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NGAO Photometric Accuracy Budget Strategy

NGAO Photometric Accuracy Budget Strategy. Richard Dekany. Outline. Photometry Science ELT Simulations Photometric Variance Sources Performance Budget Strategy Analytic Expressions Numerical Investigations Simulations Data Analysis Outstanding Issues Discussion. Noise Processes

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NGAO Photometric Accuracy Budget Strategy

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  1. NGAO Photometric Accuracy Budget Strategy Richard Dekany

  2. Outline • Photometry Science • ELT Simulations • Photometric Variance Sources • Performance Budget Strategy • Analytic Expressions • Numerical Investigations • Simulations • Data Analysis • Outstanding Issues • Discussion

  3. Noise Processes Photon Noise Source photon noise Imperfect background subtraction Detector Issues Noise Read Noise Fixed-Pattern Noise Dark Current Popcorn Noise (rapid level shifts) Residual flat-fielding errors (linear, but wrong constant) Detector non-linear response Few/Single pixel errors Cosmic rays / hot pixels / dead pixels Quantum efficiency variations PSFUncertainties On-axis Time-Variability of AO Performance Telescope Vibrations Saturation Off-axis Residual angular anisoplanatism Passive PSF estimation DIMM 0 errors Wind-induced anisoplanatism Telemetry noise Active PSF shaping MCAO residuals Optics Residual field dependentaberrations (esp. field curvature) Variable transmission (coating degradation) Field dependenttransmission (beamwalk) Photometric Error Sources Source Uncertainties • Stellar • Star variability • Time-variable chromatic emmissions (variable color) • Maculation (sunspots) • Extrastellar • Crowding • Differential interstellar extinction Environmental • Atmospheric scintillation • Variable extinction • Scatter • Transparency waves • Airmass variation across FoV • Heterochromatic extinction Calibration • Filter • Bandpass uncertainties

  4. Proposed Performance Budget Strategy

  5. NGAO Error Budget KBO imaging scenario Based on Lick, Palomar & Keck experience RD

  6. NGAO Photometry Budget M31 Bulge Scenario RD

  7. Input Assumption - Site Data Mauna Kea median seeing conditions at  = 0.5 m: • r0 = 18 cm.  = 3 cm. L0 = 75 m. • 0 = 2.5 arcsec • fG = 39 Hz • L0 = 75 m • Cn2 profile from data Median sodium density = 4 x 109 atoms/cm2 Sodium column density RD

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