BY JUSTIN RAY

Follow the countdown and launch of the Boeing Delta 2 rocket with the U.S. Air Force's GPS 2R-10 navigation spacecraft. Reload this page for the very latest on the mission.

0531 GMT (12:31 a.m. EST)

The launch team has computed that the full load for the first stage fuel tank is 9,995 gallons. Over 8,000 gallons are already aboard.

Once the tank is filled with 9,800 gallons, or 98 percent, the "rapid load" valve will be closed and the slower "fine load" phase will continue to top off the tank.

0526 GMT (12:26 a.m. EST)

RP-1 has been flowing for 10 minutes with no problems reported by the launch team.

The propellant will be guzzled along with liquid oxygen -- to be pumped into the rocket a little later -- by the first stage Rocketdyne RS-27A main engine and twin vernier steering thrusters during the initial four-and-a-half minutes of flight.

0521 GMT (12:21 a.m. EST)

Now five minutes into this approximate 20-minute process to load the rocket's first stage with about 10,000 gallons of refined kerosene fuel. Nearly 3,000 gallons have been loaded to this point.

0516 GMT (12:16 a.m. EST)

Fueling of the Delta 2 rocket's first stage has started for today's launch. About 10,000 gallons of a highly refined kerosene propellant, called RP-1, are being pumped into the base of the rocket from a storage tank at pad 17A.

0511 GMT (12:11 a.m. EST)

The Boeing launch team is now beginning the steps to prepare for loading the Delta 2 rocket's first stage RP-1 fuel tank. After verifying valves, sensors, flow meters and equipment are ready, the highly-refined kerosene fuel will start flowing into the vehicle.

0454 GMT (11:54 p.m. EST Sat.)

With the Terminal Count now underway, the launch team is beginning the work to turning on and configure the Delta's onboard guidance computer -- called the Redundant Inertial Flight Control Assembly, or RIFCA.

0450 GMT (11:50 p.m. EST Sat.)

The Terminal Countdown is now underway for the overnight blastoff of Boeing's Delta 2 rocket to place the U.S. Air Force's Global Positioning System 2R-10 spacecraft into orbit. Over the next three hours, the launch team will prep the rocket, payload and ground support systems for the planned 2:50 a.m. EST (0750 GMT) liftoff from pad 17A at Cape Canaveral Air Force Station in Florida.

The countdown currently stands at T-minus 150 minutes. However, there are a pair of holds -- totaling 30 minutes in duration -- planned at T-minus 20 minutes and T-minus 4 minutes. That will lead to launch at opening of the 15-minute window at 2:50 a.m.

It should be noted that there is a preliminary COLA, or Collision Avoidance period at the beginning of the window. So liftoff might be shifted a bit into the window. However, that is under review at this point. COLAs are blackout periods that prohibit liftoff for a few minutes to ensure the rocket isn't launched on a course that will take it too close to an object already in orbit.

As for the weather, it is very cold but skies are clear. There is now a 100 percent chance of favorable ground weather conditions for launch.

The Complex 17A area is verified cleared of workers. A warning horn will be sounded three times at the seaside complex as a precaution to alert any remaining personnel in the vicinity that they should leave immediately.

The pad clear status will allow the start of hazardous operations such as the pressurization of helium and nitrogen storage tanks inside the rocket's first and second stages, along with the second stage fuel and oxidizer tanks.

0443 GMT (11:43 p.m. EST Sat.)

The launch team members have been polled for a "ready" status to resume the countdown as planned at the end of this hold. Clocks will start ticking again at 11:50 p.m. EST as the Terminal Countdown begins.

0350 GMT (10:50 p.m. EST Sat.)

T-minus 150 minutes and holding. Clocks are entering a planned 60-minute built-in hold in the countdown. Holds are scheduled into the count to give workers a chance to catch up on any activities that may be running behind.

Over the next hour, the entire launch team and management will be seated at their consoles. A series of polls will be conducted to verify all is in readiness for entering Terminal Count at end of the built-in hold.

Liftoff of the Delta 2 rocket remains scheduled for the 2:50 a.m. EST -- the opening of a 15-minute launch window -- from Cape Canaveral, Florida.

0145 GMT (8:45 p.m. EST Sat.)

The mobile service tower has just been rolled away from the Delta 2 rocket at Cape Canaveral's pad 17A, a Boeing spokesman reports.

Activities at the Cape are leading up to the start of Terminal Count at 11:50 p.m. EST. That three-hour sequence will see the Delta 2 rocket fully fueled, the guidance system turned on, final system checks performed and all the other normal work to ready the vehicle for flight.

The loading of RP-1 kerosene fuel into the rocket's first stage is expected to start around 12:10 a.m. Liquid oxygen tanking will follow around 12:55 a.m. The second stage was loaded with storable propellant a few days ago and the third stage is solid-fueled.

The overnight launch window extends 15 minutes from 2:50 to 3:05 a.m. EST (0750-0805 GMT).

0125 GMT (8:25 p.m. EST Sat.)

On a very cold Florida night, Boeing and the U.S. Air Force are teamed up to launch a Delta 2 rocket and the Global Positioning System 2R-10 military navigation satellite from Cape Canaveral.

The mobile service tower is being prepared to roll away from the 126-foot tall rocket at pad 17A. The metal cocoon-like mobile service structure is used to assemble the Delta 2 on the seaside pad, as well as provide workers access to all reaches on the vehicle and weather protection for the rocket.

Crews will spend this evening performing the final chores to configure the vehicle and secure the launch complex for the overnight liftoff at 2:50 a.m. EST. A Boeing spokesman says there are currently no significant issues preventing an on-time launch.

The Terminal Countdown is scheduled to begin at 11:50 p.m. Fueling of the vehicle's first stage will follow.

FRIDAY, DECEMBER 19, 2003
2040 GMT (3:40 p.m. EST)

A Boeing Delta 2 rocket and its Global Positioning System 2R-10 satellite payload are poised for liftoff early Sunday from Cape Canaveral Air Force Station, Florida.

"At this time, there are no issues," Col. Mike Baker, the Air Force mission director, told reporters at news conference this afternoon. "The Delta 2, GPS spacecraft and Eastern Range are green and go for launch."

Sunday's 15-minute launch window opens at 2:50 a.m. EST (0750 GMT).

Meteorologists say weather conditions should permit an on-time liftoff. Very cold temperatures, around 40 degrees F, are expected at launch time, but even that won't stall the launch.

"Despite the cold weather we do anticipate this weekend, I would like to say the launch vehicle and satellite do not have cold weather constraints. So despite the fact that I do expect temperatures to be near 40 degrees F tomorrow and Sunday morning, that is not a constraint to the launch," weather officer Joel Tumbiolo said.

"Overall, I expect very good weather conditions over the next couple of days. High pressure is pretty much in control."

The Delta 2 will deliver the Air Force's next GPS satellite into space, replacing an aging craft in the orbiting network. It will be the third such launch in 2003 to sustain the GPS fleet, with four more planned next year.

"The health of the constellation is excellent. With the addition of GPS 2R-10, we will continue to provide tremendous navigation and targeting capabilities critical to our warfighters around the world," said Col. Allan Ballenger, the system program director for the NAVSTAR GPS Joint Program Office.

Backup launch opportunities are available on Monday and Tuesday, with 15-minute launch windows opening at 2:46 and 2:42 a.m. EST, respectively.

If the rocket doesn't fly during the three-day period, officials say they would plan to hold the launch until after the holidays.

"Because of the importance of the mission and the importance of allowing our folks to concentrate on the mission and concentrate on their families, we are not...anticipating trying to launch between Christmas and New Years," Col. Baker said.

Watch this page for live updates starting late Saturday as the countdown enters its final hours and throughout the launch.

1630 GMT (11:30 a.m. EST)

The launch weather forecast issued this morning still shows better than a 90 percent chance of acceptable conditions during Sunday's 2:50 to 3:05 a.m. liftoff window. See the latest forecast here.

THURSDAY, DECEMBER 18, 2003

Launch weather officer Joel Tumbiolo says conditions will be very favorable, although quite cold, for Sunday's early morning liftoff of the Delta 2 rocket carrying the next Global Positioning System satellite. See the latest forecast here.

Mission managers will hold their final launch readiness reviews on Friday. A pre-launch news conference is scheduled for early afternoon at Cape Canaveral. Watch this page for an update following the briefing, and live coverage during Sunday's countdown and flight of the Delta 2.

WEDNESDAY, DECEMBER 17, 2003

The latest weather forecast continues to predict favorable conditions for Sunday morning's launch attempt. See the full forecast here.

TUESDAY, DECEMBER 16, 2003

A replacement satellite ascends into space this weekend to strengthen the U.S. military's Global Positioning System -- a constellation of orbiting spacecraft that guides planes, ships, troops and precision weaponry.

The NAVSTAR GPS 2R-10 satellite is scheduled for liftoff at 2:50 a.m. EST (0750 GMT) Sunday atop a Boeing Delta 2 rocket from pad 17A at Cape Canaveral Air Force Station, Florida.

The day's available launch window extends a quarter-hour to 3:05 a.m. EST (0805 GMT).

Read our full launch preview story.

Meanwhile, Air Force weather forecasters are predicting near-perfect conditions on Sunday morning. See the early forecast here.