Exoplanet Imaging with the PIAA Coronagraph: Latest Laboratory Results from NASA Ames

Rus Belikov, Michael Connelley, Tom Greene, Dana Lynch, Mark McKelvey, Eugene Pluzhnik, Fred Witteborn

(NASA Ames Research Center)

Olivier Guyon(Subaru / UofA)

DZ 2.0 - 5.5 l/D, contrast = 5.23e-007

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Outline

• Motivation for PIAA and overview

• Lab description and results

• New PIAA mirror manufacture and simulationsShanghai, July 23, 2009

PIAA (phase-induced amplitude apodization) PIAA (phase-induced amplitude apodization) overview and motivationoverview and motivation

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PIAA invented by Olivier Guyon with PIAA invented by Olivier Guyon with significant contributions by Bob significant contributions by Bob Vanderbei, Wesley TraubVanderbei, Wesley Traub

High-throughput (almost 100%)High-throughput (almost 100%) Aggressive IWA (2 Aggressive IWA (2 /D)/D) Potentially enables Earth-like planet Potentially enables Earth-like planet

imaging with a 1.4m telescope (PECO)imaging with a 1.4m telescope (PECO) Can also be used on a balloon Can also be used on a balloon

(planetscope) or TPF Flagship(planetscope) or TPF Flagship Track record of successful hardware Track record of successful hardware

development and testingdevelopment and testing

Focal planeOriginal uniformly

illuminated pupil plane

New, apodized pupil plane Focal plane

PECO mission concept Simulated Earth image around Tau Ceti,

Shaped pupil Apodizer

ARC testbed description and role in PIAA ARC testbed description and role in PIAA technology developmenttechnology development

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New (March 08), flexible, rapidly New (March 08), flexible, rapidly reconfigurable facility in airreconfigurable facility in air

Successor to Olivier Guyon’s 1Successor to Olivier Guyon’s 1stst PIAA PIAA testbed at Subarutestbed at Subaru

Dedicated to testing PIAA and related Dedicated to testing PIAA and related technologiestechnologies

Partnering with JPL’s HCIT, with Partnering with JPL’s HCIT, with complementary roles identifiedcomplementary roles identified ARCARC

initial validation of lower TRL initial validation of lower TRL technologies and conceptstechnologies and concepts MEMS DMsMEMS DMs WFC architecture tradesWFC architecture trades dichroicsdichroics

PIAAgen2 mirror manufacturePIAAgen2 mirror manufacture JPL/HCITJPL/HCIT

higher TRL and vacuum higher TRL and vacuum validationvalidation

testing a variety of testing a variety of coronagraphscoronagraphs

Ames Coronagraph Lab

In a partnership with JPL’s HCIT

Other partnerships and rolesOther partnerships and roles

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NASA Ames Research CenterTom Greene ARC testbed directorMark McKelvey ARC testbed managerRus Belikov technical leadEugene Pluzhnik experimentsMichael Connelley experimentsFred Witteborn thermal enclosureDana Lynch optical design

Tinsley Laboratories(PIAA mirror manufacture)Daniel JayAsfaw BekeleLee DettmannBridget PetersTitus RoffClay Sylvester

NASA Jet Propulsion Lab John TraugerAndy KuhnertBrian KernMarie LevineWesley TraubStuart ShaklanAmir Give'onLaurent Pueyo

UCSC (DM characterization)Donald GavelDaren DillonRenate KupkeAndrew Norton

UofA/Subaru (PIAA design and consulting)Olivier Guyon

Lockheed Martin(Optical design)Rick KendrickRob SiglerAlice Palmer

First stage of experimentsFirst stage of experiments

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Initial goal: create a testbed capable of supporting high contrast levels Initial goal: create a testbed capable of supporting high contrast levels (1e-9)(1e-9)

Approach: keep things as simple as possibleApproach: keep things as simple as possible Use lensesUse lenses Use monochromatic lightUse monochromatic light Switch to mirrors and broadband light once testbed stability and Switch to mirrors and broadband light once testbed stability and

wavefront control are developed to better than ~1e-8 contrastwavefront control are developed to better than ~1e-8 contrast (Or maybe lenses can be made sufficiently achromatic and with a (Or maybe lenses can be made sufficiently achromatic and with a

good enough AR coating?)good enough AR coating?)

Light source(single mode fiber-coupled laser)650nm

DM (deformable mirror)

CCD

PIAA System Focusing lensCollimating lens

Focal plane occulter

Lens

PIAA systemPIAA system

Light source(single mode fiber-coupled laser)650nm

DM (deformable mirror)

CCD

PIAA System Focusing lensCollimating lens

Focal plane occulter

Lens

Made by Axsys, diamond-turned CF2, 16mm active diameterMade by Axsys, diamond-turned CF2, 16mm active diameter Post-apodizer (concentric-ring shaped pupil) made by JPL’s Microdevices Post-apodizer (concentric-ring shaped pupil) made by JPL’s Microdevices

laboratory, aluminum on glasslaboratory, aluminum on glass

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MEMS Deformable Mirror MEMS Deformable Mirror

Light source(single mode fiber-coupled laser)650nm

DM (deformable mirror)

CCD

PIAA System Focusing lensCollimating lens

Focal plane occulter

Lens

Made by Boston Micromachines, 32x32 actuators, 10mm active areaMade by Boston Micromachines, 32x32 actuators, 10mm active area Strong motivation for small MEMS DMs: for small telescopes, small DM Strong motivation for small MEMS DMs: for small telescopes, small DM

size may be necessary to keep instrument size reasonable size may be necessary to keep instrument size reasonable

Contrast results Wavefront control algorithms (both

based on image-plane sensing through DM diversity):

Variant of classical speckle nulling (Trauger and Burrows)

Based on targeting and removing individual speckles

Many speckles at a time For each speckle, scan not only the

phase, but also the amplitude of corresponding ripples on DM

Slow (100s of iterations, hours), but does not require detailed system model

Electric Field Conjugation (Give’on et. al.)

Estimates and corrects the entire dark zone on each iteration

Fast (minutes), but requires a precise system model

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

1.5e-7 from 2.0 to 4.8 /D

StabilityStability

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QuickTime™ and a decompressor

are needed to see this picture.

~10-20mK rms temperature variation over 20 minutes 3e-9 - 1e-8 rms speckle variation over 20 minutes

Active thermal control systemActive thermal control system

Water circuit with PID controllerWater circuit with PID controller An earlier version already demonstrated by Guyon at SubaruAn earlier version already demonstrated by Guyon at Subaru Expected to provide a few mK-level temperature stability or better and stability of better than 1e-9Expected to provide a few mK-level temperature stability or better and stability of better than 1e-9

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Limiting factorsLimiting factors Major limiting factors in the past:Major limiting factors in the past:

CCD artifacts (scattering off microlenses, CCD circuitry and shutter)CCD artifacts (scattering off microlenses, CCD circuitry and shutter) Eliminated by introducing a focal plane stopEliminated by introducing a focal plane stop

Ghosts from transmissive elementsGhosts from transmissive elements Eliminated by a long-coherence-length laserEliminated by a long-coherence-length laser

Alignment, baffling, system model, air currentsAlignment, baffling, system model, air currents

Current known limiting factorsCurrent known limiting factors Polarization effectsPolarization effects

Starting to control with polarizersStarting to control with polarizers

Expected future limiting factorsExpected future limiting factors Stability (1e-8)Stability (1e-8) DM voltage level quantization (1e-9 to 1e-8)DM voltage level quantization (1e-9 to 1e-8)

Solving limiting factors seems to proceed at a predictable rate (2x Solving limiting factors seems to proceed at a predictable rate (2x improvement in contrast every 6 weeks), as long as funding persistsimprovement in contrast every 6 weeks), as long as funding persists

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By Sydney Harris

New PIAA mirrors manufacturedNew PIAA mirrors manufactured

Made by TinsleyMade by Tinsley Gen2: Better achromatic design, better surface accuracy than gen1 mirrorsGen2: Better achromatic design, better surface accuracy than gen1 mirrors Currently being tested at HCITCurrently being tested at HCIT

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Wavefront qualityWavefront quality

Surface figure spec was only for spatial frequencies < 20 cycles per apertureSurface figure spec was only for spatial frequencies < 20 cycles per aperture That left mid-spatial frequency errors highThat left mid-spatial frequency errors high We now know though simulations that these errors can hurt usWe now know though simulations that these errors can hurt us

Modeling of gen2 mirrorsModeling of gen2 mirrors

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Fast but approximate model confirmed by higher fidelity Fast but approximate model confirmed by higher fidelity ones (Amir Give’on and Laurent Pueyo)ones (Amir Give’on and Laurent Pueyo)

Predicts that current Tinsley mirrors will get to no better Predicts that current Tinsley mirrors will get to no better than 1e-9than 1e-9

Limited by chromaticity of frequency folding of mid-spatial Limited by chromaticity of frequency folding of mid-spatial frequency errorsfrequency errors

Different WFC architectures don’t help muchDifferent WFC architectures don’t help much Mirrors can be smoothed by a factor of 2, bringing Mirrors can be smoothed by a factor of 2, bringing

theoretically possible contrast to 1e-10theoretically possible contrast to 1e-10 Modeling of PIAA is mature, but accuracy of fast Modeling of PIAA is mature, but accuracy of fast

approximate models not well quantifiedapproximate models not well quantified

ConclusionsConclusions

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New laboratory at NASA Ames was established for prototyping New laboratory at NASA Ames was established for prototyping PIAA coronagraph and related technologies through early TRL PIAA coronagraph and related technologies through early TRL levels before vacuum testing at JPL’s HCITlevels before vacuum testing at JPL’s HCIT

State of the art coronagraph performance at 2 State of the art coronagraph performance at 2 /D : 1.5e-7/D : 1.5e-7

Vacuum testbeds may not be required to work in high contrasts Vacuum testbeds may not be required to work in high contrasts (~1e-9)(~1e-9)

A new PIAA coronagraph mirror set manufactured (by Tinsley) A new PIAA coronagraph mirror set manufactured (by Tinsley) designed for 1e-9 contrast in a 10% banddesigned for 1e-9 contrast in a 10% band