OSETI - Optical Search for Extra-terrestrial Intelligence

1. 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. Detector Facts Each elementary detector will consist of the following features: one Fresnel lens having the dimensions of 1.40m by 1.05m four 1.5 inch in diameter photomultiplier tubes each observing only a certain region of the sky the 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 side one mega detector consists of nine elementary detectors the signals from all photomultiplier tubes from the nine component detectors are combined to an analog sum of one huge detector signal if the total signal is greater than a certain threshold, then the mega detector signals an external device indicating that it saw something two 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 accident if 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. 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. see Figure 1 left side photons pass through the lens and are focused at the center depending on which region of the sky the photons came from, they are detected by one of the four photomultiplier tubes Figure 1 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.htm Fresnel lens. Retrieved July 17, 2010 from Nihon Tokushu KogakuJushi Co., Ltd. Web site: http://www.ntkj.co.jp/product_fresnel_en.html History Timeline 1959: Giuseppe Cocconi and Philip Morrison had the idea that an extraterrestrial intelligence might be communicating with us via high frequency radio waves May 16, 1960: Theodore Maiman made the first operational laser in Hughes Research Laboratory, California 1961: Robert Schwartz and Charles Townes published a paper suggesting the possibility of interstellar communication via the emission of a light pulse such as a laser still the use of radio waves persisted for several decades until the laser technology was improved 1993: Columbus Optical SETI Observatory in Bexley, Ohio directed by Stuart Kingsley was the first observatory to become operational in North America October 19, 1998: the Harvard telescope joined the OSETI efforts since 1999: UC Berkley’s Leuschner telescope; the same year Princeton joined the Harvard group December 27, 2000: Lick Observatory in University of California 2007: Corbin Covault at Case Western Reserve University Quad detector setup: see Figure 2 just like for the double detector the threshold will be set on the sum of nine elementary detectors then 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 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. Night Sky Background Simulation 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.