Post on 04-Jan-2016
description
High-Contrast Imaging and the Direct Detection of Exoplanets
Sandrine Thomas, Ruslan Belikov, and many collaborators
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Is there another Earth out there?
Is there life on this over Earth?
Requirements for habitability
1. Planet size:~ 0.5 – 2 Earth size
2. Temperature:0-100 C
3. Biomarkers: water and oxygen 3
not habitable(too large, hydrogen gas does not escape)
habitable
not habitable(too small to keep oxygen and water)
H2O(Water)
O2
(Oxygen)
(Schematic representation only)
Credit: Petigura/UC Berkeley, Howard/UH-Manoa, Marcy/UC Berkeley
Ref: R. Hanel, GSFC
O2
Iron oxides
CO2
H2O H2O
CO2
EARTH-CIRRUS
VENUS
X 0.60
MARS
EARTH-OCEAN
H2O H2O
H2O ice
O3O2
Spectroscopy: detecting biomarkers
Detecting atmospheric oxygen and water likely indicates life(because very few non-biological processes can sustain an oxygen atmosphere)
861 confirmed planets (677 planetary systems)2740 planet candidates (from Kepler mission)
Wobble method #1: Radial Velocity(Wobble method #2: Astrometry)
Direct detection
Direct ImagingMain Engineering Requirements
• Contrast– ~1010 for Earth-like planets– ~107 for young hot planets and disks
• Inner Working Angle– The smaller the better!– Typically 1-3 l/D required on missions
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2010 2020
Kepler
2030
Exo-C/S or AFTA(~1.4m / 2.4m,$1B / $2B+)
New WorldsTelescope($4-8m, $4B+)
Beyond Kepler: Direct imaging missions
Small sats(0.25-0.7m,~$5 – 200M)Earth-sizeHabitable zoneSpectroscopyTwo stars: aCen
Earth-sizeHabitable zoneNo spectroscopy (biomarkers)Not nearby systems
Earth-sizeHabitable zoneSpectroscopy~100s of Earths
All these missions also do ground-breaking science on non-habitable planets
Earth-sizeHabitable zoneSpectroscopy~6-20 stars
Another Earth?
Simulation of an exo-Earth around aCenwith a $1B mission (1.5m telescope)
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Ground based Instruments:Exoplanet direct imaging instruments
SPHERE
GPI
P1640 SCExAO
Beuzit et al, 14
Hinkley et al, 08 Guyon et al, 10
Macintosh et al, 14
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High Contrast Imaging
Like searching for a firefly next to a lighthouse in San Francisco from Boston=> Very faint and small in comparison
Upper Scorpius Lafreniere et al 2008
Beta Pictoris b Lagrange et al 2010
HR 8799 Marois et al 2008
Fomalhaut b Kalas et al 2008
Limitations• Diffraction from the parent star
– Depends on telescope diameter and wavelength: FWHM=lambda/d
• Passives and active aberrations in the system – Constant: static aberrations of the system – 1Hz: drifts due to temperature, flexure,
mechanical instability.– 1KHz: from the ground: atmosphere
• Amplitude errors and Talbot effect that turns amplitude errors into phase errors 1 nm RMS non-
common path WFE
5 nm RMS non-common path WFE
Solutions• Diffraction: Coronagraphs• Aberrations: Active and adaptive optics
– Wavefront sensor : Shack-Hartmann, curvature sensors– Deformable mirror– Control software
fromtelescope DM system Coronagraph
Science camera
WFS Starlight rejectedby coronagraph
feedback
Diagram of a direct imaging instrument
feedback
The Lyot CoronographSivaramakrishna, 2001
Principle of Pupil Apodization-type coronagraphs
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Image plane
starlight
Telescope pupil Resulting image
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Apodizer manufacture:halftone technique using black chrome microdots
by JenOptiks.
The apodizer transmission is obtained by randomly distributing 2μm square dots over the glass.
The Apodized Lyot coronagraph
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Pupil plane Focal plane Lyot stop ImageAime et Al. 2001
Challenge #2: optical aberrations
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Image plane
starlight
Telescope pupil Resulting image
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Adaptive Optics System for Turbulence Correction
WFSFeedback
Imager
DM
Distorted wavefront
Corrected wavefront
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Image sharpening for slow changing aberrations
WFS
Feedback
Imager
DM
Distorted wavefront
Corrected wavefront
Speckle Nulling
• We need to know how the DM phase maps to the image location and intensity• To calibrate location drive the DM at the highest spatial frequency• To calibrate the intensity measure some of the spatial frequency and interpolate the
rest
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Lab Performance after Speckle Nulling
Savransky, Thomas et al., 2012
Before static wavefront correction
After static wavefront correction
Example: Gemini Planet Imager, Macintosh B.
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Image Sharpening: Ex: Electric Field Conjugation (Give’on et al. 2008, Thomas et al. 2010)
- Calculate the electric field (Ef) in the focal plane- Find the DM shape such that its effect in the plane of interest
negates the electric field present in this plane- Possible to correct both phase and amplitude
G A + Ef = 0
Actuator commands
Electric field in the focal plane
Reconstruction matrix Improves the contrast by a factor 3,
reaching 4.10^8.
The Ames Coronagraph Experiment (ACE)
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The Ames Coronagraph Experiment (ACE) Laboratory
MEMS from Boston Micromachine Corporation
On stepper and piezo stage
• Cooling system• Wavefront Control: SN, EFC, LOWFS
People and organizations partnering with ACE
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NASA ARCRuslan BelikovThomas GreeneEugene PluzhnikSandrine ThomasFred WittebornDana LynchPaul DavisEduardo BendekKevin Newman
UofAOlivier GuyonGlenn SchneiderJulien Lozi
JPLBrian KernAndy KuhnertJohn TraugerWes TraubJohn KristMarie LevineStuart ShaklanK. Balasubramanian
Lockheed MartinDomenick TenerelliRick KendrickAlan DuncanWes IrwinTroy Hix
PrincetonJeremy KasdinBob VanderbeiDavid SpergelAlexis Carlotti
L3 TinsleyJay DanielAsfaw BekeleLee DettmannBridget PetersTitus RoffClay Sylvester
STScILaurent Pueyo
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Contrast Achieved in air
Median contrast of 4.06x10-7 between 1.2 and 2 l/d Simultaneously with 8.51x10-8 between 2 and 4 l/d
Mask Inner Working Angle (IWA)=1.12 λ/dAverage over an hourSpeckle nulling, round mask
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Stability
- Contrast remains under 10-6 in the inner region and under 10-7 in the outer region for over an hour, (represented as 1500 images).
- Same performance was obtained in three independent tests.
- Reapplying a MEMS map 1-day after the correction without changing the calibration keeps the results within 10%.
=> MEMS stable and reproducible correction
Vacuum tests• We achieved the same contrast as in air, but on
a bigger zone: 1.2-12 λ/D instead of 1.2-4 λ/D• We are close to the milestone in polychromatic
(1.8e-7 at 5%, 3.2e-7 at 10% between 2 and 12 λ/D)
• Limited now by a manufacturing default of the focal plane mask (OD3 instead of OD5)
• A new mask will be manufacture for the last vacuum test, and help us achieve the milestone.
Monochromatic result
Focal plane mask
Polychromatic result with bandwidth of 5, 10, 20 and 40 %.
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Status/Next steps Milestone #1 demonstration requirement met (exceeded) in air
1.8e-7, 1.2-2.0 l/D simultaneously with 6.5e-8, 2.0-4.0 l/D
First vacuum tests started in January and are ongoing
Milestone #2 (10% broadband light) to be pursued this year
EXCEDE aggressive IWA technology development can be beneficially carried over to future larger scale coronagraphic missions with focus on exoplanets
Most of the credit goes to: J. Lozi: LOWFS, DAQ, system calibration S. Thomas: Optical design, EFC wavefront control E. Pluzhnik: Optical assembly and alignment, SN E. Bendek: CAD design and layout T. Hix and the rest of the LM team: Vacuum hardware preparation and chamber operations
Adaptation to halo beam issues
• Figure 1. Lower-dynamic-range transverse beam profile measured in Jefferson Lab’s free-electron laser injector. The blue halo intensity is about 300 (arbitrary units) less than that of the green core. Image courtesy of Pavel Evtushenko
Will need: • Contrast needed? 1e-7?• How far from the core
do you need to observe?• Which wavelength?• Dynamic range of the
detector
Potential issues:- Static and dynamic
aberrations (Stability?)- The source is resolved.- The source size varies
with time (how much?)- Noise- Mie scattering?
Christine Herman, 2001
Christine Herman, 2001 Need contrast of about 1e-4/1e-5?
Conclusion
• Similar issues are seen by your groups and coronagraphy for astronomy.
• Need a translation between astronomy and particle physics
GPI Observations of HR 4796A
Individual 60 s imagesOne linear polarization shown.Waveplate rotates 0, 22.5, 45...& the parallactic angle changes
Combined 12 minutesTotal intensity
Combined 12 minutesLinear polarized intensity
N
E0.5”