This module provides basic radio interferometry calibration utilities. Calibration is the process of estimating the 2\times 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 :ref:`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\times 2 matrices. This is
refered to as diag calibration. The final
scenario is when both the full 2\times 2
Jones matrices and the full 2\times 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.
.. currentmodule:: africanus.calibration.utils
.. autosummary::
corrupt_vis
residual_vis
correct_vis
compute_and_corrupt_vis
.. autofunction:: corrupt_vis
.. autofunction:: residual_vis
.. autofunction:: correct_vis
.. autofunction:: compute_and_corrupt_vis
.. currentmodule:: africanus.calibration.utils.dask
.. autosummary::
corrupt_vis
residual_vis
correct_vis
compute_and_corrupt_vis
.. autofunction:: corrupt_vis
.. autofunction:: residual_vis
.. autofunction:: correct_vis
.. autofunction:: compute_and_corrupt_vis
.. currentmodule:: africanus.calibration.phase_only
.. autosummary::
compute_jhr
compute_jhj
compute_jhj_and_jhr
gauss_newton
.. autofunction:: compute_jhr
.. autofunction:: compute_jhj
.. autofunction:: compute_jhj_and_jhr
.. autofunction:: gauss_newton
.. currentmodule:: africanus.calibration.phase_only.dask
.. autosummary::
compute_jhr
compute_jhj
.. autofunction:: compute_jhr
.. autofunction:: compute_jhj