T-43 hours and counting...

NASA's countdown to Atlantis' final launch and the last liftoff of the 30 year space shuttle program began at 1 p.m. EDT Tuesday, picking up at the T-43 hour mark.

"I can't think of a better way to start off the week," said Jeremy Graeber, NASA test director, at a media briefing held Tuesday morning. "Fourth of July on Monday, and the start of the STS-135 launch countdown today, followed up by the launch on Friday."

Launch teams are currently not working any issues that would delay the scheduled liftoff on Friday, July 8 at 11:26 a.m.

Despite this being the final time a countdown will lead to a space shuttle launch, Graeber told collectSPACE there has been no time allocated for pomp and circumstance.

"The great thing about putting together a launch countdown schedule is that you account for every single second and every job you need to accomplish," he said. "All of that work takes up all the time we account for in the launch countdown, so we are going to treat this launch exactly the way we have treated every launch up to this point."

"But I'm sure a lot of folks will be marking those milestones in their head as it's very exciting times, but we don't specifically plan milestones [to be] called out during the launch countdown."

Technicians at Pad 39A are preparing to load the power reactant storage device (PRSD), the subsystem that stores the cryogenic hydrogen and oxygen for the shuttle's three electricity-producing fuel cells.

The current weather forecast calls for a 40 percent chance of acceptable conditions at launch time.

"I wish I had better weather for you," said Kathy Winters, shuttle weather officer. "Right now, we are going with a 60 percent chance of [Kennedy Space Center] weather prohibiting launch due to the potential for showers and isolated thunderstorms in the area."

Weather conditions are expected to improve over Saturday and Sunday, if needed.

The four STS-135 crew members celebrated Independence Day by flying from Houston to Florida on Monday.

"I think I speak for the whole crew that we are just delighted to be here. After a very arduous nine month training flow, we're thrilled being here for launch week," said STS-135 commander Chris Ferguson.

The STS-135 astronauts arrived in Florida on the Fourth of July. Credit: collectSPACE

T-21 hours and counting...

NASA's shuttle mission management team met Wednesday morning, but had little other than the worsening weather to discuss.

"We had a really smooth mission management team meeting," said Mike Moses, the team chair and shuttle integration manager. "Nobody has any issues that are in work."

Despite the weather forecast downgrading to just a 30 percent chance of acceptable conditions at launch time, liftoff of Atlantis on the final space shuttle mission remains set for 11:26 a.m. EDT on Friday (July 8).

"The folks at the rental car places at the airport telling everybody we've already scrubbed because the weather forecast was bad," said Moses. "We don't do that, not until we get a little closer, and we don't hope to do that at all this time around."

Shuttle weather officer Kathy Winters isn't optimistic.

"It is not looking favorable right now for launch," said Winters. "We have a tropical wave that is out in the Caribbean... it's actually in the Bahamas now. That wave is actually going to come into Florida along with a lot of tropical moisture that's down to the south, and it's all going to roll into Florida in the next couple of days."

"Yesterday, I kind of thought maybe we'd have some decent conditions along the coast when it came to seeing the vehicle if we were able to get 'green' for launch. In reality, it looks like... we are going to have some showers and even potentially some thunderstorms in the area by launch time," said Winters.

Based on these conditions, Winters predicted an 80 percent chance of poor weather preventing tanking operations, with a 70 percent chance of it standing in the way of launch on Friday. The forecast for the following days improves to 60 percent no-go Saturday and 40 percent on Sunday.

"We still do have a lot of moisture in the atmosphere over the next few days, so it is certainly not 'clean and green' — but it does seem to be improving," said Winters.

Meanwhile, shuttle technicians at Pad 39A continue preparing for launch.

"The countdown so far is going extremely well," said launch director Mike Leinbach. "We're into the loading of the fuel cell system, and that's the liquid oxygen and liquid hydrogen that powers those fuel cells."

"That should be done around dinner time this evening. We'll deconfigure from that and get into other launch pad preparations," said Leinbach.

T-11 hours and holding...

With thunder booming over the Kennedy Space Center and rain falling at Launch Pad 39A, space shuttle technicians have been in a hold pattern waiting for the threat from lightning to pass so they can finish their work preparing to reveal space shuttle Atlantis for launch.

A "Phase 2 Lightning Warning" was lifted at about 1:20 p.m. EDT but not before a possible lightning strike was recorded within a third of a mile of the launch pad. The effects from that strike, if any, were being assessed.

In what was ultimately a failed attempt to get ahead of the weather, the roll back of the pad's rotating service structure (RSS) was re-targeted to begin at noon EDT, two hours earlier than originally planned. A new start time has not yet been set.

The structure envelops the shuttle as it is prepared for launch, protecting the orbiter and providing access to its payload bay.

NASA has until 7:00 p.m. EDT to retract the RSS before they would face having to scrub Friday's launch attempt, set for 11:26 a.m.

At a media briefing held Thursday morning, shuttle weather officer Kathy Winters said that the weather forecast for Friday's launch time remains unchanged, with a 30 percent chance of favorable weather. The forecast is a more favorable 80 percent for fueling Atlantis' external tank, which is scheduled to begin at 1:30 a.m.

Before the thunderstorms rolled in, preparations for the final shuttle liftoff were proceeding as scheduled.

"Our last couple of days out at the launch pad have gone extremely well. We've gotten a lot of work done and we're proceeding on the timeline as we had hoped. We're working toward tomorrow's launch," Jeff Spaulding, NASA test director, said during a Thursday morning press briefing.

"We did finish fuel cell reactant loading last night on time as planned," he said. "We also finished our main engine final preps and checkouts and all those went very well. And we're just finishing up our final inspections on the external tank and solid rocket boosters as we make sure those are configured and ready for flight."

At 5 a.m. this morning, the countdown entered a planned hold at the T-11 hour mark, and will resume counting at 7:01 p.m. EDT tonight.

T-10 hours and counting...

Space shuttle Atlantis was revealed atop its launch pad Wednesday after nearly a three hour delay as NASA waited for thunderstorms to clear.

Two lightning strikes in close proximity to Kennedy Space Center's Pad 39A — one of them hitting a water tower just 515 feet from the vehicle — left Atlantis unscathed but NASA convened an engineering review board to verify that the shuttle's systems were not affected.

After completing their review, the engineering board found no indications of issues with any systems, including Atlantis, its external fuel tank and solid rocket boosters, or their ground support equipment.

Teams began retraction of the Pad 39A's rotating service structure (RSS) to reveal Atlantis at 2:45 p.m. EDT. It was fully open at 3:16 p.m.

The rotating service structure enveloped the shuttle as it was readied for launch, protecting the orbiter and providing access to its payload bay.

The retraction was required before Atlantis' external tank could be fueled for flight, scheduled to begin at 2:01 a.m. Friday. Managers will meet at 1:30 a.m. to review the weather conditions for tanking.

The final launch of the space shuttle program remains set for 11:26 a.m. EDT on Friday. The weather forecast for launch time calls for just a 30 percent chance of acceptable conditions.

Photo Gallery: Atlantis revealed for final space shuttle flight


Space shuttle Atlantis stands poised on Launch Pad 39A. Credit: collectSPACE

T-6 hours and counting...

Fueling of space shuttle Atlantis' external tank with 535,000 gallons of liquid oxygen and hydrogen is now underway.

Space shuttle mission managers met at 1:30 a.m. EDT and gave a "go" to begin loading Atlantis' external fuel tank with its super-cold cryogenic propellants. The operation began on time at 2:01 a.m. EDT and will take approximately three hours.

The first phase of the fueling is called "slow fill" to allow the pumps, lines and tank to condition themselves to the super cold chemicals. The liquid oxygen is at minus-297 degrees Fahrenheit and the liquid hydrogen is at minus 423 degrees F.

The weather forecast calls for a 30 percent chance of favorable weather for launch. The primary concern is for showers and thunderstorms, flight through precipitation, and cumulus clouds.

Teams are not working any issues that would delay today's liftoff, which is targeted for 11:26:46 a.m. EDT (1526 GMT).

The STS-135 astronauts are scheduled to wake up at 4:30 a.m.

T-3 hours and holding...

Atlantis' external fuel tank has now been filled with more than 535,000 gallons of liquid hydrogen and liquid oxygen.

"Fast fill" of the tank began at 2:51 a.m. EDT with liquid hydrogen and one minute later for the liquid oxygen. Fueling reached "stable replenish" of both cryogenic propellants at 4:58 a.m. EDT. Liquid hydrogen (LH2) "topping" began at 4:02 a.m.

The three-hour tanking process, which began at 2:01 a.m. EDT, provides the fuel and oxidizer that Atlantis' three main engines need for the eight and a half minute climb into orbit, scheduled to begin with a liftoff at 11:26 a.m. EDT.

There are no technical issues being worked for launch.

Forecasters predict a 30 percent chance of favorable weather for launch. The concern is for showers and thunderstorms in the vicinity of Pad 39A.

The countdown entered a planned hold at the T-3 hour mark at 5:01 a.m., and will resume counting at 7:31 a.m. EDT.

T-1 hour and counting...

The STS-135 astronauts left their crew quarters to depart for Launch Pad 39A at 7:36 a.m. EDT, riding the "AstroVan," a modified Airstream trailer.

Commander Chris Ferguson, pilot Doug Hurley, and mission specialists Sandy Magnus and Rex Walheim boarded Atlantis and were strapped into their seats on the flight deck.

The STS-135 astronauts are the first four member space shuttle crew to fly since STS-6 in April 1983.

With all the crew members onboard, the closeout crew sealed Atlantis' hatch, pressurized the crew cabin, checked for leaks, and then finished up their work inside the White Room prior to leaving the pad.

The STS-135 crew depart for Launch Pad 39A and space shuttle Atlantis. Credit: collectSPACE

T-9 minutes and counting...

Launch director Mike Leinbach has given Atlantis' crew the "go" after a final "go-no go" poll of the launch team to begin the STS-135 mission at 11:26:46 a.m. EDT.

During the last few minutes remaining in the countdown, the access arm on the rotating service structure will swing away from the shuttle and the vent hood, called the beanie cap, covering the point of the external tank will be lifted up and away.

A computer, called the ground launch sequencer, has taken over all the operations on Pad 39A and will be giving the commands that will launch Atlantis.