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Bill Parsons (foreground), manager of the Space Shuttle Program, supports an External Tank (ET) tanking test at Launch Pad 39B from the Launch Control Center. The tanking test is designed to evaluate how the tank, orbiter, solid rocket boosters and ground systems perform under "cryo-load," when the tank is filled with the two ultra-low-temperature propellants. The tank filling and draining portion of the test takes about 11 hours. The test also includes a simulated countdown through the hold at T-31 seconds. The test is being conducted to troubleshoot two issues identified by a tanking test held on April 14. Data is being collected to analyze the liquid hydrogen sensors that gave intermittent readings and the liquid hydrogen pressurization relief valve that cycled more times than standard. The tanking tests are part of preparations for Space Shuttle Discovery's Return to Flight mission, STS-114, to the International Space Station. The launch window extends from July 13 through July 31.