BY JUSTIN RAY

Follow the countdown and launch of the Orbital Sciences Minotaur rocket with the U.S. Air Force's XSS-11 technology demonstration satellite. Reload this page for the very latest on the mission.

MONDAY, APRIL 11, 2005
1539 GMT (11:39 a.m. EDT)

Deploying tiny probes to inspect or service spacecraft in distress and flying satellites that can operate with limited human touch are the chief goals behind a state-of-the-art technology demonstration mission successfully launched into Earth orbit this morning. Read our full story.

1415 GMT (10:15 a.m. EDT)

T+plus 40 minutes. There has been no further word on the McMurdo communications pass. Spacecraft mission managers had cautioned before the launch that it could be 100 minutes after liftoff before data would be available to confirm a good release of XSS-11 from the Minotaur fourth stage.

1350 GMT (9:50 a.m. EDT)

T+plus 15 minutes. Engineers are hoping that the McMurdo tracking station in Antarctica will pick up the rocket's telemetry in about 20 minutes to potentially confirm spacecraft separation from the launch vehicle.

We will post confirmation of a successful launch outcome as soon as officials make that announcement.

1349 GMT (9:49 a.m. EDT)

T+plus 14 minutes. LOS of data. The rocket has passed out of range from the tracking station at Vandenberg as expected. It could be almost two hours before controllers acquire signal from the XSS-11 spacecraft to determine a successful separation from the fourth stage motor.

1347 GMT (9:47 a.m. EDT)

T+plus 12 minutes, 25 seconds. The launch team computes that the orbit achieved is on target.

1346 GMT (9:46 a.m. EDT)

T+plus 11 minutes, 50 seconds. Thrust is tailing off from the solid-fueled fourth stage.

1346 GMT (9:46 a.m. EDT)

T+plus 11 minutes, 22 seconds. All systems appear normal as fourth stage continues to burn.

1345 GMT (9:45 a.m. EDT)

T+plus 10 minutes, 43 seconds. Fourth stage stage ignition with normal pressures reported.

1345 GMT (9:45 a.m. EDT)

T+plus 10 minutes, 30 seconds. The third stage has been jettisoned from the fourth stage. Coming up on ignition of the fourth stage.

1343 GMT (9:43 a.m. EDT)

T+plus 8 minutes, 45 seconds. Rocket health status is still looking normal.

1342 GMT (9:42 a.m. EDT)

T+plus 7 minutes. The rocket is coasting to the high point of its initial suborbital trajectory achieved to this point in the launch. Once at apogee in a few minutes, the spent third stage will separate and the fourth stage motor will ignite to circularize the orbit for deployment of XSS-11.

1341 GMT (9:41 a.m. EDT)

T+plus 6 minutes. The vehicle's systems remain in good shape.

1339 GMT (9:39 a.m. EDT)

T+plus 4 minutes, 45 seconds. The Minotaur remains on course. Performance so far in this launch indicates the target apogee altitude high point will be reached.

1338 GMT (9:38 a.m. EDT)

T+plus 3 minutes, 30 seconds. The solid-fuel third stage has burned out, and the rocket is now in a brief coast period.

1338 GMT (9:38 a.m. EDT)

T+plus 3 minutes. Third stage solid motor continues to fire. All appears normal.

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

T+plus 2 minutes, 27 seconds. The rocket's payload fairing nose cone has separated.

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

T+plus 2 minutes, 17 seconds. Third stage ignition confirmed as the spent second stage falls way. This sheds the Minuteman 2 portion of Minotaur and the Pegasus heritage takes over.

1336 GMT (9:36 a.m. EDT)

T+plus 1 minute, 45 seconds. The rocket's attitude and orientation are correct.

1336 GMT (9:36 a.m. EDT)

T+plus 80 seconds. Second stage performing as expected as the Minotaur soars into the early morning sky.

1336 GMT (9:36 a.m. EDT)

T+plus 67 seconds. The first and second stages have separated. Second stage has ignited.

1335 GMT (9:35 a.m. EDT)

T+plus 45 seconds. Attitude is normal as the vehicle passed through maximum dynamic pressures.

1335 GMT (9:35 a.m. EDT)

T+plus 25 seconds. System status is normal.

1335 GMT (9:35 a.m. EDT)

T+plus 10 seconds. First stage motor pressure nominal.

1335 GMT (9:35 a.m. EDT)

LIFTOFF! Liftoff of the Minotaur rocket launching the Air Force Research Laboratory's Experimental Satellite System-11 spacecraft to demonstrate new autonomous satellite features in Earth orbit.

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

T-minus 1 minute.

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

T-minus 90 seconds. The rocket ordnance has been armed.

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

T-minus 2 minutes. Auto sequence start. Flight computer is controlling the countdown.

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

T-minus 2 minutes, 30 seconds. Coming up on auto sequence start in 30 seconds.

1331 GMT (9:31 a.m. EDT)

T-minus 3 minutes, 15 seconds. The Air Force-controlled Western Range is clear for launch.

1331 GMT (9:31 a.m. EDT)

T-minus 3 minutes, 40 seconds. The air conditioning duct to the rocket's payload fairing has been retracted.

1331 GMT (9:31 a.m. EDT)

T-minus 4 minutes. The flight computer is armed. Also, the C-band tracking beacon is working normally on interal power.

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

T-minus 5 minutes. The rocket's avionics are switching to internal power.

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

T-minus 6 minutes. The final management poll is now complete and no problems are standing in the way of liftoff.

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

T-minus 6 minutes, 45 seconds. The XSS-11 spacecraft has been declared "go" for launch.

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

T-minus 8 minutes, 30 seconds. The flight termination system is now armed.

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

T-minus 9 minutes. The rocket's flight termination system is switching to interal power. The FTS would be used to destroy the rocket should a problem arise during flight.

1325 GMT (9:25 a.m. EDT)

T-minus 10 minutes and counting. Experimental Satellite System-11 spacecraft has gone to internal battery power for launch.

1323 GMT (9:23 a.m. EDT)

T-minus 12 minutes. The launch time is being set in the rocket's flight computer.

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

T-minus 13 minutes. Removal of the thermal blanket covering the Minotaur rocket's Minuteman stages has been completed. This cover is affectionately called the "banana" because of its color and since it's peeled away in sections.

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

T-minus 14 minutes. Safety officials confirm that the hazard area and impact zones are clear for launch.

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

T-minus 15 minutes. The final launch readiness poll was just conducted of various team members. There are no problems being reported with the Minotaur rocket, XSS-11 spacecraft or Western Range.

The "go" has be given to start removing the thermal blanket covering the bottom half of the rocket. This operation is being performed remotely without workers at the pad thanks to an automatic device.

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

T-minus 19 minutes. Minotaur remains set to go at 1335 GMT.

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

T-minus 20 minutes. As dawn begins to break, the news media has moved to another viewing site because of the fog and low clouds hanging over Vandenberg. The reporters and photographers are now 13 miles from the pad in hopes of getting a bit better view of the rocket climbing out.

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

T-minus 25 minutes. A safety test of the rocket's flight termination system is starting. This system would be activated to destroy Minotaur if the rocket veered off course or experienced a major problem during launch.

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

T-minus 30 minutes. Initial link tests have been completed between the rocket's tracking beacon and the Western Range.

1255 GMT (8:55 a.m. EDT)

T-minus 40 minutes. About 35 steps in the final launch checklist have been completed thus far. Liftoff remains targeted to occur at 1335 GMT (6:35 a.m. local time; 9:35 a.m. EDT) from Vandenberg Air Force Base, Calif.

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

T-minus 45 minutes and counting. Voltage and current readings from the rocket have been checked and the launch team reports they are normal.

1247 GMT (8:47 a.m. EDT)

The launch pad danger area has been confirmed clear of all personnel.

1246 GMT (8:46 a.m. EDT)

The rocket's guidance system has been aligned without problem.

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

The rocket's avionics are being powered to permit the inertal guidance system pre-launch alignment and test the S-band communications antenna signal strength.

1235 GMT (8:35 a.m. EDT)

T-minus 60 minutes and countdown. Activities are continuing as planned at Vandenberg Air Force Base in California for liftoff of the Minotaur rocket at 1335 GMT. The launch team is opening up the final checklist.

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

A small group of reporters and photographers has gathered at Vandenberg for escort by the Air Force to a launch viewing site about four-and-a-half miles from the pad.

1225 GMT (8:25 a.m. EDT)

T-minus 70 minutes and counting. It is a foggy morning at Vandenberg. However, the reduced visibility is not a constraint for the Minotaur rocket and weather conditions are not expected to violate any launch rules.

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

T-minus 95 minutes and counting. The arming and final closeouts checklist has been completed now that the launch support equipment is powered up. Technicians plan to begin using the final launch checklist at the T-minus 1 hour mark.

1135 GMT (7:35 a.m. EDT)

T-minus 2 hours and counting. Launch support equipment is being powered up.

1128 GMT (7:28 a.m. EDT)

The satellite payload atop the Minotaur rocket has been powered and readied to proceed with this morning's launch operation. Also at this time, clearing of workers in the hazard area around the launch pad has started.

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

Power is being applied to the XSS-11 spacecraft as the countdown continues for today's launch. Liftoff will be possible during a window of 6:34 to 7 a.m. local time (9:34-10 a.m. EDT; 1334-1400 GMT).

1055 GMT (6:55 a.m. EDT)

The Minotaur launch team has begun vehicle arming and final closeouts for today's planned liftoff from Vandenberg Air Force Base, California.

Mission managers have been seated at consoles to oversee the last couple of hours in the countdown, and a readiness poll to initiate the arming was conducted a few minutes ago with no problems reported.

SUNDAY, APRIL 10, 2005

Launch of the Minotaur rocket with XSS-11 remains on schedule for Monday. Officials did not report any technical problems or concerns during an afternoon press conference today. We'll post live updates on this page during the final countdown and throughout the flight.

SATURDAY, APRIL 9, 2005

An experimental U.S. Air Force satellite designed to rendezvous with spent rocket bodies and defunct spacecraft to test autonomous technologies goes into orbit Monday aboard a half-retired missile, half-Pegasus booster.

This third flight of the Orbital Sciences-managed Minotaur rocket program begins from Space Launch Complex 8 positioned on the southern edge of Vandenberg Air Force Base, California. Liftoff will be possible during a 26-minute window extending from 6:34 to 7 a.m. local time (9:34-10 a.m. EDT; 1334-1400 GMT).

Following a five-year hiatus in missions, Minotaur returns to launch the Experimental Satellite System-11 spacecraft for the Air Force Research Laboratory.

"We are really excited here. We are ready to launch," XSS-11 program manager Harold Baker said in an interview Saturday night. "The satellite has been operating great for the last three months; the booster is in good shape. I think everybody here is ready for us to launch."

XSS-11 will perform six or seven encounters with in-space objects over its 12-to-18 month mission to demonstrate rendezvous and autonomous planning concepts, as well as ground tools for operating the $80 million mission.

Such technologies have the potential to aid future projects to service or inspect satellites.

"It will help us to learn more about working in space," Baker said.

The XSS-11 spacecraft was built by Lockheed Martin at its facilities near Denver.

The Minotaur rocket is formed by using decommissioned first and second stages from a Minuteman 2 ICBM missile and solid-fuel motors from Orbital's air-launched Pegasus program for its third and fourth stages. The vehicle is designed to provide the U.S. government with reliable access to space for small satellites.

Also known as the Orbital/Suborbital Program-Space Launch Vehicle, Minotaur had two successful missions in 2000.

Technicians are spending the weekend performing last-minute work in advance of Monday's blastoff.

"Today we did all of our preps. We got the spacecraft in final flight configuration," Baker said. "The launch vehicle closed out all of the remaining discrepancy reports that were on it. We are 'go' for launch on Monday morning."

Monday's weather forecast predicts a 100 percent chance of acceptable conditions for the Minotaur to safely ascend. However, fog and an extremely low cloud ceiling is expected to significantly hamper spectators' view.

"Vandenberg is currently under the influence of an upper level trough centered over Eastern California and progressing eastward. An upper level high pressure ridge is building in from the west and forecast to be over Central California and slightly east of Vandenberg at launch time," Air Force meteorologists reported Saturday.

"At the surface, high pressure will extend from the Eastern Pacific and into the Great Basin area creating a stable atmosphere and favorable weather conditions for launch."

The "marine layer" of low stratus clouds will cover the entire sky at 500 feet with tops at 1,500 feet. Forecasters also predict fog to reduce visibility to two-to-four miles, a temperature between 54 and 59 degrees, ground winds of 10-to-15 knots from the north-northwest and maximum upper level winds of 90 knots near 40,000 feet.

Should the launch be delayed to Tuesday for some reason, the outlook remains 100 percent 'go.'

"The forecast for Tuesday remains much the same as Monday with high pressure dominating Central California," Air Force meteorologists said. "Lower pressure begins moving into the upper levels, but not enough to destabilize the atmosphere. In the low levels, a slight thickening of the marine layer as moisture increases along the coast. Surface winds will be 10-15 knots with visibility again at two-to-four miles in fog. Upper level winds will remain from the west with maximum of 85 knots at 40,000 feet."

Watch this page for live updates during Monday's countdown and launch!