Canceled Apollo missions planning their own circumlunar flight for December to upstage the Americans once again (see Zond program). McDivitt's crew—who had grown accustomed to working with LM-3 and preparing for its flight—was kept on the D mission which now became Apollo 9, while Borman's crew would fly the CSM lunar orbit mission on Apollo 8, and the E mission was canceled. The swap of crews was also decisive in who would be the first man to walk on the Moon. Pete Conrad was backup Commander for McDivitt's crew, and by the process of crew rotation, would have been in line for Commander
Apollo 15 be selected as a prime or backup crew member for an Apollo flight; from Group 4 he was the only astronaut to make it to the Moon, with the last Apollo mission at the end of 1972. All three members of the support crew were scientist-astronauts, selected in 1967, as the prime crew felt they needed more assistance with the science than with the piloting. None of the support crew would fly during the Apollo Program, waiting until the Space Shuttle program for the chance to go into space. The three Apollo 15 astronauts had served as the backup crew