Mir EO-2 (also called Mir Principal Expedition 2) was the second long duration expedition to the Soviet space station Mir, and it lasted from February to December 1987. The mission was divided into two parts (sometimes called (a) and (b)), the division occurring when one of the two crew members, Aleksandr Laveykin, was replaced part way through the mission by Aleksandr Aleksandrov. Laveykin was replaced because ground-based doctors had diagnosed him with minor heart problems.