In addition to the Expedition Five crew, the Leonardo Multi-Purpose Logistics Module (MPLM) was brought to the station in Endeavour's payload bay. This was the fifth flight of the Leonardo MPLM. Leonardo was lifted out of the payload bay and attached directly to the station's Unity node for the unloading of its cargo. The MPLM brought eight resupply stowage racks, five resupply stowage platforms, two international standard payload racks and two scientific racks for the U.S. laboratory Destiny, EXPRESS (for Expedite the Processing of Experiments to the Space Station) Rack No. 3, and the Microgravity Glovebox. EXPRESS Rack 3 houses experiments and provides them with power, fluids, cooling, data, and other basic utilities, thus increasing the science capability of the station. The Microgravity Glovebox provides a facility that safely contains fluids, flames, particles, and fumes while performing experiments. The MPLM was replaced in the cargo bay and returned to Earth for refurbishment and reuse on a subsequent mission.
Upon docking with the station and opening of the hatches, a welcoming ceremony and safety briefing were held for the new arrivals. While docked to the space station, the STS-111 crewmembers, Chang-Diaz and Perin, performed three spacewalks continuing on-orbit construction of the ISS and maintenance work. All three spacewalks were conducted from the station’s Quest Airlock.
The first spacewalk was performed to install the P6 Truss Power and Data Grapple Fixture, which allows Canadarm2, the ISS robotic arm, to grip the P6 truss for future station assembly operations. During the first spacewalk, the crew also installed meteoroid-debris shields on the Pressurized Mating Adapter 1 (PMA 1), removed the ISS Mobile Remote Servicer Base System (MBS) thermal blankets, and unberthed the MBS from the payload bay. During the second spacewalk, the astronauts connected the MBS utilities, secured the MBS to the Mobile Transporter, deployed the MBS Payload Orbital Replacement Unit Accommodation (POA), and relocated the camera. The wrist joint of Canadarm2 was replaced during the third and final spacewalk of the STS-111 mission.
Several Detailed Supplementary Objectives (DSOs) were also performed during the STS-111 mission. A DSO is a NASA-sponsored investigation performed by Space Shuttle crewmembers, who serve as the test subjects. These studies are designed to require minimal crew time, power and stowage. Biomedical DSOs focus on operational concerns, including space motion sickness, cardiovascular deconditioning, muscle loss, changes in coordination and balance strategies, radiation exposure, pharmacokinetics and changes in the body's biochemistry.
Development Test Objectives (DTOs) performed during this mission were Single-String Global Positioning System, Crosswind Landing Performance, and Biotechnology Water Treatment System. A DTO is a NASA-sponsored investigation that is performed by Space Shuttle crewmembers to evaluate new hardware and procedures involving the Orbiter, its subsystems, and its support equipment.
One Department of Defense experiment called Ram Burn Observations (RAMBO) was also flown. RAMBO is an experiment in which the Shuttle Orbital Maneuvering System engine burns are observed for the purpose of improving plume models.
When STS-111 landed, it marked the end of a record-setting flight by the Expedition Four crew, Commander Yury Onufrienko, and Flight Engineers Carl Walz and Daniel Bursch. The Expedition Four crew spent 196 days in space, which gave Walz and Bursch the U.S. space flight endurance record. After weather delayed landing, Endeavour's crew glided to a smooth landing at Edwards Air Force Base in California on June 19, 2002, at 1:58 p.m. EDT.