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Optical Engineering

Stochastic Model For Photon Noise Induced By Charged Particles In Multiplier Phototubes Of The Hubble Space Telescope Fine Guidance Sensors
Author(s): Leonard W. Howell; Hans F. Kennel
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Paper Abstract

The Hubble Space Telescope (HST) will be subjected to charged particle strikes in its space environment. HST's onboard fine guidance sensors utilize photomultiplier tubes (PMTs) for attitude determination. These tubes, when subjected to charged particle strikes, generate "spurious" photons in the form of Cerenkov radiation and fluorescence, which can give rise to unwanted disturbances in the pointing of the telescope. This paper presents a stochastic model for the number of these spurious photons that strike the photocathode of the photomultiplier tubes, which in turn produce the unwanted photon noise. Based on thousands of simulated charged particle strikes, the probability distribution of Cerenkov radiation and fluorescence was obtained. The results of the simulation demonstrate that the Cerenkov noise and fluorescence noise are not statistically dependent to the degree that the Cerenkov pulse amplitude could be used as reliable warning of the fluorescence. This finding prompted an engineering hardware change that will eliminate the possibility of telescope pointing disturbances caused by charged particles. The model that has been programmed, complete with three-dimensional graphics of the charged particle/PMT window interaction, allows for easy adaption to a wide range of charged particles and different phototube parameters.

Paper Details

Date Published: 1 April 1986
PDF: 11 pages
Opt. Eng. 25(4) 254545 doi: 10.1117/12.7973858
Published in: Optical Engineering Volume 25, Issue 4
Show Author Affiliations
Leonard W. Howell, NASA (United States)
Hans F. Kennel, NASA (United States)

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