Post on 23-Dec-2015
transcript
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ASTRI SST-2MThe Prototype
Telescope
dual-mirror Schwarzschild-Couder
FoV = 9.6° EFL = 2150 mm
Daniele Gardiol – SPIE Advanced Telescopes and Instrumentation 2014, Montréal, Quebéc, Canada, June 23rd
Secondary mirror
monolithic 1.8 m
Primary mirror
segmented 4.3 m 18 hex elements 850 mm side-to-side
Focal plane camera
compact (50x50x50 cm3) based on Si-PMs sensors.
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Active Optics systemPrimary Mirror active supports
Daniele Gardiol – SPIE Advanced Telescopes and Instrumentation 2014, Montréal, Quebéc, Canada, June 23rd
M1 segment support
One fixed point Two axial actuators Total stroke > 10 mm Positioning accuracy < 3µm Prototype for lab test
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Active Optics systemSecondary Mirror active support
Daniele Gardiol – SPIE Advanced Telescopes and Instrumentation 2014, Montréal, Quebéc, Canada, June 23rd
M2 active support
Three axial actuators Tilt + Focus Whiffletrees to share load Total stroke ~ 15 mm
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Active Optics systemAlignment tracking system
Daniele Gardiol – SPIE Advanced Telescopes and Instrumentation 2014, Montréal, Quebéc, Canada, June 23rd
Each M1 segment is equipped with a laser which beam follows the optical path of the telescope
Spot position is tracked via two CCDs located at the camera edges and provides feedback on mirror tilt
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Active Optics systemActive Mirror Control Unit
Daniele Gardiol – SPIE Advanced Telescopes and Instrumentation 2014, Montréal, Quebéc, Canada, June 23rd
Telescope Control System
OPC-UA Client Telescope Control Unit
Active Mirror Control Unit (dedicated PC)
Twincat 3 (Beckhoff)
ATSKM M1 M2
Main OPC-UA ServerDB
Engineering interface
ADS
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Kinematic modelPerformance prediction
Daniele Gardiol – SPIE Advanced Telescopes and Instrumentation 2014, Montréal, Quebéc, Canada, June 23rd
Geometricalmodel
Opticalmodel
Segmentmodel
Behaviourprediction
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0n
nknk pct
),(2/)(
),(2/)(
2121
2121
ttottv
ttottu
p1 p2
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Kinematic modelSystem calibration
Daniele Gardiol – SPIE Advanced Telescopes and Instrumentation 2014, Montréal, Quebéc, Canada, June 23rd 7
Example:
Seventh order polynomial Image shifts up to
mm residuals for whole M1 (18 segments) > 99% of residuals are below the
hardware positioning accuracy of actuators
Residuals
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Conclusions
Daniele Gardiol – SPIE Advanced Telescopes and Instrumentation 2014, Montréal, Quebéc, Canada, June 23rd
active positioning is performed by means of axial actuators driven by stepper motors
an alignment tracking system provides feedback on the mirrors alignment. It will be used also during calibrations
can operate in stand alone mode or within the Telescope Control System A complete kinematic model predicts system performance, quantifying non-
linearities (dominated by the M1 axial actuator behaviour) A simulation of the calibration procedure shows that it is possible to
describe and correct the image shift induced by mirrors tilt over the whole range allowed by the hardware with a seventh order polynomial, being the residuals well below the mechanical accuracy positioning of the actuators