 Maiden flight took place on 24 December 1979 successfully placing CAT-1 satellite on the orbit.With the later introduction of Ariane 2 and Ariane 3 it became necessary to improve the performance of the upper stage engine.This was achieved by extending the nozzle length and increasing the chamber pressure from 30 to 35 bar, increasing the engine's specific impulse and resulting in a nominal burn time increase from 570 to 735 seconds.