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AAO Fibre Instrument Data Simulator

An overview of the Data Simulator for the HERMES and SAMI instrument projects, detailing its components, specifications, simulation results, and verification processes. The simulator aids in producing detector images for astronomical spectrographs.

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AAO Fibre Instrument Data Simulator

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  1. AAO Fibre Instrument Data Simulator ROE Workshop 2011 Michael Goodwin Tony Farrell Gayandhi De Silva Scott Smedley Australian Astronomical Observatory 10 October 2011

  2. Data Simulator Goal • Construct an end-to-end software simulation tool that produces detector images (flat, arc and object) based on the fibre-fed instrument designs. • A verification tool for the engineers, instrument scientists and astronomers HERMES 4-channel, N=392, R~28,000, S/N=100 (late 2012) is a complex astronomical spectrograph requiring a simulation tool to assist in the early performance and design verification. Samuel C. Barden, et al. Proc. SPIE 7735, 773509 (2010).

  3. Data Simulator Overview Pre-computed optical data & efficiency response data

  4. Atmosphere Simulator Components The data simulator system model abstracts the physical design of the fibre instrument. This is achieved by translating the data simulator requirements and specifications into suitable model components.

  5. Specifications – Science Object (HERMES) • high resolution (0.02Å) synthetic stellar spectra from 300nm to 1.8μm with solar and alpha-enhanced composition by P. Coelho et. Al (2005)

  6. Specifications – Atmosphere (HERMES) • sky background is modelled as reflected solar spectra from the Moon [Krisciunas, K. and Schaefer, PASP 103, 1033–1039 (1991)] • sky emission is modelled from observations with the HIRES echelle spectrograph on the Keck I telescope. [Osterbrock, D. E. et al., PASP 108, 277 (1996)]

  7. Specifications - Telescope Specifies the Anglo-Australian-Telescope (AAT) and the 2dF top-end corrector optics.

  8. Specifications - Instrument

  9. Model Data (HERMES) Zemax traces a matrix of slit field locations with wavelengths to determine detector locations (chief rays) and corresponding geometrical image (resolution element). Distortion polynomials Aberration images (geometrical) The data simulator approximates a spatial variant convolution by dividing detector into regions based on geometrical image matrix (resolution elements). The resolution element is convolved with ‘impulse’ tramline. Matlab interpolates the detector locations in the spatial and wavelength dimensions and then fits characteristic polynomials (cubic) for fibres 1-400 tramlines

  10. Efficiencies Data simulator imports realistic efficiency curves from detailed spreadsheet model. HERMES

  11. Resolving Power (HERMES) R R=29,000 R=28,000 R=27,000 wav Data simulator resolving power at detector is determined by Zemax model.

  12. Implementation Verification Verification of data simulator implementation (Linux) with that of the simulator model, Zemax / Matlab (solid line). implementation = model

  13. Verification with AAOmega Model can be fitted (mean error ~0.34 pixels) to real data (dashed line) with a simple transformation: y-offset = 5.5 pixels; scale factor = 0.994; Rotation = -0.17 degrees (i.e. clockwise) model ~ observed mechanical alignment optical tolerances Verification of model (solid line) with AAOmega observational data (image with dashed line).

  14. Simulated Output (HERMES) exposure time of 1800s using (fibers 391-400) assigned synthetic stellar spectra having Teff=4750K and brightness mv=12.5 using (fibers 381- 390) assigned spectra Teff=4250K and brightness mv=15.0.

  15. Scattering Simulation (HERMES) No Scattering Logarithmic scaling – flat field Scattering 3% Energy Sigma = 37 pixels AAOmega Scattering 1% Energy Sigma = 37 pixels

  16. VPH Littrow Ghost Simulation HERMES * Ghost analysis is still ongoing

  17. Data Simulator Results (HERMES) • Gayandhi De Silva • Astronomer (HERMES project scientist)

  18. Data Simulator (SAMI) The Sydney-AAO Multi-object IFS (SAMI). N=13, R~1800-4500, hexabundles (61-element) deployed 1 degree FoV (Commission run #1 : 1-4 July 2011) AAO Observer, August 2011, Edition #120

  19. Data Simulator Results (SAMI - FLAT) Simulated Actual – First Light

  20. Conclusions • Data simulator producing detector images for HERMES and SAMI instrument projects • Simulated detector images have been used in developing the data reduction software • Science analysis of simulated data in progress by the HERMES project scientist

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