is twice as expensive as the double mega detector, thus the final detector design will be determined based on how much funding would be allocated to the project.

References

Covault, C., Hanna, D., Ong, R., Driscoll, D. (2008, May 1). The Double-Twin-Mirror Optical SETI Observatory: A Proposal to Foundational Questions in Physics and Cosmology.Optical SETI at Harvard. Retrieved July 14, 2010 from http://seti.harvard.edu/oseti/The Search For Extraterrestrial Intelligence (SETI) In The Optical Spectrum: A Review. Retrieved July 15, 2010 from http://www.coseti.org/paper_01.htmFresnel lens. Retrieved July 17, 2010 from Nihon Tokushu Kogaku Jushi Co., Ltd. Web site: http://www.ntkj.co.jp/product_fresnel_en.html

Acknowledgements

I thank the NSF for financial support with the DMR-0850037 grant along with Dr. Corbin Covault and his High Energy Astrophysics group at Case Western Reserve University for help and mentorship in this undertaking.

see Figure 1 left sidephotons pass through the lens and are focused at the centerdepending on which region of the sky the photons came from, they are detected by one of the four photomultiplier tubes

Figure 1

Quad detector setup:see Figure 2just like for the double detector the threshold will be set on the sum of nine elementary detectorsthen four mega detectors will be taken a certain distance apart and a device will be looking for all four of the detectors to trigger at the same time Figure 2

Here is a histogram showing how many times the setup will trigger for the different combinations of mega detectors as a function of threshold due to random fluctuations of the night sky brightness in Ashtabula.