Weather likely will delay final shuttle launch

Final space shuttle crew stands ready for launch on Friday. (NASA)

A tropical wave will bring showers and low clouds to the American Space Coast on Thursday and the system's effect will likely delay Friday's launch attempt of the final space shuttle mission.

Air Force weather officer Kathy Winters and her group issued a 30% chance that weather will be favorable for Friday morning's launch attempt by Atlantis, with not much of an improvement on Saturday with only a 40% of good weather.

"Our primary concerns for launch are showers and thunderstorms within 20 nautical miles of the Shuttle Landing Facility (runway), flight through precipitation, and cumulus clouds," Winters stated this morning from Cape Canaveral.

If weather keeps the space shuttle grounded, then NASA has only Sunday and maybe Monday to launch before standing down several days due to an Air Force rocket launch in the early hours of July 14.

The Eastern Test Range has always needed two full days to turn around following a Cape launch or a shuttle landing before moving on to the next launch.

NASA thus must launch Atlantis by Monday or face a five day delay for the Delta 4 rocket launch.

Rain showers could even delay the retraction of the protective service structure on Thursday afternoon, a planned prelaunch event which allows the space shuttle to be exposed to the elements.

Currently, launch remains planned for Friday at 11:26:46 a.m. EDT, from launch complex 39-A at the Kennedy Space Center.

A launch attempt on Saturday would see mission STS-135's solid rocket boosters ignite for launch at 11:04:15 a.m.

Launch time on Sunday would see Atlantis lift-off at 10:38:31 a.m., and for Monday 10:15:58 a.m.

Sunday's launch forecast currently improves to 60% favorable.

"With the launch time moving earlier and a slightly dryer atmosphere each day, the threat of weather decreases each day," Winters added this morning.

On Tuesday, the last shuttle launch countdown began on time at 1:00 p.m. at the T-43 hour mark. Several planned holds in the count will carry that time down to zero on Friday, for now.