Vancouver, June Models of the ground layer and free atmosphere at some sites A. Tokovinin, CTIO Need for OTP “models”: Adaptive Optics!

Vancouver, June Outline  Present MASS and DIMM  MASS “overshoots”  Free atmosphere model  SODAR and balloons  Ground layer model

Vancouver, June MASS = Multi-Aperture Scintillation Sensor  6 “layers” with triangular response  Good integrals  AO time constant  S/N~10% (better sensitivity at low turbulence) MASS database:

Vancouver, June MASS-SCIDAR: MK2002 SCIDAR MASS PASP, 2005

Vancouver, June Combine MASS with DIMM  GL

Vancouver, June MASS-DIMM instruments

Vancouver, June MASS-DIMM + Meade

Vancouver, June “Overshoots” MASS DIMM ??? Strong scintillation should be saturated? Cerro Pachon, 2003

Vancouver, June Strong scintillation

Vancouver, June Index distortion… Some over-correction for exp. time remains! …and correction S AB  S AB0 /( S AB0 ) J  J 0 /( S AB ) Semi-empirical formula

Vancouver, June “Overshoots” corrected!

Vancouver, June MASS-DIMM: CP, 2005 MASS DIMM

Vancouver, June Histograms (CP, 2005) Total Ground Free

Vancouver, June FA and GL are independent! 1” Can model FA and GL separately Same plot for MK

Vancouver, June 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 CP data overview

Vancouver, June Data for Mauna Kea (2002)

Vancouver, June OTP model: Pachon h, km GoodTyp.Bad All Integrals, m 1/3 MASS-DIMM, ” 0.75”0.91”

Vancouver, June 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 SODAR campaign at CP Goal: define the thickness of the Ground Layer Duration: Oct. 30 to Nov. 15, 2004 Equipment: XFAS from Scintec Altitude range: 40m – 800m Vertical resolution: 20m Time resolution: 20 min. Results: 505 profiles (168 hours)

Vancouver, June SODAR profiles Nov 3 Nov 4 Nov 5 Nov 6

Vancouver, June SODAR vs. MASS-DIMM (CTIO)

Vancouver, June GL model: SODAR best 25% typical worst 25% Split data in groups and average separately! C n 2 (h) = A e -h/h0 + B e -h/h1 Abahamid et al.: C n 2 (h) = A h -1.5

Vancouver, June GL model: balloons J, m 1/3 h(1/e), m Good Typical Bad profiles

Vancouver, June What is “seeing”? Seeing is the HF power of optical turbulence (J) expressed in “arcseconds” [Kolmogorov] Seeing is the HF power of optical turbulence (J) expressed in “arcseconds” [Kolmogorov]  ” = (J / 6.8x ) 3/5 Do not mix “seeing” with image quality!

Vancouver, June Atmospheric IQ at Pachon (2005) median worst 25% best 25% L 0 =25m Seeing Why do we use “seeing”? – to avoid a mess! CP site monitor Dec 2004-Apr 2005

Vancouver, June Conclusions  We know integrals in FA and GL and their variation  FA and GL are independent  Turbulence in FA: lower when stronger  Periods of calm FA: “sweet spot” for AO!  Profile models for CP: good, typical, bad  GL: exponential models