Strehl Ratio estimation

SR from H band images High Strehl PSF ->fitting with Zernike modes We suppose: No relevant loss of energy due to high modes (Z>36) Amoeba fit with First 36 Zernikes Check on residuals Generation of DL PSF and SR meas as: Peak fitted / Peak DL NO DEPENDENCE on FLUX estimation

SR from H band images Low Strehl PSF: fitting with two gaussian ditributions Halo energy >> rings energy Fit with 2 gaussians SR Relativ error on SR IRTC field in pixels Point = meas Line = fit Line = residual Total flux estimation flux_im= (Meas image – fitted bias) Flux_im thresholded to 0 flux = total(flux_im) Line = DL Line = meas psf DL generated with nominal FWHM and the energy = flux sr_meas = max(y-R[0])/max(psf_dl) DL generation and SR meaurement Repeated considering Different IRTC crops

The optical gain of the pyramid WFS depends on the size of the PSF. Since the reconstructor, R, is usually calibrated with a diffraction-limited source, the residual WF will be systematically under-estimated through the vector Estimation from real-time data Marechal approximation: Wavefront error estimation: Correction residuals: and: ! Since the gain (1/R) with high peak PSF is higher, when slopes resulting from low peak PSF are used with this lower value of R, the mirror surface error is under-estimated.

The optical gain of the pyramid WFS depends on the size of the PSF. Since the reconstructor, R, is usually calibrated with a diffraction-limited source, the residual WF will be systematically under-estimated through the vector Estimation from real-time data Marechal approximation: Wavefront error estimation: Correction residuals: and: ! There is another reason that this method underestimates the WF error. The factor sigma(res) only estimates the WF error due to spatial modes whose order is less than or equal to the number of actuators used. The higher order modes in the residual error are not included in the WFS slopes.

Comparison

MAG _ ____ Acquired PSF ____ DL Psf with same flux Closed Loop parameters Bin = 1 (30x30) Freq = 1000 Hz Flux = 232 ph/subap/frame TT Modulation = +- 2 /D N modes = 153 Gain = 0.7 H band Strehl Ratios Expected from simulations = 62 – 80 % Estimated with mirror positions = 81 % Estimated on IRTC image = % [FWHM on IRTC = 41 mas]

MAG _ FP3 Closed Loop parameters Bin = 2 (15x15) Freq = 800 Hz Flux = 140 ph/subap/frame TT Modulation = +- 3 /D N modes = 153 Gain = 0.7 H band Strehl Ratios Expected from simulations = 50 – 62 % Estimated with mirror positions = 55 % Estimated on IRTC image = % [FWHM on IRTC = 41 mas] ____ Acquired PSF ____ DL Psf with same flux

MAG _ FP5 ____ Acquired PSF ____ DL Psf with same flux Closed Loop parameters Bin = 2 (15x15) Freq = 625 Hz Flux = 40 ph/subap/frame TT Modulation = +- 3 /D N modes = 153 Gain = 0.6 H band Strehl Ratios Expected from simulations = 42 – 54 % Estimated with mirror positions = 47 % Estimated on IRTC image = % [FWHM on IRTC = 42 mas]