Mission Control informed the crew of six that the ship's thermal shielding is "100 percent cleared for entry" in another week.
"Boy, that is great news, that's fantastic," shuttle commander Steve Lindsey said. "And to get all that done by the end of flight day six ... is just amazing."
"Everyone here around the room, as you can imagine, is most happy," Mission Control replied.
Only one heat shield issue remained going into the late afternoon mission management meeting — a 2-inch-long piece of fabric filler sticking out about an inch from thermal tiles on Discovery's belly. Engineers determined it wasn't necessary to have an astronaut pluck the strip out during a spacewalk and that it posed no concern for the spaceship's return to Earth on July 17. So managers gave the heat shield an official bill of health.
Officials had already decided that several other nicks and spots — ranging from bird droppings to frayed fabric — were no big deal.
Deputy shuttle program manager John Shannon, chairman of the mission management team, said the healthy shuttle — and the crew's accomplishments in orbit so far — pave the way for the next mission in just over 1½ months. That's when assembly will resume at the international space station; construction was halted by the 2003 Columbia disaster.
Sandwiched between a daring spacewalk Saturday and a crucial but more routine spacewalk Monday, Discovery's crew had an easy day Sunday, said pilot Mark Kelly. They were scheduled to work only 15 hours, instead of 16 hours.
"Today has been a relatively light day compared to the others," Kelly said in the news conference. Those first five days of the mission were so busy "we had to take our meals on the run," Lindsey said.
Check for updates on Bill Harwood's Space Place.
Saturday's spacewalk, during which astronauts Piers Sellers and Michael Fossum stood on the end of 100 feet of sometimes-oscillating shuttle robotic arm and extension boom, proved that emergency shuttle repair work can be done from that unusual vantage point, the astronauts said. But they said the feeling of being out there at the end of the boom was a little unusual.
"You find yourself lying sideways when you think you're standing up," Sellers said. "It's an unnatural feeling, but not really very unpleasant."
The second spacewalk, which begins at 8:13 a.m. EDT Monday, is much like past international space station repair spacewalks. The bulk of the scheduled 6 1/2-hour spacewalk will concentrate on finishing repairs on the station's railcar-like mobile transporter. This is a crucial piece of the station that slides back and forth, helping in the expansion of the outpost.
"We need that thing to be working to move big pieces around during assembly," Sellers said Sunday. "It was dead on one side, kind of limping on just two wheels."
Sellers and Fossum will replace part of the transporter's umbilical reel, which weighs about 330 pounds on the ground. In what may be an awkward maneuver, Sellers will be holding the old umbilical in one hand and the new one in the other, Fossum said.
"The most challenging thing tomorrow is going to be just the choreography, going back and forth in the payload bay," Fossum said. "It's quite a ballet."
NASA planned to post on its Web site Sunday first-of-its-kind video of Discovery's launch as seen from the reusable solid rocket boosters. The video, recovered last week with the boosters, mesmerized engineers in Houston on Saturday.