NASA managers Thursday ordered another delay for launch of the shuttle Discovery, from early Friday morning to late Friday night, to give engineers additional time to make sure an 8-inch hydrogen valve in the orbiter's aft compartment will operate normally during fueling.

Read our full story.

The odds of acceptable weather during fueling is 60 percent and a similar outlook for liftoff time, shuttle launch director Pete Nickolenko says.

Retraction of the pad's service gantry back into the launch position will occur between 5 and 7 a.m. EDT and fueling would start at 2:34 p.m. EDT tomorrow, shuttle launch director Pete Nickolenko says.

The management team will recovene at 12 noon EDT tomorrow to finish up the discussions about the valve and give approval to begin fueling space shuttle Discovery for an 11:59 p.m. EDT liftoff.

Mission Management Team chairman Mike Moses, speaking at the news conference underway right now at Kennedy Space Center, says engineers needed to take another day to polish the rationale to go fly space shuttle Discovery as-is after the inboard liquid hydrogen valve issue seen during fueling on Tuesday. The extra 24 hours will allow everyone to "see it, bless it" before pressing ahead with a Friday night blastoff.

It was an indication that the valve didn't close properly when commanded to do so during the last countdown that caused the launch to be postponed. But testing of the valve, its position indicator instrumentation, as well as leak checks performed on shuttle Discovery last night all produced normal results.

Officials are finishing the review of test data and secondary ways to confirm the valve is working fine if a similar indication is seen on the next launch attempt.

The Ares test has been scrubbed for today due to a problem with the auxiliary power unit that enables the rocket's nozzle to be steered.

The space shuttle update news conference with Mission Management Team chairman Mike Moses and launch director Pete Nickolenko has been pushed back to 4:30 p.m. EDT.

There's no estimate yet on how long this delay in the test firing will last.

It appears to be a thrust vector control system issue that stopped the countdown.

Hold. Clock has stopped at T-minus 20 seconds.

T-minus 1 minute. The firing key has been turned on.

A readiness poll has been completed and all systems are "go" for the test at 15 minutes after the hour.

T-minus 9 minutes and counting to the Ares 1 test.

ATK says there will be a planned hold at T-minus 9 minutes, leading to the new ignition time for the Ares 1 solid rocket motor at 3:15 p.m. EDT.

Meanwhile, NASA is planning a shuttle Discovery launch status briefing from the Kennedy Space Center at 4 p.m. EDT.

The new targeted ignition time is 3:10 p.m. EDT. Arming cables are being installed.

Clocks have resumed in Utah for the solid rocket booster test.

The countdown to the Ares test is holding at T-minus 35 minutes to repair a water deluge valve.

With Discovery's launch postponed for today, attention now turns to Utah where rocket-maker ATK plans to conduct a ground-based test firing of the solid rocket motor that will form the first stage of NASA's Ares 1 vehicle. Live streaming video coverage of the event begins at 2:30 p.m. EDT and you can watch it on the right-hand side of this page. Ignition of the booster, which is a lengthened version of the space shuttle solid rocket, is targeted for 3 p.m. EDT.

SCRUB! Launch of space shuttle Discovery is being pushed back an additional 24 hours to give engineers more time to assess the fill and drain valve issue. The next launch opportunity would come at 11:59 p.m. EDT on Friday.

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The countdown resumed ticking at 8:57 a.m. EDT from the T-minus 11 hour mark, a point to which clocks were recycled following the last scrub.

Mission managers will convene their review of the fill and drain valve testing at 12 p.m., based on the latest revised game plan for today, then the count will enter the planned T-minus 6 hour hold at 1:57 p.m. EDT to await a "go" for fueling. Loading of Discovery's external fuel tank would start at 2:57 p.m. EDT, if all systems are deemed ready.

To help readers follow along with the voyage of Discovery, we have posted the latest ascent and flight plan charts.

The official launch window, based on the latest radar tracking of the space station's orbit and subsequent revision from Mission Control, extends from 12:19:13 a.m. to 12:27:09 a.m. EDT. The targeted liftoff time occurs inside the window at 12:22:09 a.m. EDT. That's the moment when Earth's rotation carries the launch pad into the plane of the station's orbit for a Flight Day 3 rendezvous.

An additional three minutes and 10 seconds in the form a second pane of the launch window exists until 12:30:19 a.m. EDT. However, launching within that pane would lead to a Flight Day 4 rendezvous and docking.

An 8-inch hydrogen valve and a suspect position sensor in the shuttle Discovery's engine compartment that appeared to malfunction during fueling Tuesday, forcing NASA to scrub an early Wednesday launch, performed normally during five open-close cycles Wednesday evening, officials said.

Read our full story.

Thursday's Mission Management Team meeting has been rescheduled for 1 p.m. EDT to decide whether to proceed with an evening countdown and launch.

Results from the five planned cycles indicate the inboard liquid hydrogen fill and drain valve opened and closed properly each time, a NASA spokesman says. The shuttle team will be continuing data-gathering tests into the night, including a volume decay check that could take a few hours.

The data will be presented to the Mission Management Team for evaluation at 12 noon EDT.

Launch remains targeted for Thursday night/Friday morning at 12:22 a.m. EDT.

Testing of the inboard liquid hydrogen fill and drain valve on space shuttle Discovery began at 6:28 p.m. EDT. Technicians plan to command the valve to open and close five times as part of testing to determine if the device is working properly or not.

Engineers believe instrumentation that indicates the valve's position could have caused the trouble that led to yesterday's scrub. If tonight's testing proves the valve is fine and the sensor is the problem, the Mission Management Team will meet at 12 noon EDT tomorrow and decide whether Discovery can be launched without any repairs being needed.

Engineers finished draining the shuttle Discovery's external tank Wednesday and geared up to remotely test a suspect valve in the orbiter's engine compartment to find out whether the shuttle can be launched "as is" early Friday or whether the flight might face a more significant delay, possibly to mid October.

Read our full story.

The current version of the NASA Television schedule, which is Revision B, can be viewed here.

Engineers plan to test a suspect hydrogen fill-and-drain valve aboard the shuttle Discovery late Wednesday to determine if the valve or a sensor system that measures its position is to blame for readings that forced NASA to call off the shuttle's countdown Tuesday, delaying launch from early Wednesday until Friday at the earliest.

Read our full story.

Launch of Discovery is targeted for no sooner than Thursday night/Friday morning at 12:22 a.m. EDT, if the technical issue that scrubbed tonight's attempt can be resolved.

During the countdown, the launch team didn't get the expected indication when the liquid hydrogen inboard fill and drain valve was commanded to closed. Space shuttle engineers believe the valve is operating properly and that faulty position indicator instrumentation could be to blame.

The post-scrub safing procedures are underway to inert the shuttle and run additional testing on the valve for determining if the theory is correct.

The briefing's start time has been pushed back to 10 p.m. EDT.

The post-scrub news conference is targeted for 9:30 p.m. EDT.

Trouble with a critical hydrogen fill-and-drain valve in the shuttle Discovery's aft engine compartment forced NASA managers to call off an attempt to launch the orbiter early Wednesday on a space station resupply mission. It was the second delay in a row for Discovery following a weather scrub earlier Tuesday.

Read our full story.

Discovery astronauts are tweeting on their Twitter pages about today's scrub. Jose Hernandez says: "Drats! 24 hour scrub! Won't launch until tomorrow! I guess I get to sleep one more night in a bed! More to come..."

Christer Fuglesang says: "Just got the news that we are scrubbing again, due to technical problem. Bad luck again, but maybe we can have dinner with the families."

Mission managers will be holding post-scrub meetings to assess the plan going forward. A news conference from the Kennedy Space Center is expected sometime later tonight.

SCRUB! Trouble with a liquid hydrogen fill and drain valve on the space shuttle Discovery has cancelled tonight's planned launch. How long it will take to fix this problem and reschedule the liftoff is not yet known.

A senior member of the launch team says it appears a scrub will be called.

Technicians are troubleshooting the situation to determine if this valve problem could be resolved without postponing the launch.

A problem has developed with a liquid hydrogen fill and drain valve inside space shuttle Discovery that has the potential of scrubbing tonight's launch attempt. The loading of fuel into the external tank has been stopped.

The current version of the NASA Television schedule, which is Revision A, can be viewed here.

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Loading of both liquid hydrogen and liquid oxygen have switched to the "fast-fill" mode as fueling of space shuttle Discovery proceeds via remote control at launch pad 39A.

There are two tanks inside the shuttle's external fuel tank. The liquid oxygen tank occupies the top third of the bullet-shaped tank. It will be filled with 143,000 gallons of liquid oxygen chilled to minus 298 degrees Fahrenheit. The liquid hydrogen tank is contained in the bottom two-thirds of the external tank. It holds 385,000 gallons of liquid hydrogen chilled to minus 423 degrees Fahrenheit.

No technical issues are being reported in the countdown for tonight's 1:10 a.m. EDT launch of Discovery.

Liquid oxygen loading has completed chilldown and gone into slow-fill.

The liquid hydrogen loading has transitioned from chilldown to the "slow-fill" mode. This fills a small fraction of the tank, then the loading switches to "fast-fill" mode.

Today's filling of space shuttle Discovery's external fuel tank started at 3:45 p.m. with the chilldown thermal conditioning process. This will be followed by the slow-fill mode and then the fast-fill mode to load the tank over the next three hours.

To help readers follow along with the voyage of Discovery, we have posted updated ascent and flight plan charts.

As the countdown resumes after the T-minus 6 hour hold, the launch team in Firing Room 4 is preparing to begin fueling the space shuttle.

Go for fueling! Mission managers have given their formal approval to proceed with tonight's launch attempt.

The astronauts woke up at 2:30 p.m. and were seated for breakfast at 3 p.m. EDT. They'll undergo final medial checks at 3:30 p.m., have some time to relax and then begin getting suited around 8:45 p.m. Departure from the crew quarters building for the launch pad is targeted for 9:20 p.m. EDT.

The latest briefing from the launch weather team indicates ideal conditions this afternoon for fueling space shuttle Discovery. Skies over pad 39A are clear, there's a light easterly wind and temperatures are in the mid-80s F.

The outlook for launch time continues to call for a 70 percent chance of acceptable conditions.

Countdown clocks are holding at the T-minus 6 hour mark. Following today's early morning scrub, the liquid hydrogen and liquid oxygen propellants were drained off the external tank and the pad reopened for limited work.

The Mission Management Team will gather for its pre-fueling tag up meeting at 3 p.m. EDT. If all systems are ready, the shuttle should be refueled starting at 3:45 p.m. EDT.

Hoping for some cooperation from the fickle Florida weather, Discovery is aiming for liftoff tonight at 1:10 a.m. EDT (0510 GMT) on the 30th space shuttle mission to the International Space Station.

Weather forecasters are predicting 70 percent chances of acceptable conditions for this afternoon's fueling operation and the late-night launch time. Here's the latest outlook from the 45th Weather Squadron:

"An upper level trough is located in the Eastern U.S. and a surface boundary is located over Central Florida. The boundary will migrate slowly northward as the upper level trough gradually weakens. There is still a possibility thunderstorms may affect the area near tanking time as the boundary moves north. By launch time, the boundary will be northwest of KSC. There is a chance of showers near the area at launch time.

"Our primary concerns for launch are cumulus clouds within 10 nautical miles of the launch pad and showers within 20 nautical miles of the Shuttle Landing Facility (SLF).

"Easterly flow will prevail the following two days increasing the chance for showers in the area near launch time. Also, a tropical wave near Puerto Rico may develop and impact seas for SRB recovery if the launch delays beyond Wednesday morning."

The odds of acceptable weather if tonight's launch is pushed back an additional 24 or 48 hours decrease to 60 and 40 percent, respectively.

Florida's hard-to-predict weather threw the shuttle Discovery's crew a curve ball early Tuesday, worsening when forecasters predicted improvement, generating unexpected lightning and offshore storms. While conditions improved as the morning wore on, the launch team ran out of time and NASA managers were forced to order a 24-hour delay.

Read our full story.

Commander Rick Sturckow has left the spacecraft, the final of the seven astronauts to egress following today's scrub.

Christer Fuglesang is the first of the astronauts to climb out of Discovery.

Discovery's hatch has been reopened.

The Orbiter Closeout Crew has arrived back at the launch pad to assist the astronauts off the shuttle.

Photos showing this morning's lightning and poor weather that scrubbed the launch can be seen here.

A formal cutoff of the countdown has occurred.

The official odds of acceptable launch weather tomorrow are 70 percent.

SCRUB! Stormy weather around the Kennedy Space Center will prevent space shuttle Discovery from blasting off on its mission to the International Space Station today. Launch director Pete Nickolenko has ordered a 24-hour postponement, setting up for a Wednesday morning liftoff at 1:10 a.m. EDT (0510 GMT).

The lightning rule is back green. But clouds and rain are still violating criteria.

Local weather remains "no go" both for launch and the emergency landing site at Kennedy Space Center.

NASA test director Charlie Blackwell-Thompson conducting readiness poll on whether the countdown can proceed toward launch.

There are no technical issues being worked that would delay launch. However, weather remains out of limits. The ceiling is no longer being violated but five other rules are red.

The Phase 2 lightning advisory is been reduced to the lower-level Phase 1 around KSC.

To recap, the current launch weather criteria being violated include those rules for anvil clouds, cumulus clouds, rain in the flight path, lightning and the field mills that measure the electrical potential in the air. The ceiling rule has gone red too.

Launch weather officer Kathy Winters says the storms in the area seem to be easing. But it's a question whether the conditions would improve fast enough for a launch today.

Here at the Kennedy Space Center Press Site, some stars are peeking through the clouds, while its still raining buckets at the launch pad three miles away.

The sky has opened up with a driving rain.

"It will be a close one tonight," ascent flight director Richard Jones says about the weather.

A heavy rain shower is dumping on the launch pad.

T-minus 9 minutes and holding. Countdown clocks have gone into the planned 45-minute, 4-second built-in hold. Launch is targeted for 1:36:04 a.m. EDT. Today's available window to get the shuttle off the ground extends just five minutes to 1:41:37 a.m. EDT.

Weather conditions remain "no go" at the current time and there doesn't seem to be much optimism. Clouds, rain and lightning concerns are violating several of the launch weather rules.

The Orbiter Closeout Crew is driving away from the pad.

The Main Propulsion System helium system is being reconfigured by pilot Kevin Ford. Soon the gaseous nitrogen purge to the aft skirts of the solid rocket boosters will be started.

Now one hour away from launch.

Mission Control in Houston is loading Discovery's onboard computers with the proper guidance parameters based on the projected launch time.

Pilot Kevin Ford is configuring the displays inside Discovery's cockpit for launch while commander Rick Sturckow enables the abort steering instrumentation.

The work to seal the shuttle's crew compartment hatch for flight is complete. And the closeout team that assisted the astronauts into Discovery this evening is preparing to leave the launch pad now.

T-minus 20 minutes and counting. The countdown has resumed after a 10-minute hold. Clocks will tick down for the next 11 minutes to T-minus 9 minutes where the final planned hold is scheduled to occur. The hold length will be adjusted to synch up with today's preferred launch time of 1:36:04 a.m.

Discovery's onboard computers are now transitioning to the Major Mode-101 program, the primary ascent software. Also, engineers are dumping the Primary Avionics Software System (PASS) onboard computers. The data that is dumped from each of PASS computers is compared to verify that the proper software is loaded aboard for launch.

T-minus 20 minutes and holding. The countdown has paused for a 10-minute built-in hold. Launch is scheduled for 1:36:04 a.m. EDT, weather permitting.

During this built-in hold, all computer programs in Firing Room 4 of the Complex 39 Launch Control Center will be verified to ensure that the proper programs are available for the countdown; the landing convoy status will be verified and the landing sites will be checked to support an abort landing during launch today; the Inertial Measurement Unit preflight alignment will be verified completed; and preparations are made to transition the orbiter onboard computers to Major Mode 101 upon coming out of the hold. This configures the computer memory to a terminal countdown configuration.

There's been a lightning strike about four miles from the launch pad.

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Commander Rick Sturckow is pressurizing the gaseous nitrogen system for Discovery's Orbital Maneuvering System engines and pilot Kevin Ford activated the gaseous nitrogen supply for the orbiter's Auxiliary Power Units' water spray boilers.

The targeted liftoff time is 1:36:04 a.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 1:31:29 to 1:41:37 a.m. EDT. Launching within that 10 minute period will enable Discovery to dock with the International Space Station on Tuesday night.

The weather situation is trending in the wrong direction. There's now five of launch weather rules being violated: anvil clouds, cumulus clouds, rain in the flight path, lightning and the field mills that measure the electrical potential in the air.

The ground pyro initiator controllers (PICs) are scheduled to be powered up around this time in the countdown. They are used to fire the solid rocket hold-down posts, liquid oxygen and liquid hydrogen tail service mast and external tank vent arm system pyros at liftoff and the space shuttle main engine hydrogen gas burn system prior to engine ignition.

The shuttle's two Master Events Controllers are being tested. They relay the commands from the shuttle's computers to ignite, and then separate the boosters and external tank during launch.

Mainline activation of the Ground Launch Sequencer has been completed. This is the master computer program that will run the final nine minutes of the countdown.

While NASA counts down to the flight of space shuttle Discovery, South Korea is planning to make its first orbital space shot at 4 a.m. EDT. See our preview story here.

The lightning advisory for the launch site has been stepped up to Phase 2.

A lightning strike has been detected six miles east of the launch pad. So the lightning rule for launch has gone red too, joining the flight thru precipitation and cumulus cloud rules as being "no go" for launch.

Discovery's hatch has been locked.

Just two hours remain until launch. But the official weather forecast is deteriorating. The odds for acceptable conditions at the planned 1:36 a.m. EDT liftoff time are falling from 80 percent to just 40 percent due to the clouds and rain in the area.

The orbiter closeout team at the launch pad is shutting Discovery's crew module hatch for flight.

The pad crew is ready to close up Discovery's hatch.

A Phase 1 lightning advisory has been issued for the Kennedy Space Center.

The astronauts are completing a series of radio communication checks with ground controllers.

T-minus 90 minutes and counting. Countdown clocks continue to tick down to T-minus 20 minutes where the next hold is planned. Activities remain on track for liftoff at 1:36 a.m., weather permitting.

The launch weather rules for flight through precipitation and cumulus clouds just went red.

Some weather to the southeast of the Kennedy Space Center and drifting this way is encroaching within the 20 nautical mile range around the launch site.

The final Discovery astronaut has boarded the shuttle today. Jose Hernandez, mission specialist No. 2 and flight engineer, has now entered the hatch. He will sit in the flight deck center seat, giving an extra set of eyes to aid the commander and pilot watch displays and switches during launch and landing.

The 47-year-old, born in Stockton, California, is the son of a Mexican migrant family who worked to harvest fruits and vegetables. He earned degrees in electrical engineering and worked at Lawrence Livermore National Laboratory and Johnson Space Center before becoming an astronaut. This will be his first spaceflight.

Read his biography here.

Retired Army colonel and helicopter pilot Pat Forrester has boarded the space shuttle tonight to be seated in the flight deck's aft-right seat and serve as mission specialist No. 1. He grew up in Springfield, Virginia, attended West Point and has flown in space twice before.

Read his biography here.

European Space Agency astronaut Christer Fuglesang, a particle physicist and avid sailor with one previous shuttle flight to his credit, is taking the center seat on the middeck for ascent. He'll be a spacewalker on this flight as mission specialist No. 4. The 52-year-old is a native of Stockholm, Sweden.

Read his biography here.

Three hours and counting until liftoff time. No significant technical issues are being worked in the countdown and all weather conditions are acceptable right now.

Danny Olivas, raised in El Paso, Texas, is mission specialist No. 3 and the lead spacewalker for the flight. The 43-year-old mechanical engineer was working at NASA's Jet Propulsion Laboratory when selected as an astronaut.

He will ride into orbit in the middeck's left seat.

Read his biography here.

Kevin Ford, a 49-year-old retired Air Force colonel from Montpelier, Indiana, will be Discovery's pilot. He was an F-15 pilot and an F-16 test pilot.

This spaceflight rookie is making his way to the flight deck's front-right seat right now.

Read Ford's biography here.

All of the launch rules are "go" at this time. There's still some weather cells popping up, but the current conditions around the Kennedy Space Center are acceptable for a launch.

Nicole Stott, the station-bound astronaut set to join the Expedition 20 crew living aboard the outpost, serves as Discovery's mission specialist No. 5 for the launch. The 46-year-old from Clearwater, Florida attended Embry-Riddle Aeronautical University before going to work as a structural design engineer at Pratt & Whitney. She then became a Kennedy Space Center worker on space shuttles and station hardware.

Once at the space station, she will exchange places with astronaut Tim Kopra, who then will return to Earth on the shuttle to conclude a month-and-a-half in space.

Stott just crawled through Discovery's hatch to take the right-hand seat on the middeck.

Read her biography here.

Shuttle commander Rick Sturckow, a 48-year-old Marine colonel who grew up on a ranch outside of San Diego, California, leads this voyage of Discovery. It will be his fourth spaceflight to the International Space Station, having been a pilot on STS-88 and -105 and commander on STS-117.

He is the first astronaut to board the shuttle this evening, taking the forward-left seat on the flight deck.

Read Sturckow's biography here.

Discovery's crew arrived atop launch pad 39A at 10:01 p.m. EDT. The AstroVan came to a stop on the pad surface near the Fixed Service Structure tower elevator that will take the seven-man crew to the 195-foot level to begin boarding the shuttle.

The AstroVan is passing the 52-story Vehicle Assembly Building where Discovery was attached to its external tank and solid rocket boosters and the adjacent Launch Control Center.

The Press Site is located across the street, and reporters went outside to watch the passing convoy. This is a launch day tradition to say farewell and good luck to the astronaut crews.

The rain has stopped and the concern about lightning has passed.

The crew of commander Rick Sturckow, pilot Kevin Ford, mission specialists Pat Forrester, Jose Hernandez, Danny Olivas, Christer Fuglesang and station-bound astronaut Nicole Stott just departed their quarters. The astronauts are boarding the AstroVan for the ride from the Industrial Area to launch pad 39A on the edge of the Atlantic Ocean.

The astronauts have emerged from the suitup room.

T-minus 3 hours and counting. The countdown clocks are ticking again after the planned two-and-a-half hour built-in hold. Clocks will proceed to T-minus 20 minutes when the next hold is scheduled. A final hold occurs at the T-minus 9 minute mark to synch up with the 1:36:04 a.m. EDT launch time.

It's starting to rain at the Kennedy Space Center again. At the present time, the current weather conditions are "no go" for launch due to lightning concerns, cumulus clouds and anvil clouds. Meteorologists continuously monitor the weather and update launch officials are rules go red and green. The outlook says the conditions will improve by launch time.

The Final Inspection Team reports a small piece of ice around the liquid hydrogen umbilical between the pad's service mast and the aft engine compartment of Discovery that is about 4.5 inches long and .25 inches thick. Ice in this area is not unusual.

The odds of weather being acceptable at the 1:36 a.m. EDT remain at 80 percent. Air Force meteorologists say the rain and clouds will continue to dissipate.

The astronauts are donning their day-glow orange launch and entry partial pressure spacesuits. After final adjustments and pressure checks, the astronauts will depart the suitup room and take the elevator down to the ground level of the Operations and Checkout Building to board the AstroVan for the trip to launch pad 39A around 9:46 p.m.

As predicted, the local weather in the Kennedy Space Center is clearing out.

Astronaut Jose Hernandez just tweeted on his Twitter page: "Folks this is my last tweet before I go into space! Will start to suit up in 30 minutes, listen to weather brief and head to the pad!"

The Final Inspection Team is out at the launch pad to scan the vehicle for any ice or debris concerns following fueling operations. The team is responsible for checking the shuttle and launch pad one last time prior to liftoff.

The team is comprised of engineers and safety officials from NASA, United Space Alliance and tank-builder Lockheed Martin. At the conclusion of their two-hour tour-of-duty, the team will have walked up and down the entire fixed service structure and mobile launcher platform.

The team is on the lookout for any abnormal ice or frost build-up on the vehicle and integrity of the external tank foam insulation.

The team uses a portable infrared scanner that gathers temperature measurements on the surface area of the shuttle and can spot leaks. The scanner will be used to obtain temperature data on the external tank, solid rocket boosters, space shuttle orbiter, main engines and launch pad structures. The scanner can also spot leaks of the cryogenic propellants, and due to its ability to detect distinct temperature differences, can spot any dangerous hydrogen fuel that is burning. The team member also is responsible for photo documentation.

The team wears the highly visible day-glow orange coveralls that are anti-static and flame resistant. Each member also has a self-contained emergency breathing unit that holds about 10 minutes of air.

Discovery astronaut Christer Fuglesang, having just finished lunch, tweeted on his Twitter page: "The burger was good. Bags have been packed. Last chess move from quarantine sent. Getting close :-)"

The astronauts had breakfast at 3:30 p.m. and then went for a run. They'll get suited up a little after 9 p.m., then depart crew quarters for the launch pad at 9:46 p.m. EDT.

The sun is setting as a light rain falls on the Kennedy Space Center.

The teams deployed out the pad are driving through the perimeter entrance now.

A rain shower is passing over the launch pad and giving Discovery a bath. Meteorologists expect all of this weather to clear out by launch time.

With weather conditions deemed safe and the hazardous tanking operation now completed, the Orbiter Closeout Crew and Final Inspection Team will head out to the pad to perform their jobs. The closeout crew will ready Discovery's crew module for the astronauts' ingress in a couple of hours; and the inspection team will give the entire vehicle a check for any ice formation following fueling.

TANK FULL. Liquid oxygen has entered stable replenishment mode, officially completing today's three-hour external tank filling process at 7:14 p.m. EDT.

T-minus 3 hours and holding. Clocks have entered a planned two-hour, 30 minute built-in hold. Launch remains scheduled for 1:36 a.m. EDT.

The continuity checks of the pyrotechnic initiator controllers in the firing chain circuitry have been accomplished.

Liquid hydrogen loading to 100 percent was completed at 6:48 p.m. The tank will be replenished through the rest of the countdown to replace the supercold propellant that naturally boils away.

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While the hydrogen is being topped off, the liquid oxygen tank is about 77 percent full.

No leakage is being seen around the ground umbilical carrier plate on the backside of shuttle Discovery's external tank as the liquid hydrogen system is topped off. It was during this point on previous shuttle missions in March and June that leaks developed. But a tight system is being reported today.

The liquid hydrogen tank has reached the 98 percent level and beginning the topping sequence.

Now passing the two-hour mark into this afternoon's fueling operations. No troubles have been reported by the launch team during tanking.

The cryogenics flow from storage spheres at the pad, through feed lines to the mobile launcher platform, into Discovery's aft compartment and finally into the external fuel tank.

The primary and secondary antennas at the MILA tracking station near the Kennedy Space Center have been aimed at the pad.

A lightning advisory is in effect at Kennedy Space Center. However, that does not prohibit fueling from continuing as planned. Discovery is shielded by the lightning protection system at pad 39A.

The Merritt Island tracking station, commonly known as MILA, is beginning to align its tracking antennas with the launch pad.

A current check of the launch weather rules shows the lightning and anvil cloud rules are "red" due to the approaching thunderstorms.

All is going well one-hour into the fueling operations for space shuttle Discovery.

The low-level sensors in the liquid hydrogen and liquid oxygen tanks have now reading "wet" as they get submerged by the cryogenics.

Liquid hydrogen loading switched to the "fast-fill" mode at 5:00 p.m. and liquid oxygen entered the same mode at 5:02 p.m. EDT as fueling of space shuttle Discovery proceeds via remote control at launch pad 39A.

There are two tanks inside the shuttle's external fuel tank. The liquid oxygen tank occupies the top third of the bullet-shaped tank. It will be filled with 143,000 gallons of liquid oxygen chilled to minus 298 degrees Fahrenheit. The liquid hydrogen tank is contained in the bottom two-thirds of the external tank. It holds 385,000 gallons of liquid hydrogen chilled to minus 423 degrees Fahrenheit.

Liquid oxygen loading has completed chilldown and gone into slow-fill.

The liquid hydrogen loading has transitioned from chilldown to the "slow-fill" mode. This fills a small fraction of the tank, then the loading switches to "fast-fill" mode.

Looking ahead to tonight's 1:36 a.m. EDT launch time, the weather forecast predicts an 80 percent chance of good conditions. The outlook includes a few low and some scattered high clouds, a slight chance of showers, launch pad winds from the southeast at 6 knots and a temperature of 79 degrees F.

FUELING BEGINS. Today's filling of space shuttle Discovery's external fuel tank has started with the chilldown thermal conditioning process. This will be followed by the slow-fill mode and then the fast-fill mode to load the tank over the next three hours.

The countdown has resumed ticking after the T-minus 6 hour hold. And right on time, launch director Pete Nickolenko has instructed his team to begin fueling the space shuttle.

NASA says there are no technical issues being worked in the countdown. The propulsion console in Firing Room 4 is going over the final steps to prepare for the start of fueling.

The Mission Management Team has given the "go" to fuel Discovery for today's launch. The weather situation is acceptable with proceeding into tanking.

The astronauts have been awakened in crew quarters for launch day. Jose Hernandez just tweeted on his Twitter page: "Only a few more hours and we'll be set to blast off into space! What a great feeling!"

The forecast for the first hour of fueling beginning at 4:11 p.m. EDT includes a few low and some scattered high clouds, inland thunderstorms, launch pad winds from the northeast at 8 peaking to 12 knots and a temperature of 85 degrees F. There is a 20 percent chance of lightning in the area.

In the pre-fueling weather update just given to mission managers, the outlook for this afternoon has a 20 percent chance of lightning within five nautical miles of the launch pad.

Countdown clocks are in the midst of the two-hour planned hold at T-minus 6 hours. This is the standard pause in the count prior to fueling operations. There's a 70 percent chance that weather will be acceptable for filling Discovery's external tank this afternoon, meteorologists say.

To help readers follow along with the voyage of Discovery, we have posted our countdown, ascent and flight plan charts.

The official launch window, based on the latest radar tracking of the space station's orbit and subsequent revision from Mission Control, extends from 1:31:03 a.m. to 1:41:04 a.m. EDT. The targeted liftoff time occurs in the middle of the window at 1:36:04 a.m. EDT. That's the moment when Earth's rotation carries the launch pad into the plane of the station's orbit.

If the launch is delayed to Wednesday morning for some reason, a two-pane window will be available for the backup liftoff opportunity. The first pane for a Flight Day 3 rendezvous with the space station would extend from 1:05:22 to 1:15:22 a.m. EDT and include a preferred launch time of 1:10:22 a.m. EDT.

An additional three minutes and 10 seconds in the form a second pane of Wednesday's launch window exists until 1:18:32 a.m. EDT. However, launching within that pane would lead to a Flight Day 4 rendezvous and docking.

Countdown clocks resumed ticking from the T-minus 11 hour mark at 9:11 a.m. EDT as planned. This morning's work includes activating Discovery's power-generating fuel cells and inertial measurement units, plus checking all of the switches in the cockpit to ensure they are in the correct positions for launch.

The count will proceed down to the T-minus 6 hour point where a two-hour hold begins at 2:11 p.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.

Space shuttle Discovery has been uncovered from the cocoon-like service gantry at launch pad 39A for the upcoming late-night liftoff. Ground technicians will spend the next few hours getting pad equipment configured and secured in preparation for the afternoon's fueling operation.

The Mission Management Team is scheduled to convene its pre-fueling meeting around 3 p.m. to review the status of work, the readiness of shuttle systems and the latest weather forecast.

If all goes according to plan, loading of the external tank with propellant will start at 4:11 p.m. EDT. The process should take three hours to complete.

Discovery's seven astronauts spent their past day studying flight plans, going to the beach house, visiting with spouses and checking out the shuttle at the pad.

The crew will be awakened for launch day at 3 p.m. They'll have breakfast at 3:30 p.m. and then undergo final medical exams at 4 p.m. Suit up begins a little after 9 p.m. and departure from crew quarters is scheduled for 9:46 p.m. in preparation for blastoff at 1:36 a.m. EDT.

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The pad 39A rotating service structure has begun retracting to reveal Discovery for launch.

NASA managers reviewed a few final technical issues Sunday and cleared Discovery for launch early Tuesday. The only issue going into the final hours of the countdown is the weather, with a 40 percent chance of afternoon thunderstorms Monday that could delay fueling.

Read our full story.

NASA's Mission Management Team met this afternoon and confirmed that all systems remain "go" for Tuesday's launch of the space shuttle Discovery.

"I'm really pleased to report that the launch countdown activities are proceeding nominally and we're working no issues," says Pete Nickolenko, the shuttle launch director.

Today's chores at launch pad 39A are focusing on 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 8 p.m. EDT. The built-in hold will last 13 hours and 11 minutes.

The giant gantry-like rotating service structure is scheduled for retraction from around Discovery at 5 a.m. tomorrow.

"We do have four launch attempts in five days," Nickolenko said. "Effectively, we have a window of opportunities between the 25th and the 30th of August. History tells us that we have a 96 percent chance of getting our launch off in those first four opportunities. So I'm confident that if for some reason weather delays us tomorrow that we'll still get off the ground sometime in the next couple of days."

Air Force weather forecasters are predicting a 60 percent chance of weather being within limits for Discovery's fueling operations Monday afternoon and an 80 percent chance of favorable conditions at the 1:36 a.m. EDT launch time.

"An upper level trough is deepening in the Eastern U.S. Southwest flow over Central Florida will cause convergence along the east coast with a late afternoon sea breeze, and the west coast sea breeze will also migrate toward the east coast causing late afternoon and evening thunderstorms," meteorologists reported today.

"Monday, the upper level trough will weaken allowing the ridge to move north over the Central Florida area. Surface winds will shift southeasterly and steering flow winds for convection southerly; therefore, afternoon storms should develop west of the launch pad along the sea breeze and migrate north. Upper level winds from the southwest will cause anvils to migrate toward the coast. Some storms may be close enough to cause lightning within 5 nautical miles near tanking time. Thunderstorms in the area should dissipate into the evening hours, and by launch time, there is a slight chance for showers in the area.

"Our primary concerns for launch are cumulus clouds within 10 nautical miles of the launch pad and showers within 20 nautical miles of the Shuttle Landing Facility.

"For Tuesday and Wednesday, the Bermuda High ridge will migrate north, and easterly flow will be prevalent. As the easterly flow persists, coastal showers will be the main concern for launch."

Liquid hydrogen and liquid oxygen reactants for space shuttle Discovery's electricity-generating fuel cells were loaded into storage spheres beneath payload bay last night as standard work continues at pad 39A for Tuesday's launch.

The cryogenics are combined by the three onboard fuel cells to produce power and a byproduct of drinking water during the shuttle's mission. Technicians pumped the reactants into small tanks on the orbiter during a multi-hour operation. The pad umbilical system used in the loading process will be demated and stowed this morning.

The Mission Management Team will hold its Launch Minus-2 Day meeting today to review the status of work and grant approval to continue with the countdown toward launch. A power controller replaced on Discovery will be a topic for managers to close for flight. A post-meeting news conference is planned for 3 p.m. EDT.

The astronauts, continuing to adjust into the overnight work hours for the mission, went sleep in crew quarters at 7 a.m. They'll be awakened at 3 p.m. EDT and tonight plan to receive orbiter, payload and weather status briefings.

After last-minute debate over external tank insulation, the shuttle Discovery is poised for launch early Tuesday on a three-spacewalk mission to deliver more than seven tons of supplies, experiment hardware and life-support gear to the International Space Station.

Check out the mission preview story.

The shuttle Discovery's countdown is proceeding smoothly through its initial hours with no technical problems of any significance, officials said Saturday. The weather remains unchanged, with forecasters calling for a 70 percent chance of acceptable conditions at launch time Tuesday.

Read our full story.

COUNT BEGINS. As you could see in our live streaming video from the Kennedy Space Center, countdown clocks just began ticking toward Tuesday morning's scheduled launch of the 30th space shuttle mission to the International Space Station.

The official countdown sequence began at 11 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 10:30 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 Discovery'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 Tuesday's targeted liftoff time of 1:36 a.m. EDT.

Engineers at the Kennedy Space Center geared up Friday for the 11 p.m. EDT start of the shuttle Discovery's countdown to launch Tuesday on a space station resupply mission. While some unplanned work will be carried into the countdown, engineers are optimistic and forecasters are predicting a 70 percent chance of good weather.

Read our full story.

The countdown for space shuttle Discovery's launch to the International Space Station will begin at 11 p.m. EDT tonight.

"Our systems are in good shape, the launch countdown preps are proceeding without much event," NASA Test Director Steve Payne said.

"The flight crew, vehicle and the launch team are ready to go, We're excited to pick up the launch countdown and looking forward to the early morning launch Tuesday morning."

Ground teams are wrapping up checks on the solid rocket booster hydraulics after a power unit was replaced, as well as retests following replacement of a wiring harness for one of the shuttle main engines.

The astronauts, currently asleep in the crew quarters building, will be awakened at 3 p.m. EDT today. Last night, they had a fit check of their orange launch and entry spacesuits and reviewed of the flight plans.

The early weather forecast for Tuesday's planned 1:36 a.m. EDT predicts an 70 percent chance of acceptable conditions at the Kennedy Space Center, Air Force meteorologists reported today.

"An upper level trough is moving into the Eastern U.S. causing the Bermuda high pressure ridge to migrate south of Kennedy Space Center. Southwest flow over Central Florida this weekend will cause convergence along the east coast with a late afternoon sea breeze, and the west coast sea breeze will also migrate toward the east coast each afternoon causing late afternoon and evening thunderstorms. Monday, the upper level trough will weaken allowing the ridge to move north over the Central Florida area. Although afternoon storms should be inland along the sea breeze, some storms may be close enough to cause lightning within 5 nautical miles near tanking time.

"Thunderstorms in the area should dissipate into the evening hours, and by launch time, there is a slight chance for showers in the area. Our primary concerns for launch are cumulus clouds within 10 nautical miles of the launch pad and showers within 20 nautical miles of the Shuttle Landing Facility (SLF).

"For Tuesday and Wednesday, the Bermuda High ridge will migrate north, and easterly flow will be prevalent. As the easterly flow persists, coastal showers will be the main concern for launch."

Shuttle Discovery's crew has arrived at the launch site to prepare for next Tuesday's middle-of-the-night blastoff to the International Space Station.

The six-man, one-woman team of astronauts flew from Houston to the Cape aboard a Gulfstream jet, landing at 6:30 p.m. EDT on the same runway Discovery will use to conclude the spaceflight.

"It's great to arrive in Florida for the launch of STS-128," commander Rick Sturckow told reporters just after arriving. "We've been studying and training hard for a just about a year now and we're ready to go accomplish this mission."

The crew also includes pilot Kevin Ford, mission specialists Jose Hernandez, Danny Olivas, Christer Fuglesang, Pat Forrester and station-bound astronaut Nicole Stott.

After making brief statements to reporters at the runway and posing for a photo opportunity, the crew was bussed away. Upcoming on their schedule over the next few hours, the commander and pilot will do some landing practice in the training aircraft.

Bedtime will be 7 a.m. EDT, as the crew continues shifting its wake/sleep cycle for the mission that will see most of the activities occur during the overnight hours U.S. time.

The aircraft has pulled to a stop and now the astronauts are filing off.

Touchdown. The astronauts just landed at the Kennedy Space Center.

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The crew over the Gulf of Mexico, nearing the west coast of Florida on this 900-mile trip. Reportes and photographers have gathered at the runway to cover the astronauts' arrival for launch.

Discovery's crew has left Houston for the two-hour plane ride over to the Cape. Touchdown at the spaceport is expected around 6:30 p.m. EDT.

The astronauts' travel plans have changed due to weather conditions. Instead of flying in T-38 jets, the crew will fly from Houston to the Kennedy Space Center aboard a Shuttle Training Aircraft. Arrival time has been moved up to 6:30 p.m. EDT.

As expected, senior NASA managers Wednesday formally cleared the shuttle Discovery for launch Tuesday on a space station resupply mission. While some engineers said they favored collecting additional data on the integrity of foam insulation on the shuttle's external tank - work that would trigger a lengthy launch delay - officials said no one objected to pressing ahead for launch at 1:36 a.m. EDT Aug. 25.

Read our full story.

"There was an excellent discussion on foam loss that included input from multiple teams including our NASA safety and engineering communities," said Bill Gerstenmaier, associate administrator for Space Operations at NASA Headquarters in Washington, who chaired the day and a half meeting. "After examining the foam releases on recent flights and completing a lot of testing and analysis to improve our understanding of the relative risks, we concluded that we're ready to go fly. The teams are continuing to learn about foam and have planned additional tests and analysis to continue to improve our understanding of foam loss mechanisms and risks."

You can watch the live NASA news briefing on the right-hand side of this page beginning at 11:30 a.m. EDT.

The Flight Readiness Review has formally set August 25 as the official launch date for space shuttle Discovery. The launch countdown will start at 11 p.m. EDT Friday, leading to next Tuesday's liftoff at 1:36 a.m. EDT.

A post-FRR press conference from Kennedy Space Center will begin shortly.

Meanwhile, Discovery's seven astronauts are scheduled to arrive at the Cape from Houston around 7:30 p.m. EDT today.

After a lengthy technical discussion, NASA managers decided Tuesday the shuttle Discovery's external tank can be safely flown as is, without the need for additional time-consuming inspections of its foam insulation, clearing the way for launch next week on a space station resupply mission.

Read our full story.

From inside the Flight Readiness Review, officials say space shuttle Discovery's external fuel tank has been cleared to launch. Some had suggested the shuttle be rolled back to the Vehicle Assembly Building and undergo additional foam tests.

The mission flight plan updated to reflect a possible launch on August 25 can be viewed here.

NASA won't be setting space shuttle Discovery's launch date today after all. The Flight Readiness Review will extend into Wednesday morning.

For now, liftoff will occur no sooner than August 25. The launch slipped from the earlier target of August 24 due to delays in pre-flight work at the pad.

The FRR continues at this hour. When the meeting will conclude is not clear. A press conference will follow, but the start time is TBD.

The Flight Readiness Review is underway at the Kennedy Space Center today as senior NASA managers gather to set the official launch date for space shuttle Discovery. A post-meeting news conference is planned for no sooner than 3 p.m. EDT (1900 GMT).

Today's review will examine presentations from the orbiter, external tank and solid rocket booster projects and the International Space Station program. Recent foam losses from the past two tanks will be a main topic for discussion and whether Discovery can be cleared for launch as is.

NASA is pressing ahead with preparations to launch the shuttle Discovery Aug. 24 on a space station resupply mission, but Program Manager John Shannon said today a final decision to proceed will depend on the results of last-minute testing this weekend to verify the integrity of external tank foam insulation.

Read our full story.

Read our earlier status center coverage.