Complex sentence: Between the 1966 and 1968 the radar was upgraded, increasing the range of the system, later between 1969 and 1970 the radars range was again improved in addition to achieving better reliability.
Split into simpler sentences: Between the 1966 and 1968 the radar was upgraded, increasing the range of the system. Later, between 1969 and 1970, the radars range was again improved in addition to achieving better reliability.