Spacewalkers plan to venture outside the International Space Station today while NASA decides if space junk will pose a threat Friday to the 13 astronauts aboard the outpost and shuttle Discovery. Officials were confident Wednesday evening that the station would not need to dodge a large piece of a spent European rocket booster - believed to be as large as 200 square feet - by firing shuttle thrusters.
"It's looking like we probably won't have to do that," said John McCullough, chief of the flight directors office. "But we are building a plan to allow us to make that decision as late as possible."
Managers had considered a debris-ducking option that would have delayed today's spacewalk, but later determined that Danny Olivas and Christer Fuglesang could proceed as scheduled with the replacement of coolant tanks outside the station.
It won't be until around 7 a.m. today that the probability of a collision is considered reliable. The station must move if that chance exceeds 1 in 10,000.
But a decision on whether to initiate a two-hour boosting maneuver could come late in the more than six-hour spacewalk, which is scheduled to start at 5:19 p.m.
The chunk of an Ariane 5 rocket was expected to make its closest approach just after 11 a.m. Friday.
McCullough said tracking on Wednesday showed it could fly within two miles of the station, but projections are refined with each orbit.
"It's a big piece," he said, adding that it would be easier to track as a result.
In addition to the spacewalk - the second of three planned during Discovery's mission - crews today will continue moving installing cargo hauled up by the shuttle.
On Wednesday, the joint crews took another step toward furnishing the station for serious science research after nearly 11 years of construction.
Astronauts began installing in the U.S. Destiny lab two racks that will be used to study materials and fluids in microgravity and a freezer for storing biological samples.
The research could discover new materials or applications for existing ones, while a advances in fluid physics could improve designs for fuel tanks and water systems, NASA says.
"This has been one of our major goals at the space station, is to be able to perform science in a microgravity environment, so having these racks available to the crew members, it is a big day," said Heather Rarick, lead station flight director for the mission.
Also Wednesday, three station crew members - including former KSC engineer Nicole Stott - reviewed procedures to grapple and dock an unmanned Japanese cargo spacecraft expected to arrive Sept. 16.
Here's a look at highlights of the day ahead, based on a schedule that does not include a debris avoidance maneuver:
++ 12:29 p.m. Discovery and station crews awake.
++ 1:04 p.m. Discovery mission specialists Danny Olivas and Christer Fuglesang resume preparations for the mission's second of three spacewalks.
++ 3:29 p.m. Cargo transferred to and from Leonardo module.
++ 5:19 p.m. Second spacewalk begins.
++ 6:14 p.m. New Ammonia Tank Assembly removed from carrier in Discovery's payload bay.
++ 7:34 p.m. Installation of new ammonia tanks on Port 1 truss segment begins.
++ 7:59 p.m. Old tank assembly removed from end of station's robotic arm.
++ 9:54 p.m. Old tank assembly placed on carrier in Discovery's payload bay.
++ 11:49 p.m. Second spacewalk ends.
++ 3:29 a.m. (Friday): Station crew sleeps.
++ 3:59 a.m. Discovery crew sleeps.
Keep following the action here and watch it live on our NASA TV viewer. Click on the NASA TV still image on the right side of the page to launch it.
No comments:
Post a Comment