(05/17/2002) -- The STS-111 crew and Expedition 5 walk eagerly to the Astrovan that will take them to Launch Pad 39A for a simulated countdown. From left are Mission Specialists Philippe Perrin and Franklin Chang-Diaz; the Expedition 5 crew, Sergei Treschev, Peggy Whitson and Valeri Korzun; Pilot Paul Lockhart; and Commander Kenneth Cockrell. The simulation is part of STS-111 Terminal Countdown Demonstration Test activities for the crew and Expedition 5. The payload on the mission to the International Space Station includes the Mobile Base System (MBS), an Orbital Replacement Unit and Multi-Purpose Logistics Module Leonardo. The MBS will be installed on the Mobile Transporter to complete the Canadian Mobile Servicing System, or MSS, enabling Canadarm 2 to 'inchworm' from the U.S. Lab Destiny to the MSS and travel along the truss to work sites. The Expedition 5 crew is traveling on Endeavour to replace the Expedition 4 crew on the Station. Launch of Endeavour is scheduled for May 30, 2002