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NOVA-ASTRON finishes milling MATISSE reimagers

Submitter: Felix Bettonvil
Description: MATISSE, the mid-infrared interferometric spectrograph and imager for the VLTI, for which NOVA's Optical and Infrared Instrumentation Division at ASTRON builds the Cold Optical bench, has finished milling of the so-called reimagers.

MATISSE is an instrument that is designed to combine coherently the light of up to four telescopes of ESO's Very Large Telescope Interferometer (VLTI). It emulates the aperture of an up to 200-m telescope in the 2.8-5 and 8-13 micrometer wavelength bands at spectral resolutions between 30 and 5000 and spatial resolutions of the order of 5 milliarcsec. With these characteristics MATISSE is extremely well suited for study of Young Stellar Objects (YSOs), extra-solar planets and Active galactic nuclei (AGNs), asymptotic giant branch stars (AGBs) and planetary nebulae.

NOVA-ASTRON is responsible for the Cold Optical Bench (COB), being the most complex part of MATISSE, accommodating ~200 optical components, located into two boxes of roughly 70x70x40cm size, with over 8x20m(!) path length.

2013 is the year of MATISSE's manufacturing. Recently the so-called reimagers boxes (RIBs) were milled on ASTRON's 5-axis Hermle C40 milling machine. The reimagers focus the collimated light and perform spatial filtering of the star image as well as baffling of diffracted light, after which it is collimated again. Due to the very limited space envelope the beams are folded together with help of 7 mirrors per beam.
Each COB has two RIBs, being mirrored copies of each other and each symmetrical in it self. The approach guarantees maximum stability between the four channels as function of temperature. Each RIB is milled from a single piece of stress relieved 6061 aluminium.

With the milling finished, the RIBs are now being prepared to leave ASTRON temporarily for both coordinate measurements and surface coating, after which assembly of the reimager will start.
Copyright: NOVA Optical and Infrared Instrumentation Division at ASTRON
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