adaptive optics module mechanical design

MCAOMCAO

Adaptive Optics Module Adaptive Optics Module Mechanical DesignMechanical Design

Eric James

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAOMajor Design IssuesMajor Design Issues•Packaging

•Weight and balance

•Volume

•Access to components

•Structural

•ISS interface

•Flexure/vibrations

•Thermal expansion

•Performance

•Minimize surfaces

•Minimize reflection angles

MCAOMCAO

3 MCAO Preliminary Design Review

May 24-25, 2001

AOM Location

AO Module

8 meter Primary Mirror

Instrument support structure

Cassegrain Rotator


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MCAOMCAO

Electronics

Bay

Optics Bay

Electronics

Bay


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MCAOMCAOScience path

LGS path

NGS path

Beam splitters

LGS focus

Science focus

NGS focus

Optical PathsOptical Paths


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Optical BenchOptical Bench


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Bench SupportBench Support


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MCAOMCAO9U 19”rack mount chasses (12 total)

Electronics EnclosuresElectronics Enclosures


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MCAOMCAOElectronics Bay OpenElectronics Bay Open


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Heat exchanger

100 mm foam insulation at optics bay

50 mm foam insulation elsewhere

Air flow

Calculated heat loss to dome: 35 –85 Watts

Thermal ManagementThermal Management


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Finite Element AnalysisFinite Element Analysis

• Static (Gravity Induced) Flexure Analysis• Telescope at zenith• Zenith angle = 45º• Zenith angle = 60º

• Dynamic (Vibration Induced) Flexure Analysis• Natural frequency• Vibration Amplitude

• Seismic (Earthquake Induced) Stress Analysis


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Telescope at Zenith:

Maximum deflection ~50 m

Gravity

Static Analysis at Zenith


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Telescope at 60º from Zenith:

Maximum deflection ~200 m

Gravity

Static Analysis at 60º from Zenith


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Dynamic AnalysisDynamic Analysis

Mode 1: “fishtailing” motion

Lowest natural frequency: 39 Hz

Dynamic Analysis


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Seismic AnalysisSeismic AnalysisSeismic Analysis

Maximum Stress:

~ 8 x 106 Pascals


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AlignmentAlignment

• Initial Alignment (acquire image)– Align elements within major components to datum

surface.• Done by vendor at vendor facility.

– Align components and single elements to the optical bench.

– Align optical bench to the telescope.• Done by Gemini on the telescope at Gemini south.

• Final Alignment (optimize image)– Wave front analysis using source simulators and wave

front sensors.– Image analysis using stars and science detector.


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MCAOMCAOAO Module Sensitivity AO Module Sensitivity AnalysisAnalysis

• Optical fabrication and alignment sensitivities computed

• Modeling accounts for partial compensation of errors by the AO control loops– Initial alignment in the lab– Flexure/thermal errors during closed-loop operation

• Sensitivities computed for– Higher order wave front errors (science, NGS, LGS

paths)– Pupil alignment/distortion (science, LGS paths)– Boresight (tip/tilt) errors (science, LGS paths)– DM adjustments to compensate errors


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Error Budget chartError Budget chart


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Source simulator

Sensors and compensators for final Sensors and compensators for final alignment in the labalignment in the lab

DMs

NGS WFS

LGS WFS

Science Instrument

Mean tip/tilt and higher order correction (3 x 35 Zernikes)

•Tip/tilt/focus adjustments

•Pupil alignment

Tip/tilt/focus adjustment

Diagnostic WFS

Astronomer

Non-common path calibration

Influence function measurements

Distortion map


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MCAOMCAO

Telescope

Sensors and compensators for Sensors and compensators for closed-loop AOclosed-loop AO

DMs

Least-squares fit

NGS WFS

LGS WFS

OIWFS

•M2 focus

•Telescope pointing

On-axis

Tip/tilt/focus

•LGS WFS focus

•NGS WFS boresight

Pupil mirror

3 by 35

Zernikes

5 by 35 Zernikes

(tilt removed)

3 x tip/tilt

5 x tip/tilt

LGS pointing


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Wave front error budget resultsWave front error budget resultsError budget study results summary 20-Apr-01

Line Error Optical Zenith Error Source OverallNo. Category Path Description Angle Dsgn res. Fabric. Init. Align Flex/therm Rad/index (RSS) units

1 Wave front error Science Tilt removed 0 1.294E+01 4.150E+01 7.700E-03 4.050E+01 1.210E-01 5.941E+01 nm2 " " " 45 1.294E+01 4.150E+01 7.700E-03 7.960E+01 1.210E-01 9.070E+01 "3 " " " 60 1.294E+01 4.150E+01 7.700E-03 8.560E+01 1.210E-01 9.601E+01 "4 " " RMS 2-axis tip/tilt 0 Calibrated Calibrated Calibrated 1.160E-02 1.309E-05 1.160E-02 arc sec5 " " " 45 Calibrated Calibrated Calibrated 3.500E-02 1.309E-05 3.500E-02 "6 " " " 60 Calibrated Calibrated Calibrated 3.800E-02 1.309E-05 3.800E-02 "7 " Laser GS Tilt removed 0 3.528E+01 5.840E+01 7.540E+01 4.410E-01 3.430E-05 1.017E+02 nm8 " " " 45 3.528E+01 5.840E+01 7.540E+01 1.290E+00 3.430E-05 1.017E+02 "9 " " " 60 3.528E+01 5.840E+01 7.540E+01 1.440E+00 3.430E-05 1.017E+02 "

10 " " RMS 2-axis tip/tilt 0 Calibrated Calibrated Calibrated 5.040E-01 4.580E-04 5.040E-01 arc sec11 " " " 45 Calibrated Calibrated Calibrated 9.030E-01 4.580E-04 9.030E-01 "12 " " " 60 Calibrated Calibrated Calibrated 1.015E+00 4.580E-04 1.015E+00 "13 " Natural GS Tilt removed 0 4.558E+01 4.810E+01 6.540E+01 5.380E+01 5.800E-02 1.075E+02 nm14 " " " 45 4.558E+01 4.810E+01 6.540E+01 7.590E+01 5.800E-02 1.201E+02 "15 " " " 60 4.558E+01 4.810E+01 6.540E+01 8.400E+01 5.800E-02 1.254E+02 "1617 Pupil Variables Science Pupil Motion 45 8.600E-03 2.000E-02 1.090E-03 4.110E-04 8.740E-04 2.182E-02 beam diam18 " " Pupil Mag 45 1.600E-02 2.000E-02 1.680E-02 4.460E-03 2.140E-05 3.095E-02 "19 " Laser GS RMS 2-axis Pupil Motion 45 1.130E-04 0.000E+00 0.000E+00 3.500E-02 3.110E-05 3.500E-02 "20 " " Induced LGS motion 45 1.164E-03 0.000E+00 0.000E+00 3.605E-01 3.203E-04 3.605E-01 arc sec21 " " RMS Pupil distortion 45 1.722E-03 2.600E-03 2.260E-03 1.180E-03 3.050E-06 4.028E-03 beam diam2223 DM adjustments DM0 45 2.760E+01 1.200E+02 3.500E+01 1.780E+01 4.434E+00 1.293E+02 nm OPD24 DM4.5 45 3.840E+01 1.200E+02 5.670E+00 2.630E+01 4.434E+00 1.289E+02 "25 DM9.0 45 2.920E+01 1.200E+02 1.330E+01 6.150E+01 4.434E+00 1.387E+02 "

LegendAllocationIncludes 20 nm allocation for LGS WFS spot relay lens

Red numbers indicate the value is over budget or at least of some concern


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MCAOMCAOError Budget points of Error Budget points of interestinterest•Most areas meet goals. All goals are met at the zenith position.

•Flexure at 45º and 60º are about 50% over the goals. This suggests special design effort at a few areas.

•Science path tip/tilt errors must be carefully calibrated out.

•Within goals for:

•LGS pupil displacement (input to simulations)

•LGS WFS boresight errors (input to simulations)

•LGS RMS pupil distortion (input to simulations)

•RMS wave front errors in LGS and NGS paths

•DM adjustments


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MCAOMCAOActive Active ComponentsComponents

•Source simulators

•Science ADC

•DM0 aperture stop

•Beam splitter changer

•Diagnostic wave front sensor

•Shutters

•NGS wave front sensor

•NGS ADC

•LGS zoom corrector

•LGS wave front sensor


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LGS wave front sensorLGS wave front sensor

Commercial tip/tilt mirrors

CCD detectors

5 beam paths – 2 omitted for clarity

Active lenses


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NGS Wave front sensorNGS Wave front sensor

NGS path

NGS path

Probe arms

X-Z translation stages


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MCAOMCAODiagnostic WFS/Source Diagnostic WFS/Source simulatorssimulators

NGS Source

LGS Source

Diagnostic WFS

•LGS Source

•5-star constellation

•LEDs at ~.589 microns

•NGS Source

•5x5 array of 4 micron diameter fiber sources

•8 200 micron diameter sources at ~ 1 arc minute radius

CCD detector

Video camera (not shown)


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LGS Zoom CorrectorLGS Zoom Corrector

LGS wave front sensor

Moving elements

Fixed elements


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Beam splitter changerBeam splitter changer

Science path

From DMs

LGS/NGS path

Science path

To Science instrument

Rotation to change beam splitters

Science ADC


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Misc. Active componentsMisc. Active components

• Science ADC• Counter-rotating prisms• Retractable• Calcium fluoride and silica prisms

• NGS ADC• Counter-rotating prisms• Flint and crown prisms

• Shutters• Baseline same as Altair

• Aperture stop• Normally retracted, used only with source simulator to

overfill DM0 for flattening.


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Mass and Center of GravityMass and Center of Gravity

970kg (estimated)

1060 mm

900kg

Goal center of mass

1200 mm

13 mm


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MCAOMCAOProcurement strategy -Procurement strategy -5 work packages:5 work packages:

1. AO Bench (including enclosures and most electronics)

2. Deformable mirrors

3. Diagnostic WFS & source simulators

4. LGS wave front sensor

5. NGS wave front sensor


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MCAOMCAOProcurement Strategy –Procurement Strategy –Acceptance testing & IntegrationAcceptance testing & Integration

AO Bench DMs LGS WFS DWFS/ SourcesNGS WFSVendor facilities: Pre-ship tests

Hilo: Acceptance tests, integration, & closed-loop AO

Cerro Pachon: reassembly, realignment, & commissioning


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PDR AgendaPDR Agenda

Thursday, 5/240800 Welcome 0805 Project overview 0830 Science case0930 Break0945 System overview1015 System modeling1100 AO Module optics1145 Lunch

1245 AO Module mechanics1340 AO Module electronics1400 Break1415 Beam Transfer Optics1510 Laser Launch

Telescope1545 Closed committee

session1800 Adjourn

adaptive optics module mechanical design

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