Wavefront sensor testing in hypersonic flows using a laser-spark guide star

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Wavefront sensor testing in hypersonic flows using a laser-spark guide star

Neal, D.R. / Armstrong, D.J. / Hedlund, E. / Lederer, M. / Collier, A. / Spring, C. / Gruetzner, J. / Hebner, G. / Mansell, J.

Abstract

The flight environment of next-generation theater missile defense interceptors involves hypersonic speeds that place severe aero-thermodynamic loads on missile components including the windows used for optical seekers. These heating effects can lead to significant boresight error and aberration. Ground-based tests are required to characterize these effects. The authors have developed methods to measure aberrations in seeker windows using a Shack-Hartmann wavefront sensor. Light from a laser or other source with a well known wavefront is passed through the window and falls on the sensor. The sensor uses an array of micro-lenses to generate a grid of focal spots on a CCD detector. The positions of the focal spots provide a measure of the wavefront slope over each micro-lens. The wavefront is reconstructed by integrating the slopes, and analyzed to characterize aberrations. During flight, optical seekers look upstream through a window at 'look angles' angles near 0 degrees relative to the free stream flow. A 0 degree angle corresponds to large angles approaching 90 degrees when measured relative to the normal of the window, and is difficult to simulate using conventional techniques to illuminate the wavefront sensor during wind tunnel tests. For this reason, they developed a technique using laser-induced optical breakdown that allows arbitrary look angles down to 0 degrees.

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Document information

Title :

Wavefront sensor testing in hypersonic flows using a laser-spark guide star

Contributors:

Neal, D.R. (author) / Armstrong, D.J. (author) / Hedlund, E. (author) / Lederer, M. (author) / Collier, A. (author) / Spring, C. (author) / Gruetzner, J. (author) / Hebner, G. (author) / Mansell, J. (author)

Published in:

Optical Technology in Fluid, Thermal, and Combustion Flow, 3 ; 347-359

Proceedings of the SPIE - The International Society for Optical Engineering ; 3172

Publication date :

1997

Size :

13 Seiten, 9 Quellen

ISSN :

0277-786X

DOI :

https://doi.org/10.1117/12.293400

Type of media :