NASA officials said that countdown clocks at Kennedy Space Center in Florida began counting down from the T-43 hour mark at 3 p.m. EDT today.

The launch team is tracking no issues as technicians continue preparing space shuttle Discovery for liftoff on May 31 at 5:02 p.m. EDT.

There is a possibility for isolated coastal showers on the morning of launch, but the weather forecast is good overall, with an 80% chance of favorable weather at liftoff time.

The seven-member STS-124 crew arrived at Kennedy at about 12:30 p.m. today, touching down at the Shuttle Landing Facility in T-38 jets.

Navy Cmdr. Mark E. Kelly will command the STS-124 shuttle mission. Navy Cmdr. Kenneth T. Ham will serve as the pilot. Mission specialists will include NASA astronauts Karen L. Nyberg; Air Force Col. Ronald J. Garan Jr. and Air Force Reserve Col. Michael E. Fossum. Japan Aerospace Exploration Agency (JAXA) astronaut Akihiko Hoshide also will serve as a mission specialist.

Space shuttle Discovery’s upcoming STS-124 mission is the second of three flights that will launch components to complete the Japan Aerospace Exploration Agency's Kibo laboratory. The shuttle crew will install Kibo’s large Japanese Pressurized Module, or JPM, and its remote manipulator system, or RMS. The RMS consists of two robotic arms that support operations outside of Kibo.

The RMS Main Arm can handle up to 14,000 pounds of hardware and the Small Fine Arm, when attached to the Main Arm, handles more delicate operations. Each arm has six joints that mimic the movements of a human arm. The lab's logistics module, which was installed in a temporary location during STS-123 in March, will be attached to the new lab.

The bus-sized module will be the station’s largest laboratory and will be the second component of Japan's laboratory complex to fly to the station. The first, the Japanese Experiment Logistics Module, was launched in March on shuttle mission STS-123.

The Kibo pressurized module weighs in at 32,000 pounds. It is so large that the shuttle’s Orbiter Boom Sensor System was left at the station during the last mission. There is not room in Discovery's cargo bay for both the boom and the lab.

A third and final shuttle mission to complete the complex will launch an exterior platform for the Kibo laboratory complex that will allow experiments to be exposed to space.

The STS-124 mission carries the heaviest payload to the station and it will include three spacewalks. On flight day 4, Garan and Fossum will transfer the Orbiter Boom Sensor System back to the shuttle from its temporary location of the station’s truss, or backbone. The crew will then prepare the JPM for its removal from the shuttle’s payload bay. Later that day, the JPM will be installed on the port side of Harmony.

Two days after, in the second spacewalk, Garan and Fossum will install covers and external television equipment on the JPM and remove covers on the RMS, which will be deployed on flight day 8. The spacewalkers also will prepare for the flight day 7 relocation of the Japanese logistics module.

During the third and final spacewalk, Garan and Fossum will primarily work to replace a failed nitrogen tank assembly on the station’s truss with a spare that was temporarily stored on one of the station external stowage platforms.

During the spacewalks, the astronauts will wear a new gloves with reinforced patches on the thumb and index finger for the first time.  The patches are made of the same cut-resistant Vectran material already used in the palm of the gloves, but in a much tighter weave.  In this form, the fabric is called  TurtleSkin. 

TurtleSkin patches were sewn onto the gloves below the tip of the thumb and index finger, and an extra strip of the glove’s rubbery outer layer was added over the TurtleSkin to provide grip.Tests have shown that this TurtleSkin weave greatly increases the Vectran’s strength.  It is up to four times more resistant to being damaged than the normal weave.