ALPAO selected for adaptive-optics upgrade on VLTI telescopes

ALPAO (Grenoble, France), which designs and makes adaptive optics (AO) products, say that it will supply all the deformable mirrors to equip the auxiliary telescopes that form part of ESO's Very Large Telescope Interferometer (VLTI) array at the Paranal Observatory in Chile.

In 2018, the VLTI will undergo a major improvement with the installation of the New Adaptive Optics Module for Interferometry (NAOMI) on each of its 1.8 m Auxiliary Telescopes (ATs). This long-waited upgrade will allow the astronomers to reconstruct images of fainter objects such as young pre-main-sequence stars and their protoplanetary discs, post-main-sequence mass-losing stars, and active galactic nuclei.

The ALPAO deformable mirror is at the center of the NAOMI system. It will change shape at about 500 Hz to actively counteract the effect of atmospheric turbulence. The ALPAO deformable mirror (DM) can also move the star image a few times per second to monitor the brightness of the sky itself. This technique, called chopping, is needed for the forthcoming MATISSE instrument, which will observe in far-infrared light.

NAOMI will benefit from the fast and very large stroke of the ALPAO DM,  allowing the ATs to correct for both tip-tilt and higher-order correction, notesVincent Hardy, general manager of ALPAO.

Two off-the-shelve deformable mirrors from ALPAO underwent four months of intensive testing at the Institute for Planetary Sciences and Astrophysics of Grenoble (IPAG, France). The results validate the suitability of the ALPAO mirrors for NAOMI, especially the need for a large amount of deformation. Procurement is now ongoing for the three remaining pieces (four telescopes plus one spare). Tirst light for the four ATss equipped with NAOMIs is expected in mid-2018.


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