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Proceedings Paper

Picometer resolution interferometric characterization of the dimensional stability of zero CTE CFRP
Author(s): Jorge Cordero Machado; Thomas Heinrich; Thilo Schuldt; Martin Gohlke; Stefano Lucarelli; Dennis Weise; Ulrich Johann; Achim Peters; Claus Braxmaier
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Paper Abstract

Highly stable but lightweight structural materials are essential for the realization of spaceborne optical instruments, for example telescopes. In terms of optical performance, usually tight tolerances on the absolute spacing between telescope mirrors have to be maintained from integration on ground to operation in final orbit. Furthermore, a certain stability of the telescope structure must typically be ensured in the measurement band. Particular challenging requirements have to be met for the LISA Mission (Laser Interferometer Space Antenna), where the spacing between primary and secondary mirror must be stable to a few picometers. Only few materials offer sufficient thermal stability to provide such performance. Candidates are for example Zerodur and Carbon-Fiber Reinforced Plastic (CFRP), where the latter is preferred in terms of mechanical stiffness and robustness. We are currently investigating the suitability of CFRP with respect to the LISA requirements by characterization of its dimensional stability with heterodyne laser interferometry. The special, highly symmetric interferometer setup offers a noise level of 2 pm/√Hz at 0.1Hz and above, and therefore represents a unique tool for this purpose. Various procedures for the determination of the coefficient of thermal expansion (CTE) have been investigated, both on a test sample with negative CTE, as well as on a CFRP tube specifically tuned to provide a theoretical zero expansion in the axial dimension.

Paper Details

Date Published: 23 July 2008
PDF: 12 pages
Proc. SPIE 7018, Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation, 70183D (23 July 2008); doi: 10.1117/12.789495
Show Author Affiliations
Jorge Cordero Machado, EADS Astrium GmbH (Germany)
Escuela Superior de Ingenieros de Sevilla (Spain)
Thomas Heinrich, EADS Astrium GmbH (Germany)
Eidgenössische Technische Univ. Zürich (Switzerland)
Thilo Schuldt, Humboldt-Univ. zu Berlin (Germany)
Hochschule Konstanz (Germany)
Martin Gohlke, EADS Astrium GmbH (Germany)
Humboldt-Univ. zu Berlin (Germany)
Stefano Lucarelli, EADS Astrium GmbH (Germany)
Dennis Weise, EADS Astrium GmbH (Germany)
Ulrich Johann, EADS Astrium GmbH (Germany)
Achim Peters, Humboldt-Univ. zu Berlin (Germany)
Claus Braxmaier, EADS Astrium GmbH (Germany)
Hochschule Konstanz (Germany)

Published in SPIE Proceedings Vol. 7018:
Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation
Eli Atad-Ettedgui; Dietrich Lemke, Editor(s)

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