Calibration

Calibration is performed by fitting observed visibilities to a model visibility.

The scalar equation to be minimised is:

\[S = \sum_{t,f}^{}{\sum_{i,j}^{}{w_{t,f,i,j}\left| V_{t,f,i,j}^{\text{obs}} - J_{i}{J_{j}^{*}V}_{t,f,i,j}^{\text{mod}} \right|}^{2}}\]

The least squares fit algorithm uses an iterative substitution (or relaxation) algorithm from Larry D’Addario in the late seventies.

ska_sdp_func_python.calibration.chain_calibration Module

Functions to solve for and apply chains of antenna/station gain tables. See documentation for further information.

`apply_calibration_chain`(vis, gaintables[, ...])	Update the Visibility using the calibrated solutions in the form of GainTables.
`calibrate_chain`(vis, model_vis[, ...])	Calibrate using algorithm specified by calibration_context.
`create_calibration_controls`()	Create a dictionary containing default chain calibration controls.
`solve_calibrate_chain`(vis, model_vis[, ...])	Solve GainTables by fitting an observed visibility to a model visibility.

Functions to solve for delta-TEC variations across the array

`solve_ionosphere`(vis, modelvis, xyz[, ...])	Solve for ionospheric delay as a function of station location.
`set_cluster_maps`(cluster_id)	Generate vectors to help convert between station and cluster indices.
`set_coeffs_and_params`(xyz, cluster_id[, ...])	Initialise coefficients and parameters.
`get_param_count`(param)	Return the total number of parameters across all clusters.
`apply_phase_distortions`(vis, param, coeff, ...)	Update visibility model with new fit solutions.
`build_normal_equation`(vis, modelvis, param, ...)	Build normal equations.
`cluster_design_matrix`(mdl_data, mask0, ant1, ...)	Generate elements of the design matrix for the current cluster.
`solve_normal_equation`(AA, Ab, param[, it])	Solve the normal equations and update parameters.
`update_gain_table`(gain_table, param, coeff, ...)	Add new solutions to gaintable.

Utilities to support ionospheric calibration and the generation of ionospheric phase screens.

`decompose_phasescreen`(x, y, r_0[, beta])	Generate eigenvectors for phase-screen pierce points.
`displace_phasescreen`(interpolated_screen, ...)	Distort interpolated phasescreen to maintain Kolmogorov statistics.
`interpolate_phasescreen`(input_screen)	Bilinear interpolation of a two dimensional phase screen.
`standardise_eigenvectors`(evec)	Fix arbitrary eigenvector signs.
`zern`(m, n, rho, phi)	Generate Zernike polynomial values.
`zern_array`(nm, x, y[, noll_order])	Generate an array of all Zernike polynomials up to a given degree.

Jones matrix related operations.

apply_jones(ej, cfs[, inverse, min_det])

Apply Jones matrix (or inverse).

Functions for calibration operations.

`apply_gaintable`(vis, gt[, inverse, use_flags])	Apply a GainTable to a Visibility. The corrected visibility is::.
`concatenate_gaintables`(gt_list[, dim])	Concatenate a list of GainTables.
`multiply_gaintables`(gt, dgt[, time_tolerance])	Multiply two GainTables.

Functions to solve for antenna/station gain.

solve_gaintable(vis[, modelvis, gain_table, ...])

Solve a gain table by fitting an observed visibility to a model visibility.