1. High-Contrast Imaging and the Direct Detection of Exoplanets
Sandrine Thomas, Ruslan Belikov, and many collaborators
Image of alpha cen

2. Is there another Earth out there?
The question that we are trying to answer is nothing less than is there another Earth out there?
Is there another Earth out there?
Is there life on this over Earth? 2

3. Requirements for habitability
not habitable
(too large, hydrogen gas does not escape)
habitable
not habitable
(too small to keep oxygen and water)
Planet size:
~ 0.5 – 2 Earth size
Temperature:
0-100 C
Biomarkers:
water and oxygen
Credit: Petigura/UC Berkeley, Howard/UH-Manoa, Marcy/UC Berkeley
H2O
(Water) O2
(Oxygen)
(Schematic representation only)

4. Spectroscopy: detecting biomarkers
Ref: R. Hanel, GSFC O2
Iron
oxides
CO2
H2O
EARTH-CIRRUS
VENUS
X 0.60
MARS
EARTH-OCEAN
H2O ice O3
Use either this slide or previous, depending on expected technical level of audience
Detecting atmospheric oxygen and water likely indicates life
(because very few non-biological processes can sustain an oxygen atmosphere)

5. Why Direct Planet Detection?
How do planetary systems form and evolve?
Which stars have planetary systems?
What mechanism(s) create Jovian planets (accretion, migration, disk instability)
How does dynamical evolution redistribute these planets?
Physics of planets
Planetary atmospheres
Unexplored regime of 120 K < T < 600 K
Domain of NH3 & H2O & clouds
Just mention here about the different techniques: radial velocity, transits, microlensing, wabbling

6. 861 confirmed planets (677 planetary systems)
2740 planet candidates (from Kepler mission)
(Wobble method #2: Astrometry)
Wobble method #1: Radial Velocity
Astrometry: from 10pc away
Direct detection

7. Direct Imaging Main 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

8. Beyond Kepler: Direct imaging missions
2010
2020
2030
Kepler
Exo-C/S or AFTA
(~1.4m / 2.4m,
$1B / $2B+)
New Worlds
Telescope
($4-8m, $4B+)
Small sats
( m,
~$5 – 200M)
Earth-size
Habitable zone
Spectroscopy
Two stars: aCen
Earth-size
Habitable zone
No spectroscopy (biomarkers)
Not nearby systems
Another Earth?
Earth-size
Habitable zone
Spectroscopy
~6-20 stars
Earth-size
Habitable zone
Spectroscopy
~100s of Earths
Simulation of an exo-Earth around aCen
with a $1B mission (1.5m telescope)
All these missions also do ground-breaking science on non-habitable planets

9. Ground based Instruments: Exoplanet direct imaging instruments
GPI
SPHERE
Macintosh et al, 14
Beuzit et al, 14
P1640
SCExAO
Hinkley et al, 08
Guyon et al, 10

10. 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

11. 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
5 nm RMS non-common path WFE
1 nm RMS non-common path WFE

12. Solutions Diffraction: Coronagraphs
Aberrations: Active and adaptive optics
Wavefront sensor : Shack-Hartmann, curvature sensors
Deformable mirror
Control software
DM system
Coronagraph
Science
camera
WFS
Starlight rejected
by coronagraph
feedback
Diagram of a direct imaging instrument
from
telescope

13. The Lyot Coronograph Sivaramakrishna, 2001

15. Principle of Pupil Apodization-type coronagraphs
Image plane
starlight
Telescope pupil
Resulting image

16. Apodizer manufacture: halftone technique using black chrome microdots
The apodizer transmission is obtained by randomly distributing 2μm square dots over the glass.
by JenOptiks.

17. The Apodized Lyot coronagraph
Aime et Al. 2001
Pupil plane
Focal plane
Lyot stop
Image

18. Challenge #2: optical aberrations
Image plane
starlight
Telescope pupil
Resulting image

19. Adaptive Optics System for Turbulence Correction
Distorted wavefront
Corrected wavefront
Imager DM
WFS
Feedback

20. Image sharpening for slow changing aberrations
Distorted wavefront
Corrected wavefront
Imager DM
WFS
Feedback

21. 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

22. Lab Performance after Speckle Nulling
Before static wavefront correction
Example: Gemini Planet Imager, Macintosh B.
Savransky, Thomas et al., 2012
After static wavefront correction

23. Image Sharpening: Ex: Electric Field Conjugation (Give’on et al
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.
ONLY A FACTOR OF 3 ?? LOOKS BIGGER IN YOUR PLOT

24. Beta Pictoris b with GPI
Combined 30-min GPI image of Beta Pictoris. The spectral data have been median-collapsed into a synthetic broadband 1.5–1.8 μm channel. The image has been PSF subtracted using angular and spectral differential techniques. Beta Pictoris b is detected at a signal-to-noise of ∼ 100.
Gemini Planet Imager
Gemini NICI (Boccaleti et al)
1980 seconds
3952 seconds

25. Contrast vs. angular separation at H (1
Contrast vs. angular separation at H (1.6 μm) for a PSF-subtracted 30- min GPI exposure. Contrast is shown for PSF subtraction based on either a flat spectrum similar to a L dwarf or a methane-dominated spectrum (which allows more effective multiwavelength PSF subtraction.) For com- parison, a 45-min 2.1-μm Keck sequence is also shown. (Other high-contrast AO imaging setups such as Subaru HiCIAO, Gemini NICI, and VLT NACO have similar performance to that of Keck.)
0.4 arcsec = 10 lambda/d

26. The Ames Coronagraph Experiment (ACE)

27. The Ames Coronagraph Experiment (ACE) Laboratory
Cooling system
Wavefront Control: SN, EFC, LOWFS
Not as mature => labs
MEMS from Boston Micromachine Corporation
On stepper and piezo stage

28. People and organizations partnering with ACE
UofA
Olivier Guyon
Glenn Schneider
Julien Lozi
L3 Tinsley
Jay Daniel
Asfaw Bekele
Lee Dettmann
Bridget Peters
Titus Roff
Clay Sylvester
NASA ARC
Ruslan Belikov
Thomas Greene
Eugene Pluzhnik
Sandrine Thomas
Fred Witteborn
Dana Lynch
Paul Davis
Eduardo Bendek
Kevin Newman
Princeton
Jeremy Kasdin
Bob Vanderbei
David Spergel
Alexis Carlotti
STScI
Laurent Pueyo
JPL
Brian Kern
Andy Kuhnert
John Trauger
Wes Traub
John Krist
Marie Levine
Stuart Shaklan
K. Balasubramanian
Now, how hard is this problem?
Lockheed Martin
Domenick Tenerelli
Rick Kendrick
Alan Duncan
Wes Irwin
Troy Hix

29. 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/d
Average over an hour
Speckle nulling, round mask

30. Stability => MEMS stable and reproducible correction
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

31. Vacuum tests
Monochromatic result
We achieved the same contrast as in air, but on a bigger zone: λ/D instead of 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.
Focal plane mask
Polychromatic result with bandwidth of 5, 10, 20 and 40 %.

32. Status/Next steps
Milestone #1 demonstration requirement met (exceeded) in air
1.8e-7, l/D simultaneously with 6.5e-8, 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

33. Adaptation to halo beam issues
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?
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
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
Christine Herman, 2001

34. Need contrast of about 1e-4/1e-5?
Christine Herman, 2001

35. Conclusion
Similar issues are seen by your groups and coronagraphy for astronomy.
Need a translation between astronomy and particle physics

36. GPI Observations of HR 4796A
0.5” E
Individual 60 s images
One linear polarization shown.
Waveplate rotates 0, 22.5, & the parallactic angle changes
Combined 12 minutes
Total intensity
Combined 12 minutes
Linear polarized intensity
Slide by Marshall Perrin