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Center Independent Research & Development: JPL IRAD

Cryogenic Active Mirrors (CAM)

Completed Technology Project

Project Introduction

This effort seeks to develop active mirrors that can correct for thermally-induced figure deformations upon cooling from room-temperature at the time of manufacture, down to cryogenic temperatures (4K) during operation.  To do so, an array of piezoelectric actuators are distributed across the backside of a lightweighted silicon carbide substrate in a surface-parallel fashion.  Each actuator can "push" or "pull" on the surface through the application of an electric field.  This actuation scheme has been performed for room temperature mirrors, however it has yet to be demonstrated at cryogenic temperatures.  This is the primary focus of the current effort.

The primary goal of the Cryogenic Active Mirror (CAM) technology development effort was to demonstrate comparable active figure control at room and cryogenic temperatures.  This was performed experimentally by constructing a small-scale demonstrator mirror and subjecting it to cryogenic temperatures in a thermal-vacuum chamber.  This test provided a comparison of actuation stroke and figure correctability at both temperatures.  The second objective of this effort was to establish a point design for a 4x6m active aperture for a notional Far-IR telescope  This was performed using a finite element model (FEM), along with results from the experimental campaign.  In doing so, predictions on mirror stiffness, mass, and ability to correct for gravity sag and thermal deformations was established.  Finally, the last objective was to explore new methods of actuation that require zero voltage to maintain their specific actuation state.  This was performed by material characterization of piezoelectric materials at reduced temperatures.

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