Shuttle heat shield in good shape for entry
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: May 13, 2009;
Updated at 8:10 p.m.
NASA's Mission Management Team late Wednesday completed an initial assessment of the shuttle Atlantis' heat-shield tiles, blankets, reinforced carbon carbon nose cap and wing leading edge panels and decided no additional "focused" inspections will be needed until the end of the mission.
One small area of 16 tiles on the left side of the fuselage near the nose was not fully inspected because of a camera tracking overlap problem, but flight controllers told the crew those tiles could be inspected later, after an upcoming spacewalk, using the camera on the end of the shuttle's robot arm.
"The team's have been working very hard looking at all the data from all the survey work you guys did on flight days one and two and ... I can happily tell you no focused inspection is required," astronaut Alan Poindexter radioed from mission control in Houston.
"Well, that is good news," shuttle commander Scott Altman replied from Atlantis. "I know they had to work basically overtime, full-time, quarter-time, all the time to get all that work done and that data analyzed faster than we've done it before. So we appreciate that, it's great to know that tomorrow we can just focus on the EVA (spacewalk) and not worry about setting up for a focused inspection. So thanks to the team for all the work. We feel very good and confident in this report."
The Atlantis astronauts grappled the Hubble Space Telescope earlier Wednesday, mounting it in the ship's cargo bay for a five-spacewalk repair job. At Hubble's high altitude, the shuttle crew is at slightly higher risk - the mean value is 1-in-229 - from impacts with space debris.
Late Wednesday, flight controllers notified the astronauts they were tracking a 4-inch-long piece of debris from a recent Chinese anti-satellite test that was predicted to pass 1.7 miles in front of the space shuttle. While the debris required close monitoring, the astronauts were not required to carry out any avoidance maneuvers.
But the debris risk is real and LeRoy Cain, chairman of NASA's Mission Management Team, said sensors in the wing leading edge system recorded a presumed space debris impact earlier, on panel No. 11 on Atlantis' right wing. But the magnitude of the impact was an order of magnitude below the threshold that could cause noticeable damage.
"You know we have the wing leading edge impact indication system that we have turned on to monitor for any kind of MMOD (micrometeoroid/orbital debris) or other impacts we might have during the on-orbit phase," Cain said. "It did register an impact, or indications or an impact, on the right-hand side, on panel 11R of the reinforced carbon carbon part of the wing leading edge.
"The indication was .47 Gs. The team evaluated it through the normal screening process. We do think, by all indications as far as we can tell, we do think it's probably a real indication of an impact. ... We're not concerned that it's done any kind of damage that would be any concern to us, certainly not critical damage. We think if anything, just very, very small coating damage. We'll get a look at this area again when we do a late inspection (near the end of the mission) in any case. But this is not an indication we're concerned about at this time."
Asked what sorts of forces would cause real damage for a wing leading edge panel, Cain said "there are many, many different variables. But we're talking, generally speaking, in a number of Gs. This is less than .5 Gs. It's, generally speaking, an order of magnitude greater than what we're seeing here."
During initial inspections of the shuttle's heat shield Tuesday, the Atlantis astronauts downlinked images showing minor tile damage on the shuttle's right wing. Engineers decided Tuesday night the damage was of no consequence and would not require an additional, focused inspection.
"The team came back today and we have essentially cleared all of the TPS (thermal protection system) for the tiles and for the blankets," Cain said. "So essentially, all the TPS save for the RCC (reinforced carbon carbon) we've cleared for entry. We've also said we don't need any focused inspection for any of the TPS."
Shortly after Cain's briefing, the reinforced carbon carbon nose cap and wing leading edge panels were cleared as well.
The only other issue of note, Cain said, was photography showing a fine particulate dusting a handrail and insulation blankets on a carrier box housing the new Wide Field Camera 3 that will be installed in the Hubble Space Telescope during a spacewalk Thursday.
Cain said the white power-like substance was not present before launch and may be some sort of material that shook loose from payload bay bulkhead insulation blankets during the climb to space. Because of concern about possible contamination of the new camera, Cain said the spacewalkers would take extra care to avoid the dust when the camera is removed from its case Thursday.
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