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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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