Imaging Exoplanets with Advanced HighContrast Imaging Instrumentation onLarge OIR Telescopes
Olivier Guyon
University of Arizona
Subaru Telescope
NINS Astrobiology Center (Japan)

Spectacular discoveries aroundnearby stars
Trappist-1 system
7 planets~3 in hab zone
likely rocky
40 ly away

Proxima Cen b planet
Possibly habitable
Closest star to our solar
system (only 4.2 lightyears away)Why should we image planets ?
Imaging allows spectroscopy tomeasure atmosphere composition
Woolf et al.

Spectrum of Earth (taken by lookingat Earthshine) shows evidence forlife and plants

Taking images of habitable exoplanets: Why is
it so hard ?

Adaptive Optics

C. Max, Center for Adaptive Optics

Laser Tomography
AO (LTAO)

Narrow field
LGS in near-IR

100 nmNarrow fieldvisible AO

10 nm 0”10”Multi Object
AO (MOAO)

Optics size, optical layout complexity

Need more
photons

High contrast“Extreme-AO”

OKM
D1dedeen
M
D1>

Multi Conjugate
AO (MCAO)

AO loop speed

1g>
uidus 1 gesua u i dt arlly e
als sta
OKo >r n
1 LeedG S edNarrow fieldNGS in near-IR# of DM actuators# of WFS elements

Wavefront Error (nm)Easier“Low order AO”

Ground-layer
AO

Field of view 1’Cgnign
halle
7Extreme Adaptive Optics

Subaru Telescope (8.2m diameter) has an exoplanet-imaging instrument (SCExAO)
The instrument team is developing advanced Extreme-AO techniques
Subaru Telescope, Mauna Kea, Hawaii
4200m altitude
Very clear sky

Best snow in Hawaii
Regular size door

Subaru Telescope (view from inside dome)

Photograph by Enrico SachettiImaging exoplanets requires 3 techniques to be combined:(1) Extreme-AO corrects atmospheric turbulence(2) A coronagraph masks the light of the bright star(3) Smart image processing to recognize planets
Simulated images below show how
Extreme-AO and Coronagraphy
deliver high contrast image of astar

Raw on-sky image
Subaru Telescope/SCExAO

(3)
(1)

(2)

HR8799 system (b,c,d)
Subaru Telescope/SCExAO

Pyramid WFS

On-sky camera images (snapshot)
SCExAO example
Visible image (left), NearIR image (center), Visible pyramid WFS (right)

Star: Sigma Ori, 0.3” separation

AO loop runs at 0.5 kHz to 3.5 kHz
14,400 sensors → 2000 actuators

Stable near-IR PSF (H band shown here)

Achieves visible light diffraction
limit under good seeing(750nm PSF shown here)

Capella36mas separation

HR8799 system
Four planets, orbital periods on the order of 100yr
Each planet 5 to 7 Jupiter Mass

The central bright star is missing
from the image: it has beensuccessfully blocked by ouroptics, and removed by image
processing

Subaru Telescope/ SCExAO (data reduction: T. Currie)

AB Aur b protoplanet
Planet is still forming from gravitational collapse of gas cloud
Mass ~ 9x Jupiter

Subaru Telescope/ SCExAO (T. Currie et al. 2022)

Thirty
MeterTelescope

Giant Magellan TelescopeEuropean
ExtremelyLarge
Telescope

Contrast and Angular separation

M-type stars

log10 contrast

K-type stars

G-type stars
1 Re rocky planets in HZ forstars within 30pc (6041 stars)

F-type stars

Contrast and Angular separation
1 λ/D
λ=1600nm
D = 30m

1 λ/D
λ=1600nm
D = 8mAround about 50 stars (M type), rockyplanets in habitable zone could be
imaged and their spectra acquired[assumes 1e-8 contrast limit, 1 l/DIWA]
K-type and nearest G-type stars are morechallenging, but could be accessible if
raw contrast can be pushed to ~1e-7(models tell us it's possible)

M-type stars

log10 contrast

1 λ/D
λ=10000nm
D = 30m

K-type stars

Space-based observatories
observing in visible andnear-IR light

1 Re rocky planets in HZ forstars within 30pc (6041 stars)

Thermal emission from habitable
planets around nearby A, F, G typestars is detectable with ELTs

G-type stars
F-type stars

TMT Planetary Systems
Imager (PSI)
Northern Hemisphere
Broad wavelength coverage & spectroscopy
Input
PSI-Blue

PSI-Red

XAO

PSI-10Common Path AO
Vis WFS

NIR WFS
DM

Coronagraph

MODHIS
Coronagraph

Fibers>4.5 μm

Coronagraph
2.5-4.5<2.5 μm>0.95 μm

Cold>8 μm<1.8 μm
Cold<0.95 μm

0.6-1.8 μm
R = 50 IFU
ImagerPolarimeter

CommonDM

2-5 μmR = 50-5k IFU
Imager

0.6-0.95 μm
R = 100k
High-res.
Spectrograph8-13 μm
R ~ 30 IFU

0.95-2.4 μm
R = 100k
High-res.
Spectrograph
2.8-5.3 μm
R = 100k
High-res.
SpectrographI band: 24 planets

H band: 38 planets

J band: 48 planets

K band: 28 planets

I band: 24 planets

H band: 38 planets

J band: 48 planets

K band: 28 planets

AO & Infrastructure
Upgrades atSubaru TelescopeMajor upgrades are bringing SCExAO closer to TMT-PSI
Upgrades to 1st stage AO correction will boost performance:[spring 2023] 1st stage Deformable Mirror: 188 elements → 3228 elements
Validating DM technology envisioned for TMT-PSI[spring 2023] Adding high-order NearIR wavefront sensing[late 2023] Adding 1st stage high order visible WFS

Infrastructure:[2024] Beam switcher → easier operation + supports advanced modes[2023+] Laser tomographic AO → access to fainter sources[2026+] Adaptive Secondary Mirror

Kyoto3DII
AO3k

IRCS

SPIDERSNINJASCExAO
MEC
MEC
readout
electronics

BeamSwitcher
CHARIS

Advanced Control
Techniques for Extreme AO

Phase Diversity / Curvature WFS:
Reconstruction Simulation
20,000 ph total: 609nm → 34.4nm RMS

non-linear Curvature WFS:
AO loop Simulation

Computer Simulations
showing contrast gain
with high sensitivity
WFS (non-linearcurvature)m ~ 13

Predictive Control and Sensor Fusion
Conventional AO:
Measured RM/CM

Advanced AO control:
Using past measurements (predictivecontrol) and other measurements (sensorfusion) → control matrix is very big, andusually impossible to measure
We derive CM from WFS(s) telemetry

Conventional AO would have control matrix= 100 x 100 Identity matrix
Last WFS
measurement

WFS
measurement
Step -1

WFS
measurement
Step -2

WFS
measurement
Step -3

Predictive control adds
blocks to control matrix(a)Predictive Control
2kHz, target #1(b)

1kHz, faint source(c)2kHz, target #2
(e)

(d)

Off-diagonal elements
capture cross-coupling
between modes

Machine Learning based predictive control
First on-sky results (2 kHz, 50 sec update)→ 2.5x raw contrast improvement

OFF (integrator, gain=0.2)

ONImproved Image Stability

OFF (integrator, gain=0.2)

ONUsing Focal Plane Image for AO

Electric Field Conjugation(K. Ahn, 2021)

Improving Image Quality by “Learning” from Focal PlaneImage

Evolution of the on-sky PSF before running the algorithm, after the first iteration,and the after last iteration. Each image is 0.25 arcsec (40x40 pixels) across,acquired at λ = 750 nm, 30 sec exposure time (computed by co-addition of 15,000
frames acquired at 500 Hz)
Skaf et al. 2022

Self-CalibratingHigh Contrast Imaging

Principle

Why is Post-processing calibration better than AO control ?

Encouraging work: Neural Net PSF
reconstruction

Credit: Barnaby Norris & Alison Wong

Focal plane high contrast
areaDH

Focal plane image brightfieldWFS

Experimental validation (lab)1550nm, 25nm BW, Lyot Coronagraph, 7 kHz frame rate
UNCALIBRATEDCALIBRATED

30x gain in speckle variance

Variance(RON+ PHN removed)

Average(dark removed)

UNCALIBRATED
All frames (N = 60,000)

CALIBRATED
128-samplecluster

DH area

Input sensingarea

DH area :σ2all/σ2cluster = 30.7

Input sensing area :σ2all/σ2cluster = 35.7

Photonic NullingInterferometric WFSs

Credit: S. Vievard and V. Deo
On-sky demonstration of interferometric WFS→ provides path to high sensitivity chromatic WF measurement

Key advantages:
Access to very small
separation (better thancoronagraphy)
High sensitivity
wavefront sensing
integrated within chipSpectroscopy at output“Astrophotonics: The Rise of Integrated Photonics in Astronomy”
Norris & Bland-Hawthorn.
Optics and Photonics News (2019)https://www.osa-opn.org/home/articles/volume_30/may_2019/features/astrophotonics_the_rise_of_integrated_photonics_in/GLINT module @ Subaru/SCExAOGLINT module @ Subaru/SCExAO
Null output: starlight is almost
completely removed by destructive
interference, providing deep contrast.
➔This is where planet light andspectra are extracted
Fringe tracking output: Brightstarlight interference efficiently encode
residual small (nm-level) opticalaberration➔Feed this information in real-time to
upstream deformable mirror forcorrection➔Use this information to calibrate howmuch starlight is left in null outputs“Scalable photonic-based nulling interferometry with the dispersed
multi-baseline GLINT instrument”
Martinod, Norris, Tuthill...Guyon et al.
Nature Communications (2021)
link: https://www.nature.com/articles/s41467-021-22769-x

Uncalibrated
average

std dev

Photometry #1

Null #1 (B=5.5m)
Anti-null #1

Null #4 (B=2.15m)

Anti-null #41340 nm

1.4 kHz frame
rate

Photometry #21690 nm

GLINT – on-sky
Alpha Boo

Calibratedaveragestd dev

Conclusions
We are already on the path to imaging habitable planets with 30m-class telescopes.
Habitable planets around nearby M and K type stars are most accessible for
imaging and spectroscopy.
Spectra will be acquired in visible and NearIR.

SCExAO is leading the way in prototyping key technologies on this path – andenabling new science along the way.
Rapidly evolving technology landscape – important to keep up and validate on-sky.
SCExAO is an open research platform → please consider joining/collaborating
Email me at: guyon@naoj.org