Post-Processing Software

by Gustaaf Van Moorsel last modified Jun 05, 2013


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 supported on a variety of computer operating systems, including Linux and Mac-OS/X.   The AIPS Cookbook (NRAO staff, 2007) includes an entire chapter on reducing VLBI data, including discussion of VLBA calibration, space VLBI, polarimetry, and phase referencing; Appendix C provides a step-by-step guide to calibrating many types of VLBA data in AIPS, including 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:

CASA: Common Astronomy Software Applications is the new data reduction package 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:

Difmap: Difmap (Shepherd 1997), developed as part of the Caltech VLBI Analysis Programs. provides editing, imaging, self-calibration, and pipelining capabilities in an interactive package.  Development has been frozen, and continued support is limited primarily to assistance in installation.  Difmap download site:  Contact: M.C. Shepherd,