BY JUSTIN RAY

June 7, 2000 -- Follow the countdown and launch of Orbital Sciences' Pegasus rocket with the TSX-5 experimental satellite for the U.S. Air Force. Reload this page for the very latest on the mission.

1424 GMT (10:24 a.m. EDT)

CONTACT WITH TSX-5! Ground controllers have successfully acquired the signal from the Tri-Service Experiments Mission-5 satellite, confirming the craft is alive following its journey into space today. Air Force officials report the solar arrays are deployed and controllers are commanding the spacecraft.

Today's successful launch marks the 15th straight for an Orbital Sciences Pegasus rocket and 26th out of the 29 flights made in the vehicle's 10-year history. The next Pegasus is scheduled for July to place NASA's HETE-2 satellite into orbit.

1353 GMT (9:53 a.m. EDT)

Orbital Sciences' L-1011 carrier aircraft has just landed back at Vandenberg Air Force Base following today's successful launch. We are awaiting word on the health of the Air Force's TSX-5 spacecraft, which will pass over the Diego Garcia tracking station at 1414 GMT (10:14 a.m. EDT).

1337 GMT (9:37 a.m. EDT)

The preliminary orbit data has been announced and officials report the Pegasus rocket has deployed the Air Force's TSX-5 spacecraft into an acceptable orbit. The apogee, or high point, is 1706.58 km; a perigee, or low point, of 407.0 km; and inclination of 68.98 degrees.

TSX-5 mission manager Capt. Kevin Benedict gives this overview of what should be happening with the satellite:

"After separation of the spacecraft from the rocket, we go through a sequence that deploys the solar arrays immediately. Unfortunately, we're not able to see that exactly because we do not have ground stations that is capable of picking that up. Our first look at it will be approximately 55 minutes after launch we will go over Diego Garcia tracking station, which is part of the Air Force Satellite Control Network. At that time, we should be able to see the satellite, the solar arrays should be deployed, the satellite goes through its boot-up sequence and it is basically waiting there for commands.

"Our Launch and Early Orbit period is approximately four days long -- about 65 hours. With that we take a methodical step of bringing the satellite up, checking out all the systems, making sure everything is operating correctly. Once that is done, we go into our what we call our experiment checkout and that is when we turning on all the major experiments and checking those out, which takes approximately between 15 and 30 days. So at Launch+35 to 45 days, we will actually start operating the experiments."

Meanwhile, the L-1011 carrier aircraft is now heading back to Vandenberg Air Force Base. Also, the first stage has impacted the Pacific Ocean and a boat will be dispatched in a few hours to recover the pieces, the launch team reports.

We will next update once ground controllers establish contact with TSX-5.

1334:06 GMT (9:34:06 a.m. EDT)

T+plus 14 minutes, 36 seconds. SPACECRAFT SEPARATION! The Pegasus rocket has deployed the TSX-5 spacecraft following this morning's apparent successful launch.

1333:04 GMT (9:33:04 a.m. EDT)

T+plus 13 minutes, 34 seconds. The third stage has burned out and the rocket is about to reorient for spacecraft deployment.

1332 GMT (9:32 a.m. EDT)

T+plus 12 minutes, 30 seconds. The second stage has separated and third stage ignition confirmed.

1330:30 GMT (9:30:30 a.m. EDT)

T+plus 11 minutes. An ARIA aircraft is now taking data from the rocket and relaying it to Vandenberg. The rocket is now reaching the high point of its transfer orbit.

1329 GMT (9:29 a.m. EDT)

T+plus 9 minutes, 30 seconds. Pegasus' power systems and attitude remains steady.

1328 GMT (9:28 a.m. EDT)

The launch team reports the spent first stage is breaking apart as it falls to the Pacific Ocean.

1327 GMT (9:27 a.m. EDT)

T+plus 7 minutes, 30 seconds. Just under five minutes remaining in the coast period this morning.

1326 GMT (9:26 a.m. EDT)

T+plus 6 minutes, 30 seconds. A very smooth flight of the Pegasus rocket reported so far. The preliminary orbit data looks very accurate to the pre-flight predictions.

1324:20 GMT (9:24:20 a.m. EDT)

The Pegasus rocket has completed its calculation of the third stage ignition time at T+plus 12 minutes, 25.2 seconds based on performance.

1322:15 GMT (9:22:15 a.m. EDT)

T+plus 2 minute, 45 seconds. The second stage has burned out after a good firing. Also, the payload fairing has been jettisoned. The vehicle is now in a 10-minute coast period.

1321:15 GMT (9:21:15 a.m. EDT)

T+plus 1 minute, 45 seconds. Second stage ignition. Solid-fueled motor burning well.

1320:53 GMT (9:20:53 a.m. EDT)

T+plus 1 minute, 23 seconds.First stage has burned out; standing by for staging.

1320:10 GMT (9:20:10 a.m. EDT)

T+plus 40 seconds. Vehicle is quickly accelerating with all systems performing normally.

1319:35 GMT (9:19:35 a.m. EDT)

IGNITION. The Pegasus rocket's first stage has ignited and the U.S. Air Force's TSX-5 research satellite is on its way to space to test cutting edge imaging and laser communications technologies.

1319:30 GMT (9:19:30 a.m. EDT)

DROP. Pegasus is away. Standing by for ignition.

1318:48 GMT (9:18:48 a.m. EDT)

T-minus 30 seconds. The first stage flight control fins have now transferred to battery power. This allowed the fins to undergo a steering test.

1318:18 GMT (9:18:18 a.m. EDT)

T-minus 1 minute and counting.

1317:48 GMT (9:17:48 a.m. EDT)

T-minus 90 seconds. Speed of the L-1011 jet is now acceptable.

1317:18 GMT (9:17:18 a.m. EDT)

T-minus 2 minutes. The L-1011 carrier aircraft is descending slightly to gain an extra five feet per second in velocity. Also the data charts are recording.

1316:18 GMT (9:16:18 a.m. EDT)

T-minus 3 minutes. The transient power bus has gone internal and the Range reports a clear to launch.

1315:18 GMT (9:15:18 a.m. EDT)

T-minus 4 minutes and counting.

1314 GMT (9:14 a.m. EDT)

The Pegasus rocket's avionics are now running on internal power with no problems reported.

1313 GMT (9:13 a.m. EDT)

Standing by to transfer the rocket's avionics to internal power. Launch is now seven minutes away.

1310 GMT (9:10 a.m. EDT)

Launch-minus 10 minutes. Orbital Sciences' air-launched Pegasus rocket will be making its 29th flight today. The vehicle is currently riding a three-year stretch of 14 consecutive successful launches, placing 42 satellites into space.

1309 GMT (9:09 a.m. EDT)

Weather conditions have been verified go for launch, which is now 11 minutes away.

1308 GMT (9:08 a.m. EDT)

Checks of the flight termination system has been completed successfully. The FTS would be used to destroy the Pegasus rocket should a problem arise during the launch.

1305 GMT (9:05 a.m. EDT)

The trickle-charge to the TSX-5 spacecraft has been terminated and a status check of the satellite's systems are all reported normal. Now 15 minutes away from the scheduled launch of the Pegasus rocket off the Central California coastline.

1303 GMT (9:03 a.m. EDT)

The release mechanism that will drop the Pegasus rocket from the L-1011 carrier jet has been armed. Also the rocket's flight termination system has gone to internal power.

1257 GMT (8:57 a.m. EDT)

The crew aboard the L-1011 just reported the weather conditions are the predicted launch point. There was no turbulence or clouds and winds were southwesterly at 93 knots. The aircraft is heading north through the drop box and will make a U-turn and fly southward to align the Pegasus rocket with the desired launch trajectory.

1250 GMT (8:50 a.m. EDT)

Now 30 minutes away from the scheduled drop time when the three-stage Orbital Sciences Pegasus XL rocket is released from L-1011 carrier aircraft.

Capt. Bill Weaver earlier described what is like to fly the Stargazer jet during the launch of a Pegasus booster.

"When we drop the Pegasus, there is a pronounced jolt in the airplane. We can all feel it and hear this. The nose will pitch up...because of the 52,000 pound weight loss."

The actual release of Pegasus will be in the hands of co-pilot Don Moore. He will flip a switch on the center console of the cockpit to drop the rocket.

"When the rocket motor ignites, it should be about 500 feet below the airplane, as that lights and accelerates beneath us, it sounds kind of like a freight train going by," Weaver said.

The plane will make a turn to the left to avoid flying through the exhaust plume from the solid-fueled rocket.

"As soon as we rollout from the turn, the Pegasus should be plainly visible in front of us and below us and then it goes up very steeply. Quite impressive and spectacular," Weaver said.

1237 GMT (8:37 a.m. EDT)

The L-1011 aircraft has now reached cruise altitude, and another status check of the TSX-5 satellite parameters revealed acceptable readings.

1230 GMT (8:30 a.m. EDT)

Stargazer is following a preset flight path in which the aircraft will cruise northward through the 10-mile wide, 40-mile long "drop box" to evaluate weather conditions. The aircraft will then make a U-turn off the Central California coastline and return southward into the box, flying on the proper launch heading to release the winged Pegasus rocket at 1320 GMT (9:20 a.m. EDT) this morning.

1221 GMT (8:21 a.m. EDT)

The "Stargazer" carrier aircraft with the Pegasus rocket attached to its belly has departed Vandenberg Air Force Base in California for this morning's sunrise launch to place a military research satellite into orbit. The jet is headed for the "drop box" where the Pegasus will be released, located 60 miles west of Monterey over the Pacific Ocean.

1220:33 GMT (8:20:33 a.m. EDT)

The L-1011 is now rolling down the runway.

1218 GMT (8:18 a.m. EDT)

The ground launch team just been polled and all parties are "go" for takeoff of the L-1011 carrier aircraft in three minutes from Vandenberg Air Force Base, Calif.

1200 GMT (8:00 a.m. EDT)

The Launch Conductor has just announced the current target drop time for the Pegasus rocket today, as well as other adjustments to the pre-launch timeline. Countdown clocks will resume from the built-in hold at 1209 GMT (8:09 a.m. EDT), followed by takeoff of the L-1011 at 1221 GMT (8:21 a.m. EDT) and launch of the Pegasus at 1320 GMT (9:20 a.m. EDT).

1150 GMT (7:50 a.m. EDT)

The payload officer just reported all telemetry parameters coming from the TSX-5 spacecraft are within limits as the countdown remains in a planned built-in hold.

1120 GMT (7:20 a.m. EDT)

Countdown activities are proceeding at Vandenberg Air Force Base in California for this morning's sunrise launch of a Pegasus rocket carrying the TSX-5 experimental test satellite. Departure of the L-1011 aircraft is less than one hour away and the air-launched Pegasus is scheduled to be set free in just under two hours.

Currently senior members of the launch team are conducting voice checks on the various communications channels to be used today.

0830 GMT (4:30 a.m. EDT)

Launch operations are scheduled to get underway at this time for today's planned flight of the Pegasus XL rocket. The launch team will be reporting on station at Vandenberg Air Force Base in California to begin final pre-flight activities to prepare the L-1011 carrier jet and Pegasus rocket for takeoff at 1207 GMT today (5:07 a.m. local; 8:07 a.m. EDT). Launch is scheduled for exactly one hour later.

With about 3 1/2 hours until the "Stargazer" aircraft departs Vandenberg, bound for the launch zone over the Pacific Ocean, the Launch Panel Operator will now board the jet at the Hot Pad staging area. The LPO will power up the Pegasus rocket under direction from the Launch Conductor.

While that chore is underway, efforts to close out the Pegasus' access compartments will be finished and Range Safety engineers are scheduled to verify that the Flight Termination System is functioning by sending arm and fire commands to the FTS antennas.

Later this morning other tests will be conducted to ensure the readiness of Pegasus systems. The checks will include verifying the rocket can switch from aircraft-supplied power to its own internal batteries, the Inertial Measurement Unit guidance computer, the Pegasus' flight computer and telemetry system are working normally and testing the control link from the LPO to the payload.

Activities will culminate with the team members opening their launch checklist and starting the carrier jet's engines in the final hour prior to takeoff. Also, the FTS will be powered on and all safety inhibits checked, the Safe and Arm safing pins removed and the rocket placed in a ready state. Shortly before departure, the L-1011 will taxi from the Hot Pad to the runway.

Weather forecasters are calling for a 70 percent chance of acceptable conditions for the launch today. The concerns to watch will be low ceiling/visibility problems, turbulence and layered clouds. Air Force Launch Weather Officer Capt. Joseph Kurtz gave this overview on Tuesday afternoon:

A broad upper-level trough continues to deepen off the west coast of the U.S. The trough will move to the east into the drop box over the next 24 to 48 hours. As this system moves east, the drop box will see increasing layered clouds. Precipitation associated with the system will move into the box about 12 hours after launch. Locally, the marine layer continues to be a thorn in our side, as Vandenberg was about the only area along the central coast that saw low clouds and fog. Expect the marine layer to remain in place on Wednesday morning, although we may see some improvement in ceiling and visibility. Above the marine layer in the Vandenberg area we will have scattered clouds. Flight level winds will increase to between 75 and 85 knots from the southwest, which could cause some turbulence in the drop area.

In the drop box, at an altitude of 39,000 feet over the Pacific some 60 miles west of Monterey, conditions are forecast to include stratus clouds at 1,000 feet, altocumulus clouds at 10,000 feet and cirrus clouds at 24,000 feet, unrestricted visibility, flight level winds of 75 to 85 knots from the southwest and light turbulence.

TUESDAY, JUNE 6, 2000
1830 GMT (2:30 p.m. EDT)

A Pegasus rocket has been given a green light for launch on Wednesday morning to loft a U.S. Air Force research satellite into space. The mission -- the 29th for the air-launched Pegasus -- will be staged from Vandenberg Air Force Base in California.

Just after 5 a.m. local time (8 a.m. EDT; 1200 GMT), the L-1011 carrier aircraft will take off from Vandenberg bound for the predetermined launch zone 60 miles west of Monterey over the Pacific Ocean. Release of the rocket from the belly of the "Stargazer" jet is expected at 6:07 a.m. local time (9:07 a.m. EDT; 1307 GMT).

The available launch window extends from 6:02 to 6:57 a.m. local time (9:02 to 9:57 a.m. EDT; 1302-1357 GMT).

It will take the three-stage Pegasus some 14 minutes and 32 seconds to inject the Tri-Service Experiments Mission-5 satellite into a highly elliptical orbit inclined 69 degrees around Earth. The launch azimuth will be 154.2 degrees.

Spaceflight Now will provide extensive live reports throughout the final hour of the countdown and the launch on Wednesday. Return to this page for the coverage.

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

Orbital Sciences hopes to launch its Pegasus XL rocket on Wednesday, one day later than planned, if additional testing resolves a concern noted with the vehicle's avionics. An earlier test shows a low power reading, spokesman Barry Beneski says, forcing technicians to conduct further examinations before clearing the air-launched rocket for flight.

Officials will review the situation later today at Vandenberg Air Force Base in California where the launch will originate.

Wednesday's available launch window will extend from 6:02 to 6:57 a.m. local time (9:02 to 9:57 a.m. EDT; 1302-1357 GMT). Release of the Pegasus from the L-1011 carrier aircraft is targeted to occur within the window at 6:07:00 a.m. local (9:07:00 a.m. EDT; 1307:00 GMT).

Launch Weather Officer Capt. Joseph Kurtz says there will be a 70 percent chance of acceptable conditions. The weather threats will be layered clouds, turbulence and avoiding cumulus clouds.

A weather disturbance is forecast to move toward the drop box early this week and the area will see increasing layered clouds and a chance for isolated rainshowers, Kurtz said. The jet stream will also move into the box and winds at flight level will be 95 knots from the southwest, which could cause some turbulence.

MONDAY, JUNE 5, 2000
1937 GMT (3:37 p.m. EDT)

LAUNCH DELAYED! Tuesday's planned launch of an Orbital Sciences Pegasus XL rocket has been postponed due to a technical problem. Officials say a low power reading detected over the weekend from the rocket's avionics system will require more time to review, forcing a one-day delay.

"We are taking more time to understand it and then we will be ready to go," Orbital Sciences spokesman Barry Beneski said.

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

A small but cutting-edge military research satellite is awaiting its dawn launch on Tuesday aboard an Orbital Sciences Pegasus XL rocket. The Tri-Service Experiments Mission-5 will be carried into a highly elliptical orbit around Earth in a 14 1/2-minute flight of the air-launched Pegasus.

Activities are reported to be on track for the launch, which will be staged from Vandenberg Air Force Base in California.

The L-1011 carrier aircraft -- called "Stargazer" -- arrived at Vandenberg on Thursday. A four-hour operations rehearsal was successfully completed on Friday night.

On Saturday morning, the three-stage solid-fueled Pegasus rocket was rolled atop a mobile transport trailer from its processing facility -- Vandenberg's Building 1555 -- to the "hotpad" a few miles away to join the L-1011. Mating between the two occurred at around 8:30 a.m. local time with no significant problems.

The Combined Systems Test to verify the electrical and mechanical connections between Pegasus and Stargazer was scheduled for Sunday; and the final launch readiness meeting is planned this morning.

Satellite technicians will begin arriving at the launch site just after midnight local time (3 a.m. EDT; 0700 GMT) on Tuesday morning to begin last-minute preparations. Their work will include transferring the spacecraft from ground power to a trickle-charge and unhooking the umbilical cord leading to the satellite in advance of the L-1011 heading to the runway for takeoff.

The launch team will begin reporting on station about an hour later and Launch Operations should start at 1:30 a.m. local (4:30 a.m. EDT; 0830 GMT).

If all remains in readiness, the L-1011 will depart Vandenberg at 5:07 a.m. local (8:07 a.m. EDT; 1207 GMT) bound for the "drop box" about 60 miles west of Monterey, Calif., over the Pacific Ocean.

Tuesday's available launch window extends from 5:57 to 6:55 a.m. local (8:57 to 9:55 a.m. EDT; 1257-1355 GMT). However, officials are targeting 6:07:00 a.m. local (9:07:00 a.m. EDT; 1307:00 GMT) for drop of Pegasus, said Capt. Kevin Benedict, the TSX-5 mission manager.

Read our launch preview story for more details on the TSX-5 satellite and its $85 million multi-nation research mission.