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Hubble Space Telescope Coronagraphs

Hubble Space Telescope Coronagraphs. John Krist JPL. HST Cameras with Coronagraphs. NICMOS Camera 2 20” x 20”, 76 mas pixels l = 0.9 – 2.2 m m, multiple filters STIS (will be repaired in next mission) 52” x 52”, 50 mas pixels l = 0.2 - 1.0 m m (no filter)

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Hubble Space Telescope Coronagraphs

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  1. Hubble Space Telescope Coronagraphs John Krist JPL

  2. HST Cameras with Coronagraphs • NICMOS Camera 2 • 20” x 20”, 76 mas pixels • l = 0.9 – 2.2 mm, multiple filters • STIS (will be repaired in next mission) • 52” x 52”, 50 mas pixels • l = 0.2 - 1.0 mm (no filter) • ACS High Resolution Camera (HRC) • 26” x 29”, 25 mas pixels • l = 0.2 - 1.0 mm, multiple filters

  3. 0.6” NICMOS Coronagraph • 76 mas pixels, 20” x 20” field • Multiple filters over l = 0.9 - 2.2 mm • Occulting spot is r = 0.3” (1.7 - 3.5 l/D)hole drilled in mirror at intermediate focal plane • Spot and Lyot stop always in-place

  4. With a Misaligned Lyot Stop NICMOS Coronagraph PupilModels With an Aligned Lyot Stop Pupil after spot

  5. Effects of NICMOS Lyot Stop Misalignment F110W (~J band) Aligned Lyot Stop Model Misaligned Lyot Stop Model Observed Misalignment results in 2x more light in the wings + spikes

  6. NICMOS Image of HD 141569F110W (~J band)Science results in Weinberger et al. (1999) HD 141569 Image1 – PSF1 Image1 – PSF2 Reference Star Image2 – PSF1 Image2 – PSF2

  7. STIS Coronagraph • Primarily a spectrograph • CCD, 50 mas pixels, 52” x 52” field • Unfiltered imaging over l = 0.2 - 1.0 mm • Occulters are crossed wedges: d = 0.5”-2.8” (r = 5l/D – 30l/D @ V) • Lyot stop always in the beam

  8. STIS Occulters

  9. STIS CoronagraphComputed Intensity at Lyot Stop After Occulter, Before Lyot Stop After Lyot Stop

  10. HD 141569 STIS Image of HD 141569 HD 141569 - Reference Star 7” Reference Star Science results in Mouillet et al. (2001)

  11. ACS/HRC Coronagraph • CCD, 25 mas pixels, PSF FWHM=50 mas @ 0.5 mm • Multiple filters over l = 0.2 - 1.0 mm • Selectable mode in the HRC: the occulting spots and Lyot stop flip in on command • Two occulting spots: r = 0.9” and 1.8” (38l/D – 64l/D @ V) • Occulting spots in the aberrated beam from HST, before corrective optics

  12. r =1.8” (96%) r = 0.9” (86%) ACS Coronagraph1st (Aberrated) Image PlaneModel

  13. ACS Coronagraph Pupil Models Pupil After Lyot Stop Pupil After Spot

  14. V band (F606W) 7” Science results in Clampin et al. (2003) ACS Coronagraph Image of HD 141569

  15. PSF Subtraction Reference PSFSubtraction Roll Subtraction Beta Pictoris Roll 1 Roll 2 Alpha Pic 1 - 2 Beta - Alpha Pic ACS coronagraph ACS Science Team (Golimowski et al. 2006)

  16. Separated by 10 degrees in orientation, 5 hours in time ACS Coronagraph Images of Beta Pic 20”

  17. Spectral DeconvolutionSparks & Ford (2002)Images courtesy of Bill Sparks After Spectral Deconvolution & Unsharp Masking HD 130948 (ACS Coronagraph)

  18. Star outside of spot 7x reduction Coronagraph 6x reduction 1500x reduction 1200x reduction │Coronagraph - PSF│ (Roll subtraction) ACS PSF Mean Brightness Profiles (V)

  19. ACS Coronagraph Point Source Detection Limits

  20. HST vs. Ground: HD 141569 ACS Direct (V) STIS Coronagraph (U→I) Palomar AO Coronagraph (2.2 mm) Boccaletti et al. 2003 (Their image) ACS Coronagraph (V) NICMOS Coronagraph (J)

  21. HST vs. Ground Coronagraphs • HST limited to inner radius of r>0.6” (near-IR) and r>0.7” (visible, if STIS repaired, else 1.1” with ACS); on ground, 4l/D at 2 mm with a 10 m scope is 0.17” • HST stability allows PSF subtraction providing up to an additional 200x improvement in contrast (coronagraph improves contrast up to 7x); ground scope stability limited in most cases to <10x (PSF subtraction or SDI) and limited AO correction radius • HST is much better than ground for most disk imaging at radii > 1”; large scopes on ground better for point sources closer in

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