  DiFX is a correlator for VLBI data based on the FX architecture (first
Fourier transform and then cross-multiply). DiFX is a free licensed software
written in C++, developed and maintened by an international group of
programmers. A new DiFX version (dra) has been developed at Max-Planck-Institut
f\"ur Radioastronomie (MPIfR), in order to manage the correlation of a
space-based antenna with ground stations. The dra version is running on the
High Performance Computer cluster (HPC) in Bonn, and it is used for the data
processing of the three AGN imaging RadioAstron Key Science Projects ongoing,
based at the MPIfR.
