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The Design Improvement of TMT Laser Guide Star Facility

The Design Improvement of TMT Laser Guide Star Facility. Kai Wei Institute of Optics and Electronics (IOE),CAS. International Colloquium on Thirty-Meter Telescope Beijing, May 25 2011. Presentation Outline. Simple Description of the LGSF main Requirement

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The Design Improvement of TMT Laser Guide Star Facility

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  1. The Design Improvement of TMT Laser Guide Star Facility Kai Wei Institute of Optics and Electronics (IOE),CAS International Colloquium on Thirty-Meter Telescope Beijing, May 25 2011

  2. Presentation Outline • 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

  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;

  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;

  5. TMT.LGSF main Requirement

  6. 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 fourasterisms • Use conventional optics for the Beam Transfer Optics and launch the AO asterisms from a Laser Launch Telescope located behind the TMT secondary mirror

  7. TMT.LGSF main Requirement • 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

  8. Why we need update the LGSF conception design • 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 ~50m Beam Transfer Optics Optical Path with 110 total actuators.

  9. 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 28000 25926 23593

  10. Beam Transfer Optics Path Issues • 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. 10

  11. The updated LGSF conception design 2011 LGSF Design 2008 LGSF Design

  12. The updated LGSF conception design 2011 LGSF Design 2008 LGSF Design

  13. The updated LGSF conception design Flexure Compensation System Flexure Compensation System Side View Top View LLT 2008 LGSF Top end Design Top View Side View 2011 LGSF Top end Design

  14. LLT Optical Redesign (1/3) • 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 M1and M2 for about 50mm • Shift the pupil position nearly about 100mm Side View Side View

  15. LLT Optical Redesign (2/3) Image quality of the new LLT

  16. LLT Optical Redesign (3/3)

  17. Beam Transfer Optical Redesign (1/2) Move one mirror from the Nasmyth Platform to the LGSF Top End structure LGSF TOP End LGSF TOP End Laser System Laser System Old BTO Design New BTO Design

  18. Beam Transfer Optical Redesign (2/2) • 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 Input beam shape Output Beam shape

  19. Acquisition Telescope Optical Design(1/2) 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

  20. Acquisition Telescope Optical Design(2/2) Image quality of the Acquisition Telescope

  21. Throughput Budget of the End to End LGSF Optical System • End to end optical evaluation is in progress

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

  23. LGSF Top End Mechanical Redesign (2/6)-LLT Repackaging 1170mm 850mm Repackaging 2450mm 1040mm 710mm

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

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

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

  27. 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) ④ ② ③ ⑤ ⑥ ①

  28. LGSF BTO Mechanical Redesign (1/4)

  29. LGSF BTO Mechanical Redesign (1/4)

  30. LGSF BTO Mechanical Redesign (3/4)

  31. LGSF BTO Mechanical Redesign (4/4) • 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

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

  33. Electronics and Control (2/3)-Location of the Electronics Box Top End Electronics Box Dimension:1000x500x500 Weight:105Kg Elements in this Box • When allthe devices are running in the full mode, the supplied power must be greater than 3063w.

  34. Electronics and Control (3/3)- Location of the Electronics Box Laser platform Electronics Box Dimension:400x500x500 Weight:40Kg Elements in this Box • All the devices are running in the full mode, the supplied power must be greater than 74w.

  35. Management Plan • Conceptual Design Review at June 22 2011,Beijing • Cost Estimate of the LGSF will begin after CDR and finish in threemonths • 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 2012

  36. Management Plan • Schedule and Key milestone for this work package Cost Estimate Review Preliminary Design Review

  37. Questions Thank you! 37

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