Power payload handed from Discovery to the station
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: March 18, 2009
A $300 million, 31,000-pound solar array truss segment was plucked from the shuttle Discovery's cargo bay today, handed off, re-grappled and moved to an overnight park position near the right end of the international space station's main power truss for installation Thursday during a planned six-and-a-half-hour spacewalk.
NASA's Mission Management Team, meanwhile, wrapped up its initial assessment of launch photography, an inspection of the shuttle's nose cap and wing leading edge panels Monday and a photo survey of heat shield tiles on the orbiter's belly that was carried out during final approach to the station Tuesday.
The reinforced carbon carbon nose cap and wing leading edge panels, which experience the most extreme heating during re-entry, were given a clean bill of health and late today, engineers decided a damaged tile on the left inboard elevon, or wing flap, did not warrant any additional inspections.
As a result, time blocked out before launch for a "focused" inspection will be given up and deployment of the new S6 solar panels, originally planned for Sunday, will be moved up two days to Friday if Thursday's spacewalk goes well and no other problems develop.
"After fully analyzing the data, we've determined that the focused inspection is not required," astronaut Greg "Box" Johnson called from mission control. "So we're going to modify the timelime via the pre-flight agreement for no focused inspection. Margins are good for the RTV bond for that damaged tile and factor of safety is 1.8 or better. So we are ready to press with the pre-flight agreement."
"Houston, Alpha, got you loud and clear, Box," shuttle commander Lee Archambault replied from the space station. "Thank you very much! That's absolutely great news and we look forward to seeing the re-worked timeline."
Not having to carry out a focused inspection will help the crew stay on schedule in an already complicated mission and provide a bit of a cushion in case other problems develop. But so far, the astronauts have stayed on or ahead of schedule and had no trouble today getting the S6 truss segment from DIscovery's cargo bay to its overnight park position.
Because of interference issues, the shuttle's robot arm could not be used to pull S6 from the payload bay and the station's arm could not carry out the move by itself. Instead, the station's mobile crane, operated by John Phillips and Sandra Magnus, had to first pull S6 from its mounting point in the shuttle's cargo bay and then hand it off to the shuttle arm, operated by pilot Tony Antonelli, about two hours later.
The station arm's mobile base then moved down rails on the front face of the power truss to a work site at the far right end. The shuttle arm then extended S6 out over Discovery's right wing and Phillips re-grappled it with the station arm. The shuttle arm unlatched and S6 was maneuvered to a park position where it will not get too hot or to cold.
"This was a highly successful operation," Alibaruho said. "It required a great deal of choreography between the shuttle and the space station crews as well as the ground. We were very concerned about the controllability of the international space station, maneuvering such a heavy piece of equipment as the S6 truss from the payload bay to the overnight park position.
"But the spacecraft performed very well. The shuttle performed very well, we had no anomalies with either robotic arm. We actually ran slightly ahead of the timeline for most of the day. ... We are very pleased with what we were able to accomplish."
Astronauts Steven Swanson and Richard Arnold will spend the night in the station's Quest airlock at a reduced pressure of 10 pounds per square inch to help purge nitrogen from their bloodstreams. This is a standard pre-spacewalk procedure to ensure spacewalkers don't get the bends after working in NASA's 5-psi spacesuits.
The spacewalk, the first of three planned for Discovery's mission, is scheduled to begin around 1:13 p.m. Thursday.
In other work today, Magnus collected water samples from the station's potable water dispenser for shipment back to Earth aboard Discovery. Earlier testing showed the system had a higher-than-allowable bacteria count and an iodine solution carried up aboard Discovery was pumped in Tuesday.
"You may recall we conducted some activities last night to try to remediate some bacterial growth that was in the ambient temperature water line of that potable water dispenser," Alibaruho said. "We applied a biocide to that line yesterday and we let it soak overnight to make sure we reduced the bacterial count to an acceptable level.
"At this point, Sandy Magnus is following through with that procedure, which includes the collection of a water sample for return to the ground as well as an in-flight microbial sample, which will be read in a couple of days that we will use to verify the bacterial count is back to where we expect the system to normally operate."