NGAO Companion Sensitivity Performance Budget (WBS 3.1.1.10)

1. NGAO Companion Sensitivity Performance Budget (WBS 3.1.1.10) Rich Dekany, Ralf Flicker, Mike Liu, Chris Neyman, Bruce Macintosh NGAO meeting #6, 4/25/2007

2. Contrast budget - summary • Contrast performance budget still incomplete • Combining 2 analysis tools • Need more science input to complete

3. Goal and Science requirements • Goal of Contrast WFE budget (WBS 3.1.1.10): • Development of a companion sensitivity performance budget, based on a strawman coronagraph approach meeting the science requirements. Develop a contrast-driven spatio-temporal wavefront error budget that includes not just AO performance but realistic values for static/internal effects, so that we can see what instrument design choices (e.g. optics quality) are important now • From the System Requirements Document (KAON 456): • ≥4 magnitudes at 0.055” at 1-2.5 m for Galactic Center • ≥ 10 mags at 0.5” (0.7-3.5 m) for 30% sky cov. & ≤ 20” object diam. • These are insufficient specifications for contrast performance budget evaluation: more detailed observing scenario required to calculate actual contrast for specific cases.

4. High-C science case recap • Principal NGAO high-contrast science cases: • Direct imaging and spectroscopy of • Planets around low-mass stars and brown dwarfs • Resolved debris disks and protostellar envelopes • NGAO high-contrast selling points: • LGS tomography is the primary AO mode of interest • Large sky coverage • Fainter stars = many more targets +relaxed contrast requirements • Multi-band studies: optical & near-IR ~25 MJup ~5 MJup? (images from M. Liu ppt NGAO m1)

5. Analysis tools • Contrast budget spread sheet (analytical model) • Provided by B. Macintosh (derivative of GPI tool) • Fast to evaluate • Parameterizes speckle noise effects • Observing scenario implicit • We do not have good analytical models for some terms • Dynamic/static telescope aberrations (Keck pupil diffraction not included) • LGS effects • Tomography error (approximate power law for now) • Does not produce PSFs • Numerical AO simulations • YAO Monte Carlo AO simulation package (F. Rigaut) • Computationally expensive (more than ~30 s real time unreasonable) • Obtain AO PSFs at multiple wavelengths with & w/o coronagraph simultaneously • Contrast for a given observation scenario must be evaluated separately

6. Contrast tool (1) - Wavefront budget

7. Contrast tool (2) - PSD modeling

8. Contrast tool (3) - Observing scenario • “Contrast” depends on: • Smoothness of host star halo • Host star magnitude • Companion magnitude and position (angular distance from host) • Exposure time (speckle noise, dark current) • Complete observing scenario required in order to calculate contrast

9. Contrast tool (4) - Contrast budget • Sample contrast budget • 142 nm RMS WFE •  = 0.3” • m(J) = 16 • r0 = 0.18 cm • N = 48x48 sub-ap.

10. Using the contrast tool • [R,I,J,H,K,L] band (color/psym) • 142 nm (“Exo-Jupiter”) NGAO WFE budget (solid lines) • 158 nm (30° zenith angle) (dot-dashed lines)

11. Numerical simulation tool • 5-LGS (@ 90 km) quincunx asterism • Optimized for on-axis Strehl • 36x36 sub-apertures across pupil • 2-DM MCAO system • DM2 @ 10 km • Bright NGS case • Used 4 tip/tilt NGS for null-modecorrection; could have used only1 NGS (2x2) measuring Z2-Z6 • Frame rate 1 kHz • LOWFS @ 250 Hz • CN-M3 turbulence model • r0 = 18 cm

12. Lyot coronagraph model Slide borrowed from the Lyot Project

13. Apodized Lyot coronagaph • Implemented in YAO numerical AO simulation • 160 nm (36x36 quincunx MCAO shown below) 0.14% light though 10 /D occ. spot 1.5% light through 6 /D occ. spot No occulting spot

14. Radial average PSFs • No static/dynamic telescope aberrations • 160 nm RMS residual wavefront error • No coronagraph (left) ; 6/D occulting spot (right)

15. Radial average PSFs • No static/dynamic telescope aberrations • 160 nm RMS residual wavefront error • No coronagraph (left) ; 10/D occulting spot (right)

16. Radial average PSFs • 180 nm input (segment figure + windshake) • 170 nm RMS residual wavefront error • No coronagraph (left) ; 10/D occulting spot (right)

17. Conclusions / recommendations • Spread sheet contrast tool: • Needs to be validated/anchored against numerical simulation • Numerical simulations: • Will returns contrast estimates given observing scenarios • Host magnitude • Companion position & magnitude • Exposure time • Would like to include optical quality requirements (maybe not feasible within current study) • Observing scenarios: • Need to be better defined