6 p.m. CDT Thursday, April 15, 2010
Mission Control Center, Houston, Texas
STS-131 MCC Status Report #22
HOUSTON – After dealing with a balky set of bolt controllers, the combined crew of space shuttle Discovery and the International Space Station removed the Leonardo Multi-Purpose Logistics Module from its station port today.

The crew closed Leonardo’s hatch at 2:38 a.m. CDT, but put the removal on hold when Mission Control saw unusual readings on the Control Panel Assemblies that operate the 16 remote-control bolts used to secure the pressurized cargo carrier to the Harmony module port.

The crew disconnected and reconnected all 36 of the connectors that provide power and data to the controllers, and in the process found a small pin that had been broken. They secured the pin, which was not part of the electrical connections, with Kapton tape to ensure it did not interfere with the bolts’ operation. Mission Control conducted additional troubleshooting, and the bolts were released at 3:19 p.m.

Leonardo, making is final round-trip to the station before becoming a Permanent Multi-Purpose Module for the station later this year, was unberthed at 3:24 p.m., about seven hours later than planned. The crew then used the station’s robotic arm to maneuver the module into position above Discovery’s payload bay. Leonardo will remain in this “low hover” position overnight, and the crew will spend about an hour and a half finishing the job of using Canadarm2 to latch it in the shuttle’s cargo bay on Friday.

Space station and space shuttle mission managers reaffirmed plans made overnight to forego a fourth spacewalk to replace the nitrogen tank assembly that has a jammed valve. Engineers have decided the station can operate for an extended period in the current configuration. The team continues to troubleshoot the jammed valve and to consider options for future replacement of the nitrogen tank assembly. The tank assembly is used to pressurize and adjust for the expansion and contraction of the ammonia that circulates through radiators to shed excess heat generated by the station’s electronic systems.

The delay in removing Leonardo resulted in a later-than-planned bedtime for the crew, which will be allowed to sleep in for about an hour later until 12:21 a.m. Friday. The next shuttle status report will be issued after the crew is awakened, or earlier if events warrant.

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