Spaceflight Now


Follow space shuttle Endeavour's STS-127 mission to finish assembly of the International Space Station's Japanese segment. Reload this page for the latest updates.

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0405 GMT (12:05 a.m. EDT)
The astronauts spent a busy evening getting their orbital spacecraft configured for the mission. They began setting up the onboard computer network, downlinking imagery and data gathered during ascent, as well as powering up the shuttle's 50-foot-long robot arm for a post-launch checkout in preparation for its use in tomorrow's heat shield inspections. The crew got out of their launch and entry spacesuits, stowed away the mission specialists' seats and got some dinner as well. An eight-hour sleep period started at 12:03 a.m. EDT.
0210 GMT (10:10 p.m. EDT Wed.)
The latest version of the NASA Television schedule can be downloaded here.
0115 GMT (9:15 p.m. EDT Wed.)
See our launch story updated following the post-launch news conference.

A page of still images showing some of the debris events can been viewed here

0034 GMT (8:34 p.m. EDT Wed.)
"At about 107 seconds, we did see some debris events that appeared to impact the starboard chine area," CAPCOM Alan Poindexter just radioed commander Mark Polansky.

Poindexter also said those tile scuffs appear to be less severe than a similar impact on the last mission.

"Thanks for the information. I'm sure sure (you'll) get a chance to get a good look at that," Polansky replied.

"We are thrilled to be here."

0010 GMT (8:10 p.m. EDT Wed.)
Both 60-foot-long payload bay doors of shuttle Endeavour have been opened.

The shuttle's cargo hold is jam-packed on this mission. From forward to aft: the docking port occupies the front portion of the bay, followed by the Japanese science exposure facility that will be attached to the station during the mission, a smaller platform that ferries up some of the experiments for the station's new external porch and another carrier that houses spare parts to be transferred onto the station. In addition, two tiny deployable satellites are stowed on the starboard wall of the bay for release late in Endeavour's flight.

2350 GMT (7:50 p.m. EDT)
Gerstenmaier said engineers will be eager for imagery of areas toward the back end of Endeavour that could not been seen by the external tank camera during launch. That data will be collected during tomorrow's post-launch inspections and by high-resolution photography from the space station crew during rendezvous Friday.
2344 GMT (7:44 p.m. EDT)
Gerstenmaier says the aerodynamic sensitive time period in which debris could cause damage ends about T+plus 2 minutes and 15 seconds.

"With the earlier release (during flight), there is more delta velocity between the foam and the shuttle. So that could potentially cause more damage," Gerstenmaier says.

An approximate count of debris-shedding events from the external tank video shows about 14 events between T+plus 90 seconds and T+plus 2 minutes, 15 seconds. Two of those debris events can be seen hitting the shuttle tiles and scuffing off the black coating. Whether that is any concern for the heat shield is unclear.

"These look like little small streaks. With black tile, as soon as you scuff that top coat off it turns white, so it makes it look very dramatic," Mission Management Team chairman Mike Moses says.

"These look like individual small hits that just took the top coat off. It's very hard to tell the size and depth with just this camera."

2328 GMT (7:28 p.m. EDT)
Gerstenmaier said good lighting during today's launch will give engineers more detailed views of debris events during ascent. Inspections by the shuttle's robot arm boom extension and during the flip maneuver on final approach to the space station will give the best views of any damage, Gerstenmaier said.
2325 GMT (7:25 p.m. EDT)
"We had some foam loss events. There were several losses that occurred. There were probably a couple of orbiter hits (when flying through the lower atmosphere)," says Bill Gerstenmaier, NASA's associate administrator for space operations.
2255 GMT (6:55 p.m. EDT)
Running a month late because of hydrogen leaks and stormy weather, the shuttle Endeavour finally roared to life and blasted off Wednesday on its sixth try, rocketing away through a hazy sky toward a Friday rendezvous with the International Space Station. Multiple pieces of foam insulation appeared to fall from the ship's external tank during the early moments of flight, but it was not immediately clear whether the shuttle's fragile heat shield suffered any significant damage.

See our full story.

2243 GMT (6:43 p.m. EDT)
T+plus 40 minutes. The twin Orbital Maneuvering System engines on the tail of Endeavour have been fired successfully to propel the shuttle the rest of the way to orbit. The new orbit is targeted to have a high point of 142 miles and low point of 98 miles.
2239 GMT (6:39 p.m. EDT)
T+plus 37 minutes. In fact, there's perhaps upwards of a dozen debris events. A picture showing one of the debris events can be seen here.
2239 GMT (6:39 p.m. EDT)
T+plus 37 minutes. Endeavour in the proper orientation for the upcoming maneuvering burn.
2234 GMT (6:34 p.m. EDT)
T+plus 31 minutes. Upon further examination of the launch video, there's also a debris event at T+plus 1 minute, 43 seconds. Where that debris went and where it hit the vehicle is not clear.
2233 GMT (6:33 p.m. EDT)
T+plus 30 minutes. The two flapper doors on the belly of Endeavour are being swung closed to shield the umbilicals that had connected to the external fuel tank.
2219 GMT (6:19 p.m. EDT)
T+plus 16 minutes. The three Auxiliary Power Units are being shut down as planned.
2215 GMT (6:15 p.m. EDT)
T+plus 12 minutes. A cloud of small debris pieces can be seen hitting the underside heat shield tiles at T+plus 1 minute, 46 seconds.
2212 GMT (6:12 p.m. EDT)
T+plus 9 minutes, 30 seconds. The video camera mounted to Endeavour's external tank showed debris falling away during launch and some tiles appear to be slightly damaged.
2212 GMT (6:12 p.m. EDT)
T+plus 9 minutes, 18 seconds. It was a nominal MECO. A quick boost from the Orbital Maneuvering System engines is not required to reach the planned preliminary sub-orbital trajectory.
2211 GMT (6:11 p.m. EDT)
T+plus 8 minutes, 47 seconds. The emptied external tank has been jettisoned from the belly of space shuttle Endeavour. The tank will fall back into the atmosphere where it will burn up harmlessly.
2211 GMT (6:11 p.m. EDT)
T+plus 8 minutes, 31 seconds. MECO. Main Engine Cutoff confirmed! Endeavour has arrived in orbit for its construction flight to build a front porch on the International Space Station where external science research can be performed.
2210 GMT (6:10 p.m. EDT)
T+plus 7 minutes, 40 seconds. The main engines are beginning to throttle down to ensure the shuttle does not experience forces greater than 3 g's as it continues to accelerate prior to engine shutdown.
2210 GMT (6:10 p.m. EDT)
T+plus 7 minutes, 70 seconds. Endeavour is more than 600 miles downrange, traveling at 12,700 mph.
2210 GMT (6:10 p.m. EDT)
T+plus 7 minutes, 5 seconds. Single engine press 104. The shuttle can reach orbit on the power from a single main engine should two fail at this point. But all three continue to fire properly.
2209 GMT (6:09 p.m. EDT)
T+plus 6 minutes, 25 seconds. "Press to MECO" Endeavour can now achieve a safe orbit on two engines. All three remain in good shape.
2209 GMT (6:09 p.m. EDT)
T+plus 6 minutes. The shuttle has started rolling to a heads-up position to improve communications with the TDRS satellite network.
2208 GMT (6:08 p.m. EDT)
T+plus 5 minutes, 15 seconds. "Press to ATO". Endeavour can reach an orbit, albeit a low orbit, on two engines should one shut down now. But all three powerplants are still running just fine.
2207 GMT (6:07 p.m. EDT)
T+plus 4 minutes, 30 seconds. Endeavour will be tripling its speed in the next four minutes to reach orbital velocity of 17,500 mph.
2207 GMT (6:07 p.m. EDT)
T+plus 4 minutes. Negative return. The shuttle has passed the point where Endeavour could turn around and make an emergency landing at Kennedy Space Center in the event of a main engine problem. Landing sites in France and Spain are now available to Endeavour in the unlikely event an abort occurs during the remainder of today's launch.
2206 GMT (6:06 p.m. EDT)
T+plus 3 minutes, 45 seconds. Endeavour is is 56 miles in altitude, 120 miles downrange from the launch pad.
2206 GMT (6:06 p.m. EDT)
T+plus 3 minutes, 20 seconds. Endeavour is traveling at 4,000 mph.
2206 GMT (6:06 p.m. EDT)
T+plus 3 minutes. Overseeing today's climb to orbit from the Mission Control Center in Houston will be ascent flight director Bryan Lunney, son of legendary Apollo flight director Glynn Lunney. Seated alongside in Houston in direct radio contact with the shuttle crew will be CAPCOM astronaut Alan Poindexter, the upcoming commander of the STS-131 shuttle mission next year.
2205 GMT (6:05 p.m. EDT)
T+plus 2 minutes, 45 seconds. Commander Mark Polansky just received the "Two-engine Moron" call from CAPCOM Alan Poindexter in Mission Control. The call means Endeavour can now reach a Transatlantic Abort Landing site if one main engine fails. However, all three engines continue to burn normally.
2205 GMT (6:05 p.m. EDT)
T+plus 2 minutes, 20 seconds. Guidance is converging as programmed. Endeavour's engine nozzles are swiveling to steer the ship toward a precise point for main engine cutoff about six minutes from now.
2205 GMT (6:05 p.m. EDT)
T+plus 2 minutes, 10 seconds. Mission Control confirms a good jettison of the solid rocket boosters has occurred. The spent boosters will parachute into the Atlantic Ocean for retrieval. Endeavour continues its streak toward space on the power generated by the three liquid-fueled main engines.
2204 GMT (6:04 p.m. EDT)
T+plus 90 seconds. The space shuttle now weighs just half of what it did at liftoff. The solid rocket boosters are burning 11,000 pounds of propellant every second. The main engines are guzzling a half-ton of liquid fuel per second from the external tank.
2204 GMT (6:04 p.m. EDT)
T+plus 65 seconds. Endeavour's three main engines have revved back up to their 104 percent power setting. And Mission Control has given the "go at throttle up" call.
2204 GMT (6:04 p.m. EDT)
T+plus 60 seconds. Endeavour's thunderous departure from the Kennedy Space Center begins an action-packed mission with five planned spacewalks and delicate maneuvers by three different robot arms. The shuttle will reach the space station on Monday for rendezvous and docking.
2203 GMT (6:03 p.m. EDT)
T+plus 35 seconds. Endeavour's three liquid-fueled main engines are throttling down to their 72 percent power setting to ease the strain on the vehicle during passage through the region of maximum aerodynamic stresses.
2203 GMT (6:03 p.m. EDT)
T+plus 15 seconds. Houston has assumed control of Endeavour's marathon 16-day mission. The space shuttle cleared the tower and now is rolling on course to target the space station's orbit.
2203:10 GMT (6:03:10 p.m. EDT)
T-minus 10 seconds, go for ignition of the space shuttle main engines, 5, 4, 3, 2, 1 and LIFTOFF! Liftoff of shuttle Endeavour and its construction crew on a mission to finish building Japan's Kibo science facility at the International Space Station!
2202:41 GMT (6:02:41 p.m. EDT)
T-minus 31 seconds. AUTO SEQUENCE START! The handoff has occurred from the Ground Launch Sequencer to the space shuttle. Endeavour's computers now controlling.

In the next few seconds, the solid rocket booster hydraulic steering system will be started, the orbiter's body flap and speed brake moved to their launch positions, the firing chain armed. Main engine ignition begins at T-minus 6.6 seconds.

2202:10 GMT (6:02:10 p.m. EDT)
T-minus 1 minute. Computers are verifying that the main engines are ready for ignition. Sound suppression water system is armed. The system will activate at T-minus 16 seconds to suppress the sound produced at launch. And the residual hydrogen burn ignitors are armed. They will be fired at T-minus 10 seconds to burn off hydrogen gas from beneath the main engine nozzles.

Shortly, the external tank strut heaters will be turned off; Endeavour will transition to internal power; the liquid oxygen and liquid hydrogen outboard fill and drain valves will be closed; the payload bay vent doors will be positioned for the launch; and the gaseous oxygen vent arm will be verified fully retracted.

2201:40 GMT (6:01:40 p.m. EDT)
Now 90 seconds from launch. All remains "go" with Endeavour on this sixth try at launching the STS-127 mission.

The shuttle is carrying up the external science deck and experiments for Japan's Kibo facility, spare parts for the station in the form of a replacement thermal control system pump, a drive unit for the railcar and a six-foot-diameter Ku-band communications dish, plus six fresh batteries to swap out those on the Port 6 solar power module that's nearing nine years old already.

2201:10 GMT (6:01:10 p.m. EDT)
T-minus 2 minutes. The astronauts are being instructed to close and lock the visors on their launch and entry helmets.

At T-minus 1 minute, 57 seconds the replenishment to the flight load of liquid hydrogen in the external tank will be terminated and tank pressurization will begin.

2200:40 GMT (6:00:40 p.m. EDT)
T-minus 2 minutes, 30 seconds. The external tank liquid oxygen vent valve has been closed and pressurization of the LOX tank has started.

Endeavour's power-producing fuel cells are transfering to internal reactants. The units will begin providing all electricity for the mission beginning at T-50 seconds.

And pilot Doug Hurley has been asked to clear the caution and warning memory system aboard Endeavour. He will verify no unexpected errors in the system.

In the next few seconds, the gaseous oxygen vent hood will be removed from atop the external tank. Verification that the swing arm is fully retracted will be made by the ground launch sequencer at the T-minus 37 second mark.

2200:10 GMT (6:00:10 p.m. EDT)
T-minus 3 minutes. Orbiter steering check is now complete; the main engine nozzles are in their start positions.
2159:40 GMT (5:59:40 p.m. EDT)
T-minus 3 minutes, 30 seconds. The main engine nozzles now being moved through a computer controlled test pattern to demonstrate their readiness to support guidance control during launch today.
2159:10 GMT (5:59:10 p.m. EDT)
T-minus 4 minutes. Activation of the APUs is complete. The three units are up and running normally.

And the final helium purge sequence is underway in the main propulsion system. This procedure readies fuel system valves for engine start. In the next few seconds, the aerosurfaces of Endeavour will be run through a pre-planned mobility test to ensure readiness for launch. This is also a dress rehearsal for flight of the orbiter's hydraulic systems.

2158:10 GMT (5:58:10 p.m. EDT)
T-minus 5 minutes. The "go" has been given for for Auxiliary Power Unit start. Pilot Doug Hurley is now flipping three switches in Endeavour's cockpit to start each of the three APU's. The units, located in the aft compartment of Endeavour, provide the pressure needed to power the hydraulic systems of the shuttle. The units will be used during the launch and landing phases of the mission for such events as moving the orbiter's aerosurfaces, gimbaling the main engine nozzles and deploying the landing gear.

Over the course of the next minute, the orbiter's heaters will be configured for launch by commander Mark Polansky, the fuel valve heaters on the main engines will be turned off in preparation for engine ignition at T-6.6 seconds and the external tank and solid rocket booster safe and arm devices will be armed.

2157:40 GMT (5:57:40 p.m. EDT)
T-minus 5 minutes, 30 seconds. APU pre-start is complete and the units are ready for activation. The orbiters flight data recorders have gone into the record mode to collect measurements of shuttle systems performance during flight.
2157:10 GMT (5:57:10 p.m. EDT)
T-minus 6 minutes. Pilot Doug Hurley has been asked by the orbiter test conductor to pre-start the orbiter Auxiliary Power Units. This procedure readies the three APU's for their activation after the countdown passes T-minus 5 minutes.
2155:40 GMT (5:55:40 p.m. EDT)
T-minus 7 minutes, 30 seconds. The Ground Launch Sequencer has started pulling the orbiter access arm away from the crew hatch on the port side of the vehicle. The arm was the passage way for the astronauts to board Endeavour a few hours ago. The arm can be re-extended very quickly should the need arise later in the countdown.
2155:10 GMT (5:55:10 p.m. EDT)
T-minus 8 minutes and counting. Pilot Doug Hurley has flipped the switches in the cockpit of Endeavour to directly connect the three onboard fuel cells with the essential power buses. Also, the stored program commands have been issued to the orbiter for antenna alignment and management during launch.
2154:10 GMT (5:54:10 p.m. EDT)
T-minus 9 minutes and counting! The Ground Launch Sequencer has been initiated. The computer program is located in a console in the Firing Room of the Complex 39 Launch Control Center. The GLS is the master of events through liftoff. During the last 9 minutes of the countdown, the computer will monitor as many as a thousand different systems and measurements to ensure that they do not fall out of any pre-determine red-line limits. At T-minus 31 seconds, the GLS will hand off to the onboard computers of Endeavour to complete their own automatic sequence of events through the final half minute of the countdown.
2153:10 GMT (5:53:10 p.m. EDT)
Now 10 minutes from blastoff.
2152:10 GMT (5:52:10 p.m. EDT)
The countdown will resume from the T-minus 9 minute mark at 5:54:10 p.m. EDT.
2150 GMT (5:50 p.m. EDT)
NASA launch director Pete Nickolenko has conducted his poll and given approval to resume the countdown for liftoff at 6:03 p.m. EDT!
2149 GMT (5:49 p.m. EDT)
The poll by NASA test director Steve Payne confirms there are no technical issues or constraints standing in the way of launch at 6:03 p.m. EDT. The Range also reports "go" on the local weather. And Mission Control says that weather at abort landing sites is acceptable, too.
2146 GMT (5:46 p.m. EDT)
The local 45th Weather Squadron is responsible for launch forecasting. All of the launch commit criteria weather rules are "go."
2145 GMT (5:45 p.m. EDT)
The Spaceflight Meteorology Group based in Houston, which is the group that handles weather at the shuttle landing sites, confirms conditions are observed and forecast "go" at the Kennedy Space Center for Return to Launch Site (RTLS).
2144 GMT (5:44 p.m. EDT)
Ten minutes are remaining in this built-in hold. Final readiness polls will be conducted over the next few minutes.
2140 GMT (5:40 p.m. EDT)
Launch weather officer Kathy Winters says there's now less than a 10 percent chance of conditions preventing today's liftoff.
2138 GMT (5:38 p.m. EDT)
Now 25 minutes from Endeavour's launch on an eight-and-a-half minute trek to space. At main engine cutoff, Endeavour will be flying on a suborbital trajectory with a high point of 138 statute miles and low point of 36 statute miles, inclined 51.6 degrees to the equator. A half-hour later, the twin orbital maneuvering engines will be fired to place the shuttle into a 142 by 98 statute mile orbit.
2134 GMT (5:34 p.m. EDT)
Mission Management Team chairman Mike Moses is performing a readiness poll of his advisory panel. He will pass his "go" status to launch director Pete Nickolenko.
2131 GMT (5:31 p.m. EDT)
All green across the weather rule board. Conditions are within limits for a launch today.
2130 GMT (5:30 p.m. EDT)
Powering space shuttle Endeavour throughout its eight-and-a-half minute climb to orbit will be the three main engines built by Pratt & Whitney Rocketdyne. The cryogenic powerplants are fed with liquid hydrogen and liquid oxygen stored in the external fuel tank.

In the engine No. 1 position today is the Block 2-2045 engine now making its 10th launch. It has accumulated 5,485 seconds of total firing time on the previous missions, plus ground testing. STS-89 was its debut flight.

Making its first launch is the new Block 2-2060 in the engine No. 2 position. This powerplant has 1,420 seconds of ground test time.

And Block 2-2054 is engine No. 3 on Endeavour. It has eight previous flights, starting with STS-101, and some 5,123 seconds of firing time.

2125 GMT (5:25 p.m. EDT)
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2120 GMT (5:20 p.m. EDT)
At launch, the space station will be flying 220 miles above the central Pacific Ocean at 40.4 degrees South and 14.3 degrees West. Liftoff at 6:03:10 p.m. EDT is timed to place Endeavour on course to dock with the station Friday.
2116 GMT (5:16 p.m. EDT)
The official odds of acceptable weather at launch time have improved from 60 percent to 80 percent.
2109 GMT (5:09 p.m. EDT)
T-minus 9 minutes and holding. Countdown clocks have gone into the planned 45-minute, 24-second built-in hold. Launch is targeted for 6:03:10 p.m. EDT. Today's available window to get the shuttle off the ground extends just five minutes to 6:08:10 p.m. EDT.

Current weather conditions are "go" right now. Fingers are crossed!

2103 GMT (5:03 p.m. EDT)
Now one hour away from launch.

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

2102 GMT (5:02 p.m. EDT)
Mission Control in Houston is loading Endeavour's onboard computers with the proper guidance parameters based on the projected launch time.
2101 GMT (5:01 p.m. EDT)
Pilot Doug Hurley is configuring the displays inside Endeavour's cockpit for launch while commander Mark Polansky enables the abort steering instrumentation.
2058 GMT (4:58 p.m. EDT)
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 6:03:10 p.m.

Endeavour'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.

2053 GMT (4:53 p.m. EDT)
There are no technical issues being worked in the countdown. Weather is the only worry for this sixth attempt to launch space shuttle Endeavour.
2048 GMT (4:48 p.m. EDT)
T-minus 20 minutes and holding. The countdown has paused for a 10-minute built-in hold. Launch is scheduled for 6:03:10 p.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.

2035 GMT (4:35 p.m. EDT)
The anvil cloud rule is no longer being violated. So all launch commit criteria weather rules are "go" at this time.
2033 GMT (4:33 p.m. EDT)
Commander Mark Polansky is pressurizing the gaseous nitrogen system for Endeavour's Orbital Maneuvering System engines and pilot Doug Hurley activated the gaseous nitrogen supply for the orbiter's Auxiliary Power Units' water spray boilers.
2030 GMT (4:30 p.m. EDT)
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.

2025 GMT (4:25 p.m. EDT)
Chief NASA astronaut Steve Lindsey just took off aboard the Shuttle Training Aircraft to fly weather reconnaissance around the Kennedy Space Center. He's been asked to go take a look at a low pressure area to the northeast over the Atlantic. Clouds appear to be streaming toward the coast from that system.
2021 GMT (4:21 p.m. EDT)
The work to seal the shuttle's crew compartment hatch for flight is complete. And the closeout team that assisted the astronauts into Endeavour this afternoon is preparing to leave the launch pad now.
2020 GMT (4:20 p.m. EDT)
The targeted liftoff time is 6:03:10 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 5:58 to 6:08 p.m. EDT. Launching within that 10 minute period will enable Endeavour to dock with the International Space Station on Wednesday.

2016 GMT (4:16 p.m. EDT)
The field mill, lightning and cumulus cloud rules are no longer being violated. But the anvil cloud rule remains red.
2003 GMT (4:03 p.m. EDT)
Just two hours remain until the planned liftoff time. Four of the weather rules remain "no go."

The reusable solid rocket boosters, built by ATK, provide the primary thrust to propel the space shuttle away from Earth during the initial two minutes of flight. The 11 sections on each booster flying on Endeavour are a mixture of brand new and used hardware. The upper dome on the right-hand booster, for example, flew on STS-2 in 1981. In all, the twin boosters flying this morning have refurbished segments and pieces that trace back to 65 previous shuttle launches.

The boosters will parachute into the Atlantic Ocean where a pair of retrieval ships are standing by to recover the rockets and tow them back to shore, beginning again the process to disassemble, refurbish and reuse the hardware in the future.

1955 GMT (3:55 p.m. EDT)
A reminder that if you will be away from your computer but would like to receive countdown updates, sign up for our Twitter feed to get text messages on your cellphone. U.S. readers can also sign up from their phone by texting "follow spaceflightnow" to 40404. (Standard text messaging charges apply.)
1948 GMT (3:48 p.m. EDT)
The orbiter closeout team at the launch pad is shutting Endeavour's crew module hatch for flight.
1942 GMT (3:42 p.m. EDT)
The astronauts have completed a series of radio communication checks with ground controllers.
1938 GMT (3:38 p.m. EDT)
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 6:03 p.m., weather permitting.
1930 GMT (3:30 p.m. EDT)
The current weather conditions are "no go" for the field mill, lightning, anvil and cumulus cloud rules.
1921 GMT (3:21 p.m. EDT)
The final Endeavour astronaut has boarded the shuttle today. Julie Payette, mission specialist No. 2 and flight engineer, has now entered the hatch. She 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 45-year-old from Montreal, Quebec is a Canadian Space Agency astronaut. She visited the International Space Station once before in 1999.

Read her biography here.

1908 GMT (3:08 p.m. EDT)
Astronaut Dave Wolf, a veteran of three previous spaceflights ranging from a Spacelab mission, a four-month stint working aboard the Russian space station Mir and an earlier assembly flight to the International Space Station is the lead spacewalker on Endeavour. The 52-year-old medical doctor from Indianapolis is mission specialist No. 4.

Wolf will take the center seat on the middeck for ascent.

Read his biography here.

1906 GMT (3:06 p.m. EDT)
A Navy SEAL is climbing into space shuttle Endeavour's flight deck aft-right seat. Chris Cassidy, 39-year-old from Maine and spaceflight rookie is mission specialist No. 1. He will be one of the spacewalkers on the flight.

Read his biography here.

1903 GMT (3:03 p.m. EDT)
Three hours and counting until liftoff time.

Another Phase 2 lightning advisory is being issued for the Complex 39 area.

1850 GMT (2:50 p.m. EDT)
Tom Marshburn, a 48-year-old former emergency doctor and NASA flight surgeon born in North Carolina, is mission specialist No. 3 and another of the spacewalkers during Endeavour's trip to the station.

He will ride into space for the first time of his career in the middeck's left seat.

Read his biography here.

1848 GMT (2:48 p.m. EDT)
Doug Hurley, a 42-year-old lieutenant colonel in the Marine Corps born in New York, will be Endeavour's pilot. He has over 3,200 hours in more than 20 different kinds of aircraft, including being the first ever Marine pilot to fly the F/A-18 E/F Super Hornet.

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

Read Hurley's biography here.

1837 GMT (2:37 p.m. EDT)
Tim Kopra, the station-bound astronaut set to join the Expedition 20 crew living aboard the outpost, serves as Endeavour's mission specialist No. 5 for the launch. The 45-year-old from Austin, Texas is a colonel in the U.S. Army. Once at the space station, he will exchange places with Japanese astronaut Koichi Wakata, who then will return to Earth on the shuttle to conclude three-and-a-half months in space.

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

Read his biography here.

1836 GMT (2:36 p.m. EDT)
Shuttle commander Mark Polansky, a 53-year-old aviator born in New Jersey, leads this voyage of Endeavour. It will be his third spaceflight, having been a pilot and a commander on two previous construction missions to the space station in 2001 and 2006.

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

Read Polansky's biography here.

1831 GMT (2:31 p.m. EDT)
The Final Inspection Team has completed its work at the launch pad and is now preparing to depart. The team will present its report to managers in the control center in a little while.
1828 GMT (2:28 p.m. EDT)
Endeavour's crew arrived atop launch pad 39A at 2:28 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.
1825 GMT (2:25 p.m. EDT)
The disturbed weather and flight through precipitation rules are no longer being violated. Conditions are beginning to improve as the sea breeze starts pushing westward. The field mill, lightning and cumulus cloud rules remain "no go."
1822 GMT (2:22 p.m. EDT)
The AstroVan is passing the 52-story Vehicle Assembly Building where Endeavour 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 at the passing convoy. This is a launch day tradition to say farewell and good luck to the astronaut crews.

But the press crowd for this sixth launch attempt is remarkably small today.

1812 GMT (2:12 p.m. EDT)
The astronauts are boarding the AstroVan for the ride from the Industrial Area to launch pad 39A on the edge of the Atlantic Ocean. Commander Mark Polansky, pilot Doug Hurley, flight engineer Julie Payette, spacewalkers Chris Cassidy, Tom Marshburn and Dave Wolf, and station-bound astronaut Tim Kopra emerged from crew quarters at 2:12 p.m. EDT.
1808 GMT (2:08 p.m. EDT)
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 6:03:10 p.m. EDT launch time.
1800 GMT (2:00 p.m. EDT)
A Phase 2 lightning advisory is about to be discontinued. The wet weather will not prevent the astronauts from departing crew quarters as scheduled in about 15 minutes.
1749 GMT (1:49 p.m. EDT)
The astronauts just finished getting suited up again in 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 2:13 p.m.
1741 GMT (1:41 p.m. EDT)
A heavy rain advisory has been issued meaning there's a chance for greater than one-inch of rain per hour.
1740 GMT (1:40 p.m. EDT)
It's now a downpour at launch pad 39A. Forecasters hope as the afternoon goes along that the sea breeze will push the storms inland.
1735 GMT (1:35 p.m. EDT)
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1735 GMT (1:35 p.m. EDT)
There's also a wind advisory in effect.
1727 GMT (1:27 p.m. EDT)
A Phase 2 lightning advisory was just issued for the Complex 39 area.
1718 GMT (1:18 p.m. EDT)
The flight through precipitation and disturbed weather rules have gone red.
1715 GMT (1:15 p.m. EDT)
The storm over the launch site has cloud tops at 33,000 feet. But there is no lightning in this particular cell.
1711 GMT (1:11 p.m. EDT)
A rain shower is passing over the launch pad.
1709 GMT (1:09 p.m. EDT)
The launch weather rule for the field mill network around the Cape for measuring the electrical potential in the air has gone red now, too.
1700 GMT (1:00 p.m. EDT)
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.

1645 GMT (12:45 p.m. EDT)
The countdown entered the T-minus 3 hour hold at 11:38 a.m. EDT. This planned built-in pause will last two-and-a-half hours. Clocks should resume ticking at 2:08 p.m., followed five minutes later by the astronauts departing crew quarters.
1645 GMT (12:45 p.m. EDT)
At the present time, the current weather conditions are "no go" for launch due to lightning concerns and cumulus clouds. Meteorologists continuously monitor the weather and update launch officials are rules go red and green.
1630 GMT (12:30 p.m. EDT)
The astronauts had lunch at 11:30 a.m. They'll get suited up at 1:30 p.m., then depart crew quarters for the launch pad at 2:13 p.m. EDT.
1600 GMT (12:00 p.m. EDT)
With the hazardous tanking operation completed, the Orbiter Closeout Crew and Final Inspection Team will head out to the pad to perform their jobs. The closeout crew will ready Endeavour'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.
1541 GMT (11:41 a.m. EDT)
Liquid oxygen has entered stable replenishment mode, officially completing today's three-hour external tank filling process at 11:39 a.m. EDT.
1533 GMT (11:33 a.m. EDT)
Topping of the liquid oxygen tank is underway now.
1525 GMT (11:25 a.m. EDT)
From the 45th Weather Squadron earlier this morning, here's the outlook:

"The Bermuda ridge is located just south of Kennedy Space Center. The low-level winds on the latest balloon are from the southwest at 8-10 knots. This low-level wind flow will impede the progress of the east coast sea breeze somewhat, but it should progress inland into eastern Orange County by launch time. The mid-level storm steering winds also favor a very slow, eastward movement of interior and west coast storms.

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

"On Thursday the Bermuda ridge migrates further south of KSC creating slightly stronger southwest low-level flow, keeping the east coast sea breeze closer to the launch pad and increasing the probability of unacceptable launch weather."

The odds of acceptable weather are 60 percent today and 50 percent on Thursday.

1515 GMT (11:15 a.m. EDT)
Liquid hydrogen loading to 100 percent has been completed. The tank will be replenished through the rest of the countdown to replace the supercold propellant that naturally boils away.
1440 GMT (10:40 a.m. EDT)
The liquid hydrogen tank has reached the 98 percent level and began the topping sequence at 10:36 a.m. EDT.
1350 GMT (9:50 a.m. EDT)
Fast-fill of liquid oxygen is underway as well.

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

1330 GMT (9:30 a.m. EDT)
Liquid hydrogen loading has switched to the "fast-fill" mode as fueling of space shuttle Endeavour 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.

1319 GMT (9:19 a.m. EDT)
Liquid oxygen loading has completed chilldown and gone into slow-fill.
1249 GMT (8:49 a.m. EDT)
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.
1245 GMT (8:45 a.m. EDT)
Today's filling of space shuttle Endeavour's external fuel tank started at 8:38 a.m. EDT 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.
1238 GMT (8:38 a.m. EDT)
Right on time, launch director Pete Nickolenko has instructed his team in Firing Room 4 to begin fueling the space shuttle.
1227 GMT (8:27 a.m. EDT)
The Mission Management Team has given the "go" to fuel Endeavour for today's launch. There are no technical constraints against proceeding with the countdown, officials say.
1210 GMT (8:10 a.m. EDT)
There's a 60 percent chance that weather will be acceptable for launch of Endeavour today or a 40 percent chance conditions will again cause a scrub, according to the briefing given to mission managers this morning.

The forecast for the 6:03 p.m. EDT liftoff time includes showers and thunderstorms inland, a few clouds at 3,000 feet, scattered clouds at 8,000 feet and 25,000 feet, visibility of 7 miles, launch pad winds from the southeast at 8 peaking to 12 knots and a temperature of 83 degrees F.

0415 GMT (12:15 a.m. EDT)
Space shuttle Endeavour has been uncovered from the cocoon-like service gantry at launch pad 39A for Wednesday's planned 6:03 p.m. EDT liftoff. Ground technicians will spend the overnight hours getting pad equipment configured and secured in preparation for the morning's fueling operation.

The Mission Management Team is scheduled to convene its pre-fueling meeting at 8 a.m. to review the status of work, the readiness of shuttle systems and the latest weather forecast.

A topic expected to be discussed by the managers involves one of Endeavour's fuel cells. Testing of the electricity-generating system was being performed Tuesday night.

If all goes according to plan, loading of the external tank with propellant will start at 8:38 a.m. EDT. The process should take three hours to complete.

Endeavour's seven astronauts spent Tuesday studying flight plans and resting. The commander and pilot also got in some additional landing practice in the Shuttle Training Aircraft.

The crew will be awakened for launch day at 7 a.m. EDT. They'll have breakfast at 7:30 a.m. and then undergo final medical exams at 8 a.m.

0337 GMT (11:37 p.m. EDT Tues.)
The pad 39A rotating service structure has begun retracting to again reveal Endeavour for launch.

The gantry was placed back around the shuttle early Tuesday morning to give workers access in reattaching a loose thruster cover on the ship's nose.

0200 GMT (10:00 p.m. EDT Tues.)
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Standard definition clips are posted our video archive.

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0100 GMT (9:00 p.m. EDT Tues.)
We have updated our countdown, ascent and flight plan charts to reflect Wednesday's planned launch.

Read our earlier status center coverage.

STS-127 patch
The official embroidered patch for shuttle Endeavour's flight to finish building Japanese section of the space station.

Hubble crew
The official embroidered patch for mission STS-125, the space shuttle's last planned service call to the Hubble Space Telescope, is available for purchase.


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The official embroidered patch for the International Space Station Expedition 20 crew is now available from our stores.

STS-128 patch
The official embroidered patch for shuttle Discovery's flight to deliver equipment and research gear to the space station.