The celestial timebase reference system was a navigational system. This system was found aboard Galaxy-class starships. In 2368, after the computer systems of the USS Enterprise-D were disrupted by a energy wave from a Satarran starship, Geordi La Forge accessed the basic system directories of the Engineering Department. According to the department, the celestial timebase reference system was off-line. (TNG: "Conundrum" )