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

TMT.AOS.PRE.10.054.REL011

Brent Ellerbroek

TMT Instrumentation @ SPIE 2010San Diego, June 26, 2010.

TMT Early Light Adaptive Optics

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

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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

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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

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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 Software5

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“Split Tomography” Wavefront Control Architecture

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3 NGS OIWFS

6 LGS WFS

Gradient Estimation

Gradient Estimation

LGS Wave-front Recon.

NGS Modal Recon.

Reference processing

DM and TT Control

TTP

2 DMs

Laser Pointing

Focus

T/T

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Tip/Tilt and Plate Scale (Tilt Aniso-planatism) Modes

Higher-order wavefront

modes

NFIRAOS RTC

NFIRAOS

LGSF

Science Instrument

NFIRAOS

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

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NFIRAOS Dimensions (10.35x7.93x4.41m) and Plan View of Nasmyth Platform

•NFIRAOS Electronics

•Instruments

•M1

•Science Calibrator

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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

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NFIRAOS Science Optical Path

•Light From TMT •Entrance Windows

•Telescope Focus

•Off-axis Paraboloid (OAP) 1

•OAP 4

•OAP 2•Output

Focus

•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

New Top-Level LGSF Architecture

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•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)

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Key AO Components

Component Key RequirementsDeformable mirrors 63x63 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 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, near diffraction-limited beam quality

Coupling efficiency of 130 photons-m2/s/W/atom

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Performance Estimate Summary

Error term On-axis RMS WFE, nm

Delivered wavefront error 187

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 [0.41 0.60 0.75] in [J H K] bands

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Sky Coverage vs. Galactic Latitude and Zenith Angle

AO Schedule Overview

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1st 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

LasersUnits 2-7

1/26/16Unit 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

Procurement Plans

AO Systems

NFIRAOS NRC Canada

LGSF TBD (partner or vendor)

AO Executive Software TBD (partner, vendor, or PO)

Subsystems and Components

Wavefront Correctors CILAS

Visible WFS CCDs MIT Lincoln Laboratory

Visible WFS cameras and readout electronics TBD (partner or vendor)

IR WFS detectors Teledyne (TBC)

IR WFS cameras and readout electronics TBD (partner or vendor)

Real Time Controller TBD (partner or vendor)

Guidestar laser systems TBD (partner or vendor)

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Contracts begin at or near the beginning of the TMT construction phase in October, 2011

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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

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