Vancouver, June 2005 1

Modelsof the ground layer and free atmosphere

at some sites

A. Tokovinin, CTIO

Need for OTP “models”: Adaptive Optics!

Vancouver, June 2005 2

OutlineOutline

Present MASS and DIMM MASS “overshoots” Free atmosphere model SODAR and balloons Ground layer model

Vancouver, June 2005 3

MASS = Multi-Aperture Scintillation Sensor

MASS = Multi-Aperture Scintillation Sensor

6 “layers” with triangular response

Good integrals AO time constant S/N~10% (better

sensitivity at

low turbulence)

http://www.ctio.noao.edu/~atokovin/profilerhttp://www.ctio.noao.edu/~atokovin/profiler

MASS database: http://mass.ctio.noao.edu

Vancouver, June 2005 4

MASS-SCIDAR: MK2002

MASS-SCIDAR: MK2002

SCIDAR

MASS

PASP, 2005

Vancouver, June 2005 5

Combine MASS with DIMM GL

Combine MASS with DIMM GL

Vancouver, June 2005 6

MASS-DIMM instrumentsMASS-DIMM instruments

Vancouver, June 2005 7

MASS-DIMM + Meade

MASS-DIMM + Meade

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“Overshoots”

“Overshoots”

MASS

DIM

M

???Strong scintillationshould besaturated?

Cerro Pachon, 2003

Vancouver, June 2005 9

Strong scintillation

Strong scintillation

Vancouver, June 2005 10

Index distortion…

Index distortion…

Some over-correction for exp. time remains!

…and correction

…and correction

SAB SAB0/(1 + 0.7 SAB0)SAB SAB0/(1 + 0.7 SAB0)

J J0/(1 + 0.7 SAB)J J0/(1 + 0.7 SAB)

Semi-empiricalformula

Vancouver, June 2005 11

“Overshoots” corrected!

“Overshoots” corrected!

Vancouver, June 2005 12

MASS-DIMM: CP, 2005

MASS-DIMM: CP, 2005

MASS

DIM

M

Vancouver, June 2005 13

Histograms (CP, 2005)

Histograms (CP, 2005)

Tot

al

Gro

und

Free

Vancouver, June 2005 14

FA and GL are independent!FA and GL are independent!

1”

Can model FA and GL separately

Same plot for MK

Vancouver, June 2005 15

FA: calm or turbulent?

FA: calm or turbulent?

When free atmosphere

is calm, it is stable!When free atmosphere

is calm, it is stable!

Turbulence comes in bursts

Turbulence comes in bursts

Vancouver, June 2005 16

CP data overviewCP data

overview

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Data for Mauna Kea (2002)

Data for Mauna Kea (2002)

Vancouver, June 2005 18

OTP model: Pachon

OTP model: Pachon h,

kmGood Typ. Bad

0 2.2 2.7 3.3

0.5 0.2 0.4 0.7

1 0.03 0.1 0.2

2 0.02 0.1 0.4

4 0.2 0.4 0.6

8 0.15 0.2 0.3

16 0.25 0.3 0.3

All 3.05 4.2 5.8

Integrals, 10-13 m1/3

MASS-DIMM, 2005 0.62” 0.75” 0.91”

Vancouver, June 2005 19

Testing the model

Testing the model SAM AO system:

Rayleigh LGS at 10km+ 2 t-t NGS,45 Zernike modes

SAM AO system:Rayleigh LGS at 10km+ 2 t-t NGS,45 Zernike modes

Vancouver, June 2005 20

SODAR campaign at CP

SODAR campaign at CP

Goal: define the thickness of the Ground Layer

Duration: Oct. 30 to Nov. 15, 2004Equipment: XFAS from Scintec

Altitude range: 40m – 800mVertical resolution: 20mTime resolution: 20 min.

Results: 505 profiles (168 hours)

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SODAR profilesSODAR profiles

Nov 3 Nov 4

Nov 5 Nov 6

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SODAR vs. MASS-DIMM (CTIO)SODAR vs. MASS-DIMM (CTIO)

Vancouver, June 2005 23

GL model: SODARGL model: SODAR

best 25%

typicalworst 25%

Split data in groups and average separately!

Cn2(h) = A e-h/h0 + B e-h/h1Cn

2(h) = A e-h/h0 + B e-h/h1Abahamid et al.:

Cn2(h) = A h-1.5

Vancouver, June 2005 24

GL model: balloons

GL model: balloons

J, 10-13 m1/3 h(1/e), m

Good 0.9-1.2 15-30

Typical 1.6-3 20-40

Bad 6.5-10 50-100

43 profiles

Vancouver, June 2005 25

What is “seeing”?What is

“seeing”?Seeing isthe HF powerof opticalturbulence (J)expressedin “arcseconds”[Kolmogorov]

Seeing isthe HF powerof opticalturbulence (J)expressedin “arcseconds”[Kolmogorov]

” = (J / 6.8x10-13)3/5

Do not mix “seeing” with image quality!Do not mix “seeing” with image quality!

Vancouver, June 2005 26

Atmospheric IQ at Pachon (2005)

Atmospheric IQ at Pachon (2005)

medianworst 25%

best 25%

L0 =25m

Seeing

Why do we use “seeing”? – to avoid a mess!Why do we use “seeing”? – to avoid a mess!

CP site monitorDec 2004-Apr 2005

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ConclusionsConclusions

We know integrals in FA and GL and their variationFA and GL are independentTurbulence in FA: lower when stronger Periods of calm FA: “sweet spot” for AO!Profile models for CP: good, typical, badGL: exponential models