The Design Improvement of TMT Laser Guide Star Facility Kai Wei Institute of Optics and Electronics (IOE),CAS 1 International Colloquium on Thirty-Meter Telescope Beijing, May May 25

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 May 25

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; May 25

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; May 25

TMT.LGSF main Requirement May 25

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 May 25

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 May 25

Why we need update the LGSF conception design 8 ~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 based on NOAO’s Conceptual Design 2011 May 25

LGSF Top End Issues 9 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 May 25

10 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 May 25

The updated LGSF conception design LGSF Design 2011 LGSF Design 2011 May 25

The updated LGSF conception design LGSF Design 2011 LGSF Design 2011 May 25

The updated LGSF conception design LGSF Top end Design Flexure Compensation System LLT Side View Flexure Compensation System Top View 2011 LGSF Top end Design Side View 2011 May 25 Top View

LLT Optical Redesign (1/3) 14 Reduce the Diameter from 500mm to 400mm Change the Angular Magnification from 60 to 48 Change the Primary Mirror from hyperboloid to paraboloid Remove the two Aspheric surfaces in the system Reduce the Distance between the M1 and M2 for about 50mm Shift the pupil position nearly about 100mm Side View 2011 May 25

LLT Optical Redesign (2/3) 15 Radius of field angle (arc-sec) 90Km210Km WFESrWFESr (+y direction) (-y direction) (+x direction) (-x direction) (+y direction) (-y direction) (+x direction) (-x direction) Radius of field angle (arc-sec) 90Km210Km WFESrWFESr 150 (+y direction) (-y direction) (+x direction) (-x direction) (+y direction) (-y direction) (+x direction) (-x direction) Image quality of the new LLT 2011 May 25

LLT Optical Redesign (3/3) 16 NOAO Design(2008) M1/M2 Hyperboloid M1 Paraboloid M2 Hyperboloid M1 Paraboloid M2 Paraboloid M1HyperboloidParaboloid M2Hyperboloid Paraboloid Exit Pupil Diameter Angular Magnification 6048 Fields Φ17′ Image wavelength Both 550nm&589nm589nm Elements quantities ——Add one lens near the collimator Aspheric Surface 2None Image Quality (Gauss Beam 0 arc-second Near arc-seconds Near arc-seconds Near arc-seconds Near arc-seconds M1 parameters Radius No Data Conic coefficient No Data Off axis decenter No Data420 Aperture No Data M2 parameters Radius No Data Conic coefficient No Data Off axis decenter No Data Aperture No Data 56(±3.2mm more)43(±3.2mm more) Fabrication Tolerance for M1 Radius No Data ±10mm(AM-47.7~48.3 ) Conic coefficient No Data ±0.0002(PV error )±0.0002(PV error )* 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 )±0.002(PV error ) Focus adjustments(90Km to 210Km) No DataCollimator move 0.983mmCollimator move 0.109mm On axis image quality (Without focus adjustment) No Data0.9883— — On axis image quality (Witt focus adjustment) No Data0.9883— — Entrance Pupil Position(Distance from K-Mirror) No Data345mm368mm 2011 May 25

Beam Transfer Optical Redesign (1/2) 17 Old BTO DesignNew 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

Beam Transfer Optical Redesign (2/2) 18 Input beam shapeOutput Beam shape Three relay lenses reimage the laser output pupil to the LLT entrance pupil Left 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 pupil The line of sight wander between telescope pointing at zenith and 65 degrees is proceeded 2011 May 25

Acquisition Telescope Optical Design(1/2) 19 One lens and two mirrors, total length is about 570mm Field of the design is larger than 5 arcmins R band (556nm~696nm),Focal Length:5360mm Aperture: Φ150mm 2011 May 25

Acquisition Telescope Optical Design(2/2) 20 Radius of field angle (arc-sec)Image Quality(Sr) Band (+y direction) (-y direction) (+x direction) (-x direction) (-y direction) (+x direction) (+x direction) (-x direction) Image quality of the Acquisition Telescope 2011 May 25

Throughput Budget of the End to End LGSF Optical System 21 Level 1Level 2Level 3ElementsSurfaceSurface throughputThroughputTotal Throughput LGSF (the Requirement of the total throughput is ≥ 0.75 REQ-2-LGSF-0650)0.779 LOM (Laser System Output Mirrors) BTO0.937 EJFA (EJ Fold Pointing Array) TA (Truss Array) TRIFA (Tripod Fold Array) TCA (Truss Centering Array) TEFA (Top End Fold Array) Relay Lenses DOB0.970 QWP BS (Beam Splitter) AG0.992 Fold Mirror Fast Mirror LLT0.864 Collimator Lenses Fold Mirror K Mirror M M Window End to end optical evaluation is in progress 2011 May 25

LGSF Top End Mechanical Redesign (1/6)-DOB Repackaging 22 Old DesignNew Design Periscope21 Shutter1No Beam Splitter21 Beam TrapNo1 Dimension of the Bench1100 X X 710 Repackaging 2011 May 25

LGSF Top End Mechanical Redesign (2/6)-LLT Repackaging mm 1170mm 1040mm 850mm 710mm Repackaging 2011 May 25

LGSF Top End Mechanical Redesign (3/6)-AG Repackaging 24 Repackaging D=725mm D=625mm 17° 13.6° 2011 May 25

LGSF Top End Mechanical Redesign (4/6)-AT packaging 25 Acquisition Telescope The total length of the acquisition telescope is 736.5mm 2011 May 25

LGSF Top End Mechanical Redesign (5/6)-Support Structure 26 DOB Support TCA Support Tilt Compensation LLT Support 2011 May 25

LGSF Top End Mechanical Redesign (6/6)-Wind Section and Mass budget 27 The maximum transverse cross sectional area of the LGSF Top End is 2.74m 2 less than 4m 2 (REQ-2-LGSF-0750) The total mass of the LGSF Top End is 0.98t (REQ-2-LGSF-0900) 2011 May 25 ItemSub-systemMass/Kg 1LLT213 2AG95 3DOB331 4TCA55 5Electronics Box105 6Support structure185 7LGSF Top End total984 ① ② ③ ④ ⑤ ⑥

LGSF BTO Mechanical Redesign (1/4) May 25

LGSF BTO Mechanical Redesign (1/4) May 25

LGSF BTO Mechanical Redesign (3/4) May 25

LGSF BTO Mechanical Redesign (4/4) 31 Duct’s structure and the NFIRAOS laser position in the 3X3 array Laser Beam diameter: 5mm Mirror diameter: 50mm 3x3 pattern Separation between beams:70mm Duct diameter:270mm Duct :1mm thickness material rolled into tubular section 2011 May 25

Electronics and Control (1/3)-The topology of the LGSF May 25 The LGSF electronics elements are divided into two parts: –Top end electronic enclosureTop end electronic enclosure –Laser Platform electronic enclosureLaser Platform electronic enclosure The CPCI computer is the heart of the LGSF control LGSF TopologyCPCI Topology

Electronics and Control (2/3)-Location of the Electronics Box May 25 Top End Electronics Box Dimension:1000x500x500 Weight:105Kg Elements in this Box MechanismVolume /weight Network switch1U / 2.5kg Multi-view2U / 5kg Remote power switch1U / 3kg CPCI3U / 15kg Motion controller&amplifier8U / 40kg Fast tip/tilt controller and driver 3U /20kg(supplied by JPL,,need to be asserted.) Total18U /85.5kg When all the devices are running in the full mode, the supplied power must be greater than 3063w.

Electronics and Control (3/3)- Location of the Electronics Box May 25 Laser platform Electronics Box Dimension:400x500x500 Weight:40Kg Elements in this Box MechanismVolume /weight Motion controller2U / 5kg Motion amplifier3U / 15kg Network switch1U / 3kg Remote power switch1U / 3kg Total7U / 26kg All the devices are running in the full mode, the supplied power must be greater than 74w.

Management Plan 35 Conceptual Design Review at June ,Beijing Cost Estimate of the LGSF will begin after CDR and finish in three months Cost Estimate Review at the end of September Preliminary Design Part 1 will begin after Cost Estimate Review and finish in four month Preliminary Design Part 1 Review at the end of January May 25

Management Plan 36 Schedule and Key milestone for this work package Cost Estimate Review Preliminary Design Review 2011 May 25

Questions 37 Thank you! 2011 May 25