description of atst seeing monitor atst science working ...€¦ · shabar = non-redundant linear...

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


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??





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








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

description of atst seeing monitor atst science working ...€¦ · shabar = non-redundant linear...

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