The TMT Adaptive Optics Programao4elt2.lesia.obspm.fr/sites/ao4elt2/IMG/pdf/ao4elt2_ellerbroek.pdf · TMT.AOS.PRE.11.123.REL01 AO4ELT, Victoria, September 26 2011 2 ! First light

The TMT Adaptive Optics Program Brent Ellerbroeka, Sean Adkinsb, David Andersenc, Jenny Atwoodc, Arnaud Bastardd, Yong Boe, Marc-

André Boucherc, Corinne Boyera, Peter Byrnesc, Kris Caputac, Shanqiu Chenf, Carlos Correiac, Raphael Coustyd, Joeleff Fitzsimmonsc ,Luc Gillesa, James Gregoryg, Glen Herriotc, Paul Hicksonh, Alexis Hillc,

John Pazderc, Hubert Pagesd, Thomas Pfrommerh, Vladimir Reshetovc, Scott Robertsc, Jean-Christophe Sinquing, Matthias Schoeckc, Malcolm Smithc, Jean-Pierre Veranc, Lianqi Wanga, Kai Weif, and Ivan

Weversc

aTMT Observatory Corporation, bW. M. Keck Observatory, cHerzberg Institute of Astrophysics, dCILAS, eTechnical

Institute of Physics and Chemistry, fInstitute of Optics and Electronics, gMIT Lincoln Laboratory, hUniversity of British Columbia

Adaptive Optics for Extremely Large Telescopes

Victoria, Canada September 26, 2011

TMT.AOS.PRE.11.123.REL01

AO4ELT, Victoria, September 26 2011 1

TMT.AOS.PRE.11.123.REL01 AO4ELT, Victoria, September 26 2011

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! First light requirements for adaptive optics (AO) at TMT ! Derived architecture and technology choices ! System overview; major changes since 2009 ! Subsystem design tradeoffs and progress

–  Narrow Field IR AO System (NFIRAOS) –  Laser Guide Star Facility (LGSF)

! AO component development ! Modeling and system performance analysis ! Further “First Decade” AO systems and upgrades ! Summary

Presentation Outline


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! High throughput (85% in J, H, K, and I bands) ! Low thermal emission (15% of sky + telescope) ! Diffraction-limited near IR image quality

–  [187, 191, 208] nm wavefront error over a [0,10,30] arc sec field

! High sky coverage (50% at galactic pole) ! High photometric accuracy

–  2% over 30 arc sec at λ=1 µm for a 10 minute observation

! High astrometric accuracy –  50 µas over 30 arc sec in H band for a 100 second observation

! High observing efficiency ! Available at first light with low risk at acceptable cost

AO Requirements at TMT Early Light


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Derived Architectural Decisions

! Cooled (-30C) optical system –  for required emission

! High order (60x60) wavefront compensation –  for required wavefront quality

! Multi-conjugate AO (MCAO) with 6 guide stars and 2 deformable mirrors –  for required fields-of-view and astrometric/photometric accuracy

! Laser guide star (LGS) AO –  for sky coverage

! Tip/tilt and tip/tilt/focus NGS wavefront sensing in the near IR with a 2 arc min patrol field –  for sky coverage

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! Sum-frequency Nd:YAG or frequency-doubled Raman fiber laser systems

! Lasers mounted on telescope elevation journal

! Conventional beam transfer optics (mirrors)

! Center-launch beam projection

TMT First Light AO: Laser Guide Star Facility (LGSF)


TMT First Light AO: Narrow Field IR AO System (NFIRAOS)

! Mounted on Nasmyth Platform

! Interfaces for 3 client instruments

! Piezostack deformable mirrors and tip/tilt stage

! “Polar coordinate” CCD array for the LGS WFS

! HgCdTe CMOS arrays for low order, NGS, infra-red WFSs (in client instruments)


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TMT First Light AO: Real Time Control (RTC) System Features

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! “Hard” real time processes: –  WFS pixel processing (matched

filtering) –  Atmospheric tomography

! “Split” NGS/LGS formulation ! Minimal variance, pseudo

open-loop ! Computationally efficient

–  DM fitting –  Temporal filtering

! Background tasks –  Matched filter updating –  Cn2 estimation (SLODAR) –  Offload to M1, M2 –  WFS telemetry for PSF

reconstruction TMT.AOS.PRE.11.123.REL01 AO4ELT, Victoria, September 26 2011

Project Participants


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CILAS, Orleans (Wavefront Correctors)

TOPTICA, Munich (Laser Systems)

TIPC, Beijing (Laser Systems)

IOE, Chengdu (Laser Guide Star Facility)

TMT, Pasadena (Management, SE)

Keck Observatory, Waimea (WFS readout electronics)

tOSC, Anaheim (RTC)

DRAO, Penticton (RTC)

MIT/LL, Lexington (WFS CCDs)

UBC, Vancouver (Sodium LIDAR)

HIA, Victoria (NFIRAOS)

! New NFIRAOS opto-mechanical design eliminates field distortion

! LGSF architecture review –  Center- vs. side-launch trade study –  New laser location for new smaller, lighter, gravity invariant designs

! AO component design and prototyping –  Laser systems –  Deformable mirrors (and DM electronics) –  CCDs (and electronics) for LGS and visible NGS wavefront sensors –  IR HgCdTe detectors for low order, IR NGS wavefront sensors

! AO system models and performance estimates ! Concept development and performance estimates for “First Decade”

AO system options


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What’s Happened Since 2009?

Field Distortion and NFIRAOS

! 2009 NFIRAOS optical design was a off-axis parabola (OAP) relay

–  Good image quality –  0.4 arc sec distortion at edge of field

! Distortion rotated with field at final science instrument focal plane

–  Unacceptable for astrometry and multi-object spectroscopy

! Several re-design options were considered:

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OAP

DM at h=0 km on tip/ tilt platform

DM at h=11.2 km

From telescope

OAP

Output foci


Image derotator at NFIRAOS input additional surfaces; congested input focus 4-mirror anastigmat optical design large aspherics; difficult packaging Dual optical relay with 4 OAPs additional surfaces; larger mass & volume Symmetric, refractive optical design chromatic aberrations; not seriously studied

11 TMT.AOS.PRE.11.123.REL01 AO4ELT, Victoria, September 26 2011

Original (Left) and Updated (Right) NFIRAOS Optics (Common Scale)

Output focus

DM0 and TTS

Input focus

DM 11.2

DM 11.2

DM0 and TTS OAP

OAP

OAP

OAP

OAP

OAP

NFIRAOS Simplified Block Diagram (LGS Mode)


Truth WFS

LGS Zoom

6 LGS WFS

On Inst. WFS(s)

NGS WFS

RTC RTC

Param. Gen.

OAP OAP OAP OAP

OAP

OAP

DM11 DM0 + TTS

SCI BS

LGS BS

Flip mirror for NGS mode

field selection mirrors

NGS Grads

LGS Grads

LGS Off-Sets

Telescope offloads WFS/DM

telemetry (PSF recon)

Reconstruction params.

DM/WFS Statistics

Inst. Fold NGS(s)

6 LGS

Sci. Obj.

Actuator commands Source

sims.

Phase screen

To Sci. Instrument

To zoom

LGS Zoom

6 LGS WFS

Inst. Fold

Source sims.

Phase screen Simplifications

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LGSF Circa 2009

! Laser System within telescope azimuth structure

– For large lasers requiring a fixed gravity vector, frequent alignment and maintenance

! LLT behind M2 – Minimizes LGS elongation;

was also thought to minimize wavefront error due to noise

! Mirror-based beam transport between the lasers and the LLT

Lasers


LGSF Redesign Options Considered

! Center launch, with lasers mounted in elevation structure –  No need to transfer beams from azimuth to elevation structure –  Reduced overall path length –  Feasible with new lighter, smaller, gravity-invariant laser systems

! …vs. Side-launch, with lasers mounted in M1 “cell” –  Modest (~20 nm RMS) performance advantage for equal LGS signal –  Simplified beam transport, at expense of multiple LLTs –  Tighter laser packaging; larger, rotating LGS elongation on WFSs

! Various LLT simplifications also implemented, independent of above trades –  0.4m diameter; no imaging of stars for alignment; new reflective and

refractive design options

! LGS acquisition sensor added 14 TMT.AOS.PRE.11.123.REL01

AO4ELT, Victoria, September 26 2011

Updated LGSF Layout

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Laser launch location

Laser location

Beam transfer optics path

Asterism Generator

Diagnostics Bench

Launch Telescope

Acquisition Sensor

• Largest var-iations ~20nm RMS for ex-pected WFS noise levels

AO Performance Estimates: Side versus Center Launch

LGS Fratricide Modeling

! Four atmospheric effects studied –  Rayleigh backscatter causes

“fratricide” –  Remaining effects will degrade

LGS signal level

! Combined error budget allocation

Effects Backscatter Optical Depth

Rayleigh Strong 0.04 Ozone Weak 0.03 Aerosol Weak 0.02 Cirrus Weak <0.22

Cn2 Profile 25% MK13N 50% MK13N Zenith angle (deg) 0 30 45 60 0 30 45 60

RMS WFE, nm 20.32 19.03 16.91 28.85 22.64 22.50 19.96 38.64

AO Component Requirement Summary

Deformable mirrors 63x63 and 76x76 actuators at 5 mm spacing 10 µm stroke and 5% hysteresis at -30C

Tip/tilt stage 500 µrad stroke with 0.05 µrad noise 20 Hz bandwidth

NGS WFS detector 240x240 pixels ~0.8 quantum efficiency,~1 electron at 10-800 Hz

LGS WFS detectors

60x60 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 10-200 Hz

Real time controller Solve 35k x 7k reconstruction problem at 800 Hz

Sodium guidestar lasers

25W (20W with backpumping), M2 < 1.17 Coupling efficiency of 130 photons-m2/s/W/atom

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Component Development Highlights Since 2009

! Deformable mirrors (CILAS) –  Final design of NFIRAOS DMs –  6x60 subscale prototype in progress

! Visible WFS detectors (Keck and MIT/LL) –  Prototype wafer run of LGS and NGS WFS CCDs completed –  Frontside testing of packaged devices in progress

! IR NGS WFS detector arrays (Teledyne and Caltech) –  Read noise tests of H2RG detector –  <3 noise electrons at required rates with correlated multiple sampling

! Guidestar laser systems

–  TOPTICA Raman Fiber laser design and prototyping with ESO, Keck –  TIPC Nd:YAG SFG laser design, prototyping, and on-sky tests

! Development of WFS readout electronics (Keck) and DM drive electronics (HIA) also progressing


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NFIRAOS Deformable Mirrors

! Prototyping and design contract now underway at CILAS: –  Develop Final DM Designs for

NFIRAOS –  Fabricate and test 6x60 DM

breadboard –  Qualify new piezo material

source –  Validate FEA models for thermal

effects –  (Re)Validate actuator electrical

contacting –  Confirm long-term facesheet

stability –  Integrated testing with DM drive

electronics at HIA to follow 20

DM 6x60 breadboard

FEA model of thermal effects in DM0

DM0 Assembly Drawing

DM11.2 Baseplate Mode



“Polar Coordinate” CCD Array Concept for Wavefront Sensing with Elongated LGS

D = 30m è Elongation ≈ 3-4”

TMT

sodium layer ΔH =10km

H=100km

Fewer illuminated pixels reduces pixel read rates and readout noise

AODP Design

LLT

NFIRAOS Visible Wavefront Sensor Detector Prototyping

! Prototype wafer fab run completed(!) –  30x30 subaperture quadrant of

polar coordinate LGS WFS CCD –  2562 visible NGS WFS CCD

! Good functional results in wafer-level probing

! Polar coordinate devices now diced, packaged, and ready for testing

CCID-74 (2562)

Image of the front side of a finished wafer

CCID-61 Polar Coordinate

Detector Prototype

Frontside Device

Frontside Package


Laser System Development

! TOPTICA/MPB –  Keck/TMT involvement in ESO contract

for VLT 4LGSF laser system

! TIPC –  2010-11 design/prototyping study –  20W field test prototype laser

tested on the sky (8.7 mag. LGS) –  Further testING planned in 2012 at

Univ. British Columbia LZT Lidar


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Toptica/MPB Raman Fiber Laser

TIPC Nd:YAG SFG Laser On-sky TIPC tests in Yunnan

Principal AO Simulation Tools

! End-to-end time domain simulation code –  Measured sodium layer profiles –  Von Karman, multilayer turbulence with “frozen flow” –  Telescope optics figure/alignment errors + tip/tilt jitter –  Physical optics modeling for LGS beacons, LGS/NGS WFS spots, and

science PSFs –  Faithful implementation of “hard” RTC processes –  GPU implementation; 100-1 ratio between wall clock and NFIRAOS

time ! Simulation postprocessor for sky coverage analysis

–  One history of higher-order wavefront correction “replayed” for multiple NGS asterisms, since higher-order correction decoupled from NGS loop

–  Sky coverage statistics generated using 500+ random NGS asterisms ! Supplementary models/codes for individual studies


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Sample Simulation Studies Since 2009

! AO Error budget maintenance: RMS wavefront error and sky coverage ! Subsystem and component trade studies

–  LGS WFS issues: Center- vs. side-launch; fratricide; LGS spot size; meteors –  DM issues: stroke, flatness, and failed actuator impact –  TMT optics: Mirror OPDs, M1 actuators/sensors; input pupil misalignment –  NFIRAOS optics: Off-axis aberrations; NCPA; LGS WFS pupil distortion –  Vibration issues: M2/M3 tracking, tip/tilt stage power dissipation

! RTC algorithms –  “Hard” real-time: WFS pixel processing; tomography; DM fitting; Kalman

filtering –  Background tasks: SLODAR; PSF reconstruction

! PSF modeling for science simulations –  Galactic center PSF uniformity and image distortion; slit throughput


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Top-Level AO Performance Estimate

Error term On-axis RMS WFE, nm

Overall on-axis wavefront error 187

LGS mode error 157

First-order turbulence compensation 126

Implementation errors 93

Opto-mechanical 75

AO component and higher-order effects 56

NGS mode error 52

Contingency 88

•  Median Seeing, 50% sky coverage at the Galactic Pole •  Estimate stable since 2009


Estimated Sky Coverage with Median Seeing


Galactic Longitude (deg)

Gal

actic

Lon

gitu

de (d

eg)

Prob(WFE < 191 nm) for Hour Angle = 0 ! Prob. > 75% at north galactic pole

! Prob. ~ 100% below 30 degrees galactic latitude

Options for Additional “First Decade” AO Systems and Upgrades

! Adaptive secondary mirror –  Enables ground layer AO (GLAO) for wide field spectroscopy –  Simplifies other AO system architectures –  Correction of 500-1000 modes under consideration

! Mid Infra-Red AO (MIRAO) facility –  3 LGS, order 30x30 correction for observations from 4.5 to 25 µm

! Planet Formation Instrument (PFI) high contrast imaging system –  106-107 contrast in H for first-generation system; 108-109 for second –  Advanced MEMs, coronagraphs/nullers, first- and second-stage WFSs

! Multi-Object AO (MOAO) for IR multi-object spectroscopy (IRMOS) –  ~20 IFUs with 50 mas pixels deployable on a 5 arc minute field

! NFIRAOS upgrades for smaller wavefront error and/or improved correction on the full 2 arc min NFIRAOS technical field


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Concepts from 2006 Instrument Feasibility Studies


MIRAO (NOAO/

Univ. Hawaii

IFA)

PFI (Lawrence Livermore/

U. Montreal/ UC Berkeley/ JPL/ Comdev

IRMOS (U. Florida/

HIA)

IRMOS (Caltech)

NFIRAOS Upgrade Concepts


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! “Classical” dual conjugate AO

! Order 1202 DMs ! Reduces on-axis

WFE ! Could use

adaptive M2 “woofer”

! “Hybrid” MOAO

! Order 1202 MEMS

! Reduces WFE over full 2 arc min

! Tri conjugate MCAO

! Order 1202 MEMS ! Reduces WFE over

30 arc sec

Performance Estimates for NFIRAOS Upgrades


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Upgrade Option

LGS photon return

On axis WFE, RMS nm

WFE at 15”, RMS nm

Baseline NFIRAOS

First light estimate

165 180

Upgrade NFIRAOS DMs


133 157

New MOAO or MCAO NFIRAOS Instrument


130 137

2x first light estimate (or pulsed laser)

125 132

Summary

! Since 2009, the TMT first light AO architecture has benefited from two significant refinements: –  NFIRAOS 4-OAP, distortion-free optical design form –  LGSF “center launch” option with lasers on elevation

structure ! Component development progress is continuing

–  Deformable mirrors –  Wavefront sensing detectors –  Guidestar lasers

! Enhanced modeling capabilities predict performance requirements will be met

! From the final report of the Astro2010 Panel on Optical and Infrared Astronomy from the Ground: –  … TMT… has completed a preliminary design for their

first light AO system NFIRAOS, which could be constructed today using existing technologies. 32

Acknowledgements ! The TMT Project gratefully acknowledges the support of the TMT partner institutions. ! They are

–  the Association of Canadian Universities for Research in Astronomy (ACURA), –  the California Institute of Technology –  China's TMT consortium (CTMT) –  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) –  the U.S. National Science Foundation –  the Key International Cooperation Programs of the National Natural Science Foundation of

China (NSFC) –  and the Chinese Academy of Sciences


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Documents

The TMT Adaptive Optics Programao4elt2.lesia.obspm.fr/sites/ao4elt2/IMG/pdf/ao4elt2_ellerbroek.pdf · TMT.AOS.PRE.11.123.REL01 AO4ELT, Victoria, September 26 2011 2 ! First light