Delta 0300 was a two-stage numbered Delta configuration with a long-tank Thor-derived liquid first stage augmented by three Castor II solid motors, the higher-energy Delta second stage, and Delta Inertial Guidance System. Three vehicles flew polar meteorological missions from October 1972 through November 1973. NOAA 2 and NOAA 3 reached orbit; the ITOS-E launch failed after a second-stage hydraulic malfunction caused loss of control.