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AIPS. WSRT & VLA. Y-shape array A - 21 km B - 10 km C - 3.6 km D - 0.6 km 27 telescopes Ø25m. east - west array ~ 2.8 km 14 telescopes Ø25m. GMRT & MERLIN. random centre & Y-shape array 30 km 30 telescopes Ø45m. 7 telescopes 217 km Lovel Ø76m. VLBA &
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WSRT & VLA Y-shape array A - 21 km B - 10 km C - 3.6 km D - 0.6 km 27 telescopes Ø25m east - west array ~ 2.8 km 14 telescopes Ø25m
GMRT & MERLIN random centre & Y-shape array 30 km 30 telescopes Ø45m 7 telescopes 217 km Lovel Ø76m
VLBA & EVN & VLBI 10 telescopes Ø25m
dirty & clean Image
UV coverage & Image 12 hours WSRT observations
Why Calibration and Editing? • Synthesis radio telescopes, though well-designed, are not perfect • (e.g., surface accuracy, receiver noise, polarization purity, stability, etc.) • Need to accommodate engineering • (e.g., frequency conversion, digital electronics, etc.) • Hardware or control software occasionally fails or behaves unpredictably • Scheduling/observation errors sometimes occur (e.g., wrong source positions) • Atmospheric conditions not ideal (not limited to “bad” weather) • RFI radio frequency interference
That's why! BAD GOOD
visibilities = amplitude[t] * e(i[t]) VLA observations amplitude versus time good diagnostic for bad data amplitude versus UV distance
www-astro.physics.ox.ac.uk/~hrk/AIPS_TUTORIAL/HRK_AIPS_1.htmlwww-astro.physics.ox.ac.uk/~hrk/AIPS_TUTORIAL/HRK_AIPS_1.html