HOUSTON - NASA shuttle officials are withholding a final judgment on whether the Discovery orbiter's heat shield is safe for the return trip until after a team of analysts completes a meticulous survey of the up-close images taken during a Friday inspection.
"They may tell me tomorrow, they may tell me Sunday," said John Shannon, NASA's deputy shuttle program manager, of when analysts expect to complete their work. "I'll get it when I get it."
On Thursday, Shannon expressed hope Discovery's heat shield would be cleared for reentry by the end of this weekend.
Earlier today, STS-121 mission specialists Stephanie Wilson, Lisa Nowak and shuttle pilot Mark Kelly relayed home a batch of high-resolution images aimed at cementing the case. The imagery featured six key areas that engineers requested after going through photographs of Discovery's heat shield snapped from the International Space Station (ISS) during Thursday's docking.
Of those six areas, several appear to have been settled - among them a frayed bit of fabric from a so-called "tadpole" gap filler just aft of Discovery's nose landing gear and a small white blotch on the orbiter's nose - though NASA orbiter project manager Steve Poulos said final imagery analysis is still pending on both items.
Poulos said a bit more scrutiny is required over a protruding gap filler peeking up perhaps an inch above the surrounding heat-resistant belly tiles near the orbiter's wing flap. The protrusion is near door that covers an external tank connection and could lead to higher than expected heating aft of the gap filler than reentry. Analysis of both the thermal and structural effects of such heating is anticipated to be complete by Sunday, he added.
Several images of sites along the middle of Discovery's starboard - or right - wing leading edge have caught the eye of analysts as well, since they show dark marks on the heat-resistant reinforced carbon carbon panels that experience some of the highest temperatures - up to 2,960 degrees Fahrenheit - seen during reentry.
"Once we get the high fidelity imagery, it's either not an issue or something we'll need to be worried about," Poulos said if the RCC panel areas. "I think we'll have that information here this evening."
Aside from the six suspect areas, Poulos said Discovery is in ship shape.
"Orbiter systems couldn't be functioning better," Poulos said. "We are really not tracking anything significant, hardly anything at all to be honest."
Discovery is flying NASA's second shuttle flight since the 2003 Columbia accident. Recently extended one day to a 13-day mission, the STS-121 spaceflight will resupply the ISS, leave a third crewmember aboard, make repairs to the outpost and test shuttle inspection and repair methods.
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