Herriot NFIRAOS AO4ELTs Paris June 2009ao4elt.lesia.obspm.fr/sites/ao4elt/IMG/pdf/Herriot.pdf ·...

TMT.AOS.PRE.09.031.REL01 1

NFIRAOS

Glen HerriotHerzberg Institute of Astrophysics (HIA)

Victoria CanadaAO4ELT Conference

Paris June 22-26, 2009


NFIRAOS On TMT

(Future)

IRIS

IRMSNFIRAOS


NFIRAOS Top-Level Requirements

85 per cent throughput from 0.8 to 2.5 μmThermal emission < 15 % of background from sky and telescope187 nm RMS WFE on-axis, and 191 nm on a 10” FoV– “High” enclosed energy within 160 mas pixels over a 2’ FoV

50 per cent sky coverage at the Galactic pole2% differential photometry for a 2 minute exposure on a 30” FoV50 μas differential astrometry for a 100s exposure on a 30” FoV– Error falling as t-1/2 to a systematic floor of 10 μas

System available from standby within 10 minutes5 minutes to acquire a new field< 1 per cent unscheduled downtime


NFIRAOS Architecture

High sky coverage (< 2 mas tip/tilt jitter at galactic pole)– Near infra-red tip/tilt & focus sensing on “sharpened” guide star

images– Guide star sensing within client instruments– 2 arc minute guide field to locate guide stars

Three tip/tilt guide stars to detect image distortionGood image quality in the near IR over a 10-30” FoV:– Atmospheric tomography with six laser guide stars– Multi-conjugate wavefront correction (also helps sky coverage)

Good optical throughput and low background:– Minimum surface count– System cooled to -30 Celsius


NFIRAOS

Telescope Beam passes through

NSCU to Entrance Window

NFIRAOS Science

Calibration Unit (NSCU)

Wavelength and flat fields

IRIS

IRMS

Future Instrument


NFIRAOS Team

TMT AO Manager Brent Ellerbroek

TMT AO staff

Systems - Corinne Boyer Modeling – Luc Gilles, Lianqi Wang

NFIRAOS Proj. Mgr. Glen Herriot

Mechanics

Peter Byrnes, Ivan Wevers

Optics

Jenny Atwood

AO Scientist

David Andersen Jean-Pierre Véran

NFIRAOS Proj. Scientist Paul Hickson U. BC

Electronics

Chris Caputa

Modeling

R. Conan UVic Craig Irvin HIA

Software

Malcolm Smith

TMTHIA

U. British Columbia


NFIRAOS Science Optical Path

Minimizes number of surfacesLarge size set by 5-mm actuator pitch on Deformable Mirrors3 Instrument Ports

DM on Tip/Tilt stage

Light from TMT

Off-axis Parabolic mirror (OAP)

OAP

DM


NGSPath

LGS Path

Science Path Components

From Telescope

NFIRAOS Functional Block Diagram


OAP2

IR Acquisition camera

2 Truth NGS WFSs1 60x60 NGS WFS

OAP1

6 60x60 LGS WFSs

63x63 DM at h=0kmOn tip/tilt platform

76x76 DM at h=11.2km

Output to science instruments and IR T/T/F WFSs

Input from

telescope

NFIRAOS Opto-mechanical Layout


Space Frame: Current optical support concept.


Space Frame FEA: 13 Hz – 2x improvement in natural frequency

Bipod supports

(3x)


Space Frame supported by bipods


Cooling NFIRAOS for Observing Efficiency

Air Handling Unit for cool-down only

Cold plate at -30 C buried near inside of wall, holds temperature

Evacuated double window

Copper gasket conducts heat from removable panels to fixed heat exchangers on structure


5 10 15 20 25 3040

35

30

25

20Allowable AO Temperature vs emissivity

Emissivity %

Tem

pera

ture

Cel

sius

2000 2100 2200 2300 24000.01

0.1

1

10

10015% x (Teles. + Sky) vs NFIRAOS

Wavelength nm

phot

ons /

( as

ec^2

m^2

nm

s )

NFIRAOS Design15%(Telescope + Sky) K Band

Meet Spec.

Temperature vs Emissivity

15%

-30 C

•Observing time decreases directly with decrease in thermal background


Qualifying the Cooled NFIRAOS

Operation at -30 C– Optical alignment– Mechanism reliability– Component performance when cold (DMs, tip/tilt stage, coatings)– Thermal plumes degrade image quality– Air leakage into optics enclosure– Humidity and frost

Development Plan and Qualification– Subscale DMs and prototype tip/tilt stage have been tested cold– Building sub-scale cold chamber with evacuated window, super-

insulation and buried cold plates in walls– Components (e.g. motorized stages) will be qualified in cold– CFD of local seeing effects


IRISUpper Instrument

Interface

Instrument Mounting Interfaces

Rotary Seal

Bearing

Side Instrument Port


Gate Valve and Port Plug

Prior to detaching an instrument, the gate valve will be remotely shut– This maintains the integrity of the NFIRAOS optics enclosure when the

instrument snout disengagesImmediately after instrument removal, the insulated port plug will be manually installed

IRIS

GATE VALVE CLOSED

INSULATED PORT PLUG INSTALLED


NFIRAOS Laser Guide Star Wavefront Sensors

IRIS

IRMS

FutureNFIRAOS

6 LGS WFSs

85 - 235 km re-focus

Fixed Lenses

Periscope

Wavefront sensors at dome temperature


Field weighting

Altitude weighting

25 Weighted Wavefront Maps

1/21/8

1/8

1/8

1/8

•Averaged over diameter and length of sodium beacon

• < 100 nm worst case wavefront aberration vs range distance

Non-common path aberrations vs. Intensity Variations in the Sodium Layer

Diameter of sodium beacon


LGS Distortion Maps

Vector map of imaging distortion of DM actuators onto WFS lenslets<10% of a lenslet pitchFit by a 2-D polynomial (5th

order)Performance modeling result: <12 nm rms WFE


Visible Natural WFS bench

Visible Natural Wavefront Sensor Bench

Gimbal Mirrors select a natural guide star

NGS WFS deployable to control DM without lasers

Truth WFSs establish offsets for LGS WFSs


MOVING OPTICS

MOTOR

LINEAR MOTION RAILS

RANGE OF MOTION

~1.5m

END VIEW

BALLSCREW & NUT

RAILS AND SLIDES

Internal NFIRAOS calibration unit

ORANGE LEDs

•Simulates laser beacons - 85 – 235 km range


Focal Plane Calibration Mask

FOCAL PLANE MASK

RETRACTED

FIXED LIGHT

SOURCES

BEAMSPLITTER AND FOLD MIRROR DEPLOYED

FOCAL PLANE MASK DEPLOYED

BEAMSPLITTER AND FOLD MIRROR RETRACTED

focal plane mask in NFIRAOS with fixed pinhole array– Mask will be back illuminated by a rotating pupil projected from

NFIRAOS Science Calibration Unit– Calibration reference for NGS WFS pointing and focal plane distortion


Acquisition Camera

NIR commercial

camera

lensbarrel

lensgroup

foldmirrors

Instrument selection fold


RTC (Real Time Controller) Architecture

Solves 38k x 7k NFIRAOS control problem at 800 HzAlgorithms adapt in real time to turbulence and sodium layer variationsTwo design studies completed in March


Design Optimization Underway

Currently in Preliminary Design Update Phase– NFIRAOS PDR was in November

Move DM12 to 11.2 km – issue: better performance vs Zenith angle, and allows adding a guard ring of actuators efficientlyAlignment Procedure, fixtures, test pointsEarthquake Survival of individual optics mounts and tip/tilt platformSensitivity to Telescope windshake and vibrationPrototype and cold test critical components, insulation, and coolingStray Light analysisCalibration fixture for LGS Zoom opticsLab experiments– Non-Common Path calibration procedures– PSF estimation from telemetry

Thermal analysis– motor dissipation – CFD (computational fluid dynamics) of local heat sources


NFIRAOS Schedule


Acknowledgments

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 Association of Universities for Research in Astronomy (AURA), the California Institute of Technology and the University of California. This work was supported, as well, by the Canada Foundation for Innovation, the Gordon and Betty Moore Foundation, the National Optical Astronomy Observatory, which is operated by AURA under cooperative agreement with the National Science Foundation, the Ontario Ministry of Research and Innovation, and the National Research Council of Canada.

Herriot NFIRAOS AO4ELTs Paris June 2009ao4elt.lesia.obspm.fr/sites/ao4elt/IMG/pdf/Herriot.pdf ·...

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