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An Astronomical Search for Nanosecond Optical Pulses Using Field Programmable Gate Arrays

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  • Seminar Series
When Nov 01, 2012
from 02:00 PM to 03:30 PM
Where Engr. IV Bldg., Maxwell Room 57-124
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Curtis Mead

Harvard University



This talk elucidates the design, construction, and initial observations of a newly inaugurated search for extraterrestrial intelligence (SETI) survey.  The Planetary Society's All-sky Optical Observatory at the Harvard/Smithsonian Oak Ridge site is a 1.8 meter f/2.6 spherical mirror optical telescope that is searching for pulsed optical beacons in the northern hemisphere's night sky from declinations -20 degrees to +60 degrees, completing a full survey in ~150 clear nights. Optical pulses are captured by a custom built camera which images a 512 pixel, 1.6 degree by 0.2 degree swath of sky using two matched planes of pixelated, 1ns rise time photomultiplier tubes with sensitivity from 300nm to 920nm. A new electronic backend for the camera, designed by the Horowitz group at Harvard, makes use of off-the-shelf commercial field programmable gate arrays (FPGAs) in a novel way to create a more flexible and technically superior optical SETI camera able to sample and capture 1024 photomultiplier tube outputs at 800Msps, looking for the tell-tale flashes of light from possible pulsed laser transmitters. Previous survey cameras suffered from the inflexibility, high cost, and long design cycles of the full-custom integrated circuits used.  The engineering problem of analog-to-digital conversion on 1024 channnels at near gigasample per second speeds in a compact, economical, and flexible system is solved by using the abundant differential inputs of the FPGAs in a flash converter topology. By being entirely reprogrammable, the FPGAs allow exploration of triggering options and varying of other system parameters that were previously not possible but highly desirable on a research platform.  In operation since August 17th, the new camera has completed ~60 hours of night sky observation, captured a handful of intriguing signals, and provided a wealth of calibration and characterization data.


Curtis attended the University of Minnesota where he received a degree in Electrical Engineering, graduating summa cum laude, with honors. He then pursued a PhD in applied physics at the School of Engineering and Applied Sciences at Harvard University. While searching for a logic analyzer to borrow for a hobby microcontroller project that first summer, he met Professor Paul Horowitz, author of the renowned "The Art of Electronics." Curtis and Paul immediately connected over their shared interest in all things electronic, and Paul quickly became Curtis’s advisor and mentor. In Paul's lab, Curtis was able to satisfy his passion for electronic design and prototyping. Paul introduced Curtis to astronomy and the small community of researchers involved in the search for extraterrestrial intelligence (SETI). The subject of his talk is SETI and the final product of his PhD, a new instrument he has developed, using the myriad of electronics skills he's cultivated in Paul's lab. The new instrument, called the Advanced Allsky Optical SETI Camera is currently in operation at Oak Ridge Observatory in Harvard, MA in a search for pulsed optical laser transmitters.

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