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Recent & planned high-contrast work on the WCS and P3K

Recent & planned high-contrast work on the WCS and P3K. Gene Serabyn Nov. 12, 2007. H . 80. 100. 200. 250. Strehl vs. wavelength. Go short or go deep WCS provides P3K ExAO performance now. ExAO On WCS. ExAO,WCS. AO. Well Corrected Subaperture (WCS) Relay Optics. Magnify pupil

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Recent & planned high-contrast work on the WCS and P3K

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  1. Recent & planned high-contrast work on the WCS and P3K Gene Serabyn Nov. 12, 2007

  2. H 80 100 200 250 Strehl vs. wavelength • Go short or go deep • WCS provides P3K ExAO performance now ExAO On WCS ExAO,WCS AO

  3. Well Corrected Subaperture (WCS) Relay Optics • Magnify pupil • Keep pupil location at DM • Center sub-pupil on DM • Maintain F# to AO system ROB AO

  4. Potential ExAO Directions • Programs: • Short wavelength/visible AO • Faint companion observations: • Coronagraphy • Transit observations • Nulling Interferometry • Make use of: • High Strehl • Stable PSF • Stable pointing (remove NCP drifts after AO) • Speckle reduction

  5. ExAO Goals and Needs *Needs 2 good sub-apertures

  6. (Bright) Companion Signal Levels: Brown Dwarfs & Hot Jupiters • Thermal flux ratio = BplApl/(B*A*) • (in RJ limit = TplApl/T*A*) • Area ratio  0.01 • (primary transits) • Temp ratio  0.2 • Flux ratio as much as a few 0.1% • (secondary transits, imaging) • Transit observations: • Need photometric stability of order 0.1% • Coronagraphic observations • Need small inner working angle (IWA), low wavefront rms • Need high contrast near IWA

  7. Exoplanet Transit Spectroscopy: Strehl Stability • Best Strehl ratio  0.92-0.94 • rms 85 -100 nm • Strehl stability: 1 % rms

  8. Stabilize ExAO PSF on slit Difference spectra before and during transits Non-common path pointing drift removal essential new SSMs A handful of targets are bright enough with WCS H/K grism will help sensitivity 5 m collecting area will help increase target list Exoplanet Transit Spectroscopy

  9. High-Strehl Coronagraphy • Need a good wavefront and a good coronagraph • Goal is small inner working angle • Can partially make up for smaller aperture FQPM coronagraphy Pupil plane phase coronagraphy (e.g. coma) Band-limited masks: linear mask good for binaries

  10. High-contrast Coronagraphy: The Binary Star HD148112 through a FQPM • Focal plane phase masks (FQPM, vortex) allow small IWA Normal “off-FQPM” image “Through–FQPM” image Peak extinction = 80 Mean of 5 short exposures (total time = 21.24s) Cross-diagonal subtraction Peak extinction = 235  6 mag

  11. Brown Dwarf pair HD130948 at Ks • Broadband: Ks • Stellar rejection  35:1 • Ks = 6.9 ± 0.5 • separation = 2.61 ± 0.08“ • At  7.5 /DLyot Could see it to 1.5 /DLyot • Looked at fainter, closer BDs 9/06 • now 50:1 Ks • Limitations: • Mask performance • SSM mirror actuator accuracy • Need to stay on the crosshairs • Long-lived speckles 1.5 /D 500:1

  12. Off-axis Performance “Off-FQPM” PSF “On-FQPM” PSF Quadrant-subtracted PSF The quadrant subtraction improves the rejection of the peak, but also the halo. • Below 10-3 at 2/D • Waiting to develop and install new masks • Need to remove long-lived speckles

  13. Pupil Phase Coronagraphy (Coma) • Iscat = (1-S)/N2  4 10-4 • Example: 1.4 waves PV of coma at 2.16 m • Example of pupil phase coronagraphy (Codona et al.) • Generate dark hole on half of image Ideal 1st ring • Iscat

  14. Pupil phase (coma) coronagraphy • Initial trial carried out on the WCS in 9/06 • Dark area at the 2 x 10-3 level at 2/D • Saw very long-lived speckles • Require non-common path error reduction/ long-lived speckle reduction • Can move on to more complex phase distributions

  15. Comparison of Coronagraphs Guyon et al. 2006

  16. Visible AO in the B-band (400-450 nm): • SAO 70505 • V = 4.5, 6.0 • sep = 0.90 arcsec • SAO 37735 • V = 5.1, 6.3 • sep = 0.34 arcsec 1 pix. = 25.3 mas /D (B) = 59 mas Strehl  0.10 – 0.12 • Blue companions to red giants/supergiants • Sirius, O Ceti, etc… • White dwarf/supergiant flux ratio  10-4 in the red • Much better blue ratio because WDs are very hot • Can move to fainter stars with P3K • Red/Vis AO

  17. Sensitivity Limitations to WCS • Science camera sensitivity • Lose factor of ten for area • Lose small factor for transmission (t  0.8) through WCS relay • Gain small factor for Strehl improvement (1.5) • WCS roughly an order of magnitude less sensitive than 5 m aperture • WFS sensitivity • Also lose first two factors for WFS • WFS cutoff roughly 3 magnitudes higher • Flexcam sensitivity • Removes non-common path pointing drift • Not the best camera • Same issues as science camera • Limit for the latter two systems is currently ~ 10th mag • Limit not fundamental for flexcam

  18. P3K Implications/Improvements • WCS imaging performance for entire 5 m • Coronagraphs • Transits • Science camera and “flexcam” sensitivities to improve by ~ 3 mag • Fainter sources • Disks as well as companion searches • Can also get better flexcam • WFS sensitivity loss remains • WFS another 2.5 mag worse with P3K+WCS • Interesting for very high Strehl coronagraphy and high-Strehl vis AO (red and blue)

  19. Science Goals • High Strehl stability for transits (HJs) • High contrast at small IWA for companion searches (BDs, etc.) • High Strehl for short wavelength AO (WDs)

  20. Prelminary Experiments with the WCS • Extreme AO • PSF properties/stability in high-Strehl regime • Non-common path error reduction (tip-tilt; higher order) • Dark hole generation • Atmospheric Characterisation • Spatial filtered WFS • Visible AO • Initial observations of close binaries • Atmospheric properties (isoplanatic angle…) • Laser guide star visible AO? • High-contrast IR coronagraphy (S > 90%) • FQPM, Pupil-Phase, Band-limited, • Vortex, apodized pupil, etc… • Dark-hole, PSF subtraction, dual- imaging, dual-polarization imaging… • Palomar provides an excellent venue for new techniques • Preliminary experiments can accelerate P3K (new SSMs, SF WFS, speckle reduction…) and help keep the lead

  21. 0 Nulling Interferometry on the 200-inch with a rotating baseline • Phase the two subapertures to center a dark interference fringe on a bright star • Rotate pupil image or applied phase map to modulate off-axis signals Signals from off-axis sources: Green = /2b Blue = 3/2b • Dual subaperture approach

  22. Expected Performance without Phase Control • Model 100 rotations: top envelope gives avg. null of 0.1 with current AO • Measure bottom envelope shape rapidly • ExAO will lower top envelope to 0.01 and make a huge difference • Phase control between subapertures will also provide improvement

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