VLT - Very Large Telescope

Location Paranal, Chile
Customer ESO
Primary mirror:

8.2 m

Secondary mirror:

1.12 m

# Actuators:


Microgate, together with ADS, was committed in 2004 by the European Southern Observatory (ESO) to the development of a feasibility study for an adaptive secondary mirror for the VLT main telescopes (UTs).
This initial study has evolved in to a final design and then into a construction Phase, started in 2008. 

According to the baseline design, 1170 actuators distributed over the 1211mm wide mirror will provide adaptive optics correction also at visible wavelengths.

Microgate is acting as prime contractor and with ADS International beeing nominated sub-contractor.


  • 1.95mm
    Thin mirror thickness
  • 2 nm rms
    Capacitive sensors reading noise
  • 80 kHz
    Control loop frequency
  • 0.5 ms
    Typical response time
  • 6 (3 pairs)
    Number of control electronics crates
  • 78
    Number of DSP control boards
  • 160 bil. MACs/s
    Computational power
  • 4 Gbit/s
    Real time communication speed
Project status

System Assembly and integration started by mid 2011. The electromechanical tests have been successfully completed by mid 2012, confirming and even exceeding the expected dynamic performances. In Sep 2012 the system left Microgate's facilities for integration in the hub and optical tests and calibration, performed at ESO premises in Garching under Microgate's responsibility, in cooperation with INAF-Osservatorio Astrofisico di Arcetri. The optical tests have been completed in March 2013, confirming the full performance of the adaptive mirror. The unit passed a long (2.5 years) testing and calibration phase in Garching (D), in conjunction with the new adaptive optics modules (Graal, Galacsi) before installation on the telescope. In October 2016 the deformable secondary mirror was installed on the Unit Telescope 4 (Yepun).

ESO Announcements: