BY JUSTIN RAY

January 25, 2000 -- Follow the first launch of the OSPSLV Minotaur rocket with the JAWSAT satellite platform. Reload this page for the very latest on the mission.

TUESDAY, JANUARY 25, 2000
2300 GMT (6:00 p.m. EST)

With a favorable weather forecast in hand, the U.S. Air Force is making final preparations for Wednesday night's launch of its first Orbital Suborbital Program Space Launch Vehicle, nicknamed Minotaur. Liftoff could occur as early as 0303:06 GMT (10:03:06 p.m. EST), the opening of a three-hour window at Vandenberg Air Force Base, California. However, if things go according to expectations, officials will slip the liftoff to 0313:06 GMT (10:13:06 p.m. EST), which is the preferred launch time for one of the onboard payload experiments.

Capt. Eric Barela, the Air Force launch weather officer, predicts an 80 percent chance of acceptable weather with the only concern being layered clouds.

"Charts continue to position high pressure over Vandenberg on day of launch. Expect a decrease in cloud cover, however, surface winds will increase due to a tightening pressure gradient and an intrusion of cooler air. Surface winds will be out of the northwest at 15-25 knots. Upper-level winds will be westerly with a max wind of 75 knots at 40,000 feet."

The launch time forecast calls for 1,000-foot thick deck of scattered stratus clouds at 500 feet and scattered cirrus clouds at 21,000 feet, visibility between 3 and 5 miles, northwesterly winds 15 to 25 knots, a temperature of 50 to 55 degrees F and fog.

If the launch is delayed until Thursday night, which would have a three-hour window opening at 10:03:49 p.m. EST (0303:49 GMT Friday) and preferred liftoff time of 10:13:49 p.m. EST, the forecast calls for a 70 percent chance of good weather. Layered clouds would again be the concern.

Barela: "High pressure moves east as the next system approaches Vandenberg. Expect an increase in mid and upper level clouds. Surface winds will not be as strong as previously thought, expect 15-20 knots out of the northwest. Upper level winds will increase and become more southwesterly at 80-90 knots."

The countdown will begin Wednesday at T-minus 6 hours when the launch team arrives at their consoles. The painter-like scaffolding enclosing the rocket at the Commercial Launch Facility will be retracted no later than T-minus 40 minutes.

Duration of the launch through separation of the final payload will last about 20 minutes. But since the satellite deployments will occur while the rocket is out of range from tracking stations, the data will be recorded and downlinked to a site in Antarctica at about T+plus 35 minutes. Confirmation of a successful flight, which will be based on the rocket achieving orbit, making the correct orbit and deployment of the satellites, is not expected to be announced by the Air Force until approximately 2 1/2 hours after launch. However, information of satellite deployments could come by about T+plus 75 minutes.

We will have comprehensive coverage during the final hours of the countdown and throughout the flight.

0200 GMT (9:00 p.m. EST)

The U.S. Air Force has rescheduled the inaugural flight of its OSP Minotaur rocket for Thursday at 0303 GMT (10:03 p.m. EST Wednesday) from Vandenberg Air Force Base, California. The available launch window is three hours long.

The rocket and its JAWSAT satellite payload has been awaiting a new attempt for liftoff since the first launch try was scrubbed on the night of January 14.

The main problem has been finding new batteries to be installed into rocket's Range Safety destruct system, which would be used to destroy Minotaur if the vehicle's stages accidently separated during launch.

"We knew they were in short supply," said Maj. Steve Buckley, U.S. Air Force launch director.

In the end, the Air Force will use batteries originally slated for use on a later launch.

Over the weekend, engineers tested another batch of batteries, known as Lot No. 18, that now will be used on another Minuteman 2 launch later this year. The batteries that had been slated for that later launch will now be used on the OSP Minotaur rocket, clearing the way for liftoff this week.

"The testing we did this weekend allowed the Range to accept the batteries for an established launch vehicle, which is going to be launched later in the year," said Buckley. "So we were able to use the Lot No. 15 batteries, which have a better track record, on this (OSP Minotaur) rocket."

The new batteries were expected to be installed into OSP Minotaur on Monday night or early Tuesday. That will be followed by a Launch Readiness Review Tuesday afternoon at Vandenberg.

While awaiting the delivery of new batteries, the launch team has worked through the problems encountered during first launch attempt. During that countdown, a pair of problems cropped up and stopped the launch.

The first dealt with the sequencer system that controls the final two minutes of the countdown. When clocks ticked past T-minus 2 minutes, nothing happened. The rocket's flight computer failed to enter the sequence as planned.

"We have several scenarios that could have caused the sequencer problem," Buckley said. "Unfortunately, we do not have enough data to be able to capture the exact one."

But engineers can say the rocket's onboard flight computer never started its sequencer to complete the final two minutes of the countdown. Officials suspect the signal sent to the rocket to trigger the sequencer was corrupted. If that occurred, the ground support system would have recognized what happened and defaulted to an internal clock. But it was later found that the clock was six minutes off.

"If that indeed is what happened, then we are in a situation where the vehicle was just sitting around waiting for the two times to synch up. We, of course, aborted (before that)," Buckley said.

Officials have decided to not use the automatic mode for the next attempt this week.

"We decided to use a manual launch process. We will see the time count down to T-minus 2 minute point, and at the point, someone will say 'ready, ready' and press the button to start the (rocket's onboard computer) sequencer. We did that at least four times on this vehicle after the incident on the 14th. So we know that will work."

Officials determined they could try again on the night of 14th before the end of the launch window. But just over two minutes before liftoff, a launch controller called a hold because batteries that power the rocket's avionics drained below the allowable limit. That caused the countdown to be scrubbed for the day.

In retrospect, engineers have determined the batteries were simply topped off during the delayed countdown instead of being reconditioned as planned. That miscommunication meant technicians calculating whether there was enough voltage left in the batteries for the attempt near the end of the launch window was wrong.

"The prediction was off. What was reported to me before I authorized the recycle to attempt the launch the second time on the 14th was that I had a 15 percent margin. What ended up happening was that I did not have a 15 percent margin."

That led to the predictions being generated in error since the engineers were basing their estimations on the batteries being fully reconditioned.

Buckley says the team believes it is ready for the second launch attempt this week.

"I'm confident it is the right time to try. We worked through all the issues that occurred on the 14th. The 14th was, unfortunately, the first time we had taken the vehicle to that level of readiness, which is normal. There is a point where you do steps that you never do, and that point is when you try and launch the bird. So we certainly have resolved in our mind all the issues."

WEDNESDAY, JANUARY 19, 2000
0501 GMT (12:01 a.m. EST)

The U.S. Air Force has yet to reschedule the launch of the first OSP Minotaur rocket carrying the JAWSAT satellite platform. Efforts continue to find replacement batteries to install into the rocket's Range Safety system, and another launch try might not come until mid-to-late next week.

The first launch attempt was scrubbed early Saturday morning when other batteries on the rocket, ones that power Minotaur's avionics, drained below acceptable voltage limits for the mission.

Since the postponement, workers have removed the spent Range Safety batteries on the first and second stages. The premature stage separation batteries are not rechargeable and must be swapped out with fresh ones after they are activated. The batteries would be used in the safety system to destroy the rocket should a mishap occur during launch.

The Air Force is still searching for replacement batteries that can be installed on the Minotaur. Once new batteries are found and are aboard the rocket, testing and checks with the Range will have to be performed.

Sources indicate the launch might not happen before January 27 or 28, but the date is dependent on how quickly the spare batteries are located and installed. Officially, the launch could not happen before January 22.

SATURDAY, JANUARY 15, 2000
0730 GMT (2:30 a.m. EST)

The OSP Minotaur rocket's maiden launch will be delayed until around Janaury 22 after tonight's countdown ended a last-minute cutoff, the U.S. Air Force has confirmed.

After fixing an early glitch with a Range Safety command transmitter, the countdown was ticking along for a 0327 GMT (10:27 p.m. EST) liftoff. But clocks were halted at T-minus 2 minutes when the countdown sequencer program failed to automatically start. The sequencer is the master computer program that runs the final two minutes of the count.

Once the rocket was safed and the countdown recycled, officials determined the problem could be corrected by manually starting the sequencer.

With that plan in place, the countdown was restarted at T-minus 25 minutes for a planned 0540 GMT (12:40 a.m. EST) launch. But with just over two minutes to go, a launch team member called an abort after seeing the voltage readings fall below acceptable limits on the rocket's avionics batteries.

The batteries were activated during the first aborted countdown and ultimately did not last through the extended wait to the second try.

Officials plan to replace the other batteries prior to the next launch opportunity, which is expected on the evening of January 22 local time at Vandenberg Air Force Base.

The wait for another attempt is caused by the previously scheduled launch of a modified Minuteman 2 Multi-Service Launch System missile on a $100 million suborbital test. The mission is scheduled between 0201 and 0600 GMT Wednesday.

The Air Force-run Western Range, which provides communications, tracking and safety services to all Vandenberg launches, needs a few days to reconfigure its systems to support different vehicles.

The test involves the Vandenberg-launched missile carrying a dummy warhead and decoy for a hit-to-kill with another Minuteman 2 and its interceptor launched from from Kwajalein Missile Range. The intercept will occur over the Pacific Ocean.

0545 GMT (12:45 a.m. EST)

Officials have approved the plan to continue through the abort contingency checklist and then to power off the rocket. At that point, the launch attempt will be scrubbed for the night.

The preliminary word about the problem is the onboard batteries were depleted too much to support the launch.

When the next opportunity to launch Minotaur and JAWSAT will be available is not yet clear because of other operations scheduled on the Western Range at Vandenberg. It appears, however, that the next try should be late next week.

0541 GMT (12:41 a.m. EST)

The initial report is the cutoff was ordered after a problem was noted at one of the launch team consoles. We will pass along further details as they become available.

0540 GMT (12:40 a.m. EST)

The rocket's avionics have switched back to external power.

0539 GMT (12:39 a.m. EST)

Safing is underway again after the second countdown of the night ended in a cutoff. The rocket's flight computer has been disarmed and the flight termination system is being safed.

0538 GMT (12:38 a.m. EST)

The countdown has stopped and this should be a scrub for tonight since the window closes at 0554 GMT.

0537 GMT (12:37 a.m. EST)

ABORT! A cutoff has been called.

0537 GMT (12:37 a.m. EST)

T-minus 2 minutes, 30 seconds. The guidance computer is now in navigation mode. Coming up on auto sequence start in 30 seconds.

0536 GMT (12:36 a.m. EST)

T-minus 3 minutes, 30 seconds. The guidance system alignment is completed.

0536 GMT (12:36 a.m. EST)

T-minus 4 minutes. The flight computer is armed.

0535 GMT (12:35 a.m. EST)

T-minus 4 minutes, 30 seconds. Minotaur's avionics are now running on internal power.

0535 GMT (12:35 a.m. EST)

T-minus 5 minutes. The Range recorders are now running.

0534 GMT (12:34 a.m. EST)

T-minus 5 minutes, 30 seconds. Battery voltages are being verified.

0533 GMT (12:33 a.m. EST)

T-minus 6 minutes, 30 seconds. A final poll of the launch team has been completed and all systems are go.

0533 GMT (12:33 a.m. EST)

T-minus 7 minutes. The flight termination system is armed.

0532 GMT (12:32 a.m. EST)

T-minus 8 minutes. The rocket's flight termination system has switched to internal power.

0531 GMT (12:31 a.m. EST)

T-minus 9 minutes and counting. The ground alignment of the navigation unit is starting.

0530 GMT (12:30 a.m. EST)

T-minus 10 minutes and counting.

0528 GMT (12:28 a.m. EST)

T-minus 12 minutes and counting. Safety officials have verified the launch pad is cleared of all workers.

0526 GMT (12:26 a.m. EST)

Voltage and current checks of the rocket's flight termination system have been completed.

0523 GMT (12:23 a.m. EST)

Upper level winds are reported acceptable for launch.

0521 GMT (12:21 a.m. EST)

The launch conductor says if the countdown continues to go smoothly, they will not need to use the optional hold at T-minus 10 minutes. Launch remains set for 0540 GMT (12:40 a.m. EST). Also, there are no collision avoidance, or COLA, restrictions for objects in space for the new launch time.

0518 GMT (12:18 a.m. EST)

The Air Force reports the weather conditions remain acceptable for launch.

0515 GMT (12:15 a.m. EST)

A readiness poll of the team has been completed and the countdown is running again toward a second launch attempt.

0507 GMT (12:07 a.m. EST)

Officials are planning to restart the countdown at 0515 GMT from the T-minus 25 minute mark. That will lead toward a liftoff at 0540 GMT (12:40 a.m. EST).

It appears the earlier problem that caused the cutoff at T-minus 2 minutes has been resolved.

0503 GMT (12:03 a.m. EST)

The launch team is looking over the procedures for the second attempt tonight. In addition, Orbital Sciences has announced the OSP Minotaur vehicle is officially ready.

0446 GMT (11:46 p.m. EST)

Unofficially, the Air Force says they are aiming for launch around 0525 or 0535 GMT (12:25 or 12:35 a.m. EST). Tonight's available launch window extends to 0554 GMT (12:54 a.m. EST).

0424 GMT (11:24 p.m. EST)

Now 90 minutes remaining in the available window for tonight's launch attempt. The launch team has not given up on getting the Minotaur off the ground tonight.

Meanwhile, the weather reconnaissance aircraft is headed back for a refueling stop.

0419 GMT (11:19 p.m. EST)

The team at the pad are also changing out five nitrogen bottles that are used to cool the rocket's transmitter.

Reports are the temperature at the pad is 61 degrees F and the thermal conditioning of the rocket's engines will not be a problem for another launch attempt tonight.

0415 GMT (11:15 p.m. EST)

A team of engineers have arrived at the Commercial Launch Facility where the Minotaur rocket remains poised for liftoff. The team is checking temperatures to ensure the rocket's engines are within thermal conditioning limits for ignition.

0410 GMT (11:10 p.m. EST)

There is nothing new to report. Efforts continue to understand and correct the ground problem that halted the first attempt. There is still the opportunity to launch Minotaur with JAWSAT before the close of today's window at 0554 GMT (12:54 a.m. EST), so don't go away!

0353 GMT (10:53 p.m. EST)

An engineer may be dispatched to the launch pad to take the temperature at the site. The air temperature is important in determining the thermal conditioning of the rocket's Minuteman 2 first and second stage engines for launch.

0343 GMT (10:43 p.m. EST)

The launch team is still preserving the option to recycle the countdown back to T-minus 35 minutes and trying another attempt before the end of tonight's three-hour window at 0554 GMT (12:54 a.m. EST). However, troubleshooting is underway and the ground support equipment problem must be fixed before another attempt could be made tonight.

0338 GMT (10:38 p.m. EST)

The onboard batteries will last through the launch window, so they will not be a factor. However, the heating system to the rocket's first and second stage engines was disconnected earlier in the countdown. As a result, the engine temperatures must remain within acceptable limits for the launch to be allowed or else the heating ducts will have to be reattacted.

0336 GMT (10:36 p.m. EST)

Efforts are not over for another try tonight!

The launch conductor reports the ground support equipment did not send the auto sequence start command to Minotaur's flight computer. That problem is being worked and the launch may be able to go tonight.

0330 GMT (10:30 p.m. EST)

Since the rocket's onboard batteries were activated, they now must be replaced if the launch cannot fly tonight.

Previously, the Air Force launch director said if Minotaur did not fly tonight, the next try would not come until late next week due to Range availability.

We will have further details when they become available.

0329 GMT (10:29 p.m. EST)

Troubleshooting teams have been assigned. The launch conductor says the auto sequencer did not start as programmed at T-minus 2 minutes. The auto sequence is the master computer program that controls the final minutes of the countdown.

0328 GMT (10:28 p.m. EST)

Minotaur avionics and flight termination system have switched back to external power.

0327 GMT (10:27 p.m. EST)

The rocket's safe and arm devices have been safed. The flight termination system has been safed, too.

0325 GMT (10:25 p.m. EST)

Safing underway. Auto sequence start was not confirmed and the countdown has been halted.

0325 GMT (10:25 p.m. EST)

ABORT! SEQUENCER HAS STOPPED.

0325 GMT (10:25 p.m. EST)

T-minus 2 minutes. Auto sequence start.

0324 GMT (10:24 p.m. EST)

T-minus 3 minutes. The guidance computer is now in navigation mode.

0323 GMT (10:23 p.m. EST)

T-minus 4 minutes. The guidance system alignment is completed.

0322 GMT (10:22 p.m. EST)

T-minus 4 minutes, 30 seconds. The flight computer is armed.

0322 GMT (10:22 p.m. EST)

T-minus 5 minutes. Recorders are now running. Standing by to transfer Minotaur's avionics to internal power.

0321 GMT (10:21 p.m. EST)

T-minus 6 minutes. A final poll of the launch team has been completed and all systems are go.

0320 GMT (10:20 p.m. EST)

T-minus 7 minutes. The flight termination system has now been armed.

0319 GMT (10:19 p.m. EST)

T-minus 8 minutes. The rocket's flight termination system has switched to internal power.

0317 GMT (10:17 p.m. EST)

T-minus 10 minutes and counting. The countdown has resumed after this delay. Launch is set for 0327 GMT (10:27 p.m. EST).

0316 GMT (10:16 p.m. EST)

The launch team reports the Range problem has been corrected. Countdown clocks will resume in one minute. Launch is planned for 0327 GMT (10:27 p.m. EST).

0315 GMT (10:15 p.m. EST)

The Range is going through checks of the command destruct system to see if the problem has been resolved.

0310 GMT (10:10 p.m. EST)

The Air Force hopes to get the command transmitter working in about five minutes, clearing the way for launch at 0327 GMT (10:27 p.m. EST).

0305 GMT (10:05 p.m. EST)

The U.S. Air Force has three hours in which to launch the Minotaur rocket tonight. The available launch window closes at 0554 GMT (12:54 a.m. EST).

One of the satellite payloads had wanted to launch in the first 20 minutes of the window in order to collect the best data. However, since this launch is a test of the rocket, the liftoff can occur outside the 20-minute window and degraded results would be accepted from that one satellite.

0303 GMT (10:03 p.m. EST)

The decision has been made to extend this hold at T-minus 10 minutes as troubleshooting goes on for the Range problem. So launch is no longer set for 0314 GMT. A new liftoff time has not been established.

0301 GMT (10:01 p.m. EST)

While this Range problem is being worked, we should point out that if the launch is postponed the next attempt is not expected until January 22, according to Maj. Steve Buckley, the launch director. The extended delay would be caused by the planned missile test launch from Vandenberg Air Force Base early next week and the time it takes the Range to reconfigure systems from one rocket to another.

0258 GMT (9:58 p.m. EST)

Air Force Range engineers are troubleshooting a problem with command transmitter No. 3. The CT would be used to send destruct commands to destroy the rocket should an accident occur in flight. This system must be working properly in order for the countdown to restart toward launch.

0255 GMT (9:55 p.m. EST)

The new liftoff time is now planned for 0314 GMT (10:14 p.m. EST) if the Range problem can be fixed in time.

0254 GMT (9:54 p.m. EST)

T-minus 10 minutes and holding. The countdown clock is holding while the Range problem is discussed.

0251 GMT (9:51 p.m. EST)

The U.S. Air Force reports the Western Range is red. We are standing by for further details.

0249 GMT (9:49 p.m. EST)

T-minus 15 minutes and counting.

0238 GMT (9:38 p.m. EST)

The U.S. Air Force, as expected, has shifted the launch back by 10 minutes to the preferred launch time of 0304 GMT (10:04 p.m. EST). The countdown continues and no problems are being worked.

0224 GMT (9:24 p.m. EST)

The latest weather forecast indicates acceptable conditions for launch.

Tonight's launch is the first time a Minuteman ICBM has been used to place a satellite into space. But the idea has been around for over 30 years. The U.S. Air Force had thought about launching a Minuteman 1 with an extra upper stage in the late 1960s, but that flight was scrapped.

Recently, I interviewed Maj. Steve Buckley, the launch director for this inaugural OSP Minotaur mission.

"The concept has been around for a long, long time...We never got to the point where we intended to launch a satellite using (solid-fueled ICBM) systems. Part of the reason is a satellite takes a lot more energy and most of the ICBMs did not have the energy to put a useful satellite on-orbit. So we put together a hybrid to achieve the kind of thrust that we needed to get to orbit. This configuration we are going to fly coming up here has half of it is Minuteman heritage and half if it is Pegasus heritage.

"The satellite niche that we are aimed at are small satellites going to low-Earth orbit. Most of what we launch are developmental-type satellites. Small launchers of this class weren't available with the exception of the Scout...which was a scientific rocket and it does not have an ICBM heritage."

Lt. Lou Marina, Air Force's small launch vehicle mission manager, explains why ICBM boosters are used to form a new rocket instead of launching commercial vehicle already available.

"When Minuteman was deactivated, we had hundreds of these rocket motors sitting there doing nothing. There were not going to be used for ICBMs anymore, but they were quality built motors and already paid for by the U.S. tax payer. We felt we could use these motors for something else other than ICMBs and space launch is something we could use them for. As a result we have the (OSP) Space Launch Vehicle."

Minotaur has the capability to launch every 60 days. However, there aren't that many satellites to launch so Minotaur is expected to fly twice per year over the course its contract life between the U.S. Air Force and Orbital Sciences. The contract extends for another four years.

Marina: "Because the rocket is inexpensive as it is in comparison to other rockets, we feel that once we are successful with this first and probably the second launch this spring, there will be a lot of government folks that want to sign up to launch their payloads on this rocket. I don't see a reason why this won't be a successful program."

Read the fact sheet on OSP Minotaur.

0209 GMT (9:09 p.m. EST)

T-minus 45 minutes and counting. Night has fallen at the launch site and the four-stage Minotaur rocket stands illuminated by floods lights. The mobile service structure at the pad has been retracted, earlier than originally planned. At this point, the launch team is monitoring rocket systems through umbilicals and the first stage is being heated to ensure proper conditioning for ignition.

0154 GMT (8:54 p.m. EST)

Now one hour away from the opening of the three-hour launch window. Officials are expected to shift to launch to 0304 GMT (10:04 p.m. EST), the preferred time by one of the onboard satellite payloads.

The rocket flying tonight is officially known as the U.S. Air Force Orbital Suborbital Program Space Launch Vehicle. However, it also has the nickname Minotaur. Lt. Lou Marina, Air Force's small launch vehicle mission manager explains how the rocket got this unofficial nickname.

"We were trying to keep in the traditional of Orbital Sciences' launch vehicle. Typically, they are mythological nicknames (Pegasus and Taurus) and this is just a nickname. We had an Air Force/Orbital Sciences 'name the rocket contest' and everyone who felt they had a good name for the rocket and could put a plausible reason to why the rocket should be named that. We had at least a hundred entries of different mythological creatures and some weren't even mythological. When it came down to it, Minotaur was the one we selected. We felt it was appropriate. The Minotaur is half bull, half man. This rocket is half a Pegasus and half Minuteman. It really is an Orbital Sciences Corp. marketing name. It is hard to market a vehicle if it has a long name like OSP Space Launch Vehicle."

0130 GMT (8:30 p.m. EST)

The sun is setting at Vandenberg Air Force Base as the countdown continues ticking along smoothly for launch of the Minotaur rocket and JAWSAT payload in about 90 minutes. Weather conditions are promising and no technical problems are being reported from the launch team.

FRIDAY, JANUARY 14, 2000
2350 GMT (6:50 p.m. EST)

All systems remain go at Vandenberg for tonight's launch of the Minotaur rocket at 0254 GMT (9:54 p.m. EST).

The mission will be the first to occur from the Commercial Launch Facility operated by Spaceport Systems International. SSI is a limited partnership between ITT Industries and California Commercial Spaceport, Inc.

The pad is not run by the U.S. Air Force or NASA, and is aimed at small- to medium-sized rockets. The CLF is situated the southern most corner of Vandenberg Air Force Base near Space Launch Complex-6, which would have been used by the space shuttle. Construction of the new pad was completed on May 1.

SSI also operates a payload processing facility (IPF) located at Space Launch Complex-6.

2230 GMT (5:30 p.m. EST)

The countdown is inside the final 4 1/2 hours to the launch of a U.S. Air Force OSP Minotaur rocket from Vandenberg Air Force Base, California. Activities are reported on schedule and no problems are being worked.

The weather forecast has become less favorable than the predictions issued yesterday. At the opening of tonight's launch window at 0254 GMT (9:54 p.m. EST), the Air Force says there is a 60 percent chance layered clouds will violate the launch weather rules. The earlier forecast called for a 40 percent chance the clouds would be a problem.

However, the cloud issue is expected to improve later in the three-hour launch window, making officials hopeful for a liftoff tonight.

Other weather criteria that is monitored, particularly the winds and temperature, are forecasted to be within limits, said U.S. Air Force spokeswoman Lt. Colleen Lehne.

2100 GMT (4 p.m. EST)

Launch team members are scheduled to arrive on console at this time in preparation for tonight's flight of the Minotaur rocket.

"We have two teams running this launch," said U.S. Air Force Major Steve Buckley, the launch director. "The first team is actually working the rocket and they are located at the spaceport on the south base at Vandenberg. That operation is aimed at the mechanical operation of the rocket. The other group is what we call the Mission Control Team, and they are going to be up in the formal control room at Building 7000. Their job is to oversee all the events and make decisions if anything happens."

Launch will be possible during a window of 0254 to 0554 GMT (9:54 p.m. to 12:54 a.m. EST) from Vandenberg Air Force Base in California. The rocket should be visible as it travels southward along Southern California's Pacific coastline, headed toward a polar orbit 405 nautical miles above Earth.

0501 GMT (0001 EST)

The idea of using a Minuteman Intercontinental Ballistic Missile to launch a satellite into space is not new. In fact, the U.S. military considered it more than 30 years ago. But it will finally happen today, becoming the first orbital launch of the new millennium.

The maiden flight of the U.S. Air Force Orbital Suborbital Program Space Launch Vehicle, nicknamed Minotaur, is slated for liftoff tonight from Vandenberg Air Force Base, California. A three-hour launch window opens at 0254 GMT (9:54 p.m. EST), however, officials hope to send the rocket skyward at precisely 0304 GMT (10:04 p.m. EST).

Capt. Eric Barela, the Air Force launch weather officer, predicts a 60 percent chance of acceptable weather with the concern being layered clouds.

The launch time forecast calls for stratus clouds providing complete overcast at 300 feet, layered altostratus clouds broken at 12,000 feet and broken cirrus clouds at 24,000 feet, visibility between 1/2 to 2 miles, southwesterly winds 10 to 15 knots, a temperature of 48 to 53 degrees F and fog.

The mission tonight is simple: Minotaur has to prove it can place healthy satellites into the correct orbit. The vehicle is a combination booster with its first two stages comprised of a Minuteman 2 ICBM and the third and fourth stages taken from an Orbital Sciences Pegasus rocket.

Although this is just a test flight, the rocket will use the JAWSAT platform as its payload. The Joint Air Force Academy-Weber State University satellite actually carries 10 other tiny spacecraft that will be ejected into orbit.

The countdown will switch to high gear at T-minus 6 hours as the launch team begins gathering. The painter-like scaffolding enclosing the rocket at the Commercial Launch Facility will be retracted at T-minus 40 minutes.

If the weather looks favorable and there are no problems, officials will hold the countdown for 10 minutes in order to synch up with the preferred launch time of 0304 GMT (10:04 p.m. EST). There is a three-hour launch window available (0254-0554 GMT) but a desired 20-minute period (0254-0314 GMT) that is needed by one of the payloads. In addition, that specific payload wants to hit the middle of the 20-minute period at 0304 GMT (10:04 p.m. EST). But since the purpose of this launch is to test the Minotaur, liftoff can occur outside that 20-minute period with degraded results from that one satellite.

At T-minus 6 minutes, onboard batteries will begin supplying power to the rocket. In the final two minutes, computers will assume complete control of the countdown.

Duration of the launch through separation of the final payload will last about 20 minutes. But since the satellite deployments will occur while the rocket is out of range from tracking stations, the data will be recorded and downlinked to a site in Antarctica at about T+plus 35 minutes. Confirmation of a successful flight, which will be based on the rocket achieving orbit, making the correct orbit and deployment of the satellites, is not expected to be announced by the Air Force until approximately 2 1/2 hours after launch.

We will have comprehensive coverage during the final hours of the countdown and throughout the flight. Check back to our Mission Status Center for the very latest on the this launch, plus stories about the rocket and satellites.