Lessons learned from station calibration

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Lessons learned from station calibration
Parisa Noorishad, Arnold van Ardenne and Thijs
van der HulstAAVP2011, 12th- 16th Dec.
2011Dwingeloo- The Netherlands
Parisa NoorishadAAVP2011, 12th- 16th Dec.
2011Dwingeloo- The Netherlands
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AA-station calibration (gain calibration)

• Aim receivers' DI-complex gain
• Methods used by far
• Model-based methods (covariance fitting)
• Holographic method
• Redundancy (in case of a regular array)
• Deterministic effects not to dismiss
• Non-identical beam of the station elements
• Beamformed beam of the station elements (complex
  weights of digital beam)
• Beam projection/sky rotation
• ...

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Some Demonstrations
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1.1 Non-identical beams
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1.2 Non-identical beams
24th Nov 2009 212904 UTC, observing CasA
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2.1 Complex weights of digital beam
Digital Beamforming weights f 160MHz
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2.2 Phase of DI-complex gain
Tracking CasA, 24th Nov 2009 _at_ 22 12 19 UTC
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2.3 Phase of DI-complex gain
Tracking CygA, 28th Nov. 2009 _at_ 19 55 54 UTC
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Suggestions for AA- gain calibration

• Not to accept any direction dependency or rapid
  variations over time or frequency in our gain
  calibration results.
• To know the deterministic effects (e.g. beam
  shape) well and separate them from the stochastic
  ones (e.g. correlated noise, ionosphere, etc.).
• To know the beam by EM-studies.
• To set identical beams as a figure of merit.
• To correct for them (especially beam effect)
• This hopefully leads to less variance on our
  parameters of interest in AA-calibration.