project Auxiliary Telescope Systems (VLTi)

AMOS realized the design, procurement, manufacturing, assembly, factory testing and packing of the four mobile Auxiliary Telescope Systems for the ESO VLT Project, located on the Paranal Mountain in Chile.

The Auxiliary Telescopes are actually a complex system of moving telescopes. This concept of movable telescopes is unique. Any telescope can be relocated from one station to any other in less than 3 hours.

Despite the complexity of a high-grade 1.8m telescope able to send the light beam down a well in all the possible positions, they had to be installed with all their electronics and handling systems on a compact transporter with a robust dome. The transporter has to move on rails and be able to locate the telescopes with a high precision on a set of pre-selected locations.


AMOS developed all the site equipment related to the 30 observation stations. This includes the rail network and the 30 docking stations but also all the support equipment necessary for the installation and alignment of the 30 stations.

The constraints for this interferometer were:

  • Primary mirror of 1.87 m in diameter, lightweighted at 60%, with a 40nm RMS WFE for every altitude angle between 30° and zenith,
  • Optical path length variation under operational loads better than 30nm RMS in the visible range.
  • Pointing accuracy is better than 1 arcsec RMS on the sky for the whole azimuth (360°) and altitude (60°) ranges.
  • Able to be relocated in thirty stations on the Paranal site with a repeatability of 0.1mm and 10 arcsec thanks to a fully autonomous “transporter”.
  • Thermally-conditioned during day for minimizing mirror and dome seeing effects.

Head photo and photos 2 to 8: Credit ESO
Published on 15.09.2018
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