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Optics Galore

Submitter: Ramon Navarro
Description: Exciting times at NOVA-ASTRON these days. We are at the final stages of integration of the Cold Optical Bench for MATISSE; the mid-infrared interferometric spectrograph and imager for ESO's VLT interferometer (VLTI) at Paranal, Chile. Matisse can combine the light from all 4 eight-meter VLT telescopes.

In this picture you can see a detail of the reimager box; one of the main modules in the Cold Optical Bench. The reimager box conditions the signals from all 4 telescopes before they are interferometrically combined. For each telescope 9 optical components are needed to condition the light (excluding slits and pinholes). In this image alone you can distinguish 20 optical components. On the right you can see the cold stops; an undersized pupil limiting unwanted thermal radiation in the system. The gold colored parts are diamond turned, powered aluminum mirrors with a gold coating. The other elements are glass optics fixtured with a mirror clip. The glass mirrors are flat or have a very long curvature radius and are also gold coated for high reflectivity in the infrared.

In the MATISSE Cold Optics Bench the light from the telescopes is added coherently. Tolerances are extremely tight in order to achieve sufficient interferometric contrast. Despite the relatively long IR wavelengths (with respect to optical) the combined wave front error of all optical components in the reimager box is spectacular: <15nm RMS.

MATISSE is capable of imaging at spatial resolutions of ~6 milli-arcsec in the 2.8-5 and 8-13 micrometer wavelength range. This enables the study of wavelength-dependent characteristics of gas and dust grains. This includes the formation and evolution of planetary systems, Active Galactic Nuclei and high-contrast environment of evolved stars.
Copyright: Ramon Navarro
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