C n 2 profile reconstruction with Shack-Hartmann slope and scintillation data: first on-sky results J. Voyez (1), C. Robert (1), J.-M. Conan (1), V. Michau (1), L. Mugnier (1), B. Fleury (1), E. Samain (2) in collaboration with Aziz Ziad (Nice University) (1) ONERA, The French Aerospace Lab (2) Observatoire de la Côte d’Azur

J. Voyez -- Onera – AO4ELT3 – May 29th Outline CO-SLIDAR motivation & principle On-sky results on 1.5 m telescope ELT perspectives & conclusions

J. Voyez -- Onera – AO4ELT3 – May 29th Outline CO-SLIDAR motivation & principle On-sky results on 1.5 m telescope ELT perspectives & conclusions

J. Voyez -- Onera – AO4ELT3 – May 29th Too coarse Cn2 profile in turbulence & WFAO simulations may lead to very optimistic performance effect is increased when considering very large FoV systems High resolution Cn2 site characterization campaigns are needed sub-km resolution would be nice Why high resolution Cn2 profiling ? extracted from ONERA ATLAS/MAORY AO analysis (E-ELT Phase A studies) 6 LGS WFAO on 4.3 arcmin or 2 arcmin ring 4.3 arcmin 2 arcmin see also Elena Masciadri Poster-13542

J. Voyez -- Onera – AO4ELT3 – May 29th SH data for a star at angular position α : : slope in sub aperture m : intensity in sub aperture m : temporal average of  scintillation index: CO-SLIDAR principle 1/2 : slope &! scintillation from S.-H. data Turbulent wavefront Microlenses Detector Turbulent image Optical axis Pupil plane Focal plane scintillation meas. implies few cm subapertures

J. Voyez -- Onera – AO4ELT3 – May 29th CO-SLIDAR principle 2/2 : double star triangulation d mn = θh Ground layer Altitude layer m n d mn θ star 1 star 2 Ground layer Altitude layer h Altitude d mn : separation between subapertures Autocorrelation of y-slopes Intercorrelation of y-slopes Autocorrelation of scintillation Intercorrelation of scintillation d mn = θh Altitude layer Correlation maps example: 2 layers {0, h} same strength One pixel gives auto/inter-correlation between all couples with given separation

J. Voyez -- Onera – AO4ELT3 – May 29th Direct problem and inversion The C n 2 profile is estimated by minimization of J, the maximum likelihood criterion, under positivity constraint Correlations of slopes and scintillation Convergence noise Unknown : matrix of weighting functions W Correlations of detection noise (+βJ p ) Regularization term Inverse of the convergence noise covariance matrix

J. Voyez -- Onera – AO4ELT3 – May 29th Reconstructed C n 2 profile: simulation data CO-SLIDAR takes advantage of the complementarity slope vs scintillation leading to better precision / resolution here resolution is about 500m in [0, 15km] range Voyez-SPIE2012 Dtel = 1.5 m 30x30 SH. 20’’ separation

J. Voyez -- Onera – AO4ELT3 – May 29th Outline CO-SLIDAR motivation & principle On-sky results on 1.5 m telescope ELT perspectives & conclusions

J. Voyez -- Onera – AO4ELT3 – May 29th ProMeO: profilometry with MeO telescope Site : OCA (Calern, near Nice) MeO telescope: D tel = 1.5 m, CO = 30% May 2012 observation campaign 30x30 subapertures SH (d sub = 5 cm) ANDOR 1K x 1K EMCCD 2 nights of observations MeO telescope The bench

J. Voyez -- Onera – AO4ELT3 – May 29th Shack-Hartmann image samples STF1744: Binary star with sep 14.4’’, mag: 2.23 and 3.88 Temporal average of short exposures Short exposure: t exp = 3 ms 14.4’’ = 517 nm ;  = 100 nm ; ~260 & 60 ph/subap/frame

J. Voyez -- Onera – AO4ELT3 – May 29th Preliminary data reduction: STF ms 15 radial orders reconstructed r 0 is estimated on measurements excluding orders 1 and 2 L 0 is difficult to estimate, of the order of 10 or 27 m, depending on the data set  We find good agreement with Kolmogorov turbulence, with outer scale effect

J. Voyez -- Onera – AO4ELT3 – May 29th Preliminary data reduction: STF ms The intensity distribution is very close to expected log-normal distribution σ 2 χ << 0.3  We are in the weak perturbation regime

J. Voyez -- Onera – AO4ELT3 – May 29th Correlation maps: STF ms Autocorrelation of x-slopes Autocorrelation of y-slopes Autocorrelation of scintillation Intercorrelation of x-slopes Intercorrelation of y-slopes Intercorrelation of scintillation Turbulent signal !

J. Voyez -- Onera – AO4ELT3 – May 29th C n 2 profile restoration assumption : L 0 = 27 m (median L 0 at Calern, see R. Conan PhD thesis) Sequences of 1000 images at ~ 15 Hz, duration ~ 1 min Sub-aperture diameter : d sub = 5 cm Binary separation: θ = 14.4’’ Zenith angle: ζ = 35° Altitude range and resolution from simple geometrical consideration: Altitude resolution : here: δh ~ 600 m Maximum altitude: here: H max ~ 17 km

J. Voyez -- Onera – AO4ELT3 – May 29th CO-SLIDAR C n 2 profiles & comparison with SLODAR / SCIDAR good agreement between CO-SLIDAR & low altitude but overestimation of medium altitude SCIDAR reconstruction more questionable discarding xentral autocorrelation point affected by of detection noise bias

J. Voyez -- Onera – AO4ELT3 – May 29th CO-SLIDAR C n 2 profiles & comparison with SLODAR / SCIDAR with estimation and subtraction of the detection noise bias on scintillation variance better agreement between CO-SLIDAR & SCIDAR central point of the scintillation autocorrellation has its importance for global normalisation

J. Voyez -- Onera – AO4ELT3 – May 29th CO-SLIDAR C n 2 profiles: regularization smoother profile (more realistic ?) We plan a comparison with free atmosphere Cn2 deduced from meteorological reanalysis [see Hach(...)Ziad et al. MNRAS2011]

J. Voyez -- Onera – AO4ELT3 – May 29th Outline CO-SLIDAR motivation & principle On-sky results on 1.5 m telescope ELT perspectives & conclusions

J. Voyez -- Onera – AO4ELT3 – May 29th CO-SLIDAR in the C n 2 profiler & ELT landscape CO-SLIDAR on meter class telescope provides high resolution Cn2 profiles site characterization to obtain relevant inputs for WFAO design and performance evaluation data to help optical turbulence forecast [see E. Masciadri earlier talk ] Joint use of slopes & scintillation should lead to more robust profile restoration, with better resolution over whole altitude range compared to SLODAR or SCIDAR instruments Of course inter-comparison campaigns are needed (SLODAR, genSCIDAR, PBL...) [see E. Masciadri Poster-13542, A. Ziad Poster on PBL] WFAO ELT instruments will include multiWFS hence super-SLODAR capacities: should not need external measurements for control optimisation (also true for wind profiling?) use of Cn2 profile for LQG control WFAO : see Gaetano Sivo Friday talk first on-sky validation on Canary

J. Voyez -- Onera – AO4ELT3 – May 29th Conclusions and perspectives A CO-SLIDAR profiler has been set up on a 1.5 m telescope C n 2 profiles have been restored from both slopes & scintillation correlations Other observation campaigns are needed in order to calibrate and compare CO-SLIDAR with other Cn2 profilers IR CO-SLIDAR ground-ground experiment conducted in fall 2012 (ONERA with French labs LTHE-INRA-CESBIO) 4µm ; 3 km range ; 21 days of SH data with SCIDAR and temperature probes data processing in progress

J. Voyez -- Onera – AO4ELT3 – May 29th CO-SLIDAR principle 2/2 : double star triangulation Correlations of slopes: sensitivity to near ground layers Correlations of scintillation indexes: better sensitivity to high altitude layers We take advantage of both kind of correlations to retrieve the C n 2 profile COupled SLope and scIntillation Detection And Ranging d mn θ m n Altitude of maximum sensitivity d mn = θh Altitude h double star assumed to be resolved by subaperture

J. Voyez -- Onera – AO4ELT3 – May 29th C n 2 profiles: effect of outer scale L 0