Polishing and testing of the 3.5 m SiC M1 mirror of the Herschel space observatory of ESA

Tapio Korhonen; Perttu Keinanen; Mikko Pasanen; Aimo Sillanpaa

doi:10.1117/12.797645

25 September 2008 Polishing and testing of the 3.5 m SiC M1 mirror of the Herschel space observatory of ESA

Tapio Korhonen, Perttu Keinanen, Mikko Pasanen, Aimo Sillanpaa

Proceedings Volume 7102, Optical Fabrication, Testing, and Metrology III; 710218 (2008) https://doi.org/10.1117/12.797645
Event: Optical Systems Design, 2008, Glasgow, Scotland, United Kingdom

Abstract

Herschel space observatory of ESA has a parabolic M1mirror of silicon carbide (SiC) with large diameter of 3.5 m, fast focal ratio of f/0.5 and extreme light-weighting to 25 kg/m², which make the polishing of the mirror a very challenging task. Use of very high surface pressure is necessary to polish efficiently this hard material, which increases the risk of quilting effects to the shape of the only 2.5 mm thick front face of the mirror. In this paper we present descriptions of the testing and polishing methods used during Herschel M1 lapping and polishing to the specified surface shape accuracy < 1.5 μm rms and micro roughness <30 nm rms.

Citation Download Citation

Tapio Korhonen, Perttu Keinanen, Mikko Pasanen, and Aimo Sillanpaa "Polishing and testing of the 3.5 m SiC M1 mirror of the Herschel space observatory of ESA", Proc. SPIE 7102, Optical Fabrication, Testing, and Metrology III, 710218 (25 September 2008); https://doi.org/10.1117/12.797645

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