1

The Design Improvement of TMT Laser Guide Star Facility

Kai WeiInstitute of Optics and Electronics (IOE),CAS

International Colloquium on Thirty-Meter TelescopeBeijing, May 25 2011

2011 May 25

2

Simple Description of the LGSF main Requirement Why we need update the LGSF conception design? The updated LGSF conception design

– Optical design– Mechanical design– Electronics and Control

Management Plan

Presentation Outline

2011 May 25

3

TMT.LGSF main Requirement

The LGSF is composed of 3 main sub-systems: – The Laser System (LAS), which includes the lasers, the Laser

Service Enclosure (LSE) and all associated electronics (TIPC);– The Beam Transfer Optics (BTO) and LGSF Top End:

– 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), which will copy the Gemini’s LSS;

2011 May 25

4

TMT.LGSF main Requirement

The LGSF is composed of 3 main sub-systems: – The Laser System (LAS), which includes the lasers, the Laser

Service Enclosure (LSE) and all associated electronics(TIPC);– The Beam Transfer Optics (BTO) and LGSF Top End:

– 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), which will copy the Gemini’s LSS;

2011 May 25

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TMT.LGSF main Requirement

2011 May 25

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TMT.LGSF main Requirement

Main System Functions– Project the early light NFIRAOS asterism– Project other asterisms as required by the AO modes – Switch rapidly between the four asterisms– Use conventional optics for the Beam Transfer Optics and launch

the AO asterisms from a Laser Launch Telescope located behind the TMT secondary mirror

2011 May 25

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Asterism generation requirement– NFIRAOS asterism: consists of 6 LGS, 5

equally spaced on a circle of radius of 35 arcsec and one additional on-axis guide star. (black)

– MIRAO asterism: consists of 3 LGS equally spaced on a circle of radius of 70 arcsec. (red)

– MOAO asterism: consists of 8 LGS, 3 equally spaced on a circle of radius of 70 arcsec and 5 equally spaced on a circle of radius of 150 arcsec. (blue)

– GLAO asterism: consists of 5 LGS, 4 equally spaced on a circle of radius of 510 arcsec and one additional on-axis guide star. (green)

switch between asterisms within 2 minutes

TMT.LGSF main Requirement

2011 May 25

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Why we need update the LGSF conception design

~50m Beam Transfer Optics Optical Path with 110 total actuators.

2006: LGSF Conceptual Design with Launch Telescope behind M2 and Laser System attached to Elevation Journal 2008: LGSF Update Work

– Redesign of LGSF Top End to compensate for telescope top end flexure

– Relocation of Laser System to azimuth structure to allow the lasers to operate in fixed gravity orientation

2010: Intensive trade study to compare center launch versus side launch

– Center Launch confirmed– Relocation of Laser System to Elevation

Journal due to progress toward smaller, lighter and more robust 20 to 25W lasers with a design compatible with a changing gravity orientation

Our work begins at 2010.11 based on NOAO’s Conceptual Design

2011 May 25

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LGSF Top End Issues

LGSF Top End:– 0.4m telescope instead of 0.5m– repackage the sub-system at the Top End structure– Launch Telescope field of view trade study(increase the FOV from 5’ to 17’)– No optical path to observe with natural guide stars for calibrations– Wind jitter goal < 27.5m(Old 2008 LGSF structure design ~ 27.82m)– New Acquisition System: independent LGS acquisition system with small telescope

2800

0

2359

3 2592

6

2011 May 25

1010

Several issues with the old path:Interference with the (-X, -Y) edge of the -X Nasmyth platform for elevation angles > 80 deg

Requires a notch in the Nasmyth platform

Interference between EJFA2 and (-X, +Y) part of the –X Nasmyth platform for elevation angles < -3 deg

Requires another notch in the Nasmyth platform

Tight clearance between Elevation Journal and Nasmyth platform edge of 350mm.

Beam Transfer Optics Path Issues

2011 May 25

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The updated LGSF conception design

2008 LGSF Design 2011 LGSF Design2011 May 25

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The updated LGSF conception design

2008 LGSF Design 2011 LGSF Design2011 May 25

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The updated LGSF conception design

2008 LGSF Top end Design

Flexure Compensation

SystemLLT

Side View Flexure Compensation

SystemTop View

2011 LGSF Top end Design

Side View

2011 May 25

Top View

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LLT Optical Redesign (1/3)

Reduce the Diameter from 500mm to 400mmChange the Angular Magnification from 60 to 48Change the Primary Mirror from hyperboloid to paraboloidRemove the two Aspheric surfaces in the systemReduce the Distance between the M1 and M2 for about 50mmShift the pupil position nearly about 100mm

Side View Side View

2011 May 25

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LLT Optical Redesign (2/3)

Radius of field angle (arc-sec)

90Km 210Km

WFE Sr WFE Sr

0 0.017 0.990 0.005 0.999

35 (+y direction)

0.017 0.989 0.007 0.998

35 (-y direction) 0.017 0.989 0.007 0.998

35 (+x direction)

0.017 0.989 0.007 0.998

35 (-x direction) 0.017 0.989 0.007 0.998

70 (+y direction)

0.018 0.987 0.011 0.996

70 (-y direction) 0.018 0.987 0.010 0.996

70 (+x direction)

0.018 0.987 0.010 0.996

70 (-x direction) 0.018 0.987 0.010 0.996

Radius of field angle (arc-sec)

90Km 210Km

WFE Sr WFE Sr

150 (+y direction)

0.021 0.982 0.019 0.985

150 (-y direction) 0.021 0.982 0.018 0.988

150 (+x direction)

0.021 0.982 0.019 0.986

150 (-x direction) 0.021 0.982 0.019 0.986

510 (+y direction)

0.039 0.942 0.045 0.923

510 (-y direction) 0.011 0.995 0.014 0.992

510 (+x direction)

0.028 0.969 0.033 0.958

510 (-x direction) 0.028 0.969 0.033 0.958

Image quality of the new LLT

2011 May 25

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LLT Optical Redesign (3/3)NOAO Design(2008)

M1/M2 Hyperboloid

M1 Paraboloid

M2 Hyperboloid

M1 Paraboloid

M2 Paraboloid

M1 Hyperboloid Paraboloid Paraboloid

M2 Hyperboloid Hyperboloid Paraboloid

Exit Pupil Diameter 500 400 400

Angular Magnification 60 48 48

Fields Φ17′ Φ17′ Φ17′Image wavelength Both 550nm&589nm 589nm 589nm

Elements quantities — — Add one lens near the collimator

Aspheric Surface 2 None None

Image Quality

(Gauss Beam

Sr@589nm)

0 arc-second Near 0.97 0.9883 0.9888

35 arc-seconds Near 0.97 0.9881 0.9758

70 arc-seconds Near 0.97 0.9875 0.9643

150 arc-seconds Near 0.97 0.9846 0.9651

510 arc-seconds 0.86 0.9558 0.5359

M1 parameters

Radius No Data 1677.19 1708.40

Conic coefficient No Data -1 -1

Off axis decenter No Data 420 420

Aperture No Data 450 460

M2 parameters

Radius No Data 213.91 155

Conic coefficient No Data -1.269 -1

Off axis decenter No Data 50.4 38.1

Aperture No Data 56(±3.2mm more) 43(±3.2mm more)

Fabrication Tolerance

for M1

Radius No Data ±10mm(AM-47.7~48.3 ) ±10mm(AM-47.7~48.3 )

Conic coefficient No Data ±0.0002(PV error 0.0068) ±0.0002(PV error 0.0083)*

Fabrication Tolerance

for M2

Radius No Data ±1.6mm(AM-47.7~48.3 ) ±1.6mm(AM-47.6~48.2)

Conic coefficient No Data ±0.004(PV error 0.0015) ±0.002(PV error 0.0093)

Focus adjustments(90Km to 210Km) No Data Collimator move 0.983mm Collimator move 0.109mm

On axis image quality (Without focus adjustment) No Data 0.9883—0.9244 0.9888—0.8339

On axis image quality (Witt focus adjustment) No Data 0.9883—0.9991 0.9888—0.9889

Entrance Pupil Position(Distance from K-Mirror) No Data 345mm 368mm

2011 May 25

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Beam Transfer Optical Redesign (1/2)

Old BTO Design New BTO Design

Laser System

LGSF TOP End

Laser System

LGSF TOP End

Move one mirror from the Nasmyth Platform to the LGSF Top End structure

2011 May 25

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Beam Transfer Optical Redesign (2/2)

Input beam shape Output Beam shape

Three relay lenses reimage the laser output pupil to the LLT entrance pupilLeft figure shows the input beam shape of the BTO which also is the laser output beam shape, right figure shows the output beam shape on the LLT entrance pupilThe line of sight wander between telescope pointing at zenith and 65 degrees is proceeded

2011 May 25

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Acquisition Telescope Optical Design(1/2)

One lens and two mirrors, total length is about 570mmField of the design is larger than 5 arcminsR band (556nm~696nm),Focal Length:5360mmAperture: Φ150mm

2011 May 25

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Acquisition Telescope Optical Design(2/2)

Radius of field angle (arc-sec) Image Quality(Sr)

@589nm @R Band

0 0.984 0.953

35 (+y direction) 0.977 0.947

35 (-y direction) 0.977 0.947

35 (+x direction) 0.977 0.947

35 (-x direction) 0.977 0.947

150 (-y direction) 0.972 0.942

150 (+x direction) 0.972 0.942

150 (+x direction) 0.972 0.942

150 (-x direction) 0.972 0.942

Image quality of the Acquisition Telescope

2011 May 25

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Throughput Budget of the End to End LGSF Optical System

Level 1 Level 2 Level 3 Elements Surface Surface throughput Throughput Total ThroughputLGSF (the Requirement of the total throughput is ≥ 0.75 REQ-2-LGSF-0650) 0.779

LOM (Laser System Output Mirrors) 1 1 0.999 0.999 0.999BTO 0.937

EJFA (EJ Fold Pointing Array) 1 1 0.999 0.999TA (Truss Array) 1 1 0.999 0.999TRIFA (Tripod Fold Array) 1 1 0.999 0.999TCA (Truss Centering Array) 1 1 0.999 0.999TEFA (Top End Fold Array) 1 1 0.999 0.999Relay Lenses 3 6 0.990 0.941

DOB 0.970QWP 1 2 0.995 0.990BS (Beam Splitter) 1 2 0.990 0.980

AG 0.992Fold Mirror 3 3 0.999 0.997Fast Mirror 1 1 0.995 0.995

LLT 0.864Collimator Lenses 2 4 0.990 0.961Fold Mirror 1 1 0.999 0.999K Mirror 3 3 0.999 0.997M2 1 1 0.980 0.980M1 1 1 0.960 0.960Window 1 2 0.980 0.960

End to end optical evaluation is in progress

2011 May 25

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LGSF Top End Mechanical Redesign (1/6)-DOB Repackaging

Old Design New Design

Periscope 2 1

Shutter 1 No

Beam Splitter 2 1

Beam Trap No 1

Dimension of the Bench 1100 X 800 1000 X 710

Repackaging

2011 May 25

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LGSF Top End Mechanical Redesign (2/6)-LLT Repackaging

2450mm

1170

mm

1040

mm

850m

m71

0mm

Repackaging

2011 May 25

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LGSF Top End Mechanical Redesign (3/6)-AG Repackaging

RepackagingD

=725

mm

D=6

25m

m17°

13.6°

2011 May 25

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LGSF Top End Mechanical Redesign (4/6)-AT packaging

Acquisition Telescope

The total length of the acquisition telescope is 736.5mm

2011 May 25

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LGSF Top End Mechanical Redesign (5/6)-Support Structure

DOBSupport

TCA Support

Tilt Compensation

LLTSupport

2011 May 25

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LGSF Top End Mechanical Redesign (6/6)-Wind Section and Mass budget

The maximum transverse cross sectional area of the LGSF Top End is 2.74m2 less than 4m2 (REQ-2-LGSF-0750)

The total mass of the LGSF Top End is 0.98t (REQ-2-LGSF-0900)

2011 May 25

Item Sub-system Mass/Kg

1 LLT 213

2 AG 95

3 DOB 331

4 TCA 55

5 Electronics Box 105

6 Support structure 185

7 LGSF Top End total 984

①

②③

④

⑤

⑥

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LGSF BTO Mechanical Redesign (1/4)

2011 May 25

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LGSF BTO Mechanical Redesign (1/4)

2011 May 25

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LGSF BTO Mechanical Redesign (3/4)

2011 May 25

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LGSF BTO Mechanical Redesign (4/4)

Duct’s structure and the NFIRAOS laser position in the 3X3 arrayLaser Beam diameter: 5mmMirror diameter: 50mm3x3 patternSeparation between beams:70mmDuct diameter:270mmDuct :1mm thickness material rolled into tubular section

2011 May 25

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Electronics and Control (1/3)-The topology of the LGSF

2011 May 25

The LGSF electronics elements are divided into two parts: – Top end electronic enclosure– Laser Platform electronic enclosure

The CPCI computer is the heart of the LGSF control

LGSF Topology CPCI Topology

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Electronics and Control (2/3)-Location of the Electronics Box

2011 May 25

Top EndElectronics BoxDimension:1000x500x500Weight:105Kg

Elements in this BoxMechanism Volume /weight

Network switch 1U / 2.5kg

Multi-view 2U / 5kg

Remote power switch 1U / 3kg

CPCI 3U / 15kg

Motion controller&amplifier 8U / 40kg

Fast tip/tilt controller and driver

3U /20kg(supplied by JPL, ,need to be asserted.)

Total 18U /85.5kg

When all the devices are running in the full mode, the supplied power must be greater than 3063w.

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Electronics and Control (3/3)- Location of the Electronics Box

2011 May 25

Laser platformElectronics BoxDimension:400x500x500Weight:40Kg

Elements in this Box

Mechanism Volume /weight

Motion controller 2U / 5kg

Motion amplifier 3U / 15kg

Network switch 1U / 3kg

Remote power switch 1U / 3kg

Total 7U / 26kgAll the devices are running in the full mode, the supplied power must be greater than 74w.

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Management Plan

Conceptual Design Review at June 22 2011,BeijingCost Estimate of the LGSF will begin after CDR and finish in three monthsCost Estimate Review at the end of SeptemberPreliminary Design Part 1 will begin after Cost Estimate Review and finish in four monthPreliminary Design Part 1 Review at the end of January 2012

2011 May 25

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Management Plan

Schedule and Key milestone for this work package

Cost EstimateReview

PreliminaryDesign Review

2011 May 25

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Questions

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Thank you!

2011 May 25