BY SPACEFLIGHT NOW

Follow the STS-105 flight of space shuttle Discovery and the handover between the Expedition Two and Expedition Three crews of the international space station. Reload this page for the very latest.

SUNDAY, AUGUST 12, 2001

Space shuttle Discovery crossed the finish line of its two-day race to the international space station on Sunday, docking to the orbiting outpost about 250 miles above northwestern Australia. The main objective of Discovery's visit is the exchange of resident crews living aboard the outpost. Read our full docking story.

Spaceflight Now Plus subscribers can watch today's docking, as well as a couple of feature movies, in either QuickTime or RealVideo:

For subscribers only:

   VIDEO: DISCOVERY APPROACHES STATION QT or RV
   VIDEO: SHUTTLE DOCKS TO ALPHA QT or RV
   VIDEO: MISSION SUMMARY QT or RV (Running time 5 mins)
   VIDEO: STS-105 CREW FEATURE QT or RV (Running time 4 mins)
   VIDEO: SUNDAY'S MISSION STATUS BRIEFING QT or RV

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

HATCH OPENING. The astronauts of space shuttle Discovery and the international space station have been united with the opening of hatches between the two spacecraft. Greetings are underway inside the U.S. Destiny science lab of the station.

In a pre-flight interview commander Scott Horowitz explained what is planned at this point in the mission:

"Right after we have the initial greeting with the crew, the first thing I do is a safety brief. We have to be briefed on any particular safety aspects of how they're doing operations on the international space station. Almost like you would if you were flying on an airliner or riding on a large ship, where you know where the emergency exit is that takes us back to the space shuttle, where the emergency equipment is -- masks and fire extinguishers and all those kinds of things.

"After that is done, we are going to get right to work trying to move some of the equipment off the middeck of the space shuttle, which is going to be amazingly compact. I mean, we're going to have all this stuff piled in the middeck to help support transferring the Expedition Three crew. So, some of their most critical items will be transferred very shortly after we dock. The Expedition Three crew will start their handover briefings with Expedition Two, and then we'll start going about getting ready to do all of our joint work together."

2030 GMT (4:30 p.m. EDT)

The joint crews are now preparing to open the hatchway connecting Discovery and Alpha. Hatch opening is running a bit behind schedule today.

1950 GMT (3:50 p.m. EDT)

The astronauts are performing the leak checks following today's docking. Hatch opening is expected shortly.

1904 GMT (3:04 p.m. EDT)

The docking ring has been retracted and hooks have driven closed. The shuttle's docking mechanism will now be powered down.

Plans call for the hatches between the two spacecraft to be opened at around 4 p.m. EDT, followed by a welcoming ceremony and the start of transfer work to move cargo from the shuttle to station.

1858 GMT (2:58 p.m. EDT)

The extension ring on the shuttle's docking system is being retracted after the astronauts fixed a mis-alignment problem, bringing the international space station's docking port to a firm seal with Discovery. The seven astronauts aboard Discovery and the three-person space station Expedition Two crew are now orbiting together in a single, joined spacecraft.

1843 GMT (2:43 p.m. EDT)

The docking occurred at 2:41 p.m. some 250 miles above northwest Australia. Currently, the rates between the shuttle and station are being damped out. Later the hooks and latches will be closed to firmly join the two spacecraft and Discovery's Orbiter Docking System docking ring will be retracted.

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

CONTACT AND CAPTURE! Space shuttle Discovery has docked to the international space station to deliver the Expedition Three crew to the outpost for their four-month stay. Discovery will shuttle the Expedition Two astronauts back to Earth after five months living and working aboard Alpha.

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

Distance is now 10 feet as Discovery slowly inches ever closer to the international space station under the manual control of commander Scott Horowitz.

The orientation-control gyros on the station are disabled for the linkup to keep the complex from moving, while Discovery' thrusters are programmed to fire in a calculated way to force the two docking ports together at the point of contact.

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

Now 16 feet to docking.

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

The alignment between docking ports on Discovery and the space station is acceptable and no "fly out" maneuver by the shuttle is necessary. The final approach along the last 30 feet is now in progress.

1832 GMT (2:32 p.m. EDT)

Looks like docking will be a few minutes later the targeted time of 2:38 p.m. EDT. The linkup doesn't have a particular window in time that is must occur, such as when the craft pass over a ground station, so this slight delay isn't a problem.

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

Distance now 91 feet.

1824 GMT (2:24 p.m. EDT)

Discovery is now inside the 150 feet to docking with the international space station.

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

Distance is now 200 feet.

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

Discovery and the space station are now about 300 feet apart, closing at about two-tenths of a foot per second.

1807 GMT (2:07 p.m. EDT)

Discovery has now reached the velocity vector, or V-bar, directly in front of the station's direction of travel with a distance of about 400 feet. The shuttle can hold at this point for a stationkeeping maneuver to ensure proper alignment between the two craft before the approach to docking begins.

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

Discovery is making its arc from a point below to the point in front of the space station.

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

Discovery has now reached that milestone point 600 feet below the space station.

Commander Scott Horowitz is taking over manual control for the remainder of today's rendezvous and docking of Discovery to the international space station.

Piloting the shuttle from the aft control station on the flight deck of Discovery, he will regularly pulse the shuttle's steering jets to keep the shuttle on the correct course.

Flight Director John Shannon explains what will happen over the next hour or so as Discovery heads to docking:

"The rendezvous and docking are going to be just like we've seen on all the flights since STS-102 last March. The crew is going to be approaching the space station from behind and below. They'll come up below the station with the payload bay facing up toward the station, you'll be able to see it real well at about 600 feet on what we call the r-bar. That's the imaginary line from the space station down to the center of the Earth.

"Scott Horowitz will then put in what we call a plus-X burn, or pulse, while the automatic computers are pitching the vehicle up and it will just describe an arc from below the space station to directly in front of it. And they'll come out about between 400 to 350 feet in front of the space station with the payload bay facing it."

"They'll stop there, make sure everything looks OK, they'll get a 'go' from the ground to proceed. And then Scott Horowitz will fly an eight-degree corridor all the way in, slowly translating with the payload bay directly toward the space station. When he gets about 30 feet away, he'll be flying a five-degree cone into the space station.

"He'll stop at 30 feet, make sure everything is lined up perfectly, and then he'll press on in very slowly. In that final phase, he has about a three-inch lateral margin and you'll see him slowly tweak that out as we come in and dock.

"When we dock, there is an automatic sequence the crew initiates through a push button that fires jets that gives us just enough push to make sure the docking system is captured and then we start driving hooks to pull the two vehicles together."

1747 GMT (1:47 p.m. EDT)

Distance now 1,000 feet.

1744 GMT (1:44 p.m. EDT)

The U.S. solar arrays on the space station -- stretching 240 feet tip-to-tip -- have been feathered to an "edge-on" position relative to Discovery's final approach to the front side of the station in the next hour. This is done so the thruster plumes from the shuttle don't harm the delicate arrays.

The Russian solar arrays on Zarya and Zvezda will be repositioned shortly.

1741 GMT (1:41 p.m. EDT)

Discovery has completed another mid-course correction thruster firing.

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

Now 2,500 feet separating the two spacecraft.

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

Discovery has performed the next in its series of mid-course correction maneuvers. The shuttle is now less than one mile from the station. Time to docking is just over an hour. Mission Control is expecting the docking to occur at approximately 2:40 p.m. EDT.

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

Discovery has performed a quick pulse of its steering jets -- one of four small maneuvers to tweak the shuttle's course to the international space station. Distance between the two spacecraft is about two-and-a-half miles.

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

The first ship-to-ship communications between the astronauts aboard Discovery and station have been made. The shuttle is now inside five miles to Alpha.

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

Traveling about eight miles below and behind the international space station, shuttle commander Scott Horowitz has fired Discovery's left orbital maneuvering system engine for 15 seconds to begin the terminal phase of today's rendezvous for the planned 2:38 p.m. EDT docking.

The so-called Terminal Initiation burn puts Discovery on a direct course to intercept the station over the next 90-minute orbit of Earth, bringing the shuttle to a spot within 600 feet below the orbiting outpost at about 1:46 p.m. Horowitz will then guide Discovery to a point inside 400 feet directly in front of the station at 1:59 p.m. to begin the final approach to docking.

In a pre-flight interview, commander Horowitz explained this phase of the chase to catch the station:

"Rendezvous and docking the shuttle to the station we've done several times now, so there aren't a lot of unknowns. We're going to be doing what the last few crews have done. Our docking, like previous ones, we're going to rendezvous from below the station.

"We will fly below the station and enter a point that's about 500 feet underneath the station, as viewed from the Earth. At that point, we'll start a maneuver which we call a TORVA - it's a twice orbital rate, pitch-up that we fly around the space station and we get on to what we call the V-bar. So, we're in the same velocity vector as the space station.

"Once we get up to that point, we will simply fly towards the station at a very slow, controlled rate, get everything lined up, and then when we get a "go" from Mission Control, we will fly in and dock to the space station on the V-bar, we call it, which is in the velocity vector of the space station.

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

All systems are "go" for today's docking of Discovery to the international space station. The shuttle is currently 16 miles away from the outpost, closing in for the link up at 2:38 p.m. EDT. We have posted a very detailed timeline of today's activities. You can also see just the docking timeline.

We will have live coverage of today's rendezvous starting with the Terminal Initiation burn at 12:16 p.m.

The crew of Discovery was awakened at 6:10 a.m. EDT to the sounds of "The White Eagle," a traditional Russian folk song played for Expedition Three Pilot Vladimir Dezhurov. Dezhurov and his crewmates, Expedition Three Commander Frank Culbertson and Flight Engineer Mikhail Tyurin are just hours from arriving at their new home aboard the space station.

SATURDAY, AUGUST 11, 2001
2300 GMT (7:00 p.m. EDT)

Space shuttle Discovery remains on course for Sunday's rendezvous and docking with the international space station. Flight director John Shannon briefed reporters on mission status a short time ago. Here are some of his thoughts:

"The shuttle crew and Expedition Three are spending their first full day in orbit after a beautiful day yesterday. I'm happy to report there are absolutely no problems with either the shuttle or the ISS for the docking tomorrow.

"Right now, the shuttle is 8,000 nautical miles behind and below the international space station and it's closing at about 790 nautical miles per orbit," he said. "The shuttle crew spent this morning preparing for the docking tomorrow. That consisted of a checkout of their tools, the hand-held radar, the laser system we use when we get in close to measure distances and rates, and also setting up their computer systems to monitor the docking tomorrow.

"They also activated the docking system and extended the ring that's used to attach to the international space station. They pulled out the shuttle's robotic arm and did a survey of the payload bay and that all looked really good."

Spaceflight Now Plus subscribers can watch the news conference in its entirety in either QuickTime or RealVideo:

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

The crew of space shuttle Discovery was awakened by mission control at 8:14 a.m. EDT this morning with the cowboy classic "Back in the Saddle Again" by Gene Autry, a special tribute to Expedition 3 commander Frank Culbertson, who returned to space yesterday after an almost eight-year long stint behind a desk as a NASA manager.

"It's great to be back up here and thanks for the music," Culbertson radioed from Discovery. "Now I've got to translate whoppee-kai-yay to the Russians... It's a beautiful day up here."

The crew's first full day in space will be spent checking out the systems they will need for tomorrow's planned docking with the space station.

FRIDAY, AUGUST 10, 2001

The shuttle Discovery rocketed away from NASA's Florida spaceport today and set off after the international space station, carrying a fresh three-man crew and nearly four tons of supplies and equipment, including yet another sorely needed command-and-control computer. Read our full story.

We have also updated our master flight plan that details the astronauts' activities on this 12-day flight.

Spaceflight Now Plus subscribers can enjoy the following video clips from today's launch:

Additional coverage for subscribers only:

   VIDEO: LAUNCH OF DISCOVERY QT or RV
   VIDEO: ONBOARD CAMERA RECORDS COCKPIT VIEW QT or RV
   VIDEO: LIFTOFF AS SEEN FROM VAB ROOF QT or RV
   VIDEO: DRAMATIC VIEW FROM IN FRONT OF PAD QT or RV
   VIDEO: CLOSE-UP VIEW OF MAIN ENGINES QT or RV
   VIDEO: PAD PARAMETER LAUNCH VIEW QT or RV
   VIDEO: BEACH TRACKER REPLAY QT or RV
   VIDEO: VIEW OF LAUNCH FROM PRESS SITE QT or RV
   VIDEO: SOLID ROCKET BOOSTER SEPARATION QT or RV
   VIDEO: ASTRONAUTS DEPART QUARTERS FOR LAUNCH QT or RV

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

T+plus 1 hour, 45 minutes. Discovery's two 60-foot long payload bay doors have been swung open and Mission Control has given the astronauts the "go" for on-orbit operations following the successful journey into space today. Next up will be deployment of the Ku-band radar and TV antenna shortly.

The astronauts -- awake since about 7 a.m. EDT -- are due to begin an 8-hour sleep period at 12:10 a.m. EDT.

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

T+plus 44 minutes. Discovery is now in an orbit of 145 by 97 statute miles.

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

T+plus 40 minutes. The twin Orbital Maneuvering System engines on the tail of Discovery have been fired successfully to propel the shuttle the rest of the way to orbit. The next major event will be opening Discovery's payload bay doors in about an hour.

2144 GMT (5:44 p.m. EDT)

T+plus 34 minutes. Now less than five minutes away from the OMS-2 burn to boost the shuttle from its highly elliptical sub-orbital trajectory achieved at main engine cutoff to a safe orbit.

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

T+plus 26 minutes. Today's official launch time was 5:10:14.075 p.m. EDT.

2131:14 GMT (5:31:14 p.m. EDT)

T+plus 21 minutes. The umbilical flapper doors on Discovery's belly have been closed. These doors are opened for the external tank umbilicals. They need to be closed and sealed for heat protection during the shuttle's reentry at the end of the mission. The post-launch chores for the shuttle astronauts are proceeding well with no significant problems being reported.

2127:14 GMT (5:27:14 p.m. EDT)

T+plus 17 minutes. Mission Control reports the Orbital Maneuvering System engine firing to boost the shuttle from its current sub-orbital trajectory to a safe orbit will occur at T+plus 38 minutes, 30 seconds.

2125:14 GMT (5:25:14 p.m. EDT)

T+plus 15 minutes. The shuttle is being maneuvered so the astronauts can take pictures of the discarded external tank. Also, the APUs are being shut down.

2120:44 GMT (5:20:44 p.m. EDT)

T+plus 10 minutes, 30 seconds. The three-person crew living aboard the international space station have been radioed the news from Mission Control of Discovery's safe and successful launch today. The Expedition Two crew will have visitors from the shuttle with docking planned on Sunday.

2118:48 GMT (5:18:48 p.m. EDT)

T+plus 8 minutes, 34 seconds. MECO! Confirmation that Discovery's main engines have cutoff as planned, completing the powered phase of the launch. Space shuttle Discovery has safely embarked on its two-day chase to rendezvous and dock with the international space station on Sunday.

2118:14 GMT (5:18:14 p.m. EDT)

T+plus 8 minutes. The main engines beginning to throttle back to ease the force of gravity on the shuttle and astronauts.

2117:14 GMT (5:17:14 p.m. EDT)

T+plus 7 minutes. Discovery can now reach a orbit on the power of one main engine should two fail. But all three continue to fire properly.

2116:34 GMT (5:16:34 p.m. EDT)

T+plus 6 minutes, 20 seconds. Discovery has performed the roll to heads-up maneuver, putting the shuttle atop the external tank. This allows for a clear communications path to the orbiting NASA TDRS tracking and data relay satellites.

2115:14 GMT (5:15:14 p.m. EDT)

T+plus 5 minutes. Discovery can now reach a orbit on the power of two main engines should one fail. But all three continue to fire properly. A spectacular late-afternoon launch!

2114:24 GMT (5:14:24 p.m. EDT)

T+plus 4 minutes, 10 seconds. Negative return. The shuttle is traveling too fast and is too far downrange so it can no longer return to the launch site in the event of a main engine problem.

2112:24 GMT (5:12:24 p.m. EDT)

T+plus 2 minutes, 10 seconds. The twin solid rocket boosters have done their job and separated from the space shuttle Discovery. The shuttle continues its climb to orbit on the power of the three liquid-fueled main engines.

2111:44 GMT (5:11:44 p.m. EDT)

T+plus 90 seconds. All systems of Discovery are performing well as the shuttle accelerates to orbit. Burning propellant at remarkable rates, the shuttle weighs half of what it did at liftoff.

2111:14 GMT (5:11:14 p.m. EDT)

T+plus 60 seconds. Discovery's engines have throttled back up.

2110:49 GMT (5:10:49 p.m. EDT)

T+plus 35 seconds. Discovery's three main engines are being throttled down to ease the shuttle's passage through the dense lower altitudes.

2110:34 GMT (5:10:34 p.m. EDT)

T+plus 20 seconds. The shuttle has rolled to a heads-down, wings-level attitude. Houston is controlling the mission of Discovery.

2110:14 GMT (5:10:14 p.m. EDT)

LIFTOFF! Liftoff of space shuttle Discovery launching a new expedition crew to expand the scientific work aboard the international space station. And Discovery has cleared the tower for its 30th trip to space!

2109:43 GMT (5:09:43 p.m. EDT)

T-minus 31 seconds. Auto sequence start. Discovery's onboard computers are taking control of the countdown.

In the next few seconds the solid rocket booster hydraulic power units will be started and the orbiter's body flap and speed brake will be moved to their launch positions. The main engine ignition will begin at T-minus 6.6 seconds.

2109:14 GMT (5:09:14 p.m. EDT)

T-minus 1 minute. Computers verifying that the main engines are ready for ignition. Sound suppression water system is armed. System will activate at T-minus 16 seconds to suppress the sound produced at launch. Residual hydrogen burn ignitors have been armed. They will be fired at T-minus 10 seconds to burn off any hydrogen gas from beneath the main engine nozzles. And the solid rocket booster joint heaters have been deactivated.

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

2108:44 GMT (5:08:44 p.m. EDT)

T-minus 2 minutes, 30 seconds. Orbiter steering check now complete -- the main engine nozzles in their start positions. The external tank liquid oxygen vent valve has been closed and pressurization of the LOX tank has started. Standing by to transfer Discovery's power-producing fuel cells to internal reactants. The units will begin providing all electricity for the mission beginning at T-50 seconds. And pilot Rick Sturckow has been asked to clear the caution and warning memory system aboard Discovery.

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

Coming up on T-minus 2 minutes. The astronauts will be instructed to close and lock the visors on their launch and entry helmets. At T-minus 1 minute, 57 seconds the replenishment of the flight load of liquid hydrogen in the external tank will be terminated and tank pressurization will begin.

2107:44 GMT (5:07:44 p.m. EDT)

T-minus 3 minutes, 30 seconds. The main engine nozzles now being moved through a computer controlled test pattern to demonstrate their readiness to support guidance control during launch today.

2106:14 GMT (5:06:14 p.m. EDT)

T-minus 4 minutes. Activation of the APUs complete. The three units are up and running. The final helium purge sequence is under way in the main propulsion system. This procedure readies fuel system valves for engine start. In the next few seconds the aerosurfaces of Discovery will be run through a pre-planned mobility test to ensure readiness for launch. This is also a dress rehearsal for flight of the orbiter's hydraulic systems.

2105:14 GMT (5:05:14 p.m. EDT)

T-minus 5 minutes. Go for Auxiliary Power Unit start. Pilot Rick Sturckow is now flipping three switches in Discovery's cockpit to start each of the three APU's. The units, located in the aft compartment of Discovery, provide the pressure needed to power the hydraulic systems of the shuttle. The units will be used during the launch and landing phases of the mission for such events are moving the orbiter's aerosurfaces, gimbaling the main engine nozzles and deploying the landing gear.

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

2104:44 GMT (5:04:44 p.m. EDT)

T-minus 5 minutes, 30 seconds. APU pre-start is complete and the units are ready for activation. The orbiters flight data recorders now in the record mode to collect measurements of shuttle systems performance during flight.

2104:14 GMT (5:04:14 p.m. EDT)

T-minus 6 minutes. Pilot Rick Sturckow has been asked by Orbiter Test Conductor Mark Taffet to pre-start the orbiter Auxiliary Power Units. This procedure readies the three APU's for their activation at T-minus 5 minutes.

2102:44 GMT (5:02:44 p.m. EDT)

T-minus 7 minutes, 30 seconds. The ground launch sequencer is now pulling the orbiter access arm away from the crew hatch on the port side of the vehicle. The arm was the passage way for the astronauts to board Discovery a few hours ago. The arm can be re-extended in about a quarter of a minute should the need arise later in the countdown.

2102:14 GMT (5:02:14 p.m. EDT)

T-minus 8 minutes and counting. Pilot Rick Sturckow has flipped the switches in the cockpit of Discovery to directly connect the three onboard fuel cells with the essential power buses. Also, the stored program commands have been issued to the orbiter for the final antenna alignment and management for today's launch.

2101:14 GMT (5:01:14 p.m. EDT)

T-minus 9 minutes and counting. The ground launch sequencer is now controlling the final phase of today's countdown to launch of space shuttle Discovery at 5:10:14 p.m. EDT. The GLS will monitor as many as a thousand different measurements to ensure they do not fall out of predetermine red-line limits.

The launch of STS-105 will mark the 106th flight in the space shuttle program since 1981, the 81st since return-to-flight after Challenger, the 30th for Discovery and the fifth shuttle flight of 2001.

2100:14 GMT (5:00:14 p.m. EDT)

One minute remaining in this built-in hold.

Once the countdown picks up, the Ground Launch Sequencer will be initiated. The master computer program is located in a console in Firing Room 3 of the Complex 39 Launch Control Center. The GLS is the master of events through liftoff. During the last 9 minutes of the countdown, the computer will monitor as many as a thousand different systems and measurements to ensure that they do not fall out of any pre-determine red-line limits. At T-minus 31 seconds, the GLS will hand off to the onboard computers of Discovery to complete their own automatic sequence of events through the final half minute of the countdown.

2057 GMT (4:57 p.m. EDT)

NASA Launch Director Mike Leinbach has polled senior officials and no problems were announced. The local weather conditions have been confirmed "go" for launch! The worrisome forecast today has simply not impacted the Kennedy Space Center weather. Leinbach then gave the clear to proceed to resume the countdown for an on-time launch at 5:10:14 p.m. EDT today.

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

The final readiness poll by NASA Test Director Steve Altemus has been completed with all launch team members reporting "go", including the orbiter, external tank, solid rocket boosters, safety personnel, Eastern Range and the astronaut crew. Mission Control also has given its "go" which indictates weather at the Shuttle Landing Facility and other abort landing sites will not be a factor against launch today.

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

Meteorologists at Mission Control in Houston report the conditions at Kennedy Space Center's shuttle runway that Discovery would use in an emergency landing today are currently observed and forecast "go"! Liftoff set for 5:10:14 p.m. EDT.

2050 GMT (4:50 p.m. EDT)

Now 20 minutes away from Discovery's launch from Kennedy Space Center in Florida to begin the 11th U.S. voyage to the international space station. This smooth countdown remains on schedule for liftoff at 5:10:14 p.m. EDT. There are no problems being reported.

After an 8 1/2-minute climb to orbit, Discovery should achieve an elliptical orbit with a high point of 119 nautical miles and low point of 31 nautical miles. A later firing of the twin orbital maneuvering system engines on the tail of Discovery about 44 minutes into flight will raise the orbit to about 124 by 105 nautical miles as the shuttle chases to catch the space station.

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

NASA Launch Director Mike Leinbach has just made the decision to re-target liftoff for 5:10:14 p.m. EDT at the opening of today's 10-minute window instead of waiting to the middle of the window when it is most optimum for liftoff. By setting up for launch five minutes earlier, it will give NASA a better chance of beating the weather today by not having to wait an extra five minutes when conditions could go out of limits.

For these space station missions the space agency routinely targets the middle of the window -- today that would be 5:15 p.m. -- when the launch pad moves directly into the plane of the international space station, maximizing the shuttle's performance during the climb to orbit.

2034 GMT (4:34 p.m. EDT)

Two solid rocket booster recovery ships -- the Freedom Star and Liberty Star -- are on station in the Atlantic Ocean about 140 miles northeast of Kennedy Space Center, off the coast of Jacksonville, Florida. The ships will retrieve and return the spent boosters to the Cape for disassembly and shipment back to Utah for refurbishment and reuse on a future shuttle launch.

Following the boosters' parachuted descent and splashdown in the Atlantic, the recovery teams will configure the SRBs for tow back to Port Canaveral.

2024 GMT (4:24 p.m. EDT)

Officials are watching some rainshowers to the south of Kennedy Space Center. That's the main threat currently.

2021 GMT (4:21 p.m. EDT)

T-minus 9 minutes and holding. Countdown clocks have gone into the planned 45-minute built-in hold. Today's launch remains set for 5:15 p.m. EDT. There are no significant technical problems being reported and the weather conditions remain within limits at this time.

The flow rate of conditioned air into the payload bay of Discovery has been adjusted and the fuel cell load has been tweaked per the normal plan.

And the Air Force-controlled Eastern Range has verified the Kennedy Space Center area is clear for launch.

2015 GMT (4:15 p.m. EDT)

Now one hour away from launch time. The Orbital Maneuvering System/Reaction Control System crossfeed valves are configured for launch. The Main Propulsion System helium system has been reconfigured. The gaseous nitrogen purge to the aft skirts of the solid rocket boosters is starting. Also, Mission Control in Houston is loading Discovery's onboard computers with the proper guidance parameters based on the projected launch time.

2014 GMT (4:14 p.m. EDT)

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

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

T-minus 20 minutes and counting. The countdown has resumed after a 10-minute hold. Clocks will tick down for the next 11 minutes to T-minus 9 minutes where the final planned hold is scheduled to occur. The hold length will be adjust to synch up with today's preferred launch time of 5:15 p.m. EDT.

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

In about one minute, the astronauts will configure the backup computer to MM-101 and the test team will verify backup flight control system (BFS) computer is tracking the PASS computer systems.

2000 GMT (4:00 p.m. EDT)

T-minus 20 minutes and holding. The countdown has paused for a 10-minute built-in hold. Launch remains scheduled for 5:15 p.m. EDT. There are no technical problems, but the weather continues to be watched closely.

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

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

The primary avionics software system (PASS) is transferring to Discovery's BFS computer so both systems can be synched with the same data. In case of a PASS computer system failure, the BFS computer will take over control of the shuttle vehicle during flight.

1954 GMT (3:54 p.m. EDT)

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

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

Also, the shuttle's backup flight control system (BFS) computer is being configured. It would be used today in the event of emergency landing.

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

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

Discovery's crew was just told by Mission Control that some showers and thunderstorms are popping up to the south of Kennedy Space Center. However, the situation looks a whole lot better today than yesterday.

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

The Orbiter Closeout Crew has completed its job today with the hatch of Discovery sealed for flight. The team is now preparing to depart launch pad 39A and head back to the safety roadblocks.

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

At this point in the countdown the Ground Launch Sequencer mainline activation is performed. Also, the Air Force Eastern Range shuttle safety system terminal count closed-loop test will be performed to verify the countdown can be stopped in the final seconds before liftoff should a safety issue arise.

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

T-minus 1 hour and counting. Two planned holds are built into the count at T-minus 20 minutes and T-minus 9 minutes, leading to launch at 5:15 p.m. EDT. At this time, none of the launch weather rules are being violated.

The pre-flight alignment of Discovery's Inertial Measurement Units is now beginning, and will be completed by the T-minus 20 minute mark. The IMUs were calibrated over the past few hours of the countdown. The three units are used by the onboard navigation systems to determine the position of the orbiter in flight.

Meanwhile, the S-band antennas at the MILA tracking station here at the Cape are shifting from low power to high power. The site will provide voice, data and telemetry relay between Discovery and Mission Control during the first few minutes of flight. Coverage then is handed to a NASA Tracking and Data Relay Satellite in space.

1915 GMT (3:15 p.m. EDT)

Now two hours away from launch time. The countdown is still progressing smoothly with no technical glitches to speak of. The weather is the only concern, and meteorologists are remaining hopeful that conditions will permit liftoff today.

At the moment of launch, the international space station will be sailing 240 miles above Central America and heading toward the Kennedy Space Center. Mission Control plans to uplink live video of the launch to the station's crew -- Yury Usachev, James Voss and Susan Helms. The station will be directly over the Cape a few minutes after launch and controllers told the crew they should be able to see the exhaust plume left by Discovery's twin solid rocket boosters.

1904 GMT (3:04 p.m. EDT)

Discovery's crew module hatch is now swinging shut. Pressure and leak checks will be performed shortly to ensure a good seal on the hatch.

1858 GMT (2:58 p.m. EDT)

The Orbiter Closeout Crew has fixed a problem with the Mission Specialist Patrick Forrester's helmet communications system. This is no impact to today's launch.

1847 GMT (2:47 p.m. EDT)

Voice checks have been performing between the astronauts and ground controllers now that all seven crew members are strapped aboard Discovery. Meteorologists continue to monitor the local weather conditions. There remains some optimism the weather will cooperate today. Thunderstorm development isn't occurring as rapidly as yesterday and there is definitely less cloudiness today.

In the countdown, the booster test conductor will soon verify the chamber pressure in the twin solid rocket motors. Sensors measure pressure in the thrust chambers at nozzles of the boosters. The data tells onboard computers when the boosters have consumed their solid-fuel propellant and should be separated in-flight.

1823 GMT (2:23 p.m. EDT)

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

You can read Barry' biography in our Crew Report.

Meanwhile, the ground launch sequencer software that will control the final nine minutes of the countdown is being initialized as the clock continues to today's planned launch at 5:15 p.m. EDT.

Also, the solid rocket boosters' gas generator heaters in the hydraulic power units are turned on, the aft skirt gaseous nitrogen purge is starting and the rate gyro assemblies (RGAs) are being activated. The RGAs are used by the orbiter's navigation system to determine rates of motion of the boosters during the first-stage flight.

1817 GMT (2:17 p.m. EDT)

Mission specialist No. 5, Mikhail Tyurin, has boarded Discovery. Tyurin will sit in the middeck center seat.

You can read Tyurin's biography in our Crew Report.

1811 GMT (2:11 p.m. EDT)

Discovery's mission specialist No. 1, Patrick Forrester, has boarded the shuttle. He will sit in the flight deck aft right seat.

You can read Forrester's biography in our Crew Report.

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

Discovery's mission specialist No. 3, Frank Culbertson, has boarded the shuttle. He will sit in the middeck left seat.

You can read Culbertson's biography in our Crew Report.

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

Pilot Rick Sturckow has entered the shuttle's hatch. He will sit in the flight deck forward right seat.

You can read Sturckow's biography in our Crew Report.

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

Mission specialist No. 4, Vladimir Dezhurov, has boarded Discovery. Dezhurov will sit in the middeck right seat.

You can read Dezhurov's biography in our Crew Report.

1751 GMT (1:51 p.m. EDT)

Discovery commander Scott Horowitz has become the first astronaut to enter the shuttle today. He will sit in the flight deck forward left seat.

You can read Horowitz's biography in our Crew Report.

The countdown is continuing on track with no technical issues to report. The weather forecast is still poor. However, thunderstorm development isn't occurring as quickly today as yesterday. So there is some hope for acceptable conditions for liftoff at 5:15 p.m. EDT.

1744 GMT (1:44 p.m. EDT)

The crew has taken the elevator to the 195-foot level of the pad structure where the Orbiter Access Arm is located with the White Room. In the White Room the crew will be outfitted with the rest of their gear and communications hat before entering Discovery's crew module hatch. The astronauts did take a few minutes to look at Discovery on the launch pad before heading up the elevator, just as they did yesterday.

1741 GMT (1:41 p.m. EDT)

The shuttle astronauts have arrived at launch pad 39A. They will take the elevator up to the 195-foot level of the fixed service structure to enter Discovery's crew cabin.

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

Discovery's astronauts have embarked on the 20-minute ride in the "AstroVan" from their quarters to launch pad 39A on the edge of the Atlantic Ocean. They walked out of the Operations & Checkout Building in Kennedy Space Center's Industrial Area at 1:24 p.m. EDT.

The AstroVan convoy will stop at the Launch Control Center for the NASA management and NASA astronaut Charlie Precourt to exit the Astrovan. The managers will take their positions in the Firing Room while Precourt heads over to the Shuttle Landing Facility to begin weather reconnaissance flights in a T-38 jet. He will later switch to the modified Gulfstream jet, which is known as the Shuttle Training Aircraft because its flying characteristics are very similar to the space shuttle.

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

T-minus 3 hours and counting. The countdown has resumed from the planned two-hour built-in hold as scheduled. The count will continue to T-minus 20 minutes where the next built-in hold will occur. A final hold is planned at T-minus 9 minutes.

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

Discovery's astronauts are continuing with work to don their day-glow orange partial pressure suits in their quarters at the Operations & Checkout Building. The crew is scheduled to depart for the launch pad at 1:24 p.m. EDT.

Activities are going well in the final hours of today's countdown. There are no technical problems to report, but the weather remains iffy at best for liftoff at 5:15 p.m. EDT.

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

A weather briefing underway for the astronauts shows the prediction of thunderstorms and rain within 20 miles of Kennedy Space Center at launch time, which would be a violation of weather rules. The good news is the weather for overseas abort landing sites won't be an issue today.

1615 GMT (12:15 p.m. EDT)

We are now five hours away from the scheduled launch time for space shuttle Discovery. The seven astronauts have finished lunch in the dining room of the Operations & Checkout Building of Kennedy Space Center, which serves as the crew quarters while they are at the Cape. A weather briefing will be given to the crew shortly before they suit up and head for the launch pad.

There are no technical problems being addressed by the launch team. The only concern for a 5:15 p.m. EDT launch today is the weather, which remains at a 70 percent chance of "no go" conditions.

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

Discovery stands fully fueled and ready for launch from pad 39A at Kennedy Space Center, Florida. A stable replenishment is underway to continuously top-off the respective liquid hydrogen and liquid oxygen tanks within the external tank through the final minutes of the countdown.

Following tanking procedures, a team called the Final Inspection Team was sent to the pad to check the vehicle one last time prior to liftoff. Currently, the six-person team, comprised of five engineers and one safety official, is performing the inspections at pad 39A. At the conclusion of their two-hour tour-of-duty, they will have walked up and down the entire 380-foot fixed service structure and mobile launcher platform.

The team is on the lookout for any abnormal ice or frost build-up on the vehicle that could break-off during ignition and damage the spacecraft. The team is also looking for any loose debris that could possibly fly up and strike the launch vehicle. And the third item of interest to the team is the thermal integrity of the external tank foam insulation.

The team uses a portable infrared scanner that gathers temperature measurements on the surface area of the vehicle 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. One teammember is also responsible for photo documentation.

Each member of the Final Inspection Team is in constant contact with the NASA Test Director in the Firing Room.

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.

Following the Final Inspection Team's activities, the leader will meet with NASA Launch Director Mike Leinbach, the Mission Management Team, and engineering directors in the launch control center, giving a full and detailed report on the team's inspections and findings at the pad 39A.

A full inspection of the vehicle and pad was performed yesterday and the external tank received a thorough check prior to fueling.

An inspection of the launch pad and beach will be made following launch. That inspection will be to look for anything unusual, particularly anything that could have fallen off of the vehicle during the first few seconds of flight. Later there will be a meeting to review high-speed videotape and film of the launch and early ascent to determine if there was any damage to the vehicle.

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

Discovery's has been fueled for launch today at 5:15 p.m. EDT. The loading of 385,000 gallons of liquid hydrogen, chilled to minus 423 degrees Fahrenheit (minus 253 degrees Celsius), was completed at 10:41 a.m. EDT. Tanking of 143,000 gallons of liquid oxygen, chilled to minus 298 degrees Fahrenheit (minus 183 degrees Celsius), wrapped up at 11:07 a.m. EDT.

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.

With tanking completed, the Orbiter Closeout Crew and Final Inspection Team will be dispatched to launch pad 39A to perform their jobs. The closeout crew will ready Discovery's cockpit for the astronauts' boarding in a couple of hours; and the inspection team will give the entire vehicle a check for any ice formation from fueling.

NASA officials said this morning that if Discovery does not fly today, the next launch attempt won't be made until Sunday, with a backup try on Monday. Saturday will be skipped to give the launch team a rest, plus the forecast calls for an 80 percent chance of bad weather. Meteorologists say Sunday and Monday will have a 40 percent chance of unacceptable conditions each day. Should the shuttle not launch by Monday, the liftoff would be delayed at least a couple of days to replenish the onboard fuel cells.

1215 GMT (8:15 a.m. EDT)

For the second straight morning, the space shuttle launch team at Kennedy Space Center are pumping 528,000 gallons of super-cold rocket fueling to Discovery's bullet-shaped external tank in preparation for a possible afternoon liftoff. Today's tanking operation began at 8:11 a.m. EDT and will take about three hours to complete.

And just like yesterday it is a beautiful morning here in Central Florida with blue skies, warm temperatures and a light breeze. But the forecast for the 5:15 p.m. EDT launch time is not promising with just a 30 percent chance weather will allow Discovery to blast off on a 12-day flight to deliver the Expedition Three astronauts to the international space station and return the Expedition Two crew to Earth.

The typical summertime afternoon thunderstorms are again expected to fire up today. And what's worse, meteorologists say the seabreeze thunderstorms likely won't push that far inland today, keeping the storms closer to the coast and the Cape, and winds will be such that the anvil clouds from the storms will drift back toward the east.

So the countdown will roll on with the hope that the weather could possibly cooperate just enough to give Discovery a shot at launching during today's short launch window that extends from 5:10 to 5:20 p.m. The preferred liftoff time that NASA is targeting is 5:15 p.m.

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

The Mission Management Team has given a "go" to begin fueling space shuttle Discovery's external tank with the load of liquid hydrogen and liquid oxygen this morning. The three-hour process will be starting momentarily. Liftoff remains scheduled for 5:15 p.m. EDT today, however, the weather forecast remains 70 percent "no go" due to the thunderstorms.

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

The countdown clock has been recycled back to T-minus 6 hours and holding for this 24-hour postponement of space shuttle Discovery's launch. NASA mission managers will convene a meeting at 7:15 a.m. EDT to review any technical issues and receive a weather briefing before deciding whether to proceed with re-fueling the shuttle for another launch attempt. The weather forecast calls for only a 30 percent chance of favorable conditions for today's 5:15 p.m. EDT liftoff time.

Here is a look at the key events for today's countdown: (all time EDT)

• 07:50 am...Shuttle fueling begins
• 08:20 am...The countdown resumes at the T-6 hour mark
• 09:07 am...Astronaut medical exams
• 11:20 am...The countdown enters a hold at T-3 hours
• 12:00 pm...NASA television coverage begins
• 12:07 pm...Astronaut photo opportunity on NASA TV
• 12:44 pm...The crew gets a final weather briefing
• 12:54 pm...The astronauts don their pressure suits
• 01:20 pm...The countdown resumes at the T-3 hour mark
• 01:24 pm...The astronauts depart crew quarters
• 01:54 pm...The crew begins strapping in for launch
• 03:09 pm...Discovery's hatch is closed
• 04:00 pm...Start T-minus 20 hold
• 04:10 pm...Resume countdown
• 04:21 pm...Start T-minus 9 hold
• 05:06 pm...Resume countdown
• 05:10 pm...Launch window opens
• 05:10 pm...Hydraulic power system startup
• 05:15 pm...Launch

THURSDAY, AUGUST 9, 2001
2112 GMT (5:12 p.m. EDT)

SCRUB! Stormy weather at Kennedy Space Center has forced NASA to scrub today's attempt to launch space shuttle Discovery on its 12-day mission to the international space station. Thunderstorms around Central Florida would simply not allow the shuttle to launch safely today due to lightning, anvil clouds and a high electrical charge in the air. Conditions were also violating the Return-to-Launch-Site abort landing criteria at KSC's shuttle runway.

NASA Launch Director Mike Leinbach said there was "no hope" of conditions improving for today's short five-minute launch window.

Liftoff has been rescheduled for Friday during a window of 5:10:12 to 5:20:11 p.m. EDT. The preferred launch time will be 5:15:12 p.m. EDT. The weather forecast, however, is not good. Meteorologists are calling for a 70 percent chance of conditions violating the launch rules with afternoon thunderstorms expected once again.

In about a half-hour the Orbiter Closeout Crew will return to launch pad 39A to get Discovery's crew module hatch reopened and assist the astronauts egressing the shuttle. Then the external tank will be drained of its half-million gallons of liquid hydrogen and liquid oxygen.

2109 GMT (5:09 p.m. EDT)

Charlie Precourt is taking off again from the shuttle runway to resume weather reconnaissance. He landed earlier due to lightning concerns.

Weather is a constraint not only for launch, but also for the Return-to-Launch-Site abort capability that would allow the shuttle to fly back to KSC for an emergency landing in the event of a major problem during the first minutes of flight.

2106 GMT (5:06 p.m. EDT)

NASA says the weather remains observed and forecast "no go" for launch due to thunderstorms within 20 miles of the shuttle's emergency runway at Kennedy Space Center. A lightning strike was also detected 12 miles away.

2054 GMT (4:54 p.m. EDT)

Launch Director Mike Leinbach just verified with NASA Test Director Steve Altemus that there are no technical problems being worked. However, weather remains "no go" for launch and a decision on the fate of today's attempt is expected shortly.

2049 GMT (4:49 p.m. EDT)

Chief NASA astronaut Charlie Precourt, flying weather reconnaissance around Kennedy Space Center today, is expected to land his Shuttle Training Aircraft shortly. He is reporting lightning just a few miles from the runway at KSC.

The weather picture is very, very poor at this time. In addition to lightning, rules governing the electrical charge in the air and anvil clouds are also "no go" for launch.

2043 GMT (4:43 p.m. EDT)

T-minus 9 minutes and holding. Countdown clocks have gone into the planned 45-minute, 46-second built-in hold. Today's launch remains set for 5:37:46 p.m. EDT. There are no significant technical problems being reported. However, weather conditions remain "no go" at this time.

The flow rate of conditioned air into the payload bay of Discovery has been adjusted and the fuel cell load has been tweaked per the normal plan.

And the Air Force-controlled Eastern Range has verified the Kennedy Space Center area is clear for launch.

2037 GMT (4:37 p.m. EDT)

Now one hour away from launch time. The Orbital Maneuvering System/Reaction Control System crossfeed valves are configured for launch. The Main Propulsion System helium system has been reconfigured. The gaseous nitrogen purge to the aft skirts of the solid rocket boosters is starting. Also, Mission Control in Houston is loading Discovery's onboard computers with the proper guidance parameters based on the projected launch time.

2035 GMT (4:35 p.m. EDT)

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

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

T-minus 20 minutes and counting. The countdown has resumed after a 10-minute hold. Clocks will tick down for the next 11 minutes to T-minus 9 minutes where the final planned hold is scheduled to occur. The hold length will be adjust to synch up with today's preferred launch time of 5:37:46 p.m. EDT. Today's launch window extends to 5:42:46 p.m. EDT.

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

In about one minute, the astronauts will configure the backup computer to MM-101 and the test team will verify backup flight control system (BFS) computer is tracking the PASS computer systems.

2022 GMT (4:22 p.m. EDT)

T-minus 20 minutes and holding. The countdown has paused for a 10-minute built-in hold. Launch remains scheduled for 5:37:46 p.m. EDT. There are no technical problems. Only weather conditions are of concern at this time.

The astronauts have just been radioed that the weather is currently "no go" but there is still time to watch the conditions in hopes of improvement.

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

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

T-minus 22 minutes and counting. Standing by to go into a built-in hold at the T-minus 20 minute mark.

The primary avionics software system (PASS) is transferring to Discovery's BFS computer so both systems can be synched with the same data. In case of a PASS computer system failure, the BFS computer will take over control of the shuttle vehicle during flight.

2016 GMT (4:16 p.m. EDT)

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

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

Also, the shuttle's backup flight control system (BFS) computer is been configured. It would be used today in the event of emergency landing.

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

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

Anvil clouds are towering up to 40,000 feet west of the pad. Over the pad, transparent anvils go up to 38,500 feet, but the non-transparent clouds start one mile west of the pad.

2008 GMT (4:08 p.m. EDT)

The Orbiter Closeout Crew has completed its job today with the hatch of Discovery sealed for flight. The crew is now preparing to depart launch pad 39A and head back to the safety roadblocks.

NASA also reports the red team sent to the pad to fix the backup power supply for the liquid hydrogen recirculation pumps has been successful. Two fuses were replaced to get that backup system now working again.

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

Another check of the weather shows the lightning, anvil cloud and field mill launch rules are currently being violated. The thunderstorms to the west look quite menancing at this time.

1957 GMT (3:57 p.m. EDT)

At this point in the countdown the Ground Launch Sequencer mainline activation is performed. Also, the Air Force Eastern Range shuttle safety system terminal count closed-loop test will be performed to verify the countdown can be stopped in the final seconds before liftoff should a safety issue arise.

The weather concern continues. There are thunderstorms to the west of Kennedy Space Center that are keeping meteorologists busy today tracking them.

1942 GMT (3:42 p.m. EDT)

T-minus 1 hour and counting. The countdown is ticking along to today's scheduled launch at 5:38 p.m. EDT. The pre-flight alignment of Discovery's Inertial Measurement Units is now beginning, and will be completed by the T-minus 20 minute mark. The IMUs were calibrated over the past few hours of the countdown. The three units are used by the onboard navigation systems to determine the position of the orbiter in flight.

Meanwhile, the S-band antennas at the MILA tracking station here at the Cape are shifting from low power to high power. The site will provide voice, data and telemetry relay between Discovery and Mission Control during the first few minutes of flight. Coverage then is handed to a NASA Tracking and Data Relay Satellite in space.

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

The lightning weather rule is "go" again. But the weather is still the main concern at this time. Officially, there is a 40 percent chance weather will prohibit liftoff today.

1922 GMT (3:22 p.m. EDT)

Discovery's crew module hatch is now swinging shut. Pressure and leak checks will be performed shortly to ensure a good seal on the hatch for today's launch.

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

A three-person team is being dispatched to launch pad 39A to inspect the backup power supply for the liquid hydrogen recirculation pumps. That system has gone down. The team will make repairs if possible. At this point, however, this is not a constraint to launch. The primary system is working just fine.

The other technical issued worked today with a front-end processor in the Firing Room has been resolved. A backup system was activated the stable replenish to the liquid oxygen tank has resumed.

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

Weather conditions continue to be monitored at Kennedy Space Center this afternoon. The lightning weather rule is currently being violated. There are thunderstorms forming around Central Florida that meteorologists will have to keep a close eye on during the next 90 minutes of the countdown.

Also in the countdown, the booster test conductor will soon verify the chamber pressure in the twin solid rocket motors. Sensors measure pressure in the thrust chambers at nozzles of the boosters. The data tells onboard computers when the boosters have consumed their solid-fuel propellant and should be separated in-flight.

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

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

You can read Barry' biography in our Crew Report.

Meanwhile, the ground launch sequencer software that will control the final nine minutes of the countdown is being initialized as the clock continues to today's planned launch at 5:38 p.m. EDT.

Also, the solid rocket boosters' gas generator heaters in the hydraulic power units are turned on, the aft skirt gaseous nitrogen purge is starting and the rate gyro assemblies (RGAs) are being activated. The RGAs are used by the orbiter's navigation system to determine rates of motion of the boosters during the first-stage flight.

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

Mission specialist No. 5, Mikhail Tyurin, has boarded Discovery. Tyurin will sit in the middeck center seat.

You can read Tyurin's biography in our Crew Report.

1833 GMT (2:33 p.m. EDT)

The launch team is working two technical issues at this time. A front-end processor in the the launch control center has gone down. The computer had been registering an overpressure condition in the liquid oxygen tank of Discovery's external fuel tank. However, the shuttle is safe and this was just a computer glitch. The replenishment to LOX tank has been stopped, however, while the launch team switched to a backup processor. But there is plenty of time left in the countdown to get replenishment restarted and properly condition the external tank's liquid oxygen supply for flight.

Also, the backup power supply system for the liquid hydrogen recirculation pumps has gone down. The primary is still working. NASA is discussing sending a team to the pad to investigate the backup system.

Meanwhile, Discovery's mission specialist No. 1, Patrick Forrester, has boarded the shuttle. He will sit in the flight deck aft right seat.

You can read Forrester's biography in our Crew Report.

1829 GMT (2:29 p.m. EDT)

Discovery's mission specialist No. 3, Frank Culbertson, has boarded the shuttle. He will sit in the middeck left seat.

You can read Culbertson's biography in our Crew Report.

1823 GMT (2:23 p.m. EDT)

Pilot Rick Sturckow has entered the shuttle's hatch. He will sit in the flight deck forward right seat.

You can read Sturckow's biography in our Crew Report.

1817 GMT (2:17 p.m. EDT)

Mission specialist No. 4, Vladimir Dezhurov, has boarded Discovery. Dezhurov will sit in the middeck right seat.

You can read Dezhurov's biography in our Crew Report.

1814 GMT (2:14 p.m. EDT)

Discovery commander Scott Horowitz has become the first astronaut to enter the shuttle today. He will sit in the flight deck forward left seat.

You can read Horowitz's biography in our Crew Report.

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

The crew has taken the elevator to the 195-foot level of the pad structure where the Orbiter Access Arm is located with the White Room. In the White Room the crew will be outfitted with the rest of their gear and communications hat before entering Discovery's crew module hatch. The astronauts did take a few minutes to look at Discovery on the launch pad before heading up the elevator.

1805 GMT (2:05 p.m. EDT)

The shuttle astronauts have arrived at launch pad 39A. They will take the elevator up to the 195-foot level of the fixed service structure to enter Discovery's crew cabin.

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

Discovery's astronauts have embarked on the 20-minute ride in the "AstroVan" from their quarters to launch pad 39A on the edge of the Atlantic Ocean. They departed the Operations & Checkout Building in Kennedy Space Center's Industrial Area at 1:48 p.m. EDT.

The AstroVan convoy will stop at the Launch Control Center for the NASA management and NASA astronaut Charlie Precourt to exit the Astrovan. The managers will take their positions in the Firing Room while Precourt heads over to the Shuttle Landing Facility to begin weather reconnaissance flights in a T-38 jet. He will later switch to the modified Gulfstream jet, which is known as the Shuttle Training Aircraft because its flying characteristics are very similar to the space shuttle.

1725 GMT (1:25 p.m. EDT)

The crew of space shuttle Discovery are running checks on their pressure suits following a routine pre-flight weather briefing with flight controllers in Houston. Weather continues to look generally favorable, but controllers will be keeping a close watch for thunderstorms in the vicinity of the launch site.

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

The seven astronauts -- Discovery commander Scott Horowitz, pilot Rick Sturckow, mission specialists Patrick Forrester and Dan Barry, and the Expedition Three crew of commander Frank Culbertson and Russian cosmonauts Vladimir Dezhurov and Mikhail Tyurin -- are in the dining room at the Operation & Checkout Building for the traditional photo opportunity in front of the mission cake.

A weather briefing for the commander Horowitz, pilot Sturckow and flight engineer Barry is planned for 1 p.m. At the same time, the rest of the crew will start donning their launch and entry spacesuits. Once the weather update concludes, all seven astronauts will be reunited in the suit-up room.

Departure from the crew quarters for the 20-minute ride to launch pad 39A is expected at around 1:47 p.m. After arriving at the seaside pad, the astronauts will immediately begin boarding Discovery. The crew module hatch should be closed for flight at around 3:30 p.m.

THURSDAY, AUGUST 9, 2001
1600 GMT (12:00 p.m. EDT)

Good day from Kennedy Space Center in Florida where the countdown is entering the final five-and-a-half hours for the launch of space shuttle Discovery carrying the Expedition Three crew to the international space station. Liftoff is scheduled for 5:37:46 p.m. EDT (2137:46 GMT). There are no problems to report at this time.

Discovery stands fully fueled and ready for launch from pad 39A at Kennedy Space Center, Florida. The loading of 528,000 gallons of liquid oxygen and liquid hydrogen into the external tank began at 8:20 a.m. EDT. The operation went smoothly and was completed at 11:15 a.m. EDT. A stable replenishment mode then started to continuously top-off the respective tanks within the external tank through the final minutes of the countdown.

Following tanking procedures, a team called the Final Inspection Team was dispatched to the pad to check the vehicle one last time prior to liftoff. Currently, the six-person team, comprised of five engineers and one safety official, is performing the inspections at pad 39A. At the conclusion of their two-hour tour-of-duty, they will have walked up and down the entire 380-foot fixed service structure and mobile launcher platform.

The team is on the lookout for any abnormal ice or frost build-up on the vehicle that could break-off during ignition and damage the spacecraft. The team, which is headed by Greg Katnik of the Kennedy Space Center, is also looking for any loose debris that could possibly fly up and strike the launch vehicle. And the third item of interest to the team is the thermal integrity of the external tank foam insulation.

The team uses a portable infrared scanner that gathers temperature measurements on the surface area of the vehicle 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. One teammember is also responsible for photo documentation.

Each member of the Final Inspection Team is in constant contact with the NASA Test Director in the Firing Room.

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.

Following the Final Inspection Team's activities, Greg Katnik will meet with NASA Launch Director Mike Leinbach, the Mission Management Team, and engineering directors in the launch control center. Katnik will give the managers a full and detailed report on the team's inspections and findings at the pad 39A.

A full inspection of the vehicle and pad was performed yesterday and the external tank received a thorough check prior to fueling.

An inspection of the launch pad and beach will be made following launch. That inspection will be to look for anything unusual, particularly anything that could have fallen off of the vehicle during the first few seconds of flight. Later there will be a meeting to review high-speed videotape and film of the launch and early ascent to determine if there was any damage to the vehicle.

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

FUELING COMPLETED. Loading of shuttle Discovery's external tank has been completed. A stable replenishment is now underway to continuously top-off the liquid hydrogen and liquid oxygen supplies to replace the cryogenics that naturally boil away during the remainder of the countdown.

With fueling wrapped up, 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 cockpit for the astronauts' boarding in a couple of hours; and the inspection team will give the entire vehicle a check for any ice formation from fueling.

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

FUELING BEGINS! NASA has started loading space shuttle Discovery's external fuel tank with 528,000 gallons of super-cold liquid hydrogen and liquid oxygen. Tanking began at about 8:20 a.m. EDT (1220 GMT) and will take about three hours to complete.

The fueling process is being orchestrated by engineers in the safe confines of the Kennedy Space Center's Launch Control Center some four miles from Discovery at launch pad 39A.

The bullet-shaped external tank is being filled with 385,000 gallons of liquid hydrogen chilled to minus 423 degrees Fahrenheit (minus 253 degrees Celsius) and 143,000 gallons of liquid oxygen chilled to minus 298 degrees Fahrenheit (minus 183 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.

NASA officials are not reporting any technical problems and the countdown continues to the planned 5:38 p.m. EDT liftoff. The launch time weather forecast remains the same -- a 60 percent chance of acceptable conditions.

0300 GMT (11:00 p.m. EDT Wed.)

The gantry-like rotating service structure has been rolled away from space shuttle Discovery and into the launch position at pad 39A tonight as the countdown presses ahead for liftoff at 5:38 p.m. EDT.

Today workers checked out the shuttle's star trackers, activated the three Inertial Measurement Units, stowed the rest of the astronauts' equipment and activated the ground communications network.

Some of the chores to be performed overnight include the methodical job for positioning all switches in Discovery's cockpit to their proper launch configuration, resuming the countdown at 1:42 a.m. EDT from the planned hold at T-minus 11 hours, activating Discovery's three electricity-generating fuel cells at 2:52 a.m. and clearing the blast danger area around the pad of all non-essential personnel at about 3:45 a.m.

Fueling of Discovery's external tank with a half-million gallons of liquid oxygen and liquid hydrogen should begin around 8:30 a.m. The process will take three hours to complete.

The Mission Management Team will meet at 7:45 a.m. to review the weather and any technical concerns before giving approval for fueling to commence.

Overall there is still a 40 percent chance weather will be "no-go" for liftoff due to showers and thunderstorms in the area.

The seven astronauts will be awakened for launch at 7:30 a.m. and be seated for breakfast at 8 a.m. At 12 noon they will have lunch and at 1 p.m. they will be given a final update on the launch time weather forecast. Following the weather briefing they will don their launch suits and depart for the pad at 1:47 p.m. The hatch will be closed for flight at about 3:30 p.m.

WEDNESDAY, AUGUST 8, 2001
1400 GMT (10:00 a.m. EDT)

Discovery's fuel cell storage tanks located beneath the payload bay have been successfully filled with liquid hydrogen and liquid oxygen. NASA officials report the countdown remains on track to support liftoff on Thursday at 5:37:47 p.m. EDT.

Other activities underway this morning include final preparations of Discovery's main engines, filling the pad sound suppression system water tank and closing out the tail service masts on the mobile launcher platform.

Rollback of the rotating service structure from around Discovery is planned for 9:30 p.m. EDT tonight.

The weather forecast remains unchanged with a 60 percent chance of conditions being "go" for an on-time launch.

TUESDAY, AUGUST 7, 2001
2010 GMT (4:10 p.m. EDT)

Space shuttle Discovery's three electricity-generating fuel cells will be loaded with liquid hydrogen and liquid oxygen reactants at launch pad 39A this afternoon as the countdown continues for Thursday's planned blastoff. The cryogenics will be combined to generate power for the shuttle's systems and drinking water for the astronauts during the planned 12-day mission.

The latest update to the launch window shows a 9-minute, 59-second opportunity from 5:32:47 to 5:42:46 p.m. EDT. The preferred launch time that NASA will likely target is 5:37:47 p.m. EDT as the shuttle's pad moves directly into the plane of the international space station's orbit.

Since the countdown began Monday the activities have included starting the final close-outs of the space shuttle and launch pad 39A facilities, reviewing the flight software loaded into Discovery's mass memory units and display systems, loading the backup flight system software into the General Purpose Computers, activating and testing the shuttle's navigational systems and checking the pyrotechnic initiator controllers.

Senior space shuttle and space station managers met this afternoon for the traditional L-2 management meeting with no significant problems reported.

The weather is still calling for a 60 percent chance of acceptable conditions for Thursday's launch opportunity. Launch Weather Officer Ed Priselac issued this summary today:

"Low level southeast flow on Thursday expected to push sea breeze front west of KSC during the afternoon and evening. However, weak southwest flow aloft could move sea breeze front and associated weather eastward toward the launch area. Of additional interest, is weak upper low over the southeast Bahamas. The weak low and associated trough are expected to be southeast of Florida on launch day. If the tropical wave is closer to central Florida, it would increase the chance of local showers and thunderstorms."

The launch time conditions are predicted to include scattered cumulus clouds at 4,000 feet with 3/8ths sky coverage, scattered altocumulus clouds at 10,000 feet with 3/8ths sky coverage and scattered cirrus clouds at 25,000 feet with 3/8ths sky coverage, visibility of 7 miles, southeasterly winds from 120 degrees at 10 peaking to 14 knots, a temperature of 82 degrees F, relative humidity of 74 percent and a chance of showers/thunderstorms in the area.

Should the launch slip to Friday or Saturday for some reason, there is just a 30 percent chance of good weather each day due to showers and thunderstorms.

MONDAY, AUGUST 6, 2001
2218 GMT (6:18 p.m. EDT)

Space shuttle Discovery has been cleared for launch. NASA managers just formally decided the shuttle can fly "as is" and the cracked fuel injector issue does not pose a safety threat to Discovery.

Officials held about a half-dozen meetings over the past few days to debate the possibility of replacing one of the hydraulic power units on Discovery's left-hand solid rocket booster as a precaution. But in the end it was ruled unnecessary.

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

COUNTDOWN BEGINS. The three-day countdown is underway at Kennedy Space Center for Thursday's launch of space shuttle Discovery on a taxi mission to exchange the resident crews of the international space station. Liftoff is planned for 5:37:47 p.m. EDT.

Space agency officials meeting this afternoon to review the cracked solid rocket booster hydraulic power unit injector stem gave a provisional "go" for the launch. However, one additional injector was being inspected this afternoon and another meeting is slated for 6 p.m. EDT to resolve the issue once and for all.

The countdown was started from the T-43 hour mark. The count includes over 29 hours of planned hold time. The launch team is controlling the count from Firing Room 3 of the Complex 39 Launch Control Center.

Launch Weather Officer Ed Priselac is predicting a 60 percent chance of acceptable conditions on Thursday. The concern will be thunderstorms. Conditions are expected to worsen to 70 percent "no go" for launch attempts Friday and Saturday.

"All our flight and ground systems are performing well, the team's focused and prepared for launch countdown this evening," said NASA test director Steve Altemus told reporters earlier today. "If Ed can keep those thunderstorms at bay, we'll see a spectacular launch on Thursday afternoon."

SUNDAY, AUGUST 5, 2001
2312 GMT (7:12 p.m. EDT)

NASA officials have again put off making a final decision whether one of space shuttle Discovery's solid rocket booster hydraulic power units should be replaced. For now, activities continue on schedule at Kennedy Space Center for Thursday's planned 5:38 p.m. EDT blastoff.

A fuel injector that operates in conjunction with the power unit's turbine was called into question after an identical device made at the same time in the early 1980s was recently found to be cracked, touching off last-minute tests and analysis to determine if Discovery can launch safely "as is" or if the HPU should be removed and replaced.

Engineers believe the cracked injector stem was somehow bent during ground processing, which officials say is probably what led to corrosion and cracking.

Overnight engineers inspected 38 un-bent injectors and no further units were found to be cracked. The tests were run on two manufacturing batches -- Series 5000 that includes the one with the crack and the one on Discovery and Series 5100.

There was one un-bent injector, however, that had "suspicious markings." The injector will be cleaned and re-inspected to determine if the markings are cracks or something else.

It will be critical to determine if the marks are ruled cracks because that will thwart engineers' theory that bent stems cause the cracking.

Documentation shows the injector in question on Discovery is not bent.

Officials will hold another teleconference at 2 p.m. EDT tomorrow to make a final decision whether to replace the power unit on Discovery, a job that would delay launch at least a few days.

1722 GMT (1:22 p.m. EDT)

The seven astronauts who will ride space shuttle Discovery into orbit during this week's scheduled launch arrived at Kennedy Space Center today amid ongoing analysis about cracks found in a critical solid rocket booster system.

The main goal of Discovery's mission is delivering the Expedition Three crew to the international space station and returning the Expedition Two astronauts to Earth after their five-month stay on the orbiting outpost.

Liftoff remains targeted for 5:38 p.m. EDT (2138 GMT) Thursday. However, NASA officials will hold a teleconference late this afternoon to decide if a hydraulic power unit on Discovery's left-hand solid rocket booster will have to be replaced. Such a replacement effort would delay the launch approximately three to four days.

Each booster has two independent hydraulic power units that gimbal the rocket's nozzle to provide the primary means of steering the shuttle during launch. A hydraulic system failure could have catastrophic consequences.

The concern was raised after the solid rocket booster program found cracks in fuel injector device that is internal to the workings of the hydraulic power unit. The "stress corrosion" cracks were found on the stem of the injector that hasn't flown since STS-84 in 1997.

The cracked injector comes from a specific manufacturing batch that also includes an injector that is inside one of Discovery's hydraulic power units. About 20 percent of injectors in the shuttle fleet come from this same "lot."

Engineers have determined the cracked injector was somehow bent during ground processing, which officials say is probably what led to the corrosion and cracking. Boroscope testing was slated to begin Saturday on other injectors that aren't bent to see if any cracking had occurred on those units.

Documentation shows the injector in question on Discovery is not bent. So if the theory that only bent injectors will corrode and crack, then it stands to reason that Discovery is safe to fly.

Booster engineers on Saturday, however, were still recommending replacing the hydraulic power unit on Discovery as a precaution.

Word from today's management meeting is expected around 6 p.m. EDT at the earliest.

Discovery's astronauts, meanwhile, are gearing up for liftoff while the Kennedy Space Center launch team prepares to begin the three-day countdown. Clocks should begin ticking at 5 p.m. EDT Monday.

"The 105 crew is real excited to be down here for launch week. We've prepared a long time," Discovery commander Scott Horowitz told reporters gathered at the runway to cover the astronauts' Florida arrival. The crew flew from Houston to Kennedy Space Center in four T-38 jet trainers, touching down at the Shuttle Landing Facility at about 1:15 p.m. EDT.

The astronauts will spend the next few days reviewing their flight plans, undergoing medical exams, practicing landing approaches at the runway and relaxing with family members.

Horowitz will be joined during launch by pilot Rick Sturckow, mission specialists Patrick Forrester and Dan Barry, and the Expedition Three crew of commander Frank Culbertson and Russian cosmonauts Vladimir Dezhurov and Mikhail Tyurin.

While docked to the space station the Expedition Three crew will move into Alpha, replacing Expedition Two of commander Yuri Usachev and Americans Jim Voss and Susan Helms. The outgoing crew will board Discovery for the trip back home after spending five months in orbit.

Discovery is also carrying the Italian-built Leonardo cargo module that will be lifted from its payload bay and docked to the station using the shuttle's robotic arm. The astronauts will unload the supplies, equipment and new science experiments from the reusable module and then stuff it with trash and unneeded material. Leonardo will be returned to the shuttle for the ride back to Earth.

This 105th space shuttle mission, the 30th for Discovery, is scheduled to last 11 days and 20 hours with landing back at Kennedy Space Center on August 21 at about 1:17 p.m. EDT.

Read our earlier status center coverage.