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NASA's 'Groundhog Day'

— We aren't even close to Saturday afternoon's scheduled launch attempt for the shuttle Discovery, and already folks here at Kennedy Space Center in Florida are talking about the prospect for repeated countdown resets reminiscent of the comedy "Groundhog Day," in which Bill Murray lives out the same day over and over again.

The reason? It's not because of technical glitches - none of those are in sight, NASA test director Pete Nickolenko said at this morning's countdown status briefing. Rather, it's the weather forecast that sounds like a broken record: 60 percent chance of unacceptable weather for launch, due to afternoon thunderstorms and anvil clouds. That forecast currently applies to Saturday, Sunday and Monday.

"It's not an ideal situation when it comes to the weather," shuttle weather officer Kathy Winters admitted.

Nickolenko said the most likely scenario would be for mission managers to make launch tries on Saturday and Sunday, take Monday off, then try again Tuesday and Wednesday.

The off day on Monday would be to give the crew a break, he said. It's no picnic for the crew to get up in the wee hours of the morning, have them suit up and strap in, and then have to bring them back out of the shuttle day after day.

"It's like 'Groundhog Day,'" he explained. "That can get kind of old and difficult."

NASA can schedule four launch attempts over a five-day time frame, and then there have to be a couple of days set aside to replenish the shuttle's onboard cryogenic fuel, shuttle launch director Mike Leinbach said this afternoon. Once that's done, the five-day cycle would begin again.

Winters said the relatively monotonous forecast is actually in line with the usual pattern for Florida in the summer (PDF file). This week might be a little different only in terms of how much moisture is behind the cloud systems, and how pressure ridges happen to be steering the weather.

Several factors are giving the shuttle team hope that it won't get as bad as "Groundhog Day," however: One is that a 60 percent chance of no-go weather still leaves a 40 percent chance for launch. Nickolenko told reporters that launches have gone off even when the forecast was 80 percent unfavorable.

Another factor is that the steering ridge behind the storm pattern looks to be gradually shifting from south (bad) to north (good), Winters said.

But the biggest hope for Discovery's launch during the July 1-19 window is that each day, the scheduled launch time shifts about 23 minutes earlier, due to the changing orbital mechanics behind the shuttle's rendezvous with the international space station. Afternoon thunderstorms don't pose a problem if you're launching before the storms blow in.

"As that launch time goes earlier, that is the one thing that could help us over time," Winters said.

Update for 6:20 p.m.: Leinbach's description of the launch cycle made clear that it's a five-day cycle. After today's launch readiness review, mission managers said that there were no constraints on the launch other than the weather. We'll have further updates in our "Return to Flight" section. By the way, the skies clouded up and sent down the occasional sheets of rain as usual this afternoon.