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SPIRou / Infrared SpectroPolarimeter

2015 June : SPIRou parabolic mirror in construction

The Zerodur blank of the main SPIRou parabolic mirror is being controlled at SESO

Parabolic mirror

Control of the SPIRou 880mm-diameter
parent parabolic mirror at SESO-Thalès

The cryogenic spectrograph of SPIRou hosts a large double-pass parabolic mirror cut out from a parent with a clear-aperture diameter of 880mm.  The parent is to be cut into a rectangular shaped mirror of size 370x732 mm and mounted on a dedicated stress-free support (see bottom figures) allowing to reach the required performances at the cryogenic temperatures (about 80 K) at which SPIRou will operate.

The mirror and support were respectively designed by the IPAG SPIRou technical team (Patrick Rabou, Francois Hénault) and the NRC-H SPIRou technical team (Vlad Reshetov, Les Saddlemyer) under the supervision of the IRAP SPIRou core management team (Driss Kouach, Sébastien Baratchart, Marielle Lacombe).  

A call for tender was released in late 2014 for the fabrication of this critical SPIRou optical component - with the French company SESO-Thalès finally selected among the three competitors who answered the call. The machining of the parent 880mm-diameter mirror is nearing completion at SESO-Thalès (see top figure);  the forthcoming operations include

  • (i) cutting down the mirror into its final rectangular shape,
  • (ii) re-polishing it down to the requested surface accuracy (lambda / 4),
  • (iii) coating it with a high-refletance multi-layer protected coating compatible with cryogenic temperatures,
  • (iv) and finally install it in its dedicated mount.  

The mirror and mount are to be delivered at OMP/IRAP for integration into the SPIRou spectrograph by 2016 Q1.

CAD View of the parabola

Front CAD view of the SPIRou parabola in its dedicated stress-free mount

CAD View of the parabola

Back CAD view of the SPIRou parabola in its dedicated stress-free mount