Self calibration is essentially the same technique as hybrid mapping, except it uses antenna/IF gains instead of the phase and amplitude closure relations explicitly. Self-calibration takes advantage of the fact that many of the systematic errors in visibility measurements may be ascribed to individual array elements. This means that baselines are affected by n sources of error, which are the so-called antenna/IF gains. Given a rough estimate of the true source visibility (the first iteration CLEANed map), one may solve for the unknown gains. One can then make a map, inverse transform back, and repeat the process. A rule of thumb is to exclude all model CLEAN components beyond the first negative one.
Self calibration is a nonlinear procedure, and no proof of convergence has ever been given.
CLEAN Algorithm, Hybrid Mapping, Isoplanicity Assumption, Redundancy Calibration
References
AIPS package HELP file on ASCAL.
Cornwell, T. and Fomalont, E. B. "Self-Calibration." Ch. 9 in Synthesis Imaging in Radio Astronomy: Third NRAO Summer School, 1988 (Ed. R. A. Perley, F. R. Schwab, and A. H. Bridle). San Francisco, CA: Astronomical Society of the Pacific, 1989.
Pearson, T. J. and Readhead, A. C. S. "Image Formation by Self-Calibration in Radio Astronomy." Ann. Rev. Astron. Astrophys. 22, 97-130, 1984.
