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In this section, I will discuss the calibration of polarization sensitive VLBI data, both from the MarkIII and VLBA correlators. Throughout, I will only consider processing with the software package of the NRAO. The calibration steps will be demonstrated by data from a cm global MarkIII VLBI experiment (epoch 1992.24, network designation GR2) and from a cm VLBA experiment (epoch 1995.23, designation BA8). The processing path for VLBA and MarkIII correlator output differs only in the reading of data into .
An alternative reduction path is provided by the Brandeis software package, which provides facilities for amplitude calibration, polarization calibration (in the linear approximation, Equations 7), and imaging as well as model fitting routines that allow simultaneous fitting of total intensity and complex polarization. See, for example, [Roberts, Wardle, & Brown (1994)] for a description of the Brandeis software. The package was originally written for data from the MarkIII correlator, but software to convert between FITS format and Brandeis format is currently being developed. The Brandeis software package is maintained by Dr. Denise Gabuzda of the Lebedev Physical Institute who may be contacted at firstname.lastname@example.org.