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LBT672
Adaptive Secondary Mirrors
Microgate, together with ADS (http://www.ads-int.com), was committed in 2002 by LBT Corporation to building the two adaptive secondaries for the Large Binocular Telescope (LBT). System design, construction and testing is in the hands of the "same old team" that has developed the adaptive secondary concept from the beginning:
- Microgate: control system design, electronics design and construction, real time software
- ADS: mechanical design, system integration
- INAF - Osservatorio Astrofisico di Arcetri (http://www.arcetri.astro.it/adopt): system design, optical design, operational software, performance optimization and testing
- Politecnico di Milano (http://www.aero.polimi.it) - Dipartimento di ingegneria Aerospaziale: control system design and simulation
The optics (thin shell and reference body) has been manufactured at Steward Observatory Mirror Lab (http://mirrorlab.as.arizona.edu).
Even if the two units are largely based on the experience gained on MMT336 adaptive secondary, several improvements have been introduced.
The electronics has been completely redesigned, with the aim of conceiving and realizing a very powerful and flexible platform, capable of being a state-of-the-art solution for controlling adaptive optics systems with up to several thousands of actuators.
Thanks to its computational power, the LBT672 electronics does not only control the mirror dynamics, but it also performs the Real Time Reconstructor computations.
LBT672 in numbers
- Mirror diameter: 911mm
- Thin mirror thickness: 1.6mm
- Number of actuators: 672
- Capacitive sensors reading noise: 2 nm rms
- Control loop frequency: 80 KHz
- Typical response time (any mode, expected): < 1 ms
- Number of control electronics crates: 6 (3 pairs)
- Number of DSP control boards: 84
- Number of DSPs: 168
- Computational power: 80 billions MACs/s (multiply and accumulate per second, 32 bit floating point)
- Real time communication speed: 4 Gbit/s
- Data transfer and computational latency: 130µs (from last WFS pixel read to commands applied to the mirror)
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 LBT 672 actuators adaptive secondary mirror assembly. Courtesy of ADS.
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 P45, the 45 actuators prototype for the LBT adaptive secondary mirror
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 DSP control board. Each board controls 8 channels, 84 identical boards control LBT672. Thanks to its computational power, close to 1 GMACs/s, the DSP boards implement also the Real Time Reconstructor. The size of the board is 195x90 mm.
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 BCU (Basic Computational Board). This board acts as real time and diagnostic communication interface. There are 6 BCUs in each LBT672, one per crate.
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