MCAO Adaptive Optics Module Mechanical Design Eric James

MCAO May 24-25, 2001MCAO Preliminary Design Review2 Major Design Issues Packaging Weight and balance Volume Access to components Structural ISS interface Flexure/vibrations Thermal expansion Performance Minimize surfaces Minimize reflection angles

MCAO May 24-25, 2001MCAO Preliminary Design Review3 AOM Location AO Module 8 meter Primary Mirror Instrument support structure Cassegrain Rotator

MCAO May 24-25, 2001MCAO Preliminary Design Review4 Electronics Bay Optics Bay Electronics Bay

MCAO May 24-25, 2001MCAO Preliminary Design Review5 Science path LGS path NGS path Beam splitters LGS focus Science focus NGS focus Optical Paths

MCAO May 24-25, 2001MCAO Preliminary Design Review6 Optical Bench

MCAO May 24-25, 2001MCAO Preliminary Design Review7 Bench Support

MCAO May 24-25, 2001MCAO Preliminary Design Review8 9U 19”rack mount chasses (12 total) Electronics Enclosures

MCAO May 24-25, 2001MCAO Preliminary Design Review9 Electronics Bay Open

MCAO May 24-25, 2001MCAO Preliminary Design Review10 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 Management

MCAO May 24-25, 2001MCAO Preliminary Design Review11 Finite 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

MCAO May 24-25, 2001MCAO Preliminary Design Review12 Telescope at Zenith: Maximum deflection ~50  m Gravity Static Analysis at Zenith

MCAO May 24-25, 2001MCAO Preliminary Design Review13 Telescope at 60º from Zenith: Maximum deflection ~200  m Gravity Static Analysis at 60º from Zenith

MCAO May 24-25, 2001MCAO Preliminary Design Review14 Dynamic Analysis Mode 1: “fishtailing” motion Lowest natural frequency: 39 Hz Dynamic Analysis

MCAO May 24-25, 2001MCAO Preliminary Design Review15 Seismic Analysis Maximum Stress: ~ 8 x 10 6 Pascals

MCAO May 24-25, 2001MCAO Preliminary Design Review16Alignment 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.

MCAO May 24-25, 2001MCAO Preliminary Design Review17 AO Module Sensitivity Analysis 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

MCAO May 24-25, 2001MCAO Preliminary Design Review18 Error Budget chart

MCAO May 24-25, 2001MCAO Preliminary Design Review19 Source simulator Sensors and compensators for final alignment 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

MCAO May 24-25, 2001MCAO Preliminary Design Review20 Telescope Sensors and compensators for closed- 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

MCAO May 24-25, 2001MCAO Preliminary Design Review21 Wave front error budget results Red numbers indicate the value is over budget or at least of some concern

MCAO May 24-25, 2001MCAO Preliminary Design Review22 Error Budget points of interest 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

MCAO May 24-25, 2001MCAO Preliminary Design Review23 Active Components 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

MCAO May 24-25, 2001MCAO Preliminary Design Review24 LGS wave front sensor Commercial tip/tilt mirrors CCD detectors 5 beam paths – 2 omitted for clarity Active lenses

MCAO May 24-25, 2001MCAO Preliminary Design Review25 NGS Wave front sensor NGS path Probe arms X-Z translation stages

MCAO May 24-25, 2001MCAO Preliminary Design Review26 Diagnostic WFS/Source simulators 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 micron diameter sources at ~ 1 arc minute radius CCD detector Video camera (not shown)

MCAO May 24-25, 2001MCAO Preliminary Design Review27 LGS Zoom Corrector LGS wave front sensor Moving elements Fixed elements

MCAO May 24-25, 2001MCAO Preliminary Design Review28 Beam splitter changer Science path From DMs LGS/NGS path Science path To Science instrument Rotation to change beam splitters Science ADC

MCAO May 24-25, 2001MCAO Preliminary Design Review29 Misc. 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.

MCAO May 24-25, 2001MCAO Preliminary Design Review30 Mass and Center of Gravity 970kg (estimated) 1060 mm 900kg Goal center of mass 1200 mm 13 mm

MCAO May 24-25, 2001MCAO Preliminary Design Review31 Procurement strategy - 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

MCAO May 24-25, 2001MCAO Preliminary Design Review32 Procurement Strategy – Acceptance testing & Integration AO BenchDMs LGS WFS DWFS/ Sources NGS WFS Vendor facilities: Pre-ship tests Hilo: Acceptance tests, integration, & closed-loop AO Cerro Pachon: reassembly, realignment, & commissioning

MCAO May 24-25, 2001MCAO Preliminary Design Review33 PDR Agenda Thursday, 5/ Welcome 0805 Project overview 0830 Science case 0930 Break 0945 System overview 1015 System modeling 1100 AO Module optics 1145 Lunch 1245 AO Module mechanics 1340 AO Module electronics 1400 Break 1415 Beam Transfer Optics 1510 Laser Launch Telescope 1545 Closed committee session 1800 Adjourn