BY WILLIAM HARWOOD

Follow the four-month mission of first resident crew of the international space station as well as the STS-98 flight of space shuttle Atlantis to deliver the U.S. laboratory Destiny. Reload this page for the very latest.

THURSDAY, FEBRUARY 22, 2001

The three-man Expedition One crew living aboard the international space station will depart the orbiting outpost for a short time Saturday to move their Soyuz capsule to a different docking port. The Soyuz needs to be relocated to make way for an unmanned Progress supply ship scheduled for launch Monday.

With Soyuz Pilot Yuri Gidzenko at the controls, and joined by Commander Bill Shepherd and Flight Engineer Sergei Krikalev, the Soyuz will be undocked from the station at 5:08 a.m. EST (1008 GMT).

Gidzenko will back the Soyuz away from the aft docking port of the Zvezda Service Module and fly around the station to redock the Soyuz to the nadir, or earthward-facing, docking port of the Zarya Control Module.

The relocation maneuver should take about 30 minutes to complete. Television from the Soyuz is expected for a few minutes during the redocking over Russian ground stations.

The repositioning of the Soyuz will set the stage for the docking of the Russian Progress resupply vehicle to the Zvezda's aft docking port next Wednesday.

Watch this page for live updates on the Soyuz move on Saturday!

TUESDAY, FEBRUARY 20, 2001

Running two days late, the shuttle Atlantis dropped out of a cloudy Mojave Desert sky and glided to a smooth landing today at Edwards Air Force Base to wrap up an extended space station assembly flight. Read our full landing story.

2200 GMT (5:00 p.m. EST)

The three-man Expedition One crew aboard the international space station has been advised that Atlantis returned to Earth safely today. The station residents are just a couple of weeks away from coming home, too. They will ride Discovery back to Earth at the conclusion of the next shuttle mission in March. Due for blastoff March 8, Discovery will transport the Expedition Two crew to the station to relieve the vanguard astronauts.

Meanwhile, the Atlantis astronauts are headed back to the quarters for the night. They plan to return home to Houston tomorrow. The shuttle itself will be safed and prepared for the cross-country ferry flight atop a modified Boeing 747 jet over the next several days. Watch this page for updates on the trek home for Atlantis.

2153 GMT (4:53 p.m. EST)

Atlantis' astronauts are now taking the customary walk around the shuttle on runway, kicking the tires of sort after the 12-day, 21-hour, 5.3-million voyage.

2127 GMT (4:27 p.m. EST)

All five Atlantis astronauts are now reported off the shuttle and inside the Crew Transport Vehicle. They will be taken back to the crew quarters at Edwards today after their traditional walkaround of Atlantis on the runway.

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

The landing convoy has arrived at Atlantis on the runway after safety personnel verified there were no toxic vapors or problems coming from the shuttle.

2048 GMT (3:48 p.m. EST)

Post-landing chores continue for the astronauts to configure the shuttle after their homecoming. The main engine nozzles have been moved to the "rain drain" position, the shuttle's onboard computers have transitioned to the post-landing software package and Atlantis' three Auxiliary Power Units are being shut down. Also, Mission Control has told the crew they can now remove their launch and entry space suits if so desired.

2047 GMT (3:47 p.m. EST)

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

Main Gear Touchdown
3:33:05 p.m. EST
MET: 12 days, 21 hours, 20 minutes, 03 seconds

Nose Gear Touchdown
3:33:17 p.m. EST
MET: 12 days, 21 hours, 20 minutes, 15 seconds

Wheels Stop
3:34:02 p.m. EST
MET: 12 days, 21 hours, 21 minutes, 00 seconds

2044 GMT (3:44 p.m. EST)

Atlantis' three main engine nozzles are now being gimbaled to the so-called "rain drain" position. On the runway, workers have arrived with instruments to "sniff" the shuttle's exterior to check for any hazardous vapors.

2039 GMT (3:39 p.m. EST)

The astronauts are going through standard post-landing safing of Atlantis following a smooth touchdown today. The side hatch pyrotechnics have been safed and the external tank umbilical doors on the shuttle's belly have been opened.

2034 GMT (3:34 p.m. EST)

WHEELS STOP. Atlantis has rolled to a stop, bringing to an end its 23rd flight and the first human spaceflight of 2001.

2033 GMT (3:33 p.m. EST)

TOUCHDOWN! Main gear touchdown. Drag chute deployed. Nose gear touchdown. Space shuttle Atlantis rolls out on Runway 22 at the Edwards Air Force Base to complete a successful 5.3-million mile mission that spanned 202 complete orbits and delivered the U.S. Destiny laboratory to the international space station.

2032 GMT (3:32 p.m. EST)

Landing gear down and locked. Standing by for touchdown on Edwards' Runway 22 in the Mojave Desert of Southern California.

2031 GMT (3:31 p.m. EST)

Field in sight. Commander Cockrell can see the concrete runway destination as he pilots Atlantis.

2030 GMT (3:30 p.m. EST)

Atlantis is in the Heading Alignment Cylinder, an imaginary circle to align with Runway 22. Ken Cockrell will make a 210-degree right-overhead turn.

2028 GMT (3:28 p.m. EST)

Atlantis is at 55,000 feet some 32 miles to touchdown.

2027 GMT (3:27 p.m. EST)

Atlantis is 87,000 feet above Southern California flying at 1,700 miles per hour, less than 80 miles to touchdown.

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

Atlantis has made landfall over Southern California near Santa Monica. The third bank has started -- this one back to the left. And air data probes have been deployed from the shuttle's nose to feed air speed and altitude information to the computers for navigation.

2024 GMT (3:24 p.m. EST)

Nine minutes to touchdown. Atlantis is approaching the Southern California coast. The shuttle will fly directly above Los Angeles, its sonic booms should be heard in a couple minutes, and then above Palmdale where Boeing's Shuttle Assembly Plant is located. That facility is where all the space shuttles were built.

2023 GMT (3:23 p.m. EST)

Ten minutes to touchdown. Atlantis is 260 miles from the runway, speeding along at 4,700 mph at an altitude of 140,000 feet.

2022 GMT (3:22 p.m. EST)

The TACAN navigation units aboard Atlantis are now receiving data from beacons located at the ground.

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

Atlantis remains on the proper track for landing in 12 minutes at Edwards Air Force Base. Touchdown predicted to be 2,800 feet down the runway at 195 knots.

2019 GMT (3:19 p.m. EST)

The shuttle is reversing its banking. This roll is to the right and is the second of four turns during entry designed to reduce speed.

2018 GMT (3:18 p.m. EST)

Inside the final 15 minutes of flight. Atlantis is 828 miles from the runway, speeding along at 10,300 mph at an altitude of 190,000 feet.

2015 GMT (3:15 p.m. EST)

Now 18 minutes touchdown. Atlantis is currently at an altitude of 41 miles, distance to the runway 1,400 miles, with a velocity of 13,600 mph and descending at a rate of 110 feet per second.

2012 GMT (3:12 p.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.

2010 GMT (3:10 p.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 roll to the left. These turns basically remove the energy Atlantis built up during launch. Mission Control is out of 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.

Altitude 244,000 feet, velocity 16,100 mph, distance to the runway now 2,700 miles as Atlantis crosses the equator.

2006 GMT (3:06 p.m. EST)

Now 27 minutes to landing. Distance from Edwards is 3,800 miles. Altitude currently 274,000 feet over the Central Pacific Ocean approaching the equator.

2002 GMT (3:02 p.m. EST)

ENTRY INTERFACE. The protective tiles on the belly of Atlantis 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 2033 GMT (3:33 p.m. EST) on Runway 22 at Edwards Air Force Base in California.

1958 GMT (2:58 p.m. EST)

Atlantis' onboard computers now switching to the OPS-304 program, which governs entry phase of the mission. Now 35 minutes until landing. Atlantis currently above the South Pacific Ocean, northeast of New Zealand, continuing to fall closer and closer to the atmosphere.

1950 GMT (2:50 p.m. EST)

All three Auxiliary Power Units are running to supply pressure to the shuttle's hydraulic systems, which in turn move Atlantis' 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.

1948 GMT (2:48 p.m. EST)

Atlantis is now cruising south of Australia. Time until touchdown is 45 minutes.

1940 GMT (2:40 p.m. EST)

Atlantis continues its free fall towards the Earth's upper atmosphere. The shuttle is now in the proper orientation for reentry.

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

Onboard guidance is now maneuvering Atlantis 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. Atlantis will begin interacting with the upper fringes of the atmosphere above the South Pacific.

The shuttle's track home is taking the craft above the Indian Ocean, south of Australia, over the South Pacific and then on a northeastward track toward the United States. The shuttle will make landfall over Los Angeles in Southern California with the loud double sonic booms to be heard at about 12:27 p.m. local time. Atlantis' track will continue towards Edwards Air Force Base in the Mojave Desert. Once in the vicinity of the runway, Commander Cockrell will perform a 210-degree right-overhead turn to align with Runway 22 -- the northeast to southwest runway.

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

DEORBIT BURN COMPLETE. Atlantis has successfully completed the deorbit burn, committing the shuttle for its journey back to Earth. The shuttle should hit the top of the atmosphere in about a half-hour and touchdown at Edwards Air Force Base in California is set for 2033 GMT (3:33 p.m. EST).

The landing time weather forecast at Edwards is calling for a few scattered clouds, good visibility and a direct headwind of 12 peaking 20 knots from the southwest at 240 degrees.

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

DEORBIT BURN IGNITION. Flying upside down and backwards over the Indian Ocean off the east coast of Africa, space shuttle Atlantis has begun the deorbit burn for return to Earth. The firing of the two OMS engines on the tail of the shuttle will last two minutes, 43 seconds, slowing the craft by 319 feet per second, just enough to slip from orbit. The retro-burn will send Atlantis toward a touchdown at 3:33 p.m. EST on Runway 22 at Edwards Air Force Base in California.

1923 GMT (2:23 p.m. EST)

Now four minutes from the deorbit burn. Pilot Mark Polansky has activated Auxiliary Power Unit No. 1 in advance of the burn. 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 upon touchdown. 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.

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

Atlantis has started 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 19 minutes away, will slow Atlantis below orbital velocity, allowing the craft to slip from space and begin the hour-long glide to a pin-point touchdown at 3:33 p.m. EST (2033 GMT) at California's Edwards Air Force Base.

1903 GMT (2:03 p.m. EST)

Now 90 minutes away from Atlantis' scheduled landing in the Mojave Desert of Southern California.

Today's touchdown of Atlantis at Edwards Air Force Base in California will mark only the second shuttle landing there over the past five years. There was 23 straight landings have occurred at Kennedy Space Center in Florida before the string was broken last October when Discovery landed at Edwards. The shuttle mission since then -- STS-97 -- did return to Kennedy. NASA prefers Florida landings because its saves $1 million and a week's worth of processing time to avoid ferrying the shuttle across the country to the KSC launch site. But weather spoiled a KSC touchdown today.

In the 100 previous shuttle landings, 53 have occurred at KSC, 46 at Edwards and one at White Sands in New Mexico.

1859 GMT (1:59 p.m. EST)

GO FOR THE DEORBIT BURN! Entry Flight Director Leroy Cain has given final approval for space shuttle Atlantis' landing today at Edwards Air Force Base in California. So after two extra days in orbit, Atlantis is finally set to return to Earth to complete the first space shuttle mission of 2001.

The upcoming retrograde burn using the twin orbital maneuvering system engines on the tail of Atlantis to slow the shuttle's velocity by over 319 feet per second, just enough to slip the craft out of orbit and begin the plunge back into the atmosphere. Engine ignition is scheduled for 2:27:20 p.m. EST (1927:20 GMT) for the two-minute, 43-second firing.

Atlantis is headed to a landing at 3:33 p.m. EST (2033 GMT) on Runway 22 at Edwards. The landing will conclude the 12-day, 21-hour, 20-minute STS-98 mission that delivered the U.S. Destiny laboratory to the international space station.

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

1848 GMT (1:48 p.m. EST)

The landing convoy made up of several vehicles used to safe the shuttle on the runway are rolling to their position for Atlantis' return. Entry Flight Director Leroy Cain is receiving another weather update before making his final decision whether to clear Atlantis for this landing opportunity.

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

Weather reconnaissance pilot Brian Duffy report the conditions around Edwards Air Force Base are pretty stable and not dynamic today. The lower-level clouds around the area don't have any moisture in them. So weather appears like it will cooperate so Atlantis can make its journey back to Earth at last. A final "go/no go" decision on this landing opportunity is scheduled around the top of this hour.

1829 GMT (1:29 p.m. EST)

The Atlantis crew has been given a "go" to perform a steering check of the Orbiter Maneuvering System thrust vector control and begin Auxiliary Power Unit prestart, which positions switches in the cockpit in the ready-to-start configuration.

1816 GMT (1:16 p.m. EST)

CAPCOM Scott Altman just gave Atlantis commander Ken Cockrell an update on the information for the upcoming deorbit opportunity to Edwards Air Force Base, California. The 2-minute, 43-second deorbit burn would begin at 2:27:20 p.m. EST (1927:20 GMT). Upon arriving in the skies over the Edwards, Cockrell would make a right-overhead turn of 210 degrees to align with Runway 22 for touchdown 2,700 feet down the runway at 3:33 p.m. EST (2033 GMT).

See the ground track Atlantis would follow on that opportunity.

1809 GMT (1:09 p.m. EST)

Astronaut Brian Duffy is making an approach to Runway 22 at Edwards to evaluate the weather conditions. Duffy was the commander of the last shuttle mission to land at Edwards -- STS-92 last October. He will soon fly down to the Palmdale area to look at some clouds that could be building there. Palmdale is the site of the Boeing assembly plant where the space shuttles were built.

1738 GMT (12:38 p.m. EST)

The first live television pictures from Edwards is now being shown on NASA TV. It appears to be a magnificent day with mostly clear skies. NASA astronaut Brian Duffy has been flying a T-38 jet around the area earlier this morning and didn't report any concerns. He will switch to a modified Gulfstream Shuttle Training Aircraft -- like they one Charlie Precourt has been flying in Florida -- to evaluate the weather at Edwards' concrete runway 22 and 04.

1724 GMT (12:24 p.m. EST)

KSC WAVED OFF! Troublesome clouds over Kennedy Space Center has forced NASA to cancel plans to land space shuttle Atlantis at the Florida spaceport today. It is the third straight day bad weather has prevented Atlantis from landing at the site where it launched on February 7.

Mission Control has opted to send the shuttle to the backup landing site at Edwards Air Force Base in California for a scheduled 2033 GMT (3:33 p.m. EST) touchdown. Weather conditions in the Mojave Desert are reported as "great" today.

1721 GMT (12:21 p.m. EST)

The Atlantis crew just inquired if they could begin working some steps to prepare for the proposed deorbit burn for the upcoming KSC landing opportunity. Mission Control responded by telling the astronauts to hold off and that more words would be coming.

1718 GMT (12:18 p.m. EST)

Entry Flight Director Leroy Cain is receiving a weather briefing on the latest Kennedy Space Center and Edwards Air Force Base forecasts.

1710 GMT (12:10 p.m. EST)

The skies over Kennedy Space Center are really cloudy now. Precourt continues to punch through the clouds in the Shuttle Training Aircraft as he flies weather reconnaissance and makes approaches to both ends of the runway at Kennedy Space Center. In his recent approaches following the path Atlantis would take, he broke into the clouds at 7,500 feet and didn't emerge unti just 2,500 feet above the ground, which would not be an acceptable situation for a shuttle landing.

1702 GMT (12:02 p.m. EST)

Weather pilot Charlie Precourt says the approach to Kennedy Space Center's Runway 15 is "no go" right now. If the line of clouds moves to the west, it would be OK. But it hasn't done that yet. He also says crosswinds are no problem today.

1651 GMT (11:51 a.m. EST)

CAPCOM Scott Altman just told the Atlantis astronauts that clouds are unacceptable at Kennedy Space Center. Forecasters had predicted the clouds would move out of the area, but that is not taking place. Although Mission Control hasn't given up completely on KSC yet, the situation does not look favorable for Atlantis returning to Florida today.

Meanwhile, at the backup landing site at Edwards Air Force Base in California is weather is looking good so far. The first shot at landing there today would be 3:33 p.m. EST (2033 GMT). Astronaut Brian Duffy is flying weather reconnaissance over the Mojave Desert military base today.

The weather is forecast acceptable at the other backup landing site -- White Sands in New Mexico. Astronaut John Young is piloting the weather aircraft there.

The astronauts have been told to begin their "fluid loading" procedure to drink lots of fluids to replenish their bodies to aide in the readaptation to Earth's gravity, but to do at "their own pace" given the likelihood of waving off the upcoming KSC opportunity.

1645 GMT (11:45 a.m. EST)

The astronaut weather liason in Mission Control -- Dom Gorie -- just told Charlie Precourt the clouds are beginning to fill in, getting worse than they expected. Forecasters are still expecting them to dissipate, but it isn't happening fast enough. Precourt has asked if this line of clouds is moving to the west at all. Gorie says they're discussing that.

1639 GMT (11:39 a.m. EST)

Precourt says he just flew through some of the biggest "clumps" of clouds and found "very little" or no moisture in those.

1635 GMT (11:35 a.m. EST)

Precourt says the cloud bases are at 3,700 feet and tops at 8,000 feet. He reports moisture in some of the clouds.

1630 GMT (11:30 a.m. EST)

Just like the past two days, chief NASA astronaut Charlie Precourt is flying the Shuttle Training Aircraft around Kennedy Space Center to evaluate weather conditions. In his first report of the day, he says the clouds over KSC are mostly scattered with a large clear area visible to the southeast, but there are numerous "clumps" of clouds four to 10 miles across that are thick enough to be considered broken.

1620 GMT (11:20 a.m. EST)

CAPCOM Scott Altman just gave Atlantis commander Ken Cockrell an update on the information for the upcoming deorbit opportunity. The 2-minute, 44-second deorbit burn would begin at 12:56:22 p.m. EST. Upon arriving in the skies over KSC, Cockrell would make a left-overhead turn of 261 degrees to align with Runway 15 for touchdown about 2,400 feet down the runway at 2:02 p.m. EST.

1610 GMT (11:10 a.m. EST)

Per the timeline, the astronauts should be donning their day-glow orange launch and entry spacesuits shortly as preparations go on for the possible landing at Kennedy Space Center at 2:02 p.m. EST today.

Mission Control has another hour-and-a-half before needing to make a final decision on the landing opportunity so Atlantis can perform the deorbit burn to begin the descent home. Clouds are still the main issue in Florida.

1542 GMT (10:42 a.m. EST)

Shuttle Atlantis has begun its 200th orbit of Earth since launching on February 7. Meanwhile, flight controllers continue to watch a steady stream of clouds moving over Kennedy Space Center in a southeast to northwest direction. Meteorologists are hoping the whole band shifts more to the west, allowing for KSC to clear out.

1530 GMT (10:30 a.m. EST)

Atlantis' onboard computers are now transitioning 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.

1521 GMT (10:21 a.m. EST)

The Atlantis crew has closed and locked the payload bay doors in hopes of returning to Kennedy Space Center today at 2:02 p.m. EST. However, a stream of clouds moving onshore from the Atlantic Ocean is worrying Mission Control. The concern is those clouds could constitute a ceiling and obscure commander Cockrell's view of the runway during final approach.

NASA's game plan at present -- should the weather not cooperate at KSC -- would be to target Edwards Air Force Base for opportunities at 3:33 p.m. and 5:09 p.m. EST. Low clouds are also a concern there today. If Edwards is "no go" today, the last-ditch alternative is White Sands with a 5:11 p.m. EST touchdown where the weather is not expected to be a problem.

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

The flash evaporator system aboard Atlantis 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.

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

So Atlantis and its five astronaut crew makes another orbit of Earth while waiting for better weather conditions at the Kennedy Space Center landing site. Meteorologists are somewhat hopeful the clouds will move out of the area later this morning.

If the clouds end up not being a problem, Atlantis would perform a nearly three-minute long deorbit burn starting at 12:56:22 p.m. EST (1756:22 GMT) to brake from orbit and begin an hour-long dive back Florida. Touchdown on Runway 15 at KSC's Shuttle Landing Facility would occur at 2:02 p.m. EST (1902 GMT). See the ground track Atlantis would follow on that opportunity.

If KSC remains "no go" due to weather, then Mission Control will have no choice but to look to the backup landing sites at Edwards Air Force Base in California and White Sands in New Mexico. The landing times for those opportunities are:

Edwards AFB: 3:33 p.m. EST
White Sands: 3:35 p.m. EST

Edwards AFB: 5:09 p.m. EST
White Sands: 5:11 p.m. EST

And for those of you scoring at home, NASA has effectively passed up the first White Sands opportunity today that occurs on the same orbit as the 2:02 p.m. EST KSC landing.

1402 GMT (9:02 a.m. EST)

ANOTHER ORBIT! Uncertainty over clouds approaching Kennedy Space Center has forced Mission Control to forego the first landing opportunity of the day for space shuttle Atlantis. Officials will keep watch on the clouds, which could pose a problem for Commander Ken Cockrell seeing the runway as he pilots the powerless glider to the swamp-surrounded landing strip.

The decision was also made because of the need to conserve onboard water for landing attempts later in the day, including opportunities in California and New Mexico. Mission Control had told the crew to hold off closing Atlantis' payload bay doors to save water needed for cooling the shuttle's electronics.

"We know once we close the doors, we are committed to landing in the next three (orbits)," CAPCOM Scott Altman radioed the astronauts.

Those three orbits now being targeted will be deorbiting on 201, 202 and 203. The first would be to Kennedy Space Center and a touchdown at 2:02 p.m. EST. The later tries would send Atlantis to the backup landing sites if the KSC weather does not improve.

NASA wants to get Atlantis back on Earth somewhere today.

It is also worth noting that White Sands does not have a live television uplink facility. So if Atlantis lands there today, live TV won't be expected.

1250 GMT (7:50 a.m. EST)

The Atlantis astronauts are gearing up for another attempt to bring the 102nd shuttle mission to an end today after back-to-back landing delays Sunday and Monday.

The crew transitioned to the deorbit timeline at 7:25 a.m. EST in preparation for a landing at the Kennedy Space Center at 12:27 p.m.

That's the first of today's seven possible landing opportunities over four successive orbits: Two at the Kennedy Space Center, two at Edwards Air Force Base, Calif., and three at White Sands, N.M.

But the crew will only be able to use three of those opportunities. Once the shuttle's cargo bay doors are closed, Atlantis' electronics are cooled by water and there's only enough water to support three landing attempts today.

"Once we close the payload bay doors, we are committed to land within three revs (orbits) due to our consumables," astronaut Scott Altman radioed the crew from Houston. "So right now, we're looking very hard at what the best combination of three opportunities is to select for you.

"We do have a 'go' forecast for KSC at this time, just want to confirm there's no risk of clouds moving into the picture that we're not expecting and we'll have more words for you as we get closer."

To make the first Florida landing opportunity, the crew would close the shuttle's cargo bay doors around 9:40 a.m. But they may be told to hold off on the procedure depending on the weather at Kennedy and Edwards.

"We may hold off a little bit on payload bay door closure to make sure we have the optimal set of landing opportunities for you," Altman told the crew.

The forecast for the Kennedy Space Center calls for scattered clouds at 4,500 feet with winds from 110 degrees at nine knots, peaking to 16. For the second opportunity one orbit later, the winds will shift to 130 degrees but the crosswind component in both cases is below NASA's 15-knot limit.

There is some concern, however, that clouds could blow on shore later in the day. Astronaut Charles Precourt is flying a T-38 jet at Kennedy this morning to monitor potential cloud development.

At Edwards, the forecast calls for scattered clouds at 5,000 feet and two broken decks at 10,000 and 20,000 feet with winds from 210 degrees at eight knots and gusts to 14. That's no problem. There is a chance, however, of a broken deck of clouds at 5,000 feet, which would violate NASA's safety rules.

At White Sands, forecasters expect just a few clouds at 10,000 feet, a broken deck at 25,000 feet and winds from 240 degrees at seven knots with gusts to 14.

Only one shuttle mission has ever ended at White Sands - STS-3 in March 1982 - and it does not appear likely the New Mexico landing site will be a player today.

Of the three possible White Sands landing opportunities, only the third - at 5:11 p.m. EST - likely would be considered in a mix of three overall opportunities. And by that time of the day, the winds at White Sands are predicted to go out of limits.

See the NASA television schedule (rev. N) for a complete list of deorbit and landing times. And check our updated STS-98 deorbit timeline for a detailed look at the two Kennedy and Edwards opportunities.

Read our earlier status center coverage.