The shuttle Atlantis' countdown is back on track today after delays Friday because of stormy weather. More afternoon storms are expected today and again tomorrow, prompting forecasters to predict a 60 percent chance of weather that would block the shuttle's planned 4:30 p.m. Sunday launch on a space station assembly mission.

Shuttle weather officer Kathy Winters said a high pressure ridge has not moved north as fast as expected, resulting in sea breeze-driven afternoon storms along Florida's coast. If the ridge moves far enough north, prevailing winds will tend to drive those storms inland but it's too soon to say whether Atlantis's crew will catch a break Sunday.

The outlook for Monday and Tuesday is 80 percent "go."

NASA test director Jeff Spaulding said the launch team completed work to load the shuttle's fuel cell system Friday night, getting the countdown back on track after the work was interrupted earlier in the day. There are no other technical problems at pad 39B, although engineers were still checking various shuttle and launch pad systems after a lightning strike Friday.

"We did have a lightning strike to our pad lightning protection system yesterday," Spaulding said. "We have been performing a number of evaluations and walkdowns. Those evaluations are ongoing and engineers are still evaluating whether there's any additional work that will be required. So far, it looks favorable."

In the Caribbean, meanwhile, tropical storm Ernesto continues to develop and the National Hurricane Center predicts it will be a full-fledged hurricaine by Monday morning. The storm's track currently takes it into the central Gulf of Mexico, but it's too soon to say what impact, if any, it might have on shuttle operations in Florida or Texas.

NASA managers will review the weather outlook and the shuttle's launch processing during a L-minus one-day meeting starting at 1 p.m.

"In summary, Atlantis, her crew and payload have been waiting nearly four years for this opportunity to fly," Spaulding said. "I'm pleased to announce the vehicle, the launch team and hopefully the weather are ready for tomorrow's launch."

Here is the remainder of the STS-115 countdown. Note that all events up to and including the start of the final hold at the T-minus nine-minute mark are targeted to the opening of the shuttle's 10-minute launch window, typically five minutes earlier than the planned launch time. For countdown calculations, NASA rounds the window open time down to the nearest minute. The release of the final T-minus nine-minute hold, however, is targeted to the actual in-plane launch time, roughly the moment when Earth's rotation carries the launch pad into the plane of the international space station's orbit. All times in EDT.

EDT                             EVENT
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SATURDAY

10:00:00 AM             Begin 13-hour 34-minute hold
12:20:00 PM             JSC flight control team on station
01:30:00 PM             Communications system activation
02:00:00 PM             Crew module voice checks
03:10:00 PM             Flight crew equipment late stow
07:00:00 PM             Rotating service structure moved to park position
09:00:00 PM             Ascent switch list
11:34:00 PM             Resume countdown
11:34:00 PM             Terminate pad tours
11:49:00 PM             APU bite test
11:54:00 PM             Pad clear of non-essential personnel

SUNDAY

12:44:00 AM             Fuel cell activation
01:34:00 AM             MCC-Houston in launch comm configuration
02:04:00 AM             Booster joint heater activation
02:34:00 AM             Final fueling preps; launch area clear
04:34:00 AM             Begin 2-hour built-in hold (T-minus 6 hours)
05:24:00 AM             Mission management team tanking meeting
06:04:00 AM             External tank ready for fueling
06:34:00 AM             Resume countdown (T-minus 6 hours)
06:34:00 AM             LO2, LH2 transfer line chilldown
06:44:00 AM             Main propulsion system chill down
06:44:00 AM             LH2 slow fill
07:04:00 AM             LO2 slow fill
07:24:00 AM             LO2 fast fill
07:34:00 AM             LH2 fast fill
08:49:00 AM             LH2 topping
09:29:00 AM             LH2 replenish
09:34:00 AM             LO2 replenish; fueling complete
09:34:00 AM             Begin 3-hour built-in hold (T-minus 3 hours)
09:34:00 AM             Closeout crew to white room
09:34:00 AM             External tank in stable replenish mode
09:49:00 AM             Astronaut support personnel comm checks
10:19:00 AM             Pre-ingress switch reconfig
10:30:00 AM             NASA television coverage begins
10:55:00 AM             Astronaut breakfast photo op
12:00:00 PM             Crew weather briefing
12:10:00 PM             Astronauts don pressure suits
12:34:00 PM             Resume countdown (T-minus 3 hours)
12:40:00 PM             Crew departs O&C building
01:10:00 PM             Crew ingress
01:59:00 PM             Astronaut comm checks
02:24:00 PM             Hatch closure
02:59:00 PM             White room closeout
03:14:00 PM             Begin 10-minute built-in hold (T-minus 20m)
03:16:00 PM             NASA test director countdown briefing
03:24:00 PM             Resume countdown (T-minus 20m)
03:25:00 PM             Backup flight computer to OPS 1
03:29:00 PM             KSC area clear to launch
03:35:00 PM             Begin final built-in hold (T-minus 9m)
03:45:57 PM             NTD launch status verification
04:20:57 PM             Resume countdown (T-minus 9m)
04:22:27 PM             Orbiter access arm retraction
04:24:00 PM             Launch window opens (actual: 4:24:57 p.m.)
04:24:57 PM             Hydraulic power system (APU) start
04:25:02 PM             Terminate liquid oxygen replenish
04:25:57 PM             Purge sequence 4 hydraulic test
04:25:57 PM             Inertial measurement units to inertial
04:26:02 PM             Aerosurface profile
04:26:27 PM             Main engine steering test
04:27:02 PM             Liquid oxygen tank pressurization
04:27:22 PM             Fuel cells to internal reactants
04:27:27 PM             Clear caution-and-warning memory
04:27:57 PM             Crew closes visors
04:28:00 PM             Liquid hydrogen tank pressurization
04:29:07 PM             Booster joint heater deactivation
04:29:26 PM             Shuttle computers take control of countdown
04:29:36 PM             Booster steering test
04:29:50 PM             Main engine start (T-6.6 seconds)
04:29:57 PM             Booster ignition and liftoff

Additional coverage for subscribers:
VIDEO: PRE-LAUNCH NEWS CONFERENCE PLAY
VIDEO: FRIDAY'S COUNTDOWN STATUS DIAL-UP | BROADBAND
VIDEO: CREW ARRIVES FOR LAUNCH PLAY
VIDEO: THURSDAY'S COUNTDOWN STATUS DIAL-UP | BROADBAND

VIDEO: LAUNCH DATE ANNOUNCEMENT NEWS CONFERENCE PLAY
VIDEO: COMPLETE PREVIEW OF ATLANTIS MISSION PLAY
VIDEO: DETAILS OF THE THREE SPACEWALKS PLAY
VIDEO: MEET THE SIX ASTRONAUTS PLAY

VIDEO: CREW LAUNCH PAD PRESS CHAT DIAL-UP | BROADBAND
VIDEO: ATLANTIS ARRIVES AT LAUNCH PAD 39B PLAY
VIDEO: ROLLOUT FROM VEHICLE ASSEMBLY BUILDING BEGINS PLAY
VIDEO: TRUSS IN PAD'S PAYLOAD ROOM PLAY
VIDEO: PAYLOAD HOISTED INTO THE PAD PLAY
VIDEO: STATION TRUSS PAYLOAD DELIVERED TO PAD PLAY
MORE: STS-115 VIDEO COVERAGE
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