Mission STS-121 took place from July 4 to 17, 2006. During these 13 days in space, the crew of Space Shuttle Discovery continued to test new equipment and procedures that increase the safety of space shuttles. Canada played a critical role in this mission by providing an extension to the Canadarm tipped with a Laser Camera System that allow the inspection of every inch of the spacecraft for possible signs of damage.
Artist's rendering of the new Inspection Boom attached to the end of Canadarm. (Photo: MDA)
This flight to the International Space Station also delivered critical supplies and cargo to the complex for repair and future expansion of the outpost.
STS-121 Mission Overview
The crew of Space Shuttle Discovery continued to test new equipment and procedures that increased the safety of space shuttles during mission STS-121. The flight to the International Space Station also delivered critical supplies and cargo to the complex for repair and future expansion of the outpost.
The focus of the mission was to continue the analysis of safety improvements that began on the first Return to Flight mission STS-114, and to build upon those tests. It continued the testing of the external tank design and processes that minimize potentially damaging debris during launch, ground and flight camera systems to observe the shuttle environment during launch and on orbit. And testing was carried on with techniques for in-flight inspection and repair of the shuttle's Thermal Protection System, or heat shield.
The seven STS-121 astronauts take a break from training to pose for the crew portrait. From the left are astronauts Stephanie Wilson, Michael Fossum, both mission specialists; Steven Lindsey, commander; Piers Sellers, mission specialist; Mark Kelly, pilot; European Space Agency astronaut Thomas Reiter of Germany; and Lisa Nowak, both mission specialists. (Photo: NASA)
Three spacewalks took place. They were devoted to maintenance of the space station and additional testing of heat shield inspection and repair materials, tools and techniques. During the flight, mission managers expected to evaluate the high probability of shuttle supplies supporting an extra day for the mission. The third spacewalk focused on reinforced carbon-carbon inspection and repair.
Discovery remained docked to the International Space Station for most of the mission. In the space station assembly sequence, STS-121 was Utilization and Logistics Flight-1.1 (ULF-1.1). The mission was added to complete Return to Flight on-orbit testing before resuming major assembly of the space station. The mission station objectives were maintenance work and the delivery of equipment, supplies, experiments and spare parts in support of operations and future station assembly missions.
Discovery delivered a third crewmember to live aboard the station. It was the first time a long-duration, three-person crew resided on station since the Expedition 6 crew returned to Earth May 4, 2003, in Kazakhstan. Without the space shuttle to ferry equipment to the station after the Columbia accident, only two people could be supported onboard until the necessary provisions were in place.
The mission's top priority was to inspect all of the reinforced carbon-carbon heat protection material on Discovery's leading edge wing panels and to downlink the data for evaluation to the ground. Second priority was inspecting all the shuttle's silicon-based tiles. The on-orbit inspections were carried out using several methods, including umbilical well and hand-held photography and video of the external tank after it was jettisoned.
En route to the station, the day after launch, the crew used the Canadian-made 15-metre Orbiter Boom Sensor System (OBSS) tipped with two types of lasers and a high-resolution television camera to inspect key areas of the wings for any sign of damage that may have occurred during launch. This boom nearly doubles the length of the robotic capability of the shuttle crane. There were additional inspections using this equipment scheduled the day before and the day of undocking from the space station.
An inspection conducted by the station crew focused on the underside of Discovery at a distance of 183 metres before docking. The shuttle was carefully rotated under command of Lindsey through a back flip allowing the station crew to train cameras on the shuttle as it approached. This rendezvous pitch manoeuvre (RPM), was first performed during the STS-114 mission.
Two six-and-a-half hour spacewalks were scheduled on the fifth and seventh days of the mission. A third spacewalk was scheduled on the ninth day. For the first spacewalk, the crew used the orbiter boom as a work platform for hard-to-reach repair sites on the bottom of the shuttle. They also began maintenance of the station's mobile transporter by safing or replacing a cable cutter on one side of the unit to allow the robotic system to be translated in support of the second spacewalk.
During the second spacewalk, on the other side of the mobile transporter, the crew replaced a reel assembly and the detached cable that was inadvertently cut and swap out the cable cutter with a disabled unit. The crew also installed a spare pump for the thermal control system on the outside of the station's Quest airlock for future use. The replacement cable reel and pump module were delivered on a carrier in Discovery's cargo bay.
Space Shuttle Discovery on Launch Pad 39B at the Kennedy Space Center.
(Photo: NASA/ Ken Thornsley)
The STS-121 launch window was July 1 to 19. Discovery launched on July 4, 2006 from Launch Pad 39B at Kennedy Space Center, Florida, and rendezvoused with the International Space Station on flight day 3. Undocking was set for flight day 11. Discovery's crew made final preparations for the return home on flight day 12, with landing at the Kennedy Space Center's Shuttle Landing Facility on flight day 13.
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