BY JUSTIN RAY

Follow the countdown and launch of the Delta 2 rocket with WorldView 1 commercial Earth-imaging spacecraft. Reload this page for the very latest on the mission.

TUESDAY, SEPTEMBER 18, 2007

A sophisticated new Earth-imaging satellite with sharp eyes, nimble moves and a broad memory was launched Tuesday, riding the ever-dependable Delta 2 rocket into orbit during a flawless ascent that set a new reliability mark for modern space boosters.

Read our launch story

2300 GMT (7:00 p.m. EDT; 4:00 p.m. PDT)

Here's some post-launch quotes issued in various press releases today following the successful flight of the United Launch Alliance Delta 2 rocket with DigitalGlobe's WorldView 1 satellite:

"This is an incredible achievement by the Delta launch team and we are extremely proud of our record of providing reliable, cost effective assured access to space for our customers," said Michael Gass, ULA president and chief executive officer. "It is a fitting tribute to our men and women in uniform this launch occurred on the U.S. Air Force's 60th anniversary. ULA is proud to work with the Air Force and we honor their sacrifices in service of our nation."

"What better way to celebrate our 60 years of service to this nation than to have the opportunity to launch a payload into space," said Col. Steve Tanous, 30th Space Wing commander at Vandenberg. "The Air Force has been involved in exploring the high frontier since the beginning of the 'space age' and we will continue to turn today's science fiction into reality."

"The successful launch of WorldView-1 represents the hard work of hundreds of DigitalGlobe employees, Ball Aerospace and Technologies Corporation, ITT Corporation and dozens of partner organizations," said Jill Smith, chief executive officer of DigitalGlobe. "The addition of WorldView 1 to our growing constellation of satellites is a testament of our commitment to our customers. We look forward to supplying the growing market with an unprecedented offering of high-resolution geospatial products."

"Today's launch of WorldView 1 marks our second successful commercial launch for Boeing Launch Services in 2007 and puts us on track for a very successful year with two of our three scheduled launches completed," said Ken Heinly, vice president of Boeing Launch Services.

2005 GMT (4:05 p.m. EDT; 1:05 p.m. PDT)

Some photos of today's liftoff taken from the press viewing location are posted here.

1958 GMT (3:58 p.m. EDT; 12:58 p.m. PDT)

The Delta program's next launch is just a week away. That flight will send NASA's Dawn spacecraft into the asteroid belt to explore the tiny worlds of Vesta and Ceres. A Delta 2-Heavy booster is scheduled to launch the mission Wednesday, Sept. 26 from pad 17B at Cape Canaveral Air Force Station, Florida.

The next Delta from Vandenberg is targeted for Dec. 5 to deploy the second COSMO-SkyMed spacecraft for the Italian Space Agency and the Italian Ministry of Defence. A Delta 2 launched the first COSMO satellite earlier this year to begin assembling an orbiting constellation of four radar-imaging craft for civilian and military uses.

1954 GMT (3:54 p.m. EDT; 12:54 p.m. PDT)

This is the 75th consecutive successful Delta 2 rocket launch dating back to May 1997, marking a new reliability record for a modern space booster.

Prior to today's flight, the Delta 2 rocket's success string was tied with the now-retired Ariane 4 vehicle at 74 in a row. No other single rocket design in the current era has enjoyed such a long and spotless consecutive record.

The Delta 2's overall history since debuting in 1989 has achieved 128 successes in 130 flights.

1948 GMT (3:48 p.m. EDT; 12:48 p.m. PDT)

T+plus 73 minutes, 28 seconds. SPACECRAFT SEPARATION! The WorldView 1 spacecraft has been released from the Delta 2 rocket's second stage, completing today's launch!

1947 GMT (3:47 p.m. EDT; 12:47 p.m. PDT)

T+plus 72 minutes, 20 seconds. Spinup of the second stage is underway.

1947 GMT (3:47 p.m. EDT; 12:47 p.m. PDT)

T+plus 72 minutes. The Oakhanger tracking site has locked to the Delta's telemetry signal.

1937 GMT (3:37 p.m. EDT; 12:37 p.m. PDT)

T+plus 62 minutes. At this time, the second stage should be moving to the proper orientation for payload release. This maneuver will take several minutes to complete. A spinup of the stage will occur about a minute before WorldView is cast free.

1933 GMT (3:33 p.m. EDT; 12:33 p.m. PDT)

T+plus 58 minutes. Delta has exited the Hartebeesthoek tracking station coverage zone. Oakhanger tracking station in the United Kingdom will acquire the rocket's signal in about 12 minutes to monitor separation of the WorldView spacecraft from the second stage.

1932 GMT (3:32 p.m. EDT; 12:32 p.m. PDT)

T+plus 57 minutes. The orbit adjustment burn was completed as planned northwest of Madagascar. The second stage has reached an orbit with an apogee of 272.38 miles, perigee of 266.1 miles and inclination of 97.49 degrees to the equator. All of those values are right on target.

1929 GMT (3:29 p.m. EDT; 12:29 p.m. PDT)

T+plus 54 minutes, 40 seconds. The second stage engine has fired for the brief burn designed to propel its two-and-a-half-ton spacecraft payload into the proper polar orbit.

1929 GMT (3:29 p.m. EDT; 12:29 p.m. PDT)

T+plus 54 minutes. Second stage hydraulics have been activated.

1928 GMT (3:28 p.m. EDT; 12:28 p.m. PDT)

T+plus 53 minutes, 22 seconds. Small jets on the second stage have come on to settle propellant in the rocket for upcoming engine firing.

1926 GMT (3:26 p.m. EDT; 12:26 p.m. PDT)

T+plus 51 minutes, 30 seconds. Hartebeesthoek has picked up the rocket's signal as it flies northbound toward Africa.

1925 GMT (3:25 p.m. EDT; 12:25 p.m. PDT)

T+plus 50 minutes. The rocket's current orbit is 278.5 nautical miles at apogee, 98.7 miles at perigee and an inclination of 97.41 degrees.

1919 GMT (3:19 p.m. EDT; 12:19 p.m. PDT)

T+plus 44 minutes. The next firing by the Delta rocket's second stage is coming up in 10 minutes. The Hartebeesthoek tracking station in South Africa should acquire the rocket in about five minutes. The site will relay the rocket's signal back to Vandenberg to provide confirmation of the second stage burn.

1910 GMT (3:10 p.m. EDT; 12:10 p.m. PDT)

T+plus 35 minutes. A map of the rocket's planned flight path is available here.

1905 GMT (3:05 p.m. EDT; 12:05 p.m. PDT)

T+plus 30 minutes. Delta is flying in a parking orbit along a trajectory that cruises above the South Pacific before crossing Antarctica and then swinging northbound toward Africa. Here's what is still ahead in the launch today:

The second stage reignites its engine for 12 seconds northwest of Madagascar at T+plus 54 minutes to reach a near-circular polar orbit 270 nautical miles above the planet.

A short time after engine cutoff, the rocket exits the communications coverage zone of the Hartebeesthoek tracking station in South Africa, leaving engineers out of contact with Delta for several minutes. The second stage will be maneuvering itself to the proper orientation and beginning to spin up for deployment of WorldView. The northward course will cross eastern Africa, the Red Sea and Turkey before telemetry information is restored through the Oakhanger tracking station in the United Kingdom.

The two-and-a-half-ton WorldView payload should be released from the rocket at 12:48 p.m. Vandenberg time (3:48 p.m. EDT; 1948 GMT), some 73 minutes after blastoff, while flying near Finland.

The rocket stage performs a pair of evasive maneuvers -- one with its cold-gas system and another by firing the engine -- to move away from WorldView. A later fuel-depletion burn will put the stage into an entirely different orbit.

1855 GMT (2:55 p.m. EDT; 11:55 a.m. PDT)

T+plus 20 minutes. As the rocket coasts in this parking orbit, it performs a "BBQ roll" maneuver to keep the thermal conditions on the vehicle equal. This maneuver was scheduled to start at about T+plus 18 minutes, 10 seconds and conclude at T+plus 42 minutes, 50 seconds.

1850 GMT (2:50 p.m. EDT; 11:50 a.m. PDT)

T+plus 15 minutes. As the rocket has traveled out of range from the tracking plane, creating a data blackout until the Delta's signal is acquired via a South African ground station a half-hour from now.

1849 GMT (2:49 p.m. EDT; 11:49 a.m. PDT)

T+plus 14 minutes. The official liftoff time was 1835:00.526 GMT.

1845 GMT (2:45 p.m. EDT; 11:45 a.m. PDT)

T+plus 10 minutes, 31 seconds. SECO 1 now confirmed. The second stage's Aerojet-made engine has completed its initial burn for the launch, putting the Delta rocket and attached WorldView spacecraft into orbit.

1844 GMT (2:44 p.m. EDT; 11:44 a.m. PDT)

T+plus 9 minutes, 30 seconds. The rocket has flown out of range from the Vandenberg ground tracking sites. A P-3 instrumented aircraft over the Pacific will be tracking the rocket's telemetry signal as the Delta flies beyond Vandenberg's horizon.

1843 GMT (2:43 p.m. EDT; 11:43 a.m. PDT)

T+plus 8 minutes, 30 seconds. About two minutes remain in this burn of the second stage engine to achieve the intended parking orbit.

1842 GMT (2:42 p.m. EDT; 11:42 a.m. PDT)

T+plus 7 minutes. The Delta 2 rocket is 95 miles in altitude, 668 miles downrange, traveling over 13,000 mph.

1841 GMT (2:41 p.m. EDT; 11:41 a.m. PDT)

T+plus 6 minutes, 20 seconds. The second stage is firing normally.

1840 GMT (2:40 p.m. EDT; 11:40 a.m. PDT)

T+plus 5 minutes, 50 seconds. The vehicle is 81 miles in altitude, 435 miles downrange from the launch pad and traveling at 12,000 mph.

1840 GMT (2:40 p.m. EDT; 11:40 a.m. PDT)

T+plus 5 minutes. The rocket's nose cone enclosing the spacecraft has been jettisoned.

1839 GMT (2:39 p.m. EDT; 11:39 a.m. PDT)

T+plus 4 minutes, 41 seconds. The Delta's second stage engine has ignited!

1839 GMT (2:39 p.m. EDT; 11:39 a.m. PDT)

T+plus 4 minutes, 37 seconds. MECO. The first stage main engine cutoff is confirmed, and the spent stage has been jettisoned!

1838 GMT (2:38 p.m. EDT; 11:38 a.m. PDT)

T+plus 3 minutes, 50 seconds. The vehicle is 50 miles in altitude, 137 miles downrange from the launch pad and traveling at 8,200 mph.

1838 GMT (2:38 p.m. EDT; 11:38 a.m. PDT)

T+plus 3 minutes, 20 seconds. The first stage main engine continues to burn normally. The Pratt & Whitney Rocketdyne powerplant consumes kerosene fuel and liquid oxygen to produce about 200,000 pounds of thrust.

1837 GMT (2:37 p.m. EDT; 11:37 a.m. PDT)

T+plus 2 minutes, 50 seconds. The Delta 2 rocket is 36 miles in altitude, 51 miles downrange, traveling at nearly 5,000 mph.

1837 GMT (2:37 p.m. EDT; 11:37 a.m. PDT)

T+plus 2 minutes, 14 seconds. The trio of air-ignited solid boosters have completed their burn and separated. Now, the Delta 2's first stage RS-27A main engine is providing the sole thrust for the next few minutes.

1836 GMT (2:36 p.m. EDT; 11:36 a.m. PDT)

T+plus 1 minute, 31 seconds. The ground-lit boosters have jettisoned from the first stage. They remained attached until the rocket cleared off-shore oil rigs.

1836 GMT (2:36 p.m. EDT; 11:36 a.m. PDT)

T+plus 1 minute, 9 seconds. All six ground-start solid rocket boosters have burned out and the three air-lit motors have fired to life.

1836 GMT (2:36 p.m. EDT; 11:36 a.m. PDT)

T+plus 50 seconds. One minute into the flight. Delta is five miles in altitude, nine miles downrange.

1835 GMT (2:35 p.m. EDT; 11:35 a.m. PDT)

T+plus 50 seconds. The rocket has flown through the area of maximum aerodynamic pressure in the lower atmosphere. Coming up on ignition of the remaining three strap-on boosters.

1835 GMT (2:35 p.m. EDT; 11:35 a.m. PDT)

T+plus 35 seconds. Delta has broken the sound barrier. All is looking good.

1835 GMT (2:35 p.m. EDT; 11:35 a.m. PDT)

T+plus 15 seconds. This 73-minute flight of the Delta 2 rocket is underway. The has ascended from the pad and started maneuvering to its southerly heading for the trek downrange over the Pacific. The vehicle is riding the power of its first stage main engine and the six ground-lit strap-on boosters.

1835 GMT (2:35 p.m. EDT; 11:35 a.m. PDT)

LIFTOFF! Liftoff of Delta 2, launching the commercial Earth-imaging advancements of WorldView 1. And the vehicle has cleared the tower!

1834 GMT (2:34 p.m. EDT; 11:34 a.m. PDT)

T-minus 30 seconds. SRB ignitors will be armed at T-minus 11 seconds.

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

1834 GMT (2:34 p.m. EDT; 11:34 a.m. PDT)

T-minus 35 seconds. Hydraulics are reported "go."

1834 GMT (2:34 p.m. EDT; 11:34 a.m. PDT)

T-minus 1 minute. The Range has given its final clear-to-launch.

1833 GMT (2:33 p.m. EDT; 11:33 a.m. PDT)

T-minus 80 seconds. First stage liquid oxygen topping to 100 percent is underway.

1833 GMT (2:33 p.m. EDT; 11:33 a.m. PDT)

T-minus 1 minute, 45 seconds. The launch pad water suppression system is being activated.

1833 GMT (2:33 p.m. EDT; 11:33 a.m. PDT)

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.

1832 GMT (2:32 p.m. EDT; 11:32 a.m. PDT)

T-minus 2 minutes, 30 seconds. The WorldView payload have been declared "go" for launch.

1832 GMT (2:32 p.m. EDT; 11:32 a.m. PDT)

T-minus 2 minutes, 45 seconds. Vehicle ordnance is being armed.

1832 GMT (2:32 p.m. EDT; 11:32 a.m. PDT)

T-minus 3 minutes. All remains "go" for launch.

1831 GMT (2:31 p.m. EDT; 11:31 a.m. PDT)

T-minus 3 minutes, 45 seconds and counting. The Delta 2 rocket's systems are now transferring to internal power for launch. And the launch pad water system is being enabled.

1831 GMT (2:31 p.m. EDT; 11:31 a.m. PDT)

T-minus 4 minutes and counting! Clocks are ticking down the final moments for liftoff of Delta 326 with the WorldView 1 spacecraft. Launch is set for 11:35 a.m. local time from Vandenberg Air Force Base, California.

1830 GMT (2:30 p.m. EDT; 11:30 a.m. PDT)

Now five minutes from launch! The "go" has been given for release of the hold in one minute.

1829 GMT (2:29 p.m. EDT; 11:29 a.m. PDT)

The WorldView 1 spacecraft is undergoing final configuring for launch.

1828 GMT (2:28 p.m. EDT; 11:28 a.m. PDT)

Three minutes are remaining in this hold. The team is receiving reminders of procedures and instructions.

1826 GMT (2:26 p.m. EDT; 11:26 a.m. PDT)

All systems are reported "ready" by the launch team. There are no technical problems standing in the way of liftoff.

1826 GMT (2:26 p.m. EDT; 11:26 a.m. PDT)

The final pre-flight poll of the launch team is beginning.

1825 GMT (2:25 p.m. EDT; 11:25 a.m. PDT)

Now 10 minutes from launch of the WorldView 1 satellite for operator DigitalGlobe of Longmont, Colorado. The spacecraft will be capable of imaging 290,000 square miles of the planet's surface per day with half-meter resolution, a clarity not possible by any civilian satellite in orbit today.

1821 GMT (2:21 p.m. EDT; 11:21 a.m. PDT)

T-minus 4 minutes and holding. The countdown has entered the final planned built-in hold. This is a scheduled 10-minute pause leading to today's liftoff time of 11:35 a.m. local (2:35 p.m. EDT; 1835 GMT) for the Delta 2 rocket with WorldView 1.

During the hold, officials will poll the various team members in the "soft blockhouse," Range Operations Control Center and Mission Directors Center to verify all systems are ready to enter into the final phase of the countdown.

1819 GMT (2:19 p.m. EDT; 11:19 a.m. PDT)

The launch weather officer reports conditions are "go" for liftoff. It has turned out to be a chilly, overcast morning at Vandenberg. But the weather is not violating any constraints.

1816 GMT (2:16 p.m. EDT; 11:16 a.m. PDT)

The first stage kerosene fuel tank is being pressurized for launch.

1810 GMT (2:10 p.m. EDT; 11:10 a.m. PDT)

T-minus 15 minutes and counting. Countdown clocks are running again following the planned 20-minute hold. The count will continue to the T-minus 4 minute mark where another hold is scheduled. Launch remains set to occur at 11:35 a.m. local (2:35 p.m. EDT; 1835 GMT).

The most recent weather balloon information shows acceptable upper level wind conditions. There was some concern earlier in the morning after the first couple of balloons.

1806 GMT (2:06 p.m. EDT; 11:06 a.m. PDT)

A status check of the launch team members was just performed. All responded with a "ready" to press ahead with the countdown.

1805 GMT (2:05 p.m. EDT; 11:05 a.m. PDT)

Now half-way through this built-in hold at T-minus 15 minutes. Once the countdown resumes, clocks will tick down to the T-minus 4 minute mark where a 10-minute hold is planned.

Today's launch will be:

• The 326th Delta rocket launch since 1960
• The fourth of 2007
• The 130th Delta 2 rocket mission since 1989

1750 GMT (1:50 p.m. EDT; 10:50 a.m. PDT)

T-minus 15 minutes and holding. Clocks have entered the first of two planned hold periods during the final quarter of the Terminal Countdown for today's launch. This pause will last 20 minutes in duration.

These holds are designed to give the launch team a chance to deal with any problems and catch up on work that could be running behind schedule.

1746 GMT (1:46 p.m. EDT; 10:46 a.m. PDT)

The first stage engine steering checks are complete.

1741 GMT (1:41 p.m. EDT; 10:41 a.m. PDT)

The second stage engine slews are complete. First stage tests have begun.

1740 GMT (1:40 p.m. EDT; 10:40 a.m. PDT)

The launch team is beginning the "slew" or steering checks of the first and second stage engines. These are gimbal tests of the nozzles on the first stage main engine and twin vernier engines and second stage engine to ensure the rocket will be able to steer itself during launch.

1735 GMT (1:35 p.m. EDT; 10:35 a.m. PDT)

Now one hour away from the scheduled liftoff of the Delta 2 rocket from Space Launch Complex 2 at Vandenberg Air Force Base in California. The site is on the Pacific coastline, about 140 miles northwest of Los Angeles.

Today's 14-minute launch window runs from 11:35 to 11:49 a.m. local time (2:35-2:49 p.m. EDT; 1835-1849 GMT).

Following liftoff, the vehicle will head southward as it climbs into orbit on a 73-minute flight to deploy the WorldView 1 commercial Earth-imaging satellite.

1731 GMT (1:31 p.m. EDT; 10:31 a.m. PDT)

Inhibited checks are now beginning for the Range Safety command destruct receivers that would be used in destroying the Delta rocket should the vehicle veer off course or malfunction during the launch.

1725 GMT (1:25 p.m. EDT; 10:25 a.m. PDT)

T-minus 40 minutes and counting. Countdown clocks are continuing to the T-minus 15 minute mark where a 20-minute built-in hold is planned. A final 10-minute hold at T-minus 4 minutes will lead to the target liftoff time of 11:35 a.m. local (2:35 p.m. EDT; 1835 GMT).

1723 GMT (1:23 p.m. EDT; 10:23 a.m. PDT)

The upper level wind situation appears to be trending in the right direction. Data from last couple of weather balloons have shown improving conditions aloft.

1718 GMT (1:18 p.m. EDT; 10:18 a.m. PDT)

Loading of the Delta 2 rocket's first stage liquid oxygen tank was completed at 10:18 a.m. local time. The operation took 26 minutes and 35 seconds today. The tank will be replenished through the countdown to replace the super-cold liquid oxygen that naturally boils away.

The rocket is now fully fueled for launch. The vehicle's first stage was successfully loaded with RP-1 kerosene fuel earlier today. The second stage was filled with its storable nitrogen tetroxide and Aerozine 50 fuels earlier in the week. And the nine strap-on booster rockets are solid-propellant.

1711 GMT (1:11 p.m. EDT; 10:11 a.m. PDT)

Liquid oxygen loading has been underway for 20 minutes. Once the first stage tank is 95 percent full, the "rapid load" valve will be closed and the slower "fine load" phase will continue to fill the rocket.

1701 GMT (1:01 p.m. EDT; 10:01 a.m. PDT)

Now 10 minutes into this approximate 25-minute process to fill the first stage liquid oxygen tank.

1651 GMT (12:51 p.m. EDT; 9:51 a.m. PDT)

Cryogenic liquid oxygen, chilled to Minus-298 degrees F, has started flowing from a 28,000-gallon storage tank at Space Launch Complex-2 West, through plumbing and into the bottom of the Delta 2 rocket. The LOX will be consumed by the first stage main engine during the first four-and-a-half minutes of flight along with the 10,000 gallons of RP-1 kerosene already loaded aboard the vehicle.

1645 GMT (12:45 p.m. EDT; 9:45 a.m. PDT)

The launch team has a "go" to begin preparations for loading the rocket's first stage liquid oxygen tank as planned.

1644 GMT (12:44 p.m. EDT; 9:44 a.m. PDT)

The rocket's guidance system activation is reported complete.

1640 GMT (12:40 p.m. EDT; 9:40 a.m. PDT)

The latest weather forecast for launch time predicts foggy conditions, stratus clouds at 800 feet, visibility of four miles, a temperature between 58 and 62 degrees F and pad winds from the northwest at 10-15 knots, gusting to 18 knots.

1635 GMT (12:35 p.m. EDT; 9:35 a.m. PDT)

Launch time is now two hours away. Upper level winds that the rocket will experience during its early phase of flight are being monitored carefully. Initial weather balloon data this morning has indicated a possible concern for the rocket's ability to safely fly through the winds. Additional balloons will be released during the rest of the countdown to gauge any changes in the conditions aloft.

1620 GMT (12:20 p.m. EDT; 9:20 a.m. PDT)

The first stage fuel tank of the Delta 2 rocket has been fully loaded for today's planned launch. The tank was filled with a highly refined kerosene, called RP-1, during a 19-minute, 34-second process that concluded at 9:19:59 a.m. local time.

The next major task in the count will be loading super-cold cryogenic liquid oxygen into the first stage starting in about 30 minutes.

The kerosene and liquid oxygen will be consumed by the stage's Pratt & Whitney Rocketdyne RS-27A main engine and twin vernier steering thrusters during the initial four-and-a-half minutes of flight.

1618 GMT (12:18 p.m. EDT; 9:18 a.m. PDT)

Rapid-loading of the RP-1 tank has concluded with 9,900 gallons already aboard the rocket. Fine load is continuing to finish filling the tank.

1614 GMT (12:14 p.m. EDT; 9:14 a.m. PDT)

The launch team has computed that today's full load for the first stage fuel tank is 10,078 gallons.

Once the tank is filled to 98 percent or 9,900 gallons, the "rapid load" valve will be closed and the slower "fine load" phase will continue to top off the tank.

1609 GMT (12:09 p.m. EDT; 9:09 a.m. PDT)

The first stage tank is half full, with 5,000 gallons aboard now.

1604 GMT (12:04 p.m. EDT; 9:04 a.m. PDT)

First stage helium and nitrogen pressurization is complete.

1600 GMT (12:00 p.m. EDT; 9:00 a.m. PDT)

Fueling is now underway. About 10,000 gallons of the kerosene propellant are pumping into the base of the rocket from storage tanks at the pad as fueling of the Delta 2's first stage begins for today's launch.

1556 GMT (11:56 a.m. EDT; 8:56 a.m. PDT)

First stage fueling preparations are starting. After verifying valves, sensors, flow meters and equipment are ready, a highly-refined kerosene fuel will begin flowing into the vehicle a few minutes from now.

1540 GMT (11:40 a.m. EDT; 8:40 a.m. PDT)

Activation of the rocket's Redundant Inertial Flight Control Assembly guidance computer is beginning now. And the launch team is starting pressurization steps for the first and second stage helium and nitrogen systems and second stage fuel tanks.

1535 GMT (11:35 a.m. EDT; 8:35 a.m. PDT)

BEGIN COUNT. The Terminal Countdown has been initiated for today's launch of the WorldView 1 spacecraft aboard the Delta 2 rocket. No technical concerns have been reported by the launch team and activities are progressing on schedule. But upper level winds are being watched closely.

The countdown clocks currently stand at T-minus 150 minutes and counting. Two planned holds -- at the T-minus 15 minute and the T-minus 4 minute points -- will give the launch team some time to catch up on any work running behind. The first hold will last 20 minutes in duration, the second extends 10 minutes.

Today's 14-minute launch window runs from 11:35 to 11:49 a.m. local time (2:35-2:49 p.m. EDT; 1835-1849 GMT).

1526 GMT (11:26 a.m. EDT; 8:26 a.m. PDT)

The launch team has been polled to ensure all stations are manned and systems are prepared to proceed with the countdown. Everyone reported "ready."

1520 GMT (11:20 a.m. EDT; 8:20 a.m. PDT)

"Man stations for Terminal Count." That was the message just announced to the launch team in preparation for starting the Terminal Countdown some 15 minutes from now. A readiness poll will be conducted in five minutes.

Liftoff of the Delta 2 rocket remains targeted to occur ontime at 11:35 a.m. local time (2:35 p.m. EDT; 1835 GMT).

1505 GMT (11:05 a.m. EDT; 8:05 a.m. PDT)

Now 30 minutes through this scheduled hour-long hold in the countdown.

The Delta rocket today will be flying in its configuration known as the 7920-10 vehicle. The two-stage launcher is fitted with nine strap-on solid-propellant motors and a 10-foot diameter composite nose cone.

1453 GMT (10:53 a.m. EDT; 7:53 a.m. PDT)

The SLC-2W launch pad restricted area has been cleared of all personnel for the rest of the countdown.

1435 GMT (10:35 a.m. EDT; 7:35 a.m. PDT)

T-minus 150 minutes and holding. The countdown has just entered a planned 60-minute built-in hold at Vandenberg Air Force Base in California. The Terminal Countdown will begin once this hold is concluded.

1400 GMT (10:00 a.m. EDT; 7:00 a.m. PDT)

The 177-foot tall mobile service tower was retracted from the ULA Delta 2 rocket at Vandenberg Air Force Base's Space Launch Complex-2 West pad this morning, completing a crucial step in the preparations for liftoff.

A photo of the rocket standing on the pad is available here.

The gantry was used to stack the two-stage vehicle, the nine strap-on solid rocket motors and the WorldView 1 payload atop the pad's launch mount. The tower also provided the primary weather protection and worker access to the rocket during its stay at the oceanside complex on North Vandenberg.

Ground teams have spent the past couple of hours after tower rollback getting the pad secured in advance of the Terminal Countdown. Launch remains targeted for 11:35 a.m. local time (2:35 p.m. EDT; 1835 GMT).

1315 GMT (9:15 a.m. EDT; 6:15 a.m. PDT)

A successful launch today by the Delta 2 rocket would set a new modern era reliability record for a space booster. Liftoff remains on schedule for 11:35 a.m. local time (2:35 p.m. EDT; 1835 GMT) from Vandenberg Air Force Base, California.

Pad technicians overnight retracted the mobile service tower from around the Delta at the Space Launch Complex-2 West site as countdown operations got underway. The Terminal Countdown will pick up three hours before launch time.

It will take about 73 minutes for the Delta to haul the WorldView 1 satellite into the desired orbit and deploy the two-and-a-half-ton commercial Earth-imaging spacecraft.

If all goes well, the launch will extend the Delta 2 rocket's string of consecutive successes to 75, breaking the current tie with the now-retired Ariane 4 vehicle at 74 in a row. No other single rocket design in the current era has enjoyed such a long and spotless track record.

"Launch vehicle people tend to be superstitious, so we tend not to talk about it too much before it happens," said Kris Walsh, United Launch Alliance's director of NASA and commercial programs. "We take it one launch at a time."

Delta 2 has been flawless since 1997, amassing its consecutive string by launching spacecraft for military, NASA and commercial users, including the Global Positioning System satellites, the twin Mars rovers Spirit and Opportunity, the Spitzer Space Telescope and the Mercury-bound MESSENGER orbiter. In the rocket's 129 flights overall since debuting in 1989, 127 of those launches have been successful.

"I love the Delta 2. We've been able to meet schedule, we've been able to put some exciting, exciting payloads out into orbit. I think one of the things that's revolutionized the world is the GPS system. We were the ones that put all of those satellites up into orbit. So I think it's been a tremendous boon for the United States government and commercial (customers). It's a great little rocket. I'll continue to fly it as long as I can," Walsh said.

There are 26 Delta 2 rockets remaining to fly, counting today's mission.

"It's a pretty firm number, if we don't end up starting production again," Walsh said.

The future launches include 11 flights for NASA including next week's Dawn asteroid probe, the five remaining GPS 2R satellites for the Air Force, four commercial missions including today's and six rockets not yet sold, Walsh said.

Keeping the Delta 2 around for the long-term depends on finding a government partner. The Pentagon and NASA have shared the costs over the past years. But the military will soon end its use of the Delta 2 in favor of the Evolved Expendable Launch Vehicles.

The Air Force has backed the Delta 2 since the rocket's earliest days for launching the GPS constellation. But after the five remaining satellites in the current series are launched soon, the Air Force will be turning its attention to next-generation spacecraft that will fly on the larger Atlas 5 and Delta 4 boosters.

That will leave NASA as the main government user of Delta 2. Thus far, the space agency has been reluctant to fund future production of the rocket and the associated infrastructure maintenance entirely on its own.

"We'll continue (Delta 2) as long as it's a viable rocket and we have a government anchor customer," Walsh said.

MONDAY, SEPTEMBER 17, 2007
1735 GMT (1:35 p.m. EDT; 10:35 a.m. PDT)

The Delta 2 rocket and its commercial WorldView 1 cargo have been cleared for liftoff Tuesday following a final Launch Readiness Review held at Vandenberg Air Force Base this morning.

"The LRR was really short and sweet - no issues," said Kris Walsh, United Launch Alliance's director of NASA and commercial programs for the Delta rocket.

Tuesday's launch window will extend from 11:35 to 11:49 a.m. local time (2:35-2:49 p.m. EDT; 1835-1849 GMT).

But the middle of the window is expected to be unusable due to a Collision Avoidance period. A COLA blackout period in a window ensures the rocket doesn't launch at a specific time that would take the trajectory too close to another object already in space.

"There is a COLA for tomorrow. Currently, it's right in the middle of our window. That doesn't really concern us because we target (liftoff) for the front of the window, and if we need more time we usually target for the end of the window," Walsh explained.

United Launch Alliance is conducting the rocket flight while Boeing manages the commercial contract with satellite operator DigitalGlobe. ULA was formed last December to merge Boeing's Delta and Lockheed Martin's Atlas rocket families under one joint venture to cut the cost for U.S. government space launches.

The parent companies have retained the ability to sell the rockets on the commercial marketplace, and the launch of WorldView 1 will be the second such commercial flight since ULA began.

Air Force meteorologists are predicting a 100 percent chance of acceptable launch weather on Tuesday. Breezy winds are expected to increase by late morning but remain within limits for the Delta 2 rocket.

The launch time outlook calls for a few stratus clouds at 1,000 feet, seven miles of visibility, a temperature in the low 60s F and northwesterly winds from 300 to 330 degrees at 10-15 knots, gusting to 18 knots. Maximum upper level winds are anticipated between 35,000 and 40,000 feet from the west-southwest at 70 knots.

Should the launch be delayed to Wednesday for some reason, the weather forecast deteriorates to only a 40 percent chance of favorable liftoff conditions due to strong winds as a storm system approaches.

Wednesday's launch window is expected to shrink by 10 minutes at the request of the payload customer. The revised period would extend from 11:45 to 11:49 a.m. local time (2:45-2:49 p.m. EDT; 1845-1849 GMT).

Walsh said a successful launch Tuesday or Wednesday would clear the way for liftoff of NASA's Dawn asteroid probe next Wednesday, Sept. 26, aboard another Delta 2 rocket from Cape Canaveral, Florida.

"It's looking very good there. We got through the Launch Site Readiness Review and put the satellite up (on the rocket)," Walsh said. "It's a little quiescent now as we have our team focused over here (for WorldView). But if we launch either Tuesday or Wednesday we'll stay on the 26th."

Our coverage of the Dawn launch will be available here.

SUNDAY, SEPTEMBER 16, 2007

A new Earth-imaging satellite to provide high-resolution pictures for commercial and government users heads for space from California on Tuesday, launching aboard a Delta 2 rocket.

The WorldView 1 spacecraft will be capable of imaging 290,000 square miles of the planet's surface per day with half-meter resolution, a clarity not possible by any civilian satellite in orbit today.

That anticipated quality has the U.S. government signed up as a customer to receive WorldView's images of specific global hot spots and areas of interest for intelligence-gathering.

And the commercial potential for such imagery continues to increase, ranging from urban planners, real estate developers, environmental monitors and the wildly popular Google Earth.

"This is an exciting event for not only the companies involved with the launch, but also the growing number of consumers and businesspeople using satellite imagery in their daily lives," said Jill Smith, CEO of DigitalGlobe.

DigitalGlobe, based in Longmont, Colorado, has operated its QuickBird satellite for nearly six years. But the imminent addition of WorldView 1 promises to generate five times the image-collecting capacity.

"Being able to satisfy many more customer orders and larger area collections is really the big differentiator from QuickBird and our new satellite WorldView," said Chuck Herring, DigitalGlobe's director of corporate communications.

A United Launch Alliance Delta 2 rocket is responsible for delivering the WorldView 1 satellite into orbit. A good ascent Tuesday would mark the 75th consecutive successful launch for the workhorse booster over the past 10 years.

Liftoff is scheduled for 11:35 a.m. local time (2:35 p.m. EDT; 1835 GMT) from Vandenberg Air Force Base, California. The two-stage, 12-story rocket stands fully assembled inside the gantry at the Space Launch Complex-2 West pad.

A final launch readiness review is scheduled for Monday morning to give approval to enter into the countdown procedures.

On launch morning, the first stage will be filled with highly refined kerosene and supercold liquid oxygen propellants. The second stage was loaded with its storable hypergolic fuel last week.

A standard pause at the T-minus 4 minute point will give launch managers the opportunity to survey the status before countdown clocks progress into the quickly paced final minutes that see the vehicle switch to internal power, the liquid oyxgen tank pressurized and systems armed.

The main engine fires up a moment before the command is issued to ignite six of the nine strap-on solid rocket motors clustered around the Delta, giving the vehicle more than 700,000-pounds of thrust to dart away from the Central California launch base.

After swiftly climbing away from the pad, the rocket will arc southward over the Pacific Ocean. The six solid boosters lit on the ground extinguish a minute into flight as the remaining three motors are ignited. Once clear of offshore oil-drilling rigs, the half-dozen spent boosters are jettisoned at an altitude of 15 nautical miles to fall harmlessly into the sea. The air-lit motors burn out and separate two minutes after liftoff when the rocket is about 29 nautical miles up.

That leaves the kerosene-powered main engine to continue pushing the rocket above an altitude of 60 nautical miles. The spent stage then jettisons at T+plus 4 minutes, 37 seconds to let the hydrazine-fueled second stage propel the vehicle the rest of the way into space. The two-piece nose cone that encased WorldView during the trek through the atmosphere is shed just seconds after the second stage comes to life.

Ten-and-a-half minutes into the ascent, the second stage completes its initial firing while approaching the equator. The Delta settles into a parking orbit of 99 by 278 nautical miles along a trajectory that cruises above the South Pacific before crossing Antarctica and then swinging northbound toward Africa. The second stage reignites its engine for 12 seconds northwest of Madagascar at T+plus 54 minutes to reach a near-circular polar orbit 270 nautical miles above the planet.

A short time after engine cutoff, the rocket exits the communications coverage zone of the Hartebeesthoek tracking station in South Africa, leaving engineers out of contact with Delta for several minutes. The second stage will be maneuvering itself to the proper orientation and beginning to spin up for deployment of WorldView. The northward course will cross eastern Africa, the Red Sea and Turkey before telemetry information is restored through the Oakhanger tracking station in the United Kingdom.

The two-and-a-half-ton WorldView payload should be released from the rocket at 12:48 p.m. Vandenberg time (3:48 p.m. EDT; 1948 GMT), some 73 minutes after blastoff, while flying near Finland.

The rocket stage performs a pair of evasive maneuvers -- one with its cold-gas system and another by firing the engine -- to move away from WorldView. A later fuel-depletion burn will put the stage into an entirely different orbit.

WorldView will undergo post-launch activities and testing before entering service. Initial imagery from the spacecraft is expected within a month.

Watch this page Tuesday for live play-by-play countdown and launch reports throughout the day.

MONDAY, SEPTEMBER 10, 2007

Preparations are underway for the launch of the WorldView 1 spacecraft, a sophisticated Earth-imaging satellite for commercial operator DigitalGlobe of Longmont, Colorado.

A United Launch Alliance Delta 2 rocket will haul the satellite into polar orbit from Vandenberg Air Force Base in California. Liftoff is scheduled for September 18 at 11:35 a.m. local time (2:35 p.m. EDT; 1835 GMT). The day's launch window extends 14 minutes.

The launch timeline, as well as the rocket's flight path and other background information on the mission can be found in the sidebar on the left side of this page.

A complete preview of the launch will be posted here next week. And watch this page for live updates during the countdown and ascent of the Delta 2 rocket.