Complex sentence: Barbara Morgan, McAuliffe's backup, became a professional astronaut in January 1998 and flew on space shuttle mission STS-118, to the International Space Station, on August 8,2007, aboard "Endeavour", the orbiter that replaced "Challenger".
Split into simpler sentences: Barbara Morgan, McAuliffe's backup, became a professional astronaut in January 1998. Morgan flew on space shuttle mission STS-118, to the International Space Station, on August 8,2007, aboard "Endeavour", the orbiter that replaced "Challenger".