BY JUSTIN RAY

Follow the preparations and launch of the Orbital Sciences Pegasus XL rocket with the Canadian SciSat 1 ozone research spacecraft. Reload this page for the very latest on the mission.

Coverage for subscribers only:
   VIDEO: 11-MINUTE REPLAY OF PEGASUS LAUNCHING SCISAT QT
   VIDEO: POST-FLIGHT COMMENTS FROM NASA LAUNCH MANAGER QT

   VIDEO: PEGASUS XL ROCKET IS ASSEMBLED FOR THIS LAUNCH QT
   VIDEO: FOOTAGE OF SCISAT 1 UNDERGOING PROCESSING AT VAFB QT
   VIDEO: ROCKET'S NOSE CONE INSTALLED AROUND SCISAT 1 QT
   VIDEO: PEGASUS IS ROLLED OUT AND MATED TO CARRIER JET QT
   VIDEO: CARRIER AIRCRAFT TAKES OFF FOR LAUNCH OF PEGASUS QT
   VIDEO: WATCH MONDAY'S PRE-LAUNCH NEWS CONFERENCE QT
   SUBSCRIBE NOW

WEDNESDAY, AUGUST 13, 2003

A Canadian endeavor to study the chemistry of Earth's atmosphere and the fragile ozone layer was successfully propelled into space Tuesday night by an air-launched rocket. Read our full story.

0234 GMT (10:34 p.m. EDT Tues.)

The L-1011 carrier jet has landed following tonight's successful launch of the Pegasus rocket.

We will pause our coverage. Check back later this evening for movies, images and a wrap-up story on the launch of Canada's SciSat 1 spacecraft aboard Orbital Sciences Pegasus XL rocket.

0223 GMT (10:23 p.m. EDT Tues.)

The preliminary data shows that orbit achieved tonight is right on the target. SciSat 1 was deployed into an orbit with a high point of 659.24 km, low point of 648.02 km and inclination of 73.946 degrees to the Equator.

0220 GMT (10:20 p.m. EDT Tues.)

T+plus 10 minutes, 50 seconds. SPACECRAFT SEPARATION! Canada's SciSat 1 satellite has been released into Earth orbit from the Pegasus rocket for its two-year mission to study Earth's ozone layer.

0219 GMT (10:19 p.m. EDT Tues.)

T+plus 10 minutes, 15 seconds. Attitude remains nominal. Coming up on SciSat 1 separation.

0218 GMT (10:18 p.m. EDT Tues.)

T+plus 9 minutes, 15 seconds. The upper stage is now preparing for payload deploy.

0218 GMT (10:18 p.m. EDT Tues.)

T+plus 9 minutes. The third stage has burned out, completing the powered phase of SciSaat 1's launch.

0218 GMT (10:18 p.m. EDT Tues.)

T+plus 8 minutes, 35 seconds. Third stage continues its burn. Attitude is still normal.

0217 GMT (10:17 p.m. EDT Tues.)

T+plus 8 minutes, 10 seconds. The third stage has reached maximum pressure.

0217 GMT (10:17 p.m. EDT Tues.)

T+plus 7 minutes, 45 seconds. The spent second stage has separated. And the solid-fueled third stage motor has ignited, accelerating the SciSat 1 spacecraft to its orbit.

0216 GMT (10:16 p.m. EDT Tues.)

T+plus 7 minutes. Altitude 362 miles.

0216 GMT (10:16 p.m. EDT Tues.)

T+plus 6 minutes, 35 seconds. The vehicle is now reorienting in preparation for stage separation and third stage burn.

0215 GMT (10:15 p.m. EDT Tues.)

T+plus 6 minutes, 10 seconds. The ballistic coast period continues for Pegasus. About 90 seconds remain until third stage ignition.

0214 GMT (10:14 p.m. EDT Tues.)

T+plus 5 minutes. The rocket remains in a normal attitude. The power systems are still strong.

0213 GMT (10:13 p.m. EDT Tues.)

T+plus 4 minutes. Altitude is currently 200 miles.

Third stage ignition is now calculated to occur at approximately T+plus 7 minutes, 35 seconds. The start time based upon the performance of the vehicle's first two stages.

0212 GMT (10:12 p.m. EDT Tues.)

T+plus 3 minutes, 15 seconds. The solid-fueled second stage has burned out. The Pegasus rocket is now in a coast period for the next few minutes. During this time the rocket will compute the performance of the flight thus far and adjust the third stage ignition time if necessary.

0212 GMT (10:12 p.m. EDT Tues.)

T+plus 2 minute, 50 seconds. Altitude 114 miles, velocity 12,500 miles per hour.

0211 GMT (10:11 p.m. EDT Tues.)

T+plus 2 minute, 15 seconds. The two halves of the payload fairing enclosing the SciSat 1 satellite on the end of the Pegasus rocket has been jettisoned. Second stage continues to burn.

0211 GMT (10:11 p.m. EDT Tues.)

T+plus 2 minutes, 10 seconds. The second stage motor has reached maximum pressure.

0211 GMT (10:11 p.m. EDT Tues.)

T+plus 1 minute, 35 seconds. The first stage is jettisoned. The Pegasus' second stage has ignited.

0210 GMT (10:10 p.m. EDT Tues.)

T+plus 1 minute, 18 seconds. The solid-fueled first stage has burned out. The vehicle is now in a ballistic coast for a few seconds before the spent stage is jettisoned and the second stage ignites.

0210 GMT (10:10 p.m. EDT Tues.)

T+60 seconds. Vehicle remains in the proper attitude as the first stage continues to fire.

0210 GMT (10:10 p.m. EDT Tues.)

T+plus 45 seconds. The Pegasus rocket is passing through maximum dynamic pressure. Attitude of the vehicle is reported normal.

0210 GMT (10:10 p.m. EDT Tues.)

T+plus 30 seconds. The Pegasus rocket is pitched up 35 degrees as it climbs into the sky on the power of its solid-fueled first stage motor. No problems reported.

0209 GMT (10:09 p.m. EDT Tues.)

IGNITION. The Pegasus' first stage motor has ignited to launch SciSat 1 -- Canada's contribution to studying the Earth's environment from space.

0209 GMT (10:09 p.m. EDT Tues.)

DROP. The Orbital Sciences Pegasus XL rocket has been released from the L-1011 aircraft off the California coastline.

0208 GMT (10:08 p.m. EDT Tues.)

The batteries for the first stage flight control fins have been activated, allowing the fins to undergo a sweep test prior to launch. The fins are used to steer the rocket during its initial climb to space.

With the batteries activated there is just 90 seconds to launch today or else an abort will be called. That is due to the limited life of the batteries.

In the final moments prior to release of Pegasus, the L-1011 carrier aircraft crew will oversee the last seconds of the countdown and flip the switch that will drop the three-stage vehicle, with the SciSat 1 spacecraft aboard, from the belly of the jet.

0207 GMT (10:07 p.m. EDT Tues.)

Data recorders in the telemetry receiving lab are starting.

Launch is about two minutes away. Drop time will be occurring about a minute early.

0206 GMT (10:06 p.m. EDT Tues.)

The L-1011 aircraft has now entered the "drop box" for releasing the Pegasus rocket. And the launch team confirms the SIGI onboard flight computer is configured.

0206 GMT (10:06 p.m. EDT Tues.)

The transient power bus has switched to internal. Also, the rocket's new SIGI guidance computer is being configured for flight.

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

The launch team has been given a "go" to enter the final phase of the countdown at L-minus 4 minutes.

0204 GMT (10:04 p.m. EDT Tues.)

The Air Force confirms the Range is clear for the launch.

0203 GMT (10:03 p.m. EDT Tues.)

The Pegasus rocket's avionics have switching from power provided by the L-1011 to internal battery power with no problems reported.

0202 GMT (10:02 p.m. EDT Tues.)

NASA Launch Manager Chuck Dovale has polled his team for the "go" to enter terminal count. Launch of Pegasus is just minutes away.

0200 GMT (10:00 p.m. EDT Tues.)

The Air Force launch weather officer confirms conditions are "go."

0157 GMT (9:57 p.m. EDT Tues.)

Checks of the flight termination system have been completed. The Range reports the results were nominal.

NASA says SciSat 1 successfully transitioned to internal power a short time ago.

0155 GMT (9:55 p.m. EDT Tues.)

The flight termination system is now running on internal power. The safety system would be used to destroy the Pegasus rocket in the event a problem during launch.

The L-1011 is currently in the midst of its U-turn to head back toward the south for tonight's launch.

0154 GMT (9:54 p.m. EDT Tues.)

The launch team members report they are ready to switch the rocket's flight termination system to internal power.

0145 GMT (9:45 p.m. EDT Tues.)

The countdown continues for tonight's launch. Mission managers are assessing a telemetry issue relating to the launch controllers' display panels aboard the carrier aircraft. However, this does not appear to be a constraint to proceeding with the mission this evening.

0141 GMT (9:41 p.m. EDT Tues.)

The aircraft is doing a small right turn to head for the planned drop box. The flight path map can be seen here.

0135 GMT (9:35 p.m. EDT Tues.)

Today marks the 35th flight of the air-launched Pegasus rocket and the 25th using the XL version. This will be the fourth Pegasus launch in 2003, the third for NASA.

The next Pegasus is scheduled in early 2004.

Click here to see our coverage of previous Pegasus rocket flights.

0127 GMT (9:27 p.m. EDT Tues.)

After flying westerly from Vandenberg Air Force Base, the carrier jet is now making a right-hand turn to head northward.

0125 GMT (9:25 p.m. EDT Tues.)

A chase plane has intercepted the L-1011/Pegasus duo over the Pacific Ocean. The chase aircraft has an onboard camera to relay live video back to launch officials at Vandenberg Air Force Base.

0120 GMT (9:20 p.m. EDT Tues.)

Now 50 minutes from the scheduled launch of Pegasus.

The air-launched rocket will be released from the L-1011 jet over the Pacific Ocean due west of California's central coast. Weather permitting, the rocket's exhaust should be visible to residents throughout central and southern California as the Pegasus streaks southward on the trek to space.

To see the carrier jet's flight path and the "drop box" in which the Pegasus will be jettisoned from Stargazer, click here.

0113 GMT (9:13 p.m. EDT Tues.)

WHEELS UP. The "Stargazer" carrier aircraft with the Orbital Sciences Pegasus XL rocket has departed Vandenberg Air Force Base in California for tonight's launch to place Canada's SciSat 1 spacecraft into orbit to study Earth's ozone layer.

0112 GMT (9:12 p.m. EDT Tues.)

The L-1011 is rolling down the runway.

0110 GMT (9:10 p.m. EDT Tues.)

A poll of the ground launch team has been completed by the Orbital Sciences launch conductor, confirming all systems are "go" for takeoff of the L-1011 aircraft in about three minutes.

0104 GMT (9:04 p.m. EDT Tues.)

NASA Launch Manager Chuck Dovale has polled the space agency team to verify all is in readiness for takeoff of the L-1011 aircraft. There are no problems being addressed with the Pegasus rocket, SciSat 1 spacecraft, Range or anything else.

The Orbital launch team will be polled a few minutes from now.

0057 GMT (8:57 p.m. EDT Tues.)

The taxi to the runway is now complete. The L-1011 is in position for its departure to launch the Pegasus rocket and SciSat 1 spacecraft tonight.

0050 GMT (8:50 p.m. EDT Tues.)

The Stargazer carrier jet is currently rolling from its staging area to the runway at Vandenberg Air Force Base in preparation for takeoff.

0040 GMT (8:40 p.m. EDT Tues.)

Launch is now 90 minutes away. There are no reports of any problems today as the countdown continues for the 7:10 p.m. PDT (10:10 p.m. EDT; 0210 GMT) drop of the air-launched Pegasus rocket. The carrier aircraft -- with the rocket mounted to its belly -- is slated for takeoff in about 30 minutes.

TUESDAY, AUGUST 12, 2003
2200 GMT (6:00 p.m. EDT)

The countdown activities are beginning at Vandenberg Air Force Base in California for tonight's 7:10 p.m. PDT (10:10 p.m. EDT; 0210 GMT) launch of the SciSat 1 atmospheric science satellite aboard an Orbital Sciences Pegasus XL rocket.

The Pegasus countdown lasts over four hours. It features a series of ground-based events such as final preparations to the payload, performing power tests on the rocket and checking the Range Safety's Flight Termination System.

"With an air-launched system you obviously want to make sure you are fully checked out before you take off," NASA Launch Manager Chuck Dovale said. "So the Pegasus will be powered on, the electrical and guidance systems checked, we will do a Flight Termination System check with the Range and make sure all the (communications) are working."

The L-1011 carrier aircraft will taxi to the runway in a couple of hours. Takeoff it expected around 6:12 p.m. PDT (9:12 p.m. EDT; 0112 GMT). The jet will fly a pre-determined "race track" pattern over the Pacific to reach the proper launch point where Pegasus will be released to roar into orbit.

Today's launch window extends from 7:04 to 8:01 p.m. PDT (10:04-11:01 p.m. EDT; 0204-0301 GMT.

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

Canada's SciSat 1 atmospheric research satellite heads into space tonight aboard Orbital Sciences' air-launched Pegasus XL rocket.

Flying over the Pacific Ocean about 50 miles northwest of Monterey, California, the 50,000-pound rocket will be released from the belly of Orbital's L-1011 carrier jet, named Stargazer, at approximately 7:10 p.m. local time (10:10 p.m. EDT; 0210 GMT).

The mission will begin 58 minutes earlier when Stargazer takes off from Vandenberg Air Force Base bound for the preset launch point. The aircraft will follow a "race track" course, which is illustrated on this map.

The track takes Stargazer through the launch area on a northward heading, allowing the aircraft crew to evaluate weather conditions. The plane then makes a U-turn and returns to the drop point on a southerly trajectory to launch the rocket.

The day's available launch window extends from 7:04:10 to 8:01:26 p.m. Pacific Time (10:04-11:01 p.m. EDT; 0204-0301 GMT). Should a problem occur during the countdown, the window is long enough to support one recycle before the launch would have to be scrubbed. A backup launch opportunity Wednesday night is available on the Western Range.

With the push of a button in the Stargazer's cockpit, the Pegasus rocket is cast free to fall for five seconds, dropping 300 feet below the aircraft. During the plunge, the onboard flight computer will sense the rocket's separation from the carrier jet and issue a command to release the safety inhibits in preparation for ignition.

The first stage solid-fueled motor of Pegasus is lit at T+5 seconds to begin the powered journey to orbit with the SciSat 1 spacecraft.

At T+1 minute, 15 seconds, the Orion 50S XL first stage motor consumes all of its solid-fuel propellant and burns out. A short ballistic coast period begins before the spent first stage is separated to fall into the Pacific Ocean.

A second later, the Pegasus rocket's Orion 50 XL second stage begins firing to continue the trip to orbit. During the firing, at T+2 minutes, 6 seconds, the payload fairing that protected the SciSat 1 satellite during atmospheric ascent is jettisoned.

Having consumed its supply of solid-fuel propellant, the second stage motor burns out at T+2 minutes, 45 seconds. A longer coast period begins before releasing the spent stage at T+plus 7 minutes, 16 seconds.

The solid-fueled Orion 38 third stage ignites at T+plus 7 minutes, 27 seconds to deliver the SciSat 1 spacecraft into the desired highly-inclined orbit around Earth. That circular orbit of 400 miles inclined 73.9 degrees to the Equator is achieved with cutoff of the third stage at T+8 minutes, 38 seconds.

Release of the 330-pound SciSat 1 from the launcher occurs at T+plus 10 minutes, 38 seconds, completing the Pegasus rocket's 35th launch since debuting in 1990.

NASA is managing the launch for Canada's space program under a cooperative arrangement between the two agencies. The launch costs are $21.6 million. The price tag for the SciSat spacecraft, its instruments and two years of mission operations is $40 million.

SciSat 1 will study the chemical processes that control the distribution of ozone in the Earth's atmosphere, particularly at high latitudes.

The primary onboard science instrument is the Fourier Transform Spectrometer, built by ABB of Quebec City. The second instrument is the Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation, or MAESTRO for short. It was built by EMS Technologies of Ottawa.

Watch this page for live updates during today's flight of the Pegasus rocket!

SUNDAY, AUGUST 10, 2003

A Canadian science satellite designed to monitor Earth's ozone layer will soar into Earth orbit Tuesday night aboard an air-launched Pegasus XL rocket dropped from a carrier jet off the coast of California.

The day's available launch window extends from 7:04:10 to 8:01:26 p.m. Pacific Time (10:04:10-11:01:26 p.m. EDT; 0204-0301 GMT).

Release of the Orbital Sciences rocket from the modified L-1011 aircraft is targeted to occur a few minutes into the window while flying about 100 miles west of California's central coast.

The mission originates from Vandenberg Air Force Base, the home port for Pegasus rockets.

Air Force weather forecasters predict an 80 percent chance of acceptable conditions for the mission. Turbulence is the only worry.

"A developing low pressure system forming off the Washington-Oregon coast will move eastward today, moving onshore late Monday afternoon," Launch Weather Officer Capt. Scott Lisko said Sunday.

"This low will bring increasing upper-level winds to central California, both over Vandenberg and at the drop point. These increasing winds are causing slight concern for the turbulence constraint in the drop box, as the jet stream may cause occasional turbulence in the drop area.

"For launch time, Vandenberg will have scattered low-level marine layer clouds, with winds out of the northwest. The flight path to the drop point will be clear, with occasional turbulence possible.

"Maximum upper level winds on launch day will be out of the west at 70-80 knots near 40,000 feet

In the event launch is delayed to Wednesday, the forecast calls for a 90 percent chance of meeting the launch weather rules. Turbulence remains the only concern.

"Weather conditions for a 24-hour slip will remain steady. The low pressure system moving onshore to our north will continue to bring moderate jet stream winds to the area, with marine layer stratus clouds lingering over Vandenberg. Weather conditions should remain favorable, with slight concern for turbulence in the drop box. Upper level winds will remain out of the west, reaching a maximum of 60-70 knots near 40,000 feet."

This will mark the 35th flight for Pegasus since debuting in 1990 and the last of fourth launches scheduled in 2003. The small satellite launcher is currently riding a string of 20 consecutive successful flights since 1997.

The SciSat 1 cargo being deployed Tuesday carries two instruments to measure the concentration and distribution of chemicals, including ozone, in the atmosphere. Scientists hope the data gathered by the satellite will help explain the processes that break down Earth's ozone layer.

We will post a countdown and launch preview Monday evening. And watch this page for live updates throughout the flight on Tuesday night.