a possible protruding gap filler, and some external tank foam losses, but there was nothing to indicate any problems. Shannon also noted that a vapor trail was seen coming off the external tank for several seconds during launch, but noted that this was a condition seen during both STS-114, and STS-121, and was found to be condensate coming off the back side of the tank. Due to the temperature and humidity, combined with the angle of the Sun for Discovery's launch, the plume appeared more dramatic in some of the imagery. This was considered an "expected condition", and Shannon confirmed it was of no concern. October 25 (Flight day 3) The crew of STS-120 worked through the rendezvous procedures in the morning leading to the rendezvous pitch maneuver which began at 11:34 UTC. Following the RPM, the crew was given the "Go" to dock with the station, and successful docking to the International Space Station occurred at 12:40 UTC. Following docking, the joint crews conducted a station safety review, and Tani's custom Soyuz seatliner was transferred from Discovery to the Soyuz TMA-11, with Anderson's seat liner taken into Discovery. This marked the official end of Expedition 16 for Anderson, and the start of Tani's increment. Just before the two crews signed off to sleep, they were informed that after preliminary review of the RPM photography, focused inspection of the orbiter's heat shield would not be required. During the MMT briefing, Shannon confirmed that initial evaluation of the available data showed Discovery to be a "pretty clean vehicle". He also confirmed they were not working any issues or items of interest. Shannon said the piece of ice that was looked at prior to launch dislodged during main engine ignition, and as it fell, the ice appeared to graze the underside of the orbiter at the beginning of ascent, but the area around the impact site was in good condition, and the ice did not appear to have caused any damage. Shannon said the teams would continue to evaluate the imagery and data, but the shuttle was in a good configuration. October 26 (Flight day 4) The two crews started the day by preparing for the mission's first spacewalk, which began at 10:02 UTC, and ended at 16:16 UTC. Parazynski and Wheelock successfully completed all EVA activities, including preparing Harmony for removal from the payload bay. Wilson, Tani, and Anderson controlled the