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TMT LGSF System Design Current Status
Kai Wei
Institute of Optics and Electronics (IOE),CAS
1
November 4, 2014
2014/11/5
22014/11/5
Content
Background
30m Telescope(TMT) LGSF Cooperative Study
Laser Guide Star Facility in China
3
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
22
exp wRatioStrehl
Optical errors(static, dynamic) cause image degeneration
32014/11/5
4
Adaptive Optics System
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5
Without AO System
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Uranus
6
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
Adaptive Optics and LGSF
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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Adaptive Optics and LGSF
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Adaptive Optics and LGSF
AO system image with LGSAO system image without LGS
102014/11/5
Adaptive Optics and LGSF
Keck LGS AO results
TMT LGSF Cooperative Study
112014/11/5
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;
TMT LGSF Cooperative Study
122014/11/5
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
TMT LGSF Cooperative Study
142014/11/5
TMT LGSF Cooperative Study
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;
152014/11/5Institute of Optics & ElectronicsChinese Academy of Sciences
TMT LGSF Cooperative Study
– 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
162014/11/5Institute of Optics & ElectronicsChinese Academy of Sciences
TMT LGSF Cooperative Study
EFJA
TRIFA
172014/11/5Institute of Optics & ElectronicsChinese Academy of Sciences
TMT LGSF Cooperative Study
Acquisition
Telescope
Laser Launch
Telescope
Diagnostic
Bench
Asterism
Generator
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TMT LGSF Cooperative Study
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TMT LGSF Cooperative Study
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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TMT LGSF Cooperative Study
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
TMT LGSF Cooperative Study
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TMT LGSF Cooperative Study
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.
23
TMT LGSF Cooperative Study
1.8m Telescope experimental bench at Lijiang, first
light
242014/11/5Institute of Optics & ElectronicsChinese Academy of Sciences
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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Test progress and result
The laser launch Telescope with the cover opened
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Test progress and result
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Test progress and result
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
312014/11/5
The Wavelength
far away from the
Na D2 Line
Test progress and result
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%
322014/11/5
Test progress and result
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;
332014/11/5
342014/11/5
Test progress and result
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.