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TUESDAY, APRIL 8, 2003

Expedition 6 Commander Ken Bowersox and NASA Science Officer Don Pettit reconfigured critical power cables and continued the external outfitting of the International Space Station today during a 6 hour, 26 minute spacewalk designed to complete a number of get-ahead tasks for future ISS assembly.

Taking advantage of the final days of a three-man presence on the ISS before the new Expedition 7 crew is launched, Bowersox and Pettit began the second spacewalk of their increment at 8:40 a.m. EDT (1240 GMT). It was the second spacewalk for both Bowersox and Pettit, the 51st spacewalk for ISS assembly and maintenance and the 17th spacewalk staged from the U.S. Quest Airlock. Flight Engineer Nikolai Budarin helped the crew suit up and monitored ISS systems from inside the Destiny Laboratory during the excursion.

Bowersox and Pettit set out immediately to set up tools and tethers, and quickly went to work on separate tasks. Bowersox reconfigured electrical connectors at the interfaces between the Starboard Zero (S0) Truss and the two trusses flanking it, the Starboard One (S1) Truss and the Port 1 (P1) Truss. The connector work will insure that additional protection is in place to prevent the inadvertent release of the truss segments from the S0 Truss through the trusses' Bolt Bus Controller system. Bowersox also inspected a faulty heater cable on the P1 Truss Nitrogen Tank Assembly but found nothing unusual.

While that work was being conducted, Pettit replaced a power relay box in the Mobile Transporter railcar system, which has experienced some electrical problems in recent weeks.

Both spacewalkers then made their way to the Z1 (Zenith One) Truss, where they successfully rerouted power cables to two of the four Control Moment Gyros (CMGs) that provide orientation control for the ISS from the U.S. segment. One CMG failed almost a year ago, and the cable reconfiguration to CMGs # 2 and 3 will prevent both from being disabled in the unlikely event a power failure occurs. The ISS can be properly oriented with just two CMGs in operation. A replacement for the failed CMG will be flown to the ISS and installed on the first post-Columbia shuttle mission, STS-114.

Bowersox and Pettit pressed ahead to install two so-called Spool Positioning Devices on fluid quick disconnect lines for the heat exchanger on the Destiny Laboratory. The devices help keep internal seals and moving parts from experiencing internal leakage as ammonia flows through the station's cooling system.

With that completed, the two station crewmembers ventured to the S1 Truss to secure a thermal cover on the truss' Radiator Beam Valve Module, which controls the flow of ammonia to the truss' heat-rejecting radiators.

One final task awaited Bowersox and Pettit -- the deployment of a balky light stanchion for the handrail cart on the S1 Truss that would not unfurl during the previous spacewalk by the two crewmembers in January. The stanchion proved to be just as stubborn this time, but Pettit used a hammer to tap the stanchion free from its stowed position on the 10th try. A light was then installed on the stanchion, giving the truss the illuminating capability it needs to assist future spacewalkers.

With all of their work completed, Bowersox and Pettit retrieved some tools for future spacewalks from external locations and returned to Quest to complete their spacewalk at 3:06 p.m. EDT (1906 GMT).

The crew will spend a quiet day tomorrow relaxing before resuming its complement of scientific research and routine maintenance work on board the ISS Thursday.

Meanwhile, Expedition 7 Commander Yuri Malenchenko and Flight Engineer/NASA ISS Science Officer Ed Lu completed final preparations before traveling to the Baikonur Cosmodrome in Kazakhstan tomorrow from their training base in Star City, Russia to inspect the Soyuz TMA-2 vehicle in which they will be launched on April 26 to begin a six-month mission on the ISS.

1907 GMT (3:07 p.m. EDT)

The Quest airlock is being repressurized, officially ending today's successful spacewalk by Expedition 6 commander Ken Bowersox and NASA science officer Don Pettit. This 51st EVA dedicated to International Space Station operations lasted nearly six-and-a-half hours.

1901 GMT (3:01 p.m. EDT)

With the spacewalkers back inside, the outer hatch of the airlock has been closed.

1840 GMT (2:40 p.m. EDT)

Some difficulty was reported with one of the tool bags. Mission Control has said to move on.

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

Bowersox and Pettit are wrapping up the tool and hardware relocation "get-ahead" tasks. Once complete, they will march through standard clean-up procedures to put away their tools and tethers before climbing in the airlock for repressurization.

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

The spacewalkers are working on the additional bonus work following the successful completion of their planned activities today.

1720 GMT (1:20 p.m. EDT)

Now 4 hours, 40 minutes into today's spacewalk. Bowersox and Pettit have completed all of the primary tasks scheduled for this excursion. Flight controllers are now looking at having the astronauts perform some extra "get-ahead" chores, including the relocation of tools, clamps and tethers from the exterior of the Unity node and Z1 truss to the toolboxes on the Quest airlock.

1714 GMT (1:14 p.m. EDT)

The astronauts report they have completed tightening all the bolts associated with the stanchion boom and light fixture.

1703 GMT (1:03 p.m. EDT)

Bowersox and Pettit continue their efforts to install that light fixture.

1635 GMT (12:35 p.m. EDT)

The spacewalkers are now attaching a light fixture to the top of the stanchion they freed earlier.

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

A sharp tap of the hammer has freed the stuck lighting stanchion. It took Pettit 10 tries to free the stubborn pole.

1555 GMT (11:55 a.m. EDT)

The two spacewalkers are trying to free a stuck lightning pole on one of the Crew and Equipment Translation Aid (CETA) carts by tapping it with a Russian-made hammer. They had tried unsuccessfully to deploy the stanchion during their first spacewalk in January.

1500 GMT (11:00 a.m. EDT)

The two spacewalkers are making swift progress during their spacewalk this morning.

Bowersox began the EVA by successfully reconfiguring electrical connectors in the areas that bolt the space station's center truss span to the two outer truss segments. This work will prevent the the truss segments from being inadvertently detatched. Pettit, meanwhile, replaced a faulty power relay box, one of two that are used to operate the mobile transporter rail system. The replacement box checked out fine.

The two spacewalkers then reconfigured power cables for the station's Control Moment Gyros (CMGs), providing a second path of power for devices. The rewiring will prevent a single power failure stopping two gyros, which would cripple the station's U.S. attitude control system.

Next up was the installation of two 1-inch clamps along the heat exchanger quick disconnect lines to prevent ammonia leakage from the lines.

1328 GMT (9:28 a.m. EDT)

The spacewalkers are currently about 45 minutes ahead of their timeline, according to mission commentator Rob Navias.

1300 GMT (9:00 a.m. EDT)

Pettit has joined Bowersox outside the airlock.

1253 GMT (8:53 a.m. EDT)

We are receiving our first TV views of Bowersox working outside the airlock.

1248 GMT (8:48 a.m. EDT)

Bowersox has emerged from the airlock. "All right! It's certainly a nice day out here," said the veteran astronaut, who is making his second spacewalk. The astronaut's first task will be to configure safety tethers for the spacewalk.

1247 GMT (8:47 a.m. EDT)

The spacewalkers have been given a "go" by flight controllers to leave the airlock.

1240 GMT (8:40 a.m. EDT)

The 51st spacewalk in support of the International Space Station is officially underway with the astronauts switching their spacesuits to internal battery power.

1239 GMT (8:39 a.m. EDT)

Bowersox reports that the hatch is open.

1238 GMT (8:38 a.m. EDT)

Bowersox has been given a "go" to open the space station's airlock hatch.

1230 GMT (8:30 a.m. EDT)

The Quest airlock is now nearing a vacuum.

1211 GMT (8:11 a.m. EDT)

The spacewalkers have about another seven minutes in their prebreathe protocol, a proceedure designed to purge the blood of nitrogen and prevent a case of the "bends".

1203 GMT (8:03 a.m. EDT)

The airlock has been depressurized to 5 psi. It will hold at this pressure while the astronauts check their spacesuits.

1153 GMT (7:53 a.m. EDT)

Depressurization of the Quest airlock has begun.

1130 GMT (7:30 a.m. EDT)

Space station commander Kenneth Bowersox and science officer Donald Pettit are now in the crewlock compartment of the space station's airlock in readiness for a planned six-and-a-half-hour spacewalk that is due to get underway at about 1230 GMT (8:30 a.m. EDT). Depressurization of the airlock is due to begin in about 20 minutes.

MONDAY, APRIL 7, 2003

Space station commander Kenneth Bowersox and science officer Donald Pettit are gearing up for a planned six-and-a-half-hour spacewalk Tuesday to complete a series of chores before the orbiting complex is turned over to a two-man crew later this month.

NASA television coverage will begin at 7 a.m. EDT, about 90 minutes before the EVA is scheduled to start.

Spacewalk tasks include reconfiguring power connections, providing a second power source for one of the station's control moment gyroscopes, securing thermal covers on quick disconnect fittings for the station's thermal control system and releasing a light stanchion on one of the Crew and Equipment Translation Aid (CETA) carts.

This spacewalk -- staged from the Quest Airlock -- will be the 51st conducted at the station and the 26th based out of the station.

Expedition 6 flight engineer Nikolai Budarin will monitor the spacewalk from inside the station. It will be the second EVA of this expedition. A January walk was also performed by Bowersox and Pettit.

The three men will be replaced by the Expedition 7 crew of cosmonaut Yuri Malenchenko and NASA astronaut Ed Lu. The fresh crew is scheduled for launch April 26 aboard a Russian Soyuz capsule. Expedition 6 will ride the station's current Soyuz back to Earth on May 3.

Following the Columbia tragedy and grounding of the shuttle fleet, space station assembly operations were put on hold. A three-person Expedition 7 crew -- Malenchenko, Lu and cosmonaut Alexander Kaleri -- had been slated to launch aboard shuttle Atlantis in early March. However, water restrictions on the station forced the station resident crews be reduced to two people until shuttles resume resupply missions to the orbiting outpost.

THURSDAY, JANUARY 16, 2003

Space shuttle Columbia has been filled up with over a half-million gallons of cryogenic liquid hydrogen and liquid oxygen propellants in preparation for today's 10:39 a.m. EST (1539 GMT) blastoff on a 16-day scientific reseearch spaceflight. There is a 95 percent chance of favorable weather during today's 2 1/2-hour launch window.

For our live Mission Status Center coverage of Columbia's voyage, click here.

WEDNESDAY, JANUARY 15, 2003
1941 GMT (2:41 p.m. EST)

The 50th spacewalk dedicated to the international space station has been successfully completed. Expedition 6 commander Kenneth Bowersox and ISS science officer Donald Pettit begqn repressurizing the Quest airlock at 2:41 p.m. EST to bring this six-hour, 51-minute EVA to an end. All of the objectives were completed except for the mounting of an external light fixture to a equipment cart on the station's rail tracks. The highlight of the day was the deployment of a 75-foot long radiator array from the P1 truss segment.

1936 GMT (2:36 p.m. EST)

Bowersox confirms he has cut away the fabric strap that got in the way this morning during hatch opening.

1914 GMT (2:14 p.m. EST)

The spacewalkers are back in the airlock. They are about use a pair of scissors to cut off that fabric loop from the airlock cover. The end of the EVA marked when airlock repressurization begins.

1835 GMT (1:35 p.m. EST)

The spacewalk is entering the home stretch. The astronauts have been unable to complete the installation of that light fixture to the crew equipment cart on the S1 truss because of an apparent problem with a pin not disengaging. This was considered a low priority chore of the spacewalk. The check of the ammonia coolant tank was successfully completed. Still to be completed is the relocation of some tools and the added task of cutting off a fabric loop on the airlock thermal cover.

1740 GMT (12:40 p.m. EST)

The spacewalkers have completed the cleaning of the Unity node docking surface and performed some inspections of the Quest airlock hatch mechanism.

Pettit, held in place by Bowersox, used sticky tape to blot up dust-like contamination on a space station docking interface, successfully accomplishing the second major priority of their ongoing spacewalk.

Later, Bowersox returned to the airlock to rotate the handle on the outer hatch while the hatch was in the open position. He reported no problems compared to the hang up experienced this morning while trying to open the hatch. It is believed the fabric covering the hatch was to blame for causing its opening mechanism to hang up. The astronauts have been asked -- when the return to the airlock to end the EVA -- to cut off a loop of fabric to prevent any future hang ups when the hatch is being opened.

The spacewalkers are mounting a floodlight on the station's right-side solar array truss segment and still need to complete an ammonia coolant system check.

Meanwhile, the countdown continues at Kennedy Space Center for tomorrow's launch of space shuttle Columbia. Liftoff is scheduled for 10:39 a.m. EST, the opening of a 2.5-hour launch window extending to 1:09 p.m. EST. Mission managers met this morning and formally cleared the fuel line bearing issue.

1510 GMT (10:10 a.m. EST)

The highest priority task of this space walk has been accomplished. A 75-foot-long set of radiators was deployed from the station's newly installed P1 truss at around 10 a.m. EST (1500 GMT). The operation was started by ground controllers after spacewalkers Kenneth Bowersox and Donald Pettit released a set of launch locks holding the radiator in place.

1255 GMT (7:55 a.m. EST)

EVA begins. Expedition 6 commander Kenneth Bowersox and ISS science officer Donald Pettit switched their spacesuits from station-provided power to internal battery power at 7:50 a.m. EST, marking the start of this 50th spacewalk dedicated to assembly of the International Space Station.

Read a complete preview of the spacewalk.

1246 GMT (7:46 a.m. EST)

Bowersox has finally gotten the airlock hatch open! The spacewalkers will be making an inspection of the hatch to determine what was causing the handle to hang up.

1223 GMT (7:23 a.m. EST)

The spacewalkers are suited up, ready for their excursion and the Quest airlock has been depressurized. But commander Kenneth Bowersox has reported some resistance in his efforts to rotate the handle that opens the outer hatch of the airlock. Mission controllers are discussing what could be hanging up the handle.

Spacewalk preparations have proceeded smoothly over the past few hours. And before that, the station's Mobile Transporter railcar successfully drove from one worksite on the far end of the station's backbone to its home position on S1.

"The MT has relocated to work site 4 and we're driving latches now," mission control radioed at 3:10 a.m. EST. A few moments later the ground told the crew the transporter had been successfully locked in place and "not to worry about that one today."

The robot arm transporter got stranded at work site 7 on the left side of the station's solar array truss in late November. While the problem that initially held up the platform was corrected during a subsequent spacewalk, NASA managers decided to delay moving it back to its original work station until the station crew was available to help out in case of any additional problems.

But today's move, which began at 2:55 a.m. EST, went smoothly and no assistance from Bowersox and Pettit was required. The trip took just 15 minutes.

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WEDNESDAY, JANUARY 15, 2003

Space station commander Kenneth Bowersox and science officer Donald Pettit are gearing up for a planned six-and-a-half-hour spacewalk Wednesday to help deploy a huge radiator panel and to carry out other tasks necessary for ongoing station assembly work.

NASA television coverage will begin at 6 a.m. EST and the two astronauts are expected to float out of the Quest airlock module between 7 a.m. and 7:30 a.m. EST.

Expedition 6 commander Bowersox and flight engineer Nikolai Budarin, a Mir veteran, originally planned to carry out the spacewalk, or EVA, on Dec. 12, one week after the departure of the shuttle Endeavour that carried them into orbit. But a few days earlier, NASA flight surgeons "grounded" Budarin because of an undisclosed medical issue and assigned Pettit to take his place.

Read a complete preview of the spacewalk.

SATURDAY, DECEMBER 7, 2002

Running three days late, the shuttle Endeavour finally glided back to Earth today - just one day before the astronauts would have run out of clean air - leaving a fresh crew behind on the international space station and bringing their three predecessors home after a marathon six-month stay in orbit. Read our full landing story.

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2245 GMT (5:45 p.m. EST)

The astronauts are meeting with their families back at crew quarters at this time. They are said to be in good health but tired.

A post-landing news conference with commander Wetherbee and possibly the rest of the orbiter crew is scheduled for 8:30 p.m. EST. The Expedition 5 crew will not be participating.

Tape interviews with the returning station crew could be available late tonight. However, that is not for certain.

2159 GMT (4:59 p.m. EST)

For the first time in recent memory, the crew did not take the walkaround of the shuttle. Wetherbee did leave the CTV for a time to chat with officials. The transporter is now driving down the runway, headed for the crew quarters several miles away.

2110 GMT (4:10 p.m. EST)

The motorized Crew Transport Vehicle has backed away from Endeavour. It is expected that at least some of the shuttle astronauts will make the traditional walkaround of the Endeavour on the runway shortly.

Later, the astronauts will be driven to Kennedy Space Center's Operations & Checkout Building to be reunited with their families and have dinner.

Endeavour will be towed off the runway to its hangar this evening. The shuttle's next flight is the STS-115 mission in May that will deliver the next set of power-generating solar wings to the space station.

2045 GMT (3:45 p.m. EST)

Before climbing out of his seat on the flight deck, commander Jim Wetherbee had this conversation with Mission Control:

"Thank you, I do think you folks are the world's best and I really appreciate it to you and all the other teams that worked with us for this whole flight, great job, we really appreciate it," Wetherbee said, a veteran of six shuttle flights since 1990.

"Jim, we really appreciated working with you and all your crew. It was a great flight. You're great to work with. All good things come to those that wait, and we're glad to bring you back to Florida. And I have word that they have a clean desk waiting for you in Building 1," entry flight director Wayne Hale replied.

"Well...thanks a lot Wayne," Wetherbee said haltingly. "I hate to say I'm ready because then it would be recorded, but thanks a lot. Nah, I guess I'm ready."

2037 GMT (3:37 p.m. EST)

Commander Wetherbee now leaving his ship having safely brought Endeavour back to Kennedy Space Center. This was his fifth shuttle landing, more than any other astronaut.

2026 GMT (3:26 p.m. EST)

Three of the seven crew members are now off the shuttle.

2021 GMT (3:21 p.m. EST)

Crew egress from the orbiter is beginning.

2014 GMT (3:14 p.m. EST)

The astronaut support personnel has entered Endeavour to help the crew as well as begin work to prepare the shuttle for its trip to the hangar in a couple of hours.

2007 GMT (3:07 p.m. EST)

Mission Control reports at the time of touchdown, the winds were 9 peaking to 13 knots. From the direction the winds were blowing, the crosswind was only 7 knots -- well below the 15-knot limit.

2005 GMT (3:05 p.m. EST)

The Crew Transport Vehicle -- a modified airport "People Mover" -- has pulled up to the Endeavour's crew hatch for the astronauts to enter. The CTV features beds and comfortable seats for the astronauts to receive medical checks after returning to Earth's gravity from the weightless environment of space.

1959 GMT (2:59 p.m. EST)

Endeavour's three Auxiliary Power Units have been shut down.

1956 GMT (2:56 p.m. EST)

The main engine nozzles have been gimbaled to the "rain drain" position. The body flap has been set. And the astronauts have been given the OK to take off their entry suits.

1949 GMT (2:49 p.m. EST)

The astronauts are going through standard post-landing safing of Endeavour following a smooth touchdown today. The external tank umbilical doors on the shuttle's belly have been opened. The side hatch and drag chute pyrotechnics have been safed, and the landing gear is reported safed. On the runway, workers have arrived with instruments to "sniff" the shuttle's exterior to check for any hazardous vapors.

1947 GMT (2:47 p.m. EST)

Here are the preliminary landing times in Eastern Standard Time and Mission Elapsed Time:

Main Gear Touchdown
2:37:12 p.m. EST
MET: 13 days, 18 hours, 47 minutes, 25 seconds

Nose Gear Touchdown
2:37:23 p.m. EST
MET: 13 days, 18 hours, 47 minutes, 36 seconds

Wheels Stop
2:38:25 p.m. EST
MET: 13 days, 18 hours, 48 minutes, 38 seconds

1942 GMT (2:42 p.m. EST)

Post-landing safing of Endeavour is underway by the astronauts following touchdown today.

1938 GMT (2:38 p.m. EST)

WHEELS STOP. Endeavour has safely shuttled the Expedition 5 crew back to Earth after a half-year spent living and working about the international space station.

1937 GMT (2:37 p.m. EST)

TOUCHDOWN! Main gear touchdown. Nose gear touchdown. Drag chute deployed. Endeavour rolls out on Runway 33 after traveling 5 1/2 million miles over the past 14 days on its 19th trip to space.

1937 GMT (2:37 p.m. EST)

Landing gear down and locked. Standing by for touchdown on Kennedy Space Center's Runway 33.

1936 GMT (2:36 p.m. EST)

Field in sight. Commander Wetherbee can see the runway as he pilots Endeavour to landing at Kennedy Space Center. The shuttle descending at a rate seven times steeper than that of a commercial airliner.

1935 GMT (2:35 p.m. EST)

Two minutes to landing of Endeavour. Mission Control reports Wetherbee has the shuttle right on course.

1934 GMT (2:34 p.m. EST)

Endeavour is in the Heading Alignment Cylinder, an imaginary circle to align with Runway 33. The crew is piloting the shuttle through a 294-degree right-overhead turn.

1933 GMT (2:33 p.m. EST)

Commander Jim Wetherbee has taken manual control of Endeavour. This is the fifth time Wetherbee will have landed the space shuttle, more than any other astronaut.

And the sonic booms have been heard in KSC area, announcing the shuttle's arrival.

1931 GMT (2:31 p.m. EST)

Now six minutes from landing at the Kennedy Space Center. Mission Control has given the crew a "go" for late drag chute deployment after nose gear touchdown in order to achieve a crosswind landing test. It will be a straight right-hand crosswind of 9 peaking to 14 knots.

1930 GMT (2:30 p.m. EST)

Seven minutes to landing, descending at a rate of 265 feet per second, 86 miles from the runway.

1929 GMT (2:29 p.m. EST)

Air data probes have been deployed from the shuttle's nose to feed air speed, altitude and angle of attack information to the computers for navigation.

1929 GMT (2:29 p.m. EST)

Powerful long-range tracking cameras have spotted Endeavour. Range to the runway 146 miles. Altitude 21 miles.

1928 GMT (2:28 p.m. EST)

Nine minutes to landing. Endeavour is about to make U.S. landfall south of Tampa. Distance from KSC is 220 miles, altitude 25 miles, traveling at Mach 6.

1927 GMT (2:27 p.m. EST)

Touchdown is now 10 minutes away. The shuttle, just a glider during its return to Earth, is expected to land 2,500 feet down the runway at about 195 knots.

1926 GMT (2:26 p.m. EST)

Endeavour remains on the proper track for landing in 11 minutes at Kennedy Space Center.

The Merritt Island tracking station at the Cape, called MILA, has locked on to signal from space shuttle Endeavour. This provides more detailed navigation data for tracking the spaceplane as it streaks to touchdown at Kennedy Space Center. And the TACAN navigation units aboard Endeavour are now receiving data from beacons located at the ground.

1924 GMT (2:24 p.m. EST)

Endeavour is now just off the western tip of Cuba with 560 miles to go to touchdown.

1922 GMT (2:22 p.m. EST)

Now 15 minutes until landing. Endeavour is back over water, flying just to the east of the Yucatan Peninsula. Speed currently Mach 14, at an altitude of 35 miles. Range to the runway about 750 miles.

1921 GMT (2:21 p.m. EST)

Touchdown will occur on Runway 33 at the Kennedy Space Center -- the southeast to northwest strip of the Shuttle Landing Facility. Upon arrival at the heading alignment circle in skies over KSC, commander Jim Wetherbee will make a 294-degree right-overhead turn to align Endeavour with the runway. Touchdown is expected at 2:37 p.m. EST.

The Shuttle Landing Facility was built in 1975. It is 300 feet wide and 15,000 feet long with 1,000-foot overruns at each end. The strip is located about three miles northwest of the 525-foot tall Vehicle Assembly Building.

1919 GMT (2:19 p.m. EST)

Endeavour has made landfall over Central America, less than 1,500 miles to the runway, dropping at 144 feet per second.

1918 GMT (2:18 p.m. EST)

Endeavour is now reversing its bank to the left to further reduce speed.

1917 GMT (2:17 p.m. EST)

Now 20 minutes from landing. Endeavour is 1,900 miles to the runway with an altitude of 43 miles, traveling at Mach 21.

1914 GMT (2:14 p.m. EST)

The shuttle is now crossing the equator above the Pacific. Time to touchdown is 23 minutes. Speed just under Mach 24.

1911 GMT (2:11 p.m. EST)

Endeavour is beginning the first in a series of banks to scrub off speed as it plunges into the atmosphere. These turns basically remove the energy Endeavour built up during launch. This first bank is to the right.

1908 GMT (2:08 p.m. EST)

The Expedition 5 crew of commander Valery Korzun, NASA science officer Peggy Whitson and flight engineer Sergei Treschev are feeling the first tugs of gravity since their launch in June. They are strapped into specially-designed reclining seats on the middeck of Endeavour. Mission specialist Mike Lopez-Alegria is also seated downstairs to assist the crew if needed.

1905 GMT (2:05 p.m. EST)

ENTRY INTERFACE. The protective tiles on the belly of Endeavour are now feeling heat beginning to build as the orbiter enters the top fringes of the atmosphere -- a period known as Entry Interface.

The shuttle is flying with its nose elevated 40 degrees, wings level, at an altitude of 400,000 feet, passing over the southern Pacific Ocean, about 4,300 nautical miles from the landing site, at a velocity of Mach 25.

Touchdown is set for 2:37 p.m. EST at Kennedy Space Center in Florida.

1901 GMT (2:01 p.m. EST)

Endeavour is currently above the southern Pacific Ocean, 6,200 miles from the runway, traveling at Mach 25, descending at 680 feet per second.

1857 GMT (1:57 p.m. EST)

Now 40 minutes to touchdown. The shuttle's track home is taking the craft above the Pacific Ocean on northeastward track towards Kennedy Space Center. The shuttle will make landfall above Central America, before heading back over water and skirting to the west of Cuba. Endeavour will arrive in the skies of Florida on the western coast, south of Tampa, and continue across the central portion of the state, flying just south of Orlando. Once in the vicinity of KSC, Commander Wetherbee will perform a wide, sweeping 290-degree right-overhead turn to align with Runway 33 -- the southeast to northwest three-mile strip.

1854 GMT (1:54 p.m. EST)

All three Auxiliary Power Units are running to supply pressure to the shuttle's hydraulic systems, which in turn move Endeavour's aerosurfaces and deploy the landing gear. One unit was started prior to the deorbit burn; the others just a few moments ago. The units are only activated during the launch and landing phases of the shuttle mission.

1847 GMT (1:47 p.m. EST)

Now 50 minutes to touchdown. Today's landing will be the 61st to occur at Kennedy Space Center in the history of space shuttle program. Dating back to May 1996, this will mark the 39th of the last 44 shuttle missions to land in Florida. KSC is the most used landing site for the shuttle. Edwards Air Force Base in California has seen 49 landings and White Sands in New Mexico supported one.

1840 GMT (1:40 p.m. EST)

Onboard guidance is maneuvering Endeavour from its heads-down, tail-forward position needed for the deorbit burn to the reentry configuration of heads-up and nose-forward. The nose also will be pitched upward 40 degrees. In this new position, the black tiles on the shuttle's belly will shield the spacecraft during the fiery plunge through the Earth's atmosphere with temperatures reaching 3,000 degrees F. Endeavour will begin interacting with the upper fringes of the atmosphere above the South Pacific in about 25 minutes.

1834 GMT (1:34 p.m. EST)

DEORBIT BURN COMPLETE. Endeavour has successfully completed the deorbit burn, committing the shuttle for its journey back to Earth. The OMS engines have worked, no trim maneuver required.

Landing is scheduled for 2:37 p.m. EST at Kennedy Space Center in Florida to cap Endeavour's two-week flight and the 185-day voyage of the Expedition 5 space station resident crew.

1831 GMT (1:31 p.m. EST)

DEORBIT BURN IGNITION. Flying upside down and backwards above the Indian Ocean, Endeavour has begun the deorbit burn. The firing of the two Orbital Maneuvering System engines on the tail of the shuttle will last nearly three minutes, slowing the craft by over 330 feet per second to slip from orbit.

The retro-burn will send Endeavour towards a touchdown at 2:37 p.m. EST on a runway just a few miles from the Kennedy Space Center launch pad where the shuttle lifted off 14 days ago.

1827 GMT (1:27 p.m. EST)

Pilot Paul Lockhart is activating one of three Auxiliary Power Units -- APU No. 2 -- in advance of the deorbit burn, now four minutes away. The other two APUs will be started later in the descent to provide pressure needed to power shuttle's hydraulic systems that move the wing flaps, rudder/speed brake, drop the landing gear and steer the nose wheel. NASA ensures that at least one APU is working before committing to the deorbit burn since the shuttle only needs a single unit to make a safe landing.

1814 GMT (1:14 p.m. EST)

Endeavour is maneuvering to the deorbit burn attitude. The shuttle will be flying upside-down and backwards with its tail pointed in the direction of travel. The shuttle's vent doors have been closed and final configuring of the onboard computers has been completed.

The upcoming burn will be the first time the right OMS engine has been used since launch when a stuck ball valve was noted. The crew has procedures onboard to deal with an overburn during the deorbit in the unlikely event that happens.

1802 GMT (1:02 p.m. EST)

GO FOR THE DEORBIT BURN! With a favorable weather forecast, entry flight director Wayne Hale has given space shuttle Endeavour's astronauts the "go" to perform the deorbit burn at 1:31:33 p.m. EST for return to Earth.

The upcoming two-minute, 56-second retrograde burn using the twin orbital maneuvering system engines on the tail of Endeavour will slow the shuttle's velocity just enough to slip the craft out of orbit and begin the plunge back into the atmosphere.

Endeavour is headed to a landing at 2:37 p.m. EST on Runway 33 at KSC -- four days later than planned because of bad weather in Florida. But conditions have finally improved and NASA will get its desired landing at the shuttle's home port.

1800 GMT (1:00 p.m. EST)

Spaceflight Meteorology Group is reporting a favorable trend on the crosswinds. The latest landing time forecast is calling for scattered clouds at 4,000 and 25,000 feet and crosswinds no greater than 15 knots, which is right at the limit. Rominger is reporting the winds are steady and isn't having any problem handling the Shuttle Training Aircraft. Flight director Wayne Hale will be polling his team before giving the "go/no go".

1756 GMT (12:56 p.m. EST)

Rominger is reporting that the winds are steady all the way down to the runway. Entry flight director will be getting another full weather briefing momentarily before making the "go/no go" call for the deorbit burn. Ignition time of the burn, should it be approved, is 1:31:33 p.m. EST.

1755 GMT (12:55 p.m. EST)

NASA astronaut Kent Rominger, having switched from the T-38 to the Shuttle Training Aircraft earlier this morning, continues his weather reconnaissance flights around the Kennedy Space Center runway.

The STA has flying characteristics that mimic the shuttle. So his observations on how the crosswinds are affecting the approach and landing will be key to the decision whether Endeavour will be allowed to come home on the first landing opportunity today.

1751 GMT (12:51 p.m. EST)

Pilot Paul Lockhart has completed the Auxiliary Power Unit prestart, which positions switches in the cockpit in the ready-to-start configuration. One of the three APUs will be started prior to the deorbit burn.

1749 GMT (12:49 p.m. EST)

A steering check of the Endeavour's twin orbital maneuvering system engines on the tail of the shuttle has been completed. The deorbit burn engine firing will begin at 1:31:33 p.m. EST and last for two minutes and 56 seconds.

1733 GMT (12:33 p.m. EST)

The crew has been given the approval to begin their "fluid loading" protocol to drink large amounts of liquids to help in readapting to Earth's gravity, a precursor to today's landing. However, crosswinds are fluctuating above and below the limit. The forecast for landing time puts the winds right at or above the 15-knot cutoff. So this will be a close call today. The following orbit into KSC expects to have less wind.

1714 GMT (12:14 p.m. EST)

Weather pilot Kent Rominger is now reporting light to moderate turbulence below 1,000 feet during final approach to the Shuttle Landing Facility.

1703 GMT (12:03 p.m. EST)

Forecasters in Mission Control report that clouds aren't the main concern right now. The crosswinds at the shuttle runway are now 18 knots -- and out of limits. It is predicted that as the afternoon rolls on the winds will ease. So the second of the two landing opportunities of the day at KSC is looking more promising -- with touchdown at 4:15 p.m. EST.

1656 GMT (11:56 a.m. EST)

Mission Control has given commander Jim Wetherbee the Deorbit and Landing Preliminary Advisory Data update. The deorbit burn is now targeted to begin at 1:31:33 p.m. EST and last for two minutes and 56 seconds. That will put Endeavour on course for its hour-long glide back to Earth. Once in the skies off Kennedy Space Center, Wetherbee will pilot the shuttle around a 290-degree right overhead turn to align with Runway 33 for touchdown at 2:37 p.m. EST.

1632 GMT (11:32 a.m. EST)

Now two hours away from the deorbit burn. Nothing new on the weather. Clouds and crosswinds still to be watched. Endeavour's computers are now running on the entry software package. In the next hour, the crew will begin suiting up. And then in about 90 minutes, entry flight director Wayne Hale is scheduled to make the final "go/no go" decision on the deorbit burn.

1552 GMT (10:52 a.m. EST)

Endeavour's clam shell-like payload bay doors have been closed and locked in preparation for today's fiery descent into Earth's atmosphere and 2:37 p.m. EST landing at Kennedy Space Center. This is the third time in four days of landing attempts that the doors have been closed.

Mission Control will soon give commander Jim Wetherbee a "go" to transition Endeavour's onboard computers from the OPS-2 software used during the shuttle's stay in space to OPS-3, which is the software package that governs entry and landing.

And Endeavour will be maneuvering to a new orientation in space to improve the communications link with NASA's orbiting data relay satellites.

1548 GMT (10:48 a.m. EST)

Endeavour's port payload bay door is now swinging shut as the astronauts work a few minutes ahead of their timeline today.

1537 GMT (10:37 a.m. EST)

Entry flight director Wayne Hale just received another weather briefing. Conditions are currently observed "go" at Kennedy Space Center with some clouds at 3,000, 5,000 and 9,000 feet and a crosswind of 7 knots. The landing time forecast remains unchanged with a concern of a broken deck of clouds that would constitute a ceiling at 3,000 feet. The clouds in question -- located to the northeast and drifting in the direction of the Cape -- appear to be dissipating as they get closer to the shoreline.

In any event, deorbit preparations will continue this morning. The stage is set for closing Endeavour's payload bay doors in about 15 minutes.

1502 GMT (10:02 a.m. EST)

NASA astronaut Kent Rominger is flying weather reconnaissance once again at Kennedy Space Center. He is currently piloting a T-38 jet trainer. The latest report is some scattered clouds to the northeast of Kennedy Space Center with about 30 percent sky coverage.

1430 GMT (9:30 a.m. EST)

Even though Endeavour has enough consumables and supplies to safely stay orbit until Sunday, NASA plans to bring the shuttle back to Earth at either Florida's Kennedy Space Center or California's Edwards Air Force Base today. Entry flight director Wayne Hale explains the reasoning behind that decision:

"The real hard stop in all of this is the lithium hydroxide canisters that remove the carbon dioxide from the air the shuttle crew breathes," he said. "Late Sunday night, we would be out of lithium hydroxide canisters.

"That being said, we implement our standard plan. The day before we run out of the wherewithal to stay on orbit, we would land, preferably in Florida but at the other site (if necessary), whichever one is the best. So in that regard, we have called up Edwards Air Force Base, they know that we are still going to try to plan to land at the Kennedy Space Center but if we don't get enough good weather to land in Florida, we'll land in California.

"We feel very confident we can try for three (landing attempts) in a row, which would allow us to do the first two Kennedy opportunities, followed by the first California opportunity and still have an emergency reserve that if something should go wrong would allow us to land Sunday. So we'll try three opportunities and if we had some strange circumstances, we might even try four."

Endeavour's landing was scrubbed on Wednesday, Thursday and Friday because of poor weather at the desired landing site at Kennedy Space Center. Landing at Edwards means the shuttle while have to be mounted atop a 747 jet for a cross-country ferry flight at the cost of $1 million and at least one week's delay to processing for Endeavour's next launch.

"We are not at the level of a commercial airliner, where we can fly with much reduced ceilings and in rain," Hale said. "Perhaps someday we'll have a spacecraft that can do those kinds of things.

"But the fact of the matter is, the shuttle is an unpowered glider and we get one shot at landing. It is rather more difficult to land than most other aircraft and so we want to make sure we give the commander, who's coming back from two weeks in weightlessness and all that that entails, the very best shot at making a safe landing."

1407 GMT (9:07 a.m. EST)

For a record fourth day in a row, NASA is trying to get space shuttle Endeavour back on Earth. Faced with continued bad weather at the preferred landing site at Kennedy Space Center in Florida, the shuttle has remained in space for three extra days.

The news this morning from the Spaceflight Meteorology Group in Mission Control is generally encouraging for a Florida homecoming this afternoon, but there are still a couple of weather concerns.

For the first landing opportunity -- beginning with a deorbit burn at 1:32 and touchdown at 2:37 p.m. EST -- there is a slight concern for low clouds at 3,000 feet and winds from 030 degrees 12 peak 18 that would give a crosswind right at the 15 knot limit.

The second KSC opportunity one orbit later -- deorbiting at 3:09 and touchdown at 4:15 p.m. EST -- appears to be better with easing winds but still with the chance of a broken deck of low clouds.

NASA has activated the backup landing site at Edwards Air Force Base in California today. If Florida weather prevents a landing at either KSC opportunity, then the plan is to divert Endeavour to the California high desert -- for a 5:45 p.m. EST landing -- where the conditions are expected to be ideal.

The next weather briefing will occur in about 90 minutes prior to the closing of Endeavour's payload bay doors, which is scheduled for 10:52 a.m.

Read our earlier status center coverage.