BY JUSTIN RAY

Follow the preparations to return America's space shuttle fleet to flight as we chronicle work to ready Discovery for its blastoff to the international space station.

THURSDAY, JULY 21, 2005

Tropical Storm Franklin formed in the Atlantic near the Bahamas Thursday, giving NASA something else to worry about as crews prepare Discovery for the space shuttle return to flight mission scheduled to blast off Tuesday from Kennedy Space Center.

Weather tracking models were in wide disagreement tonight about where Franklin is headed. Some take the growing storm generally northward before making a lazy clock-wise loop off the Florida coast. Others actually bring the system across the Sunshine State, with landfall just south of Cape Canaveral.

As of 8 p.m. EDT, the National Hurricane Center reported Franklin was packing winds of 45 mph. NASA's rules say Discovery would have to be unplugged from pad 39B and returned to protective Vehicle Assembly Building if winds are forecast to reach 69 mph at the launch site. It normally takes 40 hours to ready a shuttle for rollback once the decision is made. The 4.2-mile trek from the pad to the VAB lasts 8 to 10 hours.

Mission managers will be receiving weather briefings to assess the situation and make the call whether it is necessary to get the shuttle off its seaside launch complex.

1905 GMT (3:05 p.m. EDT)

A developing tropical system southeast of Cape Canaveral is beginning to capture NASA's attention today. The National Hurricane Center is closely monitoring the tropical wave for potential formation into a tropical storm later today. A NASA spokesman says the agency is "starting to keep an eye on it, but it's not a threat yet" for Discovery sitting on launch pad 39B.

Meanwhile, the astronauts will be heading back to Kennedy Space Center from Houston on Friday morning. They plan to make a statement to the press at 11 a.m. EDT at the Shuttle Landing Facility. The countdown is slated to begin at 12 noon EDT on Saturday.

We have updated the launch windows chart, the master flight plan page, the mission quicklook and launch events timeline to reflect the new launch date.

WEDNESDAY, JULY 20, 2005

Troubleshooters may have found the cause of the fuel sensor malfunction that grounded the shuttle Discovery last week. Additional tests are planned, but the analysis to date, along with a proposed wiring modification, prompted NASA managers today to forego another fueling test and to press ahead instead for a launch attempt Tuesday at 10:39 a.m. EDT (1439 GMT). Read our full story.

0031 GMT (7:31 p.m. EDT Wed.)

LAUNCH DATE SET! Space shuttle Discovery will make its next launch attempt on Tuesday. Liftoff time will be 10:39 a.m. EDT, the middle of a 10-minute window.

A grounding problem in the sensor wiring is being tracked down. Technicians will swap the engine cutoff sensor No. 2 and sensor No. 4 electronics. Sensor 2 is the one that gave faulty readings on the first launch try. A fueling test will not be conducted. Engineers will monitor the system's performance during the actual launch countdown.

The three-day count will begin on Saturday.

We'll have a full report tonight.

0012 GMT (7:12 p.m. EDT Wed.)

The meeting has just concluded a short time ago. The news conference to announce the plans for Discovery is coming up in about 15 minutes.

2258 GMT (6:58 p.m. EDT)

The post-MMT meeting news conference is now expected to start no sooner than 7:30 p.m. EDT.

2140 GMT (5:40 p.m. EDT)

The Mission Management Team is meeting right now to debate the progress of troubleshooting the fuel sensor problem on Discovery and the future plans for getting the shuttle ready to launch as early as Tuesday. A news conference will be held once the meeting wraps up, probably after 7 p.m. EDT.

Meanwhile, sistership Atlantis' departure from its hangar has been scrubbed today to replace one of the landing gear tires. The shuttle was supposed to make the quarter-mile trip from the orbiter processing facility bay to the Vehicle Assembly Building this morning for mating with an external fuel tank and solid rocket boosters. But concerns with a tire pressure gauge has prompted the removal and replacement of the left-hand nose gear tire on Atlantis before the shuttle leaves the hangar. The move to the VAB could occur overnight, NASA says. Atlantis is being prepped to launch in September to haul supplies to the space station and conduct more shuttle demonstration tests as part of the second post-Columbia mission.

MONDAY, JULY 18, 2005

NASA managers Monday told the shuttle launch team to gear up for a possible attempt to launch Discovery next Tuesday if troubleshooters can either fix the fuel sensor problem that grounded the ship last week or gather enough data to prove it won't affect other sensors this time around. Read our full story.

2221 GMT (6:21 p.m. EDT)

Testing of the engine sensor system continues. NASA is examining options to fuel the external tank to perform additional testing under super-cold temperatures. That fueling test could occur as early as next Tuesday. Management team chairman Wayne Hale says it isn't clear whether the team could complete the testing they need to do during the countdown and launch on Tuesday, too. For now, efforts will continue to find the source of the glitch over the next couple of days before pressing ahead with a fueling test.

2153 GMT (5:53 p.m. EDT)

The briefing start time is now targeted for 6:15 p.m.

2100 GMT (5:00 p.m. EDT)

The management team meeting is still underway, so the news conference will be delayed beyond 5:30 p.m. EDT.

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

Discovery's seven astronauts are making preparations to leave Kennedy Space Center and return to Houston for a one-day training refresher course in their launch and landing simulator, a NASA spokesman says.

Meanwhile, engineers are meeting at this hour to discuss ongoing testing of the shuttle's engine cutoff sensor system. The review will lead into the Mission Management Team meeting at 3:30 p.m. EDT this afternoon. A news conference is scheduled for 5 or 5:30 p.m. EDT for NASA to offer a progress report.

SUNDAY, JULY 17, 2005

After a long weekend of troubleshooting, engineers have not found an obvious problem that might explain why one of four hydrogen fuel sensors failed to operate properly during the shuttle Discovery's aborted countdown Wednesday.

Among a variety of options now on the table, sources said, is another fueling test, either a stand-alone exercise or a tanking test conducted as part of an actual launch countdown, to further isolate the problem. But as of this writing, those are merely options on the table for discussion and no such decisions have been made.

Read our full story.

2220 GMT (6:20 p.m. EDT)

"Troubleshooting continues at launch pad 39B," NASA spokesman Jessica Rye said in a 6 p.m. EDT report tonight. "At this point, there is no indication of why the liquid hydrogen sensor No. 2 failed its pre-launch checkout on Wednesday during the launch countdown."

Discovery's seven astronauts remain at Kennedy Space Center awaiting the launch to be rescheduled.

SATURDAY, JULY 16, 2005

Engineers working inside the shuttle Discovery's cramped engine compartment this weekend have not yet found any obvious signs of trouble that might explain what caused one of four fuel sensors to operate improperly during last Wednesday's aborted countdown. Read our full story.

1920 GMT (3:20 p.m. EDT)

Today's Mission Management Team meeting is scheduled to get underway in a few minutes. NASA officials are planning daily MMT conferences to review the status of the fuel sensor troubleshooting work. A news briefing is not planned today, however.

1545 GMT (11:45 a.m. EDT)

Space shuttle Discovery commander Eileen Collins gave this statement today:

"My crew will remain in quarantine for the near future, maintaining our proficiency for this mission. We are keeping in close touch with the troubleshooting plan; we have confidence that the best people are working it. In fact, the plan our engineers have put together is impressive, and we are very proud of the work they are doing!

"While the launch delay is disappointing, we have strong confidence that the mission will launch safely and successfully, and we fully support our NASA leadership for taking the time required to understand the problem. We thank all of you for hanging with us!"

FRIDAY, JULY 15, 2005

Engineers are working around the clock and through the weekend, putting on a "full-court press" to recreate, isolate and eliminate the fuel sensor problem that grounded the shuttle Discovery Wednesday, NASA officials said late today. Read our full story.

1825 GMT (2:25 p.m. EDT)

Launch of the shuttle Discovery is on hold until late next week at the earliest, NASA officials said today, to give engineers time to fully troubleshoot the fuel level sensor problem that grounded the spaceplane Wednesday. Read our full story.

1755 GMT (1:55 p.m. EDT)

Launch of space shuttle Discovery will be delayed until at least "late next week," NASA announced a short time ago. The seven astronauts plan to depart Kennedy Space Center and return to their home base near Houston tonight or tomorrow. Efforts to isolate the engine cutoff sensor problem and fix it continue. NASA officials will hold a news conference sometime after 5 p.m. EDT, following the Mission Management Team meeting, provide on update on the troubleshooting efforts and perhaps a better idea when Discovery could fly.

Discovery must launch by July 31 or else wait until September 9 when the next daylight launch period opens.

1425 GMT (10:25 a.m. EDT)

The liquid oxygen and liquid hydrogen reactants for Discovery's three electricity-generating fuel cells have been offloaded, further safing the vehicle so technicians can crawl inside the shuttle's aft engine compartment to gain access to the cabling and the avionics box for the engine cutoff sensor system. NASA spokesman George Diller says the countdown remains in a holding pattern with no firm target launch date. Engineering teams continue to assess troubleshooting plans. A Mission Management Team meeting is planned for this afternoon, with a news conference to follow in the early evening to give an update on the situation.

THURSDAY, JULY 14, 2005

The shuttle Discovery's delayed launch on the first post-Columbia mission is off until at least Sunday, officials said today, and unless engineers find an obvious, simple-to-fix problem in the next day or so, the flight will be put on hold indefinitely. Read our full story.

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

A dozen engineering teams across the country have been assembled to attack this mysterious fuel sensor problem delaying Discovery's launch. Chairman of the mission management team, Wayne Hale, says Sunday is now the earliest liftoff could occur.

"This represents really an optimistic, good-luck scenario," he said, adding that it wasn't very likely the source of the problem can be found in fixed that fast.

The launch countdown has been recycled to the point roughly 48 hours away from liftoff, Kennedy Space Center shuttle processing director Mike Wetmore said.

The three electricity-producing fuel cells under Discovery's payload bay will be drained of their cryogenic reactants tonight, allowing workers access into the shuttle's aft engine compartment where the sensor electronics are located.

The management team will meet at 3:30 p.m. EDT Friday to review the status of the troubleshooting.

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

The Mission Management Team is meeting right now to discuss results of the engine cutoff sensor troubleshooting efforts and options for resolving the problem so Discovery can launch. The ship's external tank was drained of its liquid hydrogen and liquid oxygen propellants by 8:30 p.m. EDT last night after extensive testing on the hydrogen sensors. One of the four sensors gave faulty "wet" readings after the tank was drained.

NASA will hold a news conference no sooner than 2:30 p.m. EDT following the MMT meeting.

WEDNESDAY, JULY 13, 2005

Shuttle engineers are trying pinpoint why one of four critical hydrogen fuel sensors failed a test late in the shuttle Discovery's countdown Wednesday, forcing NASA managers to scrub the agency's long-awaited return to flight. Read our full story.

2040 GMT (4:40 p.m. EDT)

Mission management team chairman Wayne Hale says Saturday is the earliest possible launch opportunity for space shuttle Discovery in the best-case scenario. Engineers are troubleshooting the fuel sensor system to determine where the problem is occurring in the path between the sensor inside the liquid hydrogen tank to Discovery's computer system.

All four of these engine cutoff sensors must be working for the shuttle to be cleared for launch. The sensors are fuel gauges that indicate when hydrogen rocket fuel is running out so the shuttle's main engines can be shut down safely. When one sensor started acting up in today's countdown, Hale said it took "five minutes" to decide a scrub would be ordered.

Draining of the external tank of its half-million gallons of liquid hydrogen and liquid oxygen is underway right now. The launch team is eager to see how the suspect sensor reacts when the hydrogen tank is emptied this evening. The sensor appears to be stuck in the wet setting, Hale said.

A technical team meeting is planned for 8 a.m. EDT Thursday to review the known data. Senior managers will convene a meeting at 12 noon EDT to determine how to go forward.

Although Saturday is the earliest possible launch date, Hale said the schedule will be driven by the technical data and what needs to be done to resolve the problem. Also, servicing the shuttle's three electricity-generating fuel cells will need to be factored in over the next couple of days. A launch opportunity slips 72 hours to do that work.

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

Launch director Mike Leinbach scrubbed today's planned launch of the shuttle Discovery two-and-a-half hours before takeoff time because of data indicating one of four hydrogen fuel flow sensors in the ship's external tank was not operating properly in a test. Read our full story.

1812 GMT (2:12 p.m. EDT)

The launch team is putting together a troubleshooting plan to further examine the engine cutoff sensors that have prompted today's scrub, including tests when the external fuel tank is drained of its propellants. NASA plans a news conference no earlier than 4:30 p.m. EDT.

1804 GMT (2:04 p.m. EDT)

The disappointed astronauts are posing for pictures at the base of the launch pad with Discovery as backdrop.

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

All seven astronauts are getting into the launch pad tower's elevator the ride down to the ground. They are headed back to crew quarters to await word on when the launch will be rescheduled.

1750 GMT (1:50 p.m. EDT)

The problem involves the engine cutoff sensors that serve as fuel gauges in the external tank.

"We really don't want the engine to be running at high speed and suddenly run out of fuel. That can lead to a devastating breakdown of the engine, even uncontained failure of the engine if that should happen. Therefore, we have four sensors on the vehicle and it requires two of those to detect a low-level fuel in order to cut off the engines early before they would run out. This only comes into play in special conditions on the ascent, not a nominal ascent, so it's essentially a backup for a backup situation," astronaut Dave Wolf said.

"Even though the odds of needing this sensor are low, very low, in the proper spirit of safety to any really feasible or projectable failure we want a full system, certainly at the point of launch."

1743 GMT (1:43 p.m. EDT)

"The vehicle, the ECO sensors, for some reason did not behave today, so we are going to have to scrub this launch attempt. So once we develop our scrub turnaround plan we'll get that back to you. I appreciate all we have been through together, but this one is not going to result in a launch attempt today," launch director Mike Leinbach radioed Discovery commander Eileen Collins in announcing the scrub.

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

The astronauts are beginning to climb out of Discovery following today's scrub. Again, the launch has been postponed due to a problem with fuel sensors aboard the shuttle.

1734 GMT (1:34 p.m. EDT)

There is no word how long the delay will last and when Discovery's launch could be rescheduled. NASA has through July 31 to launch Discovery or else wait until September 9 due to the need to lift off and separate the external tank in daylight.

1733 GMT (1:33 p.m. EDT)

Launch director Mike Leinbach just radioed the Discovery crew to say the problem with the fuel sensors means the shuttle cannot fly today. Engineers need to assess this problem before clearing the orbiter for flight.

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

SCRUB! Today's launch has been scrubbed for today due to a problem with the ECO engine cut-off fuel sensors. A problem with these sensors was noted during the fueling tests on Discovery earlier this spring.

1730 GMT (1:30 p.m. EDT)

The engineering team is looking a problem with the liquid hydrogen fuel-level sensors on the shuttle.

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

None of the weather rules are being broken now. The current conditions have improved and the cumulus and anvil cloud rules are no longer violated.

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

Astronaut Wendy Lawrence, mission specialist No. 4, has crawled through the hatch. She will take the middeck's center seat.

Lawrence is a three-time shuttle flier. Read her biography here.

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

Japanese astronaut and Discovery's mission specialist No. 1, Soichi Noguchi, is climbing to the flight deck aft-right seat.

Noguchi will be making his first flight into space on STS-114. Read his biography here.

1708 GMT (1:08 p.m. EDT)

A check of the current weather conditions shows the cumulus and anvil cloud rules are being violated right now. The weather officer keeps shuttle managers updated on the launch rules and whether conditions would break that criteria throughout the countdown.

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

Mission specialist No. 3 Andy Thomas is aboard Discovery now. He is positioned closest to the hatch in the left seat on the middeck.

Thomas is the most experienced space traveler of Discovery's crew. He spent four months living aboard the Russian space station Mir in 1998, plus flew shuttle missions in 1996 and 2001. Read his biography here.

1651 GMT (12:51 p.m. EDT)

Now three hours from the planned launch time. The chief worry today is the local weather conditions at Kennedy Space Center. Storm moved through a short time ago, although blue skies have since returned. The official launch forecast has worsened from a 60 percent chance of acceptable conditions at liftoff time to 40 percent.

"High pressure is building in over the Western Atlantic. On launch day, the high pressure ridge will remain north of KSC causing southeasterly flow over the area. Morning coastal showers are expected, and possibly thunderstorm activity over KSC as the sea breeze develops during the late morning/early afternoon, but the sea breeze should migrate inland by launch time," the launch weather officer reported.

"Still, there is a threat the storms associated with the sea breeze will be within 20 nautical miles of the Shuttle Landing Facility at launch time, causing a concern for Return to Launch Site (RTLS) weather. Additionally, upper level winds from the north-northwest have increased our concern for anvils from thunderstorms migrating into the area; therefore, the probability of KSC weather prohibiting launch increased to (60%)."

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

Pilot Jim Kelly is the next crewmember to enter the shuttle. He is making his way to the flight deck's front-right seat.

Kelly has one previous shuttle flight to his credit. Read his biography here.

1644 GMT (12:44 p.m. EDT)

Now climbing through the hatch is mission specialist No. 5, Charlie Camarda. He is assigned the right seat on the middeck.

Camarda is a spaceflight rookie, Read his biography here.

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

As shuttle commander, Collins is the first astronaut to board the shuttle. She is taking her forward-left seat on the flight deck.

Collins has flown in space on three earlier missions, becoming the first woman shuttle pilot and commander. Read her biography here.

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

Commander Eileen Collins has made her way across the catwalk-like Orbiter Access Arm to the White Room positioned against the side of Discovery. The closeout crew is helping her don other survival gear.

1629 GMT (12:29 p.m. EDT)

The Discovery astronauts have reached the 195-foot level of the tower.

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

Discovery's crew arrived at launch pad 39B at 12:26 p.m. The AstroVan just came to a stop on the pad surface near the Fixed Service Structure tower elevator that will take the seven-person crew to the 195-foot level to begin boarding the shuttle this afternoon.

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

Leaving the rest of the convoy behind, the AstroVan has driven through the pad entrance gate and up the ramp to the pad surface.

1622 GMT (12:22 p.m. EDT)

The "go" has just been given for the astronauts to continue the drive to pad 39B for boarding Discovery.

1620 GMT (12:20 p.m. EDT)

The crew has been stopped short of the pad while officials verify it is safe to proceed up to Discovery given the weather conditions.

1616 GMT (12:16 p.m. EDT)

The AstroVan is now passing the tourist observation deck along the crawlerway near pads 39A and 39B. The astronauts are being escorted by KSC security personnel and a low-flying helicopter.

1611 GMT (12:11 p.m. EDT)

The AstroVan is passing the 52-story Vehicle Assembly Building where Discovery was mated to its external tank and solid rocket boosters. Some reporters across the street at the press site are braving the weather and going outside to wave at the convoy as it passes by, which is a launch day tradition to say farewell and good luck to the astronaut crews.

1601 GMT (12:01 p.m. EDT)

Led by commander Eileen Collins, the Discovery astronauts have emerged from the Kennedy Space Center crew quarters to board the shiny silver AstroVan for the 7-mile ride from the Industrial Area to launch pad 39B on the edge of the Atlantic Ocean. Loud cheers erupted from KSC employees as the crew made their way to the AstroVan.

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

T-minus 3 hours and counting. The countdown has resumed on scheduled from this planned three-hour built-in hold. Clocks will now tick down to T-minus 20 minutes when the next hold is planned. A final hold is scheduled at the T-minus 9 minute mark to synch up with the 3:50:53 p.m. EDT precise launch time.

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

The large press corp. is seeking shelter as thunder and lightning rumble across Kennedy Space Center in this storm.

1548 GMT (11:48 a.m. EDT)

It is beginning to rain here at the Complex 39 press site about 3.5 miles from the pad. The west sky is a solid gray.

1539 GMT (11:39 a.m. EDT)

"Everything is proceeding on schedule. There is nothing significant at the moment in work in the countdown. Most of our engineering channels are quiet. So we're very optimistic that, weather permitting, we'll have a launch at 3:51 this afternoon," NASA launch commentator George Diller says.

1537 GMT (11:37 a.m. EDT)

The seven astronauts have donned their day-glow orange launch and entry partial pressure spacesuits. After final adjustments and pressure checks, the crew plans to depart the suit-up 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 39B. We expect to see the crew walk out of the O&C Building around 12 noon EDT.

1532 GMT (11:32 a.m. EDT)

The navigation systems and homing beacon at the Shuttle Landing Facility runway here at Kennedy Space Center have been activated in the unlikely event Discovery has to make an emergency return just after liftoff.

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

The pre-launch astronaut weather briefing is underway. The commander, pilot and flight engineer received an update on conditions predicted at runways here at Kennedy Space Center, on the U.S. West Coast and the trans-Atlantic abort landing sites in the event a problem forced Discovery to abort the mission and make an emergency return to Earth following liftoff.

For STS-114, a new overseas landing site has been activated in Istres-le-Tube, France. This locale replaces Ben Guerir, Morocco. The other two TAL sites continue to be Moron and Zaragoza, Spain.

The Abort Once Around, or AOA, sites are California's Edwards Air Force Base and White Sands, New Mexico.

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

The rainshowers and increasing cloud cover over Kennedy Space Center seem to be developing at a vigorous rate this morning. Radar shows several showers within 20 miles of the shuttle landing strip, which would violate the emergency landing criteria. Discovery won't be permitted to lift off if the weather is unacceptable at the runway in case the shuttle has to abort the mission in the first minutes of flight and return to KSC.

1510 GMT (11:10 a.m. EDT)

The water tank at the pad is being topped off. The water will flood the launch pad in the final 16 seconds of the countdown to suppress the sound produced at liftoff.

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

Showers are beginning to develop west of the launch pad, which weather forecasters had expected.

1440 GMT (10:40 a.m. EDT)

The inspection team is responsible for checking Discovery and the launch pad one last time prior to liftoff. The 8-person 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.

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

The Final Inspection Team is on the 255-foot level of the launch pad tower as they begin their checks of Discovery.

1429 GMT (10:29 a.m. EDT)

The six-person Orbiter Closeout Crew has arrived in the White Room on the end of the Orbiter Access Arm catwalk that runs from the launch pad tower to Discovery's crew module. They will make final preparations to ready Discovery for the astronaut's arrival about two hours from now.

1419 GMT (10:19 a.m. EDT)

The Final Inspection Team has been cleared to head for the pad to begin their two-hour observations of the shuttle vehicle. The official fueling completion time was 10:05 a.m.

1415 GMT (10:15 a.m. EDT)

Discovery's seven astronauts are seated around the dining room table in crew quarters for a pre-launch snack. They were awakened at 5:45 a.m. EDT to begin the launch day activities at Kennedy Space Center. Flight engineer Steve Robinson was playing a guitar, which was quite a unique sight.

After a bite to eat, commander Eileen Collins, pilot Jim Kelly and Robinson will receive a briefing on the weather forecast for KSC and abort landing sites in California, New Mexico, Spain and France. Then they will join their crewmates in the suit-up to don the launch and entry spacesuits in preparation for heading to pad 39B around 12 noon EDT.

The launch team is not tracking any technical issues as the countdown continues on schedule to today's liftoff time of 3:51 p.m. EDT. The only concern right now is the weather. Forecasters say there's a 60 percent chance of acceptable conditions at launch time.

1410 GMT (10:10 a.m. EDT)

Discovery's external fuel tank is now full with 528,000 gallons of super-cold liquid oxygen and liquid hydrogen.

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 will be dispatched to the pad to perform their jobs. The closeout crew will ready Discovery's crew module for the astronauts' boarding in a couple of hours; and the inspection team will give the entire vehicle a check for any ice formation following fueling.

1407 GMT (10:07 a.m. EDT)

The MILA tracking station here at Merritt Island has aligned its communications antennas with the launch pad and initial communications checks with the Air Force-controlled Eastern Range have been performed in the past hour. Also, the pre-flight calibration of Discovery's three inertial measurement unit guidance computers began.

1401 GMT (10:01 a.m. EDT)

"We are on schedule for liftoff at 3:51 p.m.," NASA commentator George Diller reports from the firing room in the Launch Control Center.

1345 GMT (9:45 a.m. EDT)

Fueling is wrapping up. Meanwhile, Discovery's seven astronauts will be gathering for a pre-launch snack and photo opportunity in the dining room of crew quarters at 10:15 a.m. That will be followed by a weather briefing and then suitup. The crew will head for launch pad 39B at 12:00 p.m., arriving about 20 minutes later to begin boarding Discovery. The ship's crew compartment hatch should be closed for flight around 1:45 p.m.

1255 GMT (8:55 a.m. EDT)

T-minus 3 hours and holding. Countdown clocks have entered a planned three-hour built-in hold in advance of this afternoon's launch of space shuttle Discovery. This is a standard hold in every shuttle countdown. However, NASA has extended it from the usual two hours to three hours to give the final inspection team more time to complete their ice and debris checks of the shuttle after fueling. The team will be sent to pad 39B to begin their inspections once fueling of Discovery is completed, a little more than an hour from now. Fueling should be finished by now, but it started late because of ground equipment trouble.

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

The approximate three-hour fueling process is now passing the half-way mark. NASA is not reporting any problems with the activities to fill the external fuel tank this morning. Launch of Discovery remains targeted for 3:51 p.m. EDT.

1234 GMT (8:34 a.m. EDT)

After the slow-fill process to load each propellant tank inside external tank to the five percent level, the launch team transitioned to the fast-fill mode at 8:04 a.m. for liquid oxygen and 8:17 a.m. on the liquid hydrogen side. The fast-fill continues until the cryogenic tanks each the 98 percent full mark when the topping phase takes over.

1155 GMT (7:55 a.m. EDT)

T-minus 4 hours and counting. The count has another hour before clocks enter a three-hour planned hold.

1140 GMT (7:40 a.m. EDT)

The latest weather forecast is still predicting a 60 percent chance of acceptable conditions today. Clouds and thunderstorms are the main threats. All three abort landing sites in France and Spain are looking good. But it will be a wait-and-watch situation for the dicy Florida summertime weather at the launch site.

1129 GMT (7:29 a.m. EDT)

The slow-fill mode started for loading the liquid hydrogen into the external tank at 7:23 a.m. EDT. Liquid oxygen slow-fill should start in about 25 minutes.

There are actually two tanks inside the shuttle's orange bullet-shaped tank. The liquid oxygen tank fills the top third of the external tank. It will be filled with 143,000 gallons of liquid oxygen chilled to minus 298 degrees Fahrenheit (minus 183 degrees Celsius). 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 (minus 253 degrees Celsius).

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

The fueling process is being orchestrated by engineers in the safe confines of the Kennedy Space Center's Launch Control Center located about three-and-a-half miles from Discovery at launch pad 39B.

1112 GMT (7:12 a.m. EDT)

Fueling operations are underway! The chilldown thermal conditioning of the propellant lines and Discovery's internal plumbing commenced at 7:11 a.m. EDT. The chilldown preps the systems for the shock from the super-cold cryogenic liquid oxygen and liquid hydrogen fuels that will be pumped into the external tank this morning.

The heater problem appears to be resolved.

1103 GMT (7:03 a.m. EDT)

The repair crew is working at the launch pad to replace the firing package for the primary heater that is failed. There has been no estimate given on how long the work will take or when fueling operations could begin. The fueling should have started over an hour ago.

1055 GMT (6:55 a.m. EDT)

T-minus 5 hours and counting. Clocks continue to tick despite the delay in starting fueling this morning due to a faulty purge heater in ground support equipment at the pad. The countdown is headed to the T-minus 3 hour mark where a three-hour hold is scheduled.

1048 GMT (6:48 a.m. EDT)

Efforts continue to resolve the tank purge heater problem.

1037 GMT (6:37 a.m. EDT)

The faulty purge heater that is delaying fueling this morning is located in a room at the base of launch pad 39B, NASA spokeswoman Jessica Rye says.

1030 GMT (6:30 a.m. EDT)

NASA says fueling can be delayed upwards of two hours or so without impacting the overall countdown to the planned 3:51 p.m. EDT.

1020 GMT (6:20 a.m. EDT)

"The team in the firing room is looking at a ground support equipment heater that is the external tank intertank purge for the gaseous nitrogen. There is a secondary heater. The primary heater is not functioning and we've moved to that secondary heater, which is working fine. A crew will be going out the pad shortly to change out a firing package within that heater. The launch team would like to get the redundancy back prior to (fueling Discovery)," NASA spokeswoman Jessica Rye said.

0955 GMT (5:55 a.m. EDT)

T-minus 6 hours and counting. The countdown has resumed as scheduled after the two-hour built-in hold. But Discovery fueling has been delayed while workers attempt to fix a faulty heater purge in the external tank.

0952 GMT (5:52 a.m. EDT)

Fueling of Discovery have been put on hold this morning while a repair team is dispatched to the launch pad. Technicians have noted the external fuel tank's intertank primary heater purge is not working. A backup heater is being used, but NASA wants both heaters to be working for redundancy.

"The launch control team has decided to send a red crew to the pad to change out a firing package in that primary heater purge area," NASA spokeswoman Jessica Rye said.

Loading of Discovery's fuel tank will begin once the team has completed its work and departed the hazard area around pad 39B.

0930 GMT (5:30 a.m. EDT)

The mission management team has given a "go" to begin fueling shuttle Discovery this morning as planned. NASA is not reporting any significant technical issues. Fueling operations should commence shortly.

Managers convened their "pre-tanking meeting" at Kennedy Space Center a little while ago to review the progress of work at launch pad 39B and the weather before giving engineers approval to begin fueling Discovery. The loading of the shuttle's external fuel tank will take nearly three hours to complete.

0900 GMT (5:00 a.m. EDT)

Members of the news media have descended upon central Florida this week as NASA prepares to launch the first space shuttle mission since Columbia's ill-fated flight two-and-a-half years ago that left the fleet grounded. Read our full story.

0500 GMT (1:00 a.m. EDT)

The countdown clocks resumed ticking at 10:55 p.m. EDT following the planned 12-hour, 55-minute hold at the T-minus 11 hour mark. Final preparations for fueling are underway at launch pad 39B.

Countdown clocks will enter a planned two-hour built-in hold at the T-minus 6 hour mark at 3:55 a.m. EDT. During this time, the team will have a chance to catch up on any work that could be running behind schedule. Also during the hold, the Mission Management Team will meet to review the progress of work and any outstanding issues before giving final approval to begin fueling.

Cryogenic liquid hydrogen and liquid oxygen should start flowing from storage tanks at the pad into Discovery around 5:55 a.m. EDT as the clocks resume at T-minus 6 hours and counting. It will take about three hours to fully fill the giant external tank.

A three-hour hold at T-minus 3 hours starts at 8:55 a.m. EDT -- about the same point that fueling reaches completion. The "ice team" is then dispatched to pad 39B to conduct a thorough inspection of the tank, its foam, the orbiter, solid rocket boosters and ground structures. The team will be looking for any ice or frost formations.

Terminal Count commences at 11:55 a.m. EDT as clocks proceed ticking into the final three hours. Further built-in holds are planned at the standard T-minus 20 and T-minus 9 minute points.

Meanwhile, Discovery's seven astronauts will be awakened at 5:45 a.m. and have breakfast at 6:15 a.m. Donning of the launch and entry spacesuits begins at 11:20 a.m. in advance of departing crew quarters for the pad at 12:00 p.m.

0252 GMT (10:52 p.m. EDT Tues.)

After hours of delay retraction of the rotating service structure is nearing completion.

0212 GMT (10:12 p.m. EDT Tues.)

The rotating service structure has finally started its slow move away from the shuttle vehicle.

0201 GMT (10:01 p.m. EDT Tues.)

A paperwork issue is apparently holding up the rollback of the Rotating Service Structure this evening.

0155 GMT (9:55 p.m. EDT Tues.)

At launch pad 39B we continue to wait for the start of the retraction of the rotating service structure.

0131 GMT (9:31 p.m. EDT Tues.)

During the walkdown inspection of Discovery earlier this evening workers found what appeared to be a small blemish on a blanket covering part of the right orbital maneuvering system pod, a NASA spokesman said. Engineers have concluded this is not an issue and service structure is expected to start moving in the next five minutes.

0125 GMT (9:25 p.m. EDT Tues.)

Still no signs of movement at launch complex 39B. The rotating service structure was to have been retracted several hours ago.

0110 GMT (9:10 p.m. EDT Tues.)

We are still awaiting the retraction of the rotating service structure. The move is expected to begin soon, NASA officials say.

0001 GMT (8:01 p.m. EDT Tues.)

Discovery processing manager Stephanie Stilson has confirmed that a tile carrier panel has been successfully replaced after being damaged by a falling window cover earlier today. Stilson said engineers at the Johnson Space Center would be running an analysis to determine if any structural damage had occurred, although that was considered highly unlikely.

Meanwhile at launch complex 39B first motion of the Rotating Service Structure is expected around 8:30 p.m. The move was delayed to allow the repairs to the carrier panel and for additional inspections to verify there was no further damage.

TUESDAY, JULY 12, 2005
2253 GMT (6:53 p.m. EDT)

The replacement carrier panel has been installed on space shuttle Discovery, replacing the one struck by a falling cockpit window cover. Presumably, the new one has achieved a good fit. NASA is planning a news conference at 7:30 p.m. EDT to update reporters on the situation.

2235 GMT (6:35 p.m. EDT)

NASA Administrator Michael Griffin, saying the space agency has done everything humanly possible to fix the problems that led to the Columbia disaster, told reporters today the shuttle Discovery is "go" for launch Wednesday, weather permitting, on an "utterly crucial" mission.

"I just came from a very interesting mission management team meeting," Griffin said after the management poll to clear Discovery for flight. "The net result of all that is we're go for launch tomorrow, pending weather. We're not really working any significant issues, just working through normal closeouts and hoping the weather gods are kind for tomorrow."

Late today, after Griffin's remarks, engineers were called to launch pad 39B to troubleshoot damage to protective heat shield tiles on Discovery's left-side orbital maneuvering system rocket pod. A protective plastic cockpit window cover somehow fell off and struck a tile-covered panel. The so-called carrier panel protects attachment fittings that hold the rocket pod to the shuttle's fuselage.

Read our full story.

2154 GMT (5:54 p.m. EDT)

The window cover in question is from one of the overhead windows. It fell on its own, not when workers were handling it. The cover was found after it had fallen and hit the orbiter. In addition to the carrier panel that workers plan to replace tonight, engineers are looking for any other damage.

2149 GMT (5:49 p.m. EDT)

NASA expected to know by 7 p.m. if the replacement panel will work and whether launch can proceed tomorrow as planned.

2146 GMT (5:46 p.m. EDT)

The window cover hit the so-called carrier panel around the OMS pod. NASA is taking a new panel to launch pad 39B to replace the one hit by the falling cover. A swap-out would still permit launch tomorrow.

2129 GMT (5:29 p.m. EDT)

One of the space shuttle's protective window covers fell and struck the left Orbital Maneuvering System engine pod on Discovery at launch pad 39B today. Engineers are assessing if any damage was caused by the incident. What this means for tonight's schedule, including retraction of the rotating service structure about 90 minutes from now, remain unclear at the moment.

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

"We've done everything that we know to do," Griffin says.

"Is there something that we don't know about that could bite us? Yes."

1931 GMT (3:31 p.m. EDT)

The mission management team has completed its Launch Minus-1 Day meeting, putting to rest the final remaining issues that were debated overnight.

"We're go for launch tomorrow pending weather," NASA Administrator Mike Griffin says. "We're just hoping the weather gods are good to us tomorrow."

Griffin said he met with the Discovery astronauts and toured the launch pad today. The crew and pad teams are "raring to go."

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

Space shuttle Discovery's communications systems are being activated today as work progresses for tomorrow's planned launch.

"All work continues to go extremely well," NASA test director Jeff Spaulding said this morning.

The fuel cell storage tanks beneath the payload bay were filled with liquid hydrogen and liquid oxygen last evening. That operation was completed successfully, allowing the launch pad to be reopened around 11 p.m. EDT. Spaulding says the shuttle has enough of the cryogenics for launch attempts over the next four days before the fuel cells would have to be topped off, causing a three-day postponement. Discovery has three fuel cells to generate electricity and the astronauts' drinking water during the flight.

Final preparations of the three main engines and filling of the pad's giant sound suppression system water tank occurred overnight.

Also on tap today are functional checks of Discovery's star trackers, activation of the guidance computers known as the inertial measurement units, installation of film in numerous cameras on the launch pad and the last-minute stowing of more astronaut equipment into the crew module.

Rollback of the Rotating Service Structure to expose orbiter Discovery for launch is targeted for 7 p.m. EDT tonight.

"We think weather is going to be good for RSS retract tonight," launch weather officer Kathy Winters said.

Loading of Discovery's external tank with a half-million gallons of rocket fuel could start as early as 5:30 a.m. EDT tomorrow.

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

The shuttle Discovery's countdown is ticking smoothly toward blastoff Wednesday, but forecasters said today the launch likely will hinge on whether afternoon showers move out of the area before the opening of the shuttle's short launch window. Also today, the Columbia families issued a statement of good wishes for Discovery's crew. Read our full story.

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

The Mission Management Team will be meeting today to review the final outstanding issues and verify everything is set for entering the final countdown tonight. NASA Administrator Mike Griffin will hold a news conference following the meeting no sooner than 3 p.m. EDT.

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

T-minus 11 hours and holding. The three-day launch countdown has entered its longest planned hold, this one lasting 12 hours and 55 minutes. Discovery remains in good shape and ready for liftoff tomorrow. Loading of the fuel cell storage tanks was completed last night. The weather forecast has been downgraded slightly to a 60 percent chance of acceptable weather at the 3:51 p.m. EDT liftoff time.

MONDAY, JULY 11, 2005

NASA's mission management team met today to assess the status of shuttle Discovery's launch processing and its readiness to take off Wednesday on the first post-Columbia mission. While the panel cleared most of the open items on the agenda, engineers were asked to work through the night to resolve a few final questions. Read our full story.

2148 GMT (5:48 p.m. EDT)

At launch pad 39B this evening, cryogenic liquid hydrogen and liquid oxygen reactants are being loaded into storage spheres beneath the payload bay of Discovery. That loading work began around 4:30 p.m. EDT, an hour later than planned. The reactants are combined in Discovery's three fuel cells to generate electricity for orbiter systems and drinking water for the astronauts during the 12-day mission.

2132 GMT (5:32 p.m. EDT)

The launch readiness review by the Mission Management Team has concluded. "We had another day of good review," shuttle program manager Bill Parsons says in the pre-launch news conference just getting underway at Kennedy Space Center.

"We're aren't working any major issues. We are ready to go," says Mike Wetmore, director of shuttle processing at KSC.

Launch of Discovery is set to occur at 3:51 p.m. EDT (1951 GMT) Wednesday.

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

T-minus 27 hours and counting. The countdown clock has resumed from a planned four-hour built-in hold.

1530 GMT (11:30 a.m. EDT)

The shuttle Discovery's countdown ticked smoothly through its initial stages today as engineers geared up to load liquid hydrogen and oxygen to power the ship's electricity generating fuel cells. Forecasters, meanwhile, continue to predict a 70 percent chance off acceptable weather at launch time Wednesday. See our full full story.

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

NASA hopes to resume shuttle flights Wednesday, weather permitting, with a three-spacewalk mission to repair the international space station's stabilization system, to deliver critical supplies and equipment and to prove the design defects that led to the Columbia disaster have been corrected. This is our 10-part, 14,000-word report previewing the space shuttle's return to flight. See our full full report.

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

"All our hardware and systems are performing nominally. We're currently tracking no technical issues," said NASA test director Pete Nickolenko. "And our launch team here at Kennedy Space Center and support teams around the world are ready and looking forward to returning the shuttle Discovery to flight, returning to the international space station and safely returning our astronaut crew back home."

1307 GMT (9:07 a.m. EDT)

Discovery's countdown has entered its first built-in hold at the T-27 hour mark. During this four-hour hold preparations will begin for loading liquid oxygen and liquid hydrogen for the shuttle's electricity-generating fuel cells.

Meanwhile, a countdown status briefing is underway at the Kennedy Space Center press site. NASA test director Pete Nickolenko reports the countdown is proceeding smoothly for Wednesday's planned liftoff of space shuttle Discovery. Shuttle weather officer Kathy Winters is still forecasting a 70 percent chance of acceptable conditions for launch. Check back later for a full report.

SUNDAY, JULY 10, 2005
2200 GMT (6:00 p.m. EDT)

COUNTDOWN BEGINS! The first space shuttle launch countdown since Columbia has just commenced at Kennedy Space Center for Wednesday's liftoff of Discovery. The launch team is performing the countdown from the Complex 39 Launch Control Center's Firing Room 3. Controllers were called to their stations 30 minutes ago in preparation for beginning the count.

Clocks stand at T-minus 43 hours and counting. About 27 hours of built-in holds are planned over the next three days leading to liftoff at 3:51 p.m. EDT (1951 GMT) Wednesday from pad 39B.

Over the next 24 hours, key activities include:

• Begin final vehicle and facility close-outs for launch
  
  
• Check out backup flight systems
  
  
• Review flight software stored in mass memory units and display systems
  
  
• Load backup flight system software into Discovery's general purpose computers
  
  
• Remove mid-deck and flight-deck platforms (2 a.m.)
  
  
• Complete preparation to load power reactant storage and distribution system (5 a.m.)
  
  
• Activate and test navigational systems (7 a.m.)
  
  
• Flight deck preliminary inspections complete (10 a.m.)
  
  
• Enter first built-in hold at T-27 hours for duration of 4 hours (10 a.m.)
  
  
• Clear launch pad of all non-essential personnel
  
  
• Perform test of the vehicle's pyrotechnic initiator controllers
  
  
• Resume countdown (2 p.m.)
  
  
• Begin operations to load cryogenic reactants into Discovery's fuel cell storage tanks (3:30 p.m.)

1415 GMT (10:15 a.m. EDT)

NASA engineers made final preparations to start the shuttle Discovery's countdown later today, buoyed by forecasts calling for a 70 percent chance of acceptable weather during the ship's five-minute launch window Wednesday. Read our full story.

1310 GMT (9:10 a.m. EDT)

Launch of Discovery remains on schedule for Wednesday afternoon. Technicians are not working any significant problems. And the weather forecast for launch time predicts a 70 percent chance of acceptable conditions. The percentage for Thursday and Friday, should liftoff be delayed for any reason, is 60 percent favorable.

SATURDAY, JULY 9, 2005

Flying in one day early to dodge Hurricane Dennis, the shuttle Discovery's crew arrived at the Kennedy Space Center this evening to make final preparations for launch Wednesday on the first post-Columbia flight. Read our full story.

2330 GMT (7:30 p.m. EDT)

The early weather outlook for Wednesday's 3:51 p.m. EDT launch opportunity of space shuttle Discovery is generally favorable.

"We should be getting an easterly flow at that time as a result of Hurricane Dennis having passed and moved off," Kennedy Space Center spokesman George Diller said. "That should suppress the formation of thunderstorms during the afternoon, except perhaps initially as the seabreeze front sets up about mid-day or so."

The first detailed weather forecast will released during a countdown status news conference at 9 a.m. EDT Sunday.

2251 GMT (6:51 p.m. EDT)

After addressing the press, the astronauts are headed to the crew quarters in the Operations & Checkout Building. They are adjusting to the mission wake/sleep shifts, so bedtime is coming up in the next couple of hours. Wakeup time on launch morning is 5:45 a.m.

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

Over the next couple of days leading up to launch, the astronauts have a relatively relaxed schedule of reviewing flight plans and spending time with their families.

Sunday will see the crew receive countdown status, weather and payload briefings and perform some inspections of the new shuttle Thermal Protection System repair kits being carried on Discovery.

The final pre-flight medical exams are planned for Monday.

Also, commander Collins and pilot Jim Kelly will fly the Shuttle Training Aircraft on Monday and Tuesday to practice approaches into Kennedy Space Center's runway.

2234 GMT (6:34 p.m. EDT)

The seven crewmembers are coming down the aircraft's stairs. KSC Center Director Jim Kennedy is welcoming the astronauts to Florida.

2232 GMT (6:32 p.m. EDT)

The Gulfstream passenger jet has just rolled to a stop near the shuttle mate-demate structure adjacent to the runway. A massive crowd of photographers and reporters has gathered there to cover this evening's crew arrival. Commander Eileen Collins is expected to make a brief statement shortly.

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

The crew has arrived! Discovery's astronauts just touched down at Kennedy Space Center.

2200 GMT (6:00 p.m. EDT)

"We're definitely looking forward to the launch. It's been a long two-and-a-half years, and it'll be good for all of us to actually fly in space again," Paul Hill, the lead space shuttle flight director for Discovery's mission, said in televised interviews Friday.

"Obviously the first six months or a year after the accident, a lot of our efforts were on the accident investigation and clearly on the cause of the accident and resolving the cause of the accident. As you would expect, a lot of the emotion involved with that surrounded the loss of the seven good folks on Columbia. But as we progressed past that, it came back to focusing on making sure that all of these modifications to the shuttle and our operations are, in fact, ready to fly and that we're ready to have Eileen Collins and her crew trust us and get back on board so they can fly in space."

Hill will orchestrate operations in the shuttle mission control center during the 12-day voyage. Houston takes control of the flight as soon as Discovery lifts off with her seven astronauts.

"Once we got this close to the flight, it became a lot like any other flight. We've got a dangerous thing coming up. It is very important for us to make sure we understand how to do that so we can get these seven folks into space and back safely. And you don't have a lot of time at that point to sit and think about the intimidating nature of the job."

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

As the flight crew flies from Texas to Florida, dodging the stormy weather in the outer fringes of Hurricane Dennis, technicians at launch pad 39B continue readying space shuttle Discovery for Wednesday's liftoff.

The ordnance disconnected as part of precautionary rollback preps Thursday evening were hooked up again overnight. The external doors covering the port and starboard access ports to Discovery's cramped three-level aft engine compartment are being installed today.

"All launch preparations are on schedule," NASA spokesman George Diller says. "Weather associated with Hurricane Dennis has so far not been a factor, and at the launch pad there has been only light rain and moderate wind."

2045 GMT (4:45 p.m. EDT)

Discovery's seven astronauts are en route to the launch site!

Commander Eileen Collins, pilot Jim Kelly and mission specialists Soichi Noguchi, Steve Robinson, Andy Thomas, Wendy Lawrence and Charlie Camarda departed Ellington Field near Johnson Space Center aboard a Gulfstream jet at 4:31 p.m. EDT.

They should touch down at the Kennedy Space Center's shuttle runway around 6:30 p.m. EDT.

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

Commander Eileen Collins and her six crewmates will depart the astronaut home base in Houston at 4:30 p.m. EDT today. Riding in a Gulfstream jet, the crew's flight to Florida's Kennedy Space Center should take about two hours. The astronauts are flying aboard one large jet instead of several two-seater T-38 aircraft to permit greater flexibility in traveling around weather associated with Hurricane Dennis.

Launch preparations remain on schedule for Discovery's liftoff at 3:51 p.m. EDT on Wednesday.

FRIDAY, JULY 8, 2005
2050 GMT (4:50 p.m. EDT)

Discovery's astronauts will fly from Houston to the Cape late Saturday afternoon instead of Sunday morning due to Hurricane Dennis' trek toward the U.S. Gulf Coast. The five-man, two-woman crew is expected to arrive at the Kennedy Space Center runway around 6:30 p.m. EDT (2230 GMT).

We'll provide live reports on this page of the event.

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

Discovery will not be rolled back from the launch pad, NASA officials decided this morning.

"Hurricane Dennis has ended its eastward drift and the primary track is slightly more to the west. Landfall is currently projected at approximately the Florida/Alabama border. The closest point to KSC is forecast to be 270 miles west at 5 p.m. on Saturday," a Kennedy Space Center statement announced.

"The forecast calls for a 15% chance of 40 knot winds at KSC, 1% of 70 knots. The operational forecast shows the worst weather at KSC will occur on Saturday with rain and wind 30-35 knots. The higher wind will continue on Sunday but decrease slightly to 25-30 knots."

Rules call for the shuttle to be moved off its launch pad and returned to the 52-story Vehicle Assembly Building if there's a possibility that winds could exceed a sustained speed of 60 knots (69 mph).

Shuttle ordnanace disconnected last night in preparation for rollback will be reconnected this evening.

Launch of Discovery remains scheduled for 3:51 p.m. EDT (1951 GMT) Wednesday.

"The best weather next week is forecast to be on Wednesday and to a slighly lesser extent on Thursday, but deteriorating on Friday with considerably more afternoon thunderstorm activity," the KSC statement said.

The seven astronauts are expected to arrive at KSC from Houston around 11:15 a.m. EDT Sunday to begin their final pre-launch activities. The three-day launch countdown will be started at 6 p.m. EDT Sunday.

0506 GMT (1:06 a.m. EDT)

Technicians at launch pad 39B have disconnected explosive ordnance as part of early rollback preparations. At a midnight senior management meeting, however, officials decided not to continue with the list of chores to unhook Discovery from its seaside complex given a more optimistic weather outlook that keeps Dennis well away from Kennedy Space Center. Proceeding with more rollback activities overnight would have prevented an on-time launch Wednesday.

NASA officials will meet again at 6:30 a.m. EDT to review the hurricane's progress and the latest forecast track.

THURSDAY, JULY 7, 2005

With Hurricane Dennis churning in the Caribbean, NASA managers this evening decided to begin preparing the shuttle Discovery for a possible roll back to the protection of the Vehicle Assembly Building should the storm take a turn to the east and threaten the Space Coast. Read our full story.

2310 GMT (7:10 p.m. EDT)

Initial rollback preparations are beginning, thereby keeping NASA's options open for possibly moving Discovery off the launch pad Friday night because of Hurricane Dennis. A decision whether to continue with the work will be debated during overnight and early morning management meetings.

Should a rollback be ordered, the crawler-transporter team will arrive on duty at 2 p.m. for the anticipated first motion off the pad at 8 p.m. EDT. Discovery should be back inside the safe confines of the Vehicle Assembly Building around 5 a.m. EDT Saturday.

Moving Discovery would delay next week's liftoff. When launch could be rescheduled depends on the shuttle's return to the pad. NASA officials estimate it will take 9 days from the point of pad arrival until launch -- 5 to 6 days spent with preparations and then the standard three-day launch countdown.

The available daylight launch window for the return to flight shuttle mission extends to July 31. If Discovery isn't off the ground by then, the ship must wait until September 9.

Shuttles have been returned to the VAB 15 times in program history, most recently in May when Discovery retreated from the pad to replace its external tank and solid rocket boosters.

This would be the fifth tropical weather-related rollback -- following Columbia's mission STS-35 rollback for Tropical Storm Klaus in October 1990, Endeavour's STS-69 rollback for Hurricane Erin in August 1995, and two rollbacks for Atlantis' STS-79 mission for Hurricanes Bertha and Fran in July and September 1996.

It would make Discovery's STS-114 flight only the third to experience two rollbacks. STS-35 was moved back once for liquid hydrogen leaks in Columbia and then Tropical Storm Klaus. And STS-79 had the two hurricane scares.

2155 GMT (5:55 p.m. EDT)

While technicians prep space shuttle Discovery for the countdown to next week's launch, mission managers and weather forecasters are carefully monitoring the path of powerful Hurricane Dennis and whether the ship should be rolled back to its assembly building for shelter.

"The current forecast shows only a slight chance of more than 40 knot (46 mph) winds effecting KSC on Saturday. A decision will be made this evening if preparations should begin for a possible rollback of space shuttle Discovery," NASA said late today. "A decision on rollback would not be made until tomorrow. At this point, none of the preparations will impact the July 13 launch date."

Rules call for the shuttle to be moved off its launch pad and returned to the 52-story Vehicle Assembly Building if there's a possibility that winds could exceed a sustained speed of 60 knots (69 mph).

If the rollback is ordered, Discovery would begin the 4.2-mile trip late Friday.

The official track of Dennis predicts the Space Coast would be spared a direct hit from the storm as the Category 3 hurricane moves through the Gulf Mexico toward the Alabama/Florida panhandle region for landfall late Sunday afternoon. However, NASA is worried about the storm wobbling more easterly and the outer fringes brushing the Cape this weekend.

Meanwhile, work in Firing Room 3 of the Complex 39 Launch Control Center has started in advance of picking up the countdown at 6 p.m. EDT (2200 GMT) Sunday.

At launch pad 39B today, equipment-filled lockers are being stowed into Discovery for use by the astronauts in space. The mid-deck seats will be installed on Monday.

Installation of the ordnance has been completed. Closeouts of the shuttle's aft engine compartment are supposed to be wrap up tomorrow. Also on Friday, the pad structure and surface will be washed down and the shuttle's new wing leading edge sensors that will monitor impacts or temperature changes will be programmed for flight.

FRIDAY, JULY 1, 2005

NASA managers wrapped up a two-day flight readiness review Thursday and formally cleared the shuttle Discovery for blastoff July 13 on the first post-Columbia shuttle mission. If all goes well, the countdown will begin at 6 p.m. July 10 for a launch attempt at 3:50:47 p.m. on July 13, weather permitting. Read our full story.

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THURSDAY, JUNE 30, 2005
2118 GMT (5:18 p.m. EDT)

NASA has issued the following statement:

NASA has cleared the Space Shuttle to Return to Flight. After a two-day Flight Readiness Review meeting at NASA's Kennedy Space Center in Florida, senior managers approved a July 13 launch date for Discovery.

Commander Eileen Collins and her crew are scheduled to lift off at 3:51 p.m. EDT on the first U.S. space flight since the February 2003 loss of the Shuttle Columbia.

"After a vigorous, healthy discussion our team has come to a decision: we're ready to go," NASA Administrator Michael Griffin said after the meeting. "The past two and half years have resulted in significant improvements that have greatly reduced the risk of flying the Shuttle. But we should never lose sight of the fact that space flight is risky.

"The Discovery mission, designated STS-114, is a test flight," Griffin said, noting that astronauts will try out a host of new Space Shuttle safety enhancements. In addition, Discovery will carry 15 tons of supplies and replacement hardware to the International Space Station. July 13 is the beginning of three weeks of possible launch days that run through July 31.

NASA's Associate Administrator for Space Operations, William Readdy, chaired the Flight Readiness Review, the meeting that traditionally sets launch dates and assesses the Shuttle's fitness to fly.

"Today's decision is an important milestone in returning the Shuttle to service for the country. Our technical and engineering teams are continuing their in-depth preparations to ensure that Eileen and her crew have a successful mission," he said.

1933 GMT (3:33 p.m. EDT)

DATE SET. NASA's top officials have wrapped up their exhaustive review of space shuttle Discovery's readiness to fly the first post-Columbia mission. The two-day meeting ended this afternoon with the decision to launch Discovery on July 13 at 3:51 p.m. EDT (1951 GMT). A news conference is underway at Kennedy Space Center to make the announcement. Check back later for a full story.

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

We're now looking at a 3:30 p.m. EDT briefing start time.

1810 GMT (2:10 p.m. EDT)

NASA is now targeting 3 p.m. EDT for the start of today's post-FRR news conference.

1500 GMT (11 a.m. EDT)

The Flight Readiness Review is expected to wrap up a bit earlier than expected. NASA has moved the news conference to announce shuttle Discovery's official launch date from 4 p.m. to 2:30 p.m. EDT. We'll post the date on this page immediately.

TUESDAY, JUNE 28, 2005

Twenty-nine months after the Columbia accident, NASA's top managers will gather at Kennedy Space Center on Wednesday and Thursday to debate the readiness of putting another space shuttle in the air.

Known as the Flight Readiness Review, this traditional meeting before every launch allows a detailed examination for each piece of the shuttle. The two-day affair will decide if Discovery can launch in mid-July as currently scheduled. The FRR concludes with the space agency setting the official launch date.

"It will be an interesting session and out of that we'll emerge with the knowledge that we're either ready to go, barring the unforeseen, or that some late-breaking bit of information has been brought up," NASA Administrator Mike Griffin told agency employees in a live television address today.


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The requirement to launch Discovery in daylight coupled with orbital constraints for docking to the International Space Station limit liftoff opportunities to July 13 through July 31. The next window opens September 9. Heading into the FRR, NASA officials say the shuttle is ready to fly.

"Discovery out at the launch pad is in outstanding condition. All of the vehicle tests we've done to date have proven out very well. So right now -- about two weeks out from launch -- we're looking very, very good," shuttle launch director Mike Leinbach said today.

Since returning to the launch pad earlier this month, Discovery has been fitted with its payload and the ship's hypergolic propellant tanks are being filled with monomethyl hydrazine and nitrogen tetroxide. The fuels feed Discovery's orbital maneuvering engines and jet thrusters during the mission.

"That all went very well," Leinbach said.

But one potential problem on everyone's mind is Florida's near-daily afternoon thunderstorms in the summertime. The launch time on July 13, dictated by the station's orbit for rendezvous, is 3:51 p.m. EDT.

"If I had to point to one thing that worries me the most, I would point to what you are seeing behind me -- the clouds that are building up," Leinbach said this afternoon. "It is going to be a challenge to launch a little bit before 4 o'clock in the middle of July. We'll deal with that real-time when it happens on July 13."

Back in Washington, Griffin met with the Stafford-Covey Return to Flight Task Group earlier today. The panel has concluded that the shuttle is safe enough to resume flights despite NASA not fulfilling the literal interruption for three recommendations issued by the Columbia Accident Investigation Board.

"The Stafford-Covey Group is going to point out that although we've done an admirable job in setting ourselves about the task of responding to the Columbia Accident Investigation Board's recommendations, that we will not be in full compliance with those should we choose to launch," Griffin said. "And they pointed out that in part the reason we could not be in complete compliance had to do with the wording of those recommendations -- that they were not implementable as strictly speaking, as worded.

"One simple example: we are tasked with eliminating all debris shedding from the external tank and associated parts of the shuttle system. We've not been able to do that. No one knows how to do that. So we either believe that we have reduced the debris to an acceptable level of risk consistent with other risks that we assume when we fly the shuttle, or we don't. But I do believe we have, and we must go forward on that basis because we cannot eliminate all debris in the literal sense of the wording. And there were other examples."

NASA plans a news conference Thursday afternoon following the FRR to announce the formal launch date. To see a chart of the daily launch times in July, click here.

MONDAY, JUNE 27, 2005

An independent panel charged with assessing NASA's implementation of post-Columbia safety upgrades said in its final hearing today that the agency has failed to fully implement three of the most critical safety upgrades recommended by the Columbia Accident Investigation Board. Read our full story.

Additional coverage for subscribers:
VIDEO: MONDAY'S TASK GROUP NEWS BRIEFING DIAL-UP | BROADBAND
AUDIO: LISTEN TO THE BRIEFING FOR IPOD
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FRIDAY, JUNE 24, 2005

Shuttle launch debris risk uncertain but 'acceptable'
NASA managers met Friday and decided to press ahead with plans to launch the shuttle Discovery next month even though engineers have been unable to precisely define the threat posed by ice shaking off the ship's external tank during launch. Read our full story.

Additional coverage for subscribers:
VIDEO: "DEBRIS 101" EXPLAINS WHAT THREATENS THE SHUTTLE QT
VIDEO: REVIEW OF NASA'S EXTENSIVE IMPACT TESTING PERFORMED QT
VIDEO: PRESENTATION ON THE CHANGES MADE TO THE TANK QT
VIDEO: DAY-BY-DAY PREVIEW OF DISCOVERY'S MISSION QT
VIDEO: DETAILED SUMMARY OF MISSION'S THREE SPACEWALKS QT
VIDEO: STS-114 ACTIVITIES PLANNED ABOARD AND OUTSIDE ISS QT
VIDEO: CHANGES TO LAUNCH AND LANDING OPERATIONS QT
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WEDNESDAY, JUNE 15, 2005

The space shuttle Discovery, bolted to an upgraded external tank and a fresh set of boosters, was hauled back out to pad 39B early today for work to ready the ship for blastoff July 13. Read our full story.

1643 GMT (12:43 p.m. EDT)

The transporter has lowered the mobile launch platform to the pad's four pedestals. The crawler will be disengaged and driven away, leaving Discovery on the pad following today's successful rollout.

1558 GMT (11:58 a.m. EDT)

Discovery is atop launch pad 39B to begin the final month of preparations leading to liftoff in mid-July. Technicians still must lower the platform onto the pad pedestals over the next hour or so and then begin the extensive connections of fuel, electrical and communication lines between the ground and shuttle.

Plans call for Discovery's payload bay doors to be opened tomorrow and the cargo to be installed into the orbiter on Friday. The cargo pieces include the Italian-made Raffaello supply module filled with equipment and materials for the International Space Station, a new external stowage platform that will be mounted to the station and a fresh control-stabilizing gyroscope to replace one that failed a couple of years ago.

1545 GMT (11:45 a.m. EDT)

The platform is being aligned with the pedestals now.

1530 GMT (11:30 a.m. EDT)

Just a few feet remain to place the platform atop the pad pedestals.

1458 GMT (10:58 a.m. EDT)

Discovery is creeping onto the level pad surface as the rollout passes the nine-hour mark.

A precision laser guidance system will help align the mobile launch platform over the pad pedestals. The crawler-transporter then lowers the platform onto the pedestals to complete the rollout.

1448 GMT (10:48 a.m. EDT)

The transporter continues its extremely slow roll up the pad ramp. There are no technical problems being reported.

1425 GMT (10:25 a.m. EDT)

We have posted some additional video clips that capture this morning's big move for space shuttle Discovery. The movies are available for Spaceflight Now Plus users.

Additional coverage for subscribers:
VIDEO: DAY BREAKS OVER KENNEDY SPACE CENTER QT
VIDEO: HOT TRANSPORTER BEARING CAUSES PROBLEMS QT
VIDEO: DISCOVERY NEARS PAD 39B AFTER THE LONG JOURNEY QT
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1420 GMT (10:20 a.m. EDT)

It should take 30 to 45 minutes for the transporter to climb the five percent incline ramp to the pad surface. The crawler's jacking and leveling system will be critical during this time. The vehicle uses hydraulic lifts to keep the shuttle level during the ramp ascent by jacking up the front-end of the mobile launch platform.

1409 GMT (10:09 a.m. EDT)

Discovery has reached the perimeter fence to enter into launch complex 39B.

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

The current speed is 0.9 mph. The latest estimation predicts Discovery should reach the launch pad ramp in a half-hour or so. It will take 30-45 minutes to travel up the incline, and the shuttle should be over the pad pedestals by around 11:30 a.m.

1258 GMT (8:58 a.m. EDT)

Now seven hours into today's rollout of Discovery. The shuttle has resumed moving after another greasing of a bearing in the transporter. Technicians have been forced to do that a few times during the rollout.

1231 GMT (8:31 a.m. EDT)

The transporter has stopped again. Technicians are repacking the troublesome bearing that has been running hotter than desired during today's rollout. NASA says this quick "pit stop" to lubricate the bearing should take about 10 minutes.

Based on the progress made so far, the shuttle is expected to begin rolling up the pad's inclined ramp a little after 10 a.m. EDT.

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

The bearing temperature has stabilized and the crawler's speed is now 0.95 miles per hour, which is almost top speed for the transporter.

NASA expects the shuttle will be on the pad before 12 noon EDT. The protective gantry-like rotating service structure should be moved around the orbiter by 1 p.m. to shield Discovery from any adverse weather conditions this afternoon.

1135 GMT (7:35 a.m. EDT)

The transporter has made the northward turn where the crawlerway splits between pads 39A and 39B.

After moving at about 0.5 mph during the rollout while monitoring bearing overheating concerns, the crawler drivers have been able to pick up the pace to about 0.7 mph. But the transporter has not been allowed to reach its top speed of 1 mph.

1030 GMT (6:30 a.m. EDT)

It has been extra-slow going for Discovery. Overheating troubles with bearings on the Apollo-era crawler-transporter have caused reduced speeds and some stops along the way. Arrival at launch pad 39B is now expected no earlier than 12 noon EDT.

0855 GMT (4:55 a.m. EDT)

Discovery remains en route to launch pad 39B on the edge of the Atlantic Ocean. But this morning's rollout has been slowed a bit by problems with overheated bearings in the crawler-transporter. The shuttle is supposed to arrive at the pad around 10 a.m. EDT.

0620 GMT (2:20 a.m. EDT)

The space shuttle Discovery, bolted to an upgraded external tank and a fresh set of boosters, began its glacial return to pad 39B early today for work to ready the ship for blastoff July 13. Read our full story.

Additional coverage for subscribers:
VIDEO: FINAL PREPS ARE MADE FOR ROLLOUT QT
VIDEO: DISCOVERY BEGINS ITS JOURNEY TO THE PAD QT
VIDEO: THE SHUTTLE EMERGES FROM THE ASSEMBLY BUILDING QT
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0617 GMT (2:17 a.m. EDT)

Discovery is now outdoors as the rollout inches along. We'll provide further updates later this morning as the shuttle nears the pad.

0558 GMT (1:58 a.m. EDT)

ROLLOUT HAS BEGUN! First motion of space shuttle Discovery's rollout to launch pad 39B occurred at 1:58 a.m. EDT, beginning this 4.2-mile trek that should take eight hours to complete.

The first minutes of the rollout will proceed very slowly as the shuttle is moved out of the tight confines of the Vehicle Assembly Building. Once outside the building, the transporter is allowed to rev up to its maximum drive speed of one mile per hour.

0554 GMT (1:54 a.m. EDT)

The official "go" has been given to start rolling to the launch pad in the next few minutes.

0553 GMT (1:53 a.m. EDT)

A technician is adjusting the positioning of a flex hose on the left-hand solid rocket booster to ensure good clearance with one of the Vehicle Assembly Building's myriad of access planks. This extra work was ordered after an observer noted a possible obstruction.

0545 GMT (1:45 a.m. EDT)

The latest estimate has the rollout starting around 2 a.m., pending resolution of concerns with the platform obstruction.

0537 GMT (1:37 a.m. EDT)

One of the rollout observers noticed a possible obstruction of the shuttle platform by a VAB work plank. That is being checked out right now. There is no new estimate on when rollout will begin.

0527 GMT (1:27 a.m. EDT)

A 25-foot clear zone is being established around the shuttle transporter in preparation for the rollout. The jacking and leveling is almost complete.

0523 GMT (1:23 a.m. EDT)

Technicians report that the platform should reach the proper clearance height above the pedestals in about five minutes.

0516 GMT (1:16 a.m. EDT)

The platform is hovering a few inches above the pedestals, which are located in all four corners, as the jacking work continues.

0502 GMT (1:02 a.m. EDT)

The rollout start time is now expected around 1:30 a.m.

0501 GMT (1:01 a.m. EDT)

The crawler-transporter is being raised to essentially pick up the mobile launch platform -- upon which Discovery stands -- for the 4.2-mile ferry to the pad. The platform has been resting on pedestals in the VAB during assembly of the shuttle pieces.

0447 GMT (12:47 a.m. EDT)

Shuttle weather officer Kathy Winters reports that conditions will be acceptable throughout the next eight hours during Discovery's slow roll from the assembly building to the pad.

0446 GMT (12:46 a.m. EDT)

Shuttle launch director Mike Leinbach has given the "go" to start the jacking and leveling operations. This lifts Discovery's mobile launch platform from the VAB pedestals for the transportation to pad 39B today.

0439 GMT (12:39 a.m. EDT)

Pre-rollout sweeps of the mobile launch platform by safety personnel have completed. The platform's compartments are now manned. Communications checks between the various observers stationed to monitor the shuttle's exit through the VAB doorway will begin in about five minutes. And then the jacking and leveling operations of Discovery's platform and transporter starts, which should take 20-25 minutes to complete. Rollout is now estimated to begin around 1:15 a.m. EDT at the earliest.

0433 GMT (12:33 a.m. EDT)

The platform has successfully switched from the Vehicle Assembly Building power to its internal supplies. One final access plank remains to be retracted. So rollout should be getting underway shortly.

0417 GMT (12:17 a.m. EDT)

The power handover from facility supplies to the platform itself is continuing. Technicians are experiencing difficulty with this process, prompting some troubleshooting, NASA says.

Rollout is now expected to start around 12:45 a.m.

"No showstoppers at this time," Kennedy Space Center spokesman George Diller says. "We're just a little bit behind because of some minor problems."

0415 GMT (12:15 a.m. EDT)

Work that is underway right now in the Vehicle Assembly Building is final retractions of access platforms around the shuttle vehicle.

0410 GMT (12:10 a.m. EDT)

The weather forecast calls for light and variable winds for the overnight rollout. There's only a 10 percent chance of rain during the 8-hour rollout time frame.

0405 GMT (12:05 a.m. EDT)

Despite the slight delay in beginning Discovery's trek to the launch pad, which is now anticipated to start around 12:30 a.m. EDT, NASA spokesman George Diller says activities have been going pretty well this evening.

0401 GMT (12:01 a.m. EDT)

The start of tonight's rollout is being pushed back a half-hour due to delays in transferring the mobile platform from ground-fed power to internal supplies.

0200 GMT (10:00 p.m. EDT Tues.)

The giant doors of the Vehicle Assembly Building's High Bay 3 have been opened tonight, providing a glimpse at the backside of space shuttle Discovery's tank and boosters. Rollout is scheduled to get underway in a couple of hours.

TUESDAY, JUNE 14, 2005

Nearly three weeks after vacating its launch pad and returning to the Vehicle Assembly Building, space shuttle Discovery will go back to pad 39B tonight as NASA begins the final month of work leading to the program's return to flight.

Discovery was demated from its original fuel tank and boosters while in the VAB and mounted with another tank that features additional heaters and instrumentation.

The shuttle interface test to verify good connections between Discovery, tank, twin solid rockets and the mobile launch pad platform has been completed. Workers will report for rollout duty at 8 p.m. EDT (0000 GMT) tonight. First motion for the 4.2-mile trip to the pad is targeted for midnight EDT (0400 GMT).

Watch this page for live updates on the roll.

MONDAY, JUNE 13, 2005
1550 GMT (11:50 a.m. EDT)

Discovery's rollout has been delayed one day after activities fell behind schedule. The move is now targeted to begin at 12:01 a.m. EDT (0401 GMT) Wednesday.

SUNDAY, JUNE 12, 2005

Final preparations have begun for transporting Discovery back to launch pad 39B. Work inside the Vehicle Assembly Building is leading to rollout starting as early as 1 a.m. EDT (0500 GMT) Tuesday.

Meanwhile, Discovery's payload heads to the pad inside a protective canister around midnight EDT tonight, arriving at the launch complex between 2 and 4 a.m. EDT (0600-0800 GMT) Monday. The cargo pieces include the Italian-made Raffaello supply module filled with equipment and materials for the International Space Station, a new external stowage platform that will be mounted to the station and a fresh control-stabilizing gyroscope to replace one that failed a couple of years ago.

The cargo will be loaded into Discovery's payload bay once the shuttle reaches the pad.

THURSDAY, JUNE 9, 2005

Space shuttle Discovery has been attached to its new external fuel tank, known as ET-121, and a pair of solid-fuel booster rockets atop a mobile launch platform in the Vehicle Assembly Building. This tank, boosters and platform were originally earmarked for use by Atlantis later this year, but NASA opted to switch Discovery since the tank has new fuel line heaters, additional sensors and instrumentation.

Whether Atlantis will fly with Discovery's first tank, known as ET-120, remains undecided.

Rollout to launch pad 39B is now targeted to begin at 3 a.m. EDT (0700 GMT) on Tuesday. The 4.2-mile move will take 8 to 10 hours.

From today's shuttle program status statement, here is a look at the ET-121 upgrades:

After several weeks of data evaluation from two previous tanking tests, program managers decided not to do another one prior to Discovery's launch. They reviewed data from two previous tests on ET-120, Discovery's original tank.

One major change to Discovery's new ET is the addition of a heater on the feedline bellows to prevent ice forming during fueling and launch. The bellows is a joint on the outside of the tank, not insulated with foam, to allow expansion, contraction and movement during fueling of super-cold liquid oxygen before launch. The line feeds oxygen to the Shuttle main engines at start-up and throughout the 8.5 minute climb to orbit.

Another change to the ET is in the hydrogen diffuser. A diffuser is a fabricated tube, which consists of a core and screen assembly. It diverts the flow into radial jets that are dispersed by the wire screen. There are two diffusers per ET at the top of the hydrogen and oxygen tanks.

Discovery's new ET uses a certified plain, two wire weave. ET-120 had a tighter woven mesh than was expected. The data review showed the out-of-specification diffuser may have been the contributing cause of a liquid hydrogen pressurization problem. A vent valve cycled 13 times during the tanking tests, versus the standard eight to nine times. The valve opens and closes to ensure the liquid hydrogen stays at the correct pressure in the final two minutes prior to launch.

Discovery's new ET originally was planned to fly with Atlantis on the second Return to Flight mission, STS-121. A decision will be made next week as to which external tank, ET-120 or 119, will be used for STS-121.

MONDAY, JUNE 6, 2005

NASA managers today ruled out a third tanking test for the shuttle Discovery, keeping launch of the first post-Columbia mission on target for July 13. The launch window extends to July 31 and as of this writing, engineers have five days of contingency time in the launch processing schedule to handle unexpected problems between now and the opening of the window. Read our full story.

FRIDAY, JUNE 3, 2005

After rolling back to the Vehicle Assembly Building from launch pad 39B, technicians demated space shuttle Discovery and its original external fuel tank. Discovery will be attached with another tank and set of solid rocket boosters for the return-to-flight mission. The new tank has additional ice-fighting heaters and instrumentation. See a photo gallery.

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VIDEO: TECHNICIANS PREPARE DISCOVERY FOR DEMATING QT
VIDEO: SHUTTLE DISCOVERY IS REMOVED FROM TANK QT
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MONDAY, MAY 30, 2005

Five men and two woman will launch aboard space shuttle Discovery for the first post-Columbia mission this summer, putting their lives on the line. The crew includes the first woman to command a shuttle mission, an Australian-born astronaut who lived on Mir and a Japanese space rookie. Get to know these astronauts through a series of one-on-one interviews.

THURSDAY, MAY 26, 2005

This is NASA's press statement on today's rollback:

The Space Shuttle Discovery is back in the Vehicle Assembly Building (VAB) at NASA's Kennedy Space Center, Fla. The Shuttle will get a new, modified external fuel tank to ensure a safe Return to Flight mission (STS-114).

Discovery, carried by a Crawler Transporter, entered the VAB at 4:30 p.m. EDT. The 10-hour, 4.2 mile trip from Launch Pad 39B was briefly interrupted due to an over heated bearing on the Transporter. Today's rollback was the 15th in Space Shuttle Program history.

"Rolling back Discovery was the right thing to do and demonstrates our commitment to a safe Return to Flight," said Shuttle Program Manager Bill Parsons. "We will continue to focus on the processing milestones and complete the additional analysis we determined was required, so that we continue to move toward a launch during the July window."

Technicians will de-mate Discovery from its External Tank (ET-120) and Solid Rocket Boosters on May 31. Discovery will be attached to ET-121 on June 7. ET-121 was originally scheduled to fly with the Shuttle Atlantis on the second Return to Flight mission (STS-121).

In the VAB, a new heater will be added to ET-121 on the feedline bellows. It is the part of the pipeline that carries liquid oxygen to the Shuttle's main engines, to minimize potential ice and frost buildup. The tank also has several safety improvements, including an improved bipod fitting that connects it to the Orbiter.

In addition, NASA's second redesigned tank has been outfitted with temperature sensors and accelerometers, used to measure vibration. These sensors will gather information about the tank's performance during flight.

After the heater is added to ET-121 and the Shuttle is attached to its new propulsion elements, Discovery will roll back out to Launch Pad 39B in mid-June. Discovery's payload, the Italian-built Multi-Purpose Logistics Module Raffaello, will be installed in the payload bay, while the Shuttle is on the pad.

Launch of Discovery for STS-114 is targeted for July 13. The launch window extends to July 31. During its 12-day mission, Discovery's seven-person crew will test new hardware and techniques to improve Shuttle safety and deliver supplies to the International Space Station.

Additional coverage for subscribers:
VIDEO: CRAWLER-TRANSPORTER IS POSITIONED UNDER DISCOVERY QT
VIDEO: WORKERS UNPLUG PAD UMBILICALS ROUTED TO SHUTTLE QT
VIDEO: DISCOVERY IS ROLLED OFF PAD 39B JUST AFTER SUNRISE QT
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2031 GMT (4:31 p.m. EDT)

Discovery is pulling into the Vehicle Assembly Building to complete its rollback from the launch pad.

1903 GMT (3:03 p.m. EDT)

The crawler has begun moving again, a couple of hours after being stopped because of an overheated bearing. Discovery should be back inside the assembly building by late afternoon.

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

The shuttle continues to be parked along the Kennedy Space Center crawlerway while technicians examine an overheated bearing within the transporter. NASA has two giant tracked crawler-transporters that were originally built for Apollo four decades ago.

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

Discovery's rollback has been stalled by a problem with the crawler-transporter. Engineers are working to fix the technical glitch, which has stopped the transporter as it neared the VAB this afternoon.

1048 GMT (6:48 a.m. EDT)

Seven weeks after rolling to the launch pad for the first space shuttle mission in two years, Discovery is retreating from the oceanfront complex this morning. The ship is headed to the Vehicle Assembly Building to exchange external fuel tanks and solid rocket boosters

The rollback started moments ago as the Apollo-era crawler-transporter began moving the mobile launch platform with Discovery on top. The 4.2-mile trip from pad 39B to the Vehicle Assembly Building is expected to take about 8 hours.

It is the 15th time in program history that a shuttle mission has been rolled off the launch pad.

Once in the 52-story building, Discovery will be detached from its current orange fuel tank and booster set. The lifting crane will lower the shuttle to the concrete aisle in the VAB.

Later, the shuttle will be maneuvered into another processing bay where a second tank and booster stack await. That tank was supposed to be used by Atlantis on the second post-Columbia launch. But NASA opted to have Discovery use it since the tank is being fitted with extra ice-defeating heaters installed around the liquid oxygen feedline bellows that the original tank lacked. Discovery's first tank also experienced problems with its fuel depletion sensors and a hydrogen pressure relief valve during a test in April.

Discovery is scheduled to be mated with the new tank around June 7, with rollout to pad 39B slated for June 14 in advance of a mid-July liftoff.

0907 GMT (5:07 a.m. EDT)

Kennedy Space Center spokewoman Jessica Rye says extra time needed to complete paperwork has delayed this morning's move of Discovery. The rollback is now targeted to start around 6 a.m. EDT.

0730 GMT (3:30 a.m. EDT)

The rollback has not yet started.

0500 GMT (1:00 a.m. EDT)

After waiting just outside the pad 39B fence, the crawler-transporter has driven up the incline and is now inching beneath space shuttle Discovery's mobile launch platform. The crawler will carry the platform and shuttle back to the Vehicle Assembly Building this morning. The 8-hour rollback is expected to begin sometime after 2 a.m. EDT.

Meanwhile, technicians successfully completed the Auxiliary Power Unit confidence test-run on Wednesday. This procedure saw Discovery's APUs started up to ensure they are working properly. The APUs are used only during launch and landing to provide hydraulic pressure for moving the wing flips, the main engine nozzles and deploying the landing gear.

TUESDAY, MAY 24, 2005
1615 GMT (12:15 p.m. EDT)

Borescope inspections on space shuttle Discovery to check for landing gear door mechanism cracks have been completed at launch pad 39B, and a NASA spokeswoman says the ship appears to be in good shape.

"The borescopes wrapped up last night. All of the preliminary looks say that Discovery is fine and they did not see any of indications of any crack or cracks in that area," said Kennedy Space Center spokewoman Jessica Rye.

With access to the landing gear wells from beneath the payload bay, technicians used the camera-tipped borescope to look for any cracks in the retract link assembly on the left-hand main landing gear door. It was decided that the inspections were not needed for the right-hand door because photos taken in the hangar before Discovery moved to the launch were available.

"The right-hand side we had very good closeout photos of that particular area, and so they felt very comfortable with those closeout photos," Rye said.

The inspections were prompted after a crack was found on Atlantis' right-hand main landing gear.

Checks of Endeavour, which is undergoing a major overhaul at the spaceport, revealed no cracks.

Discovery remains scheduled for rollback to the Vehicle Assembly Building on Thursday.

MONDAY, MAY 23, 2005
1700 GMT (1:00 p.m. EDT)

Rollback of Discovery is now expected to occur Thursday morning, NASA said today, following the landing gear inspections. The 8-hour, 4.2-mile trip from pad 39B to the Vehicle Assembly Building is targeted to begin at 2 a.m. EDT (0600 GMT).

Once in the 52-story VAB, Discovery will be detached from its external fuel tank and solid rocket boosters. A heavy-duty crane will maneuver the shuttle into other processing bay for mating to the tank and booster set originally scheduled for use on the second post-Columbia mission. That second tank has additional ice-fighting heaters installed. Discovery is expected to return to pad 39B in mid-June for liftoff in mid-to-late July.

But before Discovery leaves the pad, borescope inspections are being performed to determine if a crack found on shuttle Atlantis' retract link assembly on the right-hand main landing gear is a fleet-wide issue.

"Engineers have looked at the closeout photos of the link assembly on Discovery. The initial review indicates the link assembly does not appear to have any cracks," NASA said in a status report today. "To ensure there are no cracks in the assemblies, technicians will enter Discovery's payload bay and perform borescope inspections of the area, an inspection that can only be accomplished at the pad. This additional work does not impact the launch planning window of July 13-31."

Atlantis' link assembly was removed and will be replaced with a spare, the space agency said.

0420 GMT (12:20 a.m. EDT)

Technicians will use a tiny camera to peek inside space shuttle Discovery's wheel wells today in search of landing gear cracks like those found on sistership Atlantis.

The borescope inspections to double-check Discovery were ordered over the weekend in light of the Atlantis problem. The work is being done with Discovery standing vertically at launch pad 39B.

A test-run of Discovery's auxiliary power units, which provide the hydraulic pressure needed to drive the shuttle's wing flaps, drop the landing gear and swivel the main engine nozzles, had been scheduled for today. However, the APU test will be delayed until Wednesday due to the borescope activities.

Also postponed is Discovery's departure from the pad. Workers were supposed to move the shuttle back to the Vehicle Assembly Building on Tuesday to begin the process of switching Discovery to another fuel tank and set of solid rocket boosters. Rollback is now anticipated to occur Friday.

Atlantis is undergoing pre-flight assembly and testing within a Kennedy Space Center hangar for its September launch on the second post-Columbia mission. Specific details about the tiny cracks and what, if any, impact the issue could have on Discovery's July launch were not clear Sunday night.

FRIDAY, MAY 20, 2005

Engineers pumped a half-million gallons of supercold rocket fuel into the shuttle Discovery's external tank today, repeating a test that uncovered two unexpected problems in April. This time around, suspect fuel depletion sensors in the tank worked normally while a hydrogen pressure relief valve continued to cycle more often than normal. Read our full story.

Read our earlier Mission Status Center coverage.