The Search for Extraterrestrial Intelligence
in the Optical Domain using a three channel
coincident photometer
in the Optical Domain using a three channel
coincident photometer
Bruce Howard
Astromechanical Laboratory
March 6, 2006
Revised: 8/10/2014
Astromechanical Laboratory
March 6, 2006
Revised: 8/10/2014
Principals of the SETI Photometer
•This device works on the idea that an ETI may use a powerful pulsed laser as a means to establish contact over galactic distances. First proposed in the 1960’s and quickly rejected, this idea has enjoyed a renaissance in recent years as it became apparent that Earth technology had advanced to the point that it was now possible to build and use such a laser using only technology already available in 2000.
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•The basic premise is that a pulsed laser beam of nanosecond duration could outshine the sender’s own sun by many orders of magnitude. Detection is therefore based on the simultaneous reception of many photons over a nanosecond time scale.
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•Photomultiplier tubes are an ideal detector for this instrument due to their inherently fast rise time and relative freedom from noise.
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•The basic premise is that a pulsed laser beam of nanosecond duration could outshine the sender’s own sun by many orders of magnitude. Detection is therefore based on the simultaneous reception of many photons over a nanosecond time scale.
•
•Photomultiplier tubes are an ideal detector for this instrument due to their inherently fast rise time and relative freedom from noise.
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Features of the SETI Photometer
The incoming light cone from the telescope is divided up among the three detectors using two beam splitters. The first detector receives 30% of the total light while the remaining 70% is equally divided among the other two.
Each detector assembly includes a subminiature PMT and socket assembly located inside of a thermo-cooled enclosure. The cooling is provided by a Peltier module and a copper heat exchanger. The temperature is automatically regulated at -20 degrees Centigrade by custom electronics in the control cabinet. A small housing machined from industrial plastic connects the housing to the remainder of the structure. This reduces the flow of heat into the housing and provides a location for the field lens.
An aperture plate is placed at the focal plane of the instrument to restrict the field of view to about 25 arc seconds. This plate can be moved out of the light path when an unrestricted view of the focal plane is required – such as during the acquisition of the target star and roughly centering it in the field of view. The focal plane can be inspected by two eyepieces installed on a turret assembly. One of these eyepieces is equipped with an illuminated reticule for precision centering of the target star in the aperture plate
Each detector assembly includes a subminiature PMT and socket assembly located inside of a thermo-cooled enclosure. The cooling is provided by a Peltier module and a copper heat exchanger. The temperature is automatically regulated at -20 degrees Centigrade by custom electronics in the control cabinet. A small housing machined from industrial plastic connects the housing to the remainder of the structure. This reduces the flow of heat into the housing and provides a location for the field lens.
An aperture plate is placed at the focal plane of the instrument to restrict the field of view to about 25 arc seconds. This plate can be moved out of the light path when an unrestricted view of the focal plane is required – such as during the acquisition of the target star and roughly centering it in the field of view. The focal plane can be inspected by two eyepieces installed on a turret assembly. One of these eyepieces is equipped with an illuminated reticule for precision centering of the target star in the aperture plate