The members of the prime crew of the Apollo 13 lunar landing mission (left to right) are astronauts James A. Lovell Jr., commander; Thomas K. Mattingly II, command module pilot; and Fred W. Haise Jr., lunar module pilot. They pose in front of the launching pad at the Kennedy Space Center. This original prime crew never flew together because astronaut Ken Mattingly, until a few days before the mission, was the prime Command Module Pilot for the mission but due to exposure to measles, was replaced by Jack Swigert. That was fortunate for Mattingly as the newly formed Apollo 13 crew were about to experience the most perilous journey in space.