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