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IRTF Adaptive Optics System Review

IRTF Adaptive Optics System Review. Overview. IRTF is building a 36 element curvature based AO system Purpose of this Review - Is to identify any remaining design, installation or operational problems and to expose the IRTF staff to the system details

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IRTF Adaptive Optics System Review

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  1. IRTF Adaptive Optics System Review

  2. Overview • IRTF is building a 36 element curvature based AO system • Purpose of this Review - Is to identify any remaining design, installation or operational problems and to expose the IRTF staff to the system details • Present Status – Design 90% complete, construction 70%

  3. Overview AO System Block Diagram

  4. AO Relay

  5. AO Wavefront Sensor(WFS)

  6. Target Science • Planetary Science • Jupiter and it’s satellites (using the satellite to guide) • Saturn and it’s satellites (using the satellite to guide) • Neptune (using the disk to guide) • Uranus (using the disk to guide) • Mars (with to-be designed wide field WFS) • Mission support • Cassini(saturn), Galileo (Jupiter), Mars Global Surveyor, • Mars 2001

  7. Non-planetary Science projects • Searches for companions to nearby stars (BDs and planets) • Astrometry of companions for second epoch confirmation • AO Spectroscopy for spectral typing R~1,000 • Large telescope follow up for Radial Velocities R~10,000 • YSO disks and companions • Imaging of disks and companions • Companion spectroscopy • Imaging (JHKL) of young star clusters • high resolution imaging for luminosity and mass functions,        disk lifetime studies • Seyfert galaxies • AO spectroscopy of nuclear regions • Quasar hosts • JHK imaging of underlying host galaxy

  8. Expected Image Quality Performance

  9. Estimated Performance (continued) Estimated Emissivity Addition of 6 mirrors – 5 Silver(1%), one Aluminum(2.2%)

  10. Estimated Performance(continued) • Sensitivity Limits • Full AO correction, average to good night, within 30 degrees • of zenith is expected to 12-13th visual magnitude • Partial AO correction out to 15th magnitude with a gradual • decrease in performance. • Tip/tilt only correction to 16th

  11. Top Level Requirements • A design that is optimized for planetary observations • Operation with NSFCAM(two plate scales) and SPEX • Optics that allow easily removing the AO optics from the beam • Support of differential track guide/science objects • A wavefront sensor field of view that allows tracking directly on Neptune and Uranus. • A wavefront sensor that bolts on the instrument and is fed via the science instrument cold dichroic • Operation optimized for J, H, K wavelengths with low enough emissivity to work at L and M. • Pass a corrected science field of 80x80 square

  12. Desirable Features • Easy changing between platescales on NSFCAM • WFS optics that allow IR wavefront sensors in the future. • Guide camera w/visible Photometry capability

  13. Optical Design IRTF AO Relay Optical Layout

  14. Optical DesignWavefront Sensor

  15. Optical Performance Relay performance ~96% Strehl over the 80 arcsecond field WFS performance ~95% on axis to ~80% in the corners at visible wavelengths Relay optics specified at Lambda/20 in the visible to reduce scatter to below the atmospheric scatter.

  16. AO Components • Dan to add

  17. AO SYSTEM NASA IRTF MECHANICAL SECTION Vern Stahlberger

  18. Mechanical Tasks: 1) RELAY 2) WAVE FRONT SENSOR 3) APD RACK MOUNT 4) SPOOL 5) AO AND SpeX (Interface) 6) AO AND NSFCAM (Interface)

  19. 1) RELAY I: DESIGN DRIVERS- A) Tolerances: Position Optical Elements to 0.001 inch Tilt Tolerance: 0.016 degrees (~ 54’) B) Must be able to assemble Relay with MIM in place C) Kinematic Mounts for Optical Elements

  20. A) Tolerances:HOW TO ACCOMPLISH! • General Rules: 1)Design for absolute positioning (no adjmts) • 2) Minimize interfaces => (more complex prts) • Limit Structure Deflection: FEA done; • shows < 0.0001 inch max. deflection • Positional accuracy: Precision machined optical • Mounts with doweled interfaces to Relay.Detail • drawings are built with tolerances to meet these • requirements. Sub-sections of Relay precision • machined and doweled. • Tilt tolerance of 0.016 degree (~ one minute) • The tolerances on the optics mounts are well • within these specifications.

  21. B) Ability to assembly above MIM ,Relay is 8ft+long OA

  22. RELAY SUB-SECTIONS

  23. C) Kinematic Mounts for Optical elements (Flat2)

  24. II: Construction: 1) Relay made up from 3 subsections; all bolted assemblies. 2) Made from Plates Alu Sup K100 (used for Stability and Flatness) 3) Weight: ~ 260 lbs 4) Overall Dimensions: 101 x 21 x 12 inches

  25. III: Relay Optical Subassemblies 1) Flat1&3Mount (6 “ translation, in-out of beam) 2) Flat2 Mount (Fixed) 3) Fiber Optics Guide (2” translation, in-out of beam) 4) OAP1 (Fixed) 5) DM (Fixed) 6) OAP2 (Fixed)

  26. Optical Elements supported by Relay Structure DM Flat2 OAP TO DEWAR OAP Flat1 Flat3

  27. Relay Optical Subassemblies DM DM mount Fold2 Mount OAP Fold1&3Mount OAP

  28. Interfaces: doweled/bolted

  29. DM-Subsection of Relay

  30. Relay: Fold1&Fold3 Assembly

  31. Relay assembled except some optics mounts

  32. 2) WAVE FRONT SENSOR I: Design Drivers- General Rules: Absolute positioning Minimize interfaces A) Positioning Tolerances for Optics: 0.001 inch B) Optics Bench: Flatness over surface <.0025 C) Assemble WFS to both NSFCAM and SpeX D) Kinematics Mounts for Optical Elements E) Light Tight Enclosure (1 bend) F) Cable Feed Through ( Fiber +)

  33. A) Positioning Tolerance:how to accomplish • Precision machined Optics Mounts: GD&T • is used for specifying important dimensions • and geometric relationships on individual detail • drawings. • Each Optics Mount is individually doweled to • the Optics Bench. Bench is toleranced to meet • specs

  34. Example of kinematic mounting

  35. Assembly Drawing for Steering Mirror: Example of Kinematic Mount

  36. B) Optics Bench: (Features) • Rigidity: Primary concern (to prevent relative platform motion) • Guaranteed flatness by Vendor < 0.0025 inch • Lightweight Structure: 47 lbs • Max. Static Deflection 0.001 inch/40lbs • load applied at center. • Dimensions: 44 1/2 x 15 x 2 inch

  37. Custom Optics Bench with Ray-trace Lenslettearray Membrane Mirror Dichroic

  38. Newport Optics Bench Design:

  39. TRUSSED CORE DESIGN:Extra Steel Member through center of cell significantly stiffens cell with little increase in weight.

  40. C) Assemble to both NSFCAM and SpeX • WFS will bolt to Vacuum Jacket of either • NSFCAM or SpeX • NSFCAM will have two focal positions: • WFS will be shifted by 2.75 inches when changing plate scales. • Note: Apd Mount will not move when • changing Plate-scales on NSFCAM. • Tie brackets are used to bolt Apd Mount and WFS together only when changing • instruments

  41. D) Kinematic Mount for Optical Elements

  42. E) Light tight Enclosure:Access covers

  43. WFS Optical Subassemblies

  44. 3) APD MOUNT I: Design Drivers- A) Cool Apd’s + Thermal Managment B) Need Access to Apd’s for Service/Replacement C) Need Wire feedthroughs for Fiber and Coax’s

  45. A) Cool Apd’s Heat dissipation per Apd = 2.6 Watts For 36 Apd’s ~ 100 W Set: In calculator- (next slide..) Apd Steady State working Temp. = 25 degrees C Fluid Stream Velocity = 1 m/s Fluid Free Stream Temp. (Dome) = 5 degrees C Fluid (Air) density=1.252 kg/m^3 Calculated: Heat Transfer Rate to Air: Q with the purchased heat sinks For 2 large heat-sinks =171.6 W + for 2 small heat sinks =85.8 W Total Q=257.4 W (Q is proportional to Area of heat sink)

  46. Heat Sinks: Two sizes

  47. Heat Transfer Rate to Air: Large sink

  48. However….

  49. Air Properties at Sea level

  50. Air Properties at 5000 m Density at 4000m

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