SKA SDP Pointing Offset Calibration Pipeline

This is a repository for the SDP pointing offset calibration pipeline. This repository reads Measurement Sets, optionally applies a static RFI mask (pulled from ska-telmodel-data in real time) and/or select some frequency range of interest, and then fits the 2-D Gaussian primary beams to the visibility or gain amplitudes.

The fitted parameters are the Gaussian centre (provides the Cross-elevation and Elevation offsets), width (the fitted beamwidth), and height (in arbitrary units) and their uncertainties. These fitted parameters are then written to an HDF5 file created from a PointingTable and a text file for further analysis (see Data products of the pointing pipeline).

The pipeline reads Measurement Sets using the Visibility class in ska-sdp-datamodels. When an RFI mask is applied and/or some frequency range is selected, the modified visibility is created with the ska-sdp-datamodels Visibility class for gain calibration (un-normalised G terms) or provides easy access to the visibilities and their associated parameters when fitting to them. These gains of each dish are solved for using the gain solver in the ska-sdp-func-python library. The primary beam modelling and fitting is performed with scikits.fitting following the procedure used by the SARAO team for computing the pointing offsets for the MeerKAT array.

The implementation of the pointing offset calibration pipeline is described in detail in the Observing Modes section.

The current pipeline can be executed as a CLI-based command line app (see pointing_offset_cli), or deployed in SDP using the pointing offset script.

Installation

• Installation Instructions
• Docker image

Releases

• Changelog

Design

• Algorithms and Tools
• Observing Modes
  • Single-baseline Interferometry
  • Standard Interferometry
• Processing Chunks of Visibilities
  • Frequency Range Selection
  • Splitting into Frequency Chunks
  • Removing Bad Frequency Channels
• Applying static RFI mask
  • Generating static RFI mask in HDF5 format
  • Uploading the static RFI mask to Telescope Model Data Repository
• Handling Incomplete Data
  • Missing Visibilities
  • Missing Dish Pointings
  • Data from Slews
• Averaging and Propagation of Uncertainties
  • Averaging the Visibility and Gain Amplitudes
  • Averaging the Fitted Parameters
• Validity of the Gaussian Fits
  • Understanding Beam Squint
• Fitting the Beams to the Stokes I Amplitudes
  • Fitting the Beams to the Stokes I Visibility Amplitudes
  • Fitting the Beams to the Stokes I Gain Amplitudes
• Fitting the Beams to the Parallel-hands Gain Amplitudes

Operation

• Running the pipeline in SDP
• Running the pipeline as standalone

Data products and outputs

• Data products of the pointing pipeline

API

• API

Indices and tables

• Index

• Module Index

• Search Page