BY JUSTIN RAY

July 16, 2000 -- Follow the countdown and launch of a Boeing Delta 2 rocket with the U.S. Air Force's GPS 2R-5 navigation satellite. Reload this page for the very latest on the mission.

SUNDAY, JULY 16, 2000

As a Boeing Delta 2 rocket successfully lofted a new U.S. Air Force navigation satellite on Sunday, two onboard video cameras provided dazzling views of the predawn jaunt into space. Read our full story.

1130 GMT (7:30 a.m. EDT)

The 'rocketcams' carried aboard the Boeing Delta 2 rocket has provided a stunning view what it's like to launch at night. Video cameras have been mounted on previous rockets but those launches always occurred in daylight. Check out the many QuickTime video clips posted in the right-hand side of this page from today's predawn liftoff.

Now in Earth orbit after a successful launch this morning, the Air Force's Global Positioning System 2R-5 satellite has entered a busy time to prepare it for service in one month's time.

Plans call for a Course Spin Processing Maneuver to be performed about three hours after separation from the Delta 2 rocket to align the spacecraft in the correct direction for the upcoming Apogee Kick Motor burn. That burn is expected 60 hours into the flight to push the satellite up to its required apogee altitude, basically circularizing its orbit.

The solar arrays are due to be deployed at Separation + 97 hours; followed an hour later by the start of 3-axis stabilization and Sun/Earth acquisition. At Separation + 99 Hours (approx. 35 minutes from Sun Hold Earth Search, the W-Sensor will be deployed.

At Separation + 111 Hours, the maneuver to tweak the craft's velocity will be performed so the satellite arrives at its operational location. GPS 2R-5 should be placed in the exact orbit at Separation + 327 hours.

The final software will be loaded aboard the satellite at Separation + 394 hours. Control is then handed to the 2nd Space Operations Squadron for payload initialization and checkout.

It will take about two weeks to turn on the Navigation and Nuclear Detection payloads. The onboard Atomic clocks are the first components turned on because they need time to stabilize -- about 7 to 10 days.

GPS 2R-5 should enter service in 30 to 45 days.

The Air Force will position the satellite in Plane B, Slot 5 of the GPS constellation, where it will provide precision navigation and timing information to U.S. military troops and civilians around the world. The satellite will ultimately move to another slot within Plane B to replace an aging sister-satellite when one fails.

0942 GMT (5:42 a.m. EDT)

T+plus 25 minutes, 40 seconds. SPACECRAFT SEPARATION! The NAVSTAR Global Positioning System 2R-5 military navigation satellite has been released from the Delta rocket's third stage following a successful launch this morning that began right on time.

Over the coming month, activities to prepare the satellite for service will include deploying its solar arrays in order to generate power and recharge onboard batteries, manuevers to circularize the orbital altitude and testing and of the spacecraft bus and communications payload.

Check back later this mornign for a full report on the launch, movie clips from the rocket's onboard camera and images.

0941 GMT (5:41 a.m. EDT)

T+plus 24 minutes. Boeing confirms the third stage has fired and burned out as planned. Coming up on spacecraft separation in about 90 seconds.

0940 GMT (5:40 a.m. EDT)

T+plus 23 minutes, 30 seconds. At this point in the first the third stage should been nearing the end of its firing. However, a lack of good data from the rocket is making it impossible to "see" was is happening. This is not unusual to have a noisy data.

0939 GMT (5:39 a.m. EDT)

T+plus 22 minutes, 30 seconds. Noisy data from teh rocket making it difficult to confirm any event at this point, such as stage separation and third stage ignition.

0937 GMT (5:37 a.m. EDT)

T+plus 20 minutes, 48 seconds. The Delta rocket's second stage has completed its second burn tonight to deliver the third stage and attached GPS spacecraft into the proper orbit. Coming up on second and third stage separation in less than one minute.

0935 GMT (5:35 a.m. EDT)

T+plus 18 minutes. About two minutes until the second stage engine is restarted for a 37-second firing as the GPS 2R-5 satellite continues its journey to space.

0932 GMT (5:32 a.m. EDT)

T+plus 15 minutes. Boeing reports the temporary orbit around Earth that was achieved following the first burn of the second stage is very close to perfect. The apogee is 209.82 miles, the perigee of 94.0 miles and inclination of 36.91 degrees.

0931 GMT (5:31 a.m. EDT)

T+plus 14 minutes. Nothing much to report at this point in the flight because the rocket has passed out of range from the downrange tracking station network. The next data will come in a few minutes via the Ascension Island station near the equator.

0929 GMT (5:29 a.m. EDT)

T+plus 12 minutes. The Delta rocket is now in a coast period that will last another 10 minutes before the second stage restarts. Boeing just provided a great treat -- a replay of an onboard camera. We will have QuickTime video clips shortly.

0928 GMT (5:28 a.m. EDT)

T+plus 11 minutes. SECO 1. The second stage engine has cut off as planned and the Delta 2 rocket with GPS 2R-5 spacecraft have arrive in a preliminary orbit around Earth.

0927 GMT (5:27 a.m. EDT)

T+plus 10 minutes, 30 seconds. Nearing the end of the first burn of the second stage.

0926 GMT (5:26 a.m. EDT)

T+plus 9 minutes, 30 seconds. Alitude 97 miles, downrange distance 1250, velocity 15,500 mph.

0926 GMT (5:26 a.m. EDT)

T+plus 9 minutes. Second stage engine chamber pressures looking good. Official liftoff time was 5:17:00.450 a.m. EDT.

0925 GMT (5:25 a.m. EDT)

T+plus 8 minutes. About three minutes left in the second stage burn to achieve an initial orbit around Earth. Officials report all data coming back from the Boeing Delta 2 rocket is nominal.

0924 GMT (5:24 a.m. EDT)

T+plus 7 minutes. Alitude is 88 miles, downrange distance 731, velocity 13,700 mph. The downrange Antiqua tracking station has acquired the rocket's signal.

0923 GMT (5:23 a.m. EDT)

T+plus 6 minutes, 30 seconds. The second stage engine still firing normally. Vehicle is stable.

0922 GMT (5:22 a.m. EDT)

T+plus 5 minutes, 30 seconds. Alitude is 75 miles, downrange distance 480, velocity of 13,000 mph.

0922 GMT (5:22 a.m. EDT)

T+plus 5 minutes. The protective payload fairing enclosing the GPS satellite atop the rocket has separated with no recontact detected.

0921 GMT (5:21 a.m. EDT)

T+plus 4 minutes, 45 seconds. MECO. The first stage main engine cutoff confirmed, the stage has been jettisoned and second stage engine ignition has occurred.

0921 GMT (5:21 a.m. EDT)

T+plus 4 minutes. About a half-minute left in the first stage burn. Vehicle flying right down the predicted Range track.

0920 GMT (5:20 a.m. EDT)

T+plus 3 minutes. A smooth flight continues for the Boeing Delta 2 rocket. No problems reported. The first stage main engine and twin vernier engines continue to fire.

0919 GMT (5:19 a.m. EDT)

T+plus 2 minutes, 15 seconds. The three air-start solid rocket boosters have burned out and separated. The rocket continues its trek to orbit on the power of the first stage liquid-fueled main engine.

0918 GMT (5:18 a.m. EDT)

T+plus 90 seconds. Altitude is 10 miles, downrange distance 22 miles, velocity of 2,300 mph.

0918 GMT (5:18 a.m. EDT)

T+plus 70 seconds. Separation of all six ground-start solid rocket boosters confirmed. The three air-lit solids have ignited.

0917 GMT (5:17 a.m. EDT)

T+plus 30 seconds. Vehicle performance reported normal as the rocket approaches Mach 1.

0917 GMT (5:17 a.m. EDT)

LIFTOFF! Liftoff of the Boeing Delta 2 rocket and Global Positioning System 2R-5 spacecraft -- maintaining the U.S. military's orbiting precision navigation constellation. And the vehicle has cleared the tower.

0916 GMT (5:16 a.m. EDT)

T-minus 30 seconds. Hydraulics and electronics reported go.

The launch ignition sequence will begin at T-minus 2 seconds when a Boeing engineer triggers the engine start switch. The process begins with ignition of the two vernier engines and first stage main engine start. The six ground-start solid rocket motors then light at T-0 for liftoff.

0916 GMT (5:16 a.m. EDT)

T-minus 1 minute. The Range has given its final clear-to-launch. The Delta 2 rocket's second stage hydraulic pump has gone to internal power after its pressures were verified acceptable. At the telemetry receiving areas where data from the rocket will be transmitted, the data recording charts have gone to high speed as the liftoff nears. Also, the pad 17A water suppression system has started.

0915 GMT (5:15 a.m. EDT)

T-minus 2 minutes. The first stage liquid oxygen vents are now being closed so the LOX tank can be pressurized for launch. Puffs of vapor from a relief valve on the rocket will be seen in the remainder of the countdown as the tank pressure stabilizes.

The U.S. Air Force has declared the NAVSTAR Global Positioning System 2R-5 spacecraft on internal power and officially "go" for launch this morning. The spacecraft will join 28 other operational GPS satellites in space to provide precision navigation and timing information to military forces and civilians on land, in the air and at sea around the globe. Officials are launching the craft to expand the existing constellation and have it already in space when older GPS satellite should each the end of life.

0914 GMT (5:14 a.m. EDT)

T-minus 3 minutes. The safety destruct safe and arm devices are being armed.

0913 GMT (5:13 a.m. EDT)

T-minus 4 minutes and counting. Now in the final phase of the countdown as Delta launch vehicle systems begin transferring to internal power. All systems remain ready for an on-time launch this morning at 17 minutes past the hour from pad 17A at Cape Canaveral Air Force Station in Florida.

0912 GMT (5:12 a.m. EDT)

Launch team standing by to pick up the countdown in one minute. The Delta rocket is now five minutes away from liftoff. This has been a very smooth countdown so far.

0911 GMT (5:11 a.m. EDT)

The readiness poll by the Air Force launch director just concluded and no problems were announced. Countdown clocks are scheduled to resume in two minutes for launch at 5:17 a.m. EDT.

0909 GMT (5:09 a.m. EDT)

A readiness poll of the launch team has been conducted and all parties reported "go" status for liftoff in eight minutes from Cape Canaveral Air Force Station, Florida.

0908 GMT (5:08 a.m. EDT)

Now half-way through this built-in hold. There are no problems being reported.

0903 GMT (5:03 a.m. EDT)

T-minus 4 minutes and holding. The countdown has entered the final planned hold point for tonight's launch attempt. During this planned 10-minute hold, the launch team can catch up on any work that could be running behind schedule. In addition, officials will poll the various team members to ensure all systems are ready for launch. Lt. Col. Blaise Kordell, commander of the 1st Space Launch Squadron at Cape Canaveral Air Force Station, will give the approval to launch the Delta rocket and the Air Force's NAVSTAR Global Positioning System 2R-5 satellite. At present, there are no problems being discussed. Upper level winds, ground weather, the Range, launch vehicle and payload are go for liftoff at 5:17 a.m. EDT.

0859 GMT (4:59 a.m. EDT)

The first stage fuel tank vent is being closed and the tank is being pressurized to 24 to 30 psig is being pressurized. Also, the rocket's C-band beacon used by Range Safety to track the vehicle during launch has been verified to be working properly.

0857 GMT (4:57 a.m. EDT)

T-minus 10 minutes and counting. The countdown is heading to T-minus 4 minutes for a 10-minute long hold. Liftoff the Boeing Delta 2 rocket from Cape Canaveral Air Force Station is still slated to occur at 5:17 a.m. EDT to place the NAVSTAR Global Positioning System 2R-5 satellite into space.

The Range Safety checks have been completed with no problems reported.

For these NAVSTAR GPS launches, Boeing uses a model 7925-9.5 Delta 2 rocket. The expendable launch vehicle consists of three stages, nine strap-on solid rocket boosters and a 9.5-foot diameter payload fairing. The rocket stands 126 feet tall. See our rocket fact sheet for more.

0854 GMT (4:54 a.m. EDT)

Checks are now under way of the Range Safety command destruct receivers that would be used to destroy the Delta rocket should a problem arise during the launch. A little earlier, the Range completed RF link checks with the rocket.

0852 GMT (4:52 a.m. EDT)

The trickle charge is being stopped to the Global Positioning System 2R-5 spacecraft atop the Delta rocket, and the satellite is switching to internal power for launch.

0847 GMT (4:47 a.m. EDT)

T-minus 20 minutes and counting. The countdown has resumed as scheduled from this 20-minute-long built-in hold and clocks are now ticking toward the T-minus 4 minute mark where another pause is planned. Launch remains scheduled for 5:17 a.m. EDT.

Also, the Range has reported there are no collision avoidance periods, or COLAs, this morning that would prohibit liftoff during the available launch window.

0827 GMT (4:27 a.m. EDT)

T-minus 20 minutes and holding. The countdown has gone into the first of two planned hold periods during the last 20 minutes of the terminal count for this morning's 5:17 a.m. EDT (0917 GMT) launch.

Over the past few minutes, the "slew" or steering checks of the first and second stage engines were completed and RF link tests between the Range and rocket started. There are no problems being worked with the rocket, GPS satellite cargo or Range systems. Weather is also reported to be acceptable.

Sitting atop the Delta rocket is the Lockheed Martin-built GPS 2R-5 spacecraft, which will be the 33rd operational satellite to be launched since 1989.

The Navigation Signal Timing and Ranging Global Positioning System (NAVSTAR GPS) was established in the 1970s to provide the military with navigation data for ground, sea and air forces. The first 11 satellites, known as Block 1, were launched from 1978 through 1985 and served to test the fundamentals behind the GPS concept. Beginning in 1989, the Block 2 and 2A series satellites began flying to form the current constellation that provides precise navigation data not only to the military but civilians as well.

In 1997 a newer, more advanced series of GPS satellites, the Block 2R, debuted. However, the first was lost in a launch failure. The second was successfully launched in July of that year. This morning, the fifth of 21 is scheduled to leave the Earth aboard the Delta 2 rocket. The craft are considered to be operational replenishment satellites and are developed by Lockheed Martin. They will carry GPS into the next century. Block 2R satellites are designed to provide at least 14 days of operation without contact from controllers and up to 180 days of operation when operating in the autonomous navigation (AUTONAV) mode. The spacecraft maintain their accuracy by communicating with other Block 2R satellites in orbit. This so-called cross-link ranging will be used to estimate and update the parameters in the navigation message of each Block 2R satellite without contact from ground control. Other enhancements include reprogrammable micro-processors for upgrading in-flight, additional radiation protection, greater fuel capacity, the ability to determine their own position and two atomic clocks working at all times, providing a "hot backup."

The GPS constellation is comprised of 24 primary satellites divided into six orbital planes with four spacecraft in each. They circle in formation about 10,900 nautical miles above Earth every 12 hours in orbits inclined 55 degrees to the equator.

The continuous navigation signals sent from the satellites allow users to find their position in latitude, longitude and altitude and measure time. A GPS user receiver measures the time delay for the signal to reach the receiver, which is the direct measure of the apparent range to the satellite. Measurements collected simultaneously from four satellites are processed to solve for the three dimensions of position, velocity and time. Users can determine their location to within feet, speed within a fraction of a mile per hour and time to within a millionth of a second.

Countless uses have been found for the revolutionary GPS system. Everyday, GPS guides U.S. military troops, aircraft, submarines and ships around the globe. Troops also relied on the system extensively in the featureless desert battlefield of the Gulf War. Weapons can use GPS data for guidance. GPS also found its way into the civilian commercial market - assisting planes, automobiles, boats, hikers and map makers.

SUNDAY, JULY 16, 2000
0817 GMT (4:17 a.m. EDT)

Now exactly one hour from the scheduled liftoff time for the Boeing Delta 2 rocket to place the U.S. Air Force's NAVSTAR Global Positioning System Block 2R-5 military navigation satellite into Earth orbit. The countdown continues on time and no technical problems are being reported.

Today's launch was originally targeted for June 15 but was delayed after Boeing engineers encountered an odd problem fitting together stages of the rocket atop pad 17A.

The problem was the rocket's second stage would not properly attach to the first stage. The two stages are joined together by the interstage structure -- a hollow cylinder that remains connected to the top of the first stage during launch and encloses the second stage engine.

During the first attempt to "stack" the second stage, workers noted the stage and interstage did not join together evenly across the rocket's 8-foot-wide diameter. The alignment was off by as much as three-eighths of an inch around the diameter as the top-end of the interstage was more oval than perfectly circular.

The suspect interstage was removed and replaced. However, that did not fix the problem when the second interstage was out of alignment, too.

A paperwork trace determined both problematic interstages were built and shipped at roughly the same time, suggesting perhaps a manufacturing glitch.

A third interstage was brought to the launch pad and successful joined the first and second stages in late June, allowing pre-flight assembly to resume for the Delta 2 rocket.

The two faulty interstages have been returned to Boeing's plant in Pueblo, Colorado, for detailed inspections as an investigation continues into the problem, said Boeing Mission Director Rich Murphy.

Murphy said Friday that the incident indicates the hardware screening process used at the factory needs to be improved to ensure faulty rocket parts aren't shipped to the launch site in the future.

0809 GMT (4:09 a.m. EDT)

Launch Weather Officer Joel Tumbiolo just gave another update on the forecast for today. Overall weather is still looking promising for liftoff at 5:17 a.m. EDT (0917 GMT). The only issue of concern is clouds over the launch site being thicker than 4,500 feet, which is a constraint. A weather reconnaissance aircraft will be dispatched in about 15 minutes to check the cloud deck at 15,000 feet currently above the Cape does not violate the weather rule.

Otherwise, cloud ceiling is not expected to be a problem this morning for the Range is visually track the rocket during its initial flight, surface and upper level winds are acceptable and the nearest area of lightning from thunderstorms is well to our south and moving eastward, not toward the Cape.

0800 GMT (4:00 a.m. EDT)

The rocket is now fully fueled for launch today at 5:17 a.m. EDT (0917 GMT).

The Delta 2 rocket's first stage liquid oxygen tank has been filled to 100 percent, completing the fueling process at 3:58:51 a.m. EDT. LOX tanking took 25 minutes, 11 seconds today. However, given the nature of the super-cold cryogenic, the liquid oxygen will boil away. The launch team will allow the supply of LOX aboard the rocket to drop to 95 percent where it will be maintained. Topping to flight level will occur later in the countdown.

The liquid oxygen is consumed along with the RP-1 fuel by the first stage main engine.

The second stage was loaded with its storable nitrogen tetroxide and Aerozine 50 fuels earlier this week; and the third stage and strap-on booster rockets are solid-propellant.

0756 GMT (3:56 a.m. EDT)

Rapid-filling of the first stage liquid oxygen tank has been completed to the 95-percent level. A slower loading process will now start to bring the tank to flight level.

0743 GMT (3:43 a.m. EDT)

At launch pad 17A super-cold liquid oxygen is being pumped aboard the Boeing Delta 2 rocket's first stage as the countdown continues toward liftoff today at 5:17 a.m. EDT (0917 GMT).

Meanwhile, the launch team reports the vehicle's second stage tanks have been pressurized per the plan this morning.

0727 GMT (3:27 a.m. EDT)

T-minus 80 minutes and counting. Activities are proceeding on schedule at Cape Canaveral this morning for the launch of Boeing's Delta 2 rocket with the GPS 2R-5 satellite onboard.

In the past hour, the rocket's first stage was fueled with its supply of about 10,000 gallons of RP-1 kerosene. In the next minutes, liquid oxygen will begin flowing into the stage to complete the fueling process for launch.

Launch Weather Officer Joel Tumbiolo briefed officials a short time ago and reported all conditions are currently "go" for liftoff. Upper level winds are also acceptable currently.

0617 GMT (2:17 a.m. EDT)

T-minus 150 minutes. The terminal countdown is scheduled to begin at this time for today's liftoff of the Boeing Delta 2 rocket carrying the NAVSTAR Global Positioning System 2R-5 military navigation satellite. Over the next three hours, the launch team will ready the three-stage rocket, payload and ground support systems for the planned 5:17 a.m. EDT (0917 GMT) blastoff from pad 17A at Cape Canaveral Air Force Station in Florida.

With the countdown underway, the Complex 17 area will be cleared of workers as a safety precaution. A warning horn will be sounded at the seaside complex to alert personnel to depart and head back to road blocks.

Upcoming in the next few minutes, launch team members in the Delta Operations Building, or "soft blockhouse", located about eight miles west of the pad will oversee the pressurization of helium and nitrogen storage tanks inside the rocket's first and second stages; and the second stage fuel and oxidizer tanks will be pressurized for launch. In addition, the Delta's onboard guidance computer -- called the Redundant Inertial Flight Control Assembly or RIFCA -- will be turned on and configured for the mission.

The loading of 10,000 gallons of RP-1 fuel into the first stage is scheduled to start in just under 20 minutes from now. Liquid oxygen tanking for the first stage should begin around 3:32 a.m. EDT (0732 GMT).

0205 GMT (10:05 p.m. EDT)

The 12-story mobile service tower enclosing the Boeing Delta 2 rocket at Cape Canaveral's pad 17A has been rolled back as preparations continue for this morning's launch.

The structure was fully retracted by 9:43 p.m. EDT, officials report, and pre-launch activities are ongoing in advance of starting the terminal countdown at 2:17 a.m. EDT at T-minus 150 minutes.

Once terminal count begins, the loading of RP-1 fuel will follow as 10,000 gallons of the highly refined kerosene is pumped into the rocket's first stage. Later super-cold liquid oxygen will be loaded into the stage.

A pair of holds, lasting a half-hour in total duration, are built into the countdown. One hold for 20 minutes is planned at T-minus 20 minutes while a final hold at T-minus 4 minutes should last 10 minutes.

For now, liftoff remains scheduled to occur at 5:17 a.m. EDT (0917 GMT), the opening of a 26-minute launch window. Air Force weather forecasters are still giving a 60 percent chance conditions will be acceptable for launch. The main threat is electrically-charged clouds moving too close to the rocket's flight path to space.

FRIDAY, JULY 14, 2000

A $44 million military navigation satellite is awaiting its predawn ride into space Sunday atop a Boeing Delta 2 rocket to keep the U.S. Air Force's Global Positioning System constellation healthy.

Liftoff is scheduled for 5:17 a.m. EDT (0917 GMT) from pad 17A at Cape Canaveral Air Force Station in Florida. The available launch window extends 26 minutes to 5:43 a.m. EDT (0943 GMT).

Air Force meteorologists say there is a 60 percent chance of acceptable conditions for the launch. The main threats will be troublesome clouds. Launch Weather Officer Joel Tumbiolo issued this forecast today:

"Combination of surface high pressure ridge axis over southern Florida, surface frontal boundary over northern Florida, and upper level trough developing over the eastern U.S. will result in surface to 20,000 ft W-SW flow across the area. This pattern is highly favorable for daily occurrence of afternoon and evening thunderstorms over the Cape area over the few several days. Other than the typical afternoon and evening thunderstorms the presence of the surface frontal boundary and upper level trough over Florida will also result in overnight thunderstorms developing mainly over water areas throughout the next several days. Main concern during the launch window (regardless of the day) will be for anvil, debris, and thick layered clouds from thunderstorms initiating over the eastern Gulf of Mexico moving towards the Cape."

The launch time forecast calls for a few clouds at 3,000 feet with 1/8ths sky coverage, broken clouds at 12,000 feet with 5/8ths sky coverage and a broken deck at 25,000 with 6/8ths sky coverage, visibility of 10 miles or better, southwesterly winds 10 gusting to 15 knots, a temperature of 76 to 78 degrees F and relative humidity of 90 percent. Overall, conditions will be mostly cloudy with isolated showers in the vicinity.

Should the launch be delayed to Monday for some reason, similar weather is expected with a 60 percent chance of good conditions.

The Air Force held its Launch Readiness Review on Thursday and Boeing conducted its version today, all clearing the way for Sunday's mission.

"Things are going fine," Boeing Mission Director Rich Murphy said this morning. "We have closed out all of our issues."

The rocket's second stage was loaded with its supply of storable propellants on Wednesday. Thursday saw technicians performing beacon and Range Safety checks and completion of payload fairing installation. The fairing is the rocket's nose cone that shields the GPS satellite during the first five minutes of the launch.

Officials had hoped to move the liftoff up one day -- to Saturday morning -- if Lockheed Martin's Atlas rocket launched on schedule today from Cape Canaveral. Both launches use the Air Force's Eastern Range, which can support only one rocket flight every 24 hours.

The Atlas did lift off on time, but problems getting the Delta's fairing aligned and installed delayed processing work, preventing the chance to launch early.

"We are on our original schedule," Murphy said. "We just couldn't accelerate."

The GPS 2R-5 satellite, which the Air Force also refers to as Space Vehicle No. 44, is supposed to be placed into a highly elliptical transfer orbit 25 minutes and 27 seconds after liftoff when it is released from the Delta's third stage. The craft will later fire its onboard kick engine to achieve a circular orbit 10,900 miles above Earth where it will join the Air Force's GPS constellation.

The well-known GPS system features 24 primary spacecraft that provide precision location, speed and timing information to guide U.S. military troops, aircraft, submarines, ships, weapons and civilians around the globe.

Unlike a similar launch in May when GPS 2R-4 was deployed to fill a vacancy in the orbiting GPS network, the upcoming mission will simply add to the existing fleet.

"This launch will not immediately replace any single satellite," the Air Force said in a statement. "It is being launched to add constellation robustness and will be positioned as best suited to meet future constellation needs."

Today there are 28 GPS satellites in operation. However, 16 have lost redundancy in onboard systems and exactly half of the fleet -- 14 satellites -- have surpassed their 7-1/2-year life expectancy, the Air Force says. The ongoing deployment of GPS Block 2R satellites, built by Lockheed Martin, is aimed at keeping the crucial navigation system functioning for years to come.

Controllers plan to place the new GPS 2R-5 satellite in Plane B for the six-plane GPS constellation. The craft will actually assume a new slot in that plane -- Slot 5.

In the future when one of the four older GPS spacecraft malfunctions in that plane, GPS 2R-5 will be maneuvered into the failed-satellite's slot. The four satellites in Plane B were launched in 1989, 1993 and 1996.

"No satellites currently on orbit will be moved to 'make way' for the new satellite," the Air Force statement went on to read. "The launch will place the new vehicle in a position that allows it to add to the constellation health without taking up on of the slots that are typically referred to as the 'primary operational slots'."

Check back on Saturday for details on how Boeing resolved a problem assembling this rocket at the pad, which delayed the launch a month, plus details on the countdown and two video cameras mounted on the rocket.

On Sunday morning we will have extensive live coverage throughout the countdown and launch with running updates on this page and a QuickTime streaming video broadcast.