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The New Worlds Observer:

Opening Direct Study of Exo-planets Using External Occulters

Webster CashUniversity of Colorado

&The NASA Institute for Advanced Concepts

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New Worlds Contributors

Webster Cash University of ColoradoJim GreenEric SchindhelmJeremy Kasdin Princeton UniversityBob VanderbeiDavid SpergelSara Seager MITSteve Kilston Ball AerospaceTom BanksCharlie NoeckerJon Arenberg Northrop GrummanRon PolidanChuck LillieAmy LoGlenn Starkman Case WesternSally Heap Goddard Space Flight CenterMarc KuchnerKeith GendreauDon LindlerRick LyonDoug Leviton

and growing…

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Do there exist many worlds, or is there but a single world? This is one of the most noble and exalted questions in the study of Nature. St. Albertus Magnus (1206 – 1280)

scholar and patron saint of scientists

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Bringing Science FictionTo Life

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ExoplanetsThe Planets That Circle Other Stars

There are probably 10,000 within 10pc (30 light years) of the Earth. Indirect means have now found over 200.

If we can observe them directly, we will have a new field of astronomy every bit as rich as extragalactic.

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Boy Have We Got A Problem!

Courtesy of N-G

An Earth-like Planet Is 10 Billion Times FainterThan Its Parent Star

6pack vs Bill Gates entire fortune

Less Than 0.1 Arcseconds Away

One Hubble Resolution Element

AND

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Exploration & Science

One doesn't discover new lands without consenting to lose sight of the shore for a very long time. Andre Gide (1869 - 1951)

Science requires a hypothesis suggesting knowledge of the answer while exploration has no such conceit.

New Worlds is Exploration FirstScience Second

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Indirect Means

Over 200ExoplanetsNow Known

Mostly fromRadial VelocityMeasurements

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Direct Imaging is What We Want

Can We Ever Map Extra-Solar Systems In This Manner?

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Terrestrial Planet FinderMust be done from space because of the atmosphere

Telescopes must be corrected to PERFECTION – to suppress scatter: /5000 surface, 99.999% reflection uniformity

TPF is very difficult

NASA has not been good to TPF lately.They are on indefinite hold.

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TPF-ITerrestrial Planet Finder - Interferometer

Works in Mid-Infrared ~25microns

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TPF-I & DarwinMid-Infrared Interferometer

Multiple Large Cooled-IR Telescopes Combine BeamsNull Out Star at One AngleConstructive Interference at Nearby (Planet) Angle

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TPF-CTerrestrial Planet Finder - Coronagraph

Works in Visible Band

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TPF-CVisible Light Coronagraph

4x8mSpace Telescope

Starlight Stop

Planet Light

scatter

starlight

Planet light

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External Occulters

Let’s Resurrect an Old Idea– Spitzer (1962) appears to be the first

Just Keep the Starlight Out of the Telescope

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Occulter Diagram

Telescope big enough to collect enough light from planetOcculter big enough to block star

– Want low transmission on axis and high transmission off axisTelescope far enough back to have a properly small IWANo outer working angle: View entire system at once

NWD Starshade JWSTTarget Star

Planet

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New Worlds Observer

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Fly the Telescope into the Shadow

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Dropping It In

Note: No Outer Working Angle

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The Obstacle

Diffraction

Despite What They Tell You in Sixth GradeLight Does Not Move In Straight Lines

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Occulters

Several previous programs have looked at occultersUsed simple geometric shapes

– Achieved only 10-2 suppression across a broad spectral bandWith transmissive shades

– Achieved only 10-4 suppression despite scatter problem

http://umbras.org/BOSS Starkman (TRW ca 2000)

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Pinhole Camera Started this Effort With A Pinhole Camera IdeaA Pinhole Camera Meets The TPF Requirements:

Perfect TransmissionNo Phase ErrorsScatter only from edges – can be very low

Large Distance Set by 0.01 arcsec requirementdiffraction: /D = .01” D = 10m

@500nmgeometric: F = D/tan(.01”) = 180,000km

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NIACNASA Institute for Advanced Concepts

Vision Mission Proposal 2003 -- Rejected NIAC Phase I 2004 -- Accepted NGST Teams with New Worlds November 2004 – Meeting with NGST

– Pinhole Camera too Large – Can the Diffraction Problem of Occulters be Solved?

Has Anybody Applied the Princeton methodology? Beat My Head Against this Problem for the Next Five Months

SUCCESS!

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Extinguishing Poisson’s Spot

Occulters Have Very Poor Diffraction Performance– The 1818 Prediction of Fresnel led to the famous episode of:– Poisson’s Spot (variously Arago’s Spot)– Occulters Often Concentrate Light!

Must satisfy Fresnel Equation, Not Just the Fraunhoffer Equation

Must Create a Zone That Is:– Deep Below 10-10 diffraction– Wide A couple meters minimum– Broad Suppress across at least one octave of spectrum

Must Be Practical– Binary Non-transmitting to avoid scatter– Size Below 150m Diameter– Tolerance Insensitive to microscopic errors

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A Solution Exists

0A a

a 1

na

bA e

for

for

and

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Binary Shape

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Performance

A 50m diameter occulter at 50,000km will reveal Earths at 10pc

a=b=12.5mn=6F=50,000km

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Huygens-Fresnel Principle

0 ikrEE Ae dS

i r

F

s

F

s

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Fresnel Approximation

2

2 2 cos20 2

0 0

,

iksik ik sikF F

F FE e e

E e A e d di F

2

22

0 20

0

iksikikF F

FE ke e k s

E e A J diF F

Then, if circularly symmetric:

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Now, Evaluate Candidate Apodization Function

n

a

bA e

1A

22

22

0

n

n

a ika ikFbF

a

k kE e d e d

iF iF

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Dimensionless Natural Units

ka

F

kb

F

k

F

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Electric Field at Center:

22

22

0

1 1n

ii

E e d e di i

22

221

1

nii

E e e di

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Integrate by Parts

2 1

2

nni

R n e e d

Yields E = 1+R where R is small as desiredAnd

This closed-form integral represents the electric fieldat the center of the shadow

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Continue Integrating by Parts

1! 1 1 !

n

n n n

n nR

Drop Small Terms

Dominant Term

If 2 >> n

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Binary Apodization

a

b

b

a a

b

b

a

2 2 cos cos

2

0

,2

ik ik s ik s

F F F

a

kR e A e A e d d

F

Difference between petalsand circularly symmetric

apodization.

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New Code

Still Need Computer Simulations e.g. Some Disagreement about Minimum Number of Petals Direct Fresnel 2-d integral is very slow

Princeton, Goddard , NGST, CU All Working on this

new cu code– Integrate Fresnel by parts– Yields edge integral --- like Green’s Theorem– Very Fast– Will Allow Diffraction Analysis with Any Error

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Shadow of 16 Petal Mask

Linear Log

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Effect of Petal NumberPetal Profiles

Radius(m)

0 5 10 15 20 25 30 35

Log10(Suppression)

-16

-14

-12

-10

-8

-6

-4

-2

0

2

6

48

12

24

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Simulated Solar System

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Discoverer Science Simulations

Jupiter

Saturn

Exo-Zodiacal

Starshade Shadow

Earth

Mars

Jupiter

Saturn

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Suppression vs Contrast

Those Charts are Suppression The Fraction of the Total Starlight That Makes It Into the Telescope

TPF Uses Contrast The Fraction of the Total Starlight that Ends Up Under The Image of the

Planet

Within an Occulter Contrast is Suppression Convolved With Telescope Response Function Typically Contrast is 100 times Better Than Suppression

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Additional Contrast from Telescope

10-7 10-610-8

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New World Observer Architecture

After NWD Proposal Submitted NGST looked at full-up system

4m Telescope Diameter Breakpoint

Two Starshades – one small and fast

Very Powerful Scientifically

Cost comparable to other missions on table

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The First Image of Solar System

JupiterSaturn

Uranus

Neptune

Zodiacal Light

Galaxies

10 arcseconds

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90

102030

405060

7080

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Spectroscopy

R > 100 spectroscopy will distinguish terrestrial atmospheres from Jovian with modeling

O2

H2O

CH4

NH3

S. Seager

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Spectroscopic Biomarkers

Water Necessary for habitabilityOxygen Free oxygen results only from active plant lifeOzone Results from free oxygenNitrous Oxide Another gas produced by living organismsMethane Life indicator if oxygen also presentVegetation Red edge of vegetation at 750nm

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Photometry

Calculated Photometry ofCloudless Earth as itRotates

It Should Be Possible to Detect Oceans and Continents!

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NWO Science

Result of Nature interviewsMany discussions with press and other

interested parties

It is Life Seeking that EVERYBODY wants

Just finding water planets enough, but its not what motivates the public

Can there be a bigger or more important question for astronomers?

New Worlds Observer can do it $2-3 Billion and 10 years

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Implementation

No pessimist ever discovered the secret of the stars or sailed an uncharted land, or opened a new doorway for the human spirit. Helen Keller (1880 - 1968)

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Tall Poles

Deployment of 35m shade to mm class tolerance

Acquiring and holding line of sight

Fuel usage, orbits and number of targets

Stray Light – particularly solar

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Lab Studies

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Tolerance AnalysisProceeds by perturbation analysisPitch or Yaw error – foreshortened to 1- in one dimension

2

12

0

ni y

y nR n e e y dy

csRR

Reduces to:

Proving

2 2 2

22 2222

(1 )

2 2

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2 2

(1 )

2

1

n

iky ikz

F F

ikF

y z aikziky b

F F

e e dydz

kE e

iF

e e e dydz

Where z=x/(1-)

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Starshade Tolerances

PositionLateral Several MetersDistance Many Kilometers

AngleRotational NonePitch/Yaw Many Degrees

ShapeTruncation 1mmScale 10%Blob 3cm2 or greater

HolesSingle Hole 3cm2

Pinholes 3cm2 total

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Scatter ControlView Nightside

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Deployment

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Triple LayeredMicro-meteor Protection

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Alignmentacquisition & hold

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L2 Orbit Favorable

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Planning the Mission

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Earth at 200km resolution. Oceans, continents and clouds are visible.

The New Worlds Imager

Young Water PlanetJPL

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Earth Viewed at Improving Resolution

100 km300 km3000 km 1000 km

TRUE PLANET IMAGING

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Solar System Survey at 300km Resolution

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NWI Concept

1500km

starshades

collector craft

combiner

50,0

00km

1500km

planet collimator

field star collimator

primary collector

to combiner

planet collimator

field star collimator

primary collector

to combiner

planet beams

field star beams

Delay Lines – Mixers - Detectors

planet beams

field star beams

Delay Lines – Mixers - Detectors

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Sims

Established that information is presentin the fringes and detectable.

How do we invert into images?Is this enough?

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Hypertelescope Problem

How Many Apertures Needed? One per pixel (no!)

Cost control of multiple craft

Formation Flying to Tolerance

Labeyrie has worked on this Amazing telescope even without starshades

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Conclusion By 2025

O2

H2O

By 2013

There is nothing in the above missionthat the people in this room could notimplement today.

Money for such a missionwill be available in twoyears. This is an obviouscandidate.