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TMT Early Light Adaptive Optics

TMT Early Light Adaptive Optics. Brent Ellerbroek TMT Instrumentation @ SPIE 2010 San Diego, June 26, 2010. Presentation Outline. Adaptive optics (AO) requirements summary Derived AO architecture Principal AO subsystems Narrow Field IR AO System (NFIRAOS) Laser Guide Star Facility (LGSF)

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TMT Early Light Adaptive Optics

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  1. TMT Early Light Adaptive Optics Brent Ellerbroek TMT Instrumentation @ SPIE 2010 San Diego, June 26, 2010. TMT.AOS.PRE.10.054.REL01

  2. Presentation Outline • Adaptive optics (AO) requirements summary • Derived AO architecture • Principal AO subsystems • Narrow Field IR AO System (NFIRAOS) • Laser Guide Star Facility (LGSF) • Key components • Estimated system performance • Schedule and procurement plans • Summary TMT.AOS.PRE.10.054.REL01

  3. AO Requirements at Early Light (1/2) • High throughput in J, H, K, and I bands, with low emission • Minimize optical surface count • Cooled (-30C) optical system • Diffraction-limited near IR image quality over a “narrow” field-of-view of 10-30 arc seconds • Order 60x60 wavefront compensation • Multi-conjugate AO (MCAO) with 6 guide stars and 2 deformable mirrors (DMs) • 50% sky coverage at the galactic pole • Laser guide star (LGS) wavefront sensing • Low order (tip/tilt/focus) natural guide star (NGS) wavefront sensing in the near IR with a 2 arc min patrol field TMT.AOS.PRE.10.052.REL01

  4. AO Requirements at Early Light (2/2) • Excellent photometric and astrometricaccuracy • Well characterized and stable point spread function • Telemetry for PSF reconstruction • Three low-order NGS WFS for tilt anisoplanatism compensation • High observing efficiency • Automated, reliable system • Low downtime and nightime calibration • Available at first light with low risk and acceptable cost • Utilizing existing/near-term AO technologies • Design AO into TMT from the start TMT.AOS.PRE.10.052.REL01

  5. Derived AO System Architecture • Narrow Field IR AO System (NFIRAOS) • Mounted on Nasmyth Platform • Interfaces for 3 instruments • 4-OAP, distortion free design • Laser Guide Star Facility (LGSF) • Laser launch telescope mounted behind M2 • Lasers mounted on TMT elevation journal • All-sky and bore-sighted cameras for aircraft safety (not shown) • AO Executive Software TMT.AOS.PRE.10.054.REL01

  6. “Split Tomography” Wavefront Control Architecture LGSF T/T Laser Pointing NFIRAOS NFIRAOS RTC Gradient Estimation 6 LGS WFS LGS Wave-front Recon. Higher-order wavefront modes NFIRAOS 2 DMs DM and TT Control S Reference processing TTP Science Instrument Tip/Tilt and Plate Scale (Tilt Aniso-planatism) Modes Focus 3 NGS OIWFS Gradient Estimation NGS Modal Recon. TMT.AOS.PRE.10.052.REL01

  7. AO Component Technology Choices • Laser Guide Star Facility (LGSF) • Continuous wave (CW) sum frequency or Raman fiber laser • Conventional optics (not fiber-based) beam transport • Narrow Field IR AO System (NFIRAOS) • Piezostack actuator deformable mirrors and tip/tilt stage • “Polar coordinate” CCD array for the LGS WFS • HgCdTe CMOS array for the IR low order NGS WFS • Computationally efficient real-time control algorithms implemented on DSP and FPGA hardware TMT.AOS.PRE.10.052.REL01

  8. NFIRAOS Dimensions (10.35x7.93x4.41m) and Plan View of Nasmyth Platform • Instruments • NFIRAOS Electronics • M1 • Science Calibrator TMT.AOS.PRE.10.054.REL01

  9. Cooled Enclosure with Calibration Unit, 3 Instruments, and Support Structure • Thermal enclosure • - 30° C • NSCU • NFIRAOS Science Calibration Unit • Telescope Beam • Instrument Rotator • Light Gray Trusses supplied by Instruments TMT.AOS.PRE.10.054.REL01

  10. Light From TMT • Entrance Windows • Output Focus • OAP 3 • Telescope Focus • OAP 4 • DM11 • Instrument Selection Fold Mirror • Off-axis Paraboloid (OAP) 1 • Beam splitter • Output Focus • DM0 on Tip/Tilt Stage • OAP 2 NFIRAOS Science Optical Path 4-OAP design provides excellent image quality and nulls distortion All science optics lie in a horizontal plane Dimensions driven by f/15 optical design and 0.30m pupil size at deformable mirror TMT.AOS.PRE.10.054.REL01

  11. New Top-Level LGSF Architecture • Laser launch location (0.4m launch telescope, asterism generator, and diagnostics bench) • Laser Location on Inside face of elevation journal • Feasible with new, smaller, gravity-invariant, low-maintenance lasers • Beam transfer optics path • Laser location (behind elevation journal) TMT.AOS.PRE.10.054.REL01

  12. Key AO Components TMT.AOS.PRE.10.054.REL01

  13. Performance Estimate Summary Median Seeing with 50% sky coverage at the Galactic Pole 187 nm RMS  Strehl ratios of [0.41 0.60 0.75] in [J H K] bands TMT.AOS.PRE.10.054.REL01

  14. Sky Coverage vs. Galactic Latitude and Zenith Angle

  15. AO Schedule Overview Unit 2 Unit 1 RTC DM12 DM0+TTS FAT Complete 7/18/17 DMs/TTS 11/19/14 2/12/16 3/19/15 WFS Cams 5/31/16 1/9/15 NFIRAOS FDR 12/9/13 Integration Review 3/24/15 Ready for on-Sky Tests 8/24/18 3/9/18 TMTSITE 1/26/16 1st Light Complete 12/22/18 4/27/18 Unit 1 Lasers Units 2-7 12/23/13 LGSF FAT Complete 5/22/17 FDR 12/9/13 TMT.AOS.PRE.10.054.REL01

  16. Procurement Plans Contracts begin at or near the beginning of the TMT construction phase in October, 2011 TMT.AOS.PRE.10.054.REL01

  17. Summary • TMT has been designed from the start to exploit AO • Facility AO is a major science requirement for the observatory • The overall AO architecture and subsystem requirements have been derived from the AO science requirements • Builds on demonstrated concepts and technologies, with low risk and acceptable cost • AO subsystem designs have been developed • Analysis/simulation confirm the designs meet requirements • Component prototyping and lab/field tests are underway • Construction phase schedule leads to AO first light in 2018 • Most subsystem and component procurement contracts schedule to begin in late 2011 TMT.AOS.PRE.10.054.REL01

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