Don Gavel: Keck NGAO meetin Don Gavel: Keck NGAO meetin g April 25, 2007 g April 25, 2007 1 LAO Activities Relevant To Keck LAO Activities Relevant To Keck NGAO NGAO Donald Gavel Donald Gavel NGAO Team Meeting 6 NGAO Team Meeting 6 April 26, 2007 April 26, 2007
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Don Gavel: Keck NGAO meeting April 25, 2007 1 LAO Activities Relevant To Keck NGAO Donald Gavel NGAO Team Meeting 6 April 26, 2007.
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Don Gavel: Keck NGAO meeting April Don Gavel: Keck NGAO meeting April 25, 200725, 2007
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LAO Activities Relevant To Keck NGAOLAO Activities Relevant To Keck NGAO
Donald GavelDonald Gavel
NGAO Team Meeting 6NGAO Team Meeting 6April 26, 2007April 26, 2007
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OutlineOutline
• The Laboratory for Adaptive OpticsThe Laboratory for Adaptive Optics• MEMS deformable mirror developmentMEMS deformable mirror development
Open loop control experimentsOpen loop control experiments
• LGS tomography testbed (LTAO testbed)LGS tomography testbed (LTAO testbed)Tomographic error model anchoring to laboratory experimentTomographic error model anchoring to laboratory experiment
• Pyramid wavefront sensorPyramid wavefront sensorExperimental validation of theory using a “very good” pyramidExperimental validation of theory using a “very good” pyramid
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LAO Facility in Thimann Labs Building, UCSCLAO Facility in Thimann Labs Building, UCSC
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• Presently funded by a grant from the Gordon and Betty Moore Foundation
LAO Goals1. Develop Adaptive optics technology and methods for the next
generation of extremely large ground-based telescopes
2. Develop and build a planet finder instrument using “extreme” adaptive optics technology
Laboratory for Adaptive OpticsClaire Max, Principal InvestigatorJoseph Miller, co-InvestigatorJerry Nelson, co-InvestigatorDonald Gavel, Laboratory Director
3. Develop, test, and evaluate new components and key technologies for adaptive optics
4. Provide a laboratory where students and postdocs will be trained in adaptive optics design, modeling, and implementation
• A permanent facility within the UCO/Lick Observatory located at the UC Santa Cruz campus
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MEMS DM Flattening and Control to MEMS DM Flattening and Control to Kolmogorov Phase AberrationKolmogorov Phase Aberration
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MEMS surface deflectionMEMS surface deflection depends on linear depends on linear combination of electrostatic and spring forcescombination of electrostatic and spring forces
• Mirror surface:Mirror surface:• Nonlinear in displacementNonlinear in displacement
• Linear in forcesLinear in forces
• Net force deflecting top mirror Net force deflecting top mirror plate depends on:plate depends on:• Electrostatic force pulling Electrostatic force pulling
actuator downactuator down
• Spring force restoring actuator Spring force restoring actuator upup
Video credit Daren Dillon, LAO @ UCSC.MEMS courtesy Boston Micromachines Corp.
Video created with Veeco interferometric microscope.
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Open-loop “Go-to” ControlOpen-loop “Go-to” Control(see Morzinski et. al., this meeting, paper # 6467-15)(see Morzinski et. al., this meeting, paper # 6467-15)
To within17 nm surface
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• Set central actuator to Set central actuator to voltage = 0Vvoltage = 0V• Then Then ffEE = 0 = 0
• Thus Thus ffPP(w,0) = f(w,0) = fSS(w)(w)
• Actuate neighbors only Actuate neighbors only and and measure central measure central actuator displacementactuator displacement• Obtain spring force Obtain spring force
alone as alone as ffSS = f = fPP
Electrostatic and spring force look-up Electrostatic and spring force look-up tables are calibrated empiricallytables are calibrated empirically
• Repeat with varying Repeat with varying voltages on the voltages on the central actuatorcentral actuator• Thus givingThus giving
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Found relation between displacement and spring force; Found relation between displacement and spring force; & relation btwn. displacement, voltage, and plate force& relation btwn. displacement, voltage, and plate force
• Relation between spring force Relation between spring force and displacement on central and displacement on central actuatoractuator
• Relation between voltage, Relation between voltage, displacement (via neighboring displacement (via neighboring voltage), and plate forcevoltage), and plate force electrostatic forceelectrostatic force
sprin
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displacement / nmpl
ate
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voltage on central actuator / Vvo
ltage
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voltage on central actuator / V
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Sinusoid applied to MEMS in open-loop. Sinusoid applied to MEMS in open-loop. Residuals: Residuals: 16nm rms;16nm rms; 85nm P-V 85nm P-V
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LTAO/MCAO/MOAO TestbedLTAO/MCAO/MOAO Testbed
Ref Flat
SLM
Far Field Camera
Open loop WFS path
Guide star fibers
NGS LGS
Interferometer reference beam
Deformable Mirrors (SLMs)
Configurable guide star constellationHartmann Wavefront Sensors
Kolmogorov Atmosphere phase aberrator plates
• Up to 8 wavefront guide stars and 4 tip/tilt stars• 10,000 DOF per DM (100x100 subaperture Hartmann sensors)• Up to 3 DMs (MCAO) or 1 DM and open loop WFS path (MOAO)• 5 Hz sample & control rate• Moving phase plates (wind)• Moving LGS fibers in z to simulate LGS elongation, or laser pulse
QPI Interferometer
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Similarity Parameters Map the Testbed to an On-Sky CaseSimilarity Parameters Map the Testbed to an On-Sky CaseGemini 5 LGS constellation on 42.5 arcsec radiusGemini 5 LGS constellation on 42.5 arcsec radius
Laboratory for Adaptive OpticsScaling and similarity parameters for MCAO experiment