Mark ClampinMark ClampinObservatory Project Scientist Observatory Project Scientist Goddard Space Flight CenterGoddard Space Flight Center

217217thth American Astronomical Society Meeting American Astronomical Society Meeting

JWST Telescope Optics:JWST Telescope Optics:Progress ReportProgress ReportJWST Telescope Optics:JWST Telescope Optics:Progress ReportProgress Report

JWST

JWST’s Optical DesignJWST’s Optical Design

3 mirror anastigmat

Elliptical f/1.2 Primary Mirror (PM)

Hyperbolic Secondary Mirror (SM) creates f/9 intermediate image (6 DOF)

Elliptical Tertiary Mirror (TM) images pupil at Flat Fine Steering Mirror (FSM)

Active Optical System

18 primary mirror segments

6 degrees of freedom + ROC

40 K temperature

Beryllium mirrors

3 mirror prescriptions

JWST

JWST Mirror FabricationJWST Mirror FabricationJWST Mirror FabricationJWST Mirror Fabrication

JWST Mirrors made of beryllium Lightweight and stable at 40 K Brush-Wellman

Machined & lightweighted by Axsys 92% material is removed

Raw Be billet (two mirrors)

Primary segment

TertiarySecondary

Mirrors polished at Tinsley Segment cryo-figure: 20 nm

Ambient Surface Figure Cryo Surface Figure

JWST

What is a Flight Mirror ?What is a Flight Mirror ?Primary Mirror Segment Assembly (PMSA) = Mirror + Actuators

Front Face

Rear Face 6 DOF Actuators

Radius of Curvature Actuator + Strongback

JWST

Mirror Polishing PerformanceMirror Polishing Performance

EDU mirror is designated Pathfinder mirror:

EDU allows timely resolution of processing issues, and optimized processing for flight mirrors

EDU

Flight mirrors

Excellent convergence rate on flight mirrors

JWST

Flight Mirror Cryogenic TestingFlight Mirror Cryogenic Testing

JWST

Flight Mirrors Meeting SpecificationFlight Mirrors Meeting Specification

JWST

Aft-Telescope Optical SystemAft-Telescope Optical System

JWST

First Gold Coated EDU Primary MirrorFirst Gold Coated EDU Primary Mirror

JWST

Coating of Flight Mirrors UnderwayCoating of Flight Mirrors Underway

JWST

Gold Coated Mirror AssembliesGold Coated Mirror Assemblies

JWST

Gold Coatings Exceed RequirementsGold Coatings Exceed Requirements

JWST

Flight Mirror Cryogenic TestingFlight Mirror Cryogenic Testing

JWST

Coated Mirror Figures Meet RequirementCoated Mirror Figures Meet Requirement

JWST

Schedule: Acceptance TestingSchedule: Acceptance Testing

JWST

Predicted Image QualityPredicted Image Quality

• JWST optics are designed to be diffraction-limited at a wavelength of 2 μm

• Preliminary simulations of the OTE using A4 flight mirror data as a template for the primary mirror

• Simulated PSF through NIRCam filters

F444W, F200W, F115W, & F070W

NIRCam pixels are 0.032” (SW) and 0.065” (LW)

JWST

Predicted Image Quality: 2 μm & 4 μmPredicted Image Quality: 2 μm & 4 μm

JWST

Predicted Image Quality: 0.7 μm & 1 μmPredicted Image Quality: 0.7 μm & 1 μm

JWST

Flight Mirror: Schedule for 2011Flight Mirror: Schedule for 2011

• 5 flight primary mirrors completed w/gold coating Acceptance testing under way (vibe & optical testing)

• 13 flight mirrors in final polishing cycle

• Flight Secondary in final polishing cycle

• Flight mirror fabrication program will be completed during summer 2011, with delivery of all flight mirrors !

JWST

• Acknowledgements

Chuck Bowers and Kong Ha

Lee Feinberg and OTE team

at GSFC, BATC, NGAS & QCI