Keeping tabs on threatening weather, the Endeavour astronauts packed up Saturday, powered down the ship's robot arm and tested the shuttle's re-entry systems in preparation for landing Sunday night at the Kennedy Space Center.

Commander George Zamka and his crewmates have two landing opportunities in Florida Sunday and two at Edwards Air Force Base, Calif. Flight controllers Saturday deleted a previously planned orbit adjust rocket firing, resulting in slightly revised deorbit and landing times (in EST and mission elapsed time):

DATE/TIME.....DD...HH...MM...SS...EVENT

02/21
09:14:52 PM...13...17...00...45...Deorbit ignition (orbit 217)
10:20:37 PM...13...18...06...30...Landing at Kennedy Space Center
10:50:52 PM...13...18...36...45...Deorbit ignition (orbit 218)
11:55:50 PM...13...19...41...43...Landing at Kennedy Space Center

02/22
12:20:31 AM...13...20...06...24...Deorbit ignition (orbit 219)
01:25:41 AM...13...21...11...34...Landing at Edwards AFB
01:56:41 AM...13...21...42...34...Deorbit ignition (orbit 220)
03:00:56 AM...13...22...46...49...Landing at Edwards AFB

But the Spaceflight Meteorology Group at the Johnson Space Center is predicting possible rain showers near the Kennedy Space Center with rain and low clouds expected at Edwards in California's Mojave Desert. Even worse conditions are expected in Florida on Monday but Edwards is expected to be "go."

NASA has a third shuttle landing site near White Sands, N.M., but it is considered a last-resort option because less support equipment is staged there and it would take longer to get a shuttle back to Florida. Given the current forecast, NASA is unlikely to consider a diversion to White Sands.

"The forecast we have right now, we have at least an even chance, if not a little better than that, probably 60-40 in my estimation for getting into KSC on the first opportunityåÊtomorrow night," LeRoy Cain, chairman of NASA's Mission Management Team, said at a news briefing.

"That's my personal guess, which means absolutely nothing, but since you asked, I'll give it to you. The good news is, we have a lot of options, a lot of capability in terms of our end-of-mission days and deorbit opportunities to the various sites. We're hopeful (Kennedy is) where we'll get to."

Endeavour has enough on-board supplies to remain in orbit until Tuesday at the latest. But NASA typically reserves the final landing opportunity to protect against payload bay door problems or other technical issues. Cain said NASA's current focus is to get Endeavour down, on one coast or the other, by Monday. Entry Flight Director Norm Knight is expected to brief reporters on his landing strategy at 1:30 a.m. Sunday.

Aboard Endeavour, meanwhile, Zamka, pilot Terry Virts and flight engineer Stephen Robinson worked through a standard day-before-entry flight control system checkout, firing up one of the ship's hydraulic power units and exercising the shuttle's elevons, rudder and other systems before test firing the ship's maneuvering jets.

Just before the APU was shut down, a piece of debris of some sort could be seen floating away from the shuttle, possibly jarred loose by the vibrations of the hydraulic system. The object passed very close to a camera and was too out of focus to identify.

Additional coverage for subscribers:
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VIDEO: CREW HOME MOVIES: FLIGHT DAY 1 PLAY
VIDEO: CREW HOME MOVIES: FLIGHT DAY 3 PLAY
VIDEO: CREW HOME MOVIES: FLIGHT DAY 4 PLAY
VIDEO: CREW HOME MOVIES: FLIGHT DAY 5 PLAY
VIDEO: CREW HOME MOVIES: FLIGHT DAY 6 PLAY
VIDEO: CREW HOME MOVIES: FLIGHT DAY 7 PLAY
VIDEO: CREW HOME MOVIES: FLIGHT DAY 8 PLAY
VIDEO: CREW HOME MOVIES: FLIGHT DAY 9 PLAY
VIDEO: CREW HOME MOVIES: FLIGHT DAY 10 PLAY
VIDEO: CREW HOME MOVIES: FLIGHT DAY 11 PLAY
VIDEO: CREW HOME MOVIES: FLIGHT DAY 12 PLAY
VIDEO: CREW HOME MOVIES: FLIGHT DAY 13 PLAY
VIDEO: CREW HOME MOVIES: FLIGHT DAY 14 PLAY

VIDEO: FLIGHT DAY 13 HIGHLIGHTS MOVIE PLAY
VIDEO: STUNNING TIME-LAPSE OF STATION FLYAROUND PLAY
VIDEO: SATURDAY MORNING'S MISSION STATUS BRIEFING PLAY
VIDEO: VIEWS OF ENDEAVOUR DURING THE FLYAROUND PLAY
VIDEO: VIEWS OF THE SPACE STATION DURING FLYAROUND PLAY
VIDEO: ENDEAVOUR UNDOCKS FROM THE SPACE STATION PLAY
VIDEO: PREVIEW OF FLIGHT DAY 13 ACTIVITIES PLAY

VIDEO: FLIGHT DAY 12 HIGHLIGHTS MOVIE PLAY
VIDEO: FRIDAY MORNING'S MISSION STATUS BRIEFING PLAY
VIDEO: SHUTTLE AND STATION CREWS BID THEIR FAREWELLS PLAY
VIDEO: RIBBON-CUTTING CEREMONY FOR STATION'S CUPOLA PLAY
VIDEO: IN-FLIGHT CREW NEWS CONFERENCE FOR U.S AND JAPAN PLAY

VIDEO: FLIGHT DAY 11 HIGHLIGHTS MOVIE PLAY
VIDEO: THURSDAY MORNING'S MISSION STATUS BRIEFING PLAY
VIDEO: OXYGEN GENERATOR RELOCATED TO TRANQUILITY PLAY
VIDEO: STATION'S TOILET INSTALLED IN THE NEW MODULE PLAY
VIDEO: WATER GENERATING EQUIPMENT MOVED INTO TRANQUILITY PLAY
VIDEO: PRESIDENT OBAMA CALLS SHUTTLE AND STATION CREWS PLAY

VIDEO: DAZZLING VIEWS FROM INSIDE CUPOLA PLAY
VIDEO: CUPOLA WINDOW SHUTTERS ARE TESTED PLAY
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VIDEO: FLIGHT DAY 10 HIGHLIGHTS MOVIE PLAY
VIDEO: WEDNESDAY MORNING'S MISSION STATUS BRIEFING PLAY
VIDEO: CUPOLA OPEN FOR VIEWING PLAY
VIDEO: FREEING THE SHUTTERS PLAY
VIDEO: CUPOLA IS UNVEILED! PLAY
VIDEO: FIRST HALF OF CUPOLA UNCOVERED PLAY
VIDEO: WIRING UP DOCKING ADAPTER ON TRANQUILITY PLAY
VIDEO: ACTIVATING TRANQUILITY'S OTHER COOLING LOOP PLAY
VIDEO: SPACEWALKERS FLOAT OUT OF AIRLOCK PLAY
VIDEO: STEP-BY-STEP PREVIEW OF SPACEWALK NO. 3 PLAY
VIDEO: PREVIEW OF FLIGHT DAY 10 ACTIVITIES PLAY

VIDEO: FLY WITH THE ASTRONAUTS IN THE COCKPIT PLAY
VIDEO: LOOKING OUT THE PILOT'S FRONT WINDOW PLAY
VIDEO: LEFT-HAND BOOSTER CAMERA LOOKING UPWARD PLAY
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VIDEO: LEFT-HAND BOOSTER CAMERA LOOKING DOWNWARD PLAY
VIDEO: RIGHT-HAND BOOSTER CAMERA LOOKING UPWARD PLAY
VIDEO: RIGHT-HAND BOOSTER CAMERA LOOKING INBOARD PLAY
VIDEO: RIGHT-HAND BOOSTER CAMERA LOOKING DOWNWARD PLAY
VIDEO: EXTERNAL TANK CAMERA FROM LIFTOFF TO SEPARATION PLAY

VIDEO: FLIGHT DAY 9 HIGHLIGHTS MOVIE PLAY
VIDEO: TUESDAY MORNING'S MISSION STATUS BRIEFING PLAY
VIDEO: DOCKING ADAPTER PLACED ONTO TRANQUILITY PLAY
VIDEO: PREVIEW OF FLIGHT DAY 9 ACTIVITIES PLAY

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VIDEO: CREW'S EDUCATIONAL EVENT PLAY
VIDEO: PREVIEW OF FLIGHT DAY 8 ACTIVITIES PLAY
VIDEO: SUNDAY AFTERNOON'S FLIGHT DIRECTOR INTERVIEW PLAY

VIDEO: FLIGHT DAY 7 HIGHLIGHTS MOVIE PLAY
VIDEO: SUNDAY MORNING'S MISSION STATUS BRIEFING PLAY
VIDEO: PREPPING CUPOLA'S NEW HOME PORT PLAY
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VIDEO: FLIGHT DAY 6 HIGHLIGHTS MOVIE PLAY
VIDEO: OPENING CUPOLA'S HATCHWAY BRIEFLY PLAY
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VIDEO: SPACEWALKERS ANSWER TWITTER QUESTIONS PLAY
VIDEO: ASSOCIATED PRESS, CBS AND REUTERS MEDIA INTERVIEWS PLAY
VIDEO: SATURDAY MORNING'S MISSION STATUS BRIEFING PLAY
VIDEO: PREVIEW OF FLIGHT DAY 6 ACTIVITIES PLAY

VIDEO: FRIDAY AFTERNOON'S MANAGEMENT TEAM UPDATE PLAY
VIDEO: FRIDAY MORNING'S MISSION STATUS BRIEFING PLAY
VIDEO: FLIGHT DAY 5 HIGHLIGHTS MOVIE PLAY
VIDEO: STEP-BY-STEP PREVIEW OF SPACEWALK NO. 1 PLAY
VIDEO: PREVIEW OF FLIGHT DAY 5 ACTIVITIES PLAY

VIDEO: FLIGHT DAY 4 HIGHLIGHTS MOVIE PLAY
VIDEO: WEDNESDAY NIGHT'S MISSION STATUS BRIEFING PLAY
VIDEO: SACRAMENTO, MOBILE AND ST. LOUIS MEDIA INTERVIEWS PLAY
VIDEO: WEDNESDAY AFTERNOON'S MANAGEMENT TEAM UPDATE PLAY
VIDEO: WEDNESDAY MORNING'S FLIGHT DIRECTOR INTERVIEW PLAY
VIDEO: PREVIEW OF FLIGHT DAY 4 ACTIVITIES PLAY

VIDEO: FLIGHT DAY 3 HIGHLIGHTS MOVIE PLAY
VIDEO: WEDNESDAY MORNING'S MISSION STATUS BRIEFING PLAY
VIDEO: SHUTTLE CREW WELCOMED ABOARD STATION PLAY
VIDEO: HATCHWAY OPENED BETWEEN TWO SPACECRAFT PLAY
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VIDEO: STUNNING SHOT OF SHUTTLE AGAINST HORIZON PLAY
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VIDEO: TUESDAY AFTERNOON'S MANAGEMENT TEAM UPDATE PLAY

VIDEO: AMAZING LAUNCH FOOTAGE FROM COCKPIT CAMERA PLAY

VIDEO: FLIGHT DAY 2 HIGHLIGHTS MOVIE PLAY
VIDEO: TUESDAY'S MISSION STATUS BRIEFING PLAY
VIDEO: TIME-LAPSE OF WING INSPECTIONS PLAY
VIDEO: INSPECTION BOOM READIED FOR USE PLAY
VIDEO: PREVIEW OF FLIGHT DAY 2 ACTIVITIES PLAY
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VIDEO: FLIGHT DAY 1 HIGHLIGHTS MOVIE PLAY
VIDEO: THE FULL STS-130 LAUNCH EXPERIENCE PLAY
VIDEO: SHUTTLE ENDEAVOUR BLASTS OFF! PLAY | HI-DEF
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VIDEO: PAYLOAD BAY DOORS OPENED FOLLOWING LAUNCH PLAY

VIDEO: CREW FINISHES GETTING SUITED UP PLAY
VIDEO: ASTRONAUTS LEAVE CREW QUARTERS PLAY | HI-DEF
VIDEO: CREW ARRIVES AT LAUNCH PAD 39A PLAY
VIDEO: ASTRONAUTS BOARD THEIR SPACECRAFT PLAY

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VIDEO: LAUNCH REPLAY: PRESS SITE PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: PAD PERIMETER PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: BEACH TRACKER PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: PAD CAMERA 070 PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: PAD CAMERA 071 PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: UCS-23 TRACKER PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: PLAYALINDA BEACH PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: PAD FRONT CAMERA PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: BANANA CREEK SITE PLAY | HI-DEF

VIDEO: NARRATED REVIEW OF SHUTTLE'S PREPARATIONS PLAY | HI-DEF
VIDEO: NARRATED REVIEW OF PAYLOADS' PREPARATIONS PLAY | HI-DEF

VIDEO: EXPLANATION OF WEATHER PROBLEMS PLAY | HI-DEF
VIDEO: LOW CLOUDS SCRUB FIRST COUNTDOWN PLAY | HI-DEF
VIDEO: ASTRONAUTS DEPART QUARTERS FOR PAD 39A PLAY | HI-DEF
VIDEO: CREW GETS SUITED UP FOR LAUNCH ATTEMPT PLAY | HI-DEF
VIDEO: PAD SERVICE GANTRY RETRACTED PLAY | HI-DEF
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VIDEO: INTERVIEW WITH COMMANDER GEORGE ZAMKA PLAY
VIDEO: INTERVIEW WITH PILOT TERRY VIRTS PLAY
VIDEO: INTERVIEW WITH MISSION SPECIALIST 1 KAY HIRE PLAY
VIDEO: INTERVIEW WITH MISSION SPECIALIST 2 STEVE ROBINSON PLAY
VIDEO: INTERVIEW WITH MISSION SPECIALIST 3 NICK PATRICK PLAY
VIDEO: INTERVIEW WITH MISSION SPECIALIST 4 BOB BEHNKEN PLAY

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VIDEO: THURSDAY STATUS AND WEATHER UPDATE PLAY
VIDEO: COUNTDOWN PREVIEW BRIEFING PLAY
VIDEO: ASTRONAUTS ARRIVE FOR LAUNCH PLAY | HI-DEF

VIDEO: LAUNCH DATE SET AT FLIGHT READINESS REVIEW PLAY
VIDEO: PAYLOAD BAY DOORS CLOSED FOR LAUNCH PLAY | HI-DEF
VIDEO: CREW SEES TRANQUILITY LOADED INTO SHUTTLE PLAY | HI-DEF

VIDEO: SHUTTLE EVACUATION PRACTICE PLAY | HI-DEF
VIDEO: ASTRONAUTS BOARD ENDEAVOUR PLAY | HI-DEF
VIDEO: THE LAUNCH DAY SIMULATION BEGINS PLAY | HI-DEF
VIDEO: PAD BUNKER TRAINING FOR THE CREW PLAY | HI-DEF
VIDEO: CREW BRIEFED ON EMERGENCY PROCEDURES PLAY | HI-DEF
VIDEO: TEST-DRIVING AN EMERGENCY ARMORED TANK PLAY | HI-DEF
VIDEO: NIGHTTIME APPROACHES IN TRAINING AIRCRAFT PLAY | HI-DEF
VIDEO: ASTRONAUTS CHAT WITH REPORTERS AT PAD 39A PLAY
VIDEO: SPACEWALKER UPDATES COOLING HOSE FIX PLAY | HI-DEF
VIDEO: ROBINSON'S THOUGHTS ON SHUTTLE RETIREMENT PLAY | HI-DEF
VIDEO: ASTRONAUTS ARRIVE FOR PRACTICE COUNTDOWN PLAY | HI-DEF

VIDEO: TRANQUILITY DELIVERED TO PAD 39A PLAY | HI-DEF
VIDEO: PAYLOAD TRANSPORTER GOES UPRIGHT PLAY | HI-DEF
VIDEO: PACKING UP PAYLOAD FOR LAUNCH PLAY | HI-DEF

VIDEO: SHUTTLE ENDEAVOUR'S FRIGID ROLLOUT TO PAD PLAY | HI-DEF
VIDEO: ENDEAVOUR HOISTED FOR ATTACHMENT TO TANK PLAY | HI-DEF
VIDEO: CRANE ROTATES THE ORBITER VERTICALLY PLAY | HI-DEF
VIDEO: ENDEAVOUR MOVES TO ASSEMBLY BUILDING PLAY | HI-DEF
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VIDEO: EXTERNAL TANK ATTACHED TO BOOSTERS PLAY | HI-DEF
VIDEO: ENDEAVOUR'S MAIN ENGINE INSTALLATION PLAY | HI-DEF
VIDEO: ASTRONAUTS VISIT THEIR SPACECRAFT PLAY | HI-DEF
VIDEO: CREW INSPECTS MISSION PAYLOADS PLAY | HI-DEF
VIDEO: FUEL TANK UNLOADED FROM THE BARGE PLAY | HI-DEF
VIDEO: EXTERNAL TANK ARRIVES AT SPACEPORT PLAY | HI-DEF
VIDEO: FORWARD THRUSTER POD CHECKED OUT PLAY | HI-DEF
VIDEO: ENDEAVOUR TOWED OFF RUNWAY FROM STS-127 PLAY | HI-DEF

VIDEO: TRANQUILITY HATCH SEALED FOR LAUNCH PLAY | HI-DEF
VIDEO: CUPOLA ATTACHED TO TRANQUILITY PLAY | HI-DEF
VIDEO: THE SPACE STATION'S NEW CUPOLA PLAY | HI-DEF
VIDEO: TRANQUILITY UNPACKED IN FLORIDA PLAY | HI-DEF
VIDEO: NEW MODULE ARRIVES FROM EUROPE PLAY | HI-DEF
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