The STS-135 payload canister's move to Launch Pad 39A at NASA's Kennedy Space Center in Florida is expected to begin at 9 p.m. EDT tonight with the canister's lift up the pad structure set for early Friday morning.
On Saturday, technicians will follow up on yesterday's tanking test for Atlantis by taking high-tech X-ray scans of the external fuel tank's support beams, called stringers, on the shuttle-facing side of the tank. Earlier this year, teams made the same stringer reinforcement modifications to Atlantis' tank as they had to Discovery's after small cracks in the support beams were discovered prior to the STS-133 mission. Managers ordered the work since Atlantis' tank is similar to the one used for STS-133. Yesterday's tanking test was conducted to help verify there are no issues with the reinforced tank.
During the tanking test, the main fuel valve for Atlantis' No. 3 space shuttle main engine recorded temperatures below normal levels, indicating a possible liquid hydrogen leak. Teams isolated the engine and continued to fuel Atlantis with no issues and temperatures returned to normal readings. Technicians can gain access to the engine area once it is cleared from tanking test operations, and engineers will evaluate any necessary work on the fuel valve. If the valve needs to be replaced, managers expect that the work could be done early next week at the pad and still support Atlantis' July 8 target launch date.