NAOMI sees first light with ALPAO deformable mirrors on VLTI telescopes

The ALPAO DMs function at 500 Hz and can 'chop' the image a few times per second to monitor the brightness of the sky itself.

Adaptive-optics component and system maker ALPAO (Grenoble, France) supplied all the deformable mirrors (DMs) to equip the auxiliary telescopes that form part of ESO's Very Large Telescope Interferometer (VLTI) array at the Paranal Observatory in Chile; the DMs have now seen first light.

A New Adaptive Optics Module for Interferometry (NAOMI) has been installed on each of its 1.8-meter Auxiliary Telescopes. This long-waited upgrade allows astronomers to reconstruct detailed images of even fainter objects such as young pre-main-sequence stars and their protoplanetary discs, post-main-sequence mass-losing stars, and active galactic nuclei.

The four NAOMI modules arrived on Paranal in the first half of 2018. The ALPAO deformable mirror (DM) is the centerpiece of the NAOMI system. The NAOMI mirror will its change its shape about 500 times per second to actively counteract the damaging effect of wind and turbulences on image quality. The ALPAO DM is also able to shift the image of the star away from the image plane a few times per second in order to monitor the brightness of the sky itself. This technique, called chopping, is absolutely needed for the forthcoming MATISSE instrument, which will observe in far-infrared light.

"On some nights it looks like the atmosphere is virtually gone," says Julien Woillez, the VLTI project scientist, in a public announcement. "We can now observe much fainter objects. With NAOMI, we can now use cutting-edge second-generation instruments like PIONIER, GRAVITY, and MATISSE to their full potential."


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