Post-Processing Software

AIPS

AIPS, NRAO's Astronomical Image Processing System, is a set of programs for the analysis of continuum and line observations, and is widely used with VLBA and VLBI data.  These programs are available for a wide range of computer operating systems, including various flavors of Linux and the Mac-OS/X operating system.   Extensive online internal documentation can be accessed within AIPS.  An entire chapter in the AIPS Cookbook (NRAO staff, 2007) provides useful "how-to" guidance those reducing VLBI data, including discussion of VLBA calibration transfer, space VLBI, polarimetry, and phase referencing.   Appendix C of the AIPS Cookbook provides a step-by-step guide to calibrating many types of VLBA data sets in AIPS, employing simple VLBA utilities, including calibration modifications for VLBA+VLA datasets.

A new ''frozen" version of AIPS is produced each year, and a newer version is updated and made available throughout the calendar year. Observers are encouraged to use a very recent version of AIPS, in order to keep up with ongoing  developments in VLBA instrumentation.

AIPS home page: http://aips.nrao.edu.

CASA

CASA (Common Astronomy Software Applications) is the new data reduction package that will be used for the EVLA and ALMA. It does not yet offer an end-to-end reduction path for VLBA data.  However, CASA does contain imaging and calibration tools that may be of use for VLBI data.

CASA home page: http://casa.nrao.edu.

Difmap

Difmap (Shepherd 1997) provides editing, imaging, self-calibration, and pipelining capabilities in an interactive package.  It was developed as part of the Caltech VLBI Analysis Programs and remains widely used, although development has been frozen and continued support is limited primarily to assistance in installation.

Difmap download site: ftp://ftp.astro.caltech.edu/pub/difmap/difmap.html.  Contact: M.C. Shepherd, mcs@astro.caltech.edu.

Connect with NRAO

The National Radio Astronomy Observatory and Green Bank Observatory are facilities of the U.S. National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Founded in 1956, the NRAO provides state-of-the-art radio telescope facilities for use by the international scientific community. NRAO telescopes are open to all astronomers regardless of institutional or national affiliation. Observing time on NRAO telescopes is available on a competitive basis to qualified scientists after evaluation of research proposals on the basis of scientific merit, the capability of the instruments to do the work, and the availability of the telescope during the requested time. NRAO also provides both formal and informal programs in education and public outreach for teachers, students, the general public, and the media.

The National Science Foundation (NSF) is an independent federal agency created by Congress in 1950 "to promote the progress of science; to advance the national health, prosperity, and welfare; to secure the national defense..."

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