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Laser Launch Telescope and Periscope

Laser Launch Telescope and Periscope. Celine d’Orgeville and Jim Catone. LLT. On-axis , behind secondary mirror Do not obstruct secondary mirror central hole when MCAO not in use  CoDR: deployable primary mirror.  PDR: PERISCOPE. LLT requirements. LLT image quality analysis for MCAO.

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Laser Launch Telescope and Periscope

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  1. Laser Launch Telescopeand Periscope Celine d’Orgeville and Jim Catone

  2. LLT • On-axis, behind secondary mirror • Do not obstruct secondary mirror central hole when MCAO not in use  CoDR: deployable primary mirror  PDR: PERISCOPE MCAO Preliminary Design Review

  3. LLT requirements MCAO Preliminary Design Review

  4. LLT image quality analysis for MCAO • LGS WFS centroiding measurement error must not increase by more than 20% (req.)/ 10% (goal) • Low order aberrations • LGS spot size increase < 10% (5%) • Defocus <0.1 wave rms • Astig <0.18 wave rms • Coma <0.1 wave rms • Trefoil <0.25 wave rms • Spherical <0.1 wave rms • High order aberrations • Decrease in SNR < 10% (5%) • High order ab. <0.06 wave rms MCAO Preliminary Design Review

  5. LLT image quality specs for MCAO All other performance being equal, this would save a 15% increase in laser powerrequirement MCAO Preliminary Design Review

  6. LLT optical design 16mm toroidal fold mirror 450mm, f=1672.3mm, 258mm off-axis parabola 10mm silica aspheric lens MCAO Preliminary Design Review

  7. Optical perf. over ±1 arcmin FoVfor a uniformly illuminated 450mm STOP MCAO Preliminary Design Review

  8. Optical perf. over ±1 arcmin FoVfor a uniformly illuminated 300mm STOP MCAO Preliminary Design Review

  9. Encircled energy over ±1.2 arcmin FoV MCAO Preliminary Design Review

  10. Gemini Telescope’sTop End Assembly Mounting Surface For the LLT Secondary Support Structure (SSS) Electronics Boxes Top End Vanes Vane Ring f/16 Top End SSS/M2 Interface Plane Secondary Mirror Module MCAO Preliminary Design Review

  11. Gemini Telescope’sSecondary Support Structure • Figures taken from drawings ICR01 and ICR02 25.0 2178.0 2348.0 2148.0 2153.0 2323.0 1084.0 ±7.0 475.0 Reference Plane 3D View of the SSS MCAO Preliminary Design Review

  12. SSS/LLT/BTOOB Alignment • First align the BTOOB to the LLT and pin • Remove the BTOOB and loosely install the LLT in the SSS • Reinstall the BTOOB on the LLT • Align the BTOOB/LLT assembly with the SSS • Remove the BTOOB and pin the LLT/SSS interface • Finally, reinstall the BTOOB Beam Transfer Optics Optical Bench Laser Launch Telescope Secondary Support Structure MCAO Preliminary Design Review

  13. LLT Top Plate Interfaces PLAN VIEW 3X LLT/BTOOB Interface Pad +Y 4X LLT/SSS Interface Pad F910.0 -X +X F500.0 2X LLT/BTOOB Alignment Pin Location 2X LLT/SSS Location Pin Access Port -Y MCAO Preliminary Design Review

  14. LLT Interface Details M12 Bolt & Washer BTO Optical Bench LLT Pilot Hole Access Port LLT Top Plate w/ M20 Stud ¼” Locating Pin 1.0 mm Raised Pads 15.0 24.0 25.0 SSS Top Plate ½” Locating Pin M12 Threaded Insert 1.0 mm Raised Pad M20 Nut & Washer 5.0 mm Thick Shim LLT/SSS Alignment LLT/BTOOB Alignment MCAO Preliminary Design Review

  15. Passive Focus Compensation Configuration • Produces a maximum error of 2.5 nm in the temperature range of 0 ± 15° 258.0 Off-Axis Distance 1 Fold Mirror Incoming Beam Exiting Beam Diverging Lens Translation Table 1682.3 1631.5 Compensation Rod Theoretical Mirror Mounting Plane DETAIL 1 MCAO Preliminary Design Review

  16. Periscope • Why ? • 168mm M2 hole to avoid narcissus effect when observing in thermal IR • M2 hole blocked by LLT, IR instrument can no longer see sky • How ? • Two-mirror periscope to divert the beam around the SSS • Mirror cover to block beam during visible observations • Oversized FoV and STOP to allow for M2 tip/tilt and decentrations and telescope flexures • Where ? • Bottom of SSS • Replace Gemini central baffle • Who ? • Gemini designs, integrates and commissions • RFP for parts for GN and GS periscopes MCAO Preliminary Design Review

  17. Periscope Optical Design Focus Target at Height of BTOOB/LLT Assembly 8M Telescope Axis a = 10°±1° PM1 Parent Mirror PM2 Parent Mirror 180mm Hole in M2 (Actual Hole is 168 mm) 3.5° to 4.5° Exclusion Angle on the Sky MCAO Preliminary Design Review

  18. Periscope Subsystem Primary Mirror Mirror Cover Assembly Primary Mirror Bracket Secondary Mirror Secondary Mirror Bracket MCAO Preliminary Design Review

  19. Periscope Location (SSS) SSS Periscope Assembly SSS Cross Bracing Top End Vane Interface MCAO Preliminary Design Review

  20. Periscope Location (M2) SSS LLT Periscope Assembly 475.0 M2 Mounting Plate 35.0 M2 Positioning Mechanism 897.0 M2 Tilt Mechanism f/16 Secondary Mirror (M2) 168 mm Optical Stop Beam Path MCAO Preliminary Design Review

  21. Periscope Mirror Mounting Secondary Bracket Flange Axis of Symmetry Spherical Mount Primary Mirror Primary Mirror Bracket 115° Offset MCAO Preliminary Design Review

  22. Periscope Mirror Cover Mirror Cover Motor Bracket Mirror Cover Motor Mirror Cover 2-Bar Linkage Aluminum Hinge Secondary Mirror Secondary Mirror Bracket MCAO Preliminary Design Review

  23. Mass Allocation Total Mass Added to the SSS 125 ±25 kg Periscope Mass 10 kg BTOOB Mass 20 kg LLT Mass 120 kg MCAO Preliminary Design Review

  24. Thursday, 5/24 0800 Welcome 0805 Project overview 0830 Science case 0930 Break 0945 System overview System modeling 1100 AO Module optics 1145 Lunch 1245 AO Module mechanics 1340 AO Module electronics 1400 Break 1415 Beam Transfer Optics 1510 Laser Launch Telescope Closed committee session 1800 Adjourn PDR Agenda MCAO Preliminary Design Review

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