pbr Discovery's astronauts have taken one final spacewalk outside the International Space Station before the shuttle goes into retirement.br ppbr Spacewalkers Alvin Drew and Stephen Bowen have been doing relatively minor jobs that will leave the orbiting lab in the best possible condition, once the space shuttles stops flying.br ppbr Drew and his colleague Stephen Bowen whittled down the entire to-do list, including installing a rail car light and an outdoor robot's camera.br ppbr Discovery will remain at the space station until Sunday.br ppbr The shuttle astronauts are staying an extra day to help fit the new storage room.br ppbr There is a possibility that yet another bonus day might be added, which would stretch the mission to 13 days.