In this paper we have shown that:
1) the total intensity data acquired with the European VLBI telescopes are affected by a systematic error.
2)The physical origin of this error can be traced in the instrumental polarization
3)The effect of the instrumental polarization on the data can be modeled and therefore removed
4)the existing VLBI software must be changed to apply this correction.
© European Southern Observatory (ESO) 1997
Online publication: July 8, 1998