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Update to End to End LSST Science Simulation

This update provides information on the status of the LSST Science End-to-End Simulator, including sky models, atmospheric and detector models, and validation code. It also outlines the near-term goals for science applications and simulation studies.

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Update to End to End LSST Science Simulation

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  1. Update to End to End LSST Science Simulation Garrett Jernigan and John Peterson December, 2004 Status of the Science End-to-End Simulator: 1. Sky Models (two modes) Grids of stars / FITS interface for arbitrary image 2. Atmospheric Model Kolmogorov refractive layer models 3. Optics and Deformations Geometric ray trace with perturbations 4. Detector Model Conversion depth/Diffusion (Andy Rasmussen) Telescope diffraction

  2. Three Types of Simulators: 1. Component Design, Modeling, and Simulation: (a required routine engineering activity) 2. Science End-to-End Simulator: (early; informs design; 10% accuracy) 3. Engineering End-to-End simulator: (late; follows design in detail, <1% accuracy)

  3. Atmospheric Models Raytrace Code: - Monte Carlo of photons through Atm. (also optics and detector: end-to-end) - Multi-layer Atmospheric Model (each layer a frozen screen) - Modified Kolmogorov Model for each layer (Random Gaussian with outer scale) - Now: Each Layer contains 256x256x256 cube (3D Kolmogorov Model) - Soon: Each layer: 2048x2048x16 (also 3D Kolmogorov Model) - Refractive Approximation for Raytrace with Phase Screen - Modeling ground/dome effects (not currently included) Validation Code: - PSF determined from multiple phase screen with full diffraction (FFTs required) - Non-Kolmogorov Models (atmospheric wedge, wind sheer driven flows) - Time Dependent Kolmogorov Models (drop frozen screen assumption) - Numerical Hydrodynamic Simulations

  4. Near Term Goals (Science Applications) - Results on PSF atmosphere only (raytrace and validation code results) - Distribution of seeing and ellipticity of PSF - Semi-analytic form for e1 and e2 de-correlation versus angle for stars - Numerical simulation to verify semi-analytic model - Determine the effects of LSST optics (Zernike perturbations only) - Simple examples of the shear of ideal galaxies (PSF corrected) - Some simple tests to estimate effects of non-Kolmogorov models - Validate with real data (Guide stars ?; large aperture telescopes ?)

  5. 3-D atmospheric density Density Slice Kolmogorov Model Numerical simulation (Porter)

  6. Single layer phase screen based on Kolmogorov spectrum Refraction raytraced Phase Map Vector Perturbations

  7. Multilayer Models Altitude Structure Function Wind Speed Vernin et al., Gemini RPT-A0-G0094 from Sebag

  8. Atmospheric Diffraction Telescope Diffraction

  9. Detector Model: (Rasmussen) Refraction for light entering the Si surface reduces the cone angle of the incident beam (cf. Radeka) Finite electric field at point of interaction leads to a lateral diffusion during drift time to the channel. Electric field function is dependent on doping density profile in the Si and bias voltage. Interaction length into Si is strongly wavelength dependent, and also temperature dependent, particularly at long wavelength. Photon detection by CCD alters the position of best focus and also the PSF.

  10. Telescope Raytrace + Perturbations: Fast Geometric Optics code Finds ray intercept / refraction or reflection Handles non-sequential straylight Has arbitrary rotations, translations, and perturbations Perturbations: Residual wavefront Zernike coefficients as deformations and vary as function of time

  11. Telescope (No perturbations) PSFs separated by 10 arcseconds centered at ( +1.5, 0) degrees Dotted grid is 10 microns PSFs separated by 0.6 degrees centered at (0,0) Dotted grid is 10 microns

  12. Optics+Perturbations on Primary PSFs separated by 10 arcseconds centered at ( +1.5, 0) degrees Dotted grid is 10 microns PSFs separated by 0.6 degrees centered at (0,0) Dotted grid is 10 microns

  13. Optics+Perturbations on Secondary PSFs separated by 10 arcseconds centered at ( +1.5, 0) degrees Dotted grid is 10 microns PSFs separated by 0.6 degrees centered at (0,0) Dotted grid is 10 microns

  14. Optics+Perturbations on Tertiary PSFs separated by 10 arcseconds centered at ( +1.5, 0) degrees Dotted grid is 10 microns PSFs separated by 0.6 degrees centered at (0,0) Dotted grid is 10 microns

  15. Telescope: Optics+ 10 realizations of zernike perturbations (all mirrors) PSFs separated by 10 arcseconds centered at ( +1.5, 0) degrees Dotted grid is 10 microns PSFs separated by 0.6 degrees centered at (0,0) Dotted grid is 10 microns

  16. Telescope (w/ Perturbations)+Atmosphere PSFs separated by 10 arcseconds centered at ( +1.5, 0) degrees Dotted grid is 10 microns PSFs separated by 0.6 degrees centered at (0,0) Dotted grid is 10 microns

  17. Telescope+Perturbations+Atmosphere+Wind PSFs separated by 10 arcseconds centered at ( +1.5, 0) degrees Dotted grid is 10 microns PSFs separated by 0.6 degrees centered at (0,0) Dotted grid is 10 microns

  18. Sky Image Simulations HDF galaxies Image raytraced+ perturbations+ atmosphere+wind

  19. Ellipticity Residual Studies Zernike Pert. on all mirrors Perfect telescope

  20. Ellipticity Vectors: computed from weighted Qij moments ellipticity shot noise ~ 1/sqrt(N)

  21. Ellipticity Residuals as a function of separation Preliminary

  22. Many investigations continuing to understand ellipticity changes: Telescope: (current sims give e=0.3 for perfect telescope e=0.1 for 10 realizations of up to 5th order pert. decorrelated=a degree for all mirrors) # of Zernikes (more reduces corr.) amplitude of Zernikes (affects rel. importance) which mirror (should be less correlated w/ tertiary, but not so obvious?) rate of changes of Zernikes (affect corr.) Atmosphere: (current sims give e=0.05, decorrelated=40”) seeing/structure function (affect rel. importance) outer Kolmogorov scale (increase e) wind (reduces e) layer height (reduces correlation) non-Kolmogorov effects (ellip?)

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