of Space Shuttle Endeavour on STS-89. The mission delivered cosmonaut Salizhan Sharipov to Mir and replaced David Wolf with Andy Thomas, following Wolf's 119-day Increment. During his Increment, the last of the program, Thomas worked on 27 science investigations into areas of advanced technology, Earth sciences, human life sciences, microgravity research, and ISS risk mitigation. His stay on Mir, considered the smoothest of the entire Phase One program, featured weekly "Letters from the Outpost" from Thomas and passed two milestones for length of spaceflight—815 consecutive days in space by American astronauts since the launch of Shannon Lucid on the STS-76 mission in March 1996, and 907 days of Mir occupancy by American astronauts dating back to Norman Thagard's trip to Mir in March 1995. Thomas returned to Earth on the final Shuttle–Mir mission, STS-91. The mission closed out Phase One, with the EO-25 and STS-91 crews transferring water to Mir and exchanging almost of cargo experiments and supplies between the two spacecraft. Long-term American experiments that had been on board Mir were also moved into Discovery. Hatches were closed for undocking at 9:07 a.m. Eastern Daylight Time (EDT) on June 8 and the spacecraft separated at 12:01 p.m. EDT that day. Phases Two and Three: ISS (1998–present) With the landing of Discovery on June 12, 1998, the Phase One program concluded. Techniques and equipment developed during the program assisted the development of Phase Two: initial assembly of the International Space Station (ISS). The arrival of the Destiny Laboratory Module in 2001 marked the end of Phase Two and the start of Phase Three, the final outfitting of the station, completed in 2012. In 2015, a reconfiguration of the American segment was completed to allow its docking ports to accommodate NASA-sponsored commercial crew vehicles, that were expected to start visiting the ISS in 2018. , the ISS has a pressurized volume of , and its pressurized modules total in length, plus a large truss structure that spans , making it the largest spacecraft ever assembled. The completed station consists of five laboratories and is able to support six crew members. With over of habitable volume and a mass of the completed station is almost twice the size of the combined Shuttle–Mir spacecraft. Phases Two and Three are intended to continue both international cooperation in space and zero-gravity scientific research, particularly regarding long-duration spaceflight. By spring 2015, Roscosmos, NASA, and the Canadian