NASA technicians have begun filling the space shuttle Discovery’s enormous external fuel tank in preparation for her final launch later today.

With NASA’s shuttle fleet set to retire next year, today’s launch attempt will be the beginning of the end for Discovery. The shuttle is making its 39th and final spaceflight with this launch, and will be the first of NASA’s remaining three shuttles to be retired.

Discovery will fly an 11-day supply mission to the International Space Station to deliver a humanoid robot helper for the station crew and a new storage room for the orbiting lab.