BY JUSTIN RAY

Follow the preparations and launch of the Lockheed Martin-built Titan 4B rocket carrying the sixth and final Milstar military communications satellite. Reload this page for the very latest on the mission.

SUNDAY, APRIL 6, 2003
1740 GMT (1:40 p.m. EDT)

SCRUB! Today's launch of the Titan 4B rocket and the Milstar 6 communications satellite for the U.S. Air Force has been scrubbed. After a series technical and Range issues, time has run out today. Officials are targeting a 48-hour turnaround for another launch attempt on Tuesday during a window of 9:43 a.m. to 1:43 p.m. EDT.

1735 GMT (1:35 p.m. EDT)

The launch team is reporting Centaur battery measurements dropped below their redline limit. The PAGE sequencer performed a countdown abort as designed when the Centaur readiness state was "no go" for flight.

1731 GMT (1:31 p.m. EDT)

Today's launch window closes in 20 minutes.

1730 GMT (1:30 p.m. EDT)

The Milstar 6 spacecraft atop the rocket is switching back to ground power.

1729 GMT (1:29 p.m. EDT)

The Programmable Aerospace Ground Equipment launch sequencer stopped the countdown when Centaur readiness was lost again.

1728 GMT (1:28 p.m. EDT)

T-minus 1 minute, 54 seconds. HOLD CALLED!

1728 GMT (1:28 p.m. EDT)

T-minus 2 minutes. The Centaur upper stage is switching from ground-fed power to internal batteries for launch. The vehicle's Flight Termination System is also transferring to internal power.

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

T-minus 2 minutes, 45 seconds. The Range recorders are operating.

1726 GMT (1:26 p.m. EDT)

T-minus 3 minutes, 30 seconds and counting.

1725 GMT (1:25 p.m. EDT)

T-minus 4 minutes, 30 seconds. The Milstar spacecraft is being confirmed on internal power for flight.

1725 GMT (1:25 p.m. EDT)

T-minus 5 minutes and counting again! The launch sequence is now starting. Liftoff of the Titan 4B rocket is scheduled for 1:30 p.m. EDT.

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

Neither an explanation of the problem nor how it was resolved have been announced by Lockheed Martin. If we get that information, we will pass it along.

1721 GMT (1:21 p.m. EDT)

Range has given its clear to launch. All appears in readiness to resume the countdown at 1:25 p.m. for liftoff five minutes later.

1718 GMT (1:18 p.m. EDT)

The readiness poll by the launch conductor is complete with no problems reported.

1715 GMT (1:15 p.m. EDT)

There are 10 minutes remaining in this hold. There hasn't been any word from Lockheed Martin on how the Centaur issue was resolved.

1705 GMT (1:05 p.m. EDT)

NEW LAUNCH TIME. Liftoff has been rescheduled for 1:30 p.m. EDT. The launch window extends to 1:51 p.m. EDT.

1701 GMT (1:01 p.m. EDT)

A new launch time of 1:30 p.m. EDT is being debated.

1638 GMT (12:38 p.m. EDT)

The Centaur tracking and flight safety team is convening a discussion on the anomaly channel at this time.

1635 GMT (12:35 p.m. EDT)

Sources say the countdown hold at T-minus 81 seconds was caused when the Centaur readiness was lost. The PAGE sequencer detected the situation as designed and called a hold.

1631 GMT (12:31 p.m. EDT)

Eighty minutes are remaining in today's available launch window. There is conflicting information concerning the exact cause of the countdown -- whether its Centaur or PAGE. No further details have been announced by Lockheed Martin.

1615 GMT (12:15 p.m. EDT)

Lockheed Martin is correcting earlier information that a spokesman announced to the media. The countdown hold at T-minus 81 seconds was due to a constraint with the PAGE ground equipment system and not with the Centaur upper stage itself.

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

Launch weather officer Johnny Weems says there really isn't any weather concerns for the remainder of today's window.

1558 GMT (11:58 a.m. EDT)

Engineers are assessing the situation to see if the Centaur problem can be resolved and permit liftoff before the close of today's launch window at 1:51 p.m. EDT.

1554 GMT (11:54 a.m. EDT)

The hold apparently was called when the Centaur "ready" status was lost.

1552 GMT (11:52 a.m. EDT)

The Milstar 6 spacecraft is switching back to external power. It had gone to internal batteries for launch earlier in the countdown.

1550 GMT (11:50 a.m. EDT)

Lockheed Martin says it could take about an hour to recycle. A spokesman also says the problem that caused the sequencer to hold the countdown could be Centaur-related. However, that remains to be confirmed.

1549 GMT (11:49 a.m. EDT)

The PAGE launch sequencer system halted the countdown at T-minus 1 minute, 21 seconds. There is no word on what caused the hold.

1548 GMT (11:48 a.m. EDT)

T-minus 81 seconds and holding! HOLD HAS OCCURRED.

1548 GMT (11:48 a.m. EDT)

T-minus 2 minutes. The Centaur upper stage is now switching from ground-fed power to internal batteries for launch. The vehicle's Flight Termination System is also transferring to internal power.

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

T-minus 2 minutes, 45 seconds. The Range recorders are running.

1545 GMT (11:45 a.m. EDT)

T-minus 5 minutes and counting! The Programmable Aerospace Ground Equipment -- the PAGE computer system -- is controlling the countdown sequence. Liftoff of Titan 4 B-35 and the final Milstar spacecraft is scheduled for 11:50 a.m. EDT from Complex 40 at Cape Canaveral Air Force Station, Florida.

1544 GMT (11:44 a.m. EDT)

Standing by to resume the countdown from the T-minus 5 minute mark in one minute.

1540 GMT (11:40 a.m. EDT)

Now 10 minutes away from the new launch target time. The Range is reporting it is ready to support.

1537 GMT (11:37 a.m. EDT)

The launch conductor is performing another final status check before the countdown resumes. Clocks are scheduled to pick up at 11:45 for liftoff at 11:50 a.m. EDT today.

1532 GMT (11:32 a.m. EDT)

NEW LAUNCH TIME. The launch of Titan 4 and Milstar 6 has been rescheduled for 11:50 a.m. EDT (1550 GMT).

1528 GMT (11:28 a.m. EDT)

Officials are discussing a possible new launch time of 11:50 a.m. EDT.

1518 GMT (11:18 a.m. EDT)

The launch team is going to adjust a pressure setting on the Titan's second stage. This should be done in parallel to the Range sweep. A new launch time has not been set.

1505 GMT (11:05 a.m. EDT)

The Range is estimating 30 minutes for the sweep of the launch hazard area.

1501 GMT (11:01 a.m. EDT)

"We're not going to make it." A launch team member reports work to recondition the Centaur won't be completed in time to resume the countdown at 11:03 a.m. A chilldown on the liquid hydrogen transfer line will have to occur. "We can't get it to flight level in the current configuration," the member said.

What's more, the Range could only verify the danger area was clear through 11:08 a.m. So another sweep of the area will now be required.

There is no estimate on a new launch time.

1501 GMT (11:01 a.m. EDT)

The Programmable Aerospace Ground Equipment that will control the final minutes of the countdown is verified ready.

1459 GMT (10:59 a.m. EDT)

A final status check of the launch team members is being conducted.

1458 GMT (10:58 a.m. EDT)

NEW LAUNCH TIME. Officials have confirmed a new launch time of 11:08 a.m. EDT (1508 GMT). The countdown will resume from T-minus 5 minutes at 11:03 a.m.

1455 GMT (10:55 a.m. EDT)

A new launch time of 11:08 a.m. EDT is being discussed.

1451 GMT (10:51 a.m. EDT)

Topping off of the Centaur upper stage is being completed. The super-cold liquid oxygen and liquid hydrogen cryogenics naturally boil away and have to be replenished until just before liftoff time.

1447 GMT (10:47 a.m. EDT)

The Range is now "go" for launch again. The aircraft has left the restricted area. Meanwhile, the launch team is still stepping through recycling procedures.

1446 GMT (10:46 a.m. EDT)

T-minus 5 minutes and holding. The countdown has been reset. There is no word yet on a new launch time.

The first countdown was manually aborted when the Range announced a "no go" status due to an intruder aircraft in the launch danger area.

1439 GMT (10:39 a.m. EDT)

The launch team is recycling the countdown for another attempt. Over three hours remain in today's window.

1438 GMT (10:38 a.m. EDT)

The countdown has been called by the Eastern Range. An aircraft is in the restricted airspace around the launch site.

1437 GMT (10:37 a.m. EDT)

T-minus 2 minutes, 23 seconds and holding. HOLD IS CALLED.

1437 GMT (10:37 a.m. EDT)

T-minus 3 minutes. Cameras and Range recorders are being readied.

1436 GMT (10:36 a.m. EDT)

T-minus 4 minutes and counting.

1435 GMT (10:35 a.m. EDT)

T-minus 5 minutes and counting. The Terminal Countdown has begun for launch of Titan 4 B-35 and the final Milstar spacecraft from Complex 40 at Cape Canaveral Air Force Station, Florida.

The countdown sequence is now being controlled by the Programmable Aerospace Ground Equipment -- the PAGE computer system.

1434 GMT (10:34 a.m. EDT)

The launch team is preparing to pick up the countdown in one minute.

1432 GMT (10:32 a.m. EDT)

The Air Force-controlled Eastern Range has given its final clearance to launch the Titan 4B rocket today.

1430 GMT (10:30 a.m. EDT)

Now 10 minutes away from liftoff.

Today's launch will mark the 35th for a Titan 4 rocket dating back to 1989 and the 13th flight of the newer Titan 4B model. It will be the 15th mission of a liquid-fueled Centaur upper stage on a Titan 4. This is the 24th Titan 4 to launch from Cape Canaveral and the 14th from Complex 40.

1428 GMT (10:28 a.m. EDT)

NEW LAUNCH TIME. Officials have given approval to establish a new launch time of 10:40 a.m. EDT. The countdown will resume from T-minus 5 minutes at 10:35 a.m.

1428 GMT (10:28 a.m. EDT)

A poll of the various launch team members has been performed with no problems reported!

1427 GMT (10:27 a.m. EDT)

The launch team is looking at a new liftoff time of 10:40 a.m. EDT.

1426 GMT (10:26 a.m. EDT)

Lockheed Martin says the Centaur issues are nearly resolved. A new time is being discussed.

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

Upper level wind conditions have been verified acceptable through 11:56 a.m. EDT (1556 GMT) today. Weather balloons are released throughout the countdown to measure the speed and direction of winds aloft to determine if the Titan 4 rocket can safely fly through the conditions.

1410 GMT (10:10 a.m. EDT)

Lockheed Martin now says there are two problems on the Centaur. A mechanical issue that appears to be resolved now and the flight termination system glitch announced earlier, which is still being worked.

1405 GMT (10:05 a.m. EDT)

Countdown clocks remain holding at T-minus 5 minutes. There has been no further update from Lockheed Martin on the Centaur problems or a new liftoff time.

1348 GMT (9:48 a.m. EDT)

To recap, there is a technical problem that has put today's launch on hold. A new liftoff time has not been established. The launch team has until 1:51 p.m. EDT (1751 GMT) to get the rocket airborne or else wait until another day.

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

Lockheed Martin says this problem relates to the Centaur's Range Safety system. The Centaur electrical and flight safety teams are working the issue.

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

HOLD EXTENDED. The countdown clock will not resume ticking at 9:46 a.m., effecting delaying this morning's launch by some undetermined amount of time. Today's window extends to 1:51 p.m. EDT.

The launch team is still addressing some issues with the Centaur upper stage. Details have not been released. We will update when information becomes available.

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

T-minus 5 minutes and holding. Countdown clocks have stopped for a scheduled 10-minute hold. During this period, final readiness checks will be performed by the launch team to ensure all systems are "go" for today's mission. Once everything is confirmed in readiness, the countdown will resume. The launch window extends from 9:51 a.m. to 1:51 p.m. EDT today.

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

T-minus 10 minutes and counting. The countdown will be entering the built-in hold shortly. Meanwhile, Lockheed Martin says the launch team is awaiting final confirmation that the Range Safety checks have been wrapped up successfully.

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

Now a half-hour away from the planned liftoff time. At this point, controllers are scheduled to 'power on' the Milstar satellite nestled in the nose cone atop the Titan 4B rocket.

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

The countdown continues to progress for today's launch of Titan 4 B-35 and its Centaur upper stage designated TC-23.

The Titan 4B rocket weighs about 2,074,000 pounds at present with the Milstar satellite cargo atop the massive launcher. The two stages of the Titan's central core vehicle was loaded previously with storable hypergolic Aerozine 50 and nitrogen tetroxide propellants. The liquid-fueled Centaur upper stage was filled cryogenic liquid oxygen and liquid hydrogen this morning. The large white rocket motors strapped to Titan are solid-propellant.

Read the fact sheet for a description of the rocket.

1306 GMT (9:06 a.m. EDT)

T-minus 35 minutes and counting. The countdown clocks are headed to T-minus 5 minutes where a 10-minute hold is planned. Launch is still set for 9:51 a.m. EDT. The earlier technical troubles have been resolved, Lockheed Martin reports.

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

At this point in the countdown, Range Safety is completing the final checks of the command destruct receivers that would be used to destroy the Titan rocket should it veer off course or experience a problem during launch today.

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

The Eastern Range reports the earlier problem involving the Antigua tracking station has been resolved! Also, Lockheed Martin says the launch team has made up some time in the countdown after experiencing some problems at the start of the computer-controlled process of fueling Centaur. Liftoff is still targeted for 9:51 a.m. EDT.

1252 GMT (8:52 a.m. EDT)

The latest check of the weather indicates conditions are well within limits for liftoff this morning. Skies are basically clear, it is 71 degrees F at the pad and winds from the southeast at 8 to 15 knots. Weather is 90 percent "go" for today, with the only concern near the end of the four-hour window.

Upper level winds are also verified to be acceptable.

1248 GMT (8:48 a.m. EDT)

Lockheed Martin says there are some technical problems being addressed with the Centaur upper stage and with the Range's Antigua downrange tracking station. The specific details on these issues have not been released as of yet.

1245 GMT (8:45 a.m. EDT)

Launch of the $461 million Titan 4B rocket and the $800 million Milstar 6 spacecraft is just over one hour away. It is an absolutely beautiful morning here on the east coast Florida as the Lockheed Martin and Air Force launch team count down to liftoff at 9:51 a.m. EDT.

1130 GMT (7:30 a.m. EDT)

Lockheed Martin reports that the launch remains on schedule for 9:51 a.m. EDT today.

The launch team is currently focused on the work to load liquid hydrogen and liquid oxygen cryogenic propellants into the Centaur upper stage. The stage's twin RL10 engines will consume the super-cold fuel and oxidizer during three burns needed to propel the Milstar 6 spacecraft directly into geostationary orbit later today.

Meanwhile, the weather forecast has been improved to a 90 percent chance of meeting the launch rules during the four-hour window.

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

The mobile service tower has been rolled away from the Titan 4B rocket in preparation for today's launch from Cape Canaveral's Complex 40.

Like a building on wheels, the Air Force says the 11.2 million pound mobile service tower has been considered the largest and heaviest self-propelled structure in the world. The 260-foot tall metal cocoon shields the Titan rocket while on the seaside launch pad from the weather while providing access to all areas of the vehicle. Its Class 100,000 cleanroom is where the Milstar satellite underwent final processing after being attached to the rocket.

Over the next couple of hours, pad crews will finish chores to lock the tower in its parked position and secure the complex facilities for launch.

0100 GMT (8:00 p.m. EST Sat.)

The Titan 4B rocket and Milstar 6 spacecraft remain poised for liftoff Sunday morning from Cape Canaveral Air Force Station.

Launch is targeted to occur at 9:51 a.m. EDT (1351 GMT). The day's available launch window extends to 1:51 p.m. EDT (1751 GMT).

There are no technical problems being reported by the Air Force and the weather forecast is generally favorable for liftoff.

"Our Titan team at Cape Canaveral has worked hard over the past year and we are ready to go," Lt. Col. Anthony Cotton, the Air Force launch director, said at a pre-launch news conference Saturday afternoon.

This Lockheed Martin-built Titan 4 has been on the launch pad since February 2002. Its original cargo -- a classified payload for the National Reconnaissance Office -- was not ready to launch last summer as planned, prompting the Air Force to use this rocket to carry Milstar 6.

Early Sunday morning, the mobile service tower enclosing the vehicle at Complex 40 is scheduled to be rolled into the launch position more than 7 1/2-hours before liftoff time.

Preparations to load super-cold liquid oxygen and liquid hydrogen propellants into the Centaur upper stage will commence about three hours before launch.

Watch this page for updates on the launch. Continuous live coverage will begin at about 8:45 a.m. EDT.

SATURDAY, APRIL 5, 2003

Air Force forecasters have improved the odds of acceptable weather forecast conditions on Sunday. See the forecast here.

FRIDAY, APRIL 4, 2003

The latest launch weather forecast is available here.

The final readiness reviews will be held on Saturday to clear the way for the countdown and launch of Titan 4 and the sixth Milstar communications spacecraft. A pre-launch news conference is scheduled for Saturday afternoon. We'll post an update following the briefing.

And watch this page on Sunday for live play-by-play updates starting around 8:45 a.m. EDT. The day's available launch window extends from 9:51 a.m. to 1:51 p.m. EDT.

THURSDAY, APRIL 3, 2003

This morning's updated launch weather forecast is posted here.

WEDNESDAY, APRIL 2, 2003

A 10,000-pound, $800 million satellite that will serve as an orbiting switchboard for secure communications between senior U.S. leaders and military forces around the world is slated for launch Sunday atop a Titan 4 rocket.

Liftoff is scheduled for 9:51 a.m. EDT (1351 GMT) from Complex 40 at Cape Canaveral Air Force Station, Florida. The day's available window extends four hours to 1:51 p.m. EDT (1751 GMT).

Read our launch preview story.

WEDNESDAY, FEBRUARY 26, 2003

The Air Force is now targeting an early April launch of its final Milstar communications satellite atop a Titan 4 rocket -- a mission that has been delayed since January to modify onboard software.

Launch officials decided to change the software on the Centaur upper stage to prevent "oscillations" during the launch. The concern stems from the use of newer model Pratt & Whitney RL-10 engines on this Centaur.

"The issue has been observed on other Centaur flights using similar engines," said Col. John Insprucker, Titan program official at Los Angeles Air Force Base.

"The resolution to the issue of possible oscillations caused by dynamic coupling between the Centaur/Milstar structure and the RL-10 issues is being achieved by modifying the Centaur software and associated flight constants database," Insprucker said. "This will allow operation of the Centaur engines without possibly creating an oscillation."

Within the first 10 minutes of ascent, the Titan 4's solid rocket boosters and two-stage core vehicle will complete their jobs, deploying the Centaur upper stage and attached Milstar cargo on a sub-orbital trajectory. The Centaur motor will then fire three times over the course of several hours to place the 10,000-pound Milstar spacecraft into geostationary orbit about 22,300 miles above Earth.

This will be the sixth and last Military Strategic and Tactical Relay satellite. Milstars act as smart switchboards in space, allowing users on foot, ships, submarines or aircraft to establish critical communications networks on the fly. The craft transmit voice, data and imagery, in addition to offering video teleconferencing capabilities.

The Air Force often calls Milstar the FedEx of communications satellites in explaining how the system is used to relay highly important transmissions. "When it absolutely, positively has to be there, Milstar is the system," a top Air Force official said at a previous Milstar launch.

April 6 has been picked for the launch from Complex 40 at Cape Canaveral Air Force Station, Florida. The day's four-hour window extends from 9:51 a.m. to 1:51 p.m. EDT (1351-1751 GMT).

"We are confident in the ability of the Titan team to finish modifying the software and flight constants database to the schedule that supports the launch date," Insprucker added.

One additional Titan 4 launch is being planned in 2003 -- the deployment of a classified National Reconnaissance Office cargo from the Cape. A launch date is pending for that flight, which was originally slated for last year only to be delayed until after Milstar 6 due to unspecified problems with the secret payload.