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Lessons Learned in Station Calibration for Accurate Radio Astronomy

This paper discusses the insights gained from the calibration of radio receivers at the AA-station, focusing on the DI-complex gain. Various model-based methods, holographic approaches, and redundancy solutions were employed to address the effects of non-identical beams among station elements. Key demonstrations and tracking of sources like CasA and CygA illustrated the complexities involved in achieving precise calibration. Recommendations include understanding deterministic effects, eliminating direction dependency, and establishing identical beams as a performance standard to reduce variance in calibration outcomes.

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Lessons Learned in Station Calibration for Accurate Radio Astronomy

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  1. 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

  2. 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 • ...

  3. Some Demonstrations

  4. 1.1 Non-identical beams

  5. 1.2 Non-identical beams 24th Nov 2009 21:29:04 UTC, observing CasA

  6. 2.1 Complex weights of digital beam Digital Beamforming weights f= 160MHz

  7. 2.2 Phase of DI-complex gain Tracking CasA, 24th Nov 2009 @ 22: 12: 19 UTC

  8. 2.3 Phase of DI-complex gain Tracking CygA, 28th Nov. 2009 @ 19: 55: 54 UTC

  9. 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.

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