This module provides basic radio interferometry calibration utilities. Calibration is the process of estimating the 2 × 2 Jones matrices which describe transformations of the signal as it propagates from source to observer. Currently, all utilities assume a discretised form of the radio interferometer measurement equation (RIME) as described in rime-api-anchor.
Calibration is usually divided into three phases viz.
- First generation calibration (1GC): using an external calibrator to infer the gains during the target observation. Sometimes also refered to as calibrator transfer
- Second generation calibration (2GC): using a partially incomplete sky model to perform direction independent calibration. Also known as direction independent self-calibration.
- Third generation calibration (3GC): using a partially incomplete sky model to perform direction dependent calibration. Also known as direction dependent self-calibration.
On top of these three phases, there are usually three possible calibration scenarios. The first is when both the Jones terms and the visibilities are assumed to be diagonal. In this case the two correlations can be calibrated separately and it is refered to as diag-diag calibration. The second case is when the Jones matrices are assumed to be diagonal but the visibility data are full 2 × 2 matrices. This is refered to as diag calibration. The final scenario is when both the full 2 × 2 Jones matrices and the full 2 × 2 visibilities are used for calibration. This is simply refered to as calibration. The specific scenario is determined from the shapes of the input gains and the input data.
This module also provides a number of utilities which are useful for calibration.
africanus.calibration.utils
corrupt_vis residual_vis correct_vis compute_and_corrupt_vis
corrupt_vis
residual_vis
correct_vis
compute_and_corrupt_vis
africanus.calibration.utils.dask
corrupt_vis residual_vis correct_vis compute_and_corrupt_vis
corrupt_vis
residual_vis
correct_vis
compute_and_corrupt_vis
africanus.calibration.phase_only
compute_jhr compute_jhj compute_jhj_and_jhr gauss_newton
compute_jhr
compute_jhj
compute_jhj_and_jhr
gauss_newton
africanus.calibration.phase_only.dask
compute_jhr compute_jhj
compute_jhr
compute_jhj