The STS-104 crew performed 3 spacewalks. The first spacewalk occurred on 15 July, and focused on installation of the Quest Joint Airlock. The spacewalkers helped as Susan Helms, using the station's robotic arm, lifted the new station airlock from Atlantis' payload bay and moved it to the station's Unity module. During much of the 5 hour, 59 minute spacewalk, Jim Reilly worked from a foot platform attached to the end of the shuttle's robotic arm, operated by Janet Kavandi. After the spacewalk, crew members inside the Station attached connections to the airlock to prevent thermal damage. The second spacewalk which happened on 18 July, lasted 6 hours, 29 minutes. The internal hatches between the shuttle and station were closed at the end of Flight Day 6 so Atlantis' cabin pressure could be lowered in preparation for the second spacewalk. The major objective was to attach and connect an oxygen and a nitrogen tank. Susan Helms operated the station arm to lift the tanks from the shuttle's payload bay and maneuver them to the new airlock. At the airlock, Mike Gernhardt and Jim Reilly latched the tanks in place and connected cables and hoses. The spacewalkers were able to get ahead of schedule and also install another oxygen tank, leaving only one tank to be connected on the third spacewalk. The third spacewalk, which occurred on 21 July, was the first spacewalk based out of the new Quest Joint Airlock, and lasted 4 hours, 2 minutes. Primary objective was to install the final nitrogen tank outside the airlock. This spacewalk tested a new protocol developed by former commercial diver Mike Gernhardt: essentially exercising while breathing oxygen to purge nitrogen from the spacewalkers' bodies. In August, Space Shuttle "Discovery" returned to the station during the mission STS-105, which carried the three Expedition 2 crew members back down to Earth. They undocked from the station on 20 August 2001, marking the end of the Expedition 2 increment. The International Space Station Expedition Two patch depicts the Space Station as it appeared during the time the second crew was on board. The Station flying over the Earth represents the overall reason for having a space station: to benefit the world through scientific research and international cooperation in space. The number 2 is for the second expedition and is enclosed in the Cyrillic MKS and Latin ISS which are the respective Russian and English abbreviations for the International Space Station.