CABB Data Reduction Review Summary of recommendations Dave Mc. Connell June 2011
Review of CABB data reduction • Review panel • Mark Wieringa (Chair), Mark Calabretta, Dave Mc. Connell, Tim Corwell, Bjorn Emonts, Emil Lenc, Jamie Stevens, Maxim Voronkov • Aim • Survey state of main reduction packages relevant to CABB data. • Provide recommendations for the way forward. CSIRO. Review of CABB data reduction software
Terms of Reference • Will Miriad continue to be the main reduction package for ATCA data for the next 5 years? • Does the combination of Miriad and ASKAPsoft enable all foreseeable ATCA data sets to be optimally reduced? • Should ATCA data reduction with CASA be actively tested and documented? • Should CASS consider contributing to CASA development? • What data reduction functionality is missing? How do the items rank in order of scientific priority? • How can the missing functionality be provided most easily, given the re- sources? CSIRO. Review of CABB data reduction software
Will Miriad continue to be the main reduction package for ATCA data for the next 5 years? • Yes • except for some special imaging and analysis problems • it is the most efficient package for the bulk of data reduction • Rise of ALMA will result in more experienced CASA users • Point of departure from Miriad may move earlier • After calibration • After uvsplit CSIRO. Review of CABB data reduction software
Miriad+ASKAPsoft = optimal reduction? • No, not at present • Some effort towards this would pay off • Keeps expertise “in house” • ASKAPSoft is not a general user package • Priority: pipeline processing of very large data volumes on special hardware • But: being able to test with CABB data is helpful for both ATCA and ASKAP • Use of CASA required • Import data • Image display & analysis • Selfcal CSIRO. Review of CABB data reduction software
Should ATCA data reduction with CASA be actively tested and documented? • Yes • Skip calibration path – Miriad better at this • Advantages • Complex imaging and deconvolution • Multi-Scale Clean • MFS (under development) • Automated clean boxes • Document • • Import of calibrated Miriad data Run multi-scale deconvolution algorithms Self calibration Image inspection CSIRO. Review of CABB data reduction software
Should CASS consider contributing to CASA development? • No, not at present; review when ASKAP operational • ASKAPSoft imaging algorithm developments will appear in CASA over time • No resources available for further involvement at this stage CSIRO. Review of CABB data reduction software
What data reduction functionality is missing? • Ranked by scientific priority • Priority 1 • Multi-scale clean • Multi Frequency synthesis with non linear terms • UV based Clean, UV modelling • Priority 2 • • Spectral curvature (band pass calibrator) Delay calibration (residual phase slopes across band) Polarization leakage – freq dependence Primary beam variation with frequency • The rest • Image size limits, flagging, peeling, automatic clean boxes, invert weighting errors, polarization imaging/analysis (RM synthesis) CSIRO. Review of CABB data reduction software
How can the missing functionality be provided most easily, given the resources? • Use CASA and ASKAPSoft for the complex problems • MSClean (multi-scale) • available in CASA and ASKAPSoft, including mosaicing, works well • MFS Clean • Miriad approach works well for single fields • CASA – work in progress – wait for next release • ASKAPSoft has MS-MFS Clean – testing in progress • UV based clean • major cycles – subtract from uv data • Provided in CASA and ASKAPSoft, results better than image domain clean. • Wide band primary beam response • Use MFClean for single field • Use A-projection in ASKAPSoft for mosaicing CSIRO. Review of CABB data reduction software
Proposed work CSIRO. Review of CABB data reduction software
Recommendations • Do a number of small improvements to Miriad • A few months worth of development & documentation • Documentation of path to CASA and ASKAPSoft • Data export from miriad, conversion to Measurement. Set • Recipes and scripts for CASA and ASKAPSoft reduction • MS Clean – single field, mosaic (CASA) • MSMFS Clean – single field, mosaic (ASKAPSoft) • RM imaging in CASA CSIRO. Review of CABB data reduction software
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