Beyond Kepler: Direct Imaging of Earth-like Planets

Rus Belikov

NASA Ames Research Center

Tri-Valley Stargazers, May 15, 2015

• History and science• Technology• Ames Coronagraph Experiment

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Is there another Earth out there?

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Is there life on it?

“There are infinite

worlds both like and

unlike this world of

ours...We must

believe that in all

worlds there are living

creatures and planets

and other things we

see in this world.”

Epicurius

c. 300 B.C

Thousands of years ago, Greek philosophers speculated.

4

Some gave their lives…

” There are countless suns and countless earths all rotating around their suns in exactly the same way as the seven planets of our system. We see only the suns because they are the largest bodies and are luminous, but their planets remain invisible to us because they are smaller and non-luminous. The countless worlds in the universe are no worse and no less inhabited than our Earth”

Giordano Bruno

in De L'infinito

Universo E Mondi, 1584

In 1995, a breakthrough:

the first planet around another star.

A Swiss team discovers a planet – 51 Pegasi –

48 light years from Earth.

Artist's concept of an extrasolar planet (Greg Bacon, STScI)7

Didier Queloz and Michel Mayor

And then the discoveries started rolling in:

“First new solar system discovered”USA TODAY

April 16, 1999

“10 More Planets Discovered”Washington Post

August 6, 2000

“New Planet Seen Outside Solar System ”New York Times

April 19, 1996

5,450 Exoplanets (candidates and confirmed)1,838 confirmed planets (1,132 planetary systems)

Wobble method #1: Radial Velocity (Wobble method #2: Astrometry)

Direct detection

The Transit Method

Credit: Amir Give'on and Daphna Wegner

You can see transits within our Solar System!

Next Venus transit: 2117 December 10–11

Transit of Venus, June 5th, 2012

Overexposed and processed image

atmosphere

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The Kepler MissionThe Kepler Mission

http://kepler.nasa.gov/

A Search for Earth-size PlanetsExoplanet Detections, 1995-2013

Rad

ius

Rel

ativ

e to

Ear

th

Orbital Period in daysBatalha, 2014

A Search for Earth-size PlanetsSmall HZ Planet Candidates (in progress)

Kepler exoplanet statistics: narrowing in on ηEarth

Fressin et. al. 2012

(Debiased) Planet occurrence with size

�� There are a lot of planets, at least as many as there are starsThere are a lot of planets, at least as many as there are stars�� Consistent with independent result from microlensing (Villard etConsistent with independent result from microlensing (Villard et. al. 2012). al. 2012)

�� There are many more small planets than large planetsThere are many more small planets than large planets�� Many potentially habitable candidates have been announced (but Many potentially habitable candidates have been announced (but ηηEarth Earth has not yet has not yet

been officially determined)been officially determined)�� ηηEarth Earth for Sunfor Sun--like stars have ranged from 10 like stars have ranged from 10 -- 60%. 60%.

Dong & Zhu et. al. 2013

(Debiased) Planet occurrence with period

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The Direct Imaging method

�� Keck / Gemini , AO and Keck / Gemini , AO and ADI in infrared, Nov. ADI in infrared, Nov. 2008, 2008, Christian Marois Christian Marois et. al. et. al.

�� 60 million years, 24, 38, 60 million years, 24, 38, 68 a.u.; 10, 10, 7 Jupiter 68 a.u.; 10, 10, 7 Jupiter massesmasses

HR8799 (2008) Fomalhaut (2008)Beta Pictoris (2008)

�� VLT, VLT, Anne-Marie Lagrange et. al., Nov 2008.

�� 12 million years, 8 12 million years, 8 Jupiter masses, 8 a.u. Jupiter masses, 8 a.u. 1500K1500K

�� Hubble, visible light, Hubble, visible light, Paul Kalas et. al., Nov 2008.

�� 200 million years, 0.054200 million years, 0.054--3 Jupiter masses, 115 3 Jupiter masses, 115 a.u. 1500Ka.u. 1500K

Solar system size comparison

�� 28 Planetary systems directly imaged to date 28 Planetary systems directly imaged to date �� 32 Planets, 2 multiple32 Planets, 2 multiple--planet systemsplanet systems�� Some of these may not be planetsSome of these may not be planets�� (source: exoplanet.eu)(source: exoplanet.eu)

Solar system vs. FomalhautSolar system vs. Fomalhaut

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1818

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What does the Solar System look like What does the Solar System look like from far away?from far away?

Credit: Cassini mission

2020

�� Feb 14, 1990Feb 14, 1990�� 6 light6 light--hours (4 billion miles away)hours (4 billion miles away)�� Nearest star (Alpha Cen) is 4.2 light YEARS away (2.5 trillion mNearest star (Alpha Cen) is 4.2 light YEARS away (2.5 trillion miles away)iles away)�� Earth is ~10Earth is ~101010 times (25 magnitudes) dimmer than the Sun, and would appear ~ times (25 magnitudes) dimmer than the Sun, and would appear ~

0.80.8”” away for Alpha Cenaway for Alpha Cen

What does the Solar System look like What does the Solar System look like from far away?from far away?

Credit: Voyager mission

Earth twin simulations around aCenEarth twin simulations around aCen(if we could block the second star)(if we could block the second star)

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α Cen Earth twin image simulation

1.5m aperture, 1 hour exposure

1.4m telescope 0.3m telescope

Photometry (can determine length of day, surface type, weather)

E. B. Ford, S. Seager & E. L. Turner, Nature, 2001

O2

Iron oxides

CO2

H2O H2O

CO2

EARTH-CIRRUS

VENUSX 0.60

MARS

EARTH-OCEAN

H2O H2O

H2O ice

O3O2

Spectroscopy: detecting biomarkersSpectroscopy: detecting biomarkers

Detecting atmospheric oxygen and water likely indicates life(because very few non-biological processes can sustain an oxygen atmosphere)

Red EdgeRed Edge

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Seager et al. 2005; Data from Middleton & Sullivan 2000

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Direct ImagingDirect ImagingMain Engineering RequirementsMain Engineering Requirements

�� ContrastContrast�� ~10~101010 for Earthfor Earth--like planetslike planets�� ~10~1077 for young hot planets and disksfor young hot planets and disks

�� Inner Working AngleInner Working Angle�� The smaller the better!The smaller the better!�� Typically 1Typically 1--3 3 λλ/D required on missions/D required on missions

Stars are a billion times brighter…

…than the planet

…hidden

in the glare.

Like this firefly.

3 Main Technological 3 Main Technological ChallengesChallenges

1. Funamental physics: Diffraction1. Funamental physics: Diffraction

2. Manufacturing limitations: Optical aberrations2. Manufacturing limitations: Optical aberrations

3. Environmental limitations: Mechanical Stability3. Environmental limitations: Mechanical Stability

DM system CoronagraphScience camera

fromtelescope

LOWFS Starlight rejectedby coronagraph

feedback

Diagram of a direct imaging instrument

feedback

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3131

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Starshade Light fromtelescope

Deformable

mirror

Cor

onag

raph

to

rem

ove

star

light

imager

planet

Leftover starlight

Coronagraph

See http://exep.jpl.nasa.gov/coronagraphvideo/ for a video explaining the principle of operation

See https://www.youtube.com/watch?v=gC7pjlCKZe4 for a video explaining the principle of operation

Direct ImagingDirect Imaging

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Many different solutions to diffraction Many different solutions to diffraction (coronagraphs)(coronagraphs)

Courtesy of James Lloyd

The Ames Coronagraph Experiment (ACE)The Ames Coronagraph Experiment (ACE)

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Testbeds and PIAA hardwareTestbeds and PIAA hardware

Ruslan Belikov, NASA Ames Coronagraph LaboratoryRuslan Belikov, NASA Ames Coronagraph Laboratory

ACE testbed

Lockheed Martin

JPL

PIAA lenses

PIAA mirrors

State of the art performance in the lab

Deformable mirror

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Principle of Pupil ApodizationPrinciple of Pupil Apodization--type type coronagraphscoronagraphs

Image plane

starlight

Telescope pupil Resulting image

Blocking the star: the PIAA CoronagraphBlocking the star: the PIAA Coronagraph(phase(phase--induced amplitude apodization)induced amplitude apodization)

Focal planeOriginal uniformly

illuminated pupil plane

New, apodized pupil plane Focal plane

Ruslan Belikov, NASA Ames Coronagraph LaboratoryRuslan Belikov, NASA Ames Coronagraph Laboratory

�� PIAA is a powerful technology to block the star in PIAA is a powerful technology to block the star in order to reveal planetsorder to reveal planets

�� Successful track of technology development at Successful track of technology development at Ames over the past 6 years (as well as at partner Ames over the past 6 years (as well as at partner institutions)institutions)

�� One of the potential architectures selected by One of the potential architectures selected by NASA for the ExoNASA for the Exo--C and AFTA missionsC and AFTA missions

Tau CetiAlpha Centauri A

Courtesy of K. Cahoy

ExoEarth direct image simulations, 1.5m telescope with PIAA

Another Earth?

ACE Optical LayoutACE Optical Layout

Ruslan Belikov, NASA Ames Coronagraph Laboratory

Boston MicromachinesDeformable mirror (32x32)

Wavefront control usesa combination ofEFC (Give’on et al. 2007)and Speckle Nulling

Broadband-capable PIAA mirrorsmade by L-3 Tinsley

LOWFSCCD

Focal plane occulter

LOWFS

and broadband

Initial Images from the LabInitial Images from the Lab

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Challenge #2: Challenge #2: optical aberrationsoptical aberrations

Image plane

starlight

Telescope pupil Resulting image

LOWFSCCD

Focal plane occulter

LOWFS

and broadband

Solution: use a deformable mirrorSolution: use a deformable mirror

�� Made by Boston Micromachines, 32x32 actuators, 10mm active areaMade by Boston Micromachines, 32x32 actuators, 10mm active area

Ruslan Belikov, NASA Ames Coronagraph LaboratoryRuslan Belikov, NASA Ames Coronagraph Laboratory

Challenge #3: StabilityChallenge #3: Stability

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Ruslan Belikov, NASA Ames Coronagraph Laboratory

��Light rejected by the coronagraphic mask is Light rejected by the coronagraphic mask is collected for the LOWFScollected for the LOWFS��A lens reimages the PSF on a fast cameraA lens reimages the PSF on a fast camera��A controller grabs images, calculates modes (tip/tilt A controller grabs images, calculates modes (tip/tilt upstream and downstream the PIAA, focus, upstream and downstream the PIAA, focus, ……))��Commands are send to actuators (tip/tilt mirrors, Commands are send to actuators (tip/tilt mirrors, piezo stages, piezo stages, ……))��Correction of 2 modes: tip/tilt upstream the PIAACorrection of 2 modes: tip/tilt upstream the PIAA��2 actuators: X and Y translation of the source with 2 actuators: X and Y translation of the source with piezospiezos��RealReal--time controllertime controller

•• 450 Hz maximum frequency in closed450 Hz maximum frequency in closed--looploop•• 1100 Hz in open1100 Hz in open--loop (vibration analysis)loop (vibration analysis)

LOWFSCCD

Focal plane occulter

LOWFS

and broadband

Fast camera1100 Hz maximum14 bits/pixelLow noise

Performance of the LOWFSPerformance of the LOWFS

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�� The vibration analysis, coupled with The vibration analysis, coupled with accelerometers, helped us to identify accelerometers, helped us to identify contributorscontributors

�� The controller removes mostly The controller removes mostly residual turbulence below 1 Hzresidual turbulence below 1 Hz

�� We will try to reduce vibrations, We will try to reduce vibrations, especially on the y axis, between 10 especially on the y axis, between 10 and 150 Hzand 150 Hz

�� Residue:Residue:

�� OpenOpen--loop: 6x10loop: 6x10--33 λλ/D/D

�� ClosedClosed--loop: loop: 2.5x102.5x10--33 λλ/D/D

�� Since we installed the LOWFS, the Since we installed the LOWFS, the contrast improved by a decadecontrast improved by a decade

CAD modelCAD model

Eduardo Bendek, NASA Ames Coronagraph ExperimentEduardo Bendek, NASA Ames Coronagraph Experiment

0 1 2 3 4

10-10

10-8

10-6

IWA ( λ/D)

Con

tras

t

ResultsResults

Ruslan Belikov, NASA Ames Coronagraph

Laboratory

9.25e-009, 2.2 - 3.2 l/D

-2 0 2

-3

-2

-1

0

1

2

3

-8

-7.5

-7

-6.5

-6

-5.5

-5

1.9e-8, 2.0-3.4 λ/D655nm

1.8e-7, 1.2-2.0 λ/D6.5e-8, 2.0-4.0 λ/D655nm

HBLC (HCIT, 2013)

Stable point source limit

0.001 λ/DTip/tilt errors

0.01 λ/DTip/tilt errors

Theoretical limits

PIAA (ACE, 2013)

PIAA (HCIT, 2013)

VVC4 (HCIT 2013)

-4 -2 0 2 4

-4

-3

-2

-1

0

1

2

3

4

5-8

-7.5

-7

-6.5

-6

-5.5

-5

-4.5

-4

6e-6, 1.2-2.0 λ/D10% BB @ 655nm

Preliminary resultLimited by auxiliaryReimaging optics

VVC4 (HCIT 2013)VNC(GSFC, 2013)

Video lab tourVideo lab tour

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http://gizmodo.com/5896588/the-lens-well-look-through-to-find-a-new-earth

Selected future space missions and concepts Selected future space missions and concepts

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2010 2020

Kepler

2030

Exo-C/S or AFTA(~1.4m / 2.4m,$1B / $2B+)

NWT / LUVOIR /ATLST(4+m, $4B+)

Small sats(0.25-0.7m,~$10 – 200M)

Earth-sizeHabitable zoneNo spectroscopyNot nearby systems

Earth-sizeHabitable zoneSpectroscopy>100 stars

Earth-sizeHabitable zoneSpectroscopy~6-20 stars

Direct imaging oflarge planets

Transit spectroscopy(Habitable planets unlikely)

JWST

Earth-sizeHabitable zoneSpectroscopyTwo stars: αCen

Highlighted effort: ACESatHighlighted effort: ACESat

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45cm space telescope

Capable of directly imaging Earth-like planets around Alpha Centauri

Submitted to NASA’s SMEX program in Dec 2014

ACESat data simulationACESat data simulation

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After filtering:

After shift-and-add

“Venus” “Earth” “pMars”

�� Simulation parameters (ACESat mission)Simulation parameters (ACESat mission)�� D = 45cmD = 45cm�� PIAA coronagraph PIAA coronagraph �� 1e1e--8 starting contrast (assumed after MSWC)8 starting contrast (assumed after MSWC)�� 0.5mas (10.5mas (1σσ rms) random tip/tilt jitterrms) random tip/tilt jitter�� 5 color filters5 color filters�� 22--year missionyear mission�� Photon noise included (dominates over read)Photon noise included (dominates over read)

Note: “pMars” is largerbut farther away than Solar Mars

Simulations by Jared Males

FutureFuture

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Personal Vision of EarthPersonal Vision of Earth--like like planet exploration pathplanet exploration path

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2010 2020

• Disk Science• Science precursor• Technology precursor• Retiring key risks of

ExoEarth imaging• aCen exo-Earth imaging

• Potentially Habitable Planets (Earth size, Earth T)

• Statistics

Kepler Small coronagraph(and/or other <2.4m telescopes)

2030Life-finder(Large imager flagship)

• ExoEarth imaging• Spectral

Characterization• Biomarker detection

20??

Planet resolver Interstellar probes

2???

Geoff Marcy: “Probe to Alpha Centauri, before this century is out”

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ConclusionsConclusions�� ExoExo--earth imaging is within reach. (Around earth imaging is within reach. (Around

Alpha Centauri within a decade or around Alpha Centauri within a decade or around other stars within ~2 decades.)other stars within ~2 decades.)

�� Remote detection of life is possible through Remote detection of life is possible through biomarkersbiomarkers

�� High contrast labs are developing High contrast labs are developing coronagraphic technology to help us reach coronagraphic technology to help us reach the goal of exothe goal of exo--earth imaging.earth imaging.