DESCRIPTION OF ATST SEEING MONITOR ATST Science Working

DESCRIPTION OF ATST SEEING MONITOR

ATST Science Working Group Meeting

Tucson, AZNovember 17, 2003

Jacques M. BeckersChair ATST Site Survey Working Group

University of Chicago

A Short History of Solar Site Testing~ 1900 Barnard compares Lick & Yerkes Observatories seeing(finds Yerkes slightly better for solar; Lick better for nighttime)

1913-1914 Evershed tests sites in Kashmir Region of India/Pakistan(finds lake sites much superior to mountain sites!)

1965-1967 Leighton, Zirin. Mosher survey of sites in S. California(resulted in Big Bear Lake selection for Caltech Solar Obs.)

1967-1979 JOSO survey of southern Europe & Canary Islands(resulted in establishment of Izaña & La Palma/ORM obs.)

~ 1987 LEST survey planned comparing Hawaii & Canary Island sites(R.B.Dunn built seeing test telescopes but survey was abandoned)

1996-1997 CLEAR site survey with Seykora scintillometer(tested BBSO, Lake Heron, La Palma, Mauna Loa and Sac Peak)

2002/03 NSO survey for Advanced Technology Solar Telescope

ATST SEEING MONITORSac Peak on top of 6 meter high“Stand” Fuxian Lake (Yunnan Province)

World’s First S-DIMMATST Prototype

FUXIAN HU

DIFFERENTIAL IMAGE MOTION MONITORTypical Nighttime DIMM ⇒

(Maidenak)

SHABAR

225 mm

Diameter45 mm

N

S

SOLAR DIMM or S-DIMM(ATST Survey)

to slit jaw monitor

slit width 2.7 ArcsecIn N-S direction on N Limb

DIFFERENTIAL IMAGE MOTION MONITORCONCEPT FIRST USED BY J. STOCK & G. KELLER FOR EARLY CHILE SITE SURVEY (resulting in Cerro Tololo Observatory)

DIFFERENTIAL IMAGE MOTIONS ARE INSENSITIVE TO TELESCOPESHAKE (WIND BUFFETING, TRACKING). ONLY SEEING GIVE SIGNAL

FIRST FULLY ELECTRONIC/DIGITAL VERSION USED IN NOAO MAUNAKEA/MOUNT GRAHAM SEEING COMPARISON & VLT SITE SURVEY(resulted choice of Mauna Kea for GEMINI and Cerro Paranal for VLT(I))

APERTURE DIAMETER D SHOULD BE < r0 (Seeing FWHM = λ/r0)

DISTANCE BETWEEN APERTURES d NORMALLY TAKEN AS 25 – 30 CM

EXPOSURE TIME SHOULD BE SHORT ENOUGH TO “FREEZE” THEIMAGE MOTIONS (for S-DIMM: 1 – 2 msec; cadence 15 Hz)

MS DIFFERENTIAL MOTION = 2*λ2*r0-5/3*(.0179*D-1/3-0.0968*d-1/3)

⇒ FRIED PARAMETER r0(500 nm)

S-DIM

M P

ANEL

CCD IMAGEOF SLITS

SHABAR =SHAdow BAnd Ranger

CONSISTS OF 6 SOLAR SCINTILLOMETERS

EACH IS SEYKORA TYPE SCINTILLOMETER

SEYKORA FOUND AT SAC PEAK THAT SOLARSCINTILLATION INDEX (σI

2) WAS CLOSELYCORRELATED WITH THE SEEING

WHY?

r0-5/3 = 0.060*λ2*cosζ* Cn

2(h)dh (:) FWHMseeing5/3

σI2 (for Sun) = 0.955x106*cos-2/3ζ* h-1/3*Cn

2(h)dh

where: ζ = Zenith DistanceCn

2(h) = Refractive Index Structure Constant

⇒ σI2/FWHM5/3 = const.* h-1/3*Cn

2(h)dh/ C 2(h)dh

Seykora

Rimmele

h+5/6

h-1/3

NOTE: SOLAR SCINTILLATION INDEX IS WAVELENGTH INDEPENDENT!

W. Livingston

CLEAR SITE SURVEYUsed Single Scintillometers

Sites Tested: Big Bear Lake,CALake Heron,NMLa Palma/ORMMauna Loa,HISac Peak,NM

“lakeshine”

SHABAR = NON-REDUNDANT LINEAR SCINTILLOMETER ARRAY◄ 6 SHABARS

being tested

Correlation of ►SHABAR pairs

SHABAR Pair Light Path

CorrelationCoefficient vs Separation

2 cm

4 cm

6 cm

16 cm 20 cm

100 cm 200 cmSHABAR

SHABA

R PA

NEL

JMB INTERPRETATION OF THE SHABAR DATA (Experimental Astronomy 12, 1, 2001)

USING RODDIER (Progress in Optics XIX, 283, 1981) I CALCULATE SPATIAL COVARIANCE FOR STARS & SUN:

STAR

h=10km

h=2.5km

SUN

h=10km

h=2.5km

h=5kmh=7.5km

NOTE: DISTANCES scale with HEIGHT

CVtheory(h,d)

O = observedX = fitted CVobs(d) = constant* CVtheory(h,d)*Cn

2(h)dh

Fitted to:

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

2(h)

⇒ A, h0 & B

CURRENT INTERPRETATION OF THE SHABAR DATADEVELOPED BY P. HICKSON, F. HILL & M. COLLADASREMOVES ASSUMTION OF Cn

2(h) MODEL

CVobs(d)constant*CVtheory(h,d)

d=12mm

d=468mm

h-1/3 curve

• NOTE:

• LS fit of selected heights Cn2

• height info only up to ~ 1 km

• one cannot distinguishbetween Cn

2(1.25 km) = A and Cn

2(10 km) = 2AS-DIMM15 curves corresponding to 15 spacings

DOUBTS ABOUT SHABAR RESULTSSHABAR INTERPRETATION IS BASED ON SOLIDPHYSICS OF ATMOSPHERIC OPTICS

TWO UNCERTAINTIES ON INPUT TO THEORY EXIST:(1) ASSUMPTION OF KOLMOGOROV TURBULENCE. MAYBE WRONG

AT h > 2 km WHERE CONE DIAMETER IS > 20 m WHICH ISCOMPARABLE TO THE OUTER SCALE OF TURBULENCE (L0) VALUESMENTIONED IN THE LITTERATURE

(2) “WIND-FILTERING” DUE TO LOWWIND VELOCITIES AT HIGHALTITUDES CAUSING SCINTILLATIONFREQUENCIES TO BE < CUT-OFFFREQUENCY OF SHABAR (0.1 Hz)

NEITHER SHOULD AFFECT LOW ALTITUDE RESULTSDOUBTS APPEAR BASED ON BASIS OF APPARENTDISAGREEMENT OF SHABAR RESULTS WITH PERCEPTIONS AND OTHER OBSERVATIONS

Wind takes 2 sec toMove across cone

FUTURE?What to do in Phase 2?

SUGGESTIONS:LOCAL SEEING VARIATIONS USING PRESENT S-DIMM/SHABARSYSTEMS (2 – 3 per site) & MOBILE SHABAR INSTRUMENTS

SUGGESTIONS:LOCAL SEEING VARIATIONS USING PRESENT S-DIMM/SHABARSYSTEMS (2 – 3 per site) & MOBILE SHABAR INSTRUMENTS

NEW “MAXI-SHABAR” WITH LARGER BASELINES TO PROBEHIGHER ATMOSPHERE (up to 20 km)

⇒ BOTH Cn2(h) AND Vwind(h) (horizontal vector)

⇒ ISOPLANATIC PATCH (Θ0) & TIME CONSTANT (☺0)

(SEE SOUTH POLE PROPOSAL)

1998 NSF PROPOSAL FOR SOUTH POLESTATIONARY SHABAR

Would Have MeasuredCn

2(h) andVwind(h) (horizontal vector)

to 10 km Height

RESUBMIT??

SUGGESTIONS:LOCAL SEEING VARIATIONS USING PRESENT S-DIMM/SHABARSYSTEMS (2 – 3 per site) & MOBILE SHABAR INSTRUMENTS

NEW “MAXI-SHABAR” WITH LARGER BASELINES TO PROBEHIGHER ATMOSPHERE (up to 20 km)

⇒ BOTH Cn2(h) AND Vwind(h) (horizontal vector)

⇒ ISOPLANATIC PATCH (Θ0) & TIME CONSTANT (☺0)

ONE SIMPLE & FAST OPTION: E-W STATIONARY LINEAR ARRAYWITH WIDE FOV (1200) SCINTILLOMETERS AND 40 TIMES LARGERSPACINGS (0.48m – 18.75m) ⇒ Cn

2(h) & perhaps Vwind(h)

SUGGESTIONS:LOCAL SEEING VARIATIONS USING PRESENT S-DIMM/SHABARSYSTEMS (2 – 3 per site) & MOBILE SHABAR INSTRUMENTS

NEW “MAXI-SHABAR” WITH LARGER BASELINES TO PROBEHIGHER ATMOSPHERE (up to 20 km)

⇒ BOTH Cn2(h) AND Vwind(h) (horizontal vector)

⇒ ISOPLANATIC PATCH (Θ0) & TIME CONSTANT (☺0)

ONE SIMPLE & FAST OPTION: E-W STATIONARY LINEAR ARRAYWITH WIDE FOV (1200) SCINTILLOMETERS AND 40 TIMES LARGERSPACINGS (0.48m – 18.75m) ⇒ Cn

2(h) & perhaps Vwind(h)

~ 40m HIGH MAST WITH MICRO-THERMAL SENSORS AND WIDE FOVSCINTILLOMETERS TO VERIFY (IF NEEDED) THE SHABAR TECHNIQUE

SUGGESTIONS:LOCAL SEEING VARIATIONS USING PRESENT S-DIMM/SHABARSYSTEMS (2 – 3 per site) & MOBILE SHABAR INSTRUMENTS

NEW “MAXI-SHABAR” WITH LARGER BASELINES TO PROBEHIGHER ATMOSPHERE (up to 20 km)

⇒ BOTH Cn2(h) AND Vwind(h) (horizontal vector)

⇒ ISOPLANATIC PATCH (Θ0) & TIME CONSTANT (☺0)

ONE SIMPLE & FAST OPTION: E-W STATIONARY LINEAR ARRAYWITH WIDE FOV (1200) SCINTILLOMETERS AND 40 TIMES LARGERSPACINGS (0.48m – 18.75m) ⇒ Cn

2(h) & perhaps Vwind(h)

~ 40m HIGH MAST WITH MICRO-THERMAL SENSORS AND WIDE FOVSCINTILLOMETERS TO VERIFY (IF NEEDED) THE SHABAR TECHNIQUE

USE 40 cm (?) DUNN-LEST TELESCOPES & CCD IMAGING?NOTE: The two telescopes are now on loan to University of Hawaii

SUGGESTIONS:LOCAL SEEING VARIATIONS USING PRESENT S-DIMM/SHABARSYSTEMS (2 – 3 per site) & MOBILE SHABAR INSTRUMENTS

NEW “MAXI-SHABAR” WITH LARGER BASELINES TO PROBEHIGHER ATMOSPHERE (up to 20 km)

⇒ BOTH Cn2(h) AND Vwind(h) (horizontal vector)

⇒ ISOPLANATIC PATCH (Θ0) & TIME CONSTANT (☺0)

ONE SIMPLE & FAST OPTION: E-W STATIONARY LINEAR ARRAYWITH WIDE FOV (1200) SCINTILLOMETERS AND 40 TIMES LARGERSPACINGS (0.48m – 18.75m) ⇒ Cn

2(h) & perhaps Vwind(h)

~ 40m HIGH MAST WITH MICRO-THERMAL SENSORS AND WIDE FOVSCINTILLOMETERS TO VERIFY (IF NEEDED) THE SHABAR TECHNIQUE

USE 40 cm (?) DUNN-LEST TELESCOPES & CCD IMAGING?NOTE: The two telescopes are now on loan to University of Hawaii

BALLOON FLIGHTS ⇒ Cn2(h); Vwind(h); T(h);etc.

THE END