Discovery Will Clean Out ISS Sample Storage
Frank Morring, Jr./Johnson Space Center morring@aviationweek.com 
Mission managers are carefully planning the space shuttle Discovery's return from orbit to bring back some five months of biological samples from cold storage on the International Space Station (ISS) without letting them overheat.
The station's freezer is full of blood, urine and other life-science samples scientists on the ground need for studying how humans adapt to long-term stays in microgravity, and it all must be kept at the proper temperature to be useful, according to Dan Hartman, ISS mission integration and operations manager here.
"What we're trying to do is preserve the research," Hartman said. "We basically have about a 125-hour clock."
That is more than sufficient to keep the samples at the required temperature range between 4 and minus 20 degrees centigrade in special cold bags that will return in middeck lockers on Discovery, provided the orbiter goes through its normal undocking and landing sequence.
But in a worst-case scenario, with the landing extended by two days because of landing-site weather, the temperature requirements for science might not be met. To give the samples as much time as possible in the freezer, managers decided today to wait until Wednesday to close the hatch between the station and Discovery, instead of closing it on Tuesday.
The crews will move the samples into the cold bags as late as possible before the hatch is closed. The late closing will give the crew a little more scheduled off-duty time on Tuesday, but it will push back Discovery's undocking Wednesday by four orbits -- about six hours.
The mission management team here gained the flexibility to rejigger the schedule by the extremely smooth deployment of the station's final solar array wing Friday morning. With engineers at Mission Control Center - Houston here watching over their shoulder electronically, the crew inched out the two halves of the final solar array wing out one at a time.
They stopped motion in the middle of each deployment to give the arrays time to warm in the sunlight to free chemical "stiction" between arrays jammed against each other in their launch boxes. The station also maintained a "solar inertial attitude," with the sun beaming on the same side constantly, for more of the warming effect.
Each array measures 115-by-38 feet when fully extended. First the crew deployed the array designated 1B to the aft of the starboard end of the station truss, using thrusters on the forward-facing shuttle orbiter to maintain attitude control without damaging the unfolding array.
After that they switched control of the station to engines on the Russian side of the massive spacecraft, and deployed array 3B forward toward the orbiter. That array had been packed longer than its counterpart, and gave the crew their only bad moment of the deployment when one of the "bays" appeared out of line when it stopped at the halfway mark. After warming in the sun for about 45 minutes, the wrinkled bay flattened out as the array was cranked out to its full extension.
Throughout the deployment, the combined station and shuttle crews monitored the action on the arrays carefully, both through windows and with video displays on the laptops they use to manage the station's systems.
NASA managers here were prepared to rewrite the scripts for the mission's remaining two spacewalks if it was deemed necessary to go outside to correct a problem. But in the end the arrays deployed fully in a little more than two of the four-and-a-half hours allotted to the task.
Photo: NASA
