The program getorb for automatic retrieval of the Delft precise orbits for ERS1/2. See our web pages for a link.
The package gv (recommended) or ghostview to view postscript files,
generated by plotcpm and plotoffsets, and cpx2ps.
The GMT (generic mapping tools). Highly recommended. We generally generate postscripts for visualizing the phase and amplitude with this program. See also cpxfiddle and cpx2ps.