1 / 12

Advanced Modeling Techniques for Multi-Conjugate Adaptive Optics (MCAO) Systems

Explore the optimization of MCAO models using advanced numerical simulations, hardware considerations, and turbulence effects to enhance astronomical observations. Learn about engineering tolerances, LGS performance, and the impact of spot elongation.

tuan
Download Presentation

Advanced Modeling Techniques for Multi-Conjugate Adaptive Optics (MCAO) Systems

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. MCAO at CfAO meeting M. Le Louarn CfAO - UC Santa Cruz Nov. 22 2000

  2. Goal of MCAO modeling • Can one use 1 NGS measuring 5 modes instead of 3 NGS measuring TT ? • Limiting magnitude with NGS ? • Sky coverage ? • Astrophysical implications of MCAO • ELTs: Is it possible to use N LGS and only 1DM (closed loop problem ?) for correction in the visible ? • Effect of spot elongation on MCAO • […] • AO engineering modelling (engineering tolerences) • Lasers ? • NGS - MCAO ? Probably not because of low SC, but can use a lot of faint stars (?) • Effect of the NGS star distribution (no perfect triangles) • MCAO: smaller SC than with single NGS AO. • JPV: MCAO SC on HST targets -> MCAO CoDR

  3. MCAO Modeling • Full numerical Monte Carlo Simulation • 3 DMs, 5 LGS, 7 atmospheric layers (~ Gemini) • 13x13 SH for each LGS (with SH spot speckles) • 3x3 SH for 1 NGS (instead of 3 TT NGS @ Gemini) • Least-squares inversion of IM (SVD) • Closed loop, obtain PSF anywhere in the FOV • Analytic covariance code (Tokovinin et al.) • Covariances of Zernikes computed for measurements & reconstructions • Knowledge of Cn2 profile • Optimal estimation of the correction • Open loop • Obtain residual WF error anywhere in the FOV

  4. Analytic vs. Numerical Black: Analytic & Numerical isoplanatism, Red: Numerical MCAO, Blue: Analytical MCAO

  5. H Band

  6. J Band

  7. What could go wrong in simulations ? • Atmosphere is not as simulated: • There are many turbulent layers, almost continuous profile, outer scale L0 -> effect on high altitude DM density ? • Strong turbulence profile variations in closed loop • Propagation effects • Non-Kolmogorov turbulence, Non-Taylor turbulence • Na layer / LGS properties • Height variations: difficult to put in but can get an estimate • Spot elongation (  ELTs): can be simulated for 8m tel. • Lasers for MCAO • Hardware issues: AO simulation validity ??? • High order aberrations in mirrors, DM mis-registration... • MCAO waffle modes on real DMs • DM hysteresis effects • edge effects • laser launch telescope jitter -> total least squares

  8. Cn2 profiles

  9. Cn2 profiles

  10. Lab/sky tests • Atmosphere: • Continuous turbulence (not repeatable ?) + thin layers (?) • Turbulence generator • Phase screens • Propagation effects • Phase screens • Non-Kolmogorov screens • Na Layer: • Studies on LGS AO systems ? • Site monitoring (Na profile measurements) • Lab MCAO system: • control algorithm testing, system tolerances • DM hysteresis • AO Systems: DO NGS AO system work as modelled ? (Lick AO, Keck, Pueo…)

  11. Why lab / sky tests ? • Lab test = acceptance test of the MCAO system: saves money • Have you thought of everything ? • 1DM LGS AO system: • Na Layer saturation checked • Engineering for Keck, VLT,... • Sky testing / site monitoring -> Do we have the right parameters ? • Ragazzoni test on the sky did it bring anything good ?

More Related