1

The New Worlds Observer:

Opening Direct Study of Exo-planets Using External Occulters

Webster CashUniversity of Colorado

&The NASA Institute for Advanced Concepts

2

New Worlds Contributors

Webster Cash University of ColoradoJim GreenPhil OakleyJeremy Kasdin Princeton UniversityBob VanderbeiDavid SpergelSara Seager MITSteve Kilston Ball AerospaceCharlie NoeckerJon Arenberg Northrop GrummanRon PolidanChuck LillieAmy LoTiffany GlassmanGlenn Starkman Case WesternSally Heap Goddard Space Flight CenterMarc KuchnerKeith GendreauDon LindlerRick LyonDoug LevitonAki RobergeMaggie Turnbull STScIGiovanna Tinetti University College London

and growing…

3

ExoplanetsThe Planets That Circle Other Stars

There are probably 1000 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.

4

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

5

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

6

Indirect Means

Over 200ExoplanetsNow Known

Mostly fromRadial VelocityMeasurements

7

Direct Imaging is What We Want

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

8

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.

9

TPF-ITerrestrial Planet Finder - Interferometer

Works in Mid-Infrared ~25microns

10

TPF-I & DarwinMid-Infrared Interferometer

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

11

TPF-CTerrestrial Planet Finder - Coronagraph

Works in Visible Band

12

TPF-CVisible Light Coronagraph

4x8mSpace Telescope

Starlight Stop

Planet Light

scatter

starlight

Planet light

13

External Occulters

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

Just Keep the Starlight Out of the Telescope

14

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

15

New Worlds Observer

16

Fly the Telescope into the Shadow

17

Dropping It In

Note: No Outer Working Angle

18

The Obstacle

Diffraction

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

19

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)

20

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

21

A Solution Exists

( ) 0A ρ = aρ <

aρ >( ) 1

na

bA eρ

ρ−⎛ ⎞−⎜ ⎟

⎝ ⎠= −

for

for

and

22

Binary Shape

23

Performance

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

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

24

Huygens-Fresnel Principle

25

Continue Integrating by Parts

Drop Small Terms

Dominant Term

If 2 >> n

26

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

27

Shadow of 16 Petal Mask

Linear Log

28

Simulated Solar System

Most of the followingsimulations are fromPhil Oakley

29

Additional Contrast from Telescope

10-7 10-610-8

30

The First Image of Solar System

JupiterSaturn

Uranus

Neptune

Zodiacal Light

Galaxies

10 arcseconds

31

90

102030

405060

7080

32

Discoverer Science Simulations

Jupiter

Saturn

Exo-Zodiacal

Starshade Shadow

Earth

Mars

Jupiter

Saturn

33

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

34

Spectroscopy

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

O2

H2O

CH4

NH3

S. Seager

35

Venus (bright spot) and Earth (dimmer spot) inclinations: 0,30,60,90

12

34

36

Just Earth (left). Earth from Voyager (right)

37

Brightness Profiles

0.5

0.95

38

Photometry of the Earth

39

A Year of Watching the Earth

Simulated Photometric Data Including Instrument Effects and Statistics

40

Best Inversion for a cloudless planet

41

Best case inversion for a cloudy Earth(requires 50mas IWA and reduced noise system)

42

Is This Lifefinder?

What is the definition of Lifefinder?

Scientifically: Be able to understand chemistry of atmosphere and surface?

Operationally: Spectroscopy at R~1000?

43

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)

44

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

45

Lab Studies

46

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

47

Alignmentacquisition & hold

48

L2 Orbit Favorable

49

Planning the Mission

50

Status of New Worlds

NIAC Complete

Concept Study Proposal

Decadal Review– Does General Astrophysics Too

51

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

52

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.