A lightning strike at Launch Pad 39A during Friday afternoon's thunderstorm. Sensors counted 11 such strikes within 0.3 miles of the pad. Image

This story was updated at 11:44 a.m. EDT.

CAPE CANAVERAL, Fla. - The oft-delayed space shuttleEndeavour will have to wait at least one more day to launch while NASAinvestigates whether lightning strikes near the launch pad yesterday caused anydamage.

No positive signs of harm to Endeavour have yet been foundfrom the violent lightning storm Friday afternoon, but mission managers calledfor a 24-hour delay to investigate before resuming the countdownto lift off.

"We need to be 100 percent confident that we have agood system across the board," said Mike Moses, Endeavour's missionmanagement team chairman, during a Saturday briefing. "We've seen nothing sofar that indicates anything was actually affected by the lightning strike. But wehave to check and that?s what takes time."

Thunderstorms have lately plagued the seaside region of theKennedy Space Center here, and sensors counted 11 lightning strikes withinabout 0.3 miles of Endeavour's perch on Launch Pad 39A Friday.

Although no lightning directly impacted the orbiter, fueltank or solid rocket boosters (SRBs), a near enough strike could have induced astrong current that could disable the sensitive electronics in the orbiter, orthe pyrotechnics in the SRBs.

"The concern is mostly in those pyrotechnicsystems," Moses said. "There's a lot of things that have to go right.That?s why we need to double check everything."

Mission managers hope an extra day will be enough time to thoroughlycheck out Endeavour.

"I have high confidence we'll get there in 24 hours,but I certainly cannot guarantee it," Moses said.

If no serious signs of damage are found, Endeavour could tryto launch again as early as Sunday at 7:13 p.m. EDT (2313 GMT) on its planned16-day construction mission to the International Space Station. The weatheroutlook is slightly better for Sunday than today's forecast, with a 60 percentchance of favorable conditions expected.

Repeated Delays

Endeavour's STS-127mission has already been held at the ground after a persistent leak ofgaseous hydrogen twice prevented the shuttle from lifting off. NASA has saidthe leak, a potentially dangerous gas flow from a vent pipe leading off thevehicle's 15-storey external tank, has been fixed.

After a thorough investigation, ground crews traced theproblem to a misaligned plate on the tank. NASA repaired the plate andsuccessfully tested the system last week. Mission managers said they'reconfident the issue won't pose a problem anymore.

Commanded by veteran shuttleflyer Mark Polansky, Endeavour?s STS-127 mission will launch toward theInternational Space Station carrying vital spare parts and a Japanese-builtporch for the outpost?s massive Kibo laboratory. The marathon 16-day missionwill also ferry rookie NASA astronaut Tom Kopra to the station to replaceJapanese astronaut Koichi Wakata, who has lived aboard the orbiting lab sincelate March. Wakata is Japan's first long-duration astronaut and has watchedover his country?s $1billion Kibo laboratory at the station.

Set to launch spaceward aboard Endeavour with Polansky andKopra are STS-127 pilot Doug Hurley and mission specialists Chris Cassidy,Julie Payette, Tom Marshburn and Dave Wolf. Payette represents the CanadianSpace Agency, while the rest are NASA astronauts. Five spacewalks are planned.

Kopra is beginning a three-month mission to the spacestation as a flight engineer on the outpost?s six-man Expedition 20 crew. Hewill join two Russians, another American and astronauts from Belgium and Canadaon what is the station?s first full six-person crew.

Endeavour?s 16-day mission will mark NASA's third shuttleflight of the year and the second space station construction flight of 2009.

If Endeavour is unable to launch Sunday, a third attempt ispossible on Monday, with a 70 percent chance of good weather. NASA has untilJuly 14 to launch the shuttle before standing down to allow avoid a trafficconflict with an unmanned Russian cargo ship also due at the space station thismonth. If the mission is unable to launch by then, NASA can try again on July27.

SPACE.com is providing continuous coverage of STS-127with reporter Clara Moskowitz at Cape Canaveral and senior editor Tariq Malikin New York. Click herefor mission updates and SPACE.com's live NASA TV video feed. Live launchcoverage begins at 2:30 p.m. EDT (1830 GMT).