prefactor

The LOFAR pre-facet calibration pipeline

prefactor is a pipeline to correct for various instrumental and ionospheric effects in both LOFAR HBA and LOFAR LBA observations. It will prepare your data so that you will be able to use any direction-dependent calibration software, like Rapthor, factor, or killMS.

It includes:

• removal of clock offsets between core and remote stations (using clock-TEC separation)
• correction of the polarization alignment between XX and YY
• robust time-independent bandpass correction
• ionospheric RM corrections with RMextract
• removal of the element beam
• advanced flagging and removal of bad data
• mitigation of broad-band RFI and bad stations
• direction-independent phase correction of the target, using a global sky model from TGSS ADR or the new Global Sky Model GSM
• detailled diagnostics

The full documentation can be found at the prefactor webpage.

WARNING: The current skymodel used for 3C295 is not using the Scaife&Heald flux density scale.

Software requirements

• DP3 (v5.1 or later)
• LoSoTo (v2.2.1 or later)
• LSMTool (v1.4.3 or later)
• EveryBeam (v0.2.0 or later)
• RMextract (v0.4.4 or later)
• AOFlagger (v3.1 or later)
• WSClean (v3.0 or later)
• IDG (v0.8 or later)
• LofarStMan
• Dysco (v1.2 or later)
• casacore
• Python3 (including matplotlib, scipy, and astropy)
• cwltool or toil-cwl-runner

Installation

Detailled installation instructions for prefactor are available at the prefactor documentation.

It is recommended to use Docker or Singularity for the use of software containers.

To download and install the repository run the following commands:

git clone https://git.astron.nl/eosc/prefactor3-cwl.git prefactor --depth 1
cd prefactor
pip3 install --upgrade $PWD

Running prefactor

Instructions how to setup and run prefactor are also available at the prefactor documentation.

Directory structure

prefactor contains the following sub-directories:

• Docker: contains the Dockerfile for creating the Docker image which contains all necessary software packages
• docs: contains the documentation for prefactor
• rfistrategies: strategies for statistical RFI mitigation using AOFlagger
• scripts: scripts that the pipeline calls to process data, generate plots, etc.
• skymodels: skymodels that are used by the pipeline (e.g. for demixing or calibrating the calibrator)
• solutions: template solutions for the use of non-supported calibrator sources
• steps: steps of the pipeline described in the Common Workflow Language (CWL)
• test_jobs: descriptions for running continouos integration (CI)
• workflows: pipeline workflow desriptions in the Common Workflow Language (CWL)

prefactor and its scripts were developed by:

• Alexander Drabent
• David Rafferty
• Mattia Mancini
• Marcel Loose
• Andreas Horneffer
• Francesco de Gasperin
• Marco Iacobelli
• Emanuela Orru
• Björn Adebahr
• Martin Hardcastle
• George Heald
• Soumyajit Mandal
• Carole Roskowinski
• Jose Sabater Montes
• Timothy Shimwell
• Sarrvesh Sridhar
• Reinout van Weeren
• Wendy Williams

Acknowledgements

This work was supported by the BMBF Verbundforschung under the grant 05A20STA.

The Prefactor procedure is described in this paper:

• de Gasperin, F.; Dijkema, T. J.; Drabent, A.; Mevius, M.; Rafferty, van Weeren, R., et al. 2019, A&A, 662, A5