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. Simulator Status 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)

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

5. Image Import and Simulation Before After

6. Effect of Variable Station Beams

7. 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 Simulator Beowulf

8. Configuration Studies - in progress 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. Proposed USSKA Configuration Inner ~100 km array

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