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Slide 1: High-contrast AO for imaging extrasolar planets (formerly known as Extreme AO) Bruce Macintosh (LLNL)
Slide 2: Outline • Science motivation for Extreme AO: Imaging extrasolar planets • Fourier optics with perfect wavefronts – coronagraphs • Fourier optics with phase errors – High-contrast AO PSFs • ExAO system design: the Gemini Planet Imager
Slide 4: Formation history is encoded in distributions Core acceretion + migration predictions (Ida&Lin 2004)
Slide 5: Orbital scattering in 3 body systems; Chatterjee et al. astroph/0703166 5 AU 50 AU
Slide 6: Disk fragmentation efficient at 10-20 AU Qmin=1.7 Mayer et al. 2002 160 yr 350 yr Qmin=1.4 20 AU
Slide 7: Doppler
Slide 8: Direct detection & spectroscopy of brown dwarfs Mclean et al 2003
Slide 9: GDPS Lafrienere et al 2007 (Gemini Planet Survey) etc.
Slide 10: Uncertainty in luminosity of young planets Previous models Current AO surveys Low-entropy core accretion models Extreme AO regime Marley et al 2006 astro-ph/0609739
Slide 11: Voyager “family portrait”
Slide 12: Conventional AO limited by scattered light Strehl ratio S Halo intensity 1-S
Slide 13: “Extreme” AO (ExAO) gain > S/(1-S)
Slide 14: High-contrast AO PSF • • Fraunhoffer regime: focal plane and pupil plane are connected by Fourier transforms (x,y) = pupil plane coordinates – Natural coordinate system is in units of telescope diameter • x=x[m]/D (η, ξ) = focal plane coordinates – Natural coordinate system is in units of λ/D – η= θX/(λ/D) E FT • • • • Spatial frequency 1/a <=> angular scale λ/a Upper case / lower case = fourier transform pairs – Upper case for pupil plane e e(η, ξ) = FT[E (x,y)] P,p = PSF (intensity)
Slide 15: Pupil electric field from aperture and phase Pupil plane E ( x, y ) = A( x, y )eiΦ ( x , y ) Focal plane e(ξ ,η ) = FT ( A( x, y )eiΦ ( x , y ) ) p (ξ ,η ) = e(ξ ,η ) 2 E(x,y) e (ξ,η) A = aperture Φ = phase a,φ = fourier transforms of above
Slide 16: Simple case: uniform phase Pupil plane E ( x, y ) = A( x, y ) Focal plane e(ξ ,η ) = FT ( A( x, y )) = a (ξ ,η ) p (ξ ,η ) = a (ξ ,η ) 2 E(x,y) e (ξ,η) |a|2 A = aperture Φ = phase a,φ = fourier transforms of above A
Slide 17: For small phase errors: Taylor expansion (Sivaramakrishnan et al 2002, Perrin et al 2003) Pupil plane Focal plane Ε ( ξ, ψ) = Α( ξ, ψ)ε ιΦ ( ξ, ψ) 2 e(ξ ,η ) = FT ( A( x, y )eiΦ ( x , y ) ) p (ξ ,η ) = e(ξ ,η ) 2 Φ = Α(1 + ιΦ − + K) 2
Slide 18: PSF expansion AΦ 2 e (ξ ,η ) = FT ( A ( x , y ) e iΦ ( x , y ) ) = FT ( A + AiΦ − + ...) 2 a *φ *φ = a + i(a * φ ) − + ... 2 p (ξ ,η ) = e (ξ ,η ) = e (ξ ,η ) e* (ξ ,η ) 2 a *φ *φ a* *φ * *φ * = (a + i(a *φ ) − + ...)( a * − i ( a * * φ * ) − + ... 2 2 = aa * + i[ a ( a * ∗ φ * ) − a * ( a ∗ φ )] + ( a ∗ φ )( a * ∗ φ * ) − 1  a (a* ∗ φ * ∗ φ * ) + a* (a ∗ φ ∗ φ )  2  + ...
Slide 19: PSF terms p = p0 + p1 + p2 + ... p0 = aa * • Diffraction pattern term Airy pattern p1 = −i[a (a* ∗ φ * ) − a(a ∗ φ )] = 2 Im[a(a* ∗ φ * )] p2 = (a ∗ φ )(a* ∗ φ * ) − 1  a ( a* ∗ φ * ∗ φ * ) + a* ( a ∗ φ ∗ φ )  2 
Slide 20: aa*=|FT(A)|2 is the diffraction term
Slide 21: Two-d Airy patterns
Slide 22: Coronagraphs • Invented by Bernard Lyot in 1930 for studying the corona of the sun without waiting for an eclipse
Slide 23: How can we control diffraction? A PSF PSF=aa*=|FT(A)|2
Slide 24: Coronagraph 1: Gaussian apodization
Slide 25: Coronagraph 101: Blackman or Kaiser apodization A=0.42-0.05 cos[2π(r+0.5)] +0.08 cos[4π(r+0.5)] • • More complex functions can have higher contrast or better throughput Apodizers in general are hard (impossible) to manufacture
Slide 26: Apodization in 2d
Slide 27: Pupil Shaped-pupil coronagraphs (Kasdin et al. 2003) PSF
Slide 28: Lyot coronagraph (Lyot, 1933) Starlight
Slide 29: Lyot coronagraph (Lyot, 1933) Planet Sivaramakrishnan et al 2001 has a nice 1-d analysis of how this works
Slide 30: Many new coronagraphs in recent years • Explosion of coronagraph concepts in recent years • Lyot family: – Basic: Lyot 1939 MNRAS 99, 538; Sivaramakrishnan et al 2001 – Band-limited: Kuchner & Traub 2003 – Apodized: Soummer 2005 Ap.J. 618, L161 • Apodizers: – Shaped-pupil: Kasdin et al 2003, Kasdin et al 2005 Applied Optics 44 1177, etc. – Phase-induced apodizer: Guyon et al 2005 Ap.J. 622, 744 • Interference / wave-optics – 4-quadrant phase mask: Rouan et al 2000 PASP 777 1479 – Nulling interferometer/coronagraphs: Mennesson et al. 2004 Proc. SPIE 4860, 32 • Optical vortices, many others… • Most practical coronagraphs only work at > 3-5 λ/D • Control of phase errors has been neglected
Slide 31: PSF terms p = p0 + p1 + p2 + ... p0 = aa* p1 = −i[a(a ∗ φ ) − a (a ∗ φ )] * * • • Diffraction pattern term Pinned speckle term – Antisymmetric – Traces the diffraction pattern; vanishes when diffraction is negligible – See Bloemhof 2003, Perrin et al 2003 = 2 Im[a(a* ∗ φ * )] p2 = (a ∗ φ )(a* ∗ φ * ) − 1  a (a* ∗ φ * ∗ φ * ) + a* ( a ∗ φ ∗ φ )  2  • Strehl term – Removes power from PSF core • Halo term – ~=|φ|2 (power spectrum of Φ) – Symmetric – Dominant source of scattered light in high-contrast AO!
Slide 32: d λ/d
Slide 34: White noise White noise
Slide 35: AO architecture and terms Atmosphere parameters: Coherence length r0 Wind velocity v DM conjugate to telescope primary Deformable Mirror Collimating Lens Tip/Tilt Mirror WFS conjugate to DM & primary d Dichroic d=actuator spacing D = primary mirror diameter Wavefront Sensor Science Camera
Slide 36: Power spectrum Spatial frequency Spatial frequency Phase Spatial frequency
Slide 37: Power spectrum Spatial frequency Spatial frequency Phase Spatial frequency
Slide 38: Power spectrum Spatial frequency Spatial frequency Phase Spatial frequency
Slide 39: Power spectrum Spatial frequency Spatial frequency Phase Spatial frequency
Slide 40: Power spectrum Spatial frequency Spatial frequency Phase Spatial frequency
Slide 41: Power spectrum Spatial frequency Spatial frequency Phase Spatial frequency
Slide 42: AO architecture and terms Atmosphere parameters: Coherence length r0 Wind velocity v DM conjugate to telescope primary Deformable Mirror Collimating Lens Tip/Tilt Mirror WFS conjugate to DM & primary d Dichroic d=actuator spacing D = primary mirror diameter Wavefront Sensor Science Camera
Slide 43: Phase Power spectra
Slide 44: Phase Power spectra
Slide 45: Band-limiting for anti-aliasing: spatial filter PSF intensity λ/dap Position (arcsec)
Slide 46: Spatial filter (Poyneer and Macintosh 2004) implementation Deformable Mirror Dichroic Focal stop spatial filter λ/d=0.9” Wavefront Sensor Science Camera+Coronagraph
Slide 47: Phase Power spectra
Slide 48: Inner working distance ~3-5 λ/D Outer working distance ~N λ/D AO Ti m ag el Fittin g erro r WFS measurement
Slide 49: Random intensity of all the Fourier components produces speckles
Slide 50: (ExAO PSF movie goes here)
Slide 51: As speckles average out (τ ~D/vwind) planets can be detected
Slide 52: AO architecture and terms Atmosphere parameters: Coherence length r0 Wind velocity v DM conjugate to telescope primary Deformable Mirror Collimating Lens Tip/Tilt Mirror WFS conjugate to DM & primary d Dichroic d=actuator spacing D = primary mirror diameter Wavefront Sensor Science Camera
Slide 53: ExAO 0 nm static errors, 5 MJ/500 MYr planet, 15 minute integration
Slide 54: ExAO 1 nm static errors, 5 MJ/500 MYr planet, 15 minute integration
Slide 55: ExAO 2 nm static errors, 5 MJ/500 MYr planet, 15 minute integration
Slide 56: ExAO 5 nm static errors, 5 MJ/500 MYr planet, 15 minute integration
Slide 57: ExAO and the Gemini Planet Imager 2003: Basic ExAO feasibility study and Keck strawman 2004: Gemini “Extreme AO Coronagraph” Conceptual design begins 2005: CfAO team selected 2006: (June): Project start First light: 2010 Team LLNL: Project lead + AO AMNH: Coronagraph masks&design HIA: Optomechanical + software JPL: Interferometer WFS UCB: Science modeling UCLA: IR spectrograph UdM: Data pipeline UCSC: Final integration&test
Slide 58: AO Linear ADC Gemini f/16 focus Entrance Window Stage Artificial sources Woofer DM & Tip/Tilt MEMS DM F/64 focusing ellipse WFS CCD Coronagraph Focal Plane Occultor Wheel Reference arm shutter Calibration Module LO pickoff Phasing Mirror LOWFS Pinhole Apodizer Wheel Dichroic WFS P&C & focus Lenslet Filter Wheel SF Beamsplitter Collimator Polarization modulator Zoom Optics Lyot wheel WFS collimator IR spectrograph HAWAII II RG Filter Wheel IR CAL WFS Dewar Window CAL-IFS P&C & focus Filter Wheel Prism Polarizing beamsplitter and anti-prism Lenslet Pupil viewing mirror Pupil Camera IR Self-calibration interferometer
Slide 59: High order high-speed AO (LLNL) Superpolished optics (2 nm RMS) Woofer DM Calibration/ Alignment Unit GPI Window Keck AO (1999) Deformable mirror Subaperture Control rate Wavefront sensor Strehl @ 1.65 µm Guide star mag 349 actuators (240 active) 56 cm 670 Hz ShackHartmann 400 – 1000 nm 0.4 R<13 mag. GPI (2010) 4096 actuators (1809 active) 18 cm 2000 Hz Spatiallyfiltered SH 700-900 nm >0.9 I<9 mag. (V<11 aux.) MEMS deformable mirror Commercial computer Fourier (predictive) control Spatially Filtered WFS 0.7-0.9 µm Focal stop spatial filter λ/d=0.9”
Slide 60: Apodized-pupil Lyot coronagraph (Soummer 2005) Hard-Edged Mask Apodizer Lyot Mask Soummer 2005
Slide 61: Integral field spectrograph (James Larkin, UCLA) Spectrograph Collimator Optics Prism Camera Optics Detector Lenslet Array R.I. Telephoto Camera Collimated light from Coronagraph Pupil Plane Focal Plane Filters Lenslet Window Rotating Cold Pupil Stop Low spectral resolution (R~50) High spatial resolution (0.014 arcsec) Wide field of view (3x3 arcsec) Minimal scattered light
Slide 62: UCLA Spectrograph format • • • Each spectrum is 16 pixels long, one of YJHK, ∆λ/λ=50 68,000 spectra on a 2048x2048 detector 4.5 pixel spacing 2.8 x 2.8 arcsecond field of view, 0.014 arcsecond pixels Single Spectrum
Slide 63: UCLA Broad-band ExAO snapshot
Slide 64: UCLA ExAO spectral data cube James Larkin, UCLA
Slide 65: Marois et al. 2006, Spie Fresnel optics effects (more complicated than simple Fraunhoffer model) cause speckles from aberrations near focus not to subtract as well O1 O2 O3 O4
Slide 66: GPI enclosure Gemini Cassegrain support structure GPI mechanical design Gort Electronics Optics structure
Slide 67: GPI optical structure
Slide 68: VLT Planetfinder: SPHERE
Slide 69: Monte Carlo models of science performance (Graham&Macintosh)
Slide 70: Monte Carlo models of science performance (Graham&Macintosh)
Slide 71: ExAO can detect a significant population of planets GPI detections Radial velocity detections
Slide 72: H=8-11 mag Extrasolar planets H=5-8 mag H=4-6 mag
Slide 73: Space AO: Terrestrial Planet Finder • Terrestrial Planet Finder Coronagraph (was 2020, now deferred) Original baseline: 8x3m mirror with advanced AO to correct internal errors Coronagraph works at 4 λ /D -> 0.08 arcseconds for 8-m telescope – Earth at 10 pc = 0.1 arcsec • • • Various interim 2-4 m class missions proposed with more advanced coronagraphs – 2-3 λ/D coronagraph allows smaller telescope • Some visible-light spectroscopy of Earthlike planets
Slide 74: H=8-11 mag Extrasolar planets H=5-8 mag H=4-6 mag TPF space coronagraph
Slide 75: H=8-11 mag Extrasolar planets H=5-8 mag H=4-6 mag Small TPF
Slide 76: A very large coronagraph
Slide 77: TPF Occultor (Webster Cash et al)
Slide 78: References • • • • • • • • • • Angel, R, “Ground based imaging of extrasolar planets using adaptive optics’, 1994 Nature 368, 203 (Original exoplanet paper) Burrows, A., et al., “A nongray theory of extrasolar planets and brown dwarfs”, 1997 Ap.J 491, 856 (Planet models) Sivaramakrishnan, A., et al., “Ground-based coronagraphy with High-Order Adaptive optics”, 2001 Ap.J. 552, 397 (Lyot coronagraphs) Kasdin, N.J., et al, 2003, “Extrasolar planet finding via optimized apodized pupil and shaped pupil coronagraphs”, Ap.J. 582, 1147 Kuchner, M, and Traub, W., “A Coronagraph with a Band-limited Mask for Finding Terrestrial Planets” 2002 Ap.J. 570, 200 (improved Lyot coronagraph) Sivaramakrishnan, A., et al, “Speckle decorrelation and dynamic range in speckle noise limited imaging”, 2002 Ap.J. 581, L59 (2nd-order PSF expansion) Perrin, M., et al. “The structure of the High Strehl Ratio Point-Spread Functions”, 2003, Ap.J. 596, 702 (high-order PSF expansion) Poyneer, L, and Macintosh, B., “Spatially-filtered wavefront sensor for high-order adaptive optics”, 2004, JOSA A 21, 810 (aliasing + WFS) Guyon, O., et al. “Theoretical Limits on Extrasolar Terrestrial Planet Detection with Coronagraphs”, 2006 Ap.J.S. 167, 81 Cash, W., et al, “The New Worlds Observer: using occulters to directly observe planets”, 2006 Proc. SPIE 2625