BY JUSTIN RAY

Follow the countdown and launch of the Boeing Delta 2 rocket with NASA's ICESat and CHIPSat spacecraft. Reload this page for the very latest on the mission.

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

Technicians at Space Launch Complex-2 West tonight will replace a faulty part in ground support equipment for the Delta 2 rocket's first stage helium system, a Boeing spokesman confirms. Officials remain very confident the issue will be resolved to permit another launch attempt at 4:45 p.m. PST (7:45 p.m. EST) Sunday.

And as a point of clarification, the statements from NASA on Saturday implied that this problem was on the Delta 2 rocket itself. But as Boeing later explained, the glitch was with launch pad equipment and not the vehicle. We wish make that distinction clear in our coverage.

The weather forecast for Sunday's launch opportunity is favorable.

0105 GMT (8:05 p.m. EST Sat.)

Boeing officials report this helium system pressurization problem is purely a ground support equipment issue and not on the rocket itself.

0050 GMT (7:50 p.m. EST Sat.)

A management team meeting is underway at this hour to review the hardware problem that forced Saturday's launch countdown to be called off and formalize the plan to correct the situation. This meeting should also confirm that another launch attempt will be possible on Sunday, pending completion of the repair efforts.

SATURDAY, JANUARY 11, 2003
2320 GMT (6:20 p.m. EST)

A NASA spokesman says engineers are confident this first stage helium system problem can be fixed overnight to support another countdown on Sunday.

"As just determined by our launch management team, we have scrubbed launch of the Delta vehicle today carrying the ICESat and CHIPSat payloads," agency spokesman Bruce Buckingham said. "That is due to the inability of our team to successfully troubleshoot the helium tank system pressurization problem on the first stage of the Delta. We had a 'red team' at the pad that was valiantly trying to troubleshoot the issue but were unable to do it in a timely manner."

The launch window tomorrow remains the same as today -- 4:45 to 5:30 p.m. PST (7:45 to 8:30 p.m. EST).

"We do have the confidence we can gain access to the troubled areas tonight and fix the problem," Buckingham added. "We have called for a 24-hour scrub turnaround. Activities are proceeding to perform those turnaround operations."

2309 GMT (6:09 p.m. EST)

Securing operations are now being performed by the launch team to ready the Delta 2 rocket and systems for another launch attempt tomorrow. Again, Boeing and NASA have called off today's countdown due to a helium system problem with the vehicle's first stage.

2306 GMT (6:06 p.m. EST)

SCRUB! Officials have just made the decision to scrub for today.

2303 GMT (6:03 p.m. EST)

NASA confirms that this technical problem is with "the helium tank system on the Delta 2 rocket's first stage." Troubleshooting at the launch pad continues. Officials are looking at delaying the target liftoff time from 4:45 p.m. PST (7:45 p.m. EST) to the end of today's window at 5:30 p.m. PST (8:30 p.m. EST) as a result of this problem holding up countdown activities. The countdown clocks are still ticking down, however. It is believed that fueling operations must begin within the hour if the Delta 2 is to fly today.

2258 GMT (5:58 p.m. EST)

The Range reports the C-band beacon checks are completed and good.

2250 GMT (5:50 p.m. EST)

We expect to get some additional information on the nature of this problem and the activities to fix it in about 10 minutes.

2237 GMT (5:37 p.m. EST)

The C-band tracking beacon on the rocket is undergoing its standard pre-launch checkout, which is planned at this point in the countdown. Also continuing is the effort to turn on the rocket's guidance computer. On hold at this hour are vehicle pressurization activities and first stage fueling while the "red crew" is troubleshooting a problem at the pad.

2221 GMT (5:21 p.m. EST)

The troubleshooting team is now at the pad. The launch team has been instructed to remain at their consoles while efforts continue to resolve this technical problem. Assuming the problem is successfully fixed and the special crew leaves the pad, countdown activities will resume for launch.

2207 GMT (5:07 p.m. EST)

So while the team goes into the SLC-2W pad for some unplanned work, most countdown activities are on hold. The clocks continue to tick, however.

The countdown does have some slack time to compensate for such a delay in the timeline. But it remains to be seen if this problem can be resolved fast enough to allow the countdown activities to resume to support an on-time launch. Today's launch window extends for 45 minutes.

2202 GMT (5:02 p.m. EST)

A team is being formed to send back to the launch pad to resolve a technical glitch. Safing operations are underway in advance of the team's arrival.

2145 GMT (4:45 p.m. EST)

T-minus 150 minutes and counting. The Terminal Countdown has begun for today's launch of Boeing Delta 2 rocket with NASA's ICESat and CHIPSat spacecraft. Liftoff is still targeted for 4:45 p.m. PST (7:45 p.m. EST) from Space Launch Complex-2 West at Vandenberg Air Force Base in California. The site is on the Pacific Coast, about 140 miles northwest of Los Angeles.

The available launch window extends for 45 minutes. Officials say there are no COLAs -- Collision Avoidance blackout periods -- for the window today. COLAs prohibit liftoff for a few minutes during a window to ensure a rocket isn't launched on a course that would take it too close to an object already orbiting Earth.

The countdown is being controlled from the "soft blockhouse" located about 8 miles from the Space Launch Complex-2 West pad. Senior launch officials are stationed in the Mission Directors Center located on South Base of Vandenberg.

With the countdown underway, the activities planned over the next hour include verifying the hazard danger area is cleared, activating the rocket's Redundant Inertial Flight Control Assembly guidance computer, pressurizing the first and second stage helium and nitrogen systems and second stage fuel tanks and checking the C-band tracking beacon on the rocket.

The loading of RP-1 kerosene fuel into the rocket's first stage will begin in about 20 minutes. This operation will be followed by loading of super-cold liquid oxygen in about 75 minutes.

2140 GMT (4:40 p.m. EST)

Now five minutes away from picking up the count. The weather is currently reported to be acceptable for launch. Also, a check of upper level winds has revealed favorable conditions.

2136 GMT (4:36 p.m. EST)

The launch team has been polled by the Boeing Launch Conductor to ensure everyone is on console and that all systems are ready to start the Terminal Countdown.

2130 GMT (4:30 p.m. EST)

"Man stations for Terminal Count." That was the message just announced to the launch team in preparation for starting the Terminal Countdown in 15 minutes.

2115 GMT (4:15 p.m. EST)

The launch team is now half-way through this scheduled hour-long hold in the countdown. Meanwhile, safety officials have verified that the SLC-2W launch pad danger area has been cleared of all personnel.

2045 GMT (3:45 p.m. EST)

T-minus 150 minutes and holding. The countdown has just entered a planned 60-minute built-in hold at Vandenberg Air Force Base in California. The senior management team members are taking their consoles to conduct readiness polls of the launch team over the next hour. When the clocks resume ticking the Terminal Countdown will begin, leading to liftoff of the Delta rocket with the ICESat and CHIPSat spacecraft exactly three hours later at 4:45 p.m. local time (7:45 p.m. EST; 0045 GMT).

1647 GMT (11:47 a.m. EST)

The 177-foot tall mobile service tower has begun to roll away from the Delta 2 rocket at the Space Launch Complex-2 West pad, marking a crucial milestone in the preparations for liftoff later today.

The gantry was used to stack the two-stage vehicle, the three strap-on solid rocket motors and payload atop the pad's launch mount. The tower also provided the primary weather protection and access to the rocket during its stay on the oceanside complex on North Vandenberg. Processing for this mission began in mid-October with the erection of the first stage.

Once the tower is secured in its launch position, technicians are scheduled to perform some work on the vehicle's safety destruct system. Later, the final securing of the launch mount is planned. At about 12:45 p.m. local time (3:45 p.m. EST), the pad will be evacuated of all personnel for the remainder of the countdown.

1555 GMT (10:55 a.m. EST)

Launch of the Delta 2 rocket is about nine hours away and the countdown is proceeding along at Vandenberg. Retraction of the mobile service tower has not yet occurred as workers complete final preparations and resolve some minor nits. Liftoff remains set for 4:45 p.m. PST (7:45 p.m. EST).

It is quite foggy at the pad this morning. But forecasters say conditions will improve as the day goes on.

0001 GMT (7:01 p.m. EST Fri.)

Topped with a pair of NASA scientific spacecraft with vastly different missions, a Boeing Delta 2 rocket is slated for launch Saturday from Vandenberg Air Force Base in California.

"We are through the review process and we are ready to go," NASA Launch Director Chuck Dovale told reporters Friday.

Liftoff is targeted to occur at 4:45 p.m. PST (7:45 p.m. EST; 0045 GMT Sunday) from Space Launch Complex-2 West on North Base. The launch team will have 45 minutes to get the rocket off the ground or else wait until Sunday. The window does not change from day to day.

Unlike the troublesome weather that dogged the recent Titan 2 rocket launch from Vandenberg, meteorologists are predicting near-ideal conditions this weekend. Launch Weather Office Capt. Scott Lisko says there is a 90 percent chance of meeting the launch rules on both Saturday and Sunday. The only possible hitch could be mid-level clouds that are too thick for the rocket to safely fly through.

Launch day activities should begin about 14 hours before liftoff time when workers start final preparations at the pad. Managers will receive a detailed weather briefing at 3:30 a.m. local time (6:30 a.m. EST) before giving approval to roll back the protective mobile service tower that shrouds the Delta 2 rocket on the pad.

Tower retraction to expose the rocket for launch will occur between 6 and 8 a.m. local time (9 and 11 a.m. EST), Dovale said. The next few hours are then spent securing the pad and readying the rocket's ordnance safety systems.

Just before 1 p.m. (4 p.m. EST), the pad should be cleared of all personnel in advance of the countdown entering a one-hour planned hold at the T-minus 150 minute mark. Once clocks resume ticking at 1:45 p.m. EST (4:45 p.m. EST), the Terminal Countdown phase of launch operations commence.

The loading of the first stage with a highly refined kerosene fuel is scheduled to start at 2:05 p.m. (5:05 p.m. EST). Super-cold liquid oxygen is then pumped into the stage beginning at 3:00 p.m. (6 p.m. EST).

Two final holds are built into the countdown at T-minus 20 minutes and T-minus 4 minutes. The first pause lasts 20 minutes and the second extends for 10 minutes in duration.

The launch will last about 83 minutes from liftoff until the second of the two payloads is released from the rocket's upper stage. That upper stage, for those of you keeping track, was fueled with storable propellants on December 16.

For a detailed look at the ICESat and CHIPSat spacecraft being launched and the knowledge that scientists hope to gain from the unrelated missions, see this detailed story.

And be sure to check this page for updates on Saturday, starting with confirmation of tower rollback and then play-by-play reports during the final count.

THURSDAY, JANUARY 9, 2003

Mission managers completed the Launch Readiness Review today, clearing the way for entering the final countdown for liftoff. Officials are not reporting any significant issues and the weather forecast has now improved to a 90 percent chance of acceptable conditions for Saturday's launch.

We will have a countdown preview on this page Friday night. And be sure to look here for complete live coverage of Saturday's action.

WEDNESDAY, JANUARY 8, 2003

Postponed from its original launch date of December 19 to replace a faulty ordnance box on the Boeing Delta 2 rocket, preparations for a Saturday liftoff of two NASA satellites are now on schedule at Vandenberg Air Force Base in California.

During the launch delay, workers replaced the box and completed testing of the new unit. The box provides the signal to unlatch and separate the rocket's nose cone during launch, officials said.

Saturday's launch window extends from 4:45 to 5:30 p.m. local time (7:45 to 8:30 p.m. EST; 0045-0130 GMT Sunday).

Air Force meteorologists are calling for an 80 percent chance of favorable weather conditions during the window. Thick clouds are the only concern. The forecast is even better on Sunday with a 90 percent chance of meeting the launch weather rules.

"A weak low pressure system building over the eastern Pacific Ocean will move over central California late Thursday evening, bringing increasing cloudiness and isolated rain showers throughout the day on Friday. This system will move through the area by Saturday morning, and an area of high pressure will build over Vandenberg by Saturday afternoon, bringing favorable weather conditions for the launch attempt," Launch Weather Officer Capt. Scott Lisko said today.

"There will be a few lingering mid-level clouds over Vandenberg during the launch window, creating a slight concern for the thick cloud layer constraint. Upper level winds on launch day will be from the northwest, reaching a maximum of 85 knots near 40,000 feet."

The launch time conditions are expected to include altostratus clouds at 17,000 feet with 3/8ths sky coverage and tops at 20,000 feet, cirrus clouds at 25,000 feet with 2/8ths sky coverage and tops at 28,000 feet, visibility of 7 miles, northerly winds from 330 to 360 degrees at 5 to 10 knots and a temperature of 55 to 60 degrees F.

"Scrub day conditions remain favorable, as high pressure will continue to dominate central California," Lisko said. "The thick cloud layer constraint remains a slight concern, due to a few mid-level clouds lingering over Vandenberg. Upper level winds will be from the west-northwest, reaching a maximum of 100 knots near 40,000 feet."

Watch this page for continued updates and complete live coverage of Saturday's countdown and launch.