Defining Reference Turbulence Profiles for E-ELT AO P erformance Simulations

AO4ELT3 - Florence, May 2013

Defining Reference Turbulence Profiles for E-ELT AO Performance Simulations

M. Sarazin, J. Ascenso, M. Le Louarn, G. Lombardi, J. NavarreteESO


•AO requirements•Full Range Profilers•Surface Layer Profilers•Surface Layer and Enclosure


Cn2 profile• Has impact on 2 aspects:

– Simulation accuracy: we have to model enough layers to be representative of the “real atmosphere”

– Have to reconstruct (in the RTC) the wavefront on enough layers to maximize performance (but not make a too big RTC)

• Number of layers to model depends on the field of view and the position of the lasers. More layers for wider fields.– ~30-40 simulated layers would be needed for ATLAS(LTAO) /

MAORY (MCAO)

• To maximize performance, it seems that ~10 layers need to be reconstructed in RTC


Reconstructed Cn2 layers

9 layers reconstructed out of 26 simulated: ~ same performance as 26 reconstructed 9 enough for reconstructed.

42m case

Tomographic NGS-based AO system simulated, with on-axis optimization. Size of the NGS constellation is variable.26 simulated layers

Simulated performance stabilizes after ~25-30 layers for

LTAO


FULL RANGE CN2 PROFILERS

Used at ESO in red:•Ct2 Microthermal sensors on balloons (no SL)•SCIDAR•SLODAR•SLIDAR•MASS (no GL)•PBL (moon)


MASS –Multi Aperture Scintillation Sensor

MASS is the perfect tool for site testing to assess:•the contribution of the high atmosphere to the seeing•the short term characteristics of the turbulence•and its seasonal trends


MASS weighting function

See Kornilov, V., & Kornilov, M. 2011, Exp. Astron., 29,155

MASS algorithm response to a thin turbulent layer J=5.10-14m+1/3 real including scintillation noise in 6 layer mode (top) and in HD mode (bottom)

km


E-ELT Armazones: from LuSCI (blue) and MASS (white) profiles

E-ELT Environmental Specifications

Integrated parameters

→

Q10.18” < seeingDIMM < 0.52”

Q20.52” < seeingDIMM < 0.67”

Q30.67” < seeingDIMM < 0.88”

Q40.88” < seeingDIMM < 5.68”

Seeing = 0.45”r0 = 23.4 cmτ0 = 8.08 msθ0 = 2.59”

Seeing = 0.59”r0 = 17.8 cmτ0 = 6.12 msθ0 = 2.23”

Seeing = 0.76”r0 = 13.9 cmτ0 = 4.78 msθ0 = 2.06”

Seeing = 1.09”r0 = 9.7 cmτ0 = 3.11 msθ0 = 1.83”

h (m) ∆h (m) Wind (m/s) Cn2 (10-17 m-2/3) % of J Cn

2 (10-17 m-2/3) % of J Cn2 (10-17 m-2/3) % of J Cn

2 (10-17 m-2/3) % of J

9 2 5.5* 532.4 5.95 1004.1 7.09 1476.8 6.89 2007.2 5.14

15 10 5.5* 162.4 9.07 398.2 14.05 695.1 16.22 1119.9 14.33

25 10 5.5* 79.5 4.44 165.8 5.85 283.4 6.61 560.0 7.1735 10 5.5* 54.8 3.06 105.6 3.73 177.5 4.14 377.9 4.8445 10 5.5* 42.9 2.40 78.8 2.78 130.4 3.04 292.9 3.7555 10 5.5* 40.0 2.24 68.0 2.40 110.6 2.58 253.8 3.2565 10 5.5* 38.6 2.15 62.7 2.21 99.0 2.31 222.2 2.8475 10 5.5* 37.3 2.08 57.9 2.04 90.9 2.12 200.9 2.5785 10 5.5* 36.1 2.02 54.4 1.92 83.7 1.95 185.2 2.3795 10 5.5* 34.9 1.95 51.4 1.81 78.6 1.83 172.6 2.21

105 10 5.5* 34.0 1.90 49.1 1.73 74.2 1.73 162.0 2.07115 10 5.5* 33.4 1.86 47.2 1.67 70.9 1.66 153.9 1.97125 10 5.5* 33.0 1.84 45.8 1.61 68.2 1.59 145.6 1.86135 10 5.5* 32.2 1.80 44.7 1.58 65.6 1.53 138.6 1.77145 10 5.5* 31.5 1.76 43.6 1.54 63.8 1.49 132.7 1.70155 10 5.5* 31.3 1.75 42.5 1.50 62.0 1.45 129.1 1.65165 10 5.5* 30.9 1.73 41.3 1.46 60.0 1.40 124.5 1.59175 10 5.5* 30.4 1.70 40.2 1.42 58.3 1.36 120.2 1.54185 10 5.5* 30.0 1.68 39.6 1.40 56.7 1.32 116.6 1.49195 10 5.5* 29.5 1.65 38.8 1.37 55.5 1.29 113.0 1.45205 10 5.5* 29.9 1.67 37.9 1.34 54.2 1.26 110.2 1.41215 10 5.5* 29.4 1.64 37.6 1.33 53.2 1.24 107.5 1.38225 10 5.5* 29.6 1.66 37.6 1.33 52.1 1.22 104.0 1.33235 10 5.5* 29.7 1.66 37.0 1.31 51.5 1.20 101.9 1.30245 10 5.5* 29.9 1.67 36.7 1.30 50.4 1.18 99.2 1.27563 375 5.1 2.7 5.73 3.5 4.59 6.3 5.50 18.2 8.711125 750 6.4 0.4 1.80 0.7 1.88 1.4 2.46 3.3 3.192250 1500 9.1 0.6 4.69 1.2 6.47 2.1 7.41 3.3 6.354500 3000 16.5 0.2 3.41 0.4 3.98 0.5 3.72 0.7 2.739000 6000 24.0 0.3 9.17 0.3 7.28 0.3 4.71 0.3 2.23

18000 12000 14.9 0.2 13.87 0.2 10.06 0.3 7.56 0.3 4.56


Reconstructed Cn2 layers

Impact of split of the highest layer onto 2 independent layers (same energy per layer). Log-lin scale

T. Fusco, Private communication

6.4 arcmin1.6 arcmin3.2 arcmin


PARSCA: Paranal Seeing Campaign (1993-1994)

A. Fuchs thesis, Nice University

22 km


PARSCA: Paranal Seeing Campaign (1993)

All records from the 20 balloons launched from the foot of Paranal in March 1993are merged into a single vertical profile


PARSCA: Paranal Seeing Campaign (1993)

The single vertical profile after binning with 100m (200 layers) and 1000m (20 layers)


Comparison of balloon profiles from Paranal (red&black) to E-ELT Armazones MASS measurements (green)

Balloon vs. MASS Profiles


Comparison of balloon profiles from Paranal (red&black) to E-ELT Armazones MASS measurements (green) – Log-log scale

Balloon vs. MASS Profiles


MASS and SCIDAR agree well only in the high atmosphere

Optical turbulence profiles at Mauna Kea measured by MASS & SCIDARTokovinin et al, PASP 2005

SCIDAR vs. MASS Profiles


Paranal multi-instrument Campaign (2007)

W. Dali Ali et al, A&A 524, A73 (2010)


Proposal

Create the required number (40? TBD) of simulated layers on the basis of an Hufnagel-Valley profile while respecting the fractions given in the E-ELT environmental specifications.We need to know from which height above ground to start


SURFACE LAYER PROFILERS

•LUSCI (SHABAR) @Paranal&Armazones

•SL-SLODAR @Paranal

LUNAR SCINTILLOMETER (Poster G. Lombardi et al)

LUSCI CONSISTS OF A LINEAR ARRAY OF PHOTO-DETECTORS MEASURING THE FAST MOONLIGHT FLUCTUATIONSTHE OPTICAL TURBULENCE PROFILE IS DETERMINED BY USING MODELS OF THE TURBULENCE SPECTRUM AND OF THE LUNAR SHAPE (TOKOVININ ET AL. 2010). THE PROFILE IS RESTORED STARTING FROM FIXED PIVOT POINTS AT 3, 12, 48, 192 AND 768 M ABOVE THE INSTRUMENT.

SLOPE DETECTION AND RANGING (Poster G. Lombardi et al)

The SL-SLODAR uses an optical triangulation method observing wide separation binaries (> 100”). The profile is determined from the spatial covariance of the slope of the wavefront phase aberration at the ground for the two different paths through the atmosphere defined by a double star target (Butterley et al. 2006).Cn

2(h) for 8 layers starting from the telescope pupil are provided with a resolution Δh that varies between 6 and 16 m depending on the binary separation (θ) and its zenithal ∼ ∼distance.

ΔJ VS WIND SPEED (Poster G. Lombardi et al)

ΔJ is more significant when the wind speed is < 3 m s−1.

ΔJ = JSL-SLODAR − JLuSci simultaneous SL-SLODAR and LuSci integrals in the same range of altitudes


Surface Layer and Enclosure

Does the turbulence come inside or flows around?


Surface Layer and Enclosure

Does the turbulence comes inside or flows around?


Surface Layer and EnclosureWhat would be the image quality of the E-ELT at Paranal?


Surface Layer and EnclosureVLT-UT-SH vs. DIMM (any line of sight)

UT1-SH seeing (10m-30m) versus DIMM seeing (6m)


Surface Layer and EnclosureVLT-UT-SH & MASS-DIMM

Surface Layer (UT1-SH minus DIMM) vs. ground layer (DIMM minus MASS)


Surface Layer and EnclosureVST vs. DIMM (any line of sight)

VST-OMEGACAM seeing (10m-20m) versus DIMM seeing (6m)


Surface Layer and EnclosureVST OMEGACAM & MASS-DIMM

VST predicted image quality after removal from DIMM of surface layer estimated contribution


Work in Progress!

Thank you

Documents

Defining Reference Turbulence Profiles for E-ELT AO P erformance Simulations