ska_sdp_instrumental_calibration.xarray_processors.predict module

ska_sdp_instrumental_calibration.xarray_processors.predict.predict_vis(vis, gsm, soln_time, soln_interval_slices, beams_factory=None, station_rm=None)[source]

Predict visibilities from a Global Sky Model (Distributed).

This function computes expected visibilities by evaluating the radio interferometry measurement equation. It uses a Global Sky Model (GSM) to generate local sky models for specific time steps and applies primary beam effects if a beam factory is provided.

The prediction is distributed and chunked:

  1. Time: Iterates over solution intervals defined by soln_time and soln_interval_slices.

  2. Frequency: Handled via Dask chunking on the input visibility object.

Parameters:

  • vis (Visibility) -- The template visibility dataset. Its structure (time, frequency, baselines, UVW coordinates) determines the grid for the prediction.

  • gsm (GlobalSkyModel) -- The sky model source. The method get_local_sky_model is called for each solution time to retrieve sources above the horizon.

  • soln_time (ndarray) -- Array of timestamps (float, seconds) representing the center of each solution interval.

  • soln_interval_slices (list[slice]) -- A list of slice objects. Each slice corresponds to a timestamp in soln_time and selects the range of time indices in vis that fall within that interval.

  • beams_factory (BeamsFactory, default: None) -- Factory to generate antenna primary beams. If None, the sky model is assumed to be multiplied by unity (no beam attenuation).

  • station_rm (DataArray, default: None) -- Station-based Rotation Measures (RM) for ionospheric Faraday rotation simulation. If provided, it is passed to the prediction kernel.

Return type:

Visibility

Returns:

A new Visibility object containing the predicted data in the vis variable. Metadata and coordinates are preserved from the input vis.

Raises:

AssertionError -- If the number of solution times does not match the number of interval slices.