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LAO Activities Relevant To Keck NGAO

LAO Activities Relevant To Keck NGAO. Donald Gavel NGAO Team Meeting 6 April 26, 2007. Outline. The Laboratory for Adaptive Optics MEMS deformable mirror development Open loop control experiments LGS tomography testbed (LTAO testbed)

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LAO Activities Relevant To Keck NGAO

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  1. LAO Activities Relevant To Keck NGAO Donald Gavel NGAO Team Meeting 6 April 26, 2007 Don Gavel: Keck NGAO meeting April 25, 2007

  2. Outline • The Laboratory for Adaptive Optics • MEMS deformable mirror development Open loop control experiments • LGS tomography testbed (LTAO testbed) Tomographic error model anchoring to laboratory experiment • Pyramid wavefront sensor Experimental validation of theory using a “very good” pyramid Don Gavel: Keck NGAO meeting April 25, 2007

  3. LAO Facility in Thimann Labs Building, UCSC Don Gavel: Keck NGAO meeting April 25, 2007

  4. Laboratory for Adaptive Optics Claire Max, Principal Investigator Joseph Miller, co-Investigator Jerry Nelson, co-Investigator Donald Gavel, Laboratory Director • A permanent facility within the UCO/Lick Observatory located at the UC Santa Cruz campus • Presently funded by a grant from the Gordon and Betty Moore Foundation • LAO Goals • Develop Adaptive optics technology and methods for the next generation of extremely large ground-based telescopes • Develop and build a planet finder instrument using “extreme” adaptive optics technology 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 Don Gavel: Keck NGAO meeting April 25, 2007

  5. MEMS DM Flattening and Control to Kolmogorov Phase Aberration Don Gavel: Keck NGAO meeting April 25, 2007

  6. MEMS surface deflection depends on linear combination of electrostatic and spring forces • Mirror surface: • Nonlinear in displacement • Linear in forces • Net force deflecting top mirror plate depends on: • Electrostatic force pulling actuator down • Spring force restoring actuator up Video credit Daren Dillon, LAO @ UCSC. MEMS courtesy Boston Micromachines Corp. Video created with Veeco interferometric microscope. Don Gavel: Keck NGAO meeting April 25, 2007

  7. Open-loop “Go-to” Control(see Morzinski et. al., this meeting, paper # 6467-15) To within 17 nm surface Don Gavel: Keck NGAO meeting April 25, 2007

  8. Set central actuator to voltage = 0V Then fE = 0 Thus fP(w,0) = fS(w) Actuate neighbors only and measure central actuator displacement Obtain spring force alone as fS = fP Electrostatic and spring force look-up tables are calibrated empirically • Repeat with varying voltages on the central actuator • Thus giving fE(w,v) = fP(w,v) - fS(w) Don Gavel: Keck NGAO meeting April 25, 2007

  9. Relation between spring force and displacement on central actuator Relation between voltage, displacement (via neighboring voltage), and plate force  electrostatic force voltage on neighbors / V plate force / ~N plate force / ~N voltage on central actuator / V voltage on central actuator / V Found relation between displacement and spring force; & relation btwn. displacement, voltage, and plate force spring force / ~N displacement / nm Don Gavel: Keck NGAO meeting April 25, 2007

  10. Applied sinusoid: Amplitude 300nm (600nm P-V) Wavelength 9 actuators Measured residuals Sinusoid applied to MEMS in open-loop. Residuals: 16nm rms; 85nm P-V Applied sinusoid. P-V = 600nm Measured sinusoid. P-V = 550nm Residuals. P-V = 85nm RMS = 16nm Don Gavel: Keck NGAO meeting April 25, 2007

  11. Applied gaussian: Height 390nm FWHM 56nm Measured residuals Gaussian applied to MEMS in open-loop. Residuals: 12nm rms; 142nm P-V Applied gaussian. P-V = 390nm Measured gaussian. P-V = 370nm Residuals. P-V = 140nm RMS = 12nm Don Gavel: Keck NGAO meeting April 25, 2007

  12. Applied Kolmogorov atmosphere phase screen Measured residuals Kolmogorov atmosphereapplied to MEMS in open-loop. Residuals: 16nm rms; 99nm P-V Applied Kolmogorov. P-V = 540nm Measured Kolmogorov. P-V = 480nm Residuals. P-V = 99nm RMS = 16nm Don Gavel: Keck NGAO meeting April 25, 2007

  13. Deformable Mirrors (SLMs) Kolmogorov Atmosphere phase aberrator plates QPI Interferometer Hartmann Wavefront Sensors LTAO/MCAO/MOAO Testbed Interferometer reference beam Open loop WFS path Ref Flat SLM NGS LGS Guide star fibers Far Field Camera • 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 Configurable guide star constellation Don Gavel: Keck NGAO meeting April 25, 2007

  14. Similarity Parameters Map the Testbed to an On-Sky CaseGemini 5 LGS constellation on 42.5 arcsec radius Don Gavel: Keck NGAO meeting April 25, 2007

  15. 5 LGS Asterism Results Error budget achieved in the lab Simulations from TSW Don Gavel: Keck NGAO meeting April 25, 2007

  16. Plate 1 at 4km Don Gavel: Keck NGAO meeting April 25, 2007

  17. 4 to predict 1 in middle Don Gavel: Keck NGAO meeting April 25, 2007

  18. 5 LGS Asterism Results • Field dependence – Mark Ammons Don Gavel: Keck NGAO meeting April 25, 2007

  19. Lenslet-Pyramid Wavefront Sensor Don Gavel: Keck NGAO meeting April 25, 2007

  20. Pyramid WFS Optical Layout Don Gavel: Keck NGAO meeting April 25, 2007

  21. Don Gavel: Keck NGAO meeting April 25, 2007

  22. Lenslet-Pyramid WFS Response to Sinusoidal Phase Don Gavel: Keck NGAO meeting April 25, 2007

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