With good weather expected, NASA managers Wednesday cleared the shuttle Discovery for launch Thursday on a long-delayed space station resupply mission, the orbiter's 39th and final flight.

Credit: Spaceflight Now

Mike Moses, the shuttle integration manager at the Kennedy Space Center, said Discovery's countdown was proceeding smoothly with no technical problems of any significance at pad 39A.

"Today we held our launch minus-one-day mission management team meeting where we got together just to discuss our current status and our readiness," he told reporters. "Everything is on track, going beautifully with the countdown and we are more than ready for tomorrow's launch."

Discovery is scheduled for liftoff at 4:50:27 p.m. EST (GMT-5), the middle of a 10-minute window that roughly coincides with the moment Earth's rotation carries the launch pad into the plane of the International Space Station's orbit. The shuttle must launch within five minutes of that "in-plane" time to reach the lab complex.

Shuttle weather officer Kathy WInters said forecasters are continuing to predict an 80 percent chance of good weather. The outlook deteriorates slightly over the next few days as a frontal system moves through the area, with the odds dropping to 70 percent "go" Friday and 60 percent on Saturday.

The primary goals of the 133rd shuttle flight are to deliver supplies, science gear, spare parts and other equipment to the space station, along with a final U.S. module that will be used as an orbital storage depot.

"We've been ready from a mission standpoint for quite a while, now our hardware's in line and ready to go," Moses said. "We're delivering the PMM, the permanent Multi-purpose Module, which will be basically a really good addition to space station in terms of storage capability on orbit.

"We're taking up the ELC-4, external logistics cargo pallet, which has a spare radiator and room for other spare hardware once it gets on orbit and stowed on the station. We have two very busy EVAs (spacewalks) to clean up a lot of (unfinished) activities and prepare the station for the future."

The astronauts also will deliver science hardware and a variety of experiments, along with a humanoid technology demonstration robot known as Robonaut 2.

"So we're really looking forward to a very action-packed, successful mission and everything's on track," Moses said.

Launch originally was planned for last Nov. 1, but the flight was delayed by technical problems, bad weather and ultimately by cracks in the ship's external tank. The cracks have since been repaired and structural stiffeners were added to make rib-like stringers less susceptible to stress-relief fractures.

Launch Director Mike Leinbach said figuring out the root cause of the cracks was one of the most challenging realtime shuttle problems in the 30-year history of the program. But "we fixed the tank, we're going to fly it tomorrow and it's going to perform perfectly fine."

Discovery is NASA's most seasoned orbiter and it will be making its final voyage Thursday, followed by the final flight of Endeavour in April and Atlantis later this summer.

Asked if emotions were running high going into Discovery's final launch count, Leinbach said "the last flight of all three vehicles is going to be emotional for all of us."

"Landing day's going to be tough," he said. "Landing day of Discovery, and then Endeavour and especially Atlantis, the last mission, you'll see a lot of people on the runway who will probably choke up some. Because it's the end of a 30-year program that not only have we worked in and made our livelihoods in, but we've grown to love and appreciate and feel like we're doing something special for the country and, really, the world. And it's coming to an end, and that's tough.

"But we're going to do it right, we're going to approach each of these three flights the way we approached all the other ones, we'll pull them off and be able to look back and be very, very proud of what we've accomplished in the shuttle program."

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Additional coverage for subscribers:
VIDEO: THE PRE-LAUNCH NEWS CONFERENCE PLAY
VIDEO: DISCOVERY'S COUNTDOWN IS UNDERWAY PLAY
VIDEO: LAUNCH COUNTDOWN PREVIEW AND WEATHER FORECAST PLAY
VIDEO: ASTRONAUTS ARRIVE AT LAUNCH SITE AGAIN PLAY | HI-DEF
VIDEO: DISCOVERY CLEARED FOR LAUNCH ON FEB. 24 PLAY

VIDEO: STEVE BOWEN BEGINS CREW TRAINING PLAY | HI-DEF

VIDEO: SUN RISES OVER SPACEPORT AFTER ROLLOUT PLAY | HI-DEF
VIDEO: SHUTTLE ARRIVES ATOP LAUNCH PAD 39A AGAIN PLAY | HI-DEF
VIDEO: CROWDS CHEER ON DISCOVERY'S ROLLOUT PLAY | HI-DEF
VIDEO: DISCOVERY RE-EMERGES FROM THE VAB PLAY | HI-DEF
VIDEO: LAUNCH TEAM PRACTICES PROCEDURES PLAY | HI-DEF

VIDEO: FRESH FOAM APPLIED TO EXTERNAL TANK PLAY | HI-DEF

VIDEO: ROOT CAUSE OF SHUTTLE TANK CRACKS FOUND PLAY

VIDEO: REPAIRS AND STRENGTHENING TO TANK PLAY | HI-DEF
VIDEO: DIGITAL X-RAY INSPECTIONS IN THE VAB PLAY | HI-DEF
VIDEO: WORK UNDERWAY TO REMOVE FOAM AND SENSORS PLAY | HI-DEF
VIDEO: SETTING UP ACCESS PLATFORMS AROUND TANK PLAY | HI-DEF

VIDEO: SHUTTLE ROLLED BACK TO ASSEMBLY BUILDING PLAY | HI-DEF
VIDEO: DISCOVERY DEPARTS LAUNCH PAD 39A PLAY | HI-DEF
VIDEO: LUNAR ECLIPSE OVER DISCOVERY PLAY | HI-DEF

VIDEO: HIGHLIGHTS FROM THE FUELING TEST PLAY | HI-DEF
VIDEO: RECAP OF THE FUELING EXERCISE PLAY
VIDEO: FUELING TEST COUNTDOWN UPDATE PLAY
VIDEO: COMMENTS FROM SHUTTLE LAUNCH DIRECTOR PLAY
VIDEO: GROUND UMBILICAL CARRIER PLATE CHECKED PLAY
VIDEO: INFO ON EXTERNAL TANK INSTRUMENTATION PLAY
VIDEO: DETAILED INFORMATION ON SPECIAL FUELING TEST PLAY

VIDEO: SHUTTLE DISCOVERY'S LAUNCH DELAYED TO FEBRUARY PLAY

VIDEO: FINAL PREPS FOR INSTRUMENTED TEST PLAY | HI-DEF
VIDEO: STRAIN GAUGES ATTACHED TO TANK PLAY | HI-DEF
VIDEO: BACKSCATTER INSPECTIONS OF TANK MIDSECTION PLAY | HI-DEF

VIDEO: INSTALLING DOUBLERS OVER STRINGERS PLAY | HI-DEF
VIDEO: GASEOUS HYDROGEN VENT ARM RETURNED PLAY | HI-DEF
VIDEO: DOUBLERS TO BEEF UP CRACKED BEAMS PLAY | HI-DEF
VIDEO: HYDROGEN FITTING IS REINSTALLED PLAY | HI-DEF
VIDEO: OPENING UP TANK'S ENTRANCE DOOR PLAY | HI-DEF
VIDEO: GUCP DETACHED AND SEALS REMOVED PLAY | HI-DEF
VIDEO: BROKEN FOAM REMOVED FROM THE TANK PLAY | HI-DEF
VIDEO: VENT ARM LETS GO FROM LEAKY GUCP PLAY | HI-DEF
VIDEO: DISCOVERY AWAITS REPAIRS TO TANK PROBLEMS PLAY | HI-DEF

VIDEO: INFORMATIVE DESCRIPTION OF TANK CRACK PROBLEM PLAY
VIDEO: DISCOVERY'S LAUNCH DELAYED TO MID-DECEMBER PLAY

VIDEO: GASEOUS HYDROGEN VENT ARM DETACHED FROM SHUTTLE PLAY

VIDEO: STS-133 MISSION PREVIEW MOVIE PLAY | HI-DEF
VIDEO: SHUTTLE DISCOVERY CREW BIOGRAPHIES PLAY | HI-DEF
VIDEO: ISS EXPEDITION 25-26 PREVIEW MOVIE PLAY | HI-DEF
VIDEO: SPACE STATION CREW BIOGRAPHIES PLAY | HI-DEF

VIDEO: POST-SCRUB NEWS BRIEFING ON LEAK PLAY
VIDEO: GASEOUS HYDROGEN LEAK SCRUBS LAUNCH PLAY | HI-DEF
VIDEO: BAD WEATHER DELAYS DISCOVERY LAUNCH PLAY
VIDEO: ELECTRICAL ISSUE NO LONGER A CONCERN FOR DISCOVERY PLAY
VIDEO: LAUNCH POSTPONED BY ELECTRICAL CONCERN PLAY
VIDEO: TUESDAY MORNING'S COUNTDOWN STATUS CHECK PLAY
VIDEO: DISCOVERY'S PRE-LAUNCH NEWS CONFERENCE PLAY
VIDEO: COUNTDOWN PREVIEW BRIEFING AND WEATHER FORECAST PLAY
VIDEO: ANOTHER 24-HOUR DELAY ORDERED TO FINISH REPAIRS PLAY
VIDEO: LAUNCH DELAYED 24 HOURS BY LEAK REPAIRS PLAY

VIDEO: ASTRONAUTS ARRIVE FOR LAUNCH PLAY | HI-DEF

VIDEO: FLIGHT READINESS REVIEW SETS LAUNCH DATE PLAY

VIDEO: SHUTTLE AND STATION PROGRAM BRIEFING PLAY
VIDEO: THE STS-133 MISSION OVERVIEW PRESENTATIONS PLAY
VIDEO: PREVIEW BRIEFING ON MISSION'S SPACEWALKS PLAY
VIDEO: IN-DEPTH BACKGROUND ON ROBONAUT 2 HUMANOID PLAY
VIDEO: THE ASTRONAUTS' PRE-FLIGHT NEWS BRIEFING PLAY

VIDEO: PAYLOAD BAY DOORS CLOSED FOR LAUNCH PLAY | HI-DEF
VIDEO: CREW LEAVES KSC FOR TRIP TO HOUSTON PLAY | HI-DEF
VIDEO: ASTRONAUTS INSPECT THE PAYLOAD BAY PLAY | HI-DEF
VIDEO: SHUTTLE EVACUATION PRACTICE PLAY | HI-DEF
VIDEO: ASTRONAUTS EGRESS SHUTTLE AS SEEN LIVE PLAY
VIDEO: ASTRONAUTS BOARD DISCOVERY PLAY | HI-DEF
VIDEO: SUN RISES ON LAUNCH PAD 39A PLAY | HI-DEF
VIDEO: LAUNCH DAY REHEARSAL BEGINS PLAY | HI-DEF
VIDEO: COMMEMORATIVE WALL SIGNING IN VAB PLAY | HI-DEF
VIDEO: CREW BRIEFED ON EMERGENCY PROCEDURES PLAY | HI-DEF
VIDEO: IN SHUTTLE TRAINING AIRCRAFT'S COCKPIT PLAY | HI-DEF
VIDEO: TEST-DRIVING AN EMERGENCY ARMORED TANK PLAY | HI-DEF

VIDEO: PRE-LAUNCH INTERVIEW WITH STEVE LINDSEY PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH ERIC BOE PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH AL DREW PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH TIM KOPRA PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH MIKE BARRATT PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH NICOLE STOTT PLAY

VIDEO: PAYLOADS INSTALLED INTO DISCOVERY PLAY | HI-DEF
VIDEO: MISSION PAYLOADS ARRIVE AT LAUNCH PAD PLAY | HI-DEF
VIDEO: CANISTER HAULING PAYLOADS TURNED UPRIGHT PLAY | HI-DEF
VIDEO: MODULE HOISTED INTO SHIPPING CANISTER PLAY | HI-DEF
VIDEO: WEIGHING NEW SPACE STATION MODULE PLAY | HI-DEF

VIDEO: GANTRY PLACED AROUND DISCOVERY PLAY | HI-DEF
VIDEO: SHUTTLE ATLANTIS REACHES PAD 39A PLAY | HI-DEF
VIDEO: CROWDS WATCH DISCOVERY'S FINAL ROLLOUT PLAY | HI-DEF

VIDEO: SHUTTLE HOISTED FOR ATTACHMENT TO TANK PLAY | HI-DEF
VIDEO: CRANE ROTATES THE ORBITER VERTICALLY PLAY | HI-DEF
VIDEO: DISCOVERY DEPARTS ITS HANGAR PLAY | HI-DEF

VIDEO: TIME-LAPSE SHOWS DISCOVERY ASCENDING IN VAB PLAY
VIDEO: TIME-LAPSE SHOWS THE MOVE TO ASSEMBLY BUILDING PLAY

VIDEO: DISCOVERY'S MAIDEN FLIGHT: FIRST TRIP TO VAB PLAY
VIDEO: DISCOVERY'S MAIDEN FLIGHT: ROLLOUT TO PAD 39A PLAY
VIDEO: DISCOVERY'S MAIDEN FLIGHT: TEST-FIRING ENGINES PLAY
VIDEO: DISCOVERY'S MAIDEN FLIGHT: ASSORTED VIEWS OF FRF PLAY

VIDEO: THE HISTORY OF SHUTTLE DISCOVERY PLAY
VIDEO: THE HISTORY OF SHUTTLE ENDEAVOUR PLAY
VIDEO: THE HISTORY OF SHUTTLE ATLANTIS PLAY

VIDEO: INSPECTION OF THE MISSION PAYLOADS PLAY | HI-DEF
VIDEO: ROBONAUT ARRIVES AT KENNEDY SPACE CENTER PLAY | HI-DEF
VIDEO: SPACE STATION'S SPARE THERMAL RADIATOR PLAY | HI-DEF
VIDEO: BLANKETING LEONARDO WITH INSULATION PLAY | HI-DEF
VIDEO: RACK INSERTED INTO LEONARDO FOR LAUNCH PLAY | HI-DEF
VIDEO: LEONARDO RETURNS FROM ITS PREVIOUS FLIGHT PLAY | HI-DEF
VIDEO: STATION'S SPARE PARTS DEPOT ARRIVES PLAY | HI-DEF

VIDEO: ORBITER'S PAYLOAD BAY CLOSED FOR ROLLOUT PLAY | HI-DEF
VIDEO: ASTRONAUTS VISIT THEIR SPACECRAFT PLAY | HI-DEF
VIDEO: CREW INSPECTS LEONARDO MODULE PLAY | HI-DEF
VIDEO: DISCOVERY RECEIVES ITS MAIN ENGINES PLAY | HI-DEF
VIDEO: FUEL TANK MATED TO SOLID ROCKET BOOSTERS PLAY | HI-DEF
VIDEO: HOISTING FUEL TANK INTO CHECKOUT BAY PLAY | HI-DEF
VIDEO: EXTERNAL FUEL TANK UNLOADED FROM BARGE PLAY | HI-DEF
VIDEO: MISSION'S FUEL TANK ARRIVES AT SPACEPORT PLAY | HI-DEF

VIDEO: POST-FLIGHT DESERVICING: OMS POD PLAY | HI-DEF
VIDEO: POST-FLIGHT DESERVICING: OBSS BOOM PLAY | HI-DEF
VIDEO: POST-FLIGHT DESERVICING: ENGINES PLAY | HI-DEF
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