The shuttle Atlantis is in good shape and ready for re-entry and landing Wednesday, entry Flight Director Tony Ceccacci told reporters Tuesday. While a marginal "50-50" forecast raises the possibility of a waveoff, Ceccacci said conditions are expected to improve as the week wears on.

Credit: NASA

"Basically, there's a chance of showers within a 30-mile circle," Ceccacci said. "You all know it's KSC, so it's a 50-50 chance no matter what the forecast says.

"One of the good things is, we've been watching the trends for a while and they're trending favorably. So our hope is when we come in tomorrow morning, things will still be trending in a good direction and we won't have to work it that hard. But again, it's KSC and we'll get what we get when we get there in the morning.

Assuming the weather cooperates, commander Kenneth Ham and pilot Dominic "Tony" Antonelli will fire Atlantis' twin braking rockets for three minutes and 10 seconds starting at 7:41:49 a.m. EDT, slowing the ship by about 233 mph to drop it out of orbit.

After a half-hour free fall, Atlantis will enter the discernible atmosphere over the south Pacific Ocean around 8:16 a.m., cross high above Central America and Cuba and then descend up the Florida peninsula to a landing on runway 33 at the Kennedy Space Center. Touchdown is expected around 8:48:14 a.m.

A second landing opportunity is available one orbit later, with a deorbit burn at 9:17:24 a.m. and landing around 10:22:58 a.m. Two more Florida opportunities are available Thursday, the first at 9:13 a.m. and the second at 10:48 a.m.

The Atlantis astronauts have enough on-board supplies to remain in orbit until Saturday in a worst-case scenario. But the final day is normally reserved to handle technical problems, not the weather. As a result, NASA's backup landing site at Edwards Air Force Base, Calif., will be staffed for a possible landing on Friday if Atlantis hasn't made it back to Florida by then.

"As far as the landing strategy, with the end-of-mission-plus-three (consumables) and the current forecast, tomorrow we'll be trying KSC only and if for some reason we have to wave off, the plan is KSC only on Thursday," Ceccacci said.

The forecast for Wednesday at the Kennedy Space Center calls for a chance of showers within 30 nautical miles of the shuttle runway - a violation of NASA's flight rules - scattered clouds at 3,000 feet and broken decks at 10,000 feet and 25,000 feet. Winds are expected out of the northwest, right down the runway, at 12 knots with gusts to 18.

The forecast for Thursday calls for a chance of showers within NASA's safety zone, but lighter winds and less cloud cover. By Friday, conditions are expected to be acceptable at both Kennedy and Edwards.

Here are timelines for both Wednesday landing opportunities at the Kennedy Space Center (in EDT; best viewed with fixed-width font):

Opportunity No. 1: Rev. 186 Deorbit to KSC

Deorbit ignition: 07:41:49 AM (dV: 233 mph; dT: 3:10)
Crossrange: 679 miles
Range from atmospheric entry to KSC: 5,021 miles
Turn angle: 317-degree right turn to runway 33
Landing: 08:48:14 AM

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

12:20 AM......Crew wakeup
03:41 AM......Begin deorbit timeline
03:56 AM......Radiator stow
04:06 AM......Mission specialists seat installation
04:12 AM......Computers set for deorbit prep
04:16 AM......Hydraulic system configuration
04:41 AM......Flash evaporator cooling system checkout
04:47 AM......Final payload deactivation
05:01 AM......Payload bay doors closed
05:11 AM......Mission control 'go' for OPS-3
05:21 AM......OPS-3 entry software transition
05:46 AM......Entry switch list verification
05:56 AM......Deorbit maneuver update
06:01 AM......Crew entry review
06:16 AM......Commander, pilot don entry suits
06:33 AM......Inertial measurement unit alignment
06:41 AM......Commander, pilot strap in; others don suits
06:58 AM......Shuttle steering check
07:01 AM......Hydraulic system prestart
07:08 AM......Toilet deactivation

07:21 AM......Mission control 'go' for deorbit burn
07:27 AM......Astronauts strap in
07:36 AM......Single hydraulic power unit start

07:41:49 AM...Deorbit ignition
07:44:59 AM...Deorbit burn complete

08:16:28 AM...Entry interface
08:21:26 AM...1st roll command to left
08:34:47 AM...1st roll left to right
08:35:14 AM...C-band radar acquisition
08:41:43 AM...Velocity less than mach 2.5
08:43:56 AM...Velocity less than mach 1
08:44:09 AM...Right turn to runway 33
08:48:14 AM...Landing

------------------------------------------

Opportunity No. 2: Rev. 187 Deorbit to KSC

Deorbit ignition: 09:17:24 AM (dV: 233 mph; dT: 3:10)
Crossrange: 360 miles
Range from atmospheric entry to KSC: 5,055 miles
Turn angle: 280-degree right turn to runway 33
Landing: 10:22:58 AM

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

08:57 AM......MCC 'go' for deorbit burn
09:03 AM......MS seat ingress
09:12 AM......Single APU start

09:17:24 AM...Deorbit ignition
09:20:34 AM...Deorbit burn complete

09:51:15 AM...Entry interface
09:56:11 AM...1st roll command to right
10:06:31 AM...1st right to left roll reversal
10:09:58 AM...C-band radar acquisition
10:16:28 AM...Velocity less than mach 2.5
10:18:41 AM...Velocity less than mach 1
10:19:12 AM...Right turn to runway 33
10:22:58 AM...Landing

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