BY JUSTIN RAY

SATURDAY, AUGUST 18, 2007
2230 GMT (6:30 p.m. EDT)

Today's wrap up story has been updated following the mission status briefing. You can read it here.

2125 GMT (5:25 p.m. EDT)

With the potential threat of Hurricane Dean on the mission control center in Houston, NASA managers have approved the plan to undock shuttle Endeavour from the space station on Sunday morning. Landing at Kennedy Space Center has officially moved up a day, with touchdown now targeted for about 12:30 p.m. EDT on Tuesday.

The seven Endeavour astronauts said their farewells to the station crew earlier this hour, then floated into the shuttle and closed the hatchway.

1835 GMT (2:35 p.m. EDT)

Canadian astronaut Dave Williams and space station flight engineer Clay Anderson staged an abbreviated fourth and final spacewalk today, pausing for a moment to take in a spectacular bird's eye view of Hurricane Dean, the storm that prompted NASA managers to make preparations for an earlier-than-planned undocking and landing.

Read our full story.

1819 GMT (2:19 p.m. EDT)

EVA ENDS. Repressurization of the Quest airlock module began at 2:19 p.m. EDT, marking the official conclusion of this fourth and final spacewalk planned during Endeavour's mission to the space station.

Today's EVA lasted five hours and two minutes, bringing the total spacewalking time for the mission to 23 hours and 15 minutes.

1803 GMT (2:03 p.m. EDT)

Both spacewalkers have ingressed the space station's airlock.

1740 GMT (1:40 p.m. EDT)

Work on the Wireless Instrumentation System has wrapped up. The crew will be cleaning up tools and equipment before getting back to the airlock to end this EVA.

1700 GMT (1:00 p.m. EDT)

The spacewalkers are now working to route and hook up electrical cables for the new antenna equipment.

1645 GMT (12:45 p.m. EDT)

The space station complex is flying almost directly above Hurricane Dean. The monster storm is a Category 4 hurricane with winds near 150 mph.

1617 GMT (12:17 p.m. EDT)

Three hours and counting in this fourth and final EVA of Endeavour's trip to the space station. Both spacewalkers are working together to mount external antenna equipment on the Destiny lab module for the Wireless Instrumentation System, which is designed to measure vibrations and loads imparted on the station.

1600 GMT (12:00 p.m. EDT)

A smoke alarm has sounded in the Unity connecting node of the space station. It appears to be a false alarm. The crew reports no smoke and no smell.

1546 GMT (11:46 a.m. EDT)

Dave Williams has successfully battled the bolts on the Z1 truss' S-band communications antenna, tightening all four bolts on that device. Clay Anderson is heading to the Destiny laboratory module to begin installing antenna equipment for the Wireless Instrumentation System. This is the final planned task for the shortened spacewalk.

1520 GMT (11:20 a.m. EDT)

And now the second MISSE payload has been stowed in the airlock for return to Earth.

1506 GMT (11:06 a.m. EDT)

Clay Anderson has retrieved the first of the two MISSE experiment packages, which fold up like a suitcase. He placed it back inside the airlock. Dave Williams has been struggling with the troublesome bolts on the S-band antenna.

1430 GMT (10:30 a.m. EDT)

With the inspection bom supports now installed, the spacewalkers will be going their separate ways to accomplish different jobs. Dave Williams will be tightening gimbal locks on the Z1 truss' S-band communications antenna; Clay Anderson will be retrieving a pair of space exposure experiment packages called MISSE for return to Earth. Both of these tasks were deferred from the third spacewalk of the mission, which ended early because of spacesuit glove damage.

1417 GMT (10:17 a.m. EDT)

Now one hour into the spacewalk. Dave Williams and Clay Anderson are working on the Starboard 1 truss installing external brackets for the Orbiter Boom Sensor System. The OBSS is the laser and camera inspection boom used to survey the shuttle's heat shield for damage. During the STS-123 mission early next year, the boom will be left on the station because the following mission, STS-124 carrying the Japanese Kibo science laboratory, cannot fit the OBSS in the payload bay for launch.

1349 GMT (9:49 a.m. EDT)

Both spacewalkers are heading away from the airlock module now. Their departure was slowed when one of the control handles on Dave Williams' jet-powered rescue backpack accidentally deployed. Clay Anderson helped re-stow the handle.

The first task of today's spacewalk will see the astronauts install jack stands on the station's Starboard 1 truss to hold the shuttle inspection boom next year.

1317 GMT (9:17 a.m. EDT)

EVA BEGINS. Dave Williams and Clay Anderson switched their spacesuits to internal battery power at 9:17 a.m. EDT, marking the official start time for today's spacewalk outside the space station.

1316 GMT (9:16 a.m. EDT)

The outer hatch of the airlock leading to space has been opened.

1249 GMT (8:49 a.m. EDT)

Depressurization of the airlock has started in advance of today's spacewalk. The astronauts have progressed through the spacewalk preparations very well today and activities are running nearly 45 minutes ahead of the timeline.

1220 GMT (8:20 a.m. EDT)

Canadian astronaut Dave Williams and station flight engineer Clay Anderson are preparing for a shortened spacewalk today while their crewmates complete final equipment transfers to and from the station to clear the way for hatch closure later this afternoon.

Read our full story.

FRIDAY, AUGUST 17, 2007

NASA's Mission Management Team, after resolving concerns about damage to the shuttle Endeavour's heat shield, shifted gears Friday and began discussing the possibility of bringing the astronauts back to Earth on Tuesday, a day early, because of concern Hurricane Dean could threaten a shutdown of mission control at the Johnson Space Center in Houston.

Read our full story.

1200 GMT (8:00 a.m. EDT)

The Endeavour astronauts are working through a busy day in space today, trying to trace a subtle communications wiring problem, transferring supplies and equipment to and from the international space station and preparing for a fourth and final spacewalk Saturday.

Read our full story.

THURSDAY, AUGUST 16, 2007

NASA's Mission Management Team on Thursday ruled out an unprecedented heat shield repair spacewalk and cleared the shuttle Endeavour for re-entry and landing next week "as is" based on computer modeling and tests in a high-temperature furnace that show a small gouge in the ship's belly will not cause serious damage during the fiery plunge to Earth.

Read our full story.

1200 GMT (8:00 a.m. EDT)

The Endeavour astronauts are awake and working through a revised flight plan today, awaiting word from NASA's Mission Management Team on whether the space shuttle's gouged heat shield can stand up to the rigors of re-entry as is or whether an unprecedented tile repair spacewalk will be needed Saturday. During a morning "big picture" update for commander Scott Kelly, astronaut Chris Ferguson in mission control said a decision was expected by noon or shortly thereafter.

Read our full story.

WEDNESDAY, AUGUST 15, 2007

Our latest story has been updated following the mission status briefing. You can read it here.

2355 GMT (7:55 p.m. EDT)

As expected, the Endeavour astronauts will delay their fourth spacewalk, from Friday to Saturday, to protect against the possibility of an unprecedented heat shield repair. NASA's Mission Management Team met into the evening today, assessing test results and exploring various mission scenarios, but a final decision on whether or not to order a repair spacewalk was not expected until Thursday.

Read our full story.

2010 GMT (4:10 p.m. EDT)

Making a routine inspection of his spacesuit gloves, a recently implemented safety procedure because of damage found after a December shuttle flight, astronaut Rick Mastracchio spotted a small hole in one of the outer layers of his left glove, prompting mission control to order him back to the space station's airlock as a precaution.

Read our full story.

2006 GMT (4:06 p.m. EDT)

EVA ENDS. Repressurization of the Quest airlock module began at 4:05 p.m. EDT, marking the official conclusion of this third of four planned spacewalks during Endeavour's mission to the space station.

Today's EVA lasted five hours and 28 minutes, bringing the total spacewalking time for the mission to 18 hours and 13 minutes.

1940 GMT (3:40 p.m. EDT)

Clay Anderson is making his way into the airlock. Although today's EVA is ending early, the astronauts did complete all their tasks except for picking up the station's MISSE external experiment packages. Those will be retrieved and brought inside on a future spacewalk.

1906 GMT (3:06 p.m. EDT)

Mission Control says once Clay Anderson finishes his current task on the P6 truss, he will return to the airlock and end this spacewalk. Retrieval of two external experiment packages still left to accomplish on today's EVA plan will be deferred to another day.

1900 GMT (3:00 p.m. EDT)

While Rick Mastracchio waits in the open airlock, Clay Anderson is continuing his work on the Port 6 truss removing a failed transponder.

Mastracchio's glove damage triggers the flight rule that forces him to stop work and go to the airlock as a precaution. He saw the damage during a routine glove check. The checks occur about every 30 minutes, a chore that began after glove damage was noted during a December spacewalk.

1855 GMT (2:55 p.m. EDT)

Some damage has been spotted on the outer surface of Rick Mastracchio's spacesuit gloves. So as a precaution, he is being ordered back to the airlock.

1837 GMT (2:37 p.m. EDT)

Now four hours into the EVA.

1802 GMT (2:02 p.m. EDT)

The second of the two Crew and Equipment Translation Aid - CETA - carts has been locked in place on the Staboard 1 truss of the space station, completing this task for today's EVA.

The carts had to be relocated from the station's port side over to the starboard side. This clears the truss rail system for the October move of the Port 6 truss outboard using the robot arm and mobile transporter.

1745 GMT (1:45 p.m. EDT)

The second cart is now in the hands of Clay Anderson. It has been freed from the Port 1 truss for the move over to S1.

1728 GMT (1:28 p.m. EDT)

CETA cart No. 1 has been locked down on the S1 truss. The spacewalkers will be heading back to the Port 1 truss to get the second cart.

1723 GMT (1:23 p.m. EDT)

The spacewalkers are working together now the install the first cart to its new location on the Staboard 1 truss.

1705 GMT (1:05 p.m. EDT)

With Expedition 15 flight engineer Clay Anderson standing on the station arm, the astronaut has pulled the first CETA cart off the station rail tracks. He will hold the cart in his hands while the arm swings him from the station's port side over to the starboard side for re-installation of the CETA cart.

1646 GMT (12:46 p.m. EDT)

Both CETA carts have been readied for relocation. The crew will hand-carry each cart to the starboard side of the station while riding the robot arm.

1637 GMT (12:37 p.m. EDT)

Now passing the two-hour mark in the EVA. The S-band antenna relocation from the P6 truss down to the P1 truss has been completed by Rick Mastracchio. Both spacewalkers are working on the steps to prepare the CETA carts for moving to the other end of the station truss structure.

1618 GMT (12:18 p.m. EDT)

Mission Control says the spacewalkers are running almost an hour ahead of the timeline.

1610 GMT (12:10 p.m. EDT)

Anderson has completed the installation tasks for the new signal processor and transponder. He will be moving over to the CETA equipment railcars to prepare those for relocation from the port side of the station truss to the starboard side later today. Mastracchio continues his work to move the SASA antenna.

1550 GMT (11:50 a.m. EDT)

Down at the Port 1 truss segment of the space station, spacewalker Clay Anderson is working to install a signal processor and transponder.

1523 GMT (11:23 a.m. EDT)

Perched on the end of the space station's robot arm, Rick Mastracchio is headed for the top of the Port 6 truss to begin the relocation work on the SASA communications antenna.

1453 GMT (10:53 a.m. EDT)

Both spacewalkers have emerged from the Quest airlock module as the space station flies in orbital darkness over the western Pacific Ocean.

1439 GMT (10:39 a.m. EDT)

EVA BEGINS. Rick Mastracchio and Clay Anderson switched their spacesuits to internal battery power at 10:37 a.m. EDT, marking the official start time for today's spacewalk outside the space station.

1330 GMT (9:30 a.m. EDT)

Shuttle flier Rick Mastracchio and station astronaut Clay Anderson are gearing up for a planned six-and-a-half-hour spacewalk today to upgrade the international space station's S-band communications system and make final preparations for the relocation of a stowed solar array during the next shuttle assembly mission in October.

Read our preview story.

TUESDAY, AUGUST 14, 2007

Sophisticated computer analysis indicates the aluminum skin directly below a small gash in the shuttle Endeavour's heat shield will not exceed NASA's 350-degree safety limit during re-entry, a top NASA manager said late Tuesday, despite temperatures of up to 2,100 degrees just outside the gouge.

Read our full story.

1618 GMT (12:18 p.m. EDT)

Mission Control reports the External Stowage Platform No. 3 has been firmly attached to the space station's Port 3 truss, giving the outpost another spare parts deck.

1450 GMT (10:50 a.m. EDT)

The astronauts have successfully completed the robotic handoff of the stowage platform from the shuttle arm to the station arm. The so-called "big arm" has the two-and-a-half-ton spare parts rack in its grasp for installation to the Port 3 truss of the space station.

1400 GMT (10:00 a.m. EDT)

The Endeavour astronauts are working to robotically install a 7,000-pound equipment storage platform on the international space station today, a complex procedure requiring tight choreography between the shuttle and station robot arms.

Read our full story.

1341 GMT (9:41 a.m. EDT)

The External Stowage Platform-3 is slowly rising out of space shuttle Endeavour's payload bay right now. The spare parts deck was launched aboard Endeavour for delivery to the space station.

Astronaut Barbara Morgan grappled the platform with the shuttle's robot arm at 9:13 a.m. The arm will maneuver the 7,000-pound payload in reach of the station's robot arm, which will perform the actual installation task this morning.

MONDAY, AUGUST 13, 2007

The foam-damaged heat-shield tiles on the belly of Endeavour do not represent a Columbia-class threat of catastrophic failure during re-entry, the chairman of NASA's Mission Management Team said Monday.

Read our full story.

2325 GMT (7:25 p.m. EDT)

Astronauts Rick Mastracchio and Dave Williams successfully replaced an ailing control moment gyroscope on the international space station today to accomplish the primary goal of their second spacewalk.

Read our full story.

2201 GMT (6:01 p.m. EDT)

EVA ENDS. Repressurization of the Quest airlock module began at 6:00 p.m. EDT, marking the official conclusion of this second of four spacewalks during Endeavour's mission to the space station.

Today's EVA lasted six hours and 28 minutes, bringing the total spacewalking time for the mission to 12 hours and 45 minutes.

2150 GMT (5:50 p.m. EDT)

Both astronauts are back inside the airlock. The EVA officially ends with airlock pressurization.

2055 GMT (4:55 p.m. EDT)

The spacewalkers have installed a thermal cover on the failed gyro, completing their work on that unit. Rick Mastracchio will head back to the Z1 truss and tidy up that work area while Dave Williams rides the station arm back to the airlock to start putting away equipment before calling this EVA over.

2032 GMT (4:32 p.m. EDT)

Now passing the five-hour mark of the spacewalk.

2020 GMT (4:20 p.m. EDT)

The failed gyro is being stowed in the launch frame that the spacewalkers put on the station's external spare parts platform earlier today. The gyro will remain there until the STS-122 shuttle flight in December brings the device back to Earth.

1949 GMT (3:49 p.m. EDT)

Flight controllers report good power flow to the newly installed gyro.

1926 GMT (3:26 p.m. EDT)

The new gyroscope is firmly attached to the station.

1918 GMT (3:18 p.m. EDT)

Now the spacewalkers are driving bolts to hold the new gyro in its slot on the Z1 truss.

1910 GMT (3:10 p.m. EDT)

The new gyro has been carried over to its destination on the space station's Z1 truss. The astronauts are about to begin installing the 600-pound unit. Today's EVA continues to go well.

1851 GMT (2:51 p.m. EDT)

The spacewalkers have released six bolts to pull the new gyro from its launch structure.

1822 GMT (2:22 p.m. EDT)

The gyro support frame with the new gyroscope has been installed on the station external stowage platform near the airlock module. The spacewalkers will be removing the new gyro but leaving the frame in place. It will receive the failed gyro.

1759 GMT (1:59 p.m. EDT)

Mission Control says the spacewalkers are running right on the timeline.

1748 GMT (1:48 p.m. EDT)

Riding on the station arm, Dave Williams has hand-carried the new gyro up to the station.

1737 GMT (1:37 p.m. EDT)

The spacewalkers have freed the new gyroscope, along with its launch support frame, from the payload bay of space shuttle Endeavour. This entire assembly will be transported up to the station's external stowage deck next to the airlock where the support frame will be installed. That frame will receive the failed gyro later in today's spacewalk. Plans call for the old gyro to be returned to Earth on a subsequent shuttle flight later this year.

1732 GMT (1:32 p.m. EDT)

Now two hours into the spacewalk.

1715 GMT (1:15 p.m. EDT)

Rick Mastracchio has climbed to the payload bay to join Dave Williams. They are working to release the new gyroscope from its launch restraints aboard Endeavour.

1658 GMT (12:58 p.m. EDT)

"This is the most amazing ride I've ever had," Williams just said.

1655 GMT (12:55 p.m. EDT)

Canadian astronaut Dave Williams is taking a ride on the Canadian-built space station robotic arm. Perched in a foot platform on the arm, Williams is being maneuvered down to the shuttle bay to get the new gyroscope.

1634 GMT (12:34 p.m. EDT)

The gyro has been temporarily stowed to a handrail. The new gyro is awaiting retrieval by the spacewalkers down in Endeavour's payload bay.

1630 GMT (12:30 p.m. EDT)

The failed gyro has been removed from the space station. The 600-pound device is in the hands of astronaut Rick Mastracchio.

1626 GMT (12:26 p.m. EDT)

Working at both sides of the gyroscope, the spacewalkers have used their battery-powered tools to unfasten a half-dozen bolts that have held the unit to the space station.

1612 GMT (12:12 p.m. EDT)

Four power cables have been unhooked from the failed gyro. The spacewalkers will release a series of bolts before pulling the unit out of the station's Z1 truss.

1600 GMT (12:00 p.m. EDT)

After exiting the airlock, the spacewalkers made their way to the Z1 truss of the space station to begin preparing the worksite and equipment for removal of the failed gyro.

1533 GMT (11:33 a.m. EDT)

EVA BEGINS. Rick Mastracchio and Dave Williams switched their spacesuits to internal battery power at 11:32 a.m. EDT, marking the official start time for today's spacewalk to replace a failed control moment gyroscope on the space station.

1200 GMT (8:00 a.m. EDT)

The Endeavour astronauts are gearing up for a planned six-and-a-half-hour spacewalk today to replace one of the international space station's stabilizing gyroscopes, one of four needed to maintain the lab's orientation, or attitude, in orbit.

Read our preview story.

SUNDAY, AUGUST 12, 2007

A "focused inspection" of the shuttle Endeavour's heat shield today, prompted by concern over foam impact damage spotted earlier in the mission, revealed a deep gouge that nearly penetrates two adjacent tiles on the orbiter's belly. The damage was not apparent in realtime imagery downlinked from the shuttle, but higher resolution photos seen later in the day clearly showed a small but deep, scooped-out pit in the heat shield.

Read our full story.

2056 GMT (4:56 p.m. EDT)

MISSION EXTENDED. The successful operation of the Station to Shuttle Power Transfer System will allow space shuttle Endeavour's mission to be extended three additional days. The two-week flight now targets a landing on August 22 at Kennedy Space Center.

Going into the flight, NASA wanted to ensure the new power transfer system would work properly before committing to a two-week mission. Good performance out of the system, which feeds power from the station's solar arrays to Endeavour, means the shuttle now has enough consumables to remain aloft an extra three days.

This extension means the fourth spacewalk of Endeavour's flight will be possible, too.

1845 GMT (2:45 p.m. EDT)

Astronaut Tracy Caldwell, operating the shuttle Endeavour's robot arm, aimed a camera and laser scanner at the belly of the orbiter today in a "focused inspection" to precisely measure the size and depth of gouges in a handful of heat shield tiles cause by external tank foam debris during launch Wednesday. While image analysts will not draw any conclusions until their assessment is complete, the most significant damage site looked relatively minor to the untrained eye, a seemingly shallow gouge in two adjacent tiles.

Read our story.

1630 GMT (12:30 p.m. EDT)

The focused inspections are underway beneath space shuttle Endeavour. The crew just completed scanning the thermal barrier on the right-hand main landing gear door. Next, the Orbiter Boom Sensor System's lasers and cameras will examine the damaged tiles hit by a piece of debris from the external fuel tank some 58 seconds after liftoff.

1200 GMT (8:00 a.m. EDT)

The main focus today is an up-close inspection of heat shield tile damage spotted after Endeavour's launch on Wednesday. Engineers believe the damage in question was caused by a chunk of foam insulation that popped off a propellant line support bracket on the shuttle's external fuel tank 58 seconds after liftoff.

Read our story.

SATURDAY, AUGUST 11, 2007

Digital video from cameras mounted on Endeavour's solid-fuel boosters shows debris that hit the underside of the orbiter during launch Wednesday was a chunk of foam, not ice. A focused inspection Sunday using a laser scanner and a high-resolution camera is needed to fully assess the extent of the damage and what, if any, impact it might have during re-entry.

Read our story.

2305 GMT (7:05 p.m. EDT)

Astronaut Rick Mastracchio and Canadian flier Dave Williams floated back into the space station's Quest airlock, closed the hatch and began repressurizing the module at 6:45 p.m. to wrap up a successful six-hour 17-minute spacewalk. The astronauts accomplished all of their objectives, attaching a new solar array truss segment and latching down a folding radiator on another solar array segment to clear the way for relocation later this year.

Read our story.

2246 GMT (6:46 p.m. EDT)

EVA ENDS. Repressurization of the Quest airlock module began at 6:45 p.m. EDT, marking the official conclusion of this first of four spacewalks during Endeavour's mission to the space station.

Today's EVA lasted six hours and 17 minutes.

2241 GMT (6:41 p.m. EDT)

The spacewalkers are back in the airlock. Standing by for repressurization.

2230 GMT (6:30 p.m. EDT)

The radiator work has been completed and the spacewalkers are getting ready to wrap up this EVA.

2133 GMT (5:33 p.m. EDT)

The radiator is now fully retracted. The spacewalkers are going to work to lock it down.

2127 GMT (5:27 p.m. EDT)

Retraction of the radiator on the Port 6 truss is underway. The panel is being stowed in preparation for the truss' relocation outboard to its final spot on the station during the October shuttle flight. Once the radiator is folded up via remote commanding, the spacewalkers will install restraints to keep it locked down.

Port 6 was one of the early pieces of the station to be launched. It was placed in the center of the station to provide power during the initial years of the outpost's life, and this radiator was part of the station's early cooling system. But with the station's framework now built out, P6 is being readied to move outboard.

2110 GMT (5:10 p.m. EDT)

A U.S. command-and-control computer, one of three in charge of critical functions on the international space station, unexpectedly shut down today at 3:52 p.m. A backup C&C computer immediately took over and a third computer that was in standby mode reconfigured itself to serve as a "hot backup" in case of additional problems.

Read our story.

2047 GMT (4:47 p.m. EDT)

Work on the Starboard 5 truss has been completed by spacewalkers Rick Mastracchio and Dave Williams. The new truss was successfully installed to the space station today. The station's truss backbone now stretches 246 feet in length.

The EVA duo will head back to the airlock module for a quick recharge of the spacesuit oxygen systems before moving up to the Port 6 truss for retraction of a radiator panel.

1935 GMT (3:35 p.m. EDT)

With the crew still running a half-hour ahead of schedule, the spacewalkers are using the time to perform some get-ahead tasks that will prepare the S5 truss for arrival of the Starboard 6 solar array truss next year.

1928 GMT (3:28 p.m. EDT)

Now three hours into today's EVA. The spacewalkers have removed the grapple fixture and relocated it to the underside of the S5 truss. This was necessary to allow one of the space station solar wings a clear path to rotate for tracking the sun.

1842 GMT (2:42 p.m. EDT)

The next task now underway is relocating a robot arm grapple fixture on the Starboard 5 truss.

1826 GMT (2:26 p.m. EDT)

All four attachment bolts have been torqued down by the spacewalks -- the Starboard 5 truss is firmly part of the space station now.

1808 GMT (2:08 p.m. EDT)

The spacewalkers are running more than a half-hour ahead of the timeline as they torque bolts to complete attachment of the new Staboard 5 truss to the space station.

1735 GMT (1:35 p.m. EDT)

Endeavour pilot Charlie Hobaugh, operating the space station's robot arm, has mounted the Starboard 5 truss to become part of the outpost's truss backbone. S5 has been "soft-captured" by the existing S4 truss. The spacewalkers will bolt the new two-ton piece in place to permanently attach it to the station.

1727 GMT (1:27 p.m. EDT)

All four launch locks have been removed by the spacewalkers.

1707 GMT (1:07 p.m. EDT)

The spacewalkers have gotten in position to release four launch locks on the corners of the S5 truss. Once this task is completed, the truss will be connected to the station by the robot arm.

1640 GMT (12:40 p.m. EDT)

Both Mastracchio and Williams have exited the airlock for the first spacewalk in their astronaut careers. After gathering tools and equipment, they will make their way outbound to the end of the station's starboard-side truss structure where the S5 truss awaits installation. The station's robot arm has moved the truss to the pre-install position.

1628 GMT (12:28 p.m. EDT)

EVA BEGINS. Rick Mastracchio and Dave Williams switched their spacesuits to internal battery power at 12:28 p.m. EDT, marking the official start time for today's spacewalk to install the new Starboard 5 truss on the space station and stow a radiator on the Port 6 truss.

1557 GMT (11:57 a.m. EDT)

Airlock depressurization has begun. Preparations for today's spacewalk have progressed very smoothly.

1552 GMT (11:52 a.m. EDT)

The spacewalkers have moved into the airlock portion of the Quest module and the hatchway between them and the rest of the station has been closed. Depressurization of the airlock in advance of today's EVA should begin momentarily.

1225 GMT (8:25 a.m. EDT)

Amid ongoing work to assess the health of the shuttle Endeavour's heat shield, astronauts Rick Mastracchio and Dave Williams are gearing up for a six-and-a-half-hour spacewalk today to attach a 5,000 pound spacer segment to the space station's main solar array truss.

Read our preview story.

FRIDAY, AUGUST 10, 2007

The shuttle Endeavour, deftly piloted by commander Scott Kelly, glided to a gentle docking with the international space station today after a spectacular trans-Atlantic somersault to give the lab crew a chance to inspect the orbiter's heat-shield tiles. While analysis of high-resolution digital images will take several days to complete, engineers spotted a small gouge in the heat shield tile behind the right landing gear door that may have been caused by a chunk of ice that hit the orbiter 58 seconds after launch.

Read our updated story.

2228 GMT (6:28 p.m. EDT)

Mission managers have ordered a focused inspection on Sunday to examine a small area of tiles that was hit by something, believed to be ice, during launch. Images taken during today's backflip revealed an approximate three-inch by three-inch strike. Whether this area would require any repair by spacewalking astronauts is not yet known. Engineers will need to gather more information about the depth of the damage and analyze the heating the area would see during re-entry before deciding if a fix needs to be done. The shuttle has three different repair options available.

Meanwhile, the Station to Shuttle Power Transfer System was successfully activated at 5:17 p.m. EDT this afternoon. And the S5 truss has been handed to the station arm for tomorrow's installation.

2052 GMT (4:52 p.m. EDT)

The Starboard 5 truss is on its way out of the payload bay.

2004 GMT (4:04 p.m. EDT)

HATCHES OPEN. The hatchway between Endeavour and the space station has been opened, and the shuttle crew is being welcomed aboard the outpost.

Also upcoming is the unberthing of the S5 truss from Endeavour's payload bay by the shuttle robot arm. The truss will be handed to the station's arm to stay overnight. Installation of truss occurs tomorrow during the first spacewalk of the mission.

1959 GMT (3:59 p.m. EDT)

Endeavour's arm has a grasp on the S5 truss structure. Latches holding the truss in the payload bay will be released, allowing the arm to raise the cargo out of the shuttle for handoff to the station's robotic arm.

1945 GMT (3:45 p.m. EDT)

Hatch opening and the welcome ceremony are coming up shortly. Meanwhile, members of the shuttle crew are preparing to use Endeavour's robot arm to grapple the truss in the payload bay.

1830 GMT (2:30 p.m. EDT)

The shuttle Endeavour, deftly piloted by commander Scott Kelly, glided to a gentle docking with the international space station today after a spectacular trans-Atlantic somersault to give the lab crew a chance to inspect the orbiter's heat-shield tiles.

Read our full story.

1820 GMT (2:20 p.m. EDT)

The docking ring between the two craft has been retracted into Endeavour's Orbiter Docking System, pulling the station to a tight mating. The hooks and latches are driving shut to firmly connect the two spacecraft.

Pressure and leak checks will be performed by the crews before the hatchway is opened.

1803 GMT (2:03 p.m. EDT)

Docking occurred at 2:02 p.m. EDT as the two spacecraft flew 214 miles over the South Pacific.

1802 GMT (2:02 p.m. EDT)

CONTACT AND CAPTURE! Endeavour has arrived at the space station to install the Starboard 5 truss segment and an external spare parts platform, plus transfer a couple tons of supplies and equipment.

The relative motions of the shuttle and station will be allowed to damp out over the next few minutes by the spring-loaded docking system. Later, the hooks and latches will be closed to firmly join the two craft and Endeavour's Orbiter Docking System docking ring will be retracted to form a tight seal.

The opening of hatches between the station and shuttle is expected in about 90 minutes. That will be followed by a welcoming ceremony and safety briefing. Then the joint crews will get down to business and use the shuttle robot arm to hoist the S5 truss out of Endeavour's payload bay for handoff to the station's arm.

1801 GMT (2:01 p.m. EDT)

Four feet from docking.

1800 GMT (2:00 p.m. EDT)

Now 15 feet separating the shuttle from the station. Endeavour's thrusters are programmed to fire in a post-contact maneuver to force the two docking ports together. That procedure is being armed.

1759 GMT (1:59 p.m. EDT)

The distance to docking is now 20 feet.

1757 GMT (1:57 p.m. EDT)

The final approach beginning. The alignment between docking ports on Endeavour and the space station is acceptable and no "fly out" maneuver by the shuttle is necessary.

1756 GMT (1:56 p.m. EDT)

The spacecraft are flying into an orbital sunrise over the South Pacific.

1754 GMT (1:54 p.m. EDT)

The Expedition 15 crew is waiting in the Destiny laboratory module to greet the new visitors. The shuttle is about 60 feet away.

1749 GMT (1:49 p.m. EDT)

Endeavour is 100 feet from the station docking port. Based on this latest distance update from the crew, Mission Control estimates docking time is about 14 minutes away.

1745 GMT (1:45 p.m. EDT)

Everything is still looking good as Endeavour closes within 150 feet of the space station.

1739 GMT (1:39 p.m. EDT)

About 200 feet left to go.

1731 GMT (1:31 p.m. EDT)

Now about 300 feet from docking. Endeavour is closing at about two-tenths of a foot per second.

1727 GMT (1:27 p.m. EDT)

The shuttle's crew has been given a "go" for docking.

1724 GMT (1:24 p.m. EDT)

Endeavour has reached the point directly in front of the station along the imaginary line called the velocity vector, or +V bar. The shuttle is about 370 feet from the station.

1710 GMT (1:10 p.m. EDT)

Endeavour is beginning the arc from the point beneath the station to a point roughly 400 feet in front of the complex to align with the docking port on the Destiny module. Docking is less than 45 minutes away.

1705 GMT (1:05 p.m. EDT)

The pitch maneuver has been completed. Endeavour is back in the orientation where it started, with the payload bay looking up at the station.

1702 GMT (1:02 p.m. EDT)

The main engine nozzles of Endeavour are facing the station now as the shuttle points its tail upward.

1700 GMT (1:00 p.m. EDT)

This 360-degree, nose-first pirouette by Endeavour gives the station crew about 100 seconds of quality photography time to snap detailed pictures of the orbiter's black tiles in the search for any launch impact damage.

1659 GMT (12:59 p.m. EDT)

The formal photo-taking period has started for the station crew, now that the shuttle has rotated its underside in view of the laboratory complex.

1658 GMT (12:58 p.m. EDT)

Endeavour is nose-up facing the station as the two craft fly more than 200 miles above Earth.

1656 GMT (12:56 p.m. EDT)

The rendezvous pitch maneuver -- the 360-degree flip -- is beginning. The shuttle is the under the control of commander Scott Kelly, who is flying the ship from the aft flight deck.

1654 GMT (12:54 p.m. EDT)

One hour until docking. The separation distance is now 667 feet between the two vehicles as Endeavour and the station fly high over the Amazon.

1650 GMT (12:50 p.m. EDT)

Endeavour is arriving on the R-bar, the imaginary line from the station down to Earth. The shuttle is 800 feet from station.

1645 GMT (12:45 p.m. EDT)

At a distance of about 600 feet directly below the station, commander Scott Kelly will carry out a slow 360-degree rendezvous pitch maneuver, or RPM, that will point the belly of the shuttle at the station.

As the shuttle's underside rotates into view, the station's crew will photograph Endeavour's belly with handheld digital cameras equipped with 400- and 800-millimeter lenses.

The 800mm images should provide one-inch resolution for examination of landing gear door and external tank umbilical door seals. The 400mm will yield three-inch resolution.

After completing the RPM maneuver, Endeavour will fly directly ahead of the space station with the shuttle's nose facing deep space and its cargo bay pointed at the lab complex. Then Kelly will guide the spacecraft to a docking with a pressurized mating adapter attached to the Destiny lab module.

1640 GMT (12:40 p.m. EDT)

Now 1,700 feet between the two spacecraft. Endeavour is closing at a rate of 2.5 feet per second.

1638 GMT (12:38 p.m. EDT)

The shuttle is about 2,000 feet from the station. The fourth of the possible mid-course correction burn opportunities has been performed by Endeavour.

1626 GMT (12:26 p.m. EDT)

Now 4,500 feet between the two spacecraft. Endeavour is closing at a rate of 6.5 feet per second. That rate will slow dramatically and then stop when the shuttle reaches a point about 700 feet below the station for Endeavour's photography backflip.

1617 GMT (12:17 p.m. EDT)

Endeavour and the station are flying 214 miles above Earth. About 10,000 feet separate the two spacecraft now.

1612 GMT (12:12 p.m. EDT)

Endeavour has completed a pair of mid-course correction burns available during the approach.

1554 GMT (11:54 a.m. EDT)

Now two hours from docking. With Endeavour about 30,000 feet from the station, the two crews have established voice communications.

"We're waiting for ya," station astronaut Clay Anderson told shuttle commander Scott Kelly.

1515 GMT (11:15 a.m. EDT)

TI burn. The shuttle has performed the nine-second Terminal Initiation burn to begin the final phase of today's rendezvous. The brief firing used the left Orbital Maneuvering System engine on the tail of Endeavour.

The TI burn puts the shuttle on a trajectory to directly intercept the orbiting station over the next orbit and a half. This burn is the latest in a series of maneuvers performed by Endeavour during its two days of chasing the station since launch Wednesday.

Docking is anticipated shortly before 2 p.m. EDT.

1445 GMT (10:45 a.m. EDT)

"Endeavour, you are go for TI," CAPCOM Steve Robinson just told the astronauts.

The upcoming Terminal Initiation burn by the Orbital Maneuvering System on the shuttle will position Endeavour on course to intercept the station.

1355 GMT (9:55 a.m. EDT)

Our story previewing today's docking is posted here.

1245 GMT (8:45 a.m. EDT)

Flight Day 3 is underway aboard space shuttle Endeavour this morning as the orbiter heads for a linkup with the space station. At a distance of about 85 nautical miles, pilot Charlie Hobaugh reported spotting the station a short time ago.

Docking is expected around 1:54 p.m. EDT. An hour before that, Endeavour will perform the 360-degree backflip to allow the station residents to photograph the shuttle's underside and tiles.

A timeline of today's rendezvous and docking events is posted here.

THURSDAY, AUGUST 9, 2007

Preliminary analysis of launch photography indicates about nine small bits of foam insulation came off the shuttle Endeavour's external fuel tank during the climb to space Wednesday. But only three are believed to have possibly struck the orbiter and there are no obvious signs of any impact damage, officials said today.

Read our full story.

2300 GMT (7:00 p.m. EDT)

Checks of the shuttle's leading edges were accomplished today with no obvious signs of damage to Endeavour. The shuttle continues to close the gap to the space station for Friday's planned docking.

1830 GMT (2:30 p.m. EDT)

The astronauts have completed the inspection scans of Endeavour's starboard wing using the Orbiter Boom Sensor System. The crew is in the midst of the multi-hour job to survey the shuttle to look for any signs of launch damage. This precautionary safety inspection has become a standard activity for all post-Columbia shuttle crews.

Inspections of the orbiter's nose and the port wing are still to come today.

1420 GMT (10:20 a.m. EDT)

The Endeavour astronauts are working through a busy first full day in space, completing setup of the ship's laptop computer network, checking out their spacesuits and carrying out an exhaustive inspection of the shuttle's nose cap and wing leading edge panels later this afternoon.

Early today, the shuttle was trailing the international space station by 1,242 miles, closing the gap at about 160 miles per 90-minute orbit. Two rendezvous rocket firings are planned today to fine tune Endeavour's ongoing rendezvous and if all goes well, commander Scott Kelly will guide the shuttle to a linkup with the lab complex around 1:54 p.m. Friday.

The astronauts were awakened during their sleep period earlier today when an alarm sounded because of apparent low pressure in one of the five liquid oxygen tanks in the shuttle's fuel cell system. Flight controllers initially thought the alarm was the result of an instrumentation problem, but they now suspect the pressure controller for oxygen tank No. 5 has failed.

Read our full story.

0016 GMT (8:16 p.m. EDT Wed.)

The payload bay doors have been opened. And Mission Control just gave the astronauts a "go" for on-orbit operations.

WEDNESDAY, AUGUST 8, 2007
2350 GMT (7:50 p.m. EDT)

The shuttle Endeavour, making its first flight since the 2003 Columbia disaster, blasted off today on a space station assembly mission carrying a crew of seven that includes teacher-turned-astronaut Barbara Morgan, Christa McAuliffe's backup in the original Teacher in Space program.

Read our full story.

2336 GMT (7:36 p.m. EDT)

T+plus 60 minutes. The shuttle is en route to the space station for docking on Friday.

In a pre-flight interview, Endeavour pilot Charlie Hobaugh explained how the shuttle will catch up with the station following launch.

"It's all a matter of orbital mechanics. The lower you are, the faster you are in orbit. It's not speed differential in dramatic terms but it's enough that you basically phase your orbit. We launch with the station out in front of us and we stay in a lower orbit and catch up over a couple-day period of time. Then we step up our orbit over a series of burns, to slow down our closure up until docking day when everything is in control. The orbital plane is pretty much set on launch, and it's just a matter of playing our altitude against the station altitude to catch up."

2316 GMT (7:16 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 burn occurred over the Indian Ocean.

2314 GMT (7:14 p.m. EDT)

T+plus 37 minutes, 20 seconds. The maneuvering engines have ignited for the raising burn to reach a 198 by 143 mile orbit around Earth.

2300 GMT (7:00 p.m. EDT)

T+plus 23 minutes, 25 seconds. The umbilical doors are confirmed closed and latched.

2254 GMT (6:54 p.m. EDT)

T+plus 18 minutes. The two flapper doors on the belly of Endeavour are being commanded to swing shut to shield the umbilicals that had connected to the external fuel tank.

2246 GMT (6:46 p.m. EDT)

T+plus 9 minutes, 30 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.

2245 GMT (6:45 p.m. EDT)

T+plus 8 minutes, 48 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.

2245 GMT (6:45 p.m. EDT)

T+plus 8 minutes, 30 seconds. MECO. Main Engine Cutoff confirmed! Speeding along at five miles per second above the Atlantic Ocean, Endeavour returns to space for the first time in nearly five years.

2244 GMT (6:44 p.m. EDT)

T+plus 7 minutes, 45 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.

2244 GMT (6:44 p.m. EDT)

T+plus 7 minutes, 20 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.

2243 GMT (6:43 p.m. EDT)

T+plus 7 minutes. Main engines, fuel cells and APUs continue to perform well as Endeavour nears the completion of powered ascent.

2243 GMT (6:43 p.m. EDT)

T+plus 6 minutes, 30 seconds. "Press to MECO" Endeavour can now achieve a safe orbit on two engines. All three remain in good shape.

2242 GMT (6:42 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.

2242 GMT (6:42 p.m. EDT)

T+plus 5 minutes, 20 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.

2241 GMT (6:41 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.

2240 GMT (6:40 p.m. EDT)

T+plus 4 minutes, 1 second. 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 this evening's launch.

2239 GMT (6:39 p.m. EDT)

T+plus 3 minutes. Commander Scott Kelly just received the "Two-engine TAL" call from CAPCOM Chris Ferguson in Mission Control. The call means Endeavour can now reach the Transatlantic Abort Landing site in Moron, Spain if one main engine fails. However, all three engines continue to burn normally.

2239 GMT (6:39 p.m. EDT)

T+plus 2 minutes, 45 seconds. The twin Orbital Maneuvering System engines on the ship's tail have ignited to provide an extra boost in thrust in addition to Endeavour's three main engines.

2239 GMT (6:39 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.

2238 GMT (6:38 p.m. EDT)

T+plus 2 minutes, 10 seconds. A good separation of the twin solid rocket boosters has occurred. The shuttle continues its streak toward space on the power generated by the three liquid-fueled main engines.

2238 GMT (6:38 p.m. EDT)

T+plus 1 minute, 45 seconds. It's a beautiful evening ascent for Endeavour and crew. Commander Scott Kelly and pilot Charlie Hobaugh are joined on the flight deck by mission specialists Tracy Caldwell and Rick Mastracchio. Seated down on the middeck are mission specialists Dave Williams, Barbara Morgan and Alvin Drew.

2238 GMT (6:38 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.

2237 GMT (6:37 p.m. EDT)

T+plus 70 seconds. Endeavour's three main engines have revved up to their 104 percent power setting. And Mission Control has given the "go at throttle up" call.

2237 GMT (6:37 p.m. EDT)

T+plus 60 seconds. All systems are looking good one minute into the flight. Endeavour is traveling more than 1,000 miles per hour as the main engines and twin solid rockets continue to generate nearly 7 million pounds of thrust.

2237 GMT (6:37 p.m. EDT)

T+plus 35 seconds. Endeavour's three liquid-fueled main engines are easing back to two-thirds throttle to reduce the aerodynamic stresses on the vehicle as it powers through the dense lower atmosphere and breaks the sound barrier.

2237 GMT (6:37 p.m. EDT)

T+plus 25 seconds. Endeavour has completed the roll, putting the shuttle on course for its rendezvous with the space station on Friday. The station is currently flying over the Atlantic Ocean, southeast of Halifax, Nova Scotia.

2236:52 GMT (6:36:52 p.m. EDT)

T+plus 10 seconds. Houston is now controlling of the 20th flight of Endeavour as the roll maneuver begins to place the shuttle on its northeast trajectory toward orbit.

2236:42 GMT (6:36:42 p.m. EDT)

LIFTOFF! Liftoff of Endeavour, building the space station while building the future by inspiring the next generation. And the shuttle has cleared the tower!

2236:11 GMT (6:36:11 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.

2235:42 GMT (6:35:42 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.

2234:42 GMT (6:34:42 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.

2234:12 GMT (6:34:12 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 electricity for the mission beginning at T-50 seconds.

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.

2233:42 GMT (6:33:42 p.m. EDT)

T-minus 3 minutes. Orbiter steering check is now complete; the main engine nozzles are in their start positions.

2233:12 GMT (6:33:12 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.

2232:42 GMT (6:32:42 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.

2231:42 GMT (6:31:42 p.m. EDT)

T-minus 5 minutes. The "go" has been given for for Auxiliary Power Unit start. Pilot Charlie Hobaugh 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 Scott Kelly, 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.

2231:12 GMT (6:31:12 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.

2230:42 GMT (6:30:42 p.m. EDT)

T-minus 6 minutes. Pilot Charlie Hobaugh 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.

2229:12 GMT (6:29:12 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.

2228:42 GMT (6:28:42 p.m. EDT)

T-minus 8 minutes and counting. Pilot Charlie Hobaugh 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.

2227:42 GMT (6:27:42 p.m. EDT)

T-minus 9 minutes and counting! The Ground Launch Sequencer is now actively running this final phase of this evening's countdown to launch space shuttle Endeavour.

2226:42 GMT (6:26:42 p.m. EDT)

Countdown clock will resume in two minutes.

Once the countdown picks up, the Ground Launch Sequencer will be 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.

2225 GMT (6:25 p.m. EDT)

NASA launch director Mike Leinbach has conducted his poll and given approval to resume the countdown for liftoff at 6:36 p.m. this evening!

2224 GMT (6:24 p.m. EDT)

The final readiness poll by the NASA test director confirms there are no technical issues being addressed. The Range also reports "go" on the local weather. And Mission Control is ready for the flight.

2217 GMT (6:17 p.m. EDT)

Ten minutes are remaining in this built-in hold. Final readiness polls will be conducted over the next few minutes.

2206 GMT (6:06 p.m. EDT)

Now 30 minutes from launch of Endeavour. Liftoff remains set for 6:36 p.m. EDT.

In a pre-flight interview, Endeavour pilot Charlie Hobaugh talked about what it feels like being strapped aboard the shuttle during the final hours of the countdown and then launching into space.

"People always ask me 'were you nervous before you flew?' The biggest concern is what kind of anxiety you have prior to launch. My first flight we had which was STS-104 back in 2001, we had five crew members, four on the flight deck, one on the mid-deck and, out of the four fight deck crew members during the pre-launch count, everyone was just zonked. I mean, we were tired from sleep shift and everything so where you think you really might be really nervous and charged up, as we're sitting in the orbiter we basically were dozing off at some point just because we're so tired. It's a very long count, it's very relaxing.

"But then as you get closer to the actual countdown, things pick up. You need to do a lot more actions, kind of like a freight train...everything starts to come closer in the actual moment where you have engines start and then SRB ignition is very exciting and the vehicle just kind of leaps off the pad. You go from sitting and doing nothing to just everything's in high speed. It was also very exciting on my first launch where we launched into a sunrise so, about midway through our ascent, you know when it was dark, all the sudden we see the sun rising into our forward windows and you're supposed to be monitoring all the systems and looking for anything going on but you really cheat yourself if you don't look out the window once in a while.

"It's just a very surreal event. You get the force of acceleration that builds, especially towards the end of your 8 1Ž2-minute ascent to the point where it, breathing's a little forcible. You try to lift your arm and it wants to come back down of course. You're taking acceleration through your chest where you're usually used to it down through your spine when you're flying aircraft and pulling Gs. So it's a very different sensation. Then you go from 3G acceleration to absolutely nothing. You feel like you're falling forward in your straps from being pushed out of your seat.

"And then the other thing was the very surreal part, when our mid-deck crew member on my first flight came floating up from the mid-deck. Your arms still strapped in, I look over my shoulder and everything seems in slow motion. It is just a, a really incredible experience but it happens really fast.

"Basically, 40 percent of your training is done in 8 1Ž2 minutes and then you get another two weeks of your mission. Much less of your training time is spent really getting ready for the on-orbit phase."

2152 GMT (5:52 p.m. EDT)

The Closeout Crew has completed stowing the platforms and equipment in the White Room following crew module closure. The team is preparing to depart the pad now.

2150 GMT (5:50 p.m. EDT)

The solid rocket booster retrieval ships are positioned 140 nautical miles northeast of the launch pad, off the coast of Jacksonville, to await Endeavour's liftoff this evening. The ships will recover the twin boosters after they parachute into the Atlantic Ocean. The motor casings are towed back to the Cape to begin the process of preparing the boosters for reuse. Arrival at the port is expected on Friday afternoon.

2142 GMT (5:42 p.m. EDT)

T-minus 9 minutes and holding. Countdown clocks have gone into the planned 45-minute, 42-second built-in hold. Today's launch remains set for 6:36:42 p.m. EDT. There are no technical problems being worked and weather is still "go" for launch.

2138 GMT (5:38 p.m. EDT)

Mission Control in Houston has loaded Endeavour's onboard computers with the proper guidance parameters based on the projected launch time.

2137 GMT (5:37 p.m. EDT)

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

2136 GMT (5:36 p.m. EDT)

Now one hour away from launch of Endeavour.

Pilot Charlie Hobaugh is configuring the displays inside Endeavour's cockpit for launch while commander Scott Kelly enables the abort steering instrumentation.

2131 GMT (5:31 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 6:36:42 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.

2128 GMT (5:28 p.m. EDT)

The official launch window this evening opens at 6:32:52 p.m. and closes at 6:43:46 p.m. EDT.

2121 GMT (5:21 p.m. EDT)

T-minus 20 minutes and holding. The countdown has paused for a 10-minute built-in hold. Launch is scheduled for 6:36 p.m. EDT.

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.

2120 GMT (5:20 p.m. EDT)

The shuttle's crew compartment hatch is confirmed to be closed and latched for flight.

2115 GMT (5:15 p.m. EDT)

After reopening the hatch again, two of the Orbiter Closeout Crew technicians boarded Endeavour to watch the hatch being reclosed and see how the sensors were working.

2107 GMT (5:07 p.m. EDT)

A small crack in the foam on a bracket for the external tank liquid oxygen feedline has been examined following fueling this afternoon. The Mission Management Team says the crack is not a concern for launch.

2105 GMT (5:05 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.

2055 GMT (4:55 p.m. EDT)

The hatch has been swung shut again.

2051 GMT (4:51 p.m. EDT)

The crew module hatch has been pulled open again because of problem with the sensors that should indicate the hatch is closed. The closeout team is looking at the hatch and sensors before trying to close it again.

2041 GMT (4:41 p.m. EDT)

Now passing the T-minus 1 hour mark in the countdown. Two scheduled holds are planned at T-minus 20 minutes and T-minus 9 minutes, leading to the target liftoff time of 6:36 p.m.

The final pre-flight alignment of Endeavour's guidance system inertial measurement units is underway.

2029 GMT (4:29 p.m. EDT)

Endeavour's crew module hatch is being closed for launch.

2011 GMT (4:11 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. Countdown activities remain on track for liftoff at 6:36 p.m. There are no technical issues being worked and the weather is acceptable today.

At this point in the count, the Ground Launch Sequencer software that will control the final nine minutes of the countdown has been initialized. Also, the solid rocket boosters' gas generator heaters in the hydraulic power units are turned on, the aft skirt gaseous nitrogen purge is starting and the rate gyro assemblies (RGAs) are being activated. The RGAs are used by the orbiter's navigation system to determine rates of motion of the boosters during the first stage of flight.

1958 GMT (3:58 p.m. EDT)

The final crewmember just boarded Endeavour. Rick Mastracchio serves as mission specialist No. 2 and flight engineer on Endeavour. He will ride in the flight deck's aft-center seat.

Read his biography here.

1945 GMT (3:45 p.m. EDT)

Tracy Caldwell, another rookie on the crew, is mission specialist No. 1 for Endeavour. The Arcadia, California native is climbing to the flight deck's aft-right seat.

Read her biography here.

1943 GMT (3:43 p.m. EDT)

Teacher-turned-astronaut Barbara Morgan just boarded space shuttle Endeavour for her long-awaited launch. She will take the center seat on the middeck.

Read her biography here.

1936 GMT (3:36 p.m. EDT)

Three hours and counting until liftoff time.

1925 GMT (3:25 p.m. EDT)

Pilot Charlie Hobaugh, a lieutenant colonel in the Marine Corps., is making his way to the flight deck's front-right seat.

Hobaugh was born in Bar Harbor, Maine. His previous shuttle flight was STS-104 to install the Quest airlock module at the space station in 2001.

Read his biography here.

1924 GMT (3:24 p.m. EDT)

Canadian Space Agency astronaut Dave Williams serves as mission specialist No. 3 on Endeavour's STS-118 flight. He just entered the orbiter to take the middeck's left seat.

Read his biography here.

1913 GMT (3:13 p.m. EDT)

Rookie astronaut Alvin Drew, the mission specialist No. 5 for STS-118, has boarded Endeavour to take the middeck's right-side seat. He considers Washington, DC to be his hometown.

Read his biography here.

1912 GMT (3:12 p.m. EDT)

Commander Scott Kelly is the first astronaut to board the shuttle. He is taking the forward-left seat on the flight deck.

A commander in the U.S. Navy and a native of Orange, New Jersey, has flown one previous shuttle mission -- as pilot of STS-103 in 1999 that serviced the Hubble Space Telescope. Read his biography here.

1902 GMT (3:02 p.m. EDT)

Endeavour's crew arrived at launch pad 39A at 3:01 p.m. 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.

1855 GMT (2:55 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 en route to the pad.

1846 GMT (2:46 p.m. EDT)

With commander Scott Kelly leading the way, the seven-person astronaut crew just departed the Kennedy Space Center crew quarters to board the silver AstroVan for the 20-minute ride from the Industrial Area to launch pad 39A on the edge of the Atlantic Ocean.

The crew includes pilot Charlie Hobaugh, spacewalkers Rick Mastracchio and Dave Williams, rookies Tracy Caldwell and Al Drew, and educator-astronaut Barbara Morgan. A former Idaho school teacher, Morgan was Christa McAuliffe's backup in the original "teacher-in-space" program.

1841 GMT (2:41 p.m. EDT)

T-minus 3 hours and counting. The countdown clocks are ticking again after the planned three-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 6:36:42 p.m. EDT launch time.

1836 GMT (2:36 p.m. EDT)

Four hours from launch.

1821 GMT (2:21 p.m. EDT)

The crew has donned the 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 2:45 p.m.

1806 GMT (2:06 p.m. EDT)

Commander Scott Kelly, pilot Charlie Hobaugh and flight engineer Rick Mastracchio are receiving a weather briefing on expected conditions at the Kennedy Space Center and the primary abort landing sites. Meteorologists say the weather here at the Cape and at the TAL landing sites in Europe shouldn't be a problem today.

Meanwhile, the rest of the crew is moving into the suitup room to start donning their suits.

1736 GMT (1:36 p.m. EDT)

Launch of Endeavour is now five hours away. All continues to go smoothly in this afternoon's countdown.

In a pre-flight interview, mission specialist Dave Williams offered an overview of Endeavour's mission to the space station.

"STS-118 is going to be a really exciting mission. There's three main objectives for the mission. The first one is: We're going to be taking up a section of the space station, called S5 -- it's one of the truss elements -- and we're going to be lifting it out of the payload bay of the space shuttle and installing it using the robotic arm in the shuttle, handing it off to the space station, then putting it out on the starboard side to enable us to put more solar panels out to provide power for the space station. In addition to that, we're also going to be doing a number of spacewalks, and helping to continue building the structure of the space station.

"The second main objective is to take a number of cargo items up to the space station and resupply the space station. Of course, when you're living and working in space in this closed environment, you go through a lot of consumables; we rely on other spacecraft to bring those consumables up.

"And, the third objective of the spaceflight, which is really exciting, is the first flight of the educator astronaut. Barbara Morgan will be flying with us as a mission specialist educator astronaut, trying to captivate the imagination of the youth of America, looking at that next generation of space exploration, what we're going to need in terms of technology, to live and work on the surface of the moon or send humans to Mars."

1710 GMT (1:10 p.m. EDT)

The countdown is in the midst of the T-minus 3 hour hold point. During this time, the preflight calibration of Endeavour's three inertial measurement units is performed, the Merritt Island Launch Area (MILA) tracking antennas are aligned and testing with the Eastern Range will be completed.

1645 GMT (12:45 p.m. EDT)

The Final Inspection Team is performing its observations of Endeavour this afternoon.

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.

1625 GMT (12:25 p.m. EDT)

The astronauts have been seated in the crew quarters' dining room for the traditional launch day photo. They will be moving into the suitup room shortly to begin donning the launch and entry spacesuits before heading to the launch pad at abut 2:46 p.m. this afternoon.

1610 GMT (12:10 p.m. EDT)

Endeavour's mission will further the assembly of space station. The international outpost brings together nations from around the globe, including the U.S. Russia, Europe, Canada and Japan.

In a pre-flight interview, mission specialist Dave Williams, an astronaut from the Canadian Space Agency, says the international collorabation on the space station project paves the way for future exploration.

"One of the exciting elements of the International Space Station is the partnership that came from all over the world to build this amazing orbital laboratory technology development platform. We have people from different cultures, different languages, different backgrounds, technologically, all working together, delivering hardware that, in some cases, has actually never been fit-tested until it gets to space. And amazingly, it all comes together, and it all works.

"The lessons that we've learned from that, working together, collaboratively, as the space-faring nations of the world are critical lessons that will help us leave low Earth orbit as the space-faring nations of the world to go back to the moon, go on to Mars on the behalf of humanity."

1541 GMT (11:41 a.m. EDT)

T-minus 3 hours and holding. The countdown has gone into the next planned hold in the timeline. This hold is scheduled to last three hours. Endeavour's precise launch time is targeted for 6:36:42 p.m.

Everything is looking good right now, with no significant technical problems being reported and forecasters giving a positive weather outlook today.

1503 GMT (11:03 a.m. EDT)

FUELING COMPLETED. The external fuel tank has been pumped full with a half-million gallons of supercold liquid oxygen and liquid hydrogen. The three-hour fueling process started at 8:11 a.m. with the chilldown conditioning.

But given the cryogenic nature of the oxidizer and propellant, the supplies naturally boil away. So the tanks are continuously topped off until the final minutes of the countdown in a procedure called "stable replenishment."

With the hazardous tanking operation completed, the Orbiter Closeout Crew and Final Inspection Team have been given the OK to go 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.

1442 GMT (10:42 a.m. EDT)

The level in the liquid oxygen tank is above 85 percent now.

1420 GMT (10:20 a.m. EDT)

Good morning from the Kennedy Space Center where fueling operations are going well at launch pad 39A for liftoff of space shuttle Endeavour later this evening. The liquid hydrogen portion of the external tank has reached the 98 percent level and the topping sequence has started. The liquid oyxgen filling has passed the 75 percent mark.

1241 GMT (8:41 a.m. EDT)

T-minus 6 hours and counting. Countdown clocks have resumed from a planned hold point. The count now proceeds to the T-minus 3 hour mark where the next planned hold will occur. Launch is still targeted to occur at 6:36 p.m. EDT.

1235 GMT (8:35 a.m. EDT)

FUELING UNDERWAY. The filling of space shuttle Endeavour's external fuel tank with a half-million gallons of supercold propellants has begun at launch pad 39A.

The tanking operation commenced with the chilldown thermal conditioning process at 8:11 a.m., a bit earlier than anticipated. This three-hour process continues by the slow-fill mode and then the fast-fill mode.

The cryogenics are pumped 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.

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.

There are no technical issues being worked in the countdown and the weather outlook continues to predict an 80 percent chance of good conditions at this evening's 6:36 p.m. EDT launch time.

TUESDAY, AUGUST 7, 2007

The rotating gantry at space shuttle launch pad 39A swung away from Endeavour tonight, moving the countdown a critical step closer toward Wednesday's planned 6:36 p.m. EDT liftoff.

The service structure retraction began at 8:53 p.m. EDT. Ground crews had the gantry in the park position for launch by 9:45 p.m.

Some photos from the rollback are posted here.

The overnight hours will be spent performing the final configuring of pad equipment and preparing systems for fueling space shuttle Endeavour's external fuel tank. The loading of a half-million gallons of supercold liquid hydrogen and liquid oxygen into the shuttle should begin by 8:30 a.m. EDT. That process will take three hours to complete.

With the shuttle launch team controlling from Firing Room 4, Endeavour's three-day countdown to blastoff has been going smoothly. The ship's three electricity-producing fuel cells were loaded with their cryogenic reactants Monday night, and activities on Tuesday included powering up the shuttle's avionics for testing, checking the air-to-ground communications systems and performing routine tests of the main engines.

The seven astronauts received countdown status and payload briefings on Tuesday, visited the launch pad to see the shuttle, packed personal items to be loaded aboard Endeavour, reviewed their flight plan and spent time with family members. They will be awakened shortly after 8 a.m. for launch day events.

Watch this page for live countdown and launch reports beginning with fueling operations in the morning.

1445 GMT (10:45 a.m. EDT)

The shuttle Endeavour's countdown is ticking smoothly toward launch Wednesday, with no significant technical problems and with forecasters now predicting an 80 percent chance of good weather. This will Endeavour's first flight since the 2003 Columbia disaster and the second of four space station assembly missions planned this year.

Read our full story.

MONDAY, AUGUST 6, 2007

Our detailed preview of Endeavour's mission is now available:

Fresh out of a lengthy overhaul, the shuttle Endeavour is poised for blastoff Wednesday on a space station assembly mission, the orbiter's first flight since the 2003 Columbia disaster. The high-profile multi-spacewalk mission features Barbara Morgan, a 55-year-old elementary school teacher-turned-astronaut who has waited 21 years for a chance to fulfill Christa McAuliffe's legacy as the original Teacher in Space.

Read the full report.

2005 GMT (4:05 p.m. EDT)

The Mission Management Team wrapped up its launch-minus-2-day meeting and all systems remain "go." The countdown continues to progress smoothly and there are no significant technical issues being worked.

1515 GMT (11:15 a.m. EDT)

Engineers started the shuttle Endeavour's countdown Sunday evening and with good weather expected, officials said today that so far, there are no technical problems at pad 39A that would prevent an on-time liftoff Wednesday.

"At this point, we are on schedule and we are tracking no significant issues," said NASA Test Director Jeff Spaulding.

Read our full story.

SUNDAY, AUGUST 5, 2007

The three-day countdown commenced as planned at 8 p.m. tonight for Wednesday's launch of space shuttle Endeavour.

1515 GMT (11:15 a.m. EDT)

Engineers at the Kennedy Space Center are gearing up to start the shuttle Endeavour's countdown this evening at 8 p.m. EDT, setting the stage for launch on a space station assembly mission at 6:36 p.m. EDT Wednesday. Forecasters are predicting a 70 percent chance of good weather for launch.

Read our full story.

FRIDAY, AUGUST 3, 2007

The shuttle Endeavour's seven-member crew flew to the Kennedy Space Center today to prepare for launch next week on a space station assembly mission. Commander Scott Kelly said the astronauts agreed with the decision earlier today to delay launch 24 hours, from Tuesday to Wednesday, to get back on schedule after unexpected work to replace a suspect valve in the shuttle's crew cabin pressurization system.

Read our full story.

2042 GMT (4:42 p.m. EDT)

Just hours after NASA managers postponed their launch by one day, the seven space shuttle Endeavour astronauts arrived at the Kennedy Space Center at 4:40 p.m. EDT this afternoon.

Led by commander Scott Kelly, the crew traveled from Ellington Field near Houston's Johnson Space Center to the Cape to begin final preparations for launch Wednesday on the latest construction flight to the International Space Station.

The crew includes pilot Charlie Hobaugh, spacewalkers Rick Mastracchio and Dave Williams, rookies Tracy Caldwell and Al Drew, and educator-astronaut Barbara Morgan. A former Idaho school teacher, Morgan was Christa McAuliffe's backup in the original "teacher-in-space" program.

The decision to slip the launch from Tuesday to Wednesday evening was made to give engineers more time to catch up on pre-flight work.

"NASA officials decided after a scheduling meeting Friday afternoon to reschedule the launch after it became apparent there was insufficient time to begin the countdown on schedule, complete remaining work and assure launch on Tuesday," an agency spokesman said.

"The additional day will provide time to complete the processing."

Activities at pad 39A had fallen behind schedule with this week's replacement of a faulty pressure valve in the shuttle's crew module. The valve in question was one of two positive pressure-relief valves that ensure that the cabin does not become over-pressurized.

Technicians removed the valve and installed one borrowed from shuttle Atlantis. The replacement work has been completed and the crew module has passed leak checks.

Work underway at the pad today involves vehicle ordnance, fuel system pressurization and closeouts of the aft main engine compartment.

The three-day launch countdown now begins at 8 p.m. EDT on Sunday, leading to liftoff on Wednesday at about 6:36 p.m. EDT.

The astronauts will spend the next few days studying the flight plan, receiving status briefings, undergoing medical exams and practicing shuttle landing approaches in a modified Gulfstream jet.