U.S. space agency officials are readying themselves for the most closely watch phase of the Discovery mission, the landing of the space shuttle. It was during re-entry into the Earth's atmosphere two-and-a-half years ago that the space shuttle Columbia disintegrated, killing all seven astronauts.
The Discovery mission marked the resumption of the space shuttle program after it was grounded following the Columbia disaster in February of 2003.
Columbia was doomed when a piece of insulating foam flew off its external fuel tank during take off, cracking a protective heat tile on the shuttle's wing. Because of the damaged tile searing hot gasses were able to burn a hole in the wing of the craft, which broke up in a fireball during reentry into the earth's atmosphere.
Some pieces of foam also came off the external fuel tank during the launch of Discovery, but mission engineers do not believe the debris caused any significant damage.
Now, NASA is bracing for the landing of Discovery, scheduled for early Monday.
Flight entry director LeRoy Cain says he's nervous about the landing, as he is about every aspect of his job.
"There's a lot of things to think about," he said. "There's a lot of things to worry about, and that's what I get paid to do, is to worry. And I do it a lot. So, quite honestly and frankly, if I didn't feel that way, I'd been concerned that I wasn't in the right frame on mind."
If the space shuttle runs into technical problems, Mr. Cain says mission controllers can postpone the landing.
During the thirteen day mission, Discovery's space-walking astronauts carried out an unprecedented repair mission to remove some protruding gap filler that was sticking up from between the protective heat tiles on the belly of the shuttle. Engineers on the ground had worried if the strips weren't removed, they could cause dangerous overheating during re-entry and lead to a repeat the Columbia disaster.
Mission controllers were able assess the situation using the many cameras that captured images of almost every centimeter of Discovery's exterior, from launch and now, until landing. The cameras are a response to the Columbia disaster.
Mr. Cain was asked whether all the extra information makes him more anxious about the shuttle's landing.
"Anytime that you have more data, you have more to think about. And so therein lies somewhat of a challenge," he said. "But I would tell you, I think as most of us would tell you, that I would rather have more data, because it makes you better prepared."
Forecasters are predicting good weather for Discovery's landing at Kennedy Space Center in Florida. If that changes, NASA says it will try again on Tuesday.