The offset between the center of mass and the RRA optical center is X = 0.236 m, Y = 0.598 m, Z = 0.683 m in spacecraft axes. The reference system is the same as for TOPEX, with Z pointing towards the Earth. An additional 49 mm correction, to be subtracted from the computed range, is required to account for the RRA phase center offset.

Other CoM references:

Jason Postlaunch Satellite Characteristics for POD activities
Jason-1 center-of-mass information since launch (IDS): ftp://ftp.cls.fr/pub/ids/satellites/macromodels/ja1mod.pdf
Jason-1 nominal attitude law (IDS): ftp://ftp.cls.fr/pub/ids/satellites/ja1att.txt
Jason-1 mass history (IDS): ftp://ftp.cls.fr/pub/ids/satellites/ja1mass.txt
Jason-1 maneuver history (IDS): ftp://ftp.cls.fr/pub/ids/satellites/ja1man.txt