CASA on the fringe: VLBI data processing in the CASA software package

In recent years new functionality for VLBI data processing has been added to the CASA package. This paper presents the new CASA tasks 'fringefit' and 'accor', which are closely matched to their AIPS counterparts FRING and ACCOR. Several CASA tasks received upgrades to handle VLBI specific metadata. With the current CASA release VLBI data processing is possible, and functionality will be expanded in the upcoming release. Longer term developments include fringe fitting of broad, non-continuous frequency bands and dispersive delays, which will ensure that the number of use cases for VLBI calibration will increase in future CASA releases.