1. National Aeronautics and Space Administration An Exoplanet Coronagraph on a Stratospheric Science Platform Wesley A. Traub and Pin Chen Jet Propulsion Laboratory, California Institute of Technology Bridging the Gap to Space Boulder, CO 26-28 Oct. 2009

2. National Aeronautics and Space Administration Science Motivation We now know that several hundred exoplanets exist around nearby stars. (And we expect Kepler to find several thousand around distant stars.) For all of these, we will know their mass and period (---> semi-major axis). For the transiting ones, we know their radius (--> mean density). However for nearly all of them, we will have no information on their color or spectrum, which are our first clues to their atmospheric properties. Eventually, we need SIM Lite to find all the nearby planets, and Terrestrial Planet Finder to fully characterize their spectra. Spectra, at R ~ 70, will tell us about H2O, CO2, CH4, O3, O2, plants, atmosphere, continents, oceans, rotation rate, and weather. These clues will also give us signs of life.

3. National Aeronautics and Space Administration We will not have SIM or a coronagraph in the coming 5 years, perhaps longer. So today we should practice the technique of observing an exoplanet’s colors, using a balloon platform. We believe that a 1-2 m class telescope plus coronagraph on a balloon platform will have the sensitivity to do this. Targets are the well-known Jupiters that are bright and well-separated from their stars. Benefits will be the first colors of these exoplanets, higher TRLs, A tech demo for space, and scientist/engineer training.

4. National Aeronautics and Space Administration 4 Pointing Platforms 2/3 axis frame, tip-tilt mirror, magnetically levitated bearings. Planetscope concept Solar Bolometric Imager Bernasconi et al., Adv. Sp. Res. 2004 The Planetscope Precursor package will occupy the bottom 0.5x2x2 m 3 volume of the Solar Bolometric Imager gondola (Pietro Bernasconi, PI), and will incorporate a Mars-prototype anemometer from Ball Aerospace (Rich Dissly, mgr.) and Cornell Univ. (Don Banfield, PI).

5. National Aeronautics and Space Administration 5 Earth is 10 billion/million times fainter than Sun 10 -10 visible 10 -6 infrared

6. National Aeronautics and Space Administration 6 Known exoplanets with separation and brightness accessible to Planetscope. PlanetMsiniPeriodSep.Delta (M J )(days)(arcsec)mag Eps Eri b0.8624961.2722.1 55 Cnc d3.9255510.4322.6 HD 160691 c3.1024940.3622.6 HD 190360 b1.5028910.3422.6 HD 217107 c2.1031500.3323.0 HD 39091 b10.3521510.2822.4 47 UMa c0.7625940.2721.8 14 Her b4.7417530.2121.8 HD 33636 b9.2824470.1922.3 Ups And d3.7512900.1720.8 Gam Cep b1.599050.1720.7 47 UMa b2.5410890.1620.4 HD 10647 b0.9110030.1320.7 HD 89307 b2.7330900.1321.7 HD 117207 b2.0627270.1221.3 HD 128311 c3.219190.1220.6 HD 38529 c12.7021640.1222.7 HD 70642 b2.0022310.1121.4 HD 216437 b2.1013530.1021.4 HD 169830 c4.0421020.1021.7 HD 160691 b1.676300.1019.5 HD 147513 b1.005280.1019.5 HD 37124 d0.6622950.1021.2

7. National Aeronautics and Space Administration 7 Coronagraph Search Space Example exoplanets. Over 250 are known.

8. National Aeronautics and Space Administration 8 Blue (0.4-0.6  m), Green (0.6-0.8  m), Red (0.8-1.0  m) Color Gives a First Impression of a Planet Solar system planets have colors that label them by type. Planet spectra

9. National Aeronautics and Space Administration 9 Lab demo, with planets added Trauger & Traub, Nature, April 2007 D Jupiter Earth ½ Jupiter 500 D-shaped images of dark hole, Rotated to sample annulus on sky, Planets added, Common speckles removed, Planets pop out of noise. Shows that Earth could have been detected.

10. National Aeronautics and Space Administration 10Traub IWA-OWA = 2-30 λ/D for 550 nm & 2.5 m C =  (2  σ/Nλ) 2 for σ = λ/1000 & σ = λ/10000 & N = 60 C (1 sec) C (1 hr) “Dome Seeing” Contribution: C(1 sec) assumes night best (rms = 1 nm) but only 0.1 nm of this going to speckles in the range IWA-OWA, with 0.9 nm going to piston and tilt. C(1 hr) assumes above reduced by (1 sec / 1 hr) 1/2, i.e., this is the uncertainty in the average background speckle level. Contrast & known RV exoplanets vs angle Expected free-atmosphere speckle contrast Expected PSF from coronagraph Expected dome-seeing contrast uncertainty in 1 hour

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12. National Aeronautics and Space Administration Expected disk sensitivities nameRA (h) Dec (deg) V (mag)d (pc)Ld/Lstar as (1AU) Log C (1AU) as (5AU) Log C (5AU) eps Eri9.5-93.73.21.00E-040.31-5.911.56-7.60 tau Cet1.7-153.53.61.00E-050.28-6.991.39-8.68 61 Vir13.3-184.78.52.00E-050.12-6.210.59-7.90 12

13. National Aeronautics and Space Administration Exoplanet targets target radius (as) separation (as) log(C) planet signal (elec/min) yr (max sep) RA (hr) Dec (deg) V (mag) d (pc) #Z (pl=zo di) eps Eri b0.790.65 - 0.79-8.2513.21 2012.7- 13.43.5-103.73.251 55 Cnc d0.500.23 - 0.50-9.090.242013.78.9286.013.454 HD 190360 b0.170.12 - 0.17-8.301.822013.720.0305.715.98 47 UMa c0.260.24 - 0.26-8.561.762014.311.0405.114.020 13

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15. National Aeronautics and Space Administration Telescope 15

16. National Aeronautics and Space Administration Xinetics SiC 0.8-m Mirror 16

17. National Aeronautics and Space Administration Coronagraph optics 17

18. National Aeronautics and Space Administration Low-order Wavefront Sensor 18

19. National Aeronautics and Space Administration 19 Summary A balloon coronagraph could b e built using available technology. A few one-night flights would demonstrate feasibility. A long-duration, multi-night flight would permit new science.

20. National Aeronautics and Space Administration 20 Thank you !

21. National Aeronautics and Space Administration 21 Backup Charts

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