BY JUSTIN RAY

Follow the countdown and launch of the Orbital Sciences Taurus XL rocket with the ROCSAT-2 Earth observation satellite. Reload this page for the very latest on the mission.

THURSDAY, MAY 20, 2004

The first Taurus XL rocket, a beefed up model of Orbital Sciences' small satellite launcher, darted into polar orbit Thursday, deploying a Taiwanese spacecraft and potentially attracting customers for future missions. Read our full story.

1955 GMT (3:55 p.m. EDT)

The Taurus rocket successfully carried out its mission today, putting the ROCSAT 2 spacecraft into the correct orbit.

"We are very pleased with the results of the Taurus launch and wish our customers from Taiwan's National Space Programs Office the very best with their satellite mission," said Ron Grabe, Orbital's executive vice president and general manager of its Launch Systems Group.

"Today's successful launch sets the stage for Orbital's continued support for the ROCSAT program. As the prime contractor for the upcoming ROCSAT 3 constellation of six small satellites, as well as the launch vehicle provider for that mission, we look forward to contributing to the continued success of the National Space Program Office's space missions."

This was the seventh Taurus mission and represented the vehicle family's return-to-flight after a failure in September 2001.

The next Taurus currently on the schedule will carry NASA's Orbiting Carbon Observer in August 2007 from Vandenberg.

1830 GMT (2:30 p.m. EDT)

All appears to have gone well during today's maiden flight of the Taurus XL rocket carrying the ROCSAT 2 spacecraft for Taiwan. Data is being examined, and Orbital Sciences is expected to release a statement this afternoon that would declare the launch successful.

1818 GMT (2:18 p.m. EDT)

T+plus 31 minutes. The McMurdo tracking station in Antarctica has picked up signals from both the ROCSAT 2 spacecraft and the spent fourth stage rocket motor as they fly overhead. The fourth stage was designed to record data during flight for playback over McMurdo.

1804 GMT (2:04 p.m. EDT)

T+plus 17 minutes, 30 seconds. The ROCSAT 2 spacecraft has been delivered into an orbit with an apogee of 743.31 km, perigee of 729.94 km and inclination of 99.096 degrees, according to the launch team.

The satellite is scheduled to remain in this initial orbit for a few days before boosting itself into an operational orbit 891 km above Earth.

1802 GMT (2:02 p.m. EDT)

T+plus 15 minutes, 30 seconds. Today's official liftoff time was 1747:03.310 GMT.

1801 GMT (2:01 p.m. EDT)

T+plus 14 minutes, 12 seconds. SPACECRAFT SEPARATION! Taiwan's ROCSAT 2 satellite has been deployed from the Orbital Sciences Taurus XL rocket!

1800 GMT (2:00 p.m. EDT)

T+plus 13 minutes, 40 seconds. Power system remains normal.

1800 GMT (2:00 p.m. EDT)

T+plus 13 minutes, 17 seconds. The vehicle is now aligned for payload release.

1759 GMT (1:59 p.m. EDT)

T+plus 12 minutes, 35 seconds. The fourth stage is maneuvering to the satellite deployment position.

1759 GMT (1:59 p.m. EDT)

T+plus 12 minutes, 14 seconds. The Taurus rocket's upper stage has finished its firing, completing the powered phase of today's launch.

1758 GMT (1:58 p.m. EDT)

T+plus 11 minutes, 40 seconds. The rocket's attitude remains normal.

1758 GMT (1:58 p.m. EDT)

T+plus 11 minutes, 20 seconds. Motor pressure is reported normal as the fourth stage continues to burn.

1758 GMT (1:58 p.m. EDT)

T+plus 11 minutes, 3 seconds. Fourth stage ignition is confirmed.

1757 GMT (1:57 p.m. EDT)

T+plus 10 minutes, 35 seconds. Altitude 700 km.

1756 GMT (1:56 p.m. EDT)

T+plus 9 minutes, 50 seconds. The rocket has positioned itself to the fourth stage ignition orientation as planned.

1755 GMT (1:55 p.m. EDT)

T+plus 8 minutes, 20 seconds. The rocket is passing an altitude of 600 km.

1754 GMT (1:54 p.m. EDT)

T+plus 7 minutes, 50 seconds. The vehicle orientation is correct. It will be maneuvering to the fourth stage ignition attitude shortly.

1754 GMT (1:54 p.m. EDT)

T+plus 7 minutes, 5 seconds. The power system remains normal.

1753 GMT (1:53 p.m. EDT)

T+plus 6 minutes. Orbital reports that all systems are operating normally. Ignition of the fourth stage is expected at about T+plus 11 minutes, 3 seconds.

1752 GMT (1:52 p.m. EDT)

T+plus 5 minutes, 30 seconds. The spent third stage has been jettisoned as the vehicle continues the coast phase.

1751 GMT (1:51 p.m. EDT)

T+plus 4 minutes, 30 seconds. The third stage has burned out. The Taurus rocket is now in a brief coast period.

1750 GMT (1:50 p.m. EDT)

T+plus 3 minutes, 55 seconds. The downrange P-3 tracking aircraft has acquired the rocket's signal for data relay to Vandenberg.

1750 GMT (1:50 p.m. EDT)

T+plus 3 minutes, 30 seconds. The vehicle's attitude is stable during the third stage burn.

1750 GMT (1:50 p.m. EDT)

T+plus 3 minutes, 10 seconds. With the Taurus' nose cone enclosing the ROCSAT 2 satellite during atmospheric ascent no longer needed, the fairing has been jettisoned.

1749 GMT (1:49 p.m. EDT)

T+plus 2 minutes, 55 seconds. The rocket's second stage has burned out and separated. Ignition of the third stage is confirmed.

1749 GMT (1:49 p.m. EDT)

T+plus 2 minutes. The rocket is stable as the second stage burn continues.

1748 GMT (1:48 p.m. EDT)

T+plus 1 minute, 30 seconds. The rocket's second stage has ignited and the spent first stage has separated to fall into the Pacific Ocean.

1747 GMT (1:47 p.m. EDT)

T+plus 30 seconds. The rocket has maneuvered to the proper southerly heading for the trek to polar orbit. Attitude is normal.

1747 GMT (1:47 p.m. EDT)

LIFTOFF! Liftoff of the inaugural Orbital Sciences Taurus XL rocket and the ROCSAT 2 spacecraft for Taiwan.

1746 GMT (1:46 p.m. EDT)

T-minus 30 seconds. All remains "go" for launch.

1746 GMT (1:46 p.m. EDT)

T-minus 1 minute and counting.

1745 GMT (1:45 p.m. EDT)

T-minus 90 seconds.

1745 GMT (1:45 p.m. EDT)

T-minus 2 minutes and counting. Auto sequence start. The countdown is under computer control.

1743 GMT (1:43 p.m. EDT)

T-minus 3 minutes, 15 seconds. Final arming of the rocket has been performed.

1742 GMT (1:42 p.m. EDT)

T-minus 4 minutes, 25 seconds. The launch team polls have been completed with a "final clear to launch" announced.

1742 GMT (1:42 p.m. EDT)

T-minus 5 minutes and counting. The rocket's rate gyro guidance system has been started.

1741 GMT (1:41 p.m. EDT)

T-minus 6 minutes and counting. The S-band data transmitters have been turned on. Telemetry is now being received.

1739 GMT (1:39 p.m. EDT)

T-minus 8 minutes and counting. The Taurus rocket's avoinics have gone to internal power for launch.

1737 GMT (1:37 p.m. EDT)

T-minus 10 minutes and counting. In a few moments, the launch team will be polled to give approval for switching Taurus' avionics to internal power.

1734 GMT (1:34 p.m. EDT)

The trickle charge of the ROCSAT 2 spacecraft batteries is being terminated.

1733 GMT (1:33 p.m. EDT)

Checks of the flight termination system have been conducted successfully.

1732 GMT (1:32 p.m. EDT)

T-minus 15 minutes and counting. The flight termination system is switching to internal power.

1727 GMT (1:27 p.m. EDT)

T-minus 20 minutes.

1723 GMT (1:23 p.m. EDT)

T-minus 24 minutes and counting. The launch team has been given a "go" to power on the rocket's flight termination system. The FTS would be used to destroy the Taurus in the event of mishap during launch today.

1717 GMT (1:17 p.m. EDT)

T-minus 30 minutes and counting. The countdown is progressing for an on-time launch of the Taurus XL rocket from the Space Launch Complex 576E pad at Vandenberg Air Force Base in California.

1712 GMT (1:12 p.m. EDT)

Upper level winds have been confirmed acceptable for the Taurus rocket's ascent today.

1706 GMT (1:06 p.m. EDT)

The Western Range reports the final assessment of toxics and debris predictions are "go" for launch. These predictions are made to ensure public safety if a launch accident were to occur today.

1704 GMT (1:04 p.m. EDT)

T-minus 43 minutes and counting. The launch weather officer has just provided an update to management. All conditions are acceptable and there are no concerns today.

1649 GMT (12:49 p.m. EDT)

Alignment of the Taurus rocket's guidance computer is beginning.

1648 GMT (12:48 p.m. EDT)

A readiness poll of the launch management team has been performed. All systems remain "go" for today's liftoff.

1647 GMT (12:47 p.m. EDT)

T-minus 60 minutes and counting. One hour is remaining until the launch of Orbital's first Taurus XL booster that sports a larger second and third stage to increase the amount of cargo carried into orbit.

1640 GMT (12:40 p.m. EDT)

Avionics just switched from ground-fed power to internal power for a few moments so the launch team could verify voltage and currents. No problems with the power system were noted.

1633 GMT (12:33 p.m. EDT)

The Range has successfully completed the C-band tracking beacon checks as the countdown continues on schedule this morning at Vandenberg.

1627 GMT (12:27 p.m. EDT)

T-minus 80 minutes and counting. Launch of the Taurus rocket remains targeted for 1747:02 GMT (1:47:02 p.m. EDT).

1617 GMT (12:17 p.m. EDT)

T-minus 90 minutes and counting. The Western Range is conducting interrogation checks of the tracking and data links to the rocket.

1614 GMT (12:14 p.m. EDT)

The launch team is verifying the receipt of telemetry from the vehicle at the launch control centers.

1612 GMT (12:12 p.m. EDT)

The rocket's avionics have been powered up and the flight computer is booting.

1547 GMT (11:47 a.m. EDT)

The countdown is entering the final two hours for today's launch of the Taurus rocket from Vandenberg Air Force Base in California -- a site located about 140 miles northwest of Los Angeles along the Pacific coastline.

Last-minute activities are underway at the launch pad before workers clear the hazard area.

This is a solid-propellant vehicle. So no fueling operations are conducted during the countdown like other rocket launches.

0401 GMT (12:01 a.m. EDT)

A new, more powerful version of Orbital Sciences' Taurus rocket makes its maiden flight today carrying a research spacecraft designed to study the environment around Taiwan.

Liftoff the Taurus XL booster from pad 576-East at California's Vandenberg Air Force is scheduled for 1747:02 GMT (1:47:02 p.m. EDT). The day's launch window extends to 1810:19 GMT (2:10:19 p.m. EDT).

"Thankfully we are not working any more issues. We completed the last one, I guess it was late last week. As far as the vehicle goes it is in great shape right now," Bill Wrobel, Orbital's Taurus program manager, said in an interview Wednesday.

"I just came from the site, we're doing final arming of the vehicle now so that by tomorrow morning the only thing that has to be done is a couple of last pins have to be pulled and pull our folks back from the site and we're ready to go."

Air Force meteorologists say there is a 100 percent chance of favorable weather during the launch window.

"The upper level low centered over Northern California dominates the weather pattern on launch day with a positively tilted trough preventing the formation of clouds, aiding in safe conditions for launch," launch weather officer Lt. Breea Lemm reported Wednesday.

"At the surface, expect a weak marine layer to set up in the early morning hours over Vandenberg, dissipating an hour or two prior to launch with a small amount of lingering stratus in the lower levels.

"Surface winds out of the northwest, with a tight gradient pushing the winds at 576E to 10-15 knots, well below the Launch Agency constraint of 43 knots.

"Upper level winds on launch day will be from the west-northwest, reaching a maximum of 65 knots near 40,000 feet."

The four-stage launcher will follow a southerly trajectory from its Central California launch pad, delivering the ROCSAT 2 cargo into 723 km circular orbit inclined 99.1 degrees to the equator about 14 minutes after liftoff.

Built by Astrium of France, ROCSAT 2 is the second Earth observation satellite for the Taiwanese National Space Program Office. The craft's mission is collecting data about the land and marine health on Taiwan and surrounding waters. An instrument to examine lightning in the upper atmosphere is also aboard.

Today's launch marks the return-to-flight of the Taurus vehicle family. A mission in September 2001 was doomed when a steering mechanism on the second stage motor jammed at ignition.

"That caused us to do a loop which basically we lost a significant amount of energy and we couldn't achieve orbit," Wrobel said.

The system freed itself and the rocket regained control. But the incident robbed the rocket of its speed, preventing it from reaching a stable orbit for two satellite cargos carried aboard. The craft reentered the atmosphere before completing an orbit of Earth.

To correct the problem, the steering system has been redesigned with help from the Ground-based Midcourse Defense Segment missile program.

"We basically borrowed that technology and we incorporated it into our vehicle. It's an identical set of actuators," Wrobel said.

"That obviously has a flight heritage history at this point and its been through full qualification. So we're feeling pretty good about it."

Watch this page for updates during today's launch!