 Upon reaching apogee in the transfer orbit, the first stage and interstage structure were jettisoned.The second stage then fired to circularize the orbit, after which it released the satellite and, using its attitude control jets, began a retrograde maneuver to enter a lower orbit to avoid any possibility of collision with its payload.In addition to the Communication and Reconnaissance missions described above, which placed the payload into stationary (24-hour) orbit, the IUS was also used to boost spacecraft towards planetary trajectories.