TMT LGSF System Design Current Statuskiaa.pku.edu.cn/astroforum14/sites/default/files/TMT LGSF...

TMT LGSF System Design Current Status

Kai Wei

Institute of Optics and Electronics (IOE),CAS

1

November 4, 2014

2014/11/5

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Content

Background

30m Telescope(TMT) LGSF Cooperative Study

Laser Guide Star Facility in China

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Adaptive Optics and LGSF

Diffraction-limited Resolution

λ-wavelength，D-telescope diameter

l=0.5mm,D=10m, θ=0.01″

l=0.5mm,D=0.1m, θ=1″

D

Resolution of the optical system

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exp wRatioStrehl

Optical errors(static, dynamic) cause image degeneration

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Adaptive Optics System

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Without AO System

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Uranus

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With AO System

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The brightness of nature star is limited, so a laser beam

is launched to form a star as beacon.

Keck 72014/11/5


Rayleigh Guide Star: 10km altitude, scattering of light by the molecules atmosphere

Sodium Guide Star: 90km altitude, excitation of the sodium layer through resonant pumping of the D2a transition.

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D:/00 personal/01 Paper and Conference/Presentation/青城山_20131129/mauna_kea_heavens_timelapse_1280x720.mp4

D:/00 personal/01 Paper and Conference/Presentation/青城山_20131129/mauna_kea_heavens_timelapse_1280x720.mp4

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AO system image with LGSAO system image without LGS

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Keck LGS AO results

TMT LGSF Cooperative Study

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32 subsystems including LGSF

Laser Guide Star Facility (LGSF) Lasers mounted on elevation journal;

Laser launch telescope mounted behind M2;

Beam transfer optics (BTO) along telescope truss;


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IOE will be directly responsible for the sub-system as follows:

– The Laser System, including:

– The Lasers;

– The Laser Sequencer;

– the Laser Handling and Utilities sub-system (LHUS);

– The Beam Transfer Optics and LGSF Top End (BTO/LLT):

– The Beam Transfer Optical (BTO) ;

– Diagnostic Optical Bench system (DOB);

– Asterism Generation system (AG);

– Laser Launch Telescope (LLT);

– Acquisition Telescope (AT);

– The Laser Safety System (LSS);

132014/11/5Institute of Optics & ElectronicsChinese Academy of Sciences


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LGSF Development Route

‒ From 2010, IOE started to lead the LGSF design work;

‒ 2011.6, IOE has passed the CoDR Review, Beijing;

‒ 2012.1, IOE has passed the CoDR Follow Up Review, Beijing;

‒ 2013.5, IOE has passed Cost Estimate Review, Pasadena;

‒ 2014.2, IOE has signed the workpackage start the PD phase;

‒ 2014.9, Successful Review for 1st stage of PD phase;



– The Laser System

– The Optical Path

– The Diagnostic Optical Bench

– The Asterism Generators

– The Laser Launch Telescope

(LLT)

The LGSF consists of five major mechanical assemblies, list in order of

laser beam propagation

Six NFIRAOS

Lasers

BTO

Nasmyth

Platform

Laser System Location



EFJA

TRIFA



Acquisition

Telescope

Laser Launch

Telescope

Diagnostic

Bench

Asterism

Generator

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Baseline

OP

Along the (-XECRS, +YECRS)

diagonal column and (+YECRS)

Hexpod leg

Along the (-XECRS, +YECRS)

vertical column and the

(+XECRS, -YECRS) Hexpod leg

New

OP

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Optical performance;

– (1) Number of fold mirrors & Large Angle of Incidence (AOI)

– (2) Tolerance for Relay Lenses;

– (3) Dynamic range of moving mirrors;

– (4) Throughput.

Mechanical design;

– (1) The mounting structure of the OP duct.

– (2) Influence to the layout of the DOB and AG.

– (3) The weight, wind cross section …….

Access to LGSF components;

Interference with other observatory systems;

Wind Jitter and Thermal Turbulence.

Baseline OP New OP

Optical

Number of Fold Mirrors Total 4 Total 4

Large AOI2 mirrors, may have risk forthroughput and polarization

None

Optical Path Length ~48.3m ~43.7m

Dynamical range analysis BetterLittle larger dynamical range,but acceptable;

StructureDistance between ducts andtelescope

0.17m1.1m, the weight of thesupport structure will be littleheavier, but still fine.

AccessLGSF OP component access

TPA Walkways TPA Walkways

EJFARequiresscaffolding.

HEXFA1Shutter mountedhoist and manbasket

TRIFAShutter mountedhoist and manbasket

HEXFA2Shutter mountedhoist and manbasket

LGSF Top End & TCA Access Requires scaffolding Requires scaffolding

Interference

Interference with crane 10t crane: Issue with both duct and telescope

Interference with other sub-systems

Potential interference with theM2 lifting fixture

None

Performance Thermal turbulence baseline path is slightly worse new path is better


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Selected Optical Path

2014/11/5Institute of Optics & ElectronicsChinese Academy of Sciences 232014/11/5

TMT website:

IOE has taken the

lead for the design

of LGSF.

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1.8m Telescope experimental bench at Lijiang, first

light


LGSF in China

Star WDS BU 989, Mv 4.1, angular separation 0.245arcsec, 2009.10.21

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LGSF in China

Sodium Laser and 1.8m Telescope

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Test progress and result

Laser Parameter (Provided by TIPC)

Operation mode : Long pulsed Laser

Dimension : 1200 X 900 X 300 (Laser Head)

Pulse length : ~120us

PRF : 500Hz

Average Power : ~16W

Line Width : 0.4GHz

Polarization : >99%

Beam Quality : M2 =1.2

Without Repumping

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TIPC Sodium Laser Prototype

Laser in the Cleaning Room

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The laser launch Telescope with the cover opened

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The laser beam is launched to the sky

First light of the LGS with TIPC laser

The exposure time is 1sThe

Wavelength

near the Na D2

Line

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The Wavelength

far away from the

Na D2 Line


Test the photon returns with the middle wavelength changes‒ After the this work, we shift the wavelength to the biggest photon

return position to continue our test

Test the photon returns with Circular and Linear polarization‒ The improve

between the circular and linear is nearly 30%

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Institute of Optics & ElectronicsChinese Academy of Sciences

Conclusion and Next Step

Conclusion

During the March and April the sodium column density is at low level;

the LGS has 8.2M @19W；

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Imaging resolution of J band is better than1.7 times diffraction limit with closed loop.

Star:HIP43964,

V=8.18, 1.3um

uncorrected corrected

钠导星阵列图像

2014.1.25, finished correction in AO system with LGSF the first time in China

Capture the high resolution image of the dark star.

Contact：

Email：[email protected]

Cell ：13880961467

Thanks！

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Gemini Enclosure

TMT LGSF System Design Current Statuskiaa.pku.edu.cn/astroforum14/sites/default/files/TMT LGSF...

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