With flight controllers keeping tabs on threatening weather, the Discovery astronauts packed up Wednesday and tested the shuttle's re-entry systems in preparation for landing Thursday at the Kennedy Space Center, weather permitting, to close out a successful space station resupply mission.

Credit: NASA

Commander Frederick Sturckow and his crewmates - pilot Kevin Ford, flight engineer Jose Hernandez, Patrick Forrester, John "Danny" Olivas, European Space Agency astronaut Christer Fuglesang and returning space station flight engineer Timothy Kopra - have two landing opportunities Wednesday, the first at 7:05 p.m. EDT and the second at 8:42 p.m.

There are no technical problems with the shuttle, but forecasters are predicting rain showers and possible thunderstorms in the Kennedy Space Center area that could cause problems Thursday and Friday.

"The weather tomorrow as (on) the following few days at the Kennedy Space Center, is going to be challenging," entry Flight Director Richard Jones said late Wednesday. "Just like any time here in the late summer, when the sun's out and the daytime heating effects are kind of boiling up the atmosphere a bit, we can expect some rain or some thunderstorms within the area. Hopefully, those thunderstorms are going to be staying away, outside of our 30-nautical-mile flight rule circle we have to keep them out of.

"We had a great chance to look at the weather today as it was streaming into the Kennedy Space Center area. And you could kind of see some lines of convergence, streams of thunderstorms as they were coming into the area. But as they were coming in, you could definitely see some areas of dryness, or some clearing. Hopefully, that same condition will be there tomorrow. Now, it's going to be a little bit iffy in terms of whether that dryness will be there or not, but if it is, that could work in our favor."

The forecast for NASA's backup landing site at Edwards Air Force Base in California's Mojave Desert calls for good conditions for several days in a row.

Discovery has enough supplies to remain in orbit through Sunday at the latest, but NASA managers would bring the ship down Saturday, on one coast or the other, if the weather or technical problems prevent a landing Thursday or Friday. If the Florida weather takes a dramatic turn for the worse, Jones could elect to divert the shuttle to Edwards on Friday. But the going-in plan is to shoot for a Florida landing if at all possible.

Earlier Wednesday, Sturckow, Ford and Hernandez tested the shuttle's re-entry systems, firing up one of the ship's three hydraulic power systems, exercising the shuttle's elevons and rudder and test firing the orbiter's primary reaction control system thrusters.

During the flight control system checkout, Fuglesang reported spotting a small piece of debris floating away from the shuttle.

"During the FCS checkout, during the first portion of that when we're running the auxiliary power unit and we do some secondary actuator checks that really shake the vehicle up, we did lose a piece of debris, the crew did capture that in some still shots," Jones said. "We weren't able to come to a definitive conclusion as to what that object was. But we definitively came to the conclusion that it is not a piece of the thermal protection system."

NASA's Mission Management Team, meanwhile, formally cleared Discovery's heat shield for re-entry after a final inspection of the ship's nose cap and wing leading edge panels.

Here are all the landing opportunities available to Discovery's crew Thursday, Friday and Saturday (in EDT):

ORBIT......DEORBIT........LANDING.......SITE

09/10
202........05:59 PM.......07:05 PM......Kennedy Space Center
203........07:36 PM.......08:42 PM......KSC

09/11
217........04:51 PM........05:54 PM......KSC
218........06:26 PM........07:29 PM......KSC
219........07:56 PM........08:59 PM......Edwards Air Force Base
220........09:32 PM........10:34 PM......EDW

09/12
233........05:15 PM........06:17 PM......KSC
234........06:45 PM........07:48 PM......EDW
234........06:51 PM........07:53 PM......KSC
235........08:20 PM........09:23 PM......EDW
236........09:57 PM........10:59 PM......EDW

The astronauts are scheduled to begin their day at 10:59 a.m. Thursday. Deorbit preparations for the first of the crew's two landing opportunities will begin around 2 p.m. Here are detailed timelines for both opportunities (in EDT):

EDT...........EVENT

Rev. 202 deorbit to KSC

01:59 PM......Begin deorbit timeline
02:14 PM......Radiator stow
02:24 PM......Mission specialists seat installation
02:30 PM......Computers set for deorbit prep
02:34 PM......Hydraulic system configuration
02:59 PM......Flash evaporator cooling system checkout
03:05 PM......Final payload deactivation
03:19 PM......Payload bay doors closed
03:29 PM......Mission control 'go' for OPS-3 software load
03:39 PM......OPS-3 entry software loaded
04:04 PM......Entry switch list verification
04:14 PM......Deorbit maneuver update
04:19 PM......Crew entry review
04:34 PM......Commander/pilot don entry suits
04:51 PM......IMU alignment
04:59 PM......CDR/PLT strap in; others don suits
05:16 PM......Shuttle steering check
05:19 PM......Hydraulic system prestart
05:26 PM......Toilet deactivation

05:39 PM......Mission control 'go' for deorbit burn
05:45 PM......Astronaut seat ingress
05:54 PM......Single APU start

05:59:07 PM...Deorbit ignition (dT: 2:55; dV: 202 mph)
06:02:02 PM...Deorbit burn complete

06:33:57 PM...Entry interface (range to KSC: 5,071 miles)
06:38:57 PM...1st roll command to right
06:46:01 PM...1st roll to left
06:52:00 PM...C-band radar acquisition
06:59:14 PM...Velocity less than mach 2.5
07:01:24 PM...Velocity less than mach 1
07:02:09 PM...215-degree left turn to runway 15
07:05:40 PM...Landing


Rev. 203 Deorbit to KSC

07:16 PM......MCC 'go' for deorbit burn
07:22 PM......MS seat ingress
07:31 PM......Single APU start

07:36:37 PM...Deorbit ignition
07:39:31 PM...Deorbit burn complete

08:10:03 PM...Entry interface
08:15:00 PM...1st roll command to right
08:31:58 PM...1st right-to-left roll reversal
08:35:44 PM...Velocity less than mach 2.5
08:37:49 PM...Velocity less than mach 1
08:38:00 PM...259-degree left turn to runway 15
08:42:13 PM...Landing

Jones said the weather Thursday likely would be "very challenging."

"I've had a chance to stare at weather, working as a weather flight director and as an ascent and entry flight director on other missions, and the weather's the weather," he said. "You have to kind of watch it and make sure it's behaving in the manner you want it to. And tomorrow ... it's going to look somewhat nasty, it's not going to look 'go' in the early portions of the deorbit prep. We're going to be looking for maybe a trend where it's dissipating as we get closer to the deorbit burn, looking for that area of dryness I was trying to communicate earlier."

Additional coverage for subscribers:
VIDEO: FLIGHT DAY 13 HIGHLIGHTS MOVIE PLAY
VIDEO: PREVIEW OF DISCOVERY'S RE-ENTRY EXPERIMENT PLAY
VIDEO: PRE-LANDING BRIEFING WITH ENTRY FLIGHT DIRECTOR PLAY
VIDEO: CREW INTERVIEWS WITH CBS, ABC AND CNN PLAY
VIDEO: ASTRONAUTS' HOME MOVIES: DAY 12 PLAY
VIDEO: ASTRONAUTS' HOME MOVIES: DAY 11 PLAY
VIDEO: ASTRONAUTS' HOME MOVIES: DAY 10-P2 PLAY

VIDEO: FLIGHT DAY 12 HIGHLIGHTS MOVIE PLAY
VIDEO: TUESDAY EVENING'S MISSION STATUS BRIEFING PLAY
VIDEO: DISCOVERY FLIES AROUND INTERNATIONAL SPACE STATION PLAY
VIDEO: SHUTTLE DISCOVERY UNDOCKS FROM SPACE STATION PLAY
VIDEO: TUESDAY MORNING FLIGHT DIRECTOR INTERVIEW PLAY

VIDEO: FLIGHT DAY 11 HIGHLIGHTS MOVIE PLAY
VIDEO: MONDAY EVENING'S MISSION STATUS BRIEFING PLAY
VIDEO: FAREWELL BETWEEN SHUTTLE AND STATION CREWS PLAY
VIDEO: LEONARDO MODULE RETURNED TO THE PAYLOAD BAY PLAY
VIDEO: ASTRONAUTS ANSWER QUESTIONS SUBMITTED BY PUBLIC PLAY
VIDEO: TELEMUNDO, TAMPA AND UNIVISION CREW INTERVIEWS PLAY
VIDEO: EL PASO AND AUSTIN TELEVISION CREW INTERVIEWS PLAY
VIDEO: JOSE HERNANDEZ LIVE INTERVIEWS FROM ORBIT PLAY
VIDEO: MONDAY MORNING FLIGHT DIRECTOR INTERVIEW PLAY

VIDEO: FLIGHT DAY 10 HIGHLIGHTS MOVIE PLAY
VIDEO: EUROPEAN SPACE AGENCY ASTRONAUT EVENT PLAY
VIDEO: ASTRONAUTS' HOME MOVIES: DAY 10 PLAY
VIDEO: ASTRONAUTS' HOME MOVIES: DAY 9 PLAY
VIDEO: SUNDAY MORNING FLIGHT DIRECTOR INTERVIEW PLAY

VIDEO: POST-EVA MISSION STATUS BRIEFING PLAY
VIDEO: FLIGHT DAY 9 HIGHLIGHTS MOVIE PLAY
VIDEO: FUGLESANG'S HELMET-CAM COMES LOOSE PLAY
VIDEO: ROUTING AVONICS CABLES FOR TRANQUILITY PLAY
VIDEO: FAILED ORIENTATION SENSOR REMOVED PLAY
VIDEO: WORK TO DEPLOY PAYLOAD MECHANISM PLAY
VIDEO: EVA NO. 3 BEGINS PLAY
VIDEO: SATURDAY MORNING FLIGHT DIRECTOR INTERVIEW PLAY

VIDEO: ASTRONAUTS' HOME MOVIES: DAY 8 PLAY
VIDEO: INTERNATIONAL CREW NEWS CONFERENCE PLAY
VIDEO: FLIGHT DAY 8 HIGHLIGHTS MOVIE PLAY
VIDEO: FRIDAY AFTERNOON'S MISSION STATUS BRIEFING PLAY
VIDEO: FRIDAY MORNING FLIGHT DIRECTOR INTERVIEW PLAY

HIGH DEFINITION TV DAY 7: SPACEWALKERS COME BACK INSIDE PLAY
HIGH DEFINITION TV DAY 7: MORE WORK WITH LEONARDO PLAY
HIGH DEFINITION TV DAY 7: OLIVAS AND FUGLESANG ON EVA PLAY

VIDEO: FLIGHT DAY 7 HIGHLIGHTS MOVIE PLAY
VIDEO: ASTRONAUTS' HOME MOVIES: DAY 7 PLAY
VIDEO: POST-EVA MISSION STATUS BRIEFING PLAY
VIDEO: OLD TANK MOVED TO SHUTTLE FOR RECYCLING PLAY
VIDEO: NEW TANK HOOKED UP TO STATION UMBILICALS PLAY
VIDEO: CHRISTER FUGLESANG CARRIES NEW AMMONIA TANK PLAY
VIDEO: PREPS IN SHUTTLE BAY TO UNPACK NEW AMMONIA TANK PLAY
VIDEO: DANNY OLIVAS FLOATS OUT OF AIRLOCK TO START EVA PLAY
VIDEO: THURSDAY MORNING FLIGHT DIRECTOR INTERVIEW PLAY
VIDEO: STEP-BY-STEP SUMMARY OF SPACEWALK NO. 2 PLAY

HIGH DEFINITION TV DAY 6: PREPPING FOR NEXT EVA PLAY
HIGH DEFINITION TV DAY 6: MOVING FROZEN SCIENCE PLAY
HIGH DEFINITION TV DAY 6: EMPTYING OUT LEONARDO PLAY

HIGH DEFINITION TV DAY 5: SPACEWALKERS CELEBRATE PLAY
HIGH DEFINITION TV DAY 5: OLIVAS AND STOTT ON EVA NO. 1 PLAY
HIGH DEFINITION TV DAY 5: COLBERT TREADMILL UNPACKED PLAY
HIGH DEFINITION TV DAY 5: SPACEWALKERS GET SUITED UP PLAY

HIGH DEFINITION TV DAY 4: LEONARDO MODULE OPENED PLAY
HIGH DEFINITION TV DAY 4: MOVING ITEMS FROM SHUTTLE PLAY

VIDEO: FLIGHT DAY 6 HIGHLIGHTS MOVIE PLAY
VIDEO: ASTRONAUTS' HOME MOVIES: DAY 6 PLAY
VIDEO: WEDNESDAY NIGHT'S MISSION STATUS BRIEFING PLAY
VIDEO: WEDNESDAY MORNING FLIGHT DIRECTOR INTERVIEW PLAY

VIDEO: FLIGHT DAY 5 HIGHLIGHTS MOVIE PLAY
VIDEO: POST-EVA MISSION STATUS BRIEFING PLAY
VIDEO: SPACEWALKERS PUT THIRD EXPERIMENT IN SHUTTLE PLAY
VIDEO: BRIEFCASE-LIKE PACKAGE RETRIEVED FROM STATION PLAY
VIDEO: EUROPEAN PAYLOAD MOVED FROM STATION TO SHUTTLE PLAY
VIDEO: SPACEWALKERS FREE COOLANT TANK FROM TRUSS PLAY
VIDEO: DANNY OLIVAS DISCONNECTS OLD AMMONIA TANK PLAY
VIDEO: ASTRONAUTS EMERGE FROM AIRLOCK TO START EVA PLAY
VIDEO: OVERVIEW OF FLIGHT DAY 5 ACTIVITIES PLAY
VIDEO: STEP-BY-STEP SUMMARY OF SPACEWALK NO. 1 PLAY
VIDEO: TUESDAY MORNING FLIGHT DIRECTOR INTERVIEW PLAY

VIDEO: FLIGHT DAY 4 HIGHLIGHTS MOVIE PLAY
VIDEO: MONDAY NIGHT'S MISSION STATUS BRIEFING PLAY
VIDEO: NARRATED OVERVIEW OF THE LEONARDO PAYLOAD PLAY
VIDEO: ASTRONAUTS OPEN UP AND ENTER LEONARDO MODULE PLAY
VIDEO: TIME-LAPSE OF LEONARDO MODULE'S INSTALLATION PLAY
VIDEO: LEONARDO CARGO MODULE ATTACHED TO STATION PLAY
VIDEO: MONDAY'S MISSION MANAGEMENT TEAM UPDATE PLAY
VIDEO: MONDAY MORNING FLIGHT DIRECTOR INTERVIEW PLAY

HIGH DEFINITION TV DAY 3: NICOLE STOTT ABOARD STATION PLAY
HIGH DEFINITION TV DAY 3: UNITING STATION AND SHUTTLE PLAY
HIGH DEFINITION TV DAY 3: JOIN THE CREW DURING DOCKING PLAY
HIGH DEFINITION TV DAY 3: LIFE ON RENDEZVOUS DAY PLAY

VIDEO: FLIGHT DAY 3 HIGHLIGHTS MOVIE PLAY
VIDEO: SUNDAY NIGHT'S MISSION STATUS BRIEFING PLAY
VIDEO: SHUTTLE CREW WELCOMED ABOARD STATION PLAY
VIDEO: DOCKING RING RETRACTED TO JOIN TWO CRAFT PLAY
VIDEO: TIME-LAPSE OF DOCKING FROM CENTERLINE PLAY
VIDEO: SHUTTLE FLIES OUT IN FRONT OF STATION PLAY
VIDEO: DISCOVERY PERFORMS 360-DEGREE BACKFLIP PLAY
VIDEO: BEAUTIFUL VIEWS OF DISCOVERY APPROACHING PLAY
VIDEO: TIME-LAPSE VIEW FROM SHUTTLE DOCKING PORT PLAY
VIDEO: STATION CAMERA CATCHES DISCOVERY'S "TI BURN" PLAY
VIDEO: SUNDAY'S MISSION MANAGEMENT TEAM UPDATE PLAY
VIDEO: NARRATED PREVIEW OF RENDEZVOUS AND DOCKING PLAY
VIDEO: THE MOON SINKS BELOW TAIL OF DISCOVERY PLAY
VIDEO: ASTRONAUTS' HOME MOVIES: DAY 2 PLAY
VIDEO: ASTRONAUTS' HOME MOVIES: DAY 1 PLAY

VIDEO: FLIGHT DAY 2 HIGHLIGHTS MOVIE PLAY
VIDEO: SATURDAY NIGHT'S MISSION STATUS BRIEFING PLAY
VIDEO: NARRATED PREVIEW OF SHUTTLE INSPECTIONS PLAY

VIDEO: LAUNCH REPLAY: INSIDE MISSION CONTROL ROOM PLAY
VIDEO: LAUNCH REPLAY: VAB ROOF PLAY | HI-DEF
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 CAEMRA 070 PLAY | HI-DEF
VIDEO: LAUNCH REPLAY: PAD CAEMRA 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: PATRICK AIR FORCE BASE PLAY | HI-DEF

VIDEO: POST-LAUNCH BRIEFING PLAY
VIDEO: FLIGHT DAY 1 HIGHLIGHTS MOVIE PLAY
VIDEO: THE FULL LAUNCH EXPERIENCE PLAY
VIDEO: LIFTOFF OF SPACE SHUTTLE DISCOVERY! PLAY | HI-DEF
VIDEO: COMMANDER RICK STURCKOW BOARDS DISCOVERY PLAY
VIDEO: PILOT KEVIN FORD BOARDS SHUTTLE DISCOVERY PLAY
VIDEO: MISSION SPECIALIST PAT FORRESTER BOARDS DISCOVERY PLAY
VIDEO: MISSION SPECIALIST JOSE HERNANDEZ BOARDS SHUTTLE PLAY
VIDEO: MISSION SPECIALIST DANNY OLIVAS BOARDS DISCOVERY PLAY
VIDEO: MISSION SPECIALIST CHRISTER FUGLESANG BOARDS PLAY
VIDEO: MISSION SPECIALIST NICOLE STOTT BOARDS DISCOVERY PLAY
VIDEO: ASTRONAUTS LEAVE CREW QUARTERS BUILDING PLAY | HI-DEF
VIDEO: CREW FINISHES GETTING SUITED UP PLAY | HI-DEF

VIDEO: NARRATED MISSION OVERVIEW MOVIE PLAY | HI-DEF
VIDEO: MEET SHUTTLE DISCOVERY'S ASTRONAUTS PLAY | HI-DEF
VIDEO: NARRATED REVIEW OF SHUTTLE'S PREPARATIONS PLAY | HI-DEF
VIDEO: NARRATED REVIEW OF PAYLOADS' PREPARATIONS PLAY | HI-DEF
VIDEO: THE "COLBERT" TREADMILL PLAY | HI-DEF

VIDEO: MANAGERS EXPLAIN REASON FOR SECOND SCRUB PLAY
VIDEO: WEATHER SCRUBS 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: LAUNCH PAD SERVICE GANTRY ROLLED BACK PLAY | HI-DEF

VIDEO: PRE-LAUNCH INTERVIEW WITH RICK STURCKOW PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH KEVIN FORD PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH PAT FORRESTER PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH JOSE HERNANDEZ PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH DANNY OLIVAS PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH CHRISTER FUGLESANG PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH NICOLE STOTT PLAY

VIDEO: AMERICAN AND EUROPEAN PRE-LAUNCH NEWS CONFERENCE PLAY
VIDEO: THE LAUNCH COUNTDOWN GETS UNDERWAY PLAY
VIDEO: ASTRONAUTS ARRIVE AT THE CAPE FOR LAUNCH PLAY | HI-DEF
VIDEO: FLIGHT READINESS REVIEW SETS LAUNCH DATE PLAY

VIDEO: SHUTTLE AND STATION PROGRAM UPDATE PLAY
VIDEO: THE STS-128 MISSION OVERVIEW BRIEFING PLAY
VIDEO: PREVIEW BRIEFING ON MISSION'S SPACEWALKS PLAY
VIDEO: THE ASTRONAUTS' PRE-FLIGHT NEWS BRIEFING PLAY
VIDEO: SHUTTLE PROGRAM MANAGER EXPLAINS FOAM ISSUES PLAY

VIDEO: PAYLOAD BAY DOORS CLOSED FOR FLIGHT PLAY | HI-DEF
VIDEO: MISSION CARGO LOADED ABOARD DISCOVERY PLAY | HI-DEF

VIDEO: CREW TOURS PAD'S CLEANROOM PLAY | HI-DEF
VIDEO: SHUTTLE EVACUATION PRACTICE PLAY | HI-DEF
VIDEO: ASTRONAUTS BOARD DISCOVERY 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: NIGHTTIME APPROACHES IN TRAINING AIRCRAFT PLAY | HI-DEF
VIDEO: TEST-DRIVING EMERGENCY ARMORED TANK PLAY | HI-DEF
VIDEO: INFORMAL CREW NEWS CONFERENCE AT LAUNCH PAD PLAY
VIDEO: ASTRONAUTS ARRIVE FOR PRACTICE COUNTDOWN PLAY

VIDEO: SHUTTLE DISCOVERY ROLLS OUT PAD 39A PLAY | HI-DEF
VIDEO: ORBITER HOISTED FOR MATING TO TANK PLAY | HI-DEF
VIDEO: DISCOVERY MOVED TO ASSEMBLY BUILDING PLAY | HI-DEF
VIDEO: TIME-LAPSE OF DISCOVERY ARRIVING IN VAB PLAY

VIDEO: PAYLOADS DELIVERED TO LAUNCH PAD PLAY | HI-DEF
VIDEO: LEONARDO PUT INTO TRANSPORTER PLAY | HI-DEF
VIDEO: STATION'S NEW AMMONIA TANK PLAY | HI-DEF
VIDEO: MPLM HATCH CLOSED FOR FLIGHT PLAY | HI-DEF
VIDEO: INSIDE SHUTTLE MAIN ENGINE SHOP PLAY | HI-DEF
VIDEO: CREW EQUIPMENT INTERFACE TEST PLAY | HI-DEF
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