The astronauts who will fly aboard Discovery have a much greater understanding of what went into the redesign effort ordered in the wake of the Challenger explosion than other shuttle crews.

Discovery skipper Frederick Hauck said the astronauts have become very involved in the decisions surrounding the redesign effort."I think we can say that we are very comfortable with where we are today in getting ready to fly Discovery," Hauck said. "I've been impressed with the way we've dealt with all the issues; not all of them have been easy to deal with.

"But what has been very reassuring to me has been the manner in which we've talked about them and the manner in which management has led all of us through in resolving the issues that existed and coming to an appropriate decision in that process," said Hauck.

Don Lind, who flew on the shuttle Challenger in April 1985, said the role the astronauts have in determining how the mission and hardware are structured has changed in 21/2 years.

"The astronauts have really quite a unique insight in that they're the ones who have to make the shuttle or the satellite or the experimental equipment work, and they need to have their input listened to early enough in the design that it can make some difference," said Lind, now a physics professor at Utah State University.

The job of the astronauts aboard Discovery, set for liftoff Thursday at 7:59 a.m. MDT, is lighter than in past missions. The primary objective, besides getting America back into space, is placing a communications satellite into orbit.

"This mission is not as complicated in the actual mechanics of the things we have to learn to do as the previous missions have been that we've all flown on," Discovery pilot Richard Covey said.

"So we've had the time to concentrate on those other things, the engineering development, the testing, the management reviews, the revision of our operating rules, to participate in all those things in much more detail than we would have on previous flights."

The five astronauts have played an active role in the redesign processes, giving their input on the $450 million solid rocket booster redesign and other phases of the project that have gone on since Challenger exploded Jan. 28, 1986.

The astronauts' roles in determining what goes and what doesn't, however, has been cyclical since the beginning of the space program.

"There was a movement 10 years ago because of local politics in Houston to give astronauts less say-so," said Lind, who isn't flying on the Discovery.

"And since the Challenger accident that has been reversed. It's not certainly gotten back to the position it was of Mercury and Gemini" when Lind said astronauts got what they wanted.

"See, we are the people who ride the vehicle, and we are very provincial in thinking we have a right to be involved in the value judgment as to whether the risk is acceptable," as all exploration carries risk, he said.

Discovery mission specialist Mike Lounge said the crew feels "confident that we've been included on every major decision - our input has been solicited on every major program management decision that the program has faced."

"We don't walk out of the room until we're satisfied the right question has been asked," Lounge said.

Hauck credits the appointment of former astronauts such as Rear Adm. Richard Truly and Robert Crippen to key spots in NASA flight management for the active role crews play in launch decisions.

Discovery "is significantly safer than the one I flew on. That doesn't mean it's perfectly safe, because there's no such thing as perfectly safe," said Lind.

"But they are handling this one like soft-shell egg, and this is going to be checked out, pampered, coddled - it's going to be ready to go when it goes off," the native Utahn said.