BY SPACEFLIGHT NOW

Follow the shift change between the first and second Expedition Crews leaving aboard the international space station as well as the STS-102 flight of space shuttle Discovery. Reload this page for the very latest.

WEDNESDAY, MARCH 21, 2001
0910 GMT (4:10 a.m. EST)

We will pause our coverage at this time. NASA is planning a news conference with at least some, if not all, of the STS-102 crew at around 8:30 a.m. EST. A video taped message from Expedition One is expected to follow about an hour later.

In the meantime, you can read our complete landing story.

0905 GMT (4:05 a.m. EST)

Discovery commander Jim Wetherbee reports the Expedition One astronauts are doing well after their 141-day stay in space. "They are up and walking around inside the CTV (People Mover)," Wetherbee said.

0901 GMT (4:01 a.m. EST)

The four STS-102 astronauts are now taking the traditional tour around the shuttle on runway and kicking the tires after the 12-day, 20-hour, 5.3-million mile voyage. The Expedition One crew remains inside the People Mover.

0839 GMT (3:39 a.m. EST)

The CTV People Mover has now rolled away from Discovery. It is expected at least some of the four STS-102 shuttle astronauts will make the customary walkaround inspection of Discovery on the runway.

0816 GMT (3:16 a.m. EST)

The astronauts are now reported off the shuttle. They are currently inside the motorized Crew Transport Vehicle. It is expected that at least some of the shuttle astronauts will make the traditional walkaround of the Discovery on the runway shortly. The Expedition One crew most certainly won't, however.

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

0810 GMT (3:10 a.m. EST)

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

0800 GMT (3:00 a.m. EST)

Discovery's side hatch is now open for the astronauts to exit the shuttle. The Expedition One crew is expected to be carried off the orbiter by medical personnel.

0749 GMT (2:49 a.m. EST)

The main engine nozzles have been moved to the "rain drain" position and Discovery's three Auxiliary Power Units are being shut down.

0747 GMT (2:47 a.m. EST)

Post-landing chores continue for the astronauts to configure the shuttle after their homecoming. The shuttle's onboard computers have transitioned to the post-landing software package. The side hatch and drag chute pyrotechnics have been safed. Landing gear reported safed. And Mission Control has told the crew they can now remove their launch and entry space suits if so desired.

0740 GMT (2:40 a.m. EST)

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

Main Gear Touchdown
2:31:41 a.m. EST
MET: 12 days, 19 hours, 49 minutes, 32 seconds

Nose Gear Touchdown
2:31:52 a.m. EST
MET: 12 days, 19 hours, 49 minutes, 43 seconds

Wheels Stop
2:33:06 a.m. EST
MET: 12 days, 19 hours, 51 minutes, 57 seconds

0737 GMT (2:37 a.m. EST)

The astronauts are going through standard post-landing safing of Discovery following a smooth touchdown today. The body flap has been set and the external tank umbilical doors on the shuttle's belly have been opened. On the runway, workers have arrived with instruments to "sniff" the shuttle's exterior to check for any hazardous vapors.

0734 GMT (2:34 a.m. EST)

The Expedition One crew of commander Bill Shepherd, pilot Yuri Gidzenko and flight engineer Sergei Krikalev are back on Earth after 141 days in space. Their vanguard mission to the international space station began on October 31 with launch aboard a Russian Soyuz rocket.

Shepherd has now logged 159 days in space on four flights; Gidzenko has logged 320 days on two flights; and Krikalev has now completed five missions totaling 625 days in orbit.

0732 GMT (2:32 a.m. EST)

WHEELS STOP. Discovery has rolled to a stop at Kennedy Space Center, bringing to an end the 141-day voyage of Expedition One that began the continual human presence in space.

0731 GMT (2:31 a.m. EST)

TOUCHDOWN! Main gear touchdown. Nose gear touchdown. Drag chute deployed. Space shuttle Discovery rolls out on Runway 15 at the Kennedy Space Center to complete a successful 5.3-million mile mission that delivered the Expedition Two crew and five tons of equipment, experiments and supplies to the international space station.

0731 GMT (2:31 a.m. EST)

Landing gear down and locked. Standing by for touchdown on Kennedy Space Center's Runway 15.

0730 GMT (2:30 a.m. EST)

Field in sight. Commander Wetherbee can see the runway as he pilots Discovery to the 17th nighttime landing in shuttle program history. The shuttle descending at a rate seven times steeper than that of a commercial airliner.

0729 GMT (2:29 a.m. EST)

Discovery is in the Heading Alignment Cylinder, an imaginary circle to align with Runway 15. Jim Wetherbee will make a 264-degree left-overhead turn. Altitude under 40,000 feet.

0728 GMT (2:28 a.m. EST)

Commander Jim Wetherbee has taken manual control of Discovery. The sonic booms have been heard at KSC, announcing the shuttle's arrival.

0727 GMT (2:27 a.m. EST)

Discovery's wings are leveling out. Shuttle right on course as pilot Jim Kelly tries his hand at the controls.

0726 GMT (2:26 a.m. EST)

Now five minutes from landing at the Kennedy Space Center. Drag chute deployment will occur after nose gear touchdown -- later than normal to perform the crosswind Detailed Test Objective. The surface winds are from 240 degrees at 9 peaking to 15 knots.

0724 GMT (2:24 a.m. EST)

Now seven minutes to landing. Altitude is 17 miles as Discovery streaks above Central Florida. Infrared cameras have spotted the shuttle.

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

0723 GMT (2:23 a.m. EST)

Discovery nearing the west coast of Florida over the Clearwater area with 8 minutes remaining to touchdown. Range to touchdown 147 miles.

0722 GMT (2:22 a.m. EST)

Discovery now banking back to right. This is the third of four turns to reduce speed.

0721 GMT (2:21 a.m. EST)

Discovery remains on the proper track for landing in 10 minutes at KSC. Touchdown predicted to be 2,500 feet down the runway.

Altitude now 27 miles, range to the runway 274 miles, speed down to Mach 5.

0720 GMT (2:20 a.m. EST)

The Merritt Island tracking station called MILA has locked on to signal from space shuttle Discovery. This provides more detailed navigation data for tracking the spaceplane as it streaks to touchdown at Kennedy Space Center.

And the TACAN navigation units aboard Discovery are now receiving data from beacons located at the ground.

0717 GMT (2:17 a.m. EST)

Distance to the runway 700 miles. Descending at a rate of 114 feet per second.

0716 GMT (2:16 a.m. EST)

Inside the final 15 minutes of flight. The shuttle is now 37 miles above the Gulf of Mexico on a northeasterly track to Kennedy Space Center. Range to touchdown now 930 miles.

The shuttle's thrusters used for pitch have been disabled with the aerosurfaces now being used for this control.

0715 GMT (2:15 a.m. EST)

Discovery is beginning the first roll reversal. The shuttle rolling from its bank to right to a left-hand bank.

0713 GMT (2:13 a.m. EST)

Discovery is now making landfall over southern Mexico.

0712 GMT (2:12 a.m. EST)

Mission Control reports Discovery is right on the proper track. No problems to speak of.

0711 GMT (2:11 a.m. EST)

Now 20 minutes until landing. Discovery's speed is currently at Mach 15, range to the runway is 2,200 miles.

Landing today will occur on Runway 15 at the Kennedy Space Center -- the northwest to southeast strip of the Shuttle Landing Facility. Upon arrival at the heading alignment circle in skies over KSC, commander Jim Wetherbee will make a 264-degree left-overhead turn to align Discovery with the runway. Touchdown is expected at 2:31 a.m. EST.

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

0708 GMT (2:08 a.m. EST)

The roll control jets on the shuttle are being turned off and the aerosurfaces on the spacecraft now able to be used as the vehicle continues descent into the atmosphere. All the wing flaps will be active shortly with the exception of the rudder, which won't be useful until the shuttle slows to Mach 5.

0706 GMT (2:06 a.m. EST)

Now 25 minutes to landing. Distance from Kennedy Space Center is 3,300 miles. Altitude currently 47 miles over the Central Pacific Ocean approaching the equator. Speed 16,000 miles per hour.

0705 GMT (2:05 a.m. EST)

The space shuttle is currently in the first of four steep banks to scrub off speed as it plunges into the atmosphere. This is a 75-degree or so roll to the right. These turns basically remove the energy Discovery built up during launch. Mission Control is out of normal communications with the shuttle during the roll maneuver due to heating conditions and the angle of antennas on the shuttle facing away from NASA's orbiting Tracking and Data Relay Satellites.

0704 GMT (2:04 a.m. EST)

Altitude 53 miles. Descending at a rate of 400 feet per second. Distance to the runway 4,000 miles.

0700 GMT (2:00 a.m. EST)

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

The shuttle is flying with its nose elevated 40 degrees, wings level, at an altitude of 400,000 feet, passing over the southern Pacific Ocean, about 4,300 nautical miles from the landing site, at a velocity of Mach 25, descending at a rate of 500 feet per second.

Touchdown is set for 0731 GMT (2:31 a.m. EST) on Runway 15 at Kennedy Space Center in Florida.

0655 GMT (1:55 a.m. EST)

Discovery's onboard computers now switching to the OPS-304 program, which governs entry phase of the mission. Now 36 minutes until landing. Discovery currently above the South Pacific Ocean, east of New Zealand, continuing to fall closer and closer to the atmosphere. Altitude currently 100 miles. Range to the runway some 6,200 miles.

0648 GMT (1:48 a.m. EST)

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

Also, excess propellant has been dumped from the shuttle's steering jets.

0641 GMT (1:41 a.m. EST)

Now 50 minutes from touchdown.

The shuttle's track home is taking the craft above the Pacific Ocean on northeastward track towards Kennedy Space Center. The shuttle will make landfall above southern Mexico before moving out over the Gulf of Mexico towards the United States. Discovery will arrive over Florida above Clearwater and Tampa and continue across the central portion of the state, skirting just south of Orlando. Once in the vicinity of KSC, Commander Wetherbee will perform a 264-degree left-overhead turn to align with Runway 15 -- the northwest to southeast runway -- by making a swing out of the Atlantic Ocean.

0633 GMT (1:33 a.m. EST)

Onboard guidance is maneuvering Discovery from its upside down, tail-forward position needed for the deorbit burn to the reentry configuration of heads-up and nose-forward. The nose also will be pitched upward 40 degrees. In this new position, the black tiles on the shuttle's belly will shield the spacecraft during the fiery plunge through the Earth's atmosphere with temperatures reaching 3,000 degrees F. Discovery will begin interacting with the upper fringes of the atmosphere above the South Pacific in about 26 minutes.

0629 GMT (1:29 a.m. EST)

DEORBIT BURN COMPLETE. Discovery has successfully completed the deorbit burn, committing the shuttle for its journey back to Earth. Landing is scheduled for 2:31 a.m. EST on Runway 15 at Kennedy Space Center in Florida.

Today's landing will be the 54th to occur at Kennedy Space Center in the history of space shuttle program. Dating back to May 1996, this will mark the 32nd of the last 35 shuttle missions to land in Florida. KSC is the most used landing site for the shuttle. Edwards Air Force Base in California has seen 47 landings and White Sands in New Mexico supported one. This also will be the 17th night landing for a space shuttle and the 12th to occur at KSC.

0626 GMT (1:26 a.m. EST)

DEORBIT BURN IGNITION. Flying upside down and backwards 235 miles above the central Indian Ocean northwest of Australia, Discovery has begun the deorbit burn. The firing of the two Orbital Maneuvering System engines on the tail of the shuttle will last two-minutes, 54-seconds, slowing the craft by about 303 feet per second, just enough to slip from orbit. The retro-burn will send Discovery towards a touchdown at 2:31 a.m. EST on a runway just miles from the Kennedy Space Center launch pad where the shuttle lifted off 12 days, 18 hours and 44 minutes ago.

0622 GMT (1:22 a.m. EST)

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

Meteorologists in Mission Control has verified conditions at the Kennedy Space Center remain favorable. There are no rainshowers in the immediate area, a light wind and starry skies.

0614 GMT (1:14 a.m. EST)

Discovery is performing maneuvers in space to the deorbit burn attitude. The shuttle will be flying upside-down and backwards with its tail pointed in the direction of travel. The upcoming burn, now 12 minutes away, will slow Discovery below orbital velocity, allowing the craft to slip from space and begin the hour-long glide to a pin-point touchdown at 2:31 a.m. EST (0731 GMT) at Florida's Kennedy Space Center.

0611 GMT (1:11 a.m. EST)

All seven astronauts aboard Discovery should be strapped into their seats at this point. For today's reentry there is a unique seating arrangement in place. Instead of four crew members on the flightdeck and three on the middeck, those numbers are reversed today because of the special circumstances surrounding the return of the Expedition One astronauts to Earth after 141 days in space.

On the flight deck is commander Jim Wetherbee, pilot Jim Kelly and flight engineer Paul Richards. Downstairs Andy Thomas is there to aid the former international space station residents Bill Shepherd, Yuri Gidzenko and Sergei Krikalev as they ride back to the planet. The three Expedition One astronauts are resting on their backs in recumbent seats to ease their return to gravity.

You can read more about the medical challenges that face the Expedition One crew following their space voyage in our full story.

Meanwhile, the shuttle astronauts have deactivated the toilet, the shuttle's vent doors have been closed and final configuring of the onboard computers and a steering check of the orbital maneuvering system engine nozzles have been completed.

0601 GMT (1:01 a.m. EST)

Now 90 minutes away from Discovery's scheduled landing at Kennedy Space Center.

0555 GMT (12:55 a.m. EST)

GO FOR THE DEORBIT BURN! Following an amazing improvement in the weather tonight at Florida's Kennedy Space Center, Entry Flight Director Wayne Hale in Mission Control has given space shuttle Discovery's astronauts the "go" to perform the deorbit burn at 1:26 a.m. EST (0626 GMT).

Just a couple hours ago, NASA believed there was no hope that low clouds and crosswinds at the three-mile Shuttle Landing Facility would be within limits for Discovery's homecoming. But a low pressure system affecting the Southeastern U.S. has moved northward faster than originally envisioned, allowing the winds to ease and drier air caused low clouds to dissipate, NASA meteorologists reported.

The upcoming retrograde burn using the twin orbital maneuvering system engines on the tail of Discovery will last two-minutes, 54-seconds to slow the shuttle's velocity by just over 200 miles per hour, just enough to slip the craft out of orbit and begin the plunge back into the atmosphere.

Discovery is headed to a nighttime landing at 2:31 a.m. EST (0731 GMT) on Runway 15 at KSC. The landing will conclude the 12-day, 19-hour STS-102 mission and ferry the Expedition One astronauts back to Earth after their 141-day voyage to shake down the international space station.

0554 GMT (12:54 a.m. EST)

The final weather update from meteorologists in Mission Control indicates conditions at Kennedy Space Center are currently acceptable and expected to remain that way for landing time.

0547 GMT (12:47 a.m. EST)

The last hurdle remaining tonight are these small, isolated rainshowers around Central Florida. If meteorologists can assure themselves that the showers won't be a violation of landing rules, then Discovery likely be cleared for touchdown at 2:31 a.m. EST.

0545 GMT (12:45 a.m. EST)

The crew is performing a steering check of the Orbiter Maneuvering System thrust vector control. And pilot Jim Kelly has completed the Auxiliary Power Unit prestart, which positions switches in the cockpit in the ready-to-start configuration.

0542 GMT (12:42 a.m. EST)

Chief NASA astronaut Charlie Precourt -- flying the Shuttle Training Aircraft for weather reconnaissance around Kennedy Space Center -- is making a final run to both ends of the KSC runway. A decision on the fate of this last shot at landing in Florida today is upcoming in about 20 minutes.

0522 GMT (12:22 a.m. EST)

The crew of space shuttle Discovery was just told by Mission Control that the weather picture at Kennedy Space Center is getting better. However, a final decision on whether the shuttle can come home today has not yet been made.

At present, the observed conditions are acceptable with a few clouds at 3,800, visibility of 10 miles and winds from 245 degrees at 7 peaking to 9 knots.

The forecast for landing time at 2:31 a.m. EST calls for scattered clouds at 7,000 feet, seven miles visibility and winds from 260 degrees at 8 peaking to 13 knots. The main concern is the chance of rainshowers within 30 miles of the runway. The weather reconnaissance aircraft is taking a look at those showers to see they are truly a factor or not.

So with that the astronauts have been instructed to begin their "fluid loading" procedure to drink lots of fluids to replenish their bodies to aide in the readaptation to Earth's gravity. This marks a major event on the road to Discovery being cleared for landing. Mission Control typically does not have the crew begin "fluid loading" unless there is a realistic chance of the shuttle being able to brake from orbit.

0500 GMT (12:00 a.m. EST)

The current weather forecast for the 2:31 a.m. EST landing time at Kennedy Space Center has two concerns -- the chance of a cloud ceiling at 7,000 feet (constraint is 8,000 feet) and crosswinds right at the 12-knot limit. The hope is that cloud deck will become scattered and not constitute a ceiling and the winds would ease a bit more.

0459 GMT (11:59 p.m. EST)

Chief NASA astronaut Charlie Precourt is flying the Shuttle Training Aircraft around Kennedy Space Center to evaluate weather conditions. He is currently checking out the worrisome rainshowers moving from the western part of the state toward KSC. He has reported some thin clouds, but said you could see the stars through them.

0435 GMT (11:35 p.m. EST)

The latest weather briefing continues to indicate that a decision on whether conditions would be safe for Discovery to land at Kennedy Space Center will go down to the wire tonight. The rainshowers, low clouds and crosswinds in Central Florida are being watched closely. A final decision is still 90 minutes away.

0428 GMT (11:28 p.m. EST)

CAPCOM Gus Loria just gave Discovery commander Jim Wetherbee an update on the information for the upcoming deorbit opportunity to Kennedy Space Center, if weather permits.

The two-minute, 54-second deorbit burn would begin at 1:26:06 a.m. EST (0626:06 GMT) to slip Discovery from Earth orbit for the trek to a pin-point touchdown. Upon arriving in the skies over the Cape, Wetherbee would make a left-overhead turn of 264 degrees to align with Runway 15 for touchdown 2,500 feet down the three-mile strip at 2:31 a.m. EST (0731 GMT).

See the ground track Discovery would follow on that opportunity.

0406 GMT (11:06 p.m. EST)

Discovery's General Purpose Computers have successfully transitioned to the OPS-3 entry and landing software.

0355 GMT (10:55 p.m. EST)

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

Also, Discovery is being maneuvered to a new orientation in space to improve the communications link with NASA's orbiting data relay satellites.

0351 GMT (10:51 p.m. EST)

The payload bay doors of space shuttle Discovery have been closed and locked as the stubby-winged ship continues to be transformed from an orbiting platform to a plane for its glide back to Earth in a few hours.

NASA remains hopeful weather conditions will permit a landing at Kennedy Space Center in Florida at 2:31 a.m. EST. The concerns right now are associated with a band of rainshowers moving in the general direction of KSC, bringing with it some low clouds, too. Crosswinds are also a factor.

If the Florida weather doesn't cooperate, then Mission Control will have to decide whether to divert Discovery to the backup landing site at Edwards Air Force Base in California where conditions are ideal today or keep the shuttle in space for another day and try again early Thursday.

0340 GMT (10:40 p.m. EST)

The flash evaporator system aboard Discovery has been checked out and will now be used to cool the shuttle's avionics by using the onboard water supply. This replaces the cooling provided by the radiators on insides of the payload bay doors, which will be swung shut and locked shortly for today's entry and landing.

Also, the astronauts are performing the final payload deactivation chores for entry.

0335 GMT (10:35 p.m. EST)

The latest weather briefing given to Entry Flight Director Wayne Hale showed the growing optimism that conditions at Kennedy Space Center might be acceptable for landing of Discovery at 2:31 a.m. EST.

The forecast is now calling for westerly winds from 260 degrees at 8 peaking to 13 knots. That would produce a crosswind of 12 knots -- the limit for a night shuttle landing.

Meteorologists are also watching a band of rainshowers currently in the Tampa area that is moving toward Kennedy Space Center. It is a matter of where those showers will be at landing time. Rules state there can't be any showers within 30 miles of the runway for landing. The clouds associated with the showers are also of concern because the deck could constitute a ceiling at 7,000 feet. The ceiling must be above 8,000 feet to ensure commander Jim Wetherbee has a good view of the runway during final approach.

A final decision on whether to clear Discovery to return to KSC today will come by 1:05 a.m. EST.

0300 GMT (10:00 p.m. EST)

"Too close to call."

That is the word from the Johnson Space Center at this hour as the entry flight control team monitor weather conditions at Kennedy Space Center's Shuttle Landing Facility where Discovery is scheduled to make a middle-of-the-night touchdown at 2:31 a.m. EST.

Although the weather picture has improved substantially over forecasts issued earlier Tuesday evening, the crosswinds are still a concern. But at this point NASA is not giving up hope on acceptable conditions in Florida.

Meanwhile, the weather at the backup landing site at Edwards Air Force Base in California remains rock solid in the "go" column.

0230 GMT (9:30 p.m. EST)

In a dramatic twist, meteorologists have just given Mission Control an updated weather forecast for Kennedy Space Center that is significantly improved from earlier this evening. A low pressure system affecting the area is moving to the north away from Florida a bit faster than originally predicted.

Officials were seemingly writing off KSC for landing of Discovery due to strong crosswinds and the threat of low clouds. But the clouds are dissipating and the winds have eased, though the crosswinds are still forecast one or two knots over the limit.

At present, the astronauts have opened their deorbit preparations checklist as activities continue to reconfigure Discovery for its descent and landing. The upcoming milestone will be closing of the payload bay doors at 10:46 p.m. EST.

Entry Flight Director Wayne Hale won't have to make a final decision whether to allow Discovery to land in Florida until 1:05 a.m. EST. So the weather still have a couple more hours to improve.

If Discovery is cleared to return to the Florida spaceport, the ship's braking engines would be fired at 1:26 a.m. EST with touchdown on KSC's Runway 15 at 2:31 a.m. EST.

0156 GMT (8:56 p.m. EST)

The astronauts are donning their day-glow orange partial pressure suits in advance of tonight's reentry and landing of space shuttle Discovery. And the heaters on the Leonardo cargo carrier in the shuttle's payload bay are being turned off.

There is nothing new to report on the weather. Kennedy Space Center still looks bleak and Edwards Air Force Base appears near-perfect. At this point, it is highly likely Discovery will be returning to Earth tonight and a diversion to California seems probable.

0112 GMT (8:12 p.m. EST)

To recap, Mission Control and the astronauts are keeping on the timeline to be ready for landing on the second of two landing opportunities at Kennedy Space Center in Florida with touchdown at 2:31 a.m. EST. However, the weather holds very little promise.

And given the iffy weather forecast for Thursday, Entry Flight Director Wayne Hale likely will bring the shuttle home tonight at the backup landing site at Edwards Air Force Base in California where condition are ideal for Discovery's high-speed, nighttime touchdown. The two available landing opportunities are 4:02 and 5:38 a.m. EST.

0108 GMT (8:08 p.m. EST)

The option of keeping Discovery aloft another day hinges on the weather forecast for both landing sites in the wee hours of Thursday morning.

Forecasters say the clouds should clear in Florida but the crosswinds would still be strong. The weather all depends on a low pressure system in the region and how quickly it moves over the next 24 hours.

At Edwards, the winds are expected to pick up. And although the winds are predicted right down the runway, the concern is if they shifted direction it could present a constraint for landing at the backup site.

So NASA could be in a situation where both landing sites would be "no go" on Thursday.

0059 GMT (7:59 p.m. EST)

Discovery skipper Jim Wetherbee was just informed by Mission Control that the crew should press ahead with activities this evening toward a possible landing at Kennedy Space Center in hopes of a break in the bad weather in Florida. The deorbit preparation timeline will be started by the astronauts at 9:26 p.m. and the payload bay doors should be closed at 10:46 p.m. EST.

Should the weather not improve in Florida, NASA could either divert Discovery to Edwards Air Force Base in California where conditions are acceptable or keep the shuttle aloft for another 24 hours.

The main concern at KSC is the strong crosswind at the three-mile landing strip. Current observations show crosswinds are gusting anywhere from 14 to 19 knots. The limit is 12 knots for a nighttime shuttle landing. There is also worries about a cloud ceiling at 6,000 feet. The ceiling must be above 8,000 feet.

Edwards has near-perfect weather for the shuttle homecoming at 4:02 a.m. EST.

0040 GMT (7:40 p.m. EST)

Here is a detailed look at the weather forecast for Kennedy Space Center and Edwards Air Force Base over the next two days.

Tonight KSC is expecting scattered clouds at 4,000 and 6,000 feet, visibility of 7 miles and southwesterly winds from 240 degrees at 12 peaking to 18 knots, with a crosswind component of 15 knots. The constraints to landing are crosswinds above the 12-knot allowable limit and a chance the cloud deck at 6,000 feet would become broken and constitute a ceiling.

The Edwards forecast is favorable with just a few clouds at 10,000 and broken clouds at 20,000 feet, 7 miles visibility and southwesterly winds from 230 degrees 6 peaking to 10 knots.

For early Thursday morning, should Discovery remain aloft another day, the weather is somewhat improved for KSC and still acceptable at Edwards.

The KSC forecast calls for scattered clouds at 4,000 feet, 7 miles visibility and westerly winds from 280 degrees at 12 peaking to 18 knots.

At Edwards meteorologists predict a few clouds at 10,000 feet, scattered clouds at 25,000 feet, 7 miles visibility and southwesterly winds from 230 degrees at 10 peaking to 15 knots.

0028 GMT (7:28 p.m. EST)

Mission Control just radioed the Discovery crew and informed commander Jim Wetherbee that officials will be reviewing a briefing on the entire weather picture over the next 20 minutes. So some further details on plans for Discovery's landing should be known by the top of the hour.

TUESDAY, MARCH 20, 2001
2350 GMT (6:50 p.m. EST)

WAVE OFF! As the entry flight control team takes over in Mission Control to oversee tonight's scheduled homecoming of space shuttle Discovery, we begin our live status center coverage of landing with news that NASA has waved off the first opportunity for touchdown at Kennedy Space Center tonight.

The weather forecast calls for low clouds and stiff crosswinds at the Florida spaceport, causing NASA to cancel plans to aim for a 12:56 a.m. EST landing.

So Discovery and the seven astronauts will take an extra orbit of Earth and target the second and final opportunity of the day for landing at Kennedy Space Center should the weather somehow improve. Meteorologists aren't hopeful, however. That opportunity would begin with a deorbit burn to brake from space at 1:26 a.m. (0626 GMT) and landing at 2:31 a.m. EST (0731 GMT) on Runway 15.

Meanwhile, NASA is keeping open the option of sending Discovery on a detour to the alternate landing site at Edwards Air Force Base in California. There will be two opportunities for a landing there: 4:02 and 5:38 a.m. EST. Weather conditions in the Mojave Desert are acceptable both Wednesday and Thursday.

The forecast for Kennedy Space Center on Thursday, should officials decide to keep Discovery in space for another day, has been upgraded by meteorologists and is now favorable.

So there are several options available Entry Flight Director Wayne Hale tonight. Watch this page for the very latest!

2142 GMT (4:42 p.m. EST)

The astronauts aboard space shuttle Discovery have been awakened for Flight Day 14 -- a day that is supposed to see the crew to return to Earth. But lousy weather conditions at the Kennedy Space Center landing site could keep the shuttle aloft another day or force Discovery to be diverted to Edwards Air Force Base in California tonight.

Shuttle commander Jim Wetherbee, pilot Jim Kelly, mission specialists Andy Thomas and Paul Richards and Expedition One crewmembers Bill Shepherd, Yuri Gidzenko and Sergei Krikalev will have breakfast shortly, then begin the final chores to pack up the Discovery's crew module for entry and landing.

NASA continues to focus on two available opportunities to bring Discovery back to Kennedy Space Center -- the preferred landing site -- in the wee hours of Wednesday. However, forecasters are calling for low clouds and a stiff crosswind at KSC that would violate the strict landing weather rules.

The first chance at landing would begin with an engine firing to brake Discovery from orbit at 11:50 p.m. EST (0450 GMT). That would lead to a touchdown at 12:56 a.m. (0556 GMT) on KSC's Runway 15. Should the weather be unacceptable for that landing opportunity, NASA would keep the shuttle in space for an additional orbit and look to the second and final shot of the day to land in Florida. That would come on orbit 201 with a deorbit burn at 1:26 a.m. (0626 GMT) and landing at 2:31 a.m. EST (0731 GMT).

If the weather prevents a homecoming in Florida, Entry Flight Director Wayne Hale will then review the forecast for Thursday at both KSC and the backup site at Edwards Air Force Base in California. Should the forecast show a realistic chance of better conditions in Florida on Thursday morning and a safe bet of Edwards being acceptable, Hale could elect to keep Discovery in space for another 24 hours.

But if the weather for Thursday is questionable, Discovery could be sent to Edwards on Wednesday morning. Two landing opportunities exist on the two orbits following the KSC shots. The first -- on orbit 202 -- begins with a deorbit burn at 2:57 a.m. EST (0757 GMT) and landing on Runway 22 at 4:02 a.m. EST (0902 GMT). The final opportunity of the day starts with the deorbit burn at 4:33 a.m. EST (0933 GMT) and touchdown at 5:38 a.m. EST (1038 GMT).

At present, Edwards is forecast "go" for both Wednesday and Thursday.

The bottom line is NASA wants to land in Florida -- it saves $1 million and a week's worth of time ferrying the shuttle across the country if Discovery would touch down at Edwards. However, NASA doesn't want to get into a position where waves off KSC tonight, then foregoes acceptable weather in California on Wednesday and keeps Discovery in orbit on the hope of improved conditions in Florida on Thursday only to face bad weather at both locations Thursday.

Discovery has enough consumables to remain in space through Friday if necessary.

0630 GMT (1:30 a.m. EST)

The Discovery astronauts tested the shuttle's re-entry systems late Monday and packed up for landing early Wednesday to bring the international space station's first crew back to Earth after 141 days in the weightlessness of space. Read our full landing preview story.

We also have a detailed timeline of the reentry activities.

0506 GMT (12:06 a.m. EST)

The Spaceflight Meteorology Group has offered a bleak forecast for Discovery's chances of a Florida homecoming early Wednesday. Low cloud, rain and high crosswinds are likey to rule out the planned 0556 GMT (12:56 a.m. EST) touchdown at the Kennedy Space Center, NASA mission commentator Rob Navias said.

The poor forecast has prompted entry flight director Wayne Hale to call up landing support at the back-up landing strip at Edwards Air Force Base in California. Complicating matters is the forecast for a 24 hour wave off which offers more promising weather in Florida, but the threat of crosswinds at the California site.

0406 GMT (11:06 p.m. EST, Mon.)

Entry flight director Wayne Hale is receiving a weather briefing from the Spaceflight Meteorlogy Group at the Johnson Space Center.

0243 GMT (9:43 p.m. EST, Mon.)

Current weather forecasts Discovery's planned homecoming in Florida call for low clouds, rain and high crosswinds -- all in violation of NASA's strict rules for shuttle landings.

"The weather forecast is not looking particularly encouraging," said mission commentator Rob Navias.

Entry flight director Wayne Hale will decide whether to place on standby the shuttle's back-up landing strip at Edwards Air Force Base, California, after recieving a weather update in about an hour and a half.

0220 GMT (9:20 p.m. EST, Mon.)

The flight control system check out is going smoothly. Auxiliary Power Unit (APU) No.1 ran for about five and a half minutes as the crew flexed the orbiter's aerosurfaces as part of the routine pre-landing checks. Next up: a test firing of Discovery's 44 steering jets.

0156 GMT (8:56 p.m. EST, Mon.)

Mission control has given the crew of Discovery a "go" to perform the flight control system (FCS) checkout in preparation for Wednesday morning's landing opportunities.

0145 GMT (8:45 p.m. EST, Mon.)

Discovery commander Jim Wetherbee reports the shuttle crew has the station in sight. The two craft are about 100 miles apart according to estimates by mission control.

0122 GMT (8:22 p.m. EST, Mon.)

The Expedition Two crew is scheduled to wake at about 0600 GMT 1 a.m. EST.

Read our earlier status center coverage.