If shuttle Atlantis weathers tropical storm Ernesto without any major problems, and if engineers can complete hurried preparations, NASA may be ready to make a launch attempt as early as Sept. 6, one day before the shuttle's launch window closes, officials said late today.

Launch Director Mike Leinbach said earlier that if the shuttle was moved from its launch pad, it would take eight days to ready the ship for takeoff from the point it was returned to the firing stand.

"If we were in the VAB (vehicle Assembly Building) and had to roll out to the pad to get to our first launch attempt, that was eight days," he said. "We'll already be at the launch pad, that saves a half day right there. We'll also kick off as much of the launch pad connections as we can get done tonight, that saves more time.

"Any kind of launch dates are predicated on how long we'll be cleared from the space center (because of Ernesto)," he added. "We're assuming it'll only be tomorrow afternoon and tomorrow evening and we should be able to get back into the space center Thursday. If that's the case, the plan rolls out to an attempt September the sixth or September the seventh. We're finalizing that now, we do not have a firm date. But it's in the sixth/seventh kind of time frame."

Leinbach and other senior managers decided early today to move Atlantis off the launch pad and back to the VAB because of concern about high winds from Ernesto. At the time, forecasters were predicting sustained winds of 50 knots as the storm passed by the Kennedy Space Center with gusts to 65 knots.

NASA's launch pad safety limit is 70 knots and shuttle managers, deciding it was too close to call, erred on the side of caution and ordered engineers to start moving Atlantis off the pad. The 4.2-mile trip began at 10:04 a.m. and was expected to take about 10 hours to complete.

But later in the day, the forecast changed. While south Florida was expected to get hit by 55-knot winds and gusts up to near hurricane strength, the space center was expected to see 45-knot winds with gusts to 55 Wednesday night, well below the launch pad's 70-knot limit.

After discussing the weather with forecasters and other senior managers, Leinbach and LeRoy Cain, chairman of NASA's Mission Management Team, ordered an unprecedented rollback reversal. At 2:45 p.m., NASA's ponderous crawler-transporter began creeping back toward the pad. If all goes well, Atlantis and its mobile launch platform will be "hard down" at the pad shortly after 8 p.m. A massive rotating service structure will be moved into place around the shuttle shortly thereafter and wind screens will be extended.

The wind screens and the RSS virtually surround the space shuttle at the pad, protecting the orbiter from wind-borne debris and rain. A lightning protection system shields the orbiter from electrical activity. The external fuel tank, at least the side away from the shuttle, is pretty much exposed to the elements.

"We followed the data, we met our criteria and I feel very good about the decision," Leinbach said. "There's no trepidation in my mind at all about the decision. This is the right way to go. It was a good exercise in time, we protected both options."

It remains to be seen whether NASA can, in fact, ready Atlantis for a launch attempt as early as Sept. 6. If so, a standard three-day countdown would begin this Sunday afternoon and engineers would begin pumping hydrogen and oxygen rocket fuel into the shuttle's external tank around 2:30 a.m. next Wednesday for a launch attempt at 12:29 p.m.

"The plan to get back to a launch attempt once we return from the storm is really very straight forward," Leinbach said. "We'll go through a launch pad validation process, that's about a day-long test or so, that's where we do all the connections, data, power and gases, connections from the launch pad to the mobile launch platform. We will be opening the payload bay doors and giving our payload friends a battery boost.

"Then on day two, we will reconnect our ordnance, we need to pressurize our MPS (main propulsion system) and our RCS (reaction control system) tanks. We depressurized those for the roll back, so we'll repressurize those. Then we'll get into our launch countdown. It's going to be a full three-day standard launch countdown."

Pad processing will not take as long as usual because many tasks have already been completed. Rocket fuel for the shuttle's maneuvering jets is already on board, the payload - a new solar array truss for the international space station - is already in the cargo bay and the crew has already completed a dress-rehearsal countdown.

"So those things do not have to be re-performed and that saves us a heck of a lot of time," Leinbach said. "So the short answer is, I feel good about it. I can't give you a firm date yet. When we have a better plan, I'm sure we'll advertise it to you."

The current Sept. 7 end of the shuttle's launch window is the result of three factors: The need to launch into the plane of the space station's orbit; the desire to launch in daylight for photo documentation of the shuttle's heat shield and external tank; and the need to complete the docked phase of the mission before launch of a Russian Soyuz rocket carrying the station's next full-time crew.

For Atlantis to launch past Sept. 7, the Russians would have to agree to a Soyuz launch delay that, in turn, would force the outgoing crew of the station to land in pre-dawn darkness, something the Russians don't want to do.

Earlier today, Mike Suffredini, space station program manager at the Johnson Space Center in Houston, said more discussions were planned but as of today, Sept. 7 was the cutoff. Cain seemed to imply at one point that Sept. 8 might already be on the table, but that could not be confirmed.

For readers interested in a look ahead, here is the shuttle's flight plan assuming a launch at 12:29 p.m. on Sept. 6. The timing of key events will change slightly as NASA revises the shuttle's rendezvous profile and the crew's timeline between now and then, but the times below provide a ballpark look at when major activities would occur (all times in EDT and mission elapsed time):

DATE/EDT        DD  HH  MM  EVENT
___________________________________________________

09/06/06
Wed 12:29 PM    00  00  00  STS-115 Launch (flight day 1)
Wed 03:24 PM    00  02  55  Robot arm (SRMS) checkout
Wed 04:54 PM    00  04  25  External tank video downlink
Wed 06:29 PM    00  06  00  Crew sleep begins
               
09/07/06
Thu 02:29 AM    00  14  00  Crew wakeup
Thu 05:59 AM    00  17  30  Robot arm heat shield survey
Thu 05:29 PM    01  05  00  Crew sleep begins
               
09/08/06
Fri 01:29 AM    01  13  00  STS/ISS crew wakeup
Fri 08:37 AM    01  20  08  Atlantis docks with space station
Fri 11:19 AM    01  22  50  SRMS unberths P3/4 solar array truss
Fri 05:29 PM    02  05  00  STS crew sleep begins (EV1/EV2 in airlock)
               
09/09/06
Sat 01:29 AM    02  13  00  STS/ISS crew wakeup
Sat 05:09 AM    02  16  40  Solar array truss bolted in place
Sat 06:29 AM    02  18  00  EVA-1: Airlock egress; tool setup
Sat 12:49 PM    03  00  20  EVA-1: Airlock ingress/repress
Sat 05:29 PM    03  05  00  STS crew sleep begins (EV3/EV4 in airlock)
               
09/10/06
Sun 01:29 AM    03  13  00  STS/ISS crew wakeup
Sun 06:29 AM    03  18  00  EVA-2: Airlock egress; setup
Sun 12:49 PM    04  00  20  EVA-2: Airlock repressurization
Sun 05:29 PM    04  05  00  STS crew sleep begins              
Sun 08:24 PM    04  07  55  MCC: 4A solar array mast deploy (1 section)
Sun 09:54 PM    04  09  25  MCC: 2A solar array mast deploy (1 section)

09/11/06
Mon 01:29 AM    04  13  00  STS/ISS crew wakeup
Mon 05:04 AM    04  16  35  STS: 4A solar array mast to 49 percent
Mon 05:44 AM    04  17  15  STS: 4A solar array mast to 100 percent
Mon 06:44 AM    04  18  15  STS: 2A solar array mast to 49 percent
Mon 07:24 AM    04  18  55  STS: 2A solar array mast to 100 percent
Mon 05:29 PM    05  05  00  STS crew sleep begins (EV1/EV2 in airlock)
               
09/12/06
Tue 01:29 AM    05  13  00  STS/ISS crew wakeup
Tue 06:29 AM    05  18  00  EVA-3: Airlock egress/setup
Tue 12:49 PM    06  00  20  EVA-3: Airlock repressurization
Tue 05:29 PM    06  05  00  STS crew sleep begins
               
09/13/06
Wed 01:29 AM    06  13  00  STS/ISS crew wakeup
Wed 08:49 AM    06  20  20  Joint crew news conference
Wed 05:29 PM    07  05  00  STS crew sleep begins
               
09/14/06
Thu 01:29 AM    07  13  00  STS/ISS crew wakeup
Thu 10:30 AM    07  22  01  Atlantis undocks from space station
Thu 04:29 PM    08  04  00  STS/ISS crew sleep begins
               
09/15/06
Fri 12:29 AM    08  12  00  STS crew wakeup
Fri 04:29 AM    08  16  00  OBSS survey begins
Fri 03:59 PM    09  03  30  Crew sleep begins      
Fri 11:59 PM    09  11  30  Crew wakeup

09/16/06
Sat 02:34 AM    09  14  05  Cabin stow begins
Sat 03:49 AM    09  15  20  Flight control system checkout
Sat 04:59 AM    09  16  30  RCS hotfire
Sat 03:59 PM    10  03  30  Crew sleep begins              
Sat 11:59 PM    10  11  30  Crew wakeup

09/17/06
Sun 02:59 AM    10  14  30  Deorbit timeline begins
Sun 07:00 AM    10  18  31  Deorbit ignition (orbit 171)
Sun 08:03 AM    10  19  34  Landing

09/18/06
Mon 12:08 AM    Soyuz TMA-9 launch from Kazakhstan

Additional coverage for subscribers:
VIDEO: OFFICIALS EXPLAIN INITIAL SCRUB PLAY
VIDEO: SEE THE LIGHTNING STRIKE AT PAD B PLAY
VIDEO: ANOTHER VIEW OF LIGHTNING STRIKE PLAY

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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