2022.12.21, 第11回可視⾚外線観測装置技術ワークショップ2022

Shack-Hartmann光学系を⽤いた
⼤気乱流分布測定- すばる望遠鏡でのオンスカイ試験 ⼤⾦ 原 (東北⼤学, D3)
共同研究者: ⼤野良⼈2, 美濃和陽典2, 秋⼭正幸1, ⼤屋真2, 寺尾航暉2, ⾚澤拓海1, 穂満理⽣11東北⼤学, 2国⽴天⽂台

Power spectrum of atmospheric turbulence 2 /20• Kolmogorov power spectrum−3−11/3

ΦN( f ) = 9.7 × 10 | f |2
3
CN [m ]

Forssen et al. 2019
Hardy 19982C• N(h): atmospheric turbulence pro le• Site variation• Seasonal variation• Day-night variationfi• Tens-of-minutes variation

Turbulence profiling for AO w/ multiple GS 3 /20• Laser Tomographic AO (LTAO)• Multiple LGS measurement around target• Atmospheric tomography• A few, low-independent measurement• Turbulence pro le as prior-information• Ground Layer AO (GLAO)• Precise ground layer turbulence pro le forfifi

performance simulation/evaluation

Turbulence profiling project© Subaru Telescope

4 /20• Install on AG/SH module at Subaru Nasmyth-opt platform• Consist of symmetric two Shack-Hartmann wavefront sensors~700

NsOpt AG/SH module

Light from the telescope~1400
thickness~200mm, weight~100kg including baseplateGround layer profiling: SLODAR

5 /20• Slope detection and ranging (Wilson+2002)• Principle• Common measurement of 2 WFSs
• Measure spatial correlation of phase

Correlation length→ turbulence height
Correlation strength→ turbulence strength

distortion between 2 stars• Speci cation• Height resolution= subaperture size / star separation• Maximum hight= telescope size / star separationfi

Ono et al. 2016

Higher layer profiling: SH-MASS

6 /20• Shack-Hartmann multi aperturea few cm scaleh3

scintillation sensor (Ogane+2021)• Principle

Fresnel• Intensity pattern by Fresnel di raction

di raction• Measure spatial correlation ofintensityh2• Speci cation• Height resolution ~ a few km

h1h0• Minimum height ~ 0.5 km• Limitationa few cm scale• Fine (~cm) spatial sampling is needed

di raction ring
fffiffff©ekklesia.co.jp

Turbulence profiler design concept• Measurement condition• measurement SNR → larger than 5• separation of star pair → 3-5 arcmin• availability of star pair at any time
Turbulence pro ler speci cation

range
Altitudefiresolution

SH-MASS<~300m>~600m~20ma few km

fi

Altitude

SLODAR

7 /20

Optimal sub-aperture size is 2.0cm.
→ Only part of the Subaruʼs pupil is used.
1.4m x 1.4m square region
8m apertureFY2020

Turbulence profiler optical designcollimator

MLA(pupil plane)

Parameter

Design value

Note

Number of elements

66 x 66 (15 x 15) when using all the lenslet

Subaperture size

2 cm

on primary mirror

Di raction limit of subaperture

7.55 arcsec

at 600nm

Subaperture FoV

25 arcsec

Pixel sampling2.5 arcsec/pix

Number of pixels per subaperture 10 pix

To pupil camera

relay lens
WFS detector

8 /20

To focus camera

focal plane
picko mirror

Number of total pixels

660 pix (150 pix) when using all the lenslet

Frame rate

200 fps (800 fps) when reading 1k pix (256 pix)

Pixel size

6.5 um*1

Read out noise

1.6 e/pixel

RMS value, *1

QE

82%

at 589nm, *1

ffff*1: Catalog value of Hamamatsu ORCA-Flash4.0 V2

FY2020

Turbulence profiler mechanical design

Wavefront sensor:
wavefront sensing of
1.4x1.4m pupil region with
66x66 division, 3pix/spot,
25arcsec/subap, 2kx2k pixels

Pupil camera: check pupil tomatch pupil between the twoWFSs, Φ3m FoV, 2kx2k pixels

fffffi

Focus adjustment mirror:
adjust focusing of the target

9 /20

Pupil adjustment mirror pair:de ne Φ3m pupil to introduce
collimator

Focus camera: checkacquisition and focusing of thetarget, 10x10 arcsec FoV, 1kx1kpixels

Picko mirror: picko target
at 1.5-2.5 arcmin from thetelescope optical axisNov.2021-Apr.2022

Laboratory assembly• Positioning jigs to place each mechanical component• Base parts to match height of optical component• Jigs and base parts are manufactured by Subaru machine shop and Misumi

10 /20Nov.2021-Apr.2022

Laboratory alignment• Rough alignment with straight laser
and alignment cones

Focus camera• Precise alignment with detector image
WFS2

Pupil camera*metal wire on pupil for
simulating telescope spider

with Fstrai
ght

Wavefront sensor

WFS1
laser source

11 /20Jun,Nov 2022

Installation to Subaru Telescope

12 /20• Align two WFSs on
baseplate• Attach picko mirror
stages• Crane the system toinsert in front of theAG/SH layer• Align to telescope
optical axis withpositioning pins

• Fix the system withff

metal wires andstrong magnets

Test with dummy weightJun,Nov 2022

Alignment after installation(1) Pickomirror

13 /20(2) Pupil adjustment mirror pair

pro ler internal lasers

telescopetarget on

image rotator

AO188 bench• Propagate laser beams from NsOpt to NsIR
• Rotate telescope image rotator
flfffi• Check two laser spots rotate along the circle.

wavefront sensor 1

wavefront sensor 2• Observe dome at with pupil camera andwavefront sensor• Telescope spider structure is observed• Check two WFSs are observing with
common telescope aperture.

Nov. 2022

On-sky test with Subaru Telescope• November 12th, 2022 (First half night)• Object acquisition test
• object: Altair (Rmag=0.6)• Pro ling data acquisition• object: HD11727, *56And

fiFocus camera

3.35 arcmin

HD11727(Vmag=5.9)*56And(Rmag=5.0)

Pupil camera

14 /20Obtained Shack-Hartmann data
GIF animation of background-subtracted image

15 /20• 120-sec continuous image• 80Hz (800 x 800 readout)• 230Hz (512 x 512 readout)• 350Hz (256 x 256 readout)

temporal mean

selected spots

Temporal statistics of spot brightness
sub-aperture• Spot brightness de ned as central 25x25 pixels in sub-aperture• Spot brightness time series for 15x15 spots• Temporal mean/variance/covariance calculated

Preliminaryfi

16 /20Preliminary

Preliminary

Scintillation index
XYX

17 /20Var[Ii] + Var[Ij] + 2Cov[Ii, Ij]
IX
sX = Var=[ ⟨IX⟩ ](⟨Ii⟩ + ⟨Ij⟩)2IX
IY
sXY = Var−[ ⟨IX⟩ ⟨IY⟩ ]= sX + sY − 2iijone spatial
frequency

kljcombinationof two spatial
frequencies

Cov[Ii, Ik] + Cov[Ij, Ik] + Cov[Ii, Il] + Cov[Ij, Il](⟨Ii⟩ + ⟨Ij⟩)(⟨Ik⟩ + ⟨Il⟩)sX
Preliminary

Covariance up to~5-10 cm scale

Overall scaling due
to exposure timeTurbulence profile reconstruction• Pro le reconstruction by tting
model with 6-layer turbulence
between 1km and 20km above

18 /20WFS1• KnownPreliminary

Preliminary

Preliminary

Preliminary• Observed spatial frequency

pattern determined by normal/
di erential aperture• Assumption

WFS2• Kolmogorov turbulence• Weak perturbation• Fresnel propagation
fi

fi

ff

consistent btw WFS1 & WFS2!

Discussion / Future work
• SH-MASS• Calibration with CFHT MASS-DIMM measurement• SLODAR• For precise ground layer turbulence pro le• Report on the next ASJ meeting• Next engineering observationfi• Mar. 8, 2023

19 /20Summary

20 /20• Purpose: Turbulence pro le for future AO system at Subaru telescope• Prior information of atmospheric tomography in LTAO
• Performance simulation/evaluation for GLAO
• Method: Development of new turbulence pro ler• SH-MASS for high layer turbulence• SLODAR for ground layer turbulence• Result• Development of turbulence pro ler is done.
• First light on November 12, 2022 ( nally!)

fifififi• Consistent SH-MASS result between dependent two wavefront sensors