11:30 p.m. CDT Wednesday, April 14, 2010
Mission Control Center, Houston, Texas
STS-131 MCC Status Report #21
HOUSTON – Space shuttle Discovery’s seven-member crew will begin its day by unloading the last transfer items in the Leonardo Multi-Purpose Logistics Module and then closing the hatches between it and the Harmony node in preparation for its return to the shuttle’s payload bay.

At 11:21 p.m. CDT Mission Control awakened the crew with the song “The Earth in the Color of Lapis Lazuli” by Seiko Matsuda for Naoko Yamazaki, who served as the loadmaster, supervising the unloading and loading activities for this mission.

Overnight International Space Station and Space Shuttle mission managers agreed there is no need for a fourth spacewalk to replace the nitrogen tank assembly that has a jammed valve. Station ground teams have determined the station can operate for an extended period of time in the current configuration. The team is continuing to troubleshoot the stuck valve and is looking at options for future replacement of the nitrogen tank assembly should that be necessary.

The stuck valve is in a nitrogen tank assembly needed to pressurize a new ammonia tank installed on the station during this mission’s three spacewalks. It keeps ammonia circulating through radiators that dissipate the heat generated by the station’s electronic systems.

Ground teams were concerned a high beta angle would cause the ammonia in the new tank assembly to expand and exceed the capacity of the radiators without the nitrogen to keep the system circulating. The beta angle – the angle between the sun and the plane of the orbit – is increasing, creating higher temperatures.

At 7:41 a.m., Yamazaki and Mission Specialist Stephanie Wilson will use the station’s robotic arm to move Leonardo back into the shuttle’s cargo bay. This is the seventh time Leonardo has carried supplies and equipment to the station. The next time it returns with the STS-133 crew in September it will remain berthed to the station.

The crew is scheduled for sleep at 3:21 p.m. The next shuttle status report will be issued after the crew’s work day ends, or earlier if events warrant.

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