TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Brent Ellerbroek Thirty Meter Telescope Observatory Corporation Adaptive Optics for Extremely Large Telescopes Paris, June 23, 2009 Adaptive Optics Systems for the Thirty Meter Telescope

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Presentation Outline AO requirements flowdown –Top-level science-based requirements for AO at TMT –Derived requirements and design choices –First light AO architecture summary Subsystem designs –Narrow Field Infra-Red AO System (NFIRAOS) –Laser Guide Star Facility (LGSF) System performance analysis Component requirements and prototype results Lab and field tests Upgrade paths Summary

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Top-Level Requirements at First Light Derived to enable diffraction-limited imaging and spectroscopy at near IR wavelengths: Throughput > 85% from 0.8 to 2.5  m Thermal Emission< 15% of background from sky + telescope Wavefront Quality187 nm RMS on-axis* 191/208 nm RMS on a 10”/30” FoV Sky Coverage> 50 % at the Galactic Pole Photometry2% differential accuracy (10 min exposure, 30” FoV) Astrometry 50  as differential accuracy (100 sec exposure, 30” FoV) Acquisition time< 5 minutes to acquire a new field Reliability< 1% unscheduled downtime *Yields Strehl ratios of 0.41, 0.60, and 0.75 in J, H, and K bands

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Implied AO Architectural Decisions High Throughput Low Emission Minimal Surface Count; AR coatings Cooled Optical Path (-30° C) Diffraction-Limited Image Quality High Sky Coverage 10-30” Corrected FoV Very High Order AO (60x60) Tomography (6 GS) + MCAO (2 DMs) (Sodium) Laser Guide Stars MCAO to “Sharpen” NGS Large Guide Field (2’) Near IR (J+H) Tip/Tilt NGS Multiple (3) NGS to Correct Tilt Aniso.

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Technology and Design Choices (I) Utilize existing or near-term approaches whenever possible Solid state, CW, sum-frequency (or frequency doubled) lasers for bright sodium laser guidestars –Located in telescope azimuth structure with a fixed gravity vector Impact of guidestar elongation is managed by: –Laser launch from behind secondary mirror –“Polar coordinate CCD” with pixel layout matched to elongation –Noise-optimal pixel processing, updated in real time Mirror-based beam transport from lasers to launch telescope is current baseline

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Technology and Design Choices (II) Piezostack DMs for high-order wavefront correction –“Hard” piezo for large stroke, low hysteresis at low temperature –5 mm inter-actuator pitch implies a large AO system Surface count minimized to improve throughput and emissivity –Tip/tilt correction using a tip/tilt stage, not separate mirror –Field de-rotation at instrument-AO interface (no K-mirror) Tomographic wavefront reconstruction implemented using efficient algorithms and FPGA/DSP processors Tip/tilt/focus NGS WFSs located in science instruments –Baseline detector is the H2RG array

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June AO Architecture Realization Narrow Field IR AO System (NFIRAOS) –Mounted on Nasmyth Platform –Ports for 3 instruments Laser Guide Star Facility (LGSF) –Lasers located within TMT azimuth structure –Laser launch telescope mounted behind M2 –All-sky and bore-sighted cameras for aircraft safety (not shown) AO Executive Software (not shown) Lasers

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June NFIRAOS on Nasmyth Platform with Client Instruments Electronics Enclosure Nasmyth Platform Interface LGS WFS Optics Instrument Support Structure NFIRAOS Optics Enclosure Future (third) Instrument Nasmyth Platform Laser Path IRMS (and on-instrument WFS) IRIS (and on-instrument WFS)

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June NFIRAOS Science Optical Path DM0/TTS 1-1 OAP optical relay DMs located in collimated path WFS Beam- splitter Light From TMT

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June OAP2 IR Acquisition camera 2 Truth NGS WFSs 1 60x60 NGS WFS OAP1 6 60x60 LGS WFSs 63x63 DM at h=0km On tip/tilt platform (0.3m clear apeture) 76x76 DM at h=11.2km Output to science instruments and IR T/T/F WFSs Input from telescope NFIRAOS Opto-mechanical Layout AO and science calibration units not illustrated

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Laser Guide Star Facility Conservative Design Approach Approach based upon existing LGS facilities (i.e. Gemini North and South) Laser system –Initially 6 25W solid state, CW laser devices with one spare –Space for future upgrades to additional or more advanced lasers Beam transfer optics –Azimuth structure path –“Deployable” path to transfer beams to elevation structure along telescope elevation axis –Elevation structure path, including pupil relay optics and pointing/centering mirrors for misalignment compensation –Top-end beam quality, power, and alignment sensors –Optics for asterism generation, de-rotation, and fast tip/tilt correction Laser launch telescope –0.5m unobscured aperture and environmental window

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Approach to Performance Analysis Key requirement is 187 nm RMS wavefront error on-axis –50% sky coverage at Galactic pole –At zenith with median observing conditions –Delivered wavefront with all error sources included Performance estimates are based upon detailed time- domain AO simulations –Physical optics WFS modeling with LGS elongation –Telescope aberrations and AO component effects included –Actual RTC algorithms for pixel processing and tomography –“Split” tomography enables simulation of 100’s of NGS asterisms Simulated disturbances are based upon TMT site measurements, sodium LIDAR data, telescope modeling

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Examples of AO Simulation Data and Intermediate Results Atmospheric phase screen TMT aperture function M1 phase mapM1+M2+M3 on- axis phase map Sodium layer profile Input Disturbance: AO System Responses: LGS sub- aperture image Polar coordinate CCD pixel intensities DM phase maps Residual error phase map

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Example NGS Guide Field from Monte Carlo Sky Coverage Simulation Sample Asterism near 50% Sky Coverage (Besan ç on Model, Galactic Pole) Tip/Tilt NGS Tip/Tilt/Focus NGS Tip/Tilt NGS

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Performance Estimate Summary 178 nm RMS error in LGS modes –127 nm first order, 97 nm AO components, 79 nm opto- mechanical 47.4 nm tip/tilt at 50% sky coverage 63.4 nm overall error in NGS modes 187 nm RMS total at 45% sky coverage NGS Algorithm optimization and detector characterization still underway

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Sky Coverage Results for Enclosed Energy on a 4 mas Detector

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Key AO Component Technologies ComponentKey Requirements Sodium guidestar lasers 25W Coupling efficiency of 130 photons-m 2 /s/W/atom Deformable mirrors63x63 and 76x76 actuators 10  m 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 ~0.6 quantum efficiency, 5 electrons at Hz Real time control electronics/algorithms Solve 35k x 7k reconstruction problem at 800 Hz

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Laser Systems 50W+ power successfully demonstrated by a prototype Nd:YAG, sum frequency, CW laser Development of a facility class 25W design now underway at ESO, with AURA/Keck/GMT/TMT support for prototyping Sodium layer coupling of ~260 photons–m 2 /s/W/atom demonstrated, but issues remain –Magnetic field orientation, photon recoil, inaccessible ground states –coupling of ~ 70 photons-m 2 /s/W/atom predicted at ELT sites Possible solutions include combined D2a/D2b pumping and multiple (3-5) laser lines –Performance penalty is ~40 nm RMS without laser improvements

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Wavefront Correctors: Prototyping Results Prototype Tip/Tilt Stage Simulated DM Wiring included in bandwidth demonstration Low hysteresis of only 5-6% from -40° to 20° C Subscale DM with 9x9 actuators and 5 mm spacing -3dB TTS bandwidth of 107 Hz at -35C 20 Hz Req’t

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June “Polar Coordinate” CCD Array Concept for Wavefront Sensing with Elongated Laser Guidestars D = 30m  Elongation  3-4” TMT sodium layer ΔH =10km H=100km Fewer illuminated pixels reduces pixel read rates and readout noise AODP Design LLT

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Laser Guide Star (LGS) WFS Detector Requirements ParameterRequirementComments Array Geometry“Polar Coordinate”Matched to LGS elongation Number of subapertures60x60For NFIRAOS Pixels/subaperture6x6 up to 15x6205k total pixels Frame rate Readout time 800 Hz 500  sec Read noise at 800 Hz3 electronsDerived from measured planar JFET performance (CCID-56 CCD) Quantum efficiency 0.9 at  m Narrow-line optimized Now waiting to fabricate and test the 1-quadrant prototype design developed under AO Development Program (AODP) funding

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Real Time Controller (RTC): Requirements and Design Approach Perform pixel processing for LGS and NGS WFS at 800 Hz Solve a 35k x 7k wavefront control problem at 800Hz –End-to-end latency of 1000  s (strong goal of 400  s) Update algorithms in real time as conditions change Store data needed for PSF reconstruction in post- processing Using conventional approaches, memory and processing requirements would be >100 times greater than for an 8m class MCAO system Two conceptual design studies by tOSC and DRAO provide effective solutions through computationally efficient algorithms and innovative hardware implementations

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Lab Tests and Field Measurements University of Victoria Wavefront Sensor Test Bench –Tests of matched filter wavefront sensing with real time updates as sodium layer evolves University of British Columbia sodium layer LIDAR system –5W laser, 6m receiver –5m spatial resolution at 50 Hz

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Options for First Decade AO Upgrades and Systems MEMS-based MOAO in future NFIRAOS instruments –Increased sky coverage via improved NGS sharpening –Multiple MOAO-fed IFUs on a 2 arc minute FoV –Order 120x120 wavefront correctors for ~130 nm RMS WFE (with upgraded lasers, wavefront sensors, and RTC) –MEMS correct NFIRAOS residuals; simplified stroke/linearity requirements Additional AO systems for “first decade” instrumentation: –Mid-IR AO (Order 30x30 DM, 3 LGS) –MOAO (Order 64x64 MEMS, 5’ field, ~8 LGS) –ExAO (Order 128x128 MEMS, amplitude/phase correction for M1 segments, advanced IR WFS, post-coronagraph calibration WFS) –GLAO (Adaptive secondary to control ~500 wavefront modes, 4-5 LGS) Adaptive secondary mirror could be useful for all systems –Only corrector needed for GLAO and Mid-IR AO –Large-stroke “woofer” for MOAO, ExAO, and NFIRAOS+

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Summary TMT will be designed from the start to exploit AO –Facility AO is a major science requirement for the observatory An 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 Designs and performance estimates are anchored by detailed analysis and simulation Component prototyping and lab/field tests are underway Construction phase schedule leads to AO first light in 2018 Upgrade paths are defined for improved performance and new AO capabilities during the first decade of TMT

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Additional Posters and Talks PresenterTopicTime NelsonScience and top-level AO requirements0930 Tuesday HerriotNFIRAOS1640 Tuesday TravouillonTurbulence and windspeed models1040 Wednesday WangSky coverage analysis1120 Wednesday PfrommerUBC LIDAR system1410 Wednesday BoyerLaser Guide Star Facility1600 Wednesday R. ConanUVic LGS WFS Test Bench1410 Thursday LoopIRIS on-instrument WFS1430 Thursday SinquinWavefront correctors1720 Thursday GillesTomographic wavefront reconstruction0850 Friday BrowneReal-time control electronics1040 Friday HoveyReal-time control electronics1100 Friday AndersenNFIRAOS operating temperature1720 Tuesday (poster) LardierUVic LGS WFS Test Bench1800 Thursday (poster)

TMT.AOS.PRE REL01 Ellerbroek, AO4ELT, Paris, June Acknowledgements The authors gratefully acknowledge the support of the TMT partner institutions They are –the Association of Canadian Universities for Research in Astronomy (ACURA) –the California Institute of Technology –and the University of California This work was supported as well by –the Gordon and Betty Moore Foundation –the Canada Foundation for Innovation –the Ontario Ministry of Research and Innovation –the National Research Council of Canada –the Natural Sciences and Engineering Research Council of Canada –the British Columbia Knowledge Development Fund –the Association of Universities for Research in Astronomy (AURA) –and the U.S. National Science Foundation.