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SKA: Configurations and Simulations

SKA: Configurations and Simulations. Ramesh Bhat Colin Lonsdale Roger Cappallo Shep Doeleman Divya Oberoi Joanne Attridge. MIT Haystack Observatory. Simulator Functions. A general purpose tool for LOFAR/SKA studies Create Synthetic Data Sets

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SKA: Configurations and Simulations

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  1. SKA: Configurations and Simulations Ramesh Bhat Colin Lonsdale Roger Cappallo Shep Doeleman Divya Oberoi Joanne Attridge MIT Haystack Observatory

  2. Simulator Functions • A general purpose tool for LOFAR/SKA studies • Create Synthetic Data Sets • Performance simulations, at high level design specs • Realistic effects: Ionosphere, Variable beams, Skies • Configuration Studies • Explore Design Parameter Space: • Automation to allow efficient searches • Identify trends in performance • Testing Calibration and Postprocessing • Direct access to structures solved for • Controlled environment for isolation of effects • Test New Postprocessing Algorithms • Science Applications (e.g. EOR)

  3. Includes FITS Image import Variable station beams Thermal Noise (Rx) Arbitrary array configuration. Arbitrary station config. Gaussian sources Arbitrary time/freq obs. True parallelization in time. Functional parallelization otherwise Exportable to FITS Script driven to support automated parameter searches 4-D Ionosphere with line integration. Site mask incorporation Sky noise due to Galactic Background. Will Include Polarization Realistic skies Source Spectral Index Out-of-beam source contributions (CasA in sidelobes, etc…) Extension to 3-D FFTs for wide field imaging. RFI (limited) Simulator Status

  4. Functional Flow Diagram config generator LOsim obs_spec proc_spec skies sites array Script driven Simulator Module Calibration structures for comparison (u,v) FITS MIRIAD PSF Stats Imaging Fidelity

  5. Image Import and Simulation After Before

  6. Effect of Variable Station Beams

  7. Simulator Beowulf • 20 nodes • 2.4 GHz P4, $900 each • 1 Gbyte of RAM • 60 Gbyte of disk • Gigabit ethernet switch • 24-port • $2000 • UPS and misc • Excellent price/performance • 50-80 Gflops • 1.5 Tbytes of disk • <$25,000

  8. Configuration Studies - in progress ProposedUSSKAConfiguration • Parameter space is vast: • Configurations (log spirals, random,…) • Number of stations (variable sensitivity …) • No of elements/station, Staion layout • Bandwidth and integration time • Sky properties and observing geometry • Frequency, polarization, spectrum, … • Weighting schemes, tapering • Ranges of corrupting influences. • Strategy: parameterize configurations and explore limited ranges, identify trends • Input from ALMA, ATA, SMA studies. Inner~100kmarray

  9. Figures of Merit: • PSF statistics: RMS, size, min, max, deviation. Computed for declination, integration, bw. • Cable Length (Prim’s Algorithm). • Sensitivity Loss due to: weighting, fixed taper. • PSF statistics for Inner compact array/core. • Image fidelity for a few benchmark images. • Robustness: impact of random station loss. • Calibratability: requires calibration software.

  10. Searching in Parameter Space

  11. Configuration Optimization Figures of Merit: PSF RMS vs Radius PSF Beam Size Cable Length

  12. Configuration Optimization Figures of Merit weighted And Combined into Optmization function

  13. Configuration Editor

  14. Progress so far and Future Work • Good progress with the simulator package, downstream pipeline, automation, FOMs. • Many configs tested so far, calculation of FOMs. • Continue extensive configuration studies • Explore N, Nant/station, station layout, etc. • Range of observing conditions, time/bw effects. • Configuration evaluation along FOM axes • Continue Code Development • New modules based on priority

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