The primary data reduction package for the VLA is the CASA (Common Astronomy Software Applications) package, which is also used for ALMA. See http://casa.nrao.edu for more information on the latest release.
It is possible to reduce VLA data taken in all correlator modes that are offered for general observing using CASA. More complex correlator set-ups are generally better handled by CASA, and advanced imaging algorithms are available in CASA. The VLA calibration pipeline uses CASA.
The Astronomical Image Processing System (AIPS) can reduce all observations made with simple correlator set-ups (e.g., identical spw bandwidths and channel widths throughout). AIPS is currently required for the reduction and analysis of phased-array VLA observations for VLBI and low-band observations (P-band, 230-470 MHz). NRAO will continue to support AIPS for the foreseeable future, at least until VLBI functionality and the full data path for frequencies below 500 MHz have been incorporated into CASA. See http://www.aips.nrao.edu for more details.
The following pages are designed to help VLA observers understand, and process, their data. Note that these pages are a work in progress and many are placeholders for future content. For instructions on obtaining VLA data, see the archive web page. If you are new to radio astronomy (and interferometry in general), you might consider reading Chapter 7 of Astronomy Methods (Bradt, 2004) as well as the first several lectures in Synthesis Imaging in Radio Astronomy II (ASP Conference Series Vol. 180). You may also find useful information in the lectures from the 13th Synthesis Imaging Workshop.
|These CASA Guides wiki pages contain instructions for loading and inspecting VLA data, as well as a discussion of the Measurement Set contents and structure.|
|The two main analysis packages used for the processing of VLA data are AIPS and CASA.|
|The VLA calibration pipeline performs basic flagging and calibration using CASA. Starting with the D-configuration, Semester 2013A, it will be run automatically at the completion of all astronomical scheduling blocks (SBs).|
|Describes acceptable use of NRAO computing facilities for the purpose of calibration and imaging EVLA and VLBA observations at the New Mexico Array Science Center (NMASC).|
|Since the VLA has added two new bands and much wider bandwidths, we will be making new models for Ka and S bands but also offering more models at traditional VLA bands so that the model closest to the frequency of observation can be used. Currently we have models for Ka band B array models at four frequencies. Choose the one closest to your observing frequency.|
|NRAO monitors the positions of the VLA antennas on a regular basis -- roughly monthly, and more often during reconfigurations. This involves observing a number of calibrators spread around the sky, solving for the antenna-based gains, and from their behavior deriving the three-dimensional positions of those antennas (see, e.g., chapter 12 of Thompsan, Moran, and Swenson 1991, Interferometry and Synthesis in Radio Astronomy, for a fuller discussion). These corrections (generally less than a centimeter) are then inserted into the correlator model in the on-line system.|