BY JUSTIN RAY

Follow the countdown and launch of the Lockheed Martin Atlas 2AS rocket with a classified National Reconnaissance Office payload. Reload this page for the very latest on the mission.

1500 GMT (11:00 a.m. EDT)

T-minus 10 minutes and counting. Coming up on the planned 15-minute built-in hold at T-minus 5 minutes. Still looking for liftoff at 1525 GMT.

Also, an inhibited self test of the rocket's Flight Termination System has been performed. The FTS would be used to destroy the vehicle in the event of a malfunction during launch.

1454 GMT (10:54 a.m. EDT)

The Air Force reports the countdown is continuing on track for liftoff today at about 1525 GMT (11:25 a.m. EDT; 8:25 a.m. PDT). There are no technical problems being addressed by the launch team.

1445 GMT (10:45 a.m. EDT)

Loading of the Atlas and Centaur stages is now completed. But as the countdown proceeds, the tanks will be replenished to replace the cryogenic liquid oxygen and liquid hydrogen that naturally boils away.

1430 GMT (10:30 a.m. EDT)

Fueling of the Atlas rocket and its Centaur upper stage is entering the final stages. The Atlas and Centaur liquid oxygen tanks are virtually full and will be topped off. The Centaur liquid hydrogen tank is nearing the 80 percent level and still climbing.

1425 GMT (10:25 a.m. EDT)

Now about one hour away from the launch of Lockheed Martin's Atlas 2AS rocket designated AC-160. Today will mark the 568th launch of an Atlas rocket; the 134th flight of a Centaur upper stage on an Atlas; the 23rd mission of an Atlas 2AS vehicle with four strap-on solid rocket motors; third Atlas launch of 2001 and the first from Vandenberg.

1419 GMT (10:19 a.m. EDT)

The liquid oxygen tank inside the Atlas booster stage is now at 70 percent. The Centaur hydrogen tank has been filled to the 10 percent level.

1414 GMT (10:14 a.m. EDT)

The liquid hydrogen chilldown is now complete and the super-cold fuel is flowing to fill the Centaur upper stage. The cryogenic propellant will be consumed with liquid oxygen by the stage's Pratt & Whitney-made RL-10 engines to propel the classified NRO cargo into the targeted orbit above Earth today.

Meanwhile, the Atlas liquid oxygen tank is 40 percent full.

And the final alignment of the Atlas rocket's inertial navigation guidance computer has been completed.

1408 GMT (10:08 a.m. EDT)

The Atlas stage liquid oxygen tank is now 10 percent full as today's fueling operations continue.

1358 GMT (9:58 a.m. EDT)

The Centaur liquid oxygen tank has reached the 95 percent full level. And now the chilldown procedure is being for loading liquid oxygen into the Atlas booster stage.

The countdown continues ticking along smoothly at Vandenberg for today's launch at approximately 1525 GMT (11:25 a.m. EDT; 8:25 a.m. PDT). There are no technical problems being reported and the weather remains favorable for this classified launch.

1350 GMT (9:50 a.m. EDT)

The chilldown conditioning of liquid hydrogen propellant lines at SLC-3E is now starting. This process is like the one performed on the liquid oxygen side whereby a small amount of the liquid is released from the pad's storage tank to prepare the plumbing for transferring the Minus-423 degree F fuel into the rocket.

1346 GMT (9:46 a.m. EDT)

The Centaur liquid oxygen tank is now half-full.

1341 GMT (9:41 a.m. EDT)

The Centaur upper stage's liquid oxygen tank is now 20 percent full in this early portion of fueling operations.

1331 GMT (9:31 a.m. EDT)

Chilldown conditioning of the liquid oxygen transfer lines has been completed and the launch team is now beginning to fill the Centaur upper stage with its its supply of super-cold cryogenic oxidizer. The liquid oxygen is chilled to Minus-298 degrees F, and will be consumed by the Centaur's twin RL-10 engines along with liquid hydrogen to be pumped into the stage a little later in the countdown.

Meanwhile, the Atlas stage's fuel tank has been pressurized for launch.

1328 GMT (9:28 a.m. EDT)

The "chilldown" procedure is starting to thermally condition the liquid oxygen propellants lines at SLC-3E in advance of loading the Centaur upper stage. Chilldown is a process in which a small amount of the super-cold liquid oxygen is released from the pad's storage tank into the feed lines that lead to the rocket.

1325 GMT (9:25 a.m. EDT)

T-minus 105 minutes and counting. The countdown is running again following the planned half-hour built-in hold. Activities remain on track for liftoff in two hours. It does appear the launch time has been adjusted by one minute -- to 1525 GMT -- over the Air Force's announced target liftoff time.

1318 GMT (9:18 a.m. EDT)

The launch team and management have been polled for a readiness to begin fueling the Atlas rocket. All parties reported "go" status. Approval was then given to start loading super-cold liquid propellants into the vehicle.

1255 GMT (8:55 a.m. EDT)

T-minus 105 minutes and holding. Clocks have entered the planned 30-minute hold at the T-minus 105 minute point in today's countdown at Vandenberg Air Force Base for launch of the Atlas 2AS rocket. Launch remains scheduled for 1524 GMT (11:24 a.m. EDT) with no problems currently threatening liftoff today.

At Space Complex Complex-3 East, the mobile service tower has been retracted and secured in its launch position.

The count has 45 minutes of built-in holds scheduled over the course the morning that will lead to liftoff. A second and final hold is planned at T-minus 5 minutes for 15 minutes. The holds are designed to give the launch team a window of time to work any problems that could arise without delaying other pre-flight preparations.

Once the resumes, the activities to load super-cold liquid oxygen and liquid hydrogen into the rocket will move into full swing.

1230 GMT (8:30 a.m. EDT)

The launch team continues clicking off steps in their checklists as the countdown rolls on at Vandenberg Air Force Base in California this morning for launch at 1524 GMT (11:24 a.m. EDT; 8:24 a.m. PDT). There are no technical problems being reported.

The launch control center is located in the Remote Launch Control Facility in Building 8510 of Vandenberg, located approximately 10 miles away the pad. There, the Lockheed Martin Astronautics Test Conductor, Mark Ware, conducts the overall Atlas launch countdown. Ware reports to the Lockheed Martin Astronautics Launch Director, Tom Heter. The Lockheed Martin launch operations team is responsible for preparation and checkout of the Atlas and Centaur stages, associated ground support equipment and SLC-3E launch complex ground support systems and participation in the launch countdown. The overall launch management is governed by Air Force, which procured this rocket.

Since this is a National Reconnaissance Office payload being lofted into orbit today, Col. Stephen Wojcicki, the NRO's Director of Launch, will make the final "go/no go" decision for liftoff in the final minutes of the countdown.

1207 GMT (8:07 a.m. EDT)

Riding on rails, the massive mobile service tower is rolling away from the Lockheed Martin Atlas rocket at the Space Launch Complex-3 East pad. Crews report the tower is now clear of the vehicle.

The tower is a vital tool in assembling the rocket on the pad. Processing for this launch began with erection of the Atlas stage on April 3, followed by the interstage and Centaur upper stage. The four strap-on solid rocket boosters were added on May 10. A countdown dress rehearsal that involved loading the rocket with propellants occurred on August 3. The date of the classified NRO payload's mating with the rocket was not released.

1155 GMT (7:55 a.m. EDT)

Good morning and welcome to our live coverage of today's launch of the Atlas 2AS rocket with a hush-hush cargo for the U.S. National Reconnaissance Office. The countdown is well underway at Vandenberg Air Force Base along California's central coast for the planned 1524 GMT (11:24 a.m. EDT; 8:24 a.m. PDT) liftoff.

At Space Launch Complex-3 East preparations are now beginning to retract the 230-foot tall mobile service tower away from the rocket. The structure is used to erect the rocket on the launch pad, provide access for workers to all areas of the vehicle and protection from the weather.

Over the past couple of hours, the launch team at Complex 36 have worked through propulsion launch preps for the Atlas and Centaur stages, closed out the thrust sections of both stages, conducted Atlas and Centaur pneumatic preps, and started the liquid oxygen and liquid hydrogen system preps.

Also, the weather continues to look favorable for launch today.

FRIDAY, SEPTEMBER 7, 2001

Officials have cleared the Lockheed Martin Atlas 2AS rocket for blastoff Saturday from Vandenberg Air Force Base in California carrying a classified National Reconnaissance Office payload. The final launch readiness meetings were held today, concluding with the decision to proceed with a 1524 GMT (11:24 a.m. EDT; 8:24 a.m. PDT) liftoff tomorrow.

Air Force meteorologists are still predicting a zero percent chance of weather prohibiting the launch. However, patchy fog and completely overcast skies could hamper viewing the liftoff for spectators.

Launch Weather Officer Dr. Christy Crosiar says there will be a deck of stratus clouds with full sky coverage from 500 to 1,200 feet. The visibility is expected to be two to four nautical miles, with northerly winds from 340 to 350 degrees at three to eight knots, a temperature of 53 to 58 degrees F and fog. Upper level winds will max out at 20 to 25 knots from the northwest at 40,000 to 45,000 feet.

Should the launch be delayed for some reason, there is again a 100 percent "go" weather forecast for Sunday and 80 percent "go" on Monday.

"Expect Sunday and Monday mornings to have similar conditions as the launch day," Crosiar said. "Stratus layer will get deeper and some drizzle Monday morning. By Monday morning expect to see some upper level clouds associated with the remains of Hurricane Henriette moving across the area. Upper level winds will increase to about 70 knots from the west at 35,000 - 40,000 feet."

Watch this page for countdown reports and complete live coverage of the launch!

THURSDAY, SEPTEMBER 6, 2001

As we reported yesterday, the planned launch time for the Atlas rocket on a classified mission for the National Reconnaissance Office is 1524 GMT (11:24 a.m. EDT; 8:24 a.m. PDT) on Saturday. The Air Force officially announced the time today as preparations entered the final 48 hours to blastoff.

The veil of secrecy shrouding this launch continues, however, as the duration of the launch window was not disclosed. However, sources say it will extend for 12 minutes to 1536 GMT (11:36 a.m. EDT; 8:36 a.m. PDT).

The weather forecast is excellent with a 100 percent chance of conditions being acceptable for liftoff on Saturday, as well as backup launch opportunities on Sunday and Monday.

"For launch Saturday morning expect an offshore flow with light and variable winds, five to eight knots, visibility three to five nautical miles with patchy fog and temperatures in the mid 50's," Launch Weather Officer Dr. Christy Crosiar says. "Maximum upper level winds will be 15 to 20 knots from the northwest at 45,000 feet."

The Launch Readiness Review is planned for Friday morning at Vandenberg when senior officials will gather to discuss preparations for liftoff and any technical concerns. At this point, there are no issues being reported.

At the Space Launch Complex-3 East pad, the rocket's Atlas stage fuel tank has been loaded with approximately 15,000 gallons of RP-1 fuel -- a highly refined kerosene. Slightly more fuel was pumped into the rocket than originally envisioned, a change that forced a two-week delay in the launch from August 25 to September 8.

During a mission review one month ago, the amount of fuel being carried on this launch was called into question. Engineers were looking at the pre-flight predictions and data for this mission and then compared that information to the historical experience gained in over 50 launches of Atlas 2 and 2AS rockets, Mike Gass, Lockheed Martin's vice president of Atlas and EELV programs, explained in a recent interview.

"Everything in our predictions and calculations in mission design were well within spec, well within our capability. But now we were asked the question 'where is it against that experience?'"

One parameter of over 1,500 examined was not in the middle of the target as officials wanted. The issue was the amount of RP-1 fuel onboard since this launch will carry the heaviest payload ever lofted by an Atlas rocket.

"When we have (Booster Engine Cutoff on the Atlas stage) we are at a 5-g acceleration. If you start with a heavy payload, the time to get to (Booster Engine Cutoff) is going to be slightly longer. We would like to have the fuel level at the (Booster Engine Cutoff) to be right there at the experience point where we have always been. And we can do that by adding more fuel."

The Atlas will deliver a critical national security payload into Earth orbit, and Lockheed Martin obviously wants to cut out any threats against mission success.

Added Gass: "Why on this mission be at a new experience point?"

By loading more propellant, the daily launch window in which to get the rocket airborne had to be shortened from about 24 minutes down to roughly 12 minutes.

"There is an optimal point in time that you launch, and on either side of that optimal point in time you are doing more steering and using more propellant," Gass said. "Instead of reserving capability for window time, we put the margin on the vehicle. You can never use margin in the window after you lift off, you would rather have the margin on the vehicle."

The time needed to validate and double-check the changes made with adding more fuel and adjusting the vehicle's propellant utilization system required the two-week launch postponement.

Spaceflight Now will provide complete live coverage of Saturday's countdown and launch. Watch this page for continuing updates!

WEDNESDAY, SEPTEMBER 5, 2001

A Lockheed Martin Atlas 2AS rocket is on track for launch Saturday from Central California to propel into space a top-secret national security payload that appears tied with the current fleet of ocean surveillance satellites orbiting the Earth. Read our full launch preview story.