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Challenge : Low frequency foreground – hot, confused sky

Challenge : Low frequency foreground – hot, confused sky. 0.5 to 5.0 GHz. HI 21cm signal ~ 10 mK Foreground: T ~ 100 (  /200 MH z)^-2.6 K Highly ‘confused’: 1 source/deg^2 with S 140 > 1 Jy Synch. smooth ~ 100MHz vs. 21cm lines ~ 1 MHz.

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Challenge : Low frequency foreground – hot, confused sky

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  1. Challenge: Low frequency foreground – hot, confused sky 0.5 to 5.0 GHz • HI 21cm signal ~ 10 mK • Foreground: T ~ 100 (/200 MHz)^-2.6 K • Highly ‘confused’: 1 source/deg^2 with S140 > 1 Jy • Synch. smooth ~ 100MHz vs. 21cm lines ~ 1 MHz

  2. Chromatic aberration: Frequency differencing with MHz channels doesn’t work well due to frequency dependent far-out sidelobes 142, 174 MHz

  3. Simulation: effects of residual calibration errors 6C source counts > 1Jy (Smax = 200 Jy)

  4. UVSUB ~ ‘real-time’ source removal IMLIN ~ post-processing freq fitting (3rd order)

  5. Datta+ 09 0.1% 1% For errors constant over 1 day: DNR requirement ~ 0.2% calibration errors

  6. Datta + Bowman in prep 300 hours 0.1% calibration errors UVSUB IMLIN

  7. J. Aguirre, D. Jacobs (Penn), C. Carilli (NRAO) • Focus: Reionization (power spec,CSS,abs) • Very wide field: single dipole + screen • Correlator: FPGA-based from Berkeley wireless lab • Staged engineering: maintain GB test installation  PWA  PSA

  8. PAPER: Staged Engineering • Broad band sleeve dipole + flaps • FPGA-based ‘pocket correlator’ from Berkeley wireless lab • S/W Imaging, calibration, PS analysis: AIPY + Miriad/AIPS => Python + CASA, including ionospheric ‘peeling’ calibration 100MHz 200MHz Beam response BEE2: 5 FPGAs, 500 Gops/s

  9. Western Australian deployment in 2008

  10. PAPER/WA -- 4 Ant, July 2007 RMS ~ 1Jy; DNR ~ 1e4 CygA 1e4Jy Parsons et al. 2009 120MHz 180MHz

  11. Paper – South Africa • Karoo site • 16 elements by Nov 1, 2009 • 32 elements possible by Jan 1

  12. PGB 16 dipole, 3x24hr • scale -10 to 10 Jy • rms ~ 100 mJy • FWHM ~ 20’

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