The Mission Management Team will gather at 8 a.m. EDT to review test results from the engineers double-checking shuttle systems and circuitry for any signs of lightning damage. If all looks good, officials will give approval to proceed with the countdown and begin fueling Endeavour at 9:48 a.m. EDT.

A photo gallery showing the lightning strikes hitting at launch pad 39A can be viewed here.

The astronauts will be awakened to begin launch day preparations at 8:15 a.m. EDT. Breakfast is scheduled for 8:45 a.m., followed by medical exams.

The crew spent another quiet day in quarantine after Saturday's scrub. Commander Mark Polansky, however, did get some time in the Shuttle Training Aircraft.

The seven astronauts will suit up a little before 3 p.m., then depart from crew quarters at 3:23 p.m. and arrival at the launch pad a half-hour later to start strapping aboard the shuttle. Endeavour's crew module hatch is scheduled to be closed for flight around 5:10 p.m. EDT.

The targeted liftoff time for Sunday's launch opportunity is 7:13:55 p.m. EDT. That's the moment when Earth's rotation carries the launch pad into the plane of the station's orbit.

The two-pane launch window, which includes Flight Day 3 and Flight Day 4 rendezvous scenarios, extends from 7:08:55 p.m. to 7:22:06 p.m. EDT.

The updated NASA Television schedule for Sunday can be downloaded here.

The launch weather team has updated the official forecast for Sunday and improved the odds of favorable conditions. There's now a 70 percent chance that the weather will be acceptable for Endeavour's liftoff at 7:13 p.m. EDT.

The specifics call for showers and thunderstorms inland, just a few clouds at 3,000 feet, scattered cirrus at 25,000 feet, visibility of 7 miles, launch pad winds from the southeast at 8 peaking to 12 knots and a temperature of 82 degrees F.

The primary concern will be showers or storms within 20 miles of the Kennedy Space Center runway where Endeavour would make an emergency landing in the event of a problem during launch.

Here's the outlook for today through Tuesday, as provided by Air Force meteorologists a short time ago:

"Weather will not be as active today as yesterday. The upper-level trough that was over Florida yesterday has moved east of Florida. Afternoon thunderstorms will remain along the sea breeze rather than being more wide spread across the area. The sea breeze has already moved over Merritt Island, west of complex 39A. As showers and thunderstorms develop along the sea breeze, some lightning may occur within 5 nautical miles of the launch pad.

"Tomorrow, winds through the atmosphere are lighter, and the weather that develops along the sea breeze should progress further inland; therefore, weather is more favorable for launch. Our primary concerns for launch are showers and thunderstorms within 20 nautical miles of the Shuttle Landing Facility (SLF).

"Monday and Tuesday, the surface winds will be stronger from the southwest, and the sea breeze will develop later in the day. This may cause showers and storms to be in the area near launch time."

There's a 60 percent chance of acceptable weather both for Monday's 6:51 p.m. launch time and Tuesday's 6:25 p.m. opportunity. Conditions at the shuttle runway and cumulus clouds will be the concerns on those days.

Already a month behind schedule, launch of the shuttle Endeavour on a 16-day space station assembly mission was delayed at least 24 hours, from Saturday to Sunday, to give engineers time to evaluate the effects of multiple lightning strikes at the launch pad during a severe thunderstorm Friday.

Read our full story.

NASA has released a still image taken from one of the launch pad video cameras showing the lightning mast getting hit Friday night. See the picture here.

The official tally on the lightning strikes from last night is 11 hits within 0.3 miles of the pad. The pad's water tank was hit and the lightning mast was struck a couple of times.

Mission Management Team chairman Mike Moses says additional checks are needed to build confidence that there's no problems with orbiter electronic boxes and the solid rocket booster pyrotechnic circuitry.

No damage has been found in the shuttle and ground systems that have been checked so far.

The weather forecast for Sunday's planned 7:13 p.m. EDT launch of shuttle Endeavour predicts a 40 percent chance that weather will prevent a liftoff due to thunderstorms and electrically-charged clouds.

The specifics at launch time include showers and thunderstorms in the vicinity, scattered clouds at 3,000 and 8,000 feet, broken cirrus at 25,000 feet, visibility of 7 miles, launch pad winds from the southeast at 8 peaking to 12 knots and a temperature of 82 degrees F.

The outlook for Monday's 6:51 p.m. launch time has only a 30 percent chance of unfavorable weather.

"The launch of space shuttle Endeavour has been postponed for 24 hours to allow the launch team sufficient time to perform evaluation and retesting of launch pad and launch vehicle sytems as the result of lighting strikes near the launch pad last night. So far, no damage to the space shuttle Endeavour or to launch pad systems have been found. Launch of Sunday is targeted for 7:13 p.m.," NASA spokesman George Diller says."

The targeted liftoff time for Sunday's launch opportunity is 7:13:55 p.m. EDT. That's the moment when Earth's rotation carries the launch pad into the plane of the station's orbit.

The official window for extends from 7:08:55 p.m. to 7:18:55 p.m. EDT. Launching within that 10 minute period will enable Endeavour to dock with the International Space Station on Tuesday.

An additional three minutes and 11 seconds in the form a second pane of the launch window exists until 7:22:06 p.m. EDT. However, launching within that pane would lead to a later rendezvous and a Wednesday docking.

NASA is planning an 11 a.m. EDT news conference about today's decision to postpone Endeavour's launch by 24 hours. The delay will give engineers more time to ensure the lightning strikes around the pad last night didn't cause any damage.

SCRUB! Today's launch attempt has been called off.

There were 9 lightning strikes within close proximity to the launch pad during storms that rolled over the Cape Canaveral area last night, a NASA spokesman says. Engineers are making sure those strikes did not cause any harm to ground equipment or systems aboard Endeavour.

NASA pushed back the start of this morning's pre-fueling Mission Management Team meeting to give engineers more time to check systems.

The start of fueling has been pushed back approximately 30 minutes while the Mission Management Team reviews information about lightning strikes that hit the pad area last night.

T-minus 6 hours and counting! The coundown has resumed ticking after the two-hour planned hold. The next scheduled hold occurs at T-minus 3 hours. Later pauses happen at T-minus 20 minutes and T-minus 9 minutes to give the launch team time to catch up on work running behind schedule and deal with any problems. Liftoff is targeted for precisely 7:39:38 p.m. EDT.

We're now standing by for the start of fueling operations.

The weather team is briefing mission managers on the conditions expected during this morning's fueling and this evening's scheduled launch of Endeavour.

The official forecast during the start of fueling calls for some scattered low-level clouds, good visibility, north-northwesterly winds of 5 knots, a temperature of 78 degrees and relative humidity of 82 percent. There's just a 10 percent chance lightning within 5 miles of the pad.

For the 7:39 p.m. EDT launch today, the forecast continues to predict a 60 percent chance that weather will prevent a liftoff due to thunderstorms and electrically-charged clouds.

The specifics at launch time include clouds at 3,000 and 8,000 feet, broken cirrus at 25,000 feet, visibility of 7 miles, launch pad winds from the southeast at 8 peaking to 12 knots and a temperature of 82 degrees F.

The astronauts were awakened at 8:45 a.m. They're about to have breakfast.

A short time ago, commander Mark Polansky tweeted on his Twitter page: "Good morning! Launch day is here again. As far as weather goes, my philosophy is it's always 50/50. Either it'll be good or it won't."

T-minus 6 hours and holding. Countdown clocks have just paused for a planned two-hour hold prior to fueling of space shuttle Endeavour. This is the latest in a series of holds that are built into the three-day countdown sequence leading to launch at 7:39 p.m. EDT.

During this hold, the Mission Management Team will gather for its readiness meeting to give approval for fueling while the launch team determines if there are any constraints with loading the shuttle's external tank starting at 10:14 a.m.

The gantry-like rotating service structure at Kennedy Space Center's pad 39A has been retracted from Endeavour in preparation for Saturday's liftoff on the next construction flight to the International Space Station.

Currently, countdown clocks are stopped at the T-minus 11 hour mark for a planned built-in hold. The count is scheduled to resume ticking at 3:14 a.m. EDT. This morning's work includes activating the Endeavour's inertial measurement units and power-generating fuel cells, plus checking all of the switches in the cockpit to ensure they are in the correct positions for launch.

Final closeouts of the pad and clearing of the hazard area will be finished by daybreak. The count will proceed down to the T-minus 6 hour point where a two-hour hold begins at 8:14 a.m. During that pause, the launch team will verify all systems are ready to begin loading a half-million gallons of supercold rocket fuel in the shuttle's external tank.

The three-hour fueling process is scheduled to commence around 10:14 a.m. EDT, pending a final "go" from the Mission Management Team's evening meeting to review the status of the count.

Launch remains scheduled for 7:39 p.m. EDT Saturday evening.

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The gantry is clear of the orbiter and continuing to swing back. Endeavour has been unveiled once again for this mission, which is set for its third launch attempt Saturday evening.

Tower rollback has begun. The structure typically moves back a few feet to a normal stop point while technicians confirm all is ready to drive the gantry all the way to the launch position.

At launch pad 39A, ground crews are preparing to roll back the rotating service structure away from space shuttle Endeavour. The retraction is scheduled for about 11 p.m. EDT. You can watch it live in our NASA Television webcast on the right-hand side of this page.

The gantry has provided the primary access and weather protection for the shuttle during its stay on the seaside complex. The structure's retraction will reveal the orbiter and accomplish a key milestone in the countdown.

The astronauts' last day in the ground before launching on their marathon spaceflight included free time and some status briefings on the shuttle, payloads and weather outlook. They'll begin a final pre-launch sleep period at 12:45 a.m. EDT.

Flight Day 1 for the mission starts with a wakeup call in crew quarters at 8:45 a.m. Breakfast is scheduled for 9:15 a.m., followed by medical exams. After some time to relax, they'll have a pre-launch snack at 1:25 p.m.

The seven astronauts will suit up shortly after 3 p.m., followed by departure from crew quarters at 3:49 p.m. and arrival at the launch pad a half-hour later to start strapping aboard the shuttle. Endeavour's crew module hatch is scheduled to be closed for flight around 5:30 p.m. EDT.

The official launch window, based on the latest radar tracking of the space station's orbit and subsequent revision from Mission Control, extends from 7:34:37 p.m. to 7:44:38 p.m. EDT. The targeted liftoff time occurs in the middle of the window at 7:39:38 p.m. EDT. That's the moment when Earth's rotation carries the launch pad into the plane of the station's orbit.

The shuttle Endeavour's countdown is ticking smoothly toward launch Saturday evening on a delayed space station assembly mission to attach an experiment platform to a Japanese lab module, to replace aging solar array batteries and to deliver spare parts and supplies.

See our full story.

NASA's Mission Management Team met this morning and confirmed that there are no issues standing in the way of Saturday's liftoff.

"Everybody is 'go' for launch," chairman Mike Moses said.

"So the bottom line is all of our systems continue to proceed quite well, the countdown is right on track and on target and I can say all of our flight and ground teams are ready to launch this time," says Pete Nickolenko, the shuttle launch director.

Air Force weather forecasters continue to predict a 60 percent chance that thunderstorms will interfere with Saturday's scheduled launch of shuttle Endeavour.

"A long wave, upper-level trough has deepened over the Florida Peninsula, and the surface front is located in Northern Florida. The atmosphere over Central Florida is moist and unstable, and widespread afternoon thunderstorms are expected this afternoon. There is also a risk of a severe storm in the area today due to cold temperatures aloft," meteorologists reported this morning.

"By Saturday, the surface front will be in the Central Florida area. The upper-level trough will begin to migrate northeast, but early afternoon showers and thunderstorms will develop along the sea breeze, and the front in the area will act as an added trigger for these storms. Most of the activity will occur before the launch window, but weather may still be in the area by launch time.

"Our primary concerns for launch are showers and thunderstorms within 20 nautical miles of the Shuttle Landing Facility (SLF) and anvils."

The outlook for the 7:39 p.m. EDT launch time includes showers and thunderstorms in the vicinity, scattered clouds at 3,000 and 8,000 feet, broken cirrus at 25,000 feet, visibility of 7 miles, launch pad winds from the southeast at 8 peaking to 12 knots and a temperature of 82 degrees F.

If the launch is delayed for some reason, the odds of good weather improve on Sunday and Monday.

Cryogenic reactants for Endeavour's three fuel cells were loaded into storage tanks aboard the orbiter last night as expected. The liquid hydrogen and liquid oxygen will be used to produce the electricity to power the shuttle's systems during the 16-day mission.

The planned activities for today include final tests of the three main engines, functional checks of the orbiter's star trackers, activating the inertial measurement units, thoroughly testing the communications network, loading the last items into the crew module, filling of the launch pad's sound suppression system water tank and installing film in pad cameras.

Countdown clocks will enter the lengthy T-minus 11 hour planned hold period at 2 p.m. EDT. The built-in hold will last 13 hours and 14 minutes.

The giant gantry-like rotating service structure is scheduled for retraction from around Endeavour at 11 p.m. tonight.

"Our systems are in excellent shape, we have no issues to report," says Steve Payne, NASA test director. "The STS-127 flight crew, Endeavour and the launch team are ready to go. We're all very excited to be back in launch countdown."

Liquid hydrogen and liquid oxygen for space shuttle Endeavour's electricity-generating fuel cells will be loaded into storage spheres beneath payload bay beginning around 7:30 p.m. EDT as standard work continues at pad 39A for Saturday's launch.

The cryogenic reactants are combined by the three omboard fuel cells to produce power and a byproduct of drinking water during the shuttle's mission. Technicians pump the cryogenics into small tanks aboard the orbiter during a multi-hour operation, then later demate the pad umbilical system used in the loading process and stow that equipment for launch.

The astronauts were awakened in crew quarters at 8:45 a.m. EDT and underwent medical exams a short time later. The crew's schedule includes time to study mission procedures, relax before flight and jet training runs.

The Mission Management Team will hold its Launch Minus-2 Day meeting Friday morning to review the status of work and grant approval to continue with the countdown toward launch. A post-meeting news conference is planned for 11:30 a.m. EDT.

The weather outlook for Saturday's launch opportunity remains unchanged.

See our full story on the countdown starting.

COUNT BEGINS. Countdown clocks at the Kennedy Space Center just began ticking toward Saturday evening's scheduled launch of the space shuttle Endeavour and the marathon 16-day mission to the International Space Station.

The official countdown sequence began at 10 p.m. EDT inside Firing Room 4 of the Complex 39 Launch Control Center. Launch team members had gathered for the "call-to-stations" at 9:30 p.m. EDT.

The early portion of the count involves buttoning up launch pad equipment and removing platforms inside the shuttle's crew module, reviewing flight software stored in Endeavour's mass memory units, loading backup software into the general purpose computers and testing navigation systems.

The count began from the T-minus 43 hour mark. But a series of holds are timed throughout the next few days, leading to Saturday's targeted liftoff time of 7:39 p.m. EDT.

The first official weather forecast for space shuttle Endeavour's planned Saturday launch was issued this morning and meteorologists are projecting a 60 percent chance that summertime thunderstorms will delay the liftoff.

"The weather certainly has been an issue for us this week. We've had afternoon thunderstorms each day, and we're also expecting we'll see some afternoon thunderstorms in the area around launch time on launch day as well," weather officer Kathy Winter says.

The outlook for the 7:39 p.m. EDT liftoff time on Saturday calls for scattered low- and mid-level clouds, broken high clouds, 7 miles of visibility, southeasterly winds of 8 peaking to 12 knots, a temperature of 82 degrees, and thunderstorms and anvil clouds in the vicinity.

The storms and associated electrically-charged clouds are troublesome not only for the shuttle's launch but also in the event Endeavour has to make an emergency return to the Kennedy Space Center landing strip immediately after liftoff.

"The primary concerns will be thunderstorms and anvils. They should be off to our west, sitting along the seabreeze, but that may be within the 20 nautical miles of the Shuttle Landing Facility, which is a Return to Launch Site concern. Also, anvils blowing off the top of those thunderstorms may migrate back towards our area. And with that, we do have a 60 percent chance of KSC weather prohibiting launch."

If the launch is delayed to Sunday's launch opportunity at 7:13 p.m. EDT, the odds of bad weather lessen to 40 percent. The forecast for Monday's 6:51 p.m. launch time is even better at just a 30 percent chance of weather problems.

There are no weather concerns at the overseas abort landing sites in France and Spain for any of the three days, forecasters say.

The launch team will gather in the control center tonight to start up the countdown clock at 10 p.m. EDT.

"I know the flight crew and the launch team are very excited about this launch countdown. We're all eager to get Endeavour and her crew on their way to the International Space Station," said Charlie Blackwell-Thompson, a NASA test director.

"Endeavour is in great shape. Our launch countdown preparations are going well, our work is on schedule, I have no technical issues to report. We're ready to fly this mission."

A replay of the astronauts' arrival and commander Polansky's comments can be viewed in our STS-127 video archive.

After spending an extra month on the ground while a gaseous hydrogen leak was fixed, space shuttle Endeavour's astronauts today arrived at Kennedy Space Center from Houston looking fit and eager to finally get their space station construction mission underway Saturday evening.

The six-man, one-woman team of astronauts flew from their home base to the Cape aboard a Gulfstream jet, landing nearly 45 minutes ahead of schedule on the same runway Endeavour will use to conclude the 16-day spaceflight.

"Good afternoon. It's great for the crew to be back at the Kennedy Space Center," commander Mark Polansky told reporters just after arriving.

The crew also includes rookies Doug Hurley as pilot, Chris Cassidy, Tom Marshburn and Tim Kopra serving as mission specialists, plus experienced Canadian astronaut Julie Payette flying for the second time and Dave Wolf, a veteran of previous shuttle and space station Mir flights.

"I would just like to take a moment to recognize the outstanding work that was done by the workforce here and at the other NASA centers to go ahead and correct the problems that we encountered last month. Now it's ready for STS-127 to carry out its mission, and I can tell you this crew and the entire operations team are both eager and ready to get to work. So hopefully we will get a chance to do that come this Saturday evening," Polansky said.

"So thanks very much for coming out and hopefully the next time we talk to you will be from orbit."

After a quick photo opportunity, the astronauts were bussed away. Their schedule for the rest of today includes flight data file reviews and meeting with spacesuit technicians. The commander and pilot also plan some landing practice runs in the Shuttle Training Aircraft.

Bedtime will be 12:45 a.m. EDT, as the crew shifts its wake/sleep cycle for the mission.

Touchdown. Shuttle Endeavour's crew has arrived at the launch site to prepare for Saturday evening's ascent into space.

The crew is over Central Florida now. They'll be landing at the Kennedy Space Center shortly.

The NASA jet with the astronauts is flying high over the Gulf of Mexico on this 900-mile trip.

Endeavour's crew has taken off from Houston, en route to the Kennedy Space Center for the start of final pre-flight preparations leading to Saturday's scheduled launch.

The astronauts are about to depart Ellington Field aboard a Gulfstream jet. Their arrival at Kennedy Space Center is expected around 1 p.m. EDT, an hour ahead of schedule.

Space shuttle Endeavour's astronauts are wrapping up final refresher training in Houston and preparing to travel back to Kennedy Space Center for Saturday evening's scheduled launch.

Commander Mark Polansky, pilot Doug Hurley, flight engineer Julie Payette, spacewalkers Chris Cassidy, Tom Marshburn and Dave Wolf, and station-bound astronaut Tim Kopra are scheduled to depart Ellington Field near the Johnson Space Center on Tuesday morning.

Arrival at the Florida spaceport's runway is expected around 2 p.m. EDT, and you can watch a live webcast right here on this page.

The astronauts returned home following last month's scrubs due to gaseous hydrogen leakage between the shuttle's external tank and the launch pad venting system. Thermal constraints with the space station's orbit prevented the mission from taking off over the past couple of weeks. But with that leak now fixed, as proved with a special fueling test last Wednesday, all systems now appear ready to go when the orbital launch window reopens Saturday.

The crew spent the past few weeks initially getting a break before restarting spacewalk and mission training to keep their skills sharp. They entered into pre-flight quarantine on Sunday, then spent Monday studying procedures and conducting launch rehearsals in the simulator, Polansky's tweeted on his Twitter page.

Range Safety testing and re-connection of Endeavour's ordnance systems were completed early Monday at launch pad 39A. Inside Firing Room 4 of the Launch Control Center, preps were underway to begin the formal three-day countdown sequence at 10 p.m. EDT Wednesday.

Liftoff of Endeavour remains targeted for 7:39 p.m. EDT Saturday to begin a 16-day construction flight that will finish assembling the Japanese segment of the International Space Station.

Sensors near a repaired hydrogen vent line attached to shuttle Endeavour's external tank detected only the slightest traces of free hydrogen during a critical fueling test today, officials said, clearing the way for another launch attempt July 11.

Read our full story.

Liquid oxygen tank has been placed in stable replenish. This completes the three-hour fuel loading process for space shuttle Endeavour.

Commander Mark Polansky tweeted on his Twitter page: "Watching the test on our external tank. So far, so good. If the results hold up, we'll be ready to try again on 11 July, 1939 EDT."

Once the liquid oxygen loading goes into stable replenish, the Final Inspection Team will be dispatched to the launch pad to give shuttle Endeavour's external tank a close-up examination. Draining of the propellants from the tank will start around 12 noon.

A post-test news conference is scheduled for 1 p.m. EDT today.

The liquid hydrogen loading went through the topping phase and has now reached the stable replenishment condition. Engineers have not detected any abnormal gaseous hydrogen leakage today, unlike the two previous attempts to launch shuttle Endeavour. It appears the repair efforts to overcome a slight misalignment between the external tank and venting system, which included a new seal and washer-like shims, are paying off.

No adverse gaseous hydrogen leakage has been seen in the ground umbilical carrier plate hardware, NASA commentator Candrea Thomas reports from the Firing Room.

The transition to topping mode for liquid hydrogen tank is beginning.

Loading of space shuttle Endeavour's external fuel tank continues at launch pad 39A. The big milestone coming up will be the transition of liquid hydrogen loading into the topping mode. That is when the vent valve is fully opened and the umbilical system completely chills, a point in which the gaseous hydrogen leak has occurred during past launch attempts. If the repairs have worked, the system will remain tight today.

NASA says the fueling operation is going well and that the liquid oxygen system is in fast-fill mode as well.

The liquid hydrogen loading has switched to the fast-fill mode.

This type of fueling test is a rarity for the space shuttle program. Over the history of the program, officials have sparingly ordered shuttles be loaded with a half-million gallons of cryogenics to check for leaks and examine the performance of hardware.

Today's test will determine if the new seal and shims meant to fix the leak in the gaseous hydrogen venting system have worked or not. The troublesome leak only appears when the system is in a supercold state as the external tank is filled, something that requires a full-up fueling process.

Engineers will have a good idea how well the vent system is working when the hydrogen tank gets about 98 percent full, which is when previous leaks have been discovered. That should happen around 9 a.m. EDT.

The liquid hydrogen loading has transitioned from the chilldown thermal conditioning sequence to the slow-fill mode.

The liquid oxygen system continues to be chilled.

Today's crucial test is now underway to see if the gaseous hydrogen leak between space shuttle Endeavour and the launch pad has been solved. The control team in Firing Room 4 started the three-hour fuel loading process at 6:53 a.m. EDT.

The Mission Management Team has given a "go" for fueling following its readiness meeting this morning.

Final preparations are underway at Kennedy Space Center's launch pad 39A and inside the Launch Control Center for this morning's fueling of space shuttle Endeavour. Retraction of the rotating service gantry was completed a little after midnight as the ground teams work through a countdown procedure toward this unique test.

Watch this page for live coverage of the fueling test beginning at 7 a.m. EDT. In addition to text updates, we will provide a video webcast as well.

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Engineers at the Kennedy Space Center are preparing to load the shuttle Endeavour's external tank with liquid oxygen and hydrogen rocket fuel early Wednesday in a critical test that could either pave the way to launch July 11 or trigger another lengthy delay.

Read our full story.

Engineers plan to load the shuttle Endeavour's external tank with rocket fuel next Wednesday to test vent line fixes intended to stop, or at least reduce, gaseous hydrogen leaks that grounded the shuttle June 13 and 17, NASA officials say. If the repairs work, the agency will press ahead with a third attempt to launch Endeavour on a space station assembly mission July 11.

Read our full story.

Shuttle managers plan to meet Wednesday to review procedures for a fueling test next week to assess the performance of an alternative internal seal and shim-like washers intended to eliminate a leak in a gaseous hydrogen vent line that has twice grounded the shuttle Endeavour.

Read our full story.

A very slight "clocking" misalignment in the way a hydrogen vent port flange on the shuttle Endeavour's external tank was riveted into the structure is the leading candidate for what caused gaseous hydrogen leaks that derailed two launch attempts June 13 and 17, the shuttle program manager says.

Read our full story.