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Detailed Spectroscopy of Exoplanets with Export Control Notice The New Worlds Observer Export or re-export of information contained herein may be subject to restrictions and requirements of U.S. export laws and regulations and may require advance authorization from the U.S. Government. Webster Cash University of Colorado November 21, 2008 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 didn’t 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 2 25 Aug 2008 NWO Science Telescope 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: – – – – – – – – – 3 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 25 Aug 2008 NWO Science Telescope Stars are very bright and their glare makes it difficult to see fainter objects near them 4 25 Aug 2008 NWO Science Telescope New Worlds Observer 5 25 Aug 2008 NWO Science Telescope New Worlds Observer 6 25 Aug 2008 NWO Science Telescope Fly the Telescope into the Shadow 7 25 Aug 2008 NWO Science Telescope Dropping It In Note: No Outer Working Angle 8 25 Aug 2008 NWO Science Telescope Extinguishing The Spot of Arago 9 • I Stand on the Spot of Arago and Explain How to Remove the Spot of Arago • Occulters Have Very Poor Diffraction Performance • Must satisfy Fresnel Equation, Not Just the Fraunhoffer Equation • Must Create a Zone That Is: • Must Be Practical – – – – – – – – – The 1818 Prediction of Fresnel led to the famous episode of: Spot of Arago (variously Poission’s Spot) Occulters Often Concentrate Light! Deep Wide Broad Binary Size Tolerance 25 Aug 2008 Below 10-10 diffraction A couple meters minimum Suppress across at least one octave of spectrum Non-transmitting to avoid scatter Below 150m Diameter Insensitive to microscopic errors NWO Science Telescope NWO has an Opaque Starshade • Apodizing Function Apodization Function Transmission Offset Hypergaussian function r a n T exp b • Opaque Starshade Radius Parameter 10 25 Aug 2008 Occulter inner radius a Petal 1/e length b Hypergaussian order n Distance to telescope z Number of petals P NWO Science Telescope Performance A 50m diameter occulter at 80,000km can reveal Earths at over 20pc 11 25 Aug 2008 NWO Science Telescope Shadow of 16 Petal Mask Log Linear 12 25 Aug 2008 NWO Science Telescope Target Stars: Exo-zodiacal Light 4m Case 1.5m 13 25 Aug 2008 4m 2.4m NWO Science Telescope From 10mP. Oakley Map Planetary Systems • • • Prime Goal is Exploration of the Solar Neighborhood Uranus NWO will allow us to make maps of over 100 nearby planetary systems from the habitable zone outward Galaxies Zodiacal Light Jupiter Saturn Detect and classify all major planets Neptune 14 25 Aug 2008 NWO Science Telescope 10 arcseconds Study Exoplanets • NWO will perform spectroscopy of discovered planets • This will reveal their true natures H2O O2 CH4 NH3 15 25 Aug 2008 NWO Science Telescope Four Color Photometry – Molecules!! 16 25 Aug 2008 NWO Science Telescope 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 17 25 Aug 2008 NWO Science Telescope 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 18 25 Aug 2008 NWO Science Telescope 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 • 19 Scheduling & ops by STScI or equiv. Hubble NWO Instantaneous sky ~50% ~80% Continuous sky ~20% ~35% 25 Aug 2008 NWO Science Telescope 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 Enhancing Technologies 20 25 Aug 2008 Solar Electric Propulsion •NEXT engine •Increase observable targets •Reduce propellant mass NWO Science Telescope Lightweight S/C Structures •Increase observable targets •Reduce overall mass 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 21 25 Aug 2008 NWO Science Telescope 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 22 25 Aug 2008 NWO Science Telescope Other Exozodi Issues • Confusion from dust structure Epsilon Eridani − “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 … Beta Pic Red − Solar System zodi has red scattered light color − Known debris disks show red, grey, & blue colors 23 25 Aug 2008 NWO Science Telescope HD 92945 Neutral AU Mic Blue Target Stars: Exposure Times i = 60˚ 24 From A. Roberge 25 Aug 2008 NWO Science Telescope Target Stars: Habitable Zones 50 mas IWA 25 25 Aug 2008 NWO Science Telescope From M. C. Turnbull Target Stars: Habitable Zones NWO Detection Space 26 25 Aug 2008 NWO Science Telescope From M. C. Turnbull Characterizing the Planet • “Habitability” = liquid water on surface • Spectrum mostly shows atmosphere • How to know it’s “habitable”? – Very strong H2O signature, like Earth – H2O + (surface temp or planet size or orbit) 27 25 Aug 2008 NWO Science Telescope Turnbull et al. (2006) Characterizing Planets: Spectroscopy NWO Karkoschka et al. 1998 28 25 Aug 2008 NWO Science Telescope Characterizing Planets: Photometric Variability From P. Oakley 29 25 Aug 2008 NWO Science Telescope The Starshade is Adaptable Starshade Telescope Primary Science 15 m 1m 25 m 1.5 m 50 m 4m TPF + Characterization 100 m 10 m Lifefinder N x 70 m Nx4m Exo-zodi mapper Outer Planet imager Planet Imager Increasing Resolution NWO Can also work with existing telescopes such as JWST The starshade offers a scalable technology 30 25 Aug 2008 NWO Science Telescope