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Cesic: optomechanical technology last development results and new HBCesic highly light weighted space mirror development including corrective function 7th international conference on space optics, october 2008

Paper Abstract

Thales-Alenia-Space and ECM has developed a new SiC ceramic composite to produce very lightweight space mirrors and structure. Cesic© made by ECM has been selected for its own intrinsic properties ( high specific Young modulus, high conductivity , low CTE, high strength for a ceramics) and its large manufacturing capabilities. Recently a full monolithic space instrument for earth observation, with a monolithic Cesic© structure and with Cesic© mirrors has been designed, manufactured and space qualified and is now ready for launch. The Cesic© telescope assembly has been tested under shock environment, vibration loads, and full qualification thermal environment. All these qualification tests were done directly on the flight model.

Extensive development has been also performed to design, size, manufacture and test a very light weight reflector shell made as a single part. This 1 meter reflective shell has an areal density of less than 10 Kg/m2 has been manufactured with its surface grounded to the bi parabolic shape. Such challenging areal density has requested a very thin skin associated with a ribs thickness of less than 2mm. In order to demonstrate the high stability and strength of Cesic© the reflector has been tested successfully under very aggressive environment up to 350°C and also an acoustic test with flight representative levels was successfully performed. To produce future very lightweight space mirrors ECM develop with the support of Thales-Alenia-Space since some years an improved version of Cesic© ceramic, called HB-Cesic©. HB-Cesic© made by ECM is developed for its higher intrinsic properties, Young modulus, strength and especially its direct polishing capabilities down to 3 nm micro-roughness. One of the major targets for this development was also to overcome size limitations of the C/C raw material of currently around 1x1 m to produce mirror up to 3,5 m diameter out of a single C/C raw material block.

Under ESA study a 600 mm mirror with a surface density of only 18 Kg/m2 has been designed, sized and manufactured and is currently under polishing at SESO. The polishing to a micro-roughness of far less than 20 nm RMS without expensive overcoatings has been already validated on mirrors up to 800 mm. This 600 mm mirror will be polished to a WFE of less than 20 nm, and afterwards the mirror will be tested under cryogenic environment to measure the WFE evolution between ambient and cryo. The mirror is equipped with a system for focus and astigmatism modification. During the cryo test this system will be activated at cryo temperature to also demonstrate the function of this system. This correction system is developed for future large mirrors for interferometric nulling or aperture synthesis missions like the Darwin mission . For such missions very large and very lightweight mirrors up to 3,5 m diameter with an areal density of less than 25 Kg/m2 are required and thank to the HBCesic© technology such performance is now feasible.

Paper Details

Date Published: 21 November 2017
PDF: 9 pages
Proc. SPIE 10566, International Conference on Space Optics — ICSO 2008, 105660N (21 November 2017); doi: 10.1117/12.2308269
Show Author Affiliations
Christophe Devilliers, Thales Alenia Space (France)
Mathias Kroedel, ECM (Germany)

Published in SPIE Proceedings Vol. 10566:
International Conference on Space Optics — ICSO 2008
Josiane Costeraste; Errico Armandillo; Nikos Karafolas, Editor(s)

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