Endeavour's crew members ate their traditional launch-day meal in Kennedy's Operations and Checkout Building crew quarters. Then, they put on their customized orange spaceflight suits. The suits contain an oxygen supply, communications equipment and a temperature control system that protect the astronauts during liftoff pressure changes and in the unlikely event of an emergency. After they suit up, the astronauts will leave their crew quarters and head toward a vehicle waiting to take them to Launch Pad 39A.

The launch team at NASA's Kennedy Space Center has started filling the external tank with liquid oxygen and liquid hydrogen. The propellants will power Endeavour's three main engines during launch.

The enclosed gantry that protects the shuttle on the launch pad will be retracted to its launch position tonight as the liftoff of Endeavour nears. The Rotating Service Structure, as it is known, will be moved tonight at 11:30. Liftoff remains on schedule for 7:55 p.m. EST Friday. The weather forecast calls for a 70 percent chance of acceptable conditions and the launch team reports no technical issues.

Space shuttle Endeavour, commanded by veteran space flier Navy Capt. Chris Ferguson, 47, is scheduled to arrive at the space station two days later. The shuttle and station crews will collaborate on the delivery of key life support and habitability systems that will enable long‐term, self‐sustaining station operations after the shuttle fleet is retired. The crew will conduct four spacewalks to service and lubricate the complex’s two Solar Alpha Rotary Joints (SARJ) that allow the station’s photovoltaic cells to revolve like paddlewheels and point at the sun. The starboard SARJ has had limited use since September 2007.

The primary goal of the STS-126/ULF2 mission is to provide additional capability for the International Space Station to house astronauts and to increase the station crew size from three to the desired six-crew members by spring 2009. Leonardo, a large cargo container inside Endeavour’s payload bay, will bring supplies and equipment to the International Space Station to help prepare the outpost for a six member crew. The supplies include replacement Trundle Bearing Assemblies (TBAs) for the station’s ailing Starboard Solar Alpha Rotary Joint (SARJ). In all, more than 1,000 items will be delivered in the Multi‐Purpose Logistics Module (MPLM). Leonardo is one of three differently named large, reusable pressurized MPLMs used to ferry cargo back and forth to the station. Including STS-126, the MPLMs have flown eight times since 2001. Leonardo was the first MPLM to deliver supplies to the station and STS-126 is its fifth flight. The cylindrical modules include components that provide life support, fire detection and suppression, electrical distribution and computers when attached to the station.

The Italian-built, U.S.-owned logistics modules are capable of carrying more than 7.5 tons (15,000 pounds) of cargo, spares and supplies, the equivalent of a semi-truck trailer. The modules bring equipment to and from the space station, such as container racks with science equipment, science experiments from NASA and its international partners, spare parts, and other hardware items for return, such as completed experiments, system racks, space station hardware that needs repair and refuse. Some of the items are intended for disposal on Earth, while others are for analysis and data collection by hardware providers and scientists.

In addition to Leonardo, Endeavour will carry the Lightweight Multi-Purpose Experiment Support Structure Carrier and a spare Flex Hose Rotary Coupler Unit (FHRC) for a future replacement spare. The shuttle will return a depleted Nitrogen Tank Assembly (NTA), which will be refilled and sent back to the station in 2010. The FHRC provides two isolated paths for distribution of ammonia between the space station radiators and the rest of the staton. The NTA provides a high-pressure gaseous nitrogen supply to control the flow of ammonia out of the Ammonia Tank Assembly (ATA). Carrying 16 system and cargo racks, Leonardo will fly with modifications that will allow 12 additional cargo bags the size of carry-on suitcases to be flown inside the module’s rear end cone.

Leonardo will carry two crew quarters racks that will be installed inside the Harmony node, an advanced Resistive Exercise Device, designated aRED, two Water Reclamation Racks that will recycle urine into potable water, a Combustion Integration Rack that will analyze the physics of combustible gases, a Waste and Hygiene Compartment (WHC) rack including a toilet, a galley that will be located in the U.S. Destiny laboratory, three Zero-Gravity storage racks for stowage of large quantities of hardware, four handrail extender assemblies to increase crew members’ mobility as they float about the station, an antimicrobial applicator to remove bacteria from cooling and fluid lines, and two additional foot restraints to elevate shorter crew members.

Also included in Leonardo is the General Laboratory Active Cryogenic ISS Experiment Refrigerator, or GLACIER, a double locker cryogenic freezer for transporting and preserving science experiments that will remain in orbit at the end of the mission. The freezer provides thermal control between +4° Celsius and ‐160° Celsius and can operate in both the space shuttle’s middeck and the EXPRESS Rack in orbit. The EXPRESS Rack system supports science payloads in several disciplines, such as biology, chemistry, physics, ecology and medicine, including commercial activities.

In the active mode, GLACIER can be transported in the mid-deck, but for passive transport, it is flown in the logistics module. Additionally, an incubator/refrigerator, the Microgravity Experiment Research Locker Incubator, or MERLIN, will fly in the MPLM. Though originally used for thermal control of scientific experiments, it will remain on the outpost and be used to store drinking beverages and food for a six‐member station crew.

Leonardo is named after the Italian inventor and scientist Leonardo da Vinci. The two other modules are named Raffaello, after master painter and architect Raffaello Sanzio, and Donatello, for one of the founders of modern sculpture, Donato di Niccolo Di Betto Bardi. Raffaello has flown three times.

Leonardo has flown the most because it is equipped with programmable heater thermostats on the outside of the module that allow for more mission flexibility. There are only two more MPLM flights scheduled before the station is complete and the space shuttle retires in 2010.