Bootstrapping for antenna gains

For one of our observations with the GMRT at P-band, all good point source calibrators were either too weak or too far away in the sky from the target source. We therefore observed $J1829+487$, a moderately resolved source, as the phase calibrater. This source is resolved at baselines longer than $2K\lambda$ which means that we could use it to determine the phase offsets only for the Central square antennas. Therefore, to image the target source at full resolution, we needed an image-plane model for the calibrater. The antenna-based calibration allows one to solve for the antenna gains without using the full set of baseline data. In the following, we demonstrate a method which can be exploited to bootstrap and determine phase corrections for the whole array.

Figure: Figure showing calibrated visibilities for Central-square antennas only. The first and the second panel show the amplitude and phase respectively while the last panel shows the corresponding image for $J1829+487$. The source is unresolved till a baseline length of $2K\lambda$.