Advertisement

Wide Field Imaging

  • Sebastiaan van der Tol
Chapter
Part of the Astrophysics and Space Science Library book series (ASSL, volume 426)

Abstract

Visibilities cannot be fully corrected to compensate for direction dependent effects. Corrected visibilities are valid for one direction only. By contrast, images can be corrected in a direction dependent fashion. For example, an image can be adjusted to correct for the direction dependent sensitivity pattern of a primary antenna beam. However, this image-plane correction can only be properly applied if the beam is not time dependent. Effects that are both time and direction dependent can only be corrected by the imager, during the process of inversion from the visibility to the image domain. A-projection is one example of an algorithm that can apply these corrections efficiently. For LOFAR data, the AWimager software implements this algorithm. This chapter describes the A-projection algorithm, its implementation in AWimager, as well as tips for its usage and performance tuning.

References

  1. Bhatnagar, S., Cornwell, T.J., Golap, K., Uson, J.M.: Astron. Astrophys. 487, 419 (2008)ADSCrossRefGoogle Scholar
  2. Briggs, D.S., Schwab, F.R., Sramek, R.A.: In: Taylor, G.B., Carilli, C.L., Perley, R.A. (eds.) Synthesis Imaging in Radio Astronomy II. Astronomical Society of the Pacific Conference Series, vol. 180, p. 127 (1999)Google Scholar
  3. Clark, B.G.: Astron. Astrophys. 89, 377 (1980)ADSGoogle Scholar
  4. Cornwell, T.J., Humphreys, B.: Analysis of convolutional resampling algorithm performance, SKA memo 132, Technical report, SKA Organisation (2011)Google Scholar
  5. Cornwell, T., Braun, R., Briggs, D.S.: In: Taylor, G.B., Carilli, C.L., Perley, R.A. (eds.) Synthesis Imaging in Radio Astronomy II. Astronomical Society of the Pacific Conference Series, vol. 180, p. 151 (1999)Google Scholar
  6. Cornwell, T.J., Golap, K., Bhatnagar, S.: IEEE J. Sel. Top. Signal Process. 2, 647 (2008)ADSCrossRefGoogle Scholar
  7. Offringa, A.R., McKinley, B., Hurley-Walker, N., et al.: Mon. Not. R. Astron. Soc. 444, 606 (2014)ADSCrossRefGoogle Scholar
  8. Slepian, D., Pollak, H.O.: Bell Syst. Tech. J. 40, 43 (1961)CrossRefGoogle Scholar
  9. Tasse, C., van der Tol, S., van Zwieten, J., van Diepen, G., Bhatnagar, S.: Astron. Astrophys. 553, A105 (2013)CrossRefGoogle Scholar
  10. Thompson, A.R.: In: Taylor, G.B., Carilli, C.L., Perley, R.A. (eds.) Synthesis Imaging in Radio Astronomy II. Astronomical Society of the Pacific Conference Series, vol. 180, p. 11 (1999)Google Scholar
  11. Thompson, A., Moran, J., Swenson, G.: Interferometry and Synthesis in Radio Astronomy. Wiley, Hoboken (2001)CrossRefGoogle Scholar
  12. van Haarlem, M.P., Wise, M.W., Gunst, A.W., et al.: Astron. Astrophys. 556, A2 (2013)CrossRefGoogle Scholar

Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  1. 1.ASTRONDwingelooThe Netherlands

Personalised recommendations