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Microscopic surface structure of C/SiC composite mirrors for space cryogenic telescopes
Keigo Enya1, Takao Nakagawa, Hidehiro Kaneda
1Department of Infrared Astrophysics, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Kanagawa, Japan. enya@ir.isas.jaxa.jp
Applied Optics
|March 27, 2007
Summary
Improved carbon-fiber-reinforced silicon carbide (C/SiC) composite mirrors exhibit reduced surface roughness after SiSiC slurry coating. These mirrors maintain stable scattering properties at cryogenic temperatures, making them suitable for space telescopes.
Area of Science:
- Materials Science
- Optical Engineering
- Astronomy Instrumentation
Background:
- Carbon-fiber-reinforced silicon carbide (C/SiC) composites are used in advanced telescope mirrors.
- Bare C/SiC mirrors exhibit microscopic surface structures and roughness due to material composition.
- Existing surface roughness can impact optical performance in cooled telescopes.
Purpose of the Study:
- To characterize the microscopic surface structure of polished C/SiC composite mirrors.
- To evaluate the effectiveness of a SiSiC slurry coating in reducing surface roughness.
- To assess the thermal stability of mirror surface properties for cryogenic applications.
Main Methods:
- Microscopic surface analysis of bare and coated C/SiC mirrors.
- Surface roughness measurements (20-100 nm rms for bare mirrors).
- Scattering property measurements at room temperature and 95 K.
Main Results:
- Bare C/SiC mirrors show surface structures attributed to material hardness differences.
- SiSiC slurry coating effectively reduces surface roughness to 2 nm rms.
- Scattering properties remain stable across temperature changes from room temperature to 95 K.
Conclusions:
- The SiSiC slurry coating significantly improves the surface quality of C/SiC mirrors.
- The enhanced C/SiC mirrors demonstrate thermal stability, crucial for cryogenic space telescopes.
- Coated C/SiC mirrors are a viable candidate for the SPICA telescope and other cooled observatories.
