Detailed Spectroscopy of Exoplanets with The New Worlds Observer

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Detailed Spectroscopy of Exoplanets withThe New
Worlds Observer

• Webster Cash
• University of Colorado
• November 21, 2008

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Where Next with Space Missions for Exoplanets?

• There Has Been Stunning Progress in Study of
  Exoplanets
• It takes 10 to 20 years to launch a space
  observatory
• 14 years ago this field didnt exist
• where will it be in 20 years with or without
  space????
• A Space Exoplanet Mission Must Have A
• Dramatic Leap In Sensitivity and Inner Working
  Angle
• High Quality Spectroscopy
• Capability WAAAAAY Beyond What We have Seen So
  Far
• Otherwise the Mission Will Rendered Mundane
• In Short We Need High Quality Spectroscopy of
  Earth-twins
• And broad capability to study planetary systems
  in detail
• Anything less would be a gamble

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NWO Team Membership Organizations, Roles and
Leads

• Team consist of 43 active members
• 9 organizations are participating
• Additional involvement is provided from each
  organization and includes technical area experts
  and graduate/undergraduate students
• Organizations, Roles and Leads
• Colorado University PI, Science, Optical Design,
  and Systems Analysis Webster Cash
• Northrop Grumman Deputy PI and Starshade
  Development Amy Lo
• Ball Aerospace Technology Corporation Telescope
  Development Charley Noecker
• USNO Astrometry Ralph Gaume
• NASA GRC Occulter (Starshade) Propulsion Scott
  Benson
• KinetX Mission Design and Navigation Bobby
  Williams
• GSI Lead Scientist Maggie Turnbull
• University College of London Exoplanet Spectra
  Modeling Giovanna Tinetti
• NASA GSFC Study Management Kate Hartman

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Stars are very bright and their glare makes it
difficult to see fainter objects near them
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New Worlds Observer
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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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Extinguishing The Spot of Arago

• I Stand on the Spot of Arago and Explain How to
  Remove the Spot of Arago
• Occulters Have Very Poor Diffraction Performance
• The 1818 Prediction of Fresnel led to the famous
  episode of
• Spot of Arago (variously Poissions 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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NWO has an Opaque Starshade

• Apodizing Function

Apodization Function
Offset Hypergaussian function

• Opaque Starshade

Parameter
Occulter inner radius a
Petal 1/e length b
Hypergaussian order n
Distance to telescope z
Number of petals P
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Performance

• A 50m diameter occulter at 80,000km can reveal
  Earths at over 20pc

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Shadow of 16 Petal Mask
Log
Linear
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Target Stars Exo-zodiacal Light
4m Case
From P. Oakley
10m
4m
2.4m
1.5m
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Map Planetary Systems

• Prime Goal is Exploration of the Solar
  Neighborhood
• NWO will allow us to make maps of over 100 nearby
  planetary systems from the habitable zone outward
• Detect and classify all major planets

Uranus
Galaxies
Zodiacal Light
Jupiter
Saturn
Neptune
10 arcseconds
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Study Exoplanets

• NWO will perform spectroscopy of discovered
  planets
• This will reveal their true natures

CH4
NH3
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Four Color Photometry Molecules!!
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Find Earth-like Planets

• NWO can look close enough to the central star to
  see Earth twins
• NWO can find more Earths than any other approach
• NWO can separate barren rocks from water worlds

Need best completeness diagram here
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Search for Life

• NWO can do detailed spectroscopy of Earth-like
  planets
• Resolution in the 100 to 1000 range
• Can easily detect water in the atmosphere
• Can see surface features as the planet rotates
• Can detect the key biomarkers

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NWO Allows Ample time for General Astrophysics

• While starshade retargets, telescope is free for
  general astrophysics
• At least 50 of telescope time is devoted to
  general astrophysics
• Telescope can see within 50 degrees of sun
• Capable of weeks of continuous integration
• Telescope operation similar to JWST
• Scheduling ops by STScI or equiv.

Hubble NWO
Instantaneous sky 50 80
Continuous sky 20 35
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Starshade Critical Technology
Enabling Technologies

• Precision Shape Control
• Maintain edge position
• Maintain structure shape

• Thin Edge Treatment
• Maintain edge stability
• Minimize stray light

• Precision Deployment
• Minimize jitter
• Maintain petal location

• Opaque Membrane
• Maintain opacity
• Lightweight

• 2 Axes Formation Flying
• Maintain 1m alignment
• Minimize jitter

• Solar Electric Propulsion
• NEXT engine
• Increase observable targets
• Reduce propellant mass

• Lightweight S/C Structures
• Increase observable targets
• Reduce overall mass

Enhancing Technologies
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Science Goals

• Completely Map the Nearby Stellar Systems
• Catalogue All Major Planets and Belts
• Classify Each (Develop Classification Schemes!)
• Measure Approximate Orbit of Each
• Spectroscopically Study the Most Interesting
  Planets
• Find Water Planets
• Search for Life
• Watch Planetary Systems Forming
• General Astrophysics with a True Hubble Follow-on

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Detect and Study ExoZodis

• Orbiting dust scatters starlight an cause
  exozodiacal light
• The exozodi can be strong enough to obscure the
  planets
• We currently know NOTHING of the nature of
  exozodis

Knowledge of Exozodi is key to the direct
detection of exoplanets NWO can measure hundreds
of such systems NWO can detect planets despite
high levels of exozodi
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Other Exozodi Issues
Epsilon Eridani

• Confusion from dust structure
• Is that a planet or a dust clump?
• Can we tell by its color before wasting time on a
  spectrum?

Greaves et al. (2005)

• Maybe
• Solar System zodi has red scattered light color
• Known debris disks show red, grey, blue colors

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Target Stars Exposure Times
i 60
From A. Roberge
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Target Stars Habitable Zones
50 mas IWA
From M. C. Turnbull
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Target Stars Habitable Zones
NWO Detection Space
From M. C. Turnbull
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Characterizing the Planet

• Very strong H2O signature, like Earth
• H2O (surface temp or planet size or orbit)

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Characterizing Planets Spectroscopy
NWO
Karkoschka et al. 1998
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Characterizing Planets Photometric Variability
From P. Oakley
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The Starshade is Adaptable
Starshade Telescope Primary Science
15 m 1 m Exo-zodi mapper
25 m 1.5 m Outer Planet imager
50 m 4 m TPF Characterization
100 m 10 m Lifefinder
N x 70 m N x 4 m Planet Imager
Increasing Resolution
NWO Can also work with existing telescopes such
as JWST
The starshade offers a scalable technology