BY JUSTIN RAY

Follow the countdown and launch of the Boeing Delta 2 rocket with NASA's Earth Observing System satellite Aura. Reload this page for the very latest on the mission.

1100 GMT (7:00 a.m. EDT)

For the second straight day, technical concerns have scrubbed the launch of NASA's $785-million Aura atmospheric research mission aboard a Boeing Delta 2 rocket.

Worries about the data recorder on the satellite thwarted yesterday's attempt, prompting officials to call off the launch opportunity a half-hour before liftoff. But today's shot got much closer as clocks ticked down the final minutes to launch until suspect battery current measurements on the rocket's second stage triggered an alarm that stopped the countdown.

"At approximately T-minus 3 minutes, we saw an unexpected red alarm called by Telemetry Monitor No. 2. He saw a brief bit-toggle on a battery system expanded measurement. It was not expected, so he properly called the hold," said NASA launch director Chuck Dovale.

"We are establishing a meeting at 5 a.m. (local time) to discuss that issue. That is first and foremost. We need to resolve that issue before we continue with another attempt. Optimistically, we are setting up for a 24-hour (turnaround) in the event we can resolve that issue quickly."

There are several factors that will determine if a 24-hour scrub turnaround will be performed, leading to liftoff at 1002 GMT tomorrow.

"We also need to ensure the spacecraft can support a 24-hour (turnaround) based on their battery capacity margin, which at this time is predicted to be within (range) for a 24-hour turnaround," Dovale said.

"We did just get a brief weather summary for a 24-hour (turnaround). The local weather constraints do rise from what we saw this morning. The probability of violation is up 40 percent.

"There is also a concern for weather down south from here where the P-3 instrumented aircraft is to support. They are possibly to transition through tropical storm-, tropical depression-type weather. So we have to monitor that and we'll decide later this morning whether or not that's a possibility that they can support tomorrow.

"So we have a few hurdles to clear. But we are posturing ourselves for a 24-hour (turnaround). We will let the team know later this morning whether or not we can achieve that."

1027 GMT (6:27 a.m. EDT)

NASA launch director Chuck Dovale says there will be a meeting at 1200 GMT (5 a.m. local time) to discuss the battery current measurements that caused today's scrub.

For now, officials are "optimistically" preparing for another launch try tomorrow. However, that is a very tentative plan.

In addition to resolving the battery measurements on the rocket's second stage, there are concerns about tropical weather in the flight path that the downrange tracking aircraft would take tomorrow. And engineers are assessing the battery capacity on the Aura spacecraft to determine if it permits another launch attempt for the third straight day.

We will update this page later this morning as officials make their decisions on rescheduling the mission.

1020 GMT (6:20 a.m. EDT)

The concerns for the P-3 aircraft tomorrow is tropical weather affecting its trek. The P-3 is a required asset to support the launch.

The local weather forecast at Vandenberg Air Force Base tomorrow is calling for a 40 percent chance of bad weather due to clouds and moisture moving into the area. Similar conditions are expected again on Friday.

1012 GMT (6:12 a.m. EDT)

One concern for a possible launch attempt tomorrow is the availability of the P-3 data relay aircraft that flies downrange to receive telemetry from the Delta 2 rocket during launch. At this point, it is unclear if tomorrow is even an option for launch, NASA indicates.

1007 GMT (6:07 a.m. EDT)

It appears battery current measurements on the Delta 2 rocket's second stage triggered a red alarm, causing the countdown to be halted. The lower limits for these measurements were violated as the rocket was switching to internal power for launch, NASA commentator Bruce Buckingham says.

With no time to assess the problem given the three-minute launch window, the mission had to be scrubbed for today.

Engineers and managers are assessing the situation to determine how to resolve the problem and establish a new launch date.

1001 GMT (6:01 a.m. EDT)

We are still awaiting word on what caused the countdown to be stopped. But there will be no launch today.

0959 GMT (5:59 a.m. EDT)

SCRUB! Since today's launch window extended just three minutes, there is not ample time to recycle the countdown clock and re-attempt liftoff this morning. So this hold has effectively scrubbed the launch for today.

0959 GMT (5:59 a.m. EDT)

The launch team is safing the vehicle after the countdown was halted at approximately T-minus 3 minutes and 15 seconds.

0958 GMT (5:58 a.m. EDT)

HOLD! Countdown has stopped due to a problem.

0958 GMT (5:58 a.m. EDT)

T-minus 3 minutes, 45 seconds and counting. The Delta 2 rocket's systems are now transferring to internal power for launch. And the launch pad water system is being enabled.

0958 GMT (5:58 a.m. EDT)

T-minus 4 minutes and counting! The final phase of the countdown is now underway for the launch of Delta 306 and the Aura atmospheric research satellite. Liftoff is set for 1001:59 from Vandenberg Air Force Base, California.

0957 GMT (5:57 a.m. EDT)

Final approval has been given to restart the countdown clock in one minute.

0956 GMT (5:56 a.m. EDT)

The Aura spacecraft sitting atop the Delta 2 rocket has switched to internal battery power for launch.

0956 GMT (5:56 a.m. EDT)

Countdown will resume in two minutes.

0953 GMT (5:53 a.m. EDT)

The launch team members report a "ready" status to continue the countdown for an on-time liftoff this morning. The team is now receiving final instructions on countdown procedures.

0953 GMT (5:53 a.m. EDT)

The launch team readiness poll is beginning with five minutes remaining in this built-in hold.

0951 GMT (5:51 a.m. EDT)

NASA launch director Chuck Dovale has polled his management team. No problems were voiced. "The NASA team is ready to proceed," Dovale said.

0947:59 GMT (5:47:59 a.m. EDT)

T-minus 4 minutes and holding. The countdown has entered the final planned hold point for today's launch. During this planned 10-minute hold, officials will poll the various team members in the soft blockhouse, Western Range Operations Control Center and Mission Directors Center.

0946 GMT (5:46 a.m. EDT)

The Air Force launch weather officer has declared that conditions are "go" for liftoff today.

0943 GMT (5:43 a.m. EDT)

The first stage propellant tank is being pressurized for launch.

0942 GMT (5:42 a.m. EDT)

Launch is now 20 minutes away.

0938 GMT (5:38 a.m. EDT)

Inhibited checks are now beginning for the Range Safety command destruct receivers that would be used in destroying the Delta rocket should the vehicle veer off course or malfunction during the launch.

0931:59 GMT (5:31:59 a.m. EDT)

T-minus 20 minutes and counting. Clocks are ticking again after the planned 20-minute hold. The countdown will proceed to T-minus 4 minutes where the final hold is scheduled.

0928 GMT (5:28 a.m. EDT)

The Boeing launch team was just polled to confirm everyone is "ready" to continue the countdown. No problems were reported.

0925 GMT (5:25 a.m. EDT)

NASA launch director Chuck Dovale reports that everything is "go" across the board. He just conducted a poll of the space agency's management team to verify readiness to resume the countdown at the end of this hold.

0922 GMT (5:22 a.m. EDT)

Now half-way through this built-in hold at T-minus 20 minutes. Once the countdown resumes, clocks will tick down to the T-minus 4 minute mark where a 10-minute hold is planned.

0920 GMT (5:20 a.m. EDT)

Data link checks are now reported complete.

0911:59 GMT (5:11:59 a.m. EDT)

T-minus 20 minutes and holding. The countdown has entered the 20-minute built-in hold. This pause is designed to give the launch team a chance to work any problems or catch up on activities that might be running behind schedule. Engineers will also have time to examine all the data from the just-completed steering tests. Launch is slated for the precise moment of 1001:59 GMT from Vandenberg Air Force Base, California.

0908 GMT (5:08 a.m. EDT)

The first stage engine steering checks are complete.

0907 GMT (5:07 a.m. EDT)

T-minus 25 minutes and counting. The countdown is nearing a planned 20-minute built-in hold at the T-minus 20 minute mark. Another hold is scheduled at T-minus 4 minutes. Launch is still set to occur at 1002 GMT this morning.

0904 GMT (5:04 a.m. EDT)

The second stage engine slews are complete. First stage tests are starting.

0902 GMT (5:02 a.m. EDT)

The launch team is beginning the "slew" or steering checks of the first and second stage engines. These are gimbal tests of the nozzles on the first stage main engine and twin vernier engines and second stage engine to ensure the rocket will be able to steer itself during launch.

0853 GMT (4:53 a.m. EDT)

There are no constraints to launch, officials say. All systems aboard the Delta 2 rocket and Aura spacecraft are "go" at this time. Also, the weather conditions at Vandenberg Air Force Base are acceptable for liftoff.

0847 GMT (4:47 a.m. EDT)

The countdown is entering the final 75 minutes to launch. Liftoff remains scheduled for 1002 GMT this morning.

0842 GMT (4:42 a.m. EDT)

The launch team reports the loading of the Delta 2 rocket's first stage liquid oxygen tank was completed at 0842:21 GMT. The operation took 24 minutes and 2 seconds today. The tank will be replenished through the countdown to replace the super-cold liquid oxygen that naturally boils away.

The rocket is now fully fueled for launch. The vehicle's first stage was successfully loaded with RP-1 kerosene fuel along with the liquid oxygen this morning. The second stage was filled with its storable nitrogen tetroxide and Aerozine 50 fuels last week. The nine strap-on booster rockets are solid-propellant.

0840 GMT (4:40 a.m. EDT)

Work to activate the Delta rocket's guidance system has been completed.

0833 GMT (4:33 a.m. EDT)

Now 15 minutes into liquid oxygen tanking. Once the first stage tank is 95 percent full, the "rapid load" valve will be closed and the slower "fine load" phase will continue to fill the rocket.

0832 GMT (4:32 a.m. EDT)

Engineers are looking at a slight leak in the liquid oxygen loading system, NASA says. However, the work to fill the first stage continues as scheduled.

0828 GMT (4:28 a.m. EDT)

The normal layer of ice is beginning to form on the rocket's skin as liquid oxgen loading passes the 10-minute point.

0820 GMT (4:20 a.m. EDT)

As this 25-minute cryogenic fueling process gets underway, a plume of white vapor is already streaming from the vent port of the first stage.

0818 GMT (4:18 a.m. EDT)

Super-cold liquid oxygen is beginning to flow into the first stage of the Boeing Delta 2 rocket as the countdown continues for today's 1002 GMT launch.

The liquid oxygen, chilled to Minus-298 degrees F, is being pumped from a launch pad storage tank, through plumbing and into the bottom of the rocket. The LOX and the RP-1 kerosene fuel -- loaded aboard the vehicle earlier this morning -- will be consumed by the first stage main engine.

0812 GMT (4:12 a.m. EDT)

The launch team has received maanagement approval to start preparations to load the rocket's first stage liquid oxygen tank.

0811 GMT (4:11 a.m. EDT)

The Range has completed link checks with the rocket's tracking beacon.

0802 GMT (4:02 a.m. EDT)

Launch is now two hours away.

0740 GMT (3:40 a.m. EDT)

The countdown is continuing very quietly this morning at Vandenberg Air Force Base. Since the first stage fuel loading was accomplished ahead of schedule, this present segment of the count is uneventful. But the tempo will pick up about a half-hour from now with the loading of liquid oxygen into the first stage.

0724 GMT (3:24 a.m. EDT)

The first stage helium and nitrogen system pressurization has been completed.

0707 GMT (3:07 a.m. EDT)

Engineers are starting work to pressurize the helium and nitrogen storage tanks inside the rocket's first and second stages, along with the second stage fuel and oxidizer tanks.

Also, activation of the rocket's guidance control system is underway.

0701:59 GMT (3:01:59 a.m. EDT)

T-minus 150 minutes and counting. The Terminal Countdown is now underway today's launch of the Delta 2 rocket and the Aura satellite. The next three hours will be spent fueling the rocket, activating systems and performing final testing before liftoff at 1001:59 GMT from the SLC-2W pad at Vandenberg Air Force Base, California.

Weather conditions are acceptable and there are no technical problems being reported byy the launch team.

The countdown currently stands at T-minus 150 minutes. However, there are a pair of holds -- totaling 30 minutes in duration -- planned at T-minus 20 minutes and T-minus 4 minutes.

0654 GMT (2:54 a.m. EDT)

The team has been polled for a "ready" status to pick up the countdown.

A "red crew" dispatched to the pad to reconfigure a valve has done its work and is now leaving the area.

0647 GMT (2:47 a.m. EDT)

"Man stations for Terminal Count." The launch team members have been instructed to take positions at their consoles. A readiness poll will be performed in a few minutes to verify everyone is prepared to resume the countdown at the end of this scheduled hold at 0701:59 GMT.

0632 GMT (2:32 a.m. EDT)

Now half-way through this scheduled built-in hold in the countdown.

0602 GMT (2:02 a.m. EDT)

The Boeing Delta 2 rocket's first stage fuel tank has been filled for today's launch of NASA's Aura satellite. The tank was loaded with a highly refined kerosene, called RP-1, during a 19-minute, 18-second process that concluded at 0602:24 GMT.

0601:59 GMT (2:01:59 a.m. EDT)

T-minus 150 minutes and holding. The countdown has entered a planned 60-minute built-in hold. This is the first of three holds scheduled into the count to give workers a chance to catch up on any activities that may be running behind.

Over the next hour, the entire launch team and management will be seated at their consoles. A series of polls will be conducted to verify all is in readiness for entering Terminal Count at end of the built-in hold.

0556 GMT (1:56 a.m. EDT)

The launch team has computed that the full load for the first stage fuel tank is 9,921 gallons. Once the tank is filled to 98 percent, or 9,750 gallons, the "rapid load" valve will be closed and the slower "fine load" phase will continue top off the tank.

0553 GMT (1:53 a.m. EDT)

Now 10 minutes into the first stage fueling process. Over 5,000 gallons have been loaded into the Boeing Delta 2 rocket.

The first stage Rocketdyne RS-27A main engine and twin vernier steering thrusters will consume the fuel along with liquid oxygen during the initial four-and-a-half minutes of flight. The liquid oxygen will be pumped into the rocket later in the countdown.

0543 GMT (1:43 a.m. EDT)

Fueling of the Delta 2 rocket's first stage has started as 10,000 gallons of a highly refined kerosene propellant, called RP-1, begins flowing into the vehicle from a storage tank at the Space Launch Complex-2 West pad.

The RP-1 loading is occurring well ahead of schedule today because workers have to be at the launch pad to monitor the activity. Yesterday, a fuel flow meter problem forced a crew to scramble out to the pad to verify the amount of RP-1 loaded into the rocket. That unplanned event delayed the fueling and put other operations behind schedule.

Once the kerosene is pumped into the Delta 2 rocket today, all workers will clear the hazard area around the pad so the countdown can continue.

0540 GMT (1:40 a.m. EDT)

The Boeing launch team is preparing to re-fill the Delta 2 rocket's first stage with kerosene fuel as the countdown proceeds for this morning's launch.

Following Tuesday's launch delay, the kerosene and liquid oxygen were emptied from the first stage during routine post-scrub operations. The propellants will be re-loaded today, starting with the kerosene.

TUESDAY, JULY 13, 2004
2345 GMT (7:45 p.m. EDT)

The critical data recorder aboard NASA's Aura atmospheric research satellite has been deemed healthy, clearing the way for a second attempt to launch the spacecraft aboard a Boeing Delta 2 rocket. Liftoff is targeted for 1002 GMT (6:02 a.m. EDT; 3:02 a.m. PDT) Wednesday from Vandenberg Air Force Base, California.

"Mission mangers have assessed the Aura spacecraft's solid-state recorder issue that arose during the countdown this morning and have concluded the issue is not a constraint to launch," the space agency said in a statement this evening.

"Engineers are confident that the solid-state recorder is healthy. The issue observed during the countdown had been seen previously during spacecraft testing. There is no concern for loss of science data or the spacecraft's state-of-health."

The device records data from Aura's instruments for later playback to Earth when the satellite makes periodic passes over ground receiving stations.

The weather forecast predicts a 90 percent chance of acceptable conditions at launch time Wednesday. The only slight concern is thick clouds. Here is the outlook from Air Force launch weather officer Capt. Paul Lucyk:

"The ridge of high pressure centered near the Four-Corners extends from northern Arizona through the southern Los Angeles basin. This ridge is just south of Los Angeles and, combined with an upper level trough in the Pacific-Northwest, will continue to bring upper level winds from the southwest.

"Expect to see the marine layer again Wednesday morning with visibility near 1-2 miles as warm air aloft continues. Winds are forecast at 5-10 knots with a loosening gradient by T-0. The high pressure in the desert southwest will begin to shift the mid level flow more southerly which, combined with monsoon moisture, brings a slight concern for thick clouds. Upper level winds will continue from the southwest with maximum of 45 knots near 42,000 feet."

The launch time forecast calls for stratus clouds at 200 feet with 8/8ths sky coverage and tops at 800 feet, cirrus clouds at 20,000 feet with 3/8ths sky coverage and tops at 23,000 feet, visibility of one-to-two miles with fog, northerly winds from 340 to 020 degrees at 5 to 10 knots and a temperature between 53 and 57 degrees F.

Watch this page for live updates during the countdown and launch.

2303 GMT (7:03 p.m. EDT)

Engineers have resolved concerns with the solid-state data recorder aboard the Aura spacecraft, allowing officials to reschedule liftoff for Wednesday morning at 1002 GMT.

More details to follow.

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

Engineers have begun diagnostic testing on Aura's solid-state recorder. Concerns about the device caused officials to stop this morning's countdown and delay launching the $785 million mission for at least 24 hours.

The Aura mission management team will convene a meeting at 2200 GMT (3 p.m. PDT; 6 p.m. EDT) to determine a new launch date.

For now, NASA says liftoff could occur no sooner than Wednesday at 1001:59 GMT (3:01:59 a.m. PDT; 6:01:59 a.m. EDT) from Vandenberg Air Force Base, California.

Aura will ride a Boeing Delta 2 rocket into orbit around Earth's poles where its four instruments will monitor the health of the planet's atmosphere like never before.

0945 GMT (5:45 a.m. EDT)

Worries about a recorder aboard NASA's Aura atmospheric research satellite forced officials to scrub this morning's launch with a half-hour remaining in the countdown at Vandenberg Air Force Base, California.

"As we just heard from our launch director, Chuck Dovale, we are 'no go' for launch this morning," NASA commentator Bruce Buckingham said as the scrub was called a few minutes ago.

"The spacecraft engineers have indicated that there are some concerns, specifically with a solid-state recorder on the spacecraft itself. As they were discussing it through the morning, they determined they could not get comfortable with that particular issue. They would like to take some additional time to make sure they understand what the specific concerns are.

"We don't know if this will be a 24-hour delay or require additional time. We should have that information in the next few hours."

We'll update this page as additional news becomes available.

0936 GMT (5:36 a.m. EDT)

"We have called a 'no go' ... based on a spacecraft issue they have been working with the solid-state recorder," NASA launch director Chuck Dovale told his team in calling the scrub. "They could not resolve it in time...We are not sure if we are at a 24- or 48-hour turnaround (before another launch attempt)."

0930 GMT (5:30 a.m. EDT)

SCRUB! Today's launch of the Aura spacecraft has been postponed due to a problem with a solid-state recorder on the satellite. A new launch date has not been established.

0929 GMT (5:29 a.m. EDT)

The Aura spacecraft team is reporting "no go" for launch today.

0927 GMT (5:27 a.m. EDT)

Five minutes remain in this built-in hold at T-minus 20 minutes. Once the countdown resumes, clocks will tick down to the T-minus 4 minute mark where a 10-minute hold is planned.

0925 GMT (5:25 a.m. EDT)

NASA launch director Chuck Dovale says all systems are "go" on the Delta 2 rocket, the local and downrange Range assets, weather and upper level winds. But the recorder issue on the Aura spacecraft is still being discussed.

Dovale has polled his management team and the space agency is "go" to resume the countdown at the end of this hold.

0920 GMT (5:20 a.m. EDT)

The first stage engine steering checks are complete.

The countdown remains holding at T-minus 20 minutes as expected. The launch team is nearly caught up to the pre-planned schedule. Activities had been running behind due to a problem with a fuel flow meter at the pad.

There is one issue currently being reported by NASA. It involves a recorder on the Aura spacecraft. Officials and engineers are assessing the situtation to determine if this will cause a delay in today's planned launch.

0915 GMT (5:15 a.m. EDT)

After a brief delay, the second stage engine slews are complete. First stage tests have started.

0914 GMT (5:14 a.m. EDT)

NASA spokesman Bruce Buckingham says that spacecraft engineers are discussing concerns with a solid-state recorder on the Aura satellite.

0911:59 GMT (5:11:59 a.m. EDT)

T-minus 20 minutes and holding. The countdown has entered the 20-minute built-in hold.

0909 GMT (5:09 a.m. EDT)

The launch team is beginning the "slew" or steering checks of the first and second stage engines. These are gimbal tests of the nozzles on the first stage main engine and twin vernier engines and second stage engine to ensure the rocket will be able to steer itself during launch.

0907 GMT (5:07 a.m. EDT)

T-minus 25 minutes and counting. The countdown is nearing a planned 20-minute built-in hold at the T-minus 20 minute mark. Another hold is scheduled at T-minus 4 minutes. Launch is still set to occur at 1002 GMT this morning.

0902 GMT (5:02 a.m. EDT)

LOX loading complete! Filling of the Delta 2 rocket's first stage liquid oxygen tank was completed at 0902 GMT. The operation took 24 minutes and 3 seconds today. The tank will be replenished through the countdown to replace the super-cold liquid oxygen that naturally boils away.

The rocket is now fully fueled for launch. The vehicle's first stage was successfully loaded with RP-1 kerosene fuel along with the liquid oxygen over the past hour. The second stage was filled with its storable nitrogen tetroxide and Aerozine 50 fuels last week. The nine strap-on booster rockets are solid-propellant.

0857 GMT (4:57 a.m. EDT)

The Delta rocket's guidance system has been activated for launch.

0852 GMT (4:52 a.m. EDT)

Now 15 minutes into liquid oxygen loading. Once the first stage tank is 95 percent full, the "rapid load" valve will be closed and the slower "fine load" phase will continue to fill the rocket.

0847 GMT (4:47 a.m. EDT)

A plume of white vapor is streaming from the vent port of the first stage as the cryogenic tanking passes the 10-minute mark. And the normal layer of ice is beginning to form on the rocket's skin.

NASA is not reporting any problems as the countdown rolls on.

0844 GMT (4:44 a.m. EDT)

The first stage liquid oxygen loading operation has been underway for seven minutes officially. It will take approximately 25 minutes to fill the rocket's tank.

0838 GMT (4:38 a.m. EDT)

Super-cold liquid oxygen, chilled to Minus-298 degrees F, is being pumped into the first stage of the Boeing Delta 2 rocket as the countdown continues for today's 1002 GMT launch.

The liquid oxygen is flowing from a storage tank at the launch pad, through plumbing and into the bottom of the rocket. The LOX and the RP-1 kerosene fuel -- loaded aboard the vehicle in the past hour -- will be consumed by the first stage main engine.

0834 GMT (4:34 a.m. EDT)

The launch team has been given approval to start preparations to load the rocket's first stage liquid oxygen tank.

0832 GMT (4:32 a.m. EDT)

Now 90 minutes from the launch of the Delta 2 rocket and the Aura environmental spacecraft. The hazard zone around the launch pad has been verified clear again after the special team was sent to the pad due to the fuel flow meter. Activities to begin loading liquid oxygen into the rocket's first stage should start shortly.

0819 GMT (4:19 a.m. EDT)

Fuel loading complete! The Boeing Delta 2 rocket's first stage fuel tank has been filled for today's launch of NASA's Aura satellite. The tank was loaded with a highly refined kerosene, called RP-1, during a 20-minute, 18-second process that concluded at 0819:12 GMT.

Once the workers sent to the pad to deal with the fuel flow meter issue clear the hazard area, the launch team will begin preps to load super-cold cryogenic liquid oxygen into the first stage.

0814 GMT (4:14 a.m. EDT)

The launch team has computed that the full load for the first stage fuel tank is 9,904 gallons. Once the tank is filled to 98 percent, or 9,700 gallons, the "rapid load" valve will be closed and the slower "fine load" phase will continue top off the tank.

0812 GMT (4:12 a.m. EDT)

Fueling continues with 7,000 gallons are already aboard.

0804 GMT (4:04 a.m. EDT)

About 3,000 gallons of kerosene propellant have been loaded into the rocket.

The fuel will be used with liquid oxygen by the first stage Rocketdyne RS-27A main engine and twin vernier steering thrusters during the initial four-and-a-half minutes of flight. The liquid oxygen will be pumped into the rocket later in the countdown.

0800 GMT (4:00 a.m. EDT)

Fueling of the Delta 2 rocket's first stage has begun for today's launch. About 10,000 gallons of a highly refined kerosene propellant, called RP-1, are being pumped into the rocket from a 15,000-gallon storage tank at the Space Launch Complex-2 West pad.

Personnel at the launch pad are assisting after the flow meter problem experienced earlier.

0751 GMT (3:51 a.m. EDT)

Officials remain hopeful that the time being lost to resolve the fuel flow meter problem at the launch pad will be caught up later in the countdown. Launch remains targeted for 1002 GMT this morning.

The countdown has a pair of built-in holds scheduled at T-minus 20 minutes and T-minus 4 minutes that serve as margin to compensate for problems that delay activities like fueling.

0738 GMT (3:38 a.m. EDT)

Fueling of the Delta 2 rocket is on hold. The launch team has found a problem with one of the fuel flow meters that shows how much kerosene is loaded into the rocket. A crew is being dispatched to the pad to troubleshoot the glitch.

0723 GMT (3:23 a.m. EDT)

Boeing technicians are starting preparations for loading the Delta 2 rocket's first stage RP-1 fuel tank. After verifying valves, sensors, flow meters and equipment are ready, the highly-refined kerosene fuel will start flowing into the vehicle.

0722 GMT (3:22 a.m. EDT)

The first stage helium and nitrogen system pressurization has been completed.

0701:59 GMT (3:01:59 a.m. EDT)

Begin Terminal Countdown! The count has entered the final three hours to launch of Boeing's Delta 2 rocket with NASA's Aura spacecraft.

The countdown currently stands at T-minus 150 minutes. However, there are a pair of holds -- totaling 30 minutes in duration -- planned at T-minus 20 minutes and T-minus 4 minutes.

The launch team will spend the Terminal Count prepping the rocket, payload and ground support systems for the planned 1001:59 GMT liftoff from the SLC-2W pad at Vandenberg Air Force Base, California.

Boeing is not reporting any problems and the weather remains 90 percent "go" for launch this morning.

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.

0653 GMT (2:53 a.m. EDT)

The launch team was just polled for a "ready" status to pick up the countdown. Terminal Count will begin as scheduled in just a few minutes for today's launch of the Delta rocket.

0647 GMT (2:47 a.m. EDT)

"Man stations for Terminal Count." The launch team members have been instructed to take positions at their consoles. A readiness poll will be performed in a few minutes to verify everyone is prepared to resume the countdown at the end of this scheduled hold at 0701:59 GMT.

0602 GMT (2:02 a.m. EDT)

T-minus 150 minutes and holding. The countdown has entered a planned 60-minute built-in hold. This is the first of three holds scheduled into the count to give workers a chance to catch up on any activities that may be running behind.

Over the next hour, the entire launch team and management will be seated at their consoles. A series of polls will be conducted to verify all is in readiness for entering Terminal Count at end of the built-in hold.

Launch is still scheduled for 1002 GMT this morning.

0215 GMT (10:15 p.m. EDT Mon.)

The mobile service tower has been retracted from around the Delta 2 rocket at the SLC-2W launch pad as countdown preparations get underway for the overnight blastoff of NASA's Aura spacecraft at 1002 GMT (6:02 a.m. EDT; 3:02 a.m. PDT).

The MST is a structure on wheels that is used to assemble the rocket stages on the pad, provide access for workers and shield the vehicle from the weather.

Workers will spend the next couple of hours getting the pad configured for liftoff. The area will be cleared of all personnel before the Terminal Countdown begins three hours before launch time.

MONDAY, JULY 12, 2004
1700 GMT (1 p.m. EDT)

The weather forecast for tomorrow's launch of the Delta 2 rocket with Aura is still calling for a 90 percent chance of acceptable conditions. Although Vandenber's trademark fog and low visibility will hamper spectators watching the liftoff, meteorologists say only gusty launch pad winds are of concern for violating the weather rules.

Here is the outlook from Capt. Paul Lucyk, the Air Force launch weather officer:

"Vandenberg is currently under the influence of high pressure centered in the Four Corners region. A ridge of high pressure extends from northern Arizona through the southern Los Angeles basin. This ridge is just south of Los Angeles and, combined with an upper level trough in the Pacific-Northwest, will tend to bring upper level winds from the southwest for the next 3-5 days.

"The forecast for Tuesday has tended more toward fog as upper level temperatures continue to warm in response to the ridge in the southwest. As of this morning, models have kept dry air in place at all but the lowest levels. This, combined with upper level warming will push the marine layer lower, which will drive our visibility down."

The launch time forecast calls for stratus clouds at 200 feet with 8/8ths sky coverage and tops at 800 feet, visibility of one-half to one-mile with fog, a temperature between 55 and 60 degrees F, northerly ground-level winds from 340 to 020 degrees at 8 to 12 knots and upper level winds from the southwest with maximum of 55 knots near 42,000 feet.

Should the launch be delayed 24 hours, there is a 90 percent chance of favorable liftoff weather.

"The forecast for Wednesday still calls for a slight change to favor the high pressure in the desert southwest. This raises a concern for monsoon moisture moving through the Los Angeles basin and into eastern Ventura county," Lucyk says.

"Our primary concern for scrub is the 102-foot winds (at the launch pad), but with this moisture, anvil clouds associated with thunderstorm development to the southeast of Vandenberg may be a factor. The anvil concern is slight, as steering winds aloft will continue out of the southwest keeping the majority of the mid and upper level moisture to our east.

"The forecast continues to call for drier air in place but will keep the marine layer stratus at the very lowest levels. Surface winds continue from the northwest at 8-12 knots. Upper level winds will continue from the southeast with maximum of 40 knots at 40,000 feet."

SATURDAY, JULY 10, 2004

Officials have affirmed plans to reschedule the launch of NASA's Aura satellite atop a Boeing Delta 2 rocket for Tuesday morning -- two days later than planned after a problem was found with the pyrotechnic system that jettisons the rocket's nose cone during the climb to space.

Liftoff from the SLC-2 West pad at California's Vandenberg Air Force Base is targeted for a precise time of 1001:59 GMT (6:01:59 a.m. EDT; 3:01:59 a.m. PDT). The day's available window to launch the mission extends just three minutes.

"Yesterday during routine pre-launch checks, engineers discovered an improper assembly of the fairing ordnance detonator connector within the Delta 2 booster fairing. This detonator acts to separate the fairing during flight," NASA said in a statement late Saturday. "Mission managers decided an additional 48 hours was needed to correct the matter."

The problem was a misalignment between cabling and the detonators. Workers had to reposition the hardware to fix the situation, then re-perform pre-flight checks of the pyrotechnic system. The system must work properly to shed the payload shroud at T+plus 4 minutes, 41 seconds.

Countdown activities will begin Monday afternoon at the Vandenberg launch site, which is located about 140 miles northwest of L.A. along the Pacific coastline.

The mobile service tower enclosing the Delta 2 rocket is scheduled for rollback around 5:30 p.m. local time (0030 GMT; 8:30 p.m. EDT). The Terminal Count commences at 12:01 a.m. local (0701 GMT; 3:01 a.m. EDT). The loading of kerosene propellant into the first stage follows 20 minutes later, with liquid oxygen tanking around 1:15 a.m.

Watch this page for live updates throughout the countdown!

1630 GMT (12:30 p.m. EDT)

Work to get an ordnance connector properly aligned on the Delta 2 rocket's payload shroud is expected to delay launch of Aura until Tuesday morning, Boeing says.

The part didn't line up correctly during pre-launch preparations, prompting officials to call off Sunday's scheduled launch opportunity. Efforts are underway to fix the problem to permit the $785 million mission to blast off at 1002 GMT (6:02 a.m. EDT; 3:02 a.m. PDT) Tuesday.

0435 GMT (12:35 a.m. EDT)

DELAY. Troubles with a connector on the Delta 2 rocket's nose cone have forced officials to postpone Sunday morning's attempt to launch the Aura spacecraft from Vandenberg Air Force Base, California.

"We are down at least 24 hours," NASA spokesman Bruce Buckingham said late Friday night.

"The reason is because there is an ordnance separation connector at the base of fairing that is not lining up properly. We don't know why yet. We have engineers off looking at it now. We should have a better understanding of what's ahead of us sometime tomorrow."

The problem has delayed the launch until Monday at the earliest. Liftoff time would be 1002 GMT (6:02 a.m. EDT; 3:02 a.m. PDT). However, further slippage is possible.

"We have engineers meeting through the night. They will be coming back with the options for the management team tomorrow afternoon," Buckingham said Friday night.

The rocket's 10-foot diameter nose cone encloses the Aura satellite during ascent through Earth's atmosphere. Once it is safe to expose the spacecraft -- four minutes and 41 seconds after liftoff -- the fairing is jettisoned in two halves.

FRIDAY, JULY 9, 2004
1550 GMT (11:50 a.m. EDT)

In today's updated launch weather forecast, Air Force meteorologists are still predicting a 90 percent chance of acceptable conditions for Sunday's attempt to launch the Delta 2 rocket with Aura. The only slight concern is wind.

"There is not much change from yesterday's forecast for Vandenberg," Launch Weather Officer Capt. Paul Lucyk said. "We're currently under the influence of weakening high pressure, bringing seasonable marine layer clouds, temperatures, and winds. As we approach Sunday morning, expect the approach of a trough in the Pacific Northwest to bring slightly stronger upper level winds from the southwest. With little associated energy, the trough will not cause disruption to the marine layer so we will continue to see low-level clouds during launch day."

The launch time forecast calls for stratus clouds at 500 feet with 8/8ths sky coverage and tops at 1,800 feet, visibility of five miles with fog, northerly winds from 330 to 360 degrees at 8 to 12 knots and a temperature between 55 and 60 degrees F.

Should the launch be delayed to Monday morning for some reason, forecasters say the weather will be unchanged.

"Expect conditions to remain much the same for scrub day with a bit of an increase in surface and upper-level wind speeds as the upper-level trough slowly moves eastward increasing pressure gradients," Lucyk said.

"We will continue to see marine layer stratus restricting ceilings and visibility but the latest models indicate a slight drying trend, which could allow a peek at the launch. Surface winds are forecast from the north-northwest with velocities in the 8-12 knot range at lift-off. Upper level winds will be from the southwest, reaching a maximum of 65 knots near 45,000 feet."

THURSDAY, JULY 8, 2004

The latest weather forecast is now calling for a 90 percent chance of acceptable conditions on Sunday morning. Here is the outlook issued today:

"Vandenberg is currently under the influence of high pressure, bringing seasonable marine layer clouds, temperatures, and winds. As we approach Sunday morning, expect the approach of a trough in the Pacific Northwest to bring slightly stronger upper level winds from the southwest. With little associated energy, the trough will not cause disruption to the marine layer so we will continue to see low-level clouds during launch day. Surface winds are expected from the northwest at 5-10 knots and upper level winds will be from the southwest with maximum near 43Kft at 55-60 knots. Temperatures for launch will be in the upper 50's Fahrenheit."

1616 GMT (12:16 p.m. EDT)

Mission managers meeting this morning to review the paperwork chase on transistors installed inside the Aura spacecraft have given a "go" for launch Sunday, NASA spokesman George Diller says.

With the issue formally put to rest, technicians have been given approval to begin filling the Delta 2 rocket's second stage with its load of storable propellants today. Also, a mission dress rehearsal is scheduled to occur.

Officials delayed the launch 24 hours so engineers could determine if transistors used on Aura were of concern. The problem stems from an industry-wide alert.

WEDNESDAY, JULY 7, 2004

This weekend's liftoff of NASA's Aura atmospheric research satellite has slipped from Saturday to Sunday so technicians can sort through records to determine if any suspect transistors are installed in the spacecraft.

A Boeing Delta 2 rocket is now scheduled to launch Aura into polar orbit at 1001:57 GMT (6:01:57 a.m. EDT; 3:01:57 a.m. PDT) from Vandenberg Air Force Base, California.

"Earlier this week, engineers began reviewing whether suspect transistors affecting an unrelated non-NASA mission may be aboard the Aura satellite and Delta 2 booster and if this could have any effect on the mission. Today, the Flight Readiness Review was reconvened. Spacecraft engineers decided that an additional day was needed to complete their review, though it was determined that there is not concern with the Delta 2 booster," NASA said in a statement.

As a result of the delay, the loading of storable hypergolic propellants into the rocket's second stage originally slated for today has been postponed to Thursday.

The early weather outlook for Sunday calls for an 80 percent chance of acceptable launch conditions.

"Vandenberg is currently under the influence of high pressure, bringing seasonable marine layer clouds, temperatures and winds. As we approach Saturday morning, expect a trough in the Pacific Northwest to deepen bringing few upper level clouds while sustaining the marine layer. The trough will allow the marine layer to thicken bringing the possibility for drizzle in the overnight hours," the Air Force launch weather officer reported today.

"Expect conditions to remain much the same for (Sunday) with a slight increase in surface and upper-level wind speeds as the upper-level trough slowly moves eastward. We will continue to see marine layer stratus restricting ceilings and visibility. Surface winds are forecast to remain from the northwest with velocities in the 8-12 knot range at liftoff. Upper level winds will be from the west-southwest, reaching a maximum of 60 knots near 45,000 feet."

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

TUESDAY, JUNE 22, 2004

The Aura spacecraft was delivered to launch pad today and hoisted atop the Boeing Delta 2 launch vehicle. Liftoff is now targeted for July 10.

MONDAY, JUNE 21, 2004

Aura's launch has been rescheduled to no earlier than July 10 due to two issues, NASA announced today.

"Additional time was needed to assure that suspect computer chips causing difficulty on a different satellite were not of the same lot as those aboard the Aura spacecraft. Also, the engineering review board needed additional time to clear the concern over the second stage fuel tank shutoff valve failure. It was resolved satisfactorily June 18," the space agency said.

"The spacecraft is at the Astrotech payload processing facility located on North Vandenberg Air Force Base, Calif. Although planned to be moved to Space Launch Complex 2 today, the wind is too high for hoisting atop the Delta 2 rocket. It remains on the transporter in the spacecraft hangar ready for rollout. What effect this may have on the launch date, if any, will be evaluated when the spacecraft arrives at the pad."

WEDNESDAY, JUNE 9, 2004

NASA has set July 8 as the new tentative launch date for the Aura satellite aboard the Delta 2 rocket. The launch window that day would extend from 1001:57 to 1004:57 GMT (6:01:57-6:04:57 a.m. EDT; 3:01:57-3:04:57 a.m. local time).

TUESDAY, JUNE 8, 2004

Engineers must remove a leaky valve on the Boeing Delta 2 rocket before NASA's Aura environmental satellite can be launched from Vandenberg Air Force Base in California, delaying the mission into early July.

The rocket's second stage pressurization system failed a recent test at the Space Launch Complex-2 West pad. That caused the planned June 19 launch date to be postponed, and a new date has not been established.

"The second stage is a pressure-fed system. The pressurization system during checkout on the pad showed a small leak," Boeing mission director Rich Murphy said in an interview Tuesday.

"We've seen these kinds of small leaks before. The engineering (team) decided to cycle a valve that looked like it was leaking. Typically, what will happen is if you cycle this valve it will seal better. Well, we cycled the valve and it leaked worse.

"When that happened, they said 'well, we have to change this valve.' So we are now in the process of changing out that valve.

"It is, unfortunately, a welded-in valve. So they have to cut it out and weld in a new valve. So we are looking at probably early July (for launch)."

The job of replacing the valve won't require the rocket stage to be removed from the launch pad.

"It is doable out on the pad. We just got to get the right folks in," Murphy said.

1935 GMT (3:35 p.m. EDT)

Launch of Aura will be pushed into early July so workers can replace a faulty valve on the rocket's second stage. A new launch date has not been selected. More details later today.

FRIDAY, JUNE 4, 2004

Efforts to resolve an issue with the helium pressurization system of the Boeing Delta 2 rocket's second stage has prompted a one-week delay in the launch of NASA's Aura satellite to study Earth's atmosphere. Liftoff from Vandenberg Air Force Base in California is now targeted for no earlier than Saturday, June 26.

Earlier, workers replaced a suspect hydraulic pump on the rocket. Concerns with the pump forced replacement of a similar device on the Delta 2 rocket being prepped in Florida for next week's launch of the GPS 2R-12 satellite. See coverage of that mission here.

2145 GMT (5:45 p.m. EDT)

Launch of the Delta 2 rocket and the Aura spacecraft has been delayed a week to June 26, NASA has announced.

THURSDAY, JUNE 3, 2004

Delivery of NASA's Aura satellite to its California launch pad was postponed this week while engineers troubleshoot a concern with the Boeing Delta 2 rocket that will lift the $785 million atmospheric research mission into Earth orbit.

Plans had called for Aura to be driven Wednesday from the Astrotech processing building to Space Launch Complex 2-West at Vandenberg Air Force Base, California. Once at the seaside pad, the 23-foot long spacecraft would be hoisted into the tower and bolted to the Delta's upper stage. But those activities are currently on hold.

"A launch site readiness review was conducted on June 1. A subsequent decision was made to delay transportation and mate of the spacecraft to the Delta 2 launch vehicle until an issue with the Delta 2 second stage helium pressurization system is assessed by the launch team," NASA said in a statement Thursday.

What impact, if any, the delay will have on the planned June 19 launch date was unclear late Thursday.

The Aura spacecraft has been at Vandenberg since early April undergoing final testing. Fueling of the satellite was completed May 14, and earlier this week it was encapsulated within a transport canister for the short move to the pad.

Assembly of the Delta 2 rocket atop the launch pad began April 29 with erection of the first stage. The second stage was added May 1. Attachment of the nine strap-on solid rocket motors was finished by May 5. A countdown dress rehearsal in which the first stage was loaded with super-cold liquid oxygen occurred May 21.

This is the same launch site used April 20 when a Delta 2 rocket carried NASA's Gravity Probe-B craft into space to test Einstein's theory of relativity.

Aura is the next in a series of satellites for NASA's Earth Observing System. Flying 438 miles above the planet, Aura will use its four instruments to observe the composition and chemistry in the atmosphere.

The mission aims to answer three environmental questions:

• 1. Is the stratospheric ozone layer recovering?
• 2. What are the processes controlling air quality?
• 3. How is the Earth's climate changing?