Weather outlook iffy for weekend shuttle launch
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: June 28, 2006
The shuttle Discovery is in good shape and on track for launch Saturday, but forecasters are predicting a 60 percent chance of electrically charged anvil clouds and afternoon showers Saturday, Sunday and Monday that would prevent takeoff.
Florida's summertime afternoon weather is always subject to change on short notice and as of this writing, launch managers plan to press ahead for what will be only the second shuttle flight in three years.
"Our teams have been working tirelessly during the last year to make this shuttle flight and all our shuttle flights, obviously, as safe as possible for the crews," said NASA test director Jeff Spaulding.
"As we approach our nation's 230th birthday, I'm proud to announce that the launch vehicle, the launch team and flight crew are ready to launch and continue our mission of completing the space station."
Discovery's countdown is scheduled to begin at 5 p.m. today, leading up to a launch attempt at 3:49 p.m. EDT Saturday, roughly the moment Earth's rotation carries the launch pad into the plane of the international space station's orbit.
Spaulding dismissed concerns about the weather, pointing out that on more than one occasion NASA was able to proceed with a launch despite forecasts as bad as 90 percent no-go.
"I think as always, if we have an opportunity to launch, the management team will sit down and make an evaluation and then make a go at trying to get off the ground," he said. "That's always our plan, to try to get off if we have an opportunity. Obviously these forecasts, while they sound a little bit gloomy, we've certainly launched with higher predictions than this, etc.. As always, we'll evaluate the weather real time and make a decision on the day of launch."
Engineers plan to load Discovery's electricity producing fuel cell system with liquid oxygen and liquid hydrogen Thursday afternoon. Once loaded, Discovery will have five days to get off the ground before a two-day stand down to top off the hydrogen tanks. The oxygen supply will be good for 12 days.
If Discovery can take off during the first three days of its window, enough hydrogen and oxygen will be available to permit a one-day mission extension and the addition of a third spacewalk to test heat-shield repair techniques. But after Monday, enough hydrogen likely will have boiled off in the fuel cell system to preclude an extra day.
Spaulding said no decisions have been made on whether NASA would make three launch attempts in a row to get Discovery off. The usual practice is two attempts in a row and then a day off to give the launch team a break. If that policy holds up, NASA will be able to make four attempts in five days before standing down for 48 hours to top off the hydrogen tanks.
Afternoon showers and thunderstorms are the rule on Florida's east coast in the summer months and Kathy Winter, an Air Force weather officer, said this week is no exception. While a ridge will push afternoon storms inland this weekend, electrically charged anvil clouds will pose a threat to Discovery's launch.
"Those thunderstorms, even though they'll be pushing inland, we'll be seeing anvils coming back from those thunderstorms and those are also dangerous when it comes to triggering a lightning strike. So our main concern is going to be those anvils coming back from those thunderstorms."
In addition, an inverted trough, or wave, to the west will bring more moisture into the area "and because of that, we could also see some isolated showers and cumulus clouds in the area of the launch pad and within 20 nautical miles of the shuttle landing facility," she said.
The weather is expected to be acceptable for at least one emergency runway in Spain or France, along with a backup landing site at Edwards Air Force Base in California throughout the weekend.
NASA's problem is the possibility of rocket-triggered lightning during launch and/or showers and low clouds that could prevent a safe return-to-launch site abort.
NASA flight rules require a "go" forecast for RTLS, meaning no worse than scattered clouds below 5,000 feet, visibility of at least four statute miles and crosswinds less than 15 knots. A shuttle cannot be cleared for launch if thunderstorms, lightning or rain are within 23 miles of the runway.