xv astronauts to be housed on Mir as Russia had done with other countries. The shuttle would help ferry up much-needed supplies in exchange for letting US astronauts gain station living experience. Simply docking the American orbiter to the Mir space station was an engineering and political feat in itself since neither the vehicles nor the programs were designed for such activities. Although automated supply ships, called Progress, serviced Mir, their capacity was nowhere near that of the shuttle. Seven US astronauts stayed aboard Mir from 1995 to 1998 for a combined on-orbit time of more than 30 months. In the second phase, the ISS would be constructed up to a minimal set of components that would make it a self-supporting scientific outpost. To help jump-start the program, the Russians would provide the first two modules that would anchor the station by providing living quarters, power, life support, propulsion (to keep the station from falling back to the Earth), and attitude control (to keep the vehicle in the proper orientation). This phase ended with the addition of the US airlock, which provided redundant extravehicular activity (EVA), or spacewalk, capability. At this point, the ISS would consist of living quarters, docking ports, propulsion and control modules, power-generating solar arrays, and airlocks that allowed for spacewalks that were critical for repair and further assembly. This would be a self-sufficient mini-station. Phase 3 would see the ISS evolve to “core complete.” Although more modules were planned beyond core completion (e.g., the habitation module), this phase represented a truly complete station that would include three science modules: the US laboratory, ESA Columbus astrophysics module, and the Japanese modules with an External Exposure Facility. Initially, the ISS crews consisted of three people. When the advanced US life support system was activated in 2009, the standard crew size increased to six. The ISS will be able to routinely support a crew of seven. It is anticipated the permanent crew will reach this number upon completion of the US Commercial Crew Program. The Program Office, located at Johnson Space Center in Houston, Texas, manages the USOS. Run by the program manager, the Program Office is responsible for all aspects of the program under NASA direction. A number of divisions under the program manager oversee every aspect of the vehicle integration and operations, including engineering support, software development, external integration, planning and safety, and mission assurance. The chief scientist and the ISS Research Integration Office are tasked with maximizing the research, often referred to as utilization, on the space station. Also under the ISS Program Office is Mission Operations Support. This is performed by the Flight Operations Directorate and the flight control team that executes the real-time operation of the vehicle. Note that while each international partner and its FCT is responsible for its systems, NASA is responsible for integration and all safety aspects of the space station. The Space Shuttle was managed out of a separate Space Shuttle Program Office. Getting to Know the International Space Station The fully assembled ISS is shown in Figure 3, with each element indicated. Although there is no true up, down, left, or right in space, a system is required to ensure everyone—crew and ground—are talking consistently. Therefore, as with a seagoing ship, the direction of motion is referred to as forward, which makes the opposite end the aft. In Figure 3, the Pressurized Mating Adapter number 2 (PMA-2) module is at the front of the station and is generally the nose pointing in the direction of flight most of the time. Facing forward (i.e., sitting on PMA-2 and looking forward) means the port side is on the left and starboard is on the right. Unlike a ship on the water, the ISS is exposed to additional directions in space—i.e., up and down. When the ISS is orbiting forward around the Earth, the direction pointing down toward the Earth is called nadir and the direction away is the zenith. More details are provided in Chapter 8. Each module or segment of the ISS has a functional name such as Node 2, Laboratory, S0 truss, or Service Module, for example. The FCT uses these names on all its operations and clearly indicates the function of that element. For example, Node indicates a pressurized module that serves as a hub for other modules to be attached. The Integrated Truss