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 MATISSE slit and pinhole slider. The challenge is to accurately position a certain slit or pinhole in the beam of each of the 4 VLT telescopes at a temperature of 38 Kelvin. At the lower right you can see four accurate laser cut slit/pinholes (shiny metal) with a slightly oversized black pinhole around each slit/pinhole to minimize spurious reflections. The slits are accurately held in position by a thicker grey metal foil, dowel pins and magnets. The holes at the upper right transmit the science beam after a reflection, but minimize the impact of diffraction and stray light.
The cross shaped element in the center of the image is a technical position for alignment purposes. If this position is selected, 2 LEDs (on the bend sections of the copper colored foil on the far left of the picture) can illuminate the alignment cross. A third LED can illuminate the circular diffuse reflective element just above the cross. Other slit/pinhole positions are not visible in this picture. In the upper left the clutch and the end switch of the sliding mechanism are visible. Accurate positioning is ensured by the use of indents (not shown in this picture).
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.