Picometer resolution interferometric characterization of the dimensional stability of zero CTE CFRP

Jorge Cordero Machado; Thomas Heinrich; Thilo Schuldt; Martin Gohlke; Stefano Lucarelli; Dennis Weise; Ulrich Johann; Achim Peters; Claus Braxmaier

doi:10.1117/12.789495

23 July 2008 Picometer resolution interferometric characterization of the dimensional stability of zero CTE CFRP

Jorge Cordero Machado, Thomas Heinrich, Thilo Schuldt, Martin Gohlke, Stefano Lucarelli, Dennis Weise, Ulrich Johann, Achim Peters, Claus Braxmaier

Author Affiliations +

Proceedings Volume 7018, Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation; 70183D (2008) https://doi.org/10.1117/12.789495
Event: SPIE Astronomical Telescopes + Instrumentation, 2008, Marseille, France

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.

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Jorge Cordero Machado, Thomas Heinrich, Thilo Schuldt, Martin Gohlke, Stefano Lucarelli, Dennis Weise, Ulrich Johann, Achim Peters, and Claus Braxmaier "Picometer resolution interferometric characterization of the dimensional stability of zero CTE CFRP", Proc. SPIE 7018, Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation, 70183D (23 July 2008); https://doi.org/10.1117/12.789495

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