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Published August 3, 2001 | Published
Book Section - Chapter Open

Targeted and all-sky search for nanosecond optical pulses at Harvard-Smithsonian

Abstract

We have built a system to detect nanosecond pulsed optical signals from a target list of some 10,000 sun-like stars, and have made some 20,000 observations during its two years of operation. A beamsplitter feeds a pair of hybrid avalanche photodetectors at the focal plane of the 1.5m Cassegrain at the Harvard/Smithsonian Oak Ridge Observatory (Agassiz Station), with a coincidence triggering measurement of pulse width and intensity at sub-nanosecond resolution. A flexible web-enabled database, combined with mercifully low background coincidence rates (approximately 1 event per night), makes it easy to sort through far-flung data in search of repeated events from any candidate star. An identical system will soon begin observations, synchronized with ours, at the 0.9m Cassegrain at Princeton University. These will permit unambiguous identification of even a solitary pulse. We are planning an all-sky search for optical pulses, using a dedicated 1.8m f/2.4 spherical glass light bucket and an array of pixelated photomultipliers deployed in a pair of matched focal planes. The sky pixels, 1.5 arcmin square, tessellate a 1.6 by 0.2 degree patch of sky in transit mode, covering the Northern sky in approximately 150 clear nights. Fast custom IC electronics will monitor corresponding pixels for coincident optical pulses of nanosecond timescale, triggering storage of a digitized waveform of the light flash.

Additional Information

© 2001 SPIE. We gratefully acknowledge the enlightened and continued support of The Planetary Society (TPS) and the Bosack- Kruger Charitable Foundation, and additional support from the SETI Institute. David Brown's matching contribution to TPS made possible the all-sky project. We thank Nathan Hazen and James Oliver for designing the "Garage-Mahal" observatory building. We are indebted to the night observers at Agassiz Station for their tireless efforts that bring us so many photons.

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