Report

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 Generation of DL PSF and SR meas as: Peak fitted / Peak DL NO DEPENDENCE on FLUX estimation Check on residuals SR from H band images Low Strehl PSF: fitting with two gaussian ditributions Halo energy >> rings energy Point = meas Line = fit Line = residual Fit with 2 gaussians Repeated considering Different IRTC crops SR Relativ error on SR Total flux estimation flux_im = (Meas image – fitted bias) Flux_im thresholded to 0 flux = total(flux_im) Line = DL Line = meas DL generation and SR meaurement IRTC field in pixels psf DL generated with nominal FWHM and the energy = flux sr_meas = max(y-R[0])/max(psf_dl) Estimation from real-time data 2 2 2 SR exp tot Marechal approximation: tot res 2 Wavefront error estimation: 2 2 fit n mod Correction residuals: res 2 2 m res i and: m res Rs i 1 ! • 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 m res Rs 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. Estimation from real-time data There is another reason that this method underestimates the WF error. The 2 factor sigma(res) only estimates the due to spatial modes whose 2 error WF 2 SR the exp tot Marechal approximation: of actuators order is less than or equal to number used. The higher order not included in the WFS slopes. modes in the residual error are tot res 2 Wavefront error estimation: 2 2 fit n mod Correction residuals: res 2 2 m res i and: m res Rs i 1 ! • 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 m res Rs Comparison 20091005_133216 MAG 8.5 ____ 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 = 84+- 8 % [FWHM on IRTC = 41 mas] 20091005_164935 FP3 MAG 10.7 ____ Acquired PSF ____ DL Psf with same flux 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 = 55 +- 7 % [FWHM on IRTC = 41 mas] 20091005_173152 FP5 MAG 12.4 ____ 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 = 45 +- 5 % [FWHM on IRTC = 42 mas]