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A Method to Measure the Flatness of the LSST Focal Plane Assembly in Situ

Willy Langeveld

astro-pharXiv:astro-ph/0511058

Abstract

In this note I describe an inexpensive and simple laser-based method to measure the flatness of the LSST focal plane assembly (FPA) in situ, i.e. while the FPA is inside its cryostat, at -100 C and under vacuum. The method may also allow measurement of the distance of the FPA to lens L3, and may be sensitive enough to measure gravity- and pressure-induced deformations of L3 as well. The accuracy of the method shows promise to be better than 1 micron.

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