1 / 24

Applicability and limitations of redundancy cal. in phased array stations

Applicability and limitations of redundancy cal. in phased array stations. Parisa Noorishad, Stefan Wijnholds, Arnold van Ardenne & Thijs van der Hulst YERAC2011, Manchester, 18 th -20 th July. 2011. A few words about new radio telescopes. Introduction & Motivation. Introduction:.

nasya
Télécharger la présentation

Applicability and limitations of redundancy cal. in phased array stations

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Applicability and limitations of redundancy cal. in phased array stations Parisa Noorishad, Stefan Wijnholds, Arnold van Ardenne & Thijs van der Hulst YERAC2011, Manchester, 18th -20th July. 2011

  2. A few words about new radio telescopes

  3. Introduction & Motivation

  4. Introduction: • [1] J. E. Noordam & A. G. de Bruyn, Nature, 14 oct. 1982 • [2] M. Wieringa, PhD thesis, Leiden Univ., 1991

  5. Introduction:

  6. Why redundancy? • Independent of a sky model, • Less sensitive to RFIs, • Computationally cheap and fast, • Simple to implement (important for SKA), • Could also be used as a diagnostic tool. • Regularity in a station configuration e.g. in MWA, HBA, EMBRACE.

  7. Redundancy in HBAs Introduction & Motivation

  8. Beam identicalness: CAESAR: Computationally Advanced and Efficient Simulator for Arrays [Rob Maaskant et al.]

  9. When redundancy fails:

  10. When redundancy holds:

  11. Checking the influence of non-identical sidelobes

  12. The systematic error due to non-identical sidelobes

  13. Quantifying that systematic error: The potential calibrator sources for RS208, on 24th of Nov. 2009 at 21:29:04 UTC and the systematic errors in the amplitudes and the phases of the redundant visibility due to the contribution of other strong sources through non-identical sidelobes.

  14. The plots of the residuals for corrected redundant visibilities

  15. Redundancy cal. Quality Introduction & Motivation

  16. CRB and the actual variance of the estimated parameters: We tracked CasA on 24th November 2009 from 15:25:43 UTC until 22:12:19 UTC.

  17. Redundancy cal. Limitations Introduction & Motivation

  18. Limitations of the redundancy calibration method: • Station configuration • Mutual coupling between the station elements which leads to: • Non-identical beams of the station elements • Presence of baseline dependent noise • SNR of the observed sky

  19. Station configuration and the condition of redundancy calibration

  20. One more point

  21. Model based cal. method: • The mutual coupling seems to be a non-dismissible effect (for phased array stations). • We need beam model of each individual station elements e.g. each tile at HBAs. [1] Wijnholds & van der Veen, 2009 [2] Wijnholds & van der Veen, 2010

  22. Summary & Conclusion

  23. Summary: • Applicability and limitations of the redundancy cal. for phased array station was investigated. • Conclusions: • Redundancy cal. is a stand-alone gain cal. method. • Using redundancy requires taking into account the parameters which affects its applicability and performance. • Identical beam; Mutual coupling seems to be a non-dismissible effect, no matter which method we use. • Next Step: • To do more rigorous CRB and Monte-Carlo analysis for two existing implementations of the redundancy method. • To evaluate the merit of the redundancy in UVW-space at the whole array level using SKA configuration.

More Related