The Arcetri Adaptive Optics group history

Arcetri Observatory Adaptive Optics (AdOpt) group born in the 1990s under the guidance of Piero Salinari, when he proposed to provide the Large Binocular Telescope (LBT) – that was in development under the name of Columbus Telescope – with a deformable secondary mirror (1). With the help of Ciro Del Vecchio who made finite element analysis and Valdemaro Biliotti who developed a simple and accurate capacitive sensor, the first design of an Adaptive Secondary Mirror (ASM) was completed in 1993. In the following years, the group worked, in collaboration with Microgate and ADS, on some prototypes: a 30 actuator prototypes, P30 (REF), was built in 1997 and a large one, P36, was completed and successfully tested in 1999.

At the same time, Roberto Ragazzoni and Simone Esposito developed the Pyramid WFS for Telescopio Nazionale Galileo which reached first light in 2001 (REF1,REF2).

2002 is the year of the first Adaptive Secondary Mirror on a telescope: MMT becomes an adaptive telescope with a 640mm f/15 secondary with 336 actuators (REF1, REF2, REF3).

After these projects Arcetri Adaptive Optics group focused on the Adaptive Optics system of LBT: the First Light Adaptive optics (FLAO) system. Several new people joined the group to meet the need of designing and building 2 pyramid WFSs and 2 ASMs — LBT is a binocular telescope!

Preliminary on-sky results in 2010 shown that FLAO is able to reach 90% SR in H band (REF1,REF2). No other system at that time can do the same (REF). This gave the scientific community the proof of the advantages of Pyramid WFS and ASM.

Then, the group continued to work on the ASM technology development as partner of the AdOptica Consortium and became part of several consortiums for developing new instruments:

• LBT Advanced Rayleigh guided Ground layer adaptive Optics System (ARGOS – first light 2015, REF1, REF2) and Single conjugated adaptive Optics Upgrade (SOUL – first light 2018, REF).
• Magellan Adaptive Optics system (Mag-AO – first light 2012, REF) for Magellan Telescopes (which comprises a 585 actuators ASM and a pyramid WFS).
• Enhanced Resolution Imager and Spectrograph (ERIS – FDR 2017, REF1, REF2) and MCAO Assisted Visible Imager and Spectrograph (MAVIS – phase A started 2018, REF) for ESO VLT.
• Natural Guidestar Wavefront Sensor (NGWS – PDR 2013, REF) for GMT.
• Multi-conjugate Adaptive Optics RelaY (MAORY – phase B started in 2016, REF1, REF2) for ESO ELT
• ESA Large Aperture Telescope Technology (LATT) project (ended in 2015) which proved that ASM technology can be adapted to lightweight large aperture deployable space telescopes (REF1, REF2).

Finally, we would like to highlight that after the excellent results of FLAO many other observatories,in addition to those already listed, added or planned to add a Pyramid WFS or/and an ASM to their telescopes:

• Starting from 2014 Subaru Coronagraphic Extreme Adaptive Optics (SCExAO, REF) was equipped with a pyramid WFS.
• In 2016 ESO Very Large Telescope (VLT) Unit Telescope number 4 (UT4) started using the Deformable Secondary Mirror (DSM) an ASM with 1170 actuators (REF).
• In 2018 Keck Planet Imager and Characterizer (KPIC) was installed at the Keck telescope. This instrument is equipped with an infrared Pyramid WFS (REF).
• All the three next generation telescopes: Giant Magellan Telescope (GMT) and ESO Extremely Large Telescope (ELT) and Thirty Meter Telescope (TMT) will have single conjugate AO systems which uses Pyramid WFSs (REF1, REF2, REF3), and both GMT and ELT will be equipped with ASM technology (REF1,REF2).

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(1) the idea of a deformable mirror which is part of the telescope optical train was first proposed by Jacques Beckers in 1989

-- GuidoAgapito - 16 Jan 2019