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

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Presentation on theme: "TMT.AOS.PRE.10.054.REL01 1 Brent Ellerbroek TMT SPIE 2010 San Diego, June 26, 2010. TMT Early Light Adaptive Optics."— Presentation transcript:

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

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 REL01 2

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 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 REL013

4 AO Requirements at Early Light (2/2) Excellent photometric and astrometric accuracy –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 REL014

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 5 TMT.AOS.PRE REL01

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

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 REL017

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

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

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

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

12 Key AO Components ComponentKey Requirements Deformable mirrors63x63 and 76x76 actuators at 5 mm spacing 10 mm stroke and 5% hysteresis at -30C Tip/tilt stage 500  rad stroke with 0.05  rad noise 20 Hz bandwidth NGS WFS detector240x240 pixels ~0.8 quantum efficiency,~1 electron at Hz LGS WFS detectors60x60 subapertures with 6x6 to 6x15 pixels each ~0.9 quantum efficiency, 3 electrons at 800 Hz Low-order IR NGS WFS detectors 1024x1024 pixels (subarray readout on ~8x8 windows) ~0.6 quantum efficiency, 3 electrons at Hz Real time controllerSolve 35k x 7k reconstruction problem at 800 Hz Sodium guidestar lasers25W, near diffraction-limited beam quality Coupling efficiency of 130 photons-m 2 /s/W/atom 12 TMT.AOS.PRE REL01

13 13 Performance Estimate Summary Error termOn-axis RMS WFE, nm Delivered wavefront error187 LGS mode error 154 First-order turbulence compensation 122 Implementation errors 95 Opto-mechanical 74 AO component and higher-order effects 59 NGS mode error 62 Contingency 86 Median Seeing with 50% sky coverage at the Galactic Pole 187 nm RMS  Strehl ratios of [ ] in [J H K] bands TMT.AOS.PRE REL01

14 14 Sky Coverage vs. Galactic Latitude and Zenith Angle

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

16 Procurement Plans AO Systems NFIRAOSNRC Canada LGSFTBD (partner or vendor) AO Executive SoftwareTBD (partner, vendor, or PO) Subsystems and Components Wavefront CorrectorsCILAS Visible WFS CCDsMIT Lincoln Laboratory Visible WFS cameras and readout electronicsTBD (partner or vendor) IR WFS detectorsTeledyne (TBC) IR WFS cameras and readout electronicsTBD (partner or vendor) Real Time ControllerTBD (partner or vendor) Guidestar laser systemsTBD (partner or vendor) TMT.AOS.PRE REL01 16 Contracts begin at or near the beginning of the TMT construction phase in October, 2011

17 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 REL01


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