The Endeavour astronauts tested the shuttle's re-entry systems Tuesday and packed for landing Wednesday at the Kennedy Space Center to close out a 16-day space station assembly mission. Entry Flight Director Richard Jones said the shuttle is in good shape and the weather is "go" for a late afternoon descent.

"The flight control system behaved beautifully, there are no issues to really talk about," Jones said of today's entry preparations.

Flying upside down and backward, Gorie and pilot Gregory Johnson plan to fire Endeavour's twin braking rockets for two minutes and 51 seconds starting at 5:58:14 p.m., slowing the ship by about 209 mph and dropping it out of orbit.

Sailing northward over Central America just west of the Panama Canal, the shuttle's flight path will carry it high above central Cuba and then up the east coast of Florida before a left overhead turn to line up on runway 15. Touchdown is expected at 7:05:08 p.m.

Jones said one of the shuttle's three hydraulic power units appears to be suffering a slight decrease in fuel pressure, but telemetry indicates the problem is a slow nitrogen leak, which poses no problem for the auxiliary power unit in question.

"We started APU 1 during FCS (flight control system) checkout," Jones said. "As you know, we have been monitoring a small, slight fuel tank pressure decrease for many days now. ... They determined that this leak behaved and looked like a gaseous nitrogen leak. We started that APU today to go through FCS checkout so that we could essentially get a warm fuzzy that it is behaving exactly like we had intended. And sure enough, APU 1 did just great and there's nothing that would tell me or the flight control team that that APU is not ready for entry. Because it is."

The astronauts also tested Endeavour's re-entry software, known as "OPS-3."

"We got into that mode for a specific reason, so that we could look at the GPS system," Jones said. "This vehicle, the Endeavour, is a three-string GPS vehicle. It's the only one in our fleet and we are going to use that system to come home tomorrow. GPS is one of our primary navigation aids. That system also did very well."

Endeavour's primary steering thrusters also were test fired and again, no problems were uncovered.

But engineers were notified of an orbital debris impact on one of the shuttle's cockpit windows. The ding is about the size of a BB, but Jones said an engineering analysis shows the multi-pane window has plenty of margin for entry.

"We've seen these dings before that have happened throughout the course of our shuttle history," he said. "This ding was looked at today by our engineering community. It's about one eighth to about three sixteenths of an inch in diameter, so it's very small. But our engineers did look at it, it's cleared for entry and we have plenty of margin in that window."

Gorie and Johnson took turns practicing landing procedures using a computer flight simulator. While Endeavour is healthy and checked out for entry, Gorie told a reporter he still gets butterflies thinking about his responsibilities.

"The orbiter's really been performing really marvelously this whole flight, we don't have any concerns at all about it," he said. "We were just talking a little bit ago when Box (Johnson) and I were working the little trainer for the landing. You always have a little butterflies when you approach an event like that. We're certainly not scared about it, but yeah, you're a little bit nervous about wanting to do it just right and just like you've been training for. But Endeavour's in great shape and we're looking forward to getting back into Florida right before sunset tomorrow."

Because of the favorable weather forecast, NASA is not staffing its backup landing site at Edwards Air Force Base, Calif. Endeavour's crew will have two opportunities, on successive orbits, to land in Florida at 7:05 p.m. and 8:39 p.m. respectively. If the weather or some other problem blocks both opportunities, the astronauts will remain in orbit an extra day and try again Thursday. The shuttle has enough on-board supplies to stay in orbit until Friday.

Here is a timeline of re-entry events (in EDT throughout; best viewed with a fixed-width font):

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

..............Rev. 248 descent to KSC runway 15

01:58:00 PM...Begin deorbit timeline
02:13:00 PM...Radiator stow
02:23:00 PM...Mission specialists seat installation
02:29:00 PM...Computers set for deorbit prep
02:33:00 PM...Hydraulic system configuration
02:58:00 PM...Flash evaporator cooling system checkout
03:04:00 PM...Final payload deactivation
03:18:00 PM...Payload bay doors closed
03:28:00 PM...Mission control 'go' for OPS-3 entry software load
03:38:00 PM...OPS-3 software loaded
04:03:00 PM...Entry switchlist verification
04:13:00 PM...Deorbit maneuver update
04:18:00 PM...Crew entry review
04:33:00 PM...Commander/pilot don entry suits
04:50:00 PM...Inertial Measurement Unit alignment
04:58:00 PM...CDR/PLT strap in; mission specialists don suits
05:15:00 PM...Shuttle steering check
05:18:00 PM...Hydraulic power system prestart
05:25:00 PM...Toilet deactivation
05:33:00 PM...Vent doors closed for entry
05:38:00 PM...Mission control 'go' for deorbit burn
05:44:00 PM...MS seat ingress
05:53:00 PM...Single APU start

05:58:14 PM...Deorbit ignition
(Alt: 215.2 sm; Vel: 17,251 mph; dV: 209 mph; dT: 2:51)
06:01:05 PM...Deorbit burn complete

06:33:06 PM...Entry interface
(alt: 75.7 sm; Vel: 16,979 mph; range: 4,959 sm)
06:38:03 PM...1st roll command to left
06:52:00 PM...C-band radar acquisition
06:54:34 PM...1st left to right roll reversal
06:58:36 PM...Velocity less than mach 2.5
(alt: 83,000 ft; vel: 1,709 mph)
07:00:47 PM...Velocity less than mach 1
(alt: 51,100 ft; vel: 613 mph)
07:02:05 PM...Shuttle on the heading alignment cylinder
07:05:08 PM...Landing


..............Rev. 249 descent to KSC runway 15

07:13:14 PM...Mission control 'go' for deorbit burn
07:19:14 PM...MS seat ingress
07:28:14 PM...Single APU start

07:33:14 PM...Deorbit ignition
(alt: 216 sm; vel: 17,251 mph; dV: 206 mph; dT: 2:48)
07:36:02 PM...Deorbit burn complete

08:07:23 PM...Entry interface
(alt: 75.6 sm; vel: 16,979 mph; range: 5,055 sm)
08:12:18 PM...1st roll command to right
08:21:14 PM...1st right-to-left roll reversal
08:26:00 PM...C-band radar acquisition
08:32:34 PM...Velocity less than mach 2.5
(alt: 83,900 feet; vel: 1,704 mph)
08:34:46 PM...Velocity less than mach 1
(alt: 50,700 feet; vel: 613 mph)
08:35:32 PM...Shuttle on the heading alignment cylinder
08:39:06 PM...Landing

Additional coverage for subscribers:
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VIDEO: CLOSEUP VIEW OF THE 'REPAIRED' SHUTTLE TILES PLAY
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VIDEO: TILE REPAIR DRY RUN PRACTICE WITH THE DISPENSER PLAY
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VIDEO: NARRATED ANIMATION OF DEXTRE'S RELOCATION PLAY

VIDEO: THE FLIGHT DAY 8 HIGHLIGHTS MOVIE PLAY
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VIDEO: DEXTRE ROBOT FREED FROM LAUNCH PALLET PLAY
VIDEO: SECOND SPARE DCSU BOX PLACED ON THE STATION PLAY
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VIDEO: FIRST SPARE DCSU BOX PLACED ON THE STATION PLAY
VIDEO: SPARE YAW JOINT FOR STATION ARM TRANSFERRED PLAY
VIDEO: MOUNTING PLATE ATTACHED TO COLUMBUS PLAY
VIDEO: DEXTRE ROBOT FITTED WITH TOOL HOLDER PLAY
VIDEO: TOOL PLATFORM ATTACHED TO DEXTRE PLAY
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VIDEO: THE FLIGHT DAY 5 HIGHLIGHTS MOVIE PLAY
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VIDEO: THURSDAY'S MISSION STATUS BRIEFING PLAY
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VIDEO: LAUNCH REPLAY: CAMERA CS-6 PLAY

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VIDEO: ENDEAVOUR'S CREW MODULE CLOSED FOR FLIGHT PLAY
VIDEO: ASTRONAUT DOI CLIMBS INTO HIS SEAT PLAY
VIDEO: PILOT JOHNSON CLIMBS INTO HIS SEAT PLAY
VIDEO: ASTRONAUT REISMAN CLIMBS INTO HIS SEAT PLAY
VIDEO: COMMANDER GORIE CLIMBS INTO HIS SEAT PLAY
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VIDEO: CREW DEPARTS QUARTERS FOR LAUNCH PAD PLAY
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VIDEO: PAD GANTRY RETRACTED FOR LAUNCH PLAY

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