Shuttle Set To Undock, Soyuz To Arrive
Frank Morring, Jr./Johnson Space Center morring@aviationweek.com 
More mission coverage cam be followed at the On Space blog
The combined crews of the space shuttle Discovery and the International Space Station will say their farewells and close the hatches Wednesday as the STS-119/15A ISS assembly draws to a close.
After an off-duty day Tuesday highlighted by a call from President Barack Obama, the crews were set to go to sleep early in preparation for what promises to be an unusually busy undocking day.
Although the normal practice has been to close the hatches between the two spacecraft the day before undocking, mission managers have delayed the hatch closing until Wednesday at 10:53 a.m. EDT to give about five months worth of scientific samples on the station as much time as possible in its freezer.
Once the blood, urine, saliva and other life-science samples are out of cold storage, the Discovery crew will have about 125 hours to get them on the ground before their scientific value is lost. The samples will ride in the shuttle freezer and in double cold bags packed in middeck lockers, and will have first priority for unpacking when Discovery touches down as early as March 28, according to Kwatsi Alabaruho, lead ISS flight director for the mission (Aerospace DAILY, March 23).
Delaying the hatch closing in turn delays undocking by four orbits - about six hours - to give the two crews extra time to make the last-minute transfers, close the hatches, depressurize the docking compartments and check them for leaks.
Once that is done, Discovery pilot Tony Antonelli is scheduled to back the orbiter away from its common berthing mechanism at the front of the station's Harmony node at 3:53 p.m. EDT. He'll fly the standard 360-degree circuit up, over and under the station at a range of 400 to 600 feet to give shuttle crewmates time to document the station's condition, and then will fire a separation burn to drop into a lower orbit for landing preparations.
On the station, crewmates Mike Fincke, Yuri Lonchakov and Koichi Wakata will have a day off, and then Fincke and Lonchakov will start packing for their return to Earth on Soyuz TMA-13/17S April 7.
The replacement Soyuz, designated TMA-14/18S, is scheduled to launch to the station on March 27 at 7:49 a.m. EDT, to deliver Expedition 19 Commander Gennady Padalka and flight engineer Michael Barratt, along with space tourist Charles Simonyi, who will return with Ficke and Lochakov.
The full text of this story appeared in the Aviation Week Intelligence Network
Photo credit: NASA
