The shuttle Discovery's countdown is ticking smoothly toward blastoff Wednesday, but forecasters said today the launch likely will hinge on whether afternoon showers move out of the area before the opening of the shuttle's short launch window. Liftoff is targeted for 3:50:52 p.m. Wednesday.

Shuttle forecaster Kathy Winters downgraded the forecast from 70 percent "go" to 60 percent Wednesday, Thursday and Friday. The primary concern is showers or thunderstorms within 20 nautical miles of the shuttle's emergency runway.

"As the sea breeze forms, we're going to see some showers and possibly even a thunderstorm develop during the countdown," Winters said. "But then as the sea breeze progresses to the west with the easterly flow, we should actually see an improvement in our weather at the launch pad.

"What our main concern is going to be is that these storms will move far enough to the west to be beyond the 20-nautical-mile ring around the Shuttle Landing Facility, which is our return-to-launch-site (abort) concern. So we are expecting to see some weather in the area, but it should progress to the west."

A shuttle main engine failure or some other major malfunction in the first few minutes of flight would force the crew to attempt an emergency return to the Kennedy Space Center. Because the shuttle makes a gliding approach and only has one shot at the runway, NASA flight runs require relatively clear sky, no rain and crosswinds of 15 knots or less. The 20-nautical-mile circle around the runway is intended to ensure good landing conditions a half-hour after launch when a returning crew would be on final approach.

NASA test director Jeff Spaulding said there are no technical problems of any significance at pad 39B, although NASA managers plan to meet later today to resolve a few lingering technical issues.

Overall, Spaulding said, "the vehicle is ready, the team's ready, I think our nation is ready and it seems like our weather will be ready so that we can begin our historic mission of returning the shuttle to flight and bringing our crew safely home."

Said payload manager Scott Higginbotham: "This has been a long journey for all of us, it's been a long story in many of our lives but we're all committed to seeing that we have a happy ending."

Spaulding said Discovery's crew - commander Eileen Collins, pilot James Kelly, flight engineer Stephen Robinson, Andrew Thomas, Wendy Lawrence, Charles Camarda and Japanese astronaut Soichi Noguchi - are in good spirits and ready to go.

"Their mood is one of excitement as is ours and they're anxious to get back to launching," he said. "They've been training for an awful long time and certainly, they're prepared and ready for this mission. That's their focus right now."

Discovery's crew plans to honor the memory of the Columbia astronauts in a ceremony aboard the shuttle on July 20, the 36th anniversary of the Apollo 11 landing on the moon in 1969. Earlier today, the families of the Columbia astronauts wished Discovery's crew well. Here is their statement:

"As NASA prepares to launch the Shuttle Discovery, we, the Columbia Families, would like to show our support for the STS-114 crew and all the dedication and talent of those who supported this Return to Flight effort. We have had two and a half years to reflect daily on the loss of our loved ones as the Shuttle Columbia (STS 107) broke apart over Texas on February 1, 2003.

"In the aftermath of the Columbia tragedy we saw our nationšs space program reinvent itself. The extraordinary efforts of local, state and national organizations involved in the recovery effort, the Columbia Accident Investigation Board, the Return to Flight Task Group and all the NASA and aerospace industry workforce implementing the Return to Flight effort have clearly done an exemplary job in defining and reducing the technical risk as much as possible. As the families of Apollo 1 and Challenger before us, we grieve deeply but know the exploration of space must go on. We hope we have learned, and will continue to learn, from each of these accidents, so that we will be as safe as we can be in this high risk endeavor.

"As important as solving the technical risk is, we must be vigilant to ensure the organizational and cultural issues that contributed to Apollo, Challenger, and Columbia are forever remembered. Under the leadership of the new NASA Administrator, we have every confidence that the sacrifice of our loved ones and those that preceded them, will be realized for the benefit of all humankind.

"Godspeed Discovery."

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