After Armstrong served as backup commander for Apollo8, Slayton offered him the post of commander of Apollo 11 on December 23, 1968, as Apollo8 orbited the Moon. According to Armstrong's 2005 biography, Slayton told him that although the planned crew was Commander Armstrong, Lunar Module Pilot Buzz Aldrin, and Command Module Pilot Michael Collins, he was offering Armstrong the chance to replace Aldrin with Jim Lovell. After thinking it over for a day, Armstrong told Slayton he would stick with Aldrin, as he had no difficulty working with him and thought Lovell deserved his own command. Replacing Aldrin with Lovell would have made Lovell the lunar module pilot, unofficially the lowest ranked member, and Armstrong could not justify placing Lovell, the commander of Gemini 12, in the number3 position of the crew. The crew of Apollo 11 was officially announced on January 9, 1969, as Armstrong, Collins, and Aldrin, with Lovell, Anders, and Fred Haise as the backup crew.