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Advances in High-Contrast Imaging Techniques for Exoplanet Detection

The Michelson Summer School on High-Contrast Imaging, held at Caltech from July 20-23, 2004, explored cutting-edge techniques in detecting faint background objects near bright stars. Key topics included inner and outer working angles, various perturbations affecting imaging, and simulation methodologies employing advanced instruments like Keck IRCAL and Lick AO. Participants delved into methods to achieve high contrast, specifically targeting detection limits of contrast ratios down to 10^-10, and explored innovative pupil mapping techniques for enhanced image clarity.

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Advances in High-Contrast Imaging Techniques for Exoplanet Detection

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  1. Key Types Introduction Wesley A. Traub Harvard-Smithsonian Center for Astrophysics Michelson Summer School on High-Contrast Imaging Caltech, Pasadena 20-23 July 2004

  2. Reminders of main topics • C, IWA, OWA • types • perturbations

  3. C K~20 mag Bkgd objects 7 arcsec wand J~21 mag Bkgd object 20 arcsec radius circle Ref: McCarthy & Zuckerman (2004); Macintosh et al (2003)

  4. Search space: best to date Keck IRCAL, Lick AO, K Ks, AO, NACO, VLTI WFPC2, HST, I CFHT, AO, H Keck NICMOS, 10sig 50% det, HST, H XAO, 10m, R, 2007 Airy Halo

  5. Earth & Jupiter-Saturn, 100 stars Simulations by Bob Brown, STScI

  6. Earth & Jupiter-Saturn Regions

  7. Radial-velocity Stars

  8. RV stars and brown dwarfs

  9. 1.8-m range

  10. TPF-C Range

  11. C, IWA, OWA Contrast C: Example: C = 10-10 driven by Earth/Sun = 2x10-10. Inner working angle IWA: Example: IWA = 3 /D driven by 1 AU/10pc = 0.100 arcsec. Outer working angle OWA: Example: OWA = 48 /D driven by N = 96 actuator DM.

  12. Image-plane coronagraph simulation 1st image with Airy rings mask, centered on star image 1st pupil 2nd pupil Lyot stop, blocks bright edges 2nd image, no star, bright planet Ref.: Pascal Borde 2004

  13. Wide-band (quadrant-phase) mask

  14. y v Shaped-pupil mask x u Image: cut along the x-axis Pupil: Spergel-Kasdin prolate-spheroidal mask Image: dark areas < 10-10 transmission A(x, 0) = exp(-(x/)2) A(0, y) = periodic & messy Kasdin, Vanderbei, Littman, & Spergel, preprint, 2004

  15. Discrete-mapped pupil (2): Densification Clean image, narrow FOV Image with many aliases Densified pupil Entrance pupil, sparsely filled FOV is small.

  16. Continuous-mapped pupil Input wavefront: uniform amplitude. Mirror 2 100 dB = 10-10 = 25 mag Output wavefront: prolate-spheroidal amplitude. Output image: prolate spheroid Mirror 1 Compact star image, easily blocked

  17. Nulling-shearing coronagraph

  18. Phase ripple and speckles Polishing errors on primary Pupil plane Phase ripples from primary mirror errors Speckles generated by 3 sinusoidal components of the polishing errors No DM: Image plane With DM: Image plane

  19. Phase + amplitude ripple and speckles h(u) = n (an+ian')cos(Knu) + (bn+ibn')sin(Knu) = total ripples Describes all possible phase and amplitude ripples (= errors). DM can give I() = (0) + n [(bn’)2 + (an’)2 ] (k+Kn)  bigger speckles + [ 0 + 0 ] (k-Kn)]  smaller (zero) speckles

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