BY JUSTIN RAY

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

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SATURDAY, MAY 4, 2002

Touted as a "grand observatory" to study planet Earth's water resources from space, NASA's Aqua satellite flew to its orbital perch Saturday atop a Boeing Delta 2 rocket. Read our full story.

1140 GMT (7:40 a.m. EDT)

NASA reports Aqua's solar array has been deployed and all appears fine in the first quick look at the satellite's health following this morning's launch into space.

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

Following release from the launch vehicle, Aqua is to begin the 12-minute process to cut the cords holding its power-generating solar array in the stowed position. Once that is completed, the array will need about 8 minutes to drive outward to its extended configuration.

We will pause our live launch coverage at this time. Check back later this morning for an update on Aqua's health once ground controllers have had time to examine the data. We will post a full launch wrap-up story later in the day.

1054 GMT (6:54 a.m. EDT)

T+plus 59 minutes, 40 seconds. SPACECRAFT SEPARATION! NASA's Aqua observatory has been deployed into orbit from the Boeing Delta 2 rocket for a six-year mission to improve scientists' understanding of the role water plays in the planet's climate.

1053 GMT (6:53 a.m. EDT)

T+plus 58 minutes. The second stage is maneuvering to the proper deployment orientation.

1052 GMT (6:52 a.m. EDT)

T+plus 57 minutes. Deployment of Aqua from the second stage will occur in a two-step fashion to ensure there aren't any tip-off rates imparted into the spacecraft at separation. At T+plus 59 minutes and 0 seconds, the clamp band around the base of the satellite will be released. Thirty seconds later the secondary latches will be disengaged. Instead of the usual method of springs pushing the satellite away from the rocket, the stage's helium blowdown system will fire to slowly back the rocket away from Aqua.

1051 GMT (6:51 a.m. EDT)

T+plus 56 minutes. The orbit achieved following the just-completed second stage burn has a high point of 371.1 nautical miles, low point of 364.6 nautical miles and inclination of 98.16 degrees. Officials report the orbit is well within the targeted parameters.

1049 GMT (6:49 a.m. EDT)

T+plus 54 minutes, 30 seconds. SECO 2. Confirmation has been received that the second stage engine shut down following the second firing of this launch, completed the powered phase of flight to deliver the Aqua spacecraft into low-Earth orbit.

1049 GMT (6:49 a.m. EDT)

T+plus 54 minutes, 2 seconds. Second stage restart has occurred. The liquid-fueled engine is firing again for an approximate 19-second burn to raise and circularize the current orbit in preparation for deployment of the Aqua satellite.

Meanwhile, acquisition has occurred through the Malindi tracking station in Kenya, Africa.

1048 GMT (6:48 a.m. EDT)

T+plus 53 minutes. Some data drop outs reported.

1047 GMT (6:47 a.m. EDT)

T+plus 52 minutes. Hartebeesthoek has acquired the rocket's signal.

1039 GMT (6:39 a.m. EDT)

T+plus 44 minutes. Now about 10 minutes away from restart of the second stage engine to circularize the orbit for deployment of Aqua. Shortly after the Hartebeesthoek station picks up the rocket, the Malindi site in Kenya should also acquire. Both stations will provide coverage of the 19-second firing of the second stage. Malindi will be the only site to see release of Aqua at T+plus 59 minutes, 30 seconds.

1036 GMT (6:36 a.m. EDT)

T+plus 41 minutes. The Delta 2 is now out of contact with any ground tracking site. The next station to acquire will be the Hartebeesthoek station in South Africa in about 8 minutes.

1035 GMT (6:35 a.m. EDT)

T+plus 40 minutes, 25 seconds. The vehicle has now passed out of range from McMurdo.

1033 GMT (6:33 a.m. EDT)

T+plus 38 minutes. Good quality from the Boeing Delta 2 rocket is still being reported via the McMurdo site as the vehicle flies high above Antarctica.

1029 GMT (6:29 a.m. EDT)

T+plus 34 minutes. The vehicle is in a programmed "BBQ" roll, which allows the second stage and Aqua spacecraft to be thermally heated evenly.

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

T+plus 32 minutes. The McMurdo Tracking Station in Antarctica has acquired the signal of the Delta 2 rocket. Data indicates the vehicle continues in the normal coast mode.

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

T+plus 25 minutes. The quiet coast period continues for the Delta 2 rocket and Aqua. You can see what is left to come, including restart of the second stage and deployment of the spacecraft, on our launch timeline page.

The first firing of the second stage did last about four seconds longer than planned, making up for a slight shortfall from the first stage. But that is what the second stage is supposed to do.

1015 GMT (6:15 a.m. EDT)

T+plus 20 minutes. The Delta rocket is currently flying above the Central Pacific Ocean on generally a southward trajectory. It will pass close to Antarctica before as it begins a northerly pass above the Indian Ocean just off the coast of Africa. You can see some maps of the trajectory here.

1010 GMT (6:10 a.m. EDT)

T+plus 15 minutes. The data to show the exact orbit achieved was not available through the OTTR telemetry relay ship.

The next tracking pass will occur in about 17 minutes when the rocket soars above the McMurdo Tracking Station near the South Pole.

1009 GMT (6:09 a.m. EDT)

T+plus 14 minutes. The vehicle has now passed out of range from the OTTR tracking ship, which is positioned in the Pacific Ocean. The last data relayed from the rocket shows a normal coast was underway.

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

T+plus 12 minutes, 45 seconds. The official Range liftoff time was 0954:58.290 GMT.

1006 GMT (6:06 a.m. EDT)

T+plus 11 minutes, 22 seconds. The second stage engine has shut down as planned. The Delta 2 rocket with the Aqua spacecraft has arrived into a preliminary orbit around Earth.

The Delta rocket is now in a coast period that will last until the second stage restarts at about T+plus 53 minutes, 42 seconds.

1005 GMT (6:05 a.m. EDT)

T+plus 10 minutes. Just over one minute left in this first firing of the Delta 2's second stage. Engine performance reported good.

1004 GMT (6:04 a.m. EDT)

T+plus 9 minutes. Second stage is still firing as planned. No problems reported.

1003 GMT (6:03 a.m. EDT)

T+plus 8 minutes. The Delta 2 rocket is now passing out of range from the Vandenberg tracking station. An Ocean-going Transportable Test & Evaluation Resource, or OTTR, tracking ship will now provide data relay from the rocket back to engineers at Vandenberg.

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

T+plus 6 minutes, 20 seconds. Second stage engine continues to fire normally. Thrust chamber pressure looks good, Boeing reports.

1000 GMT (6:00 a.m. EDT)

T+plus 5 minutes, 50 seconds. Altitude is 82 miles, downrange distance 426 miles, velocity 12,100 miles per hour.

1000 GMT (6:00 a.m. EDT)

T+plus 5 minutes. The protective payload fairing enclosing the Aqua spacecraft atop the rocket has separated.

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

T+plus 4 minutes, 40 seconds. Second stage engine ignition has been confirmed.

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

T+plus 4 minutes, 30 seconds. MECO. The first stage main engine cutoff confirmed, and the spent stage has been jettisoned.

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

T+plus 3 minutes, 30 seconds. Altitude is 46 miles, downrange distance 106 miles, velocity 7,200 mph.

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

T+plus 3 minutes. The first stage main engine and twin vernier thrusters are performing normally. Altitude is 36 miles, downrange distance 54 miles.

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

T+plus 2 minutes, 20 seconds. All three air-lit solid rocket boosters have burned out and jettisoned.

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

T+plus 1 minute, 40 seconds. All six spent ground-start solid rocket motors have been jettisoned now that the rocket has cleared the offshore oil drilling platform. The rocket continues to power toward space on the first stage liquid fueled main engine and the three air-lit solid rocket boosters.

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

T+plus 1 minute, 5 seconds. All six ground-start solid rocket boosters have burned out. Separation will occur once the vehicle passes into a safe drop zone. The three remaining motors strapped to the base of the Delta 2 vehicle have now ignited and will burn for the next minute.

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

T+plus 60 seconds. Now passing through the area of maximum aerodynamic dynamic pressure on the rocket as it climbs into the dense lower altitudes.

0955 GMT (5:55 a.m. EDT)

T+plus 35 seconds. The Delta rocket is now supersonic, traveling more than 700 miles per hour.

0955 GMT (5:55 a.m. EDT)

T+plus 20 seconds. Vehicle has rolled to the proper trajectory to head southward to a polar orbit with the Aqua observatory.

0955 GMT (5:55 a.m. EDT)

LIFTOFF! Liftoff of the Boeing Delta 2 rocket with NASA's Aqua spacecraft -- a new environmental eye on Earth. And the vehicle has cleared the tower.

0954 GMT (5:54 a.m. EDT)

T-minus 30 seconds. Hydraulics and electronics reported go. Launch pad water system has been activated. Ignitors will be armed at T-minus 11 seconds.

The launch ignition sequence will begin at T-minus 2 seconds when a Boeing engineer triggers the engine start switch. The process begins with ignition of the two vernier engines and first stage main engine start. The six solid rocket motors then light at T-0 for liftoff.

0954 GMT (5:54 a.m. EDT)

T-minus 1 minute. The Range has given its final clear-to-launch. The Delta 2 rocket's second stage hydraulic pump has gone to internal power after its pressures were verified acceptable. Also, the first stage liquid oxygen tank is being topped off at 100 percent.

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

T-minus 90 seconds. At the telemetry receiving areas where data from the rocket will be transmitted the data recording charts have gone to high speed.

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

T-minus 2 minutes. The first stage liquid oxygen vents are now being closed so the LOX tank can be pressurized for launch. Puffs of vapor from a relief valve on the rocket will be seen in the remainder of the countdown as the tank pressure stabilizes.

0952 GMT (5:52 a.m. EDT)

T-minus 2 minutes, 30 seconds and counting. The final "go for launch" for the Aqua spacecraft atop the Delta 2 rocket been given from the spacecraft management team.

0952 GMT (5:52 a.m. EDT)

T-minus 3 minutes and counting. The safety destruct safe and arm devices are being armed.

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

T-minus 4 minutes and counting. Now in the final phase of the countdown the Delta 2 rocket's systems begin transferring to internal power for launch. Liftoff set to occur at 0955 GMT today from Vandenberg Air Force Base in California.

0950 GMT (5:50 a.m. EDT)

Now five minutes from launch! Standing by for release of the hold in one minute. All the polling has been completed with the decision made to resume the countdown for an on-time launch today.

0949 GMT (5:49 a.m. EDT)

The Aqua spacecraft has been switched to internal power for its launch into space.

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

The rocket launch team has been polled by the Boeing launch conductor with no problems reported.

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

Now half-way through this 10-minute built-in hold. Standing by for the final pre-launch poll of the launch team to confirm all systems are "go" to resume the countdown for liftoff. Thus far this has been a very smooth countdown.

0940:58 GMT (5:40:58 a.m. EDT)

T-minus 4 minutes and holding. The countdown has entered the final planned built-in hold. This is a scheduled 10-minute pause leading to today's liftoff time of 0954:58 GMT (5:54:58 a.m. EDT).

During the hold officials will poll the various team members behind the scenes, in the "soft blockhouse," Range Operations Control Center and Mission Directors Center.

At this point, all appears set for an on-time launch today. There have been no technical problems reported and the weather is observed and forecast "go" for launch.

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

The vent of the first stage RP-1 fuel tank is being closed and the tank is being pressurized for launch.

0934:58 GMT (5:34:58 a.m. EDT)

T-minus 10 minutes and counting. The countdown is heading to T-minus 4 minutes for a 10-minute hold. Liftoff the Boeing Delta 2 rocket from Vandenberg Air Force Base is still slated to occur at 0954:58 GMT with NASA's Aqua Earth observing satellite.

0932 GMT (5:32 a.m. EDT)

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

0924:58 GMT (5:24:58 a.m. EDT)

T-minus 20 minutes and counting. Countdown clocks are running again following the planned 20-minute hold. The count will continue to the T-minus 4 minute mark where another hold is scheduled. Launch remains set for 0954:58 GMT.

0921 GMT (5:21 a.m. EDT)

The Boeing Launch Conductor has polled the launch team for a "go" to pick up the countdown as planned. No issues were announced. Clocks are set to resume in four minutes.

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

Now half-way through this 20-minute built-in hold in the countdown.

0910 GMT (5:10 a.m. EDT)

The launch weather officer just completed another briefing. Conditions are currently acceptable and forecast to remain within limits this morning's launch. There are low clouds over Vandenberg, but they are not a constraint for launch.

Meanwhile, Range Safety's checks of the computer models, based on today's wind conditions and other factors, show the toxics and debris from an explosion early in the Delta rocket's flight would remain away from populated areas. Also, the modeling continues to indicate that the nozzle covers from the air-lit solid rocket motors will fall within preset safety zones.

0904:58 GMT (5:04:58 a.m. EDT)

T-minus 20 minutes and holding. Clocks have entered the first of two planned hold periods during the last 20 minutes of the Terminal Countdown for today's precise 0954:58 GMT launch time. This pause will last 20 minutes in duration.

These holds are designed to give the launch team a chance to deal with any problems and catch up on work that could be running behind schedule. But at this point, there are no significant issues being addressed on the Delta or Aqua spacecraft.

Engineers have just completed gimbal checks of the nozzles on the first stage main engine and twin vernier engines and second stage engine. This test is performed to ensure the engines will be able to steer the rocket during launch.

0854:58 GMT (4:54:58 a.m. EDT)

Now one hour away from the scheduled liftoff time for the Boeing Delta 2 rocket from Space Launch Complex 2-West at Vandenberg Air Force Base along the central coastline of California. The base is located about half-way between Los Angeles and San Francisco.

Over the next few minutes, the "slew" or steering checks of the first and second stage engines will be performed. Also RF link tests between the Range and rocket are scheduled.

0839:58 GMT (4:39:58 a.m. EDT)

T-minus 45 minutes and counting. Countdown clocks are continuing to the T-minus 20 minute mark where a 20-minute built-in hold is planned. A final 10-minute hold at T-minus 4 minutes will lead to the target liftoff time of 0954:58 GMT this morning for the Boeing Delta 2 rocket.

In the countdown the launch team has finished the work to pressurize the second stage helium, nitrogen and propellant tank pressurizations.

0835 GMT (4:35 a.m. EDT)

The launch team reports the loading of the Delta 2 rocket's first stage liquid oxygen tank was completed at 0835:04 GMT. The operation took 23 minutes and 33 seconds today. The tank will be replenished through the remainder of the countdown to replace the liquid oxygen that naturally boils away.

The rocket is now fully fueled for launch this morning at 0955 GMT (5:55 a.m. EDT; 2:55 a.m. PDT) from Vandenberg Air Force Base in California to deliver NASA's Aqua satellite into space to study Earth's water cycle.

The vehicle's first stage was successfully loaded with RP-1 kerosene fuel along with the liquid oxygen over the past hour-and-a-half. The second stage was loaded with its storable nitrogen tetroxide and Aerozine 50 fuels earlier this week; and the nine strap-on booster rockets are solid-propellant.

There are no technical problems being reported with the rocket or payload, and the weather is looking promising.

0826 GMT (4:26 a.m. EDT)

Liquid oxygen tanking continues, now passing the 15-minute mark in the loading operation.

0816 GMT (4:16 a.m. EDT)

Now five minutes into this approximate 25-minute process to fill the first stage liquid oxygen tank.

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

Right on schedule, cryogenic liquid oxygen, chilled to Minus-298 degrees F, has started flowing from a 28,000-gallon storage tank at Space Launch Complex 2-West, through plumbing and into the bottom of the Boeing Delta 2 rocket. The LOX will be consumed by the first stage main engine during the first four-and-a-half minutes of flight along with the 10,000 gallons of RP-1 kerosene loaded aboard the vehicle during the past hour.

0806 GMT (4:06 a.m. EDT)

The Boeing Launch Conductor has given the launch team a "go" to begin preparations for loading the rocket's first stage liquid oxygen tank as planned.

0754 GMT (3:54 a.m. EDT)

The Air Force launch weather officer has just briefed managers on current and forecast conditions for today's launch of the Boeing Delta 2 rocket. At the 0955 GMT liftoff time today there is a 100 percent chance of meeting the launch weather rules.

The conditions are expected to include stratus clouds at 1,200 to 2,200 feet, visibility of 5 to 7 miles, winds from north at 5 to 10 knots and a temperature of 48 degrees F.

Range Safety also reports the initial checks of the toxics and debris computer models shows acceptable conditions for launch today.

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

The first stage fuel tank of the Boeing Delta 2 rocket has been fully loaded for today's planned 0954:58 GMT (5:54:58 a.m. EDT; 2:54:58 a.m. PDT) liftoff from Vandenberg Air Force Base in California. The tank was loaded with 10,011 gallons of a highly refined kerosene, called RP-1, during a 20-minute process that concluded at 0739:57 GMT.

The next major task in the countdown will be loading super-cold cryogenic liquid oxygen into the first stage starting at about 0810 GMT.

The countdown continues smoothly this morning.

0736 GMT (3:36 a.m. EDT)

The first stage fuel tank has been loaded with 9,000 gallons so far. Once the tank is filled with 9,811 gallons, or 98 percent, the "rapid load" valve will be closed and the slower "fine load" phase will top off the tank to 10,011 gallons for launch.

0732 GMT (3:32 a.m. EDT)

The launch team has computed that the full load for the first stage fuel tank is 10,011 gallons. Over 6,000 gallons are already aboard.

0725 GMT (3:25 a.m. EDT)

Now six minutes into this approximate 20-minute process to load the rocket's first stage with about 10,000 gallons of refined kerosene. Just over 3,000 gallons have been loaded to this point.

Called RP-1, the propellant will be guzzled along with liquid oxygen -- to be pumped into the rocket a little later this morning -- by the first stage Rocketdyne RS-27A main engine and twin vernier steering thrusters during the initial four-and-a-half minutes of flight.

0719 GMT (3:19 a.m. EDT)

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

0715 GMT (3:15 a.m. EDT)

The Boeing launch team is now beginning the steps to prepare 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.

0655 GMT (2:55 a.m. EDT)

T-minus 150 minutes and counting. The Terminal Countdown has begun for today's launch of Boeing Delta 2 rocket with NASA's Aqua environmental research spacecraft. Liftoff remains scheduled for precisely 0954:58 GMT (5:54:58 a.m. EDT; 2:54:58 a.m. PDT) from Space Launch Complex 2-West at Vandenberg Air Force Base in California.

The weather is reported to be within limits and the first check of upper level wind conditions revealed acceptable conditions.

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 kersone 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 at 0810 GMT (4:10 a.m. EDT; 1:10 a.m. PDT).

0646 GMT (2:46 a.m. EDT)

The launch team has been polled by the Boeing Launch Conductor to ensure everyone is on console and all systems are ready to start the Terminal Countdown. The launch pad has been cleared of all personnel for rest of the count. This morning's liftoff is scheduled for 0954:58 GMT (5:54:58 a.m. EDT; 2:54:58 a.m. PDT).

0640 GMT (2:40 a.m. EDT)

"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.

0554:58 GMT (1:54:58 a.m. EDT)

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. Over the next hour, the senior management team will be seated at their consoles to conduct readiness polls of the launch team. When the clocks resume ticking at 0654:58 GMT (2:54:58 a.m. EDT; 11:54:58 p.m. PDT), the Terminal Countdown will begin, leading to liftoff of the Delta rocket and Aqua spacecraft exactly three hours later.

0050 GMT (8:50 p.m. EDT Fri.)

The 177-foot tall mobile service tower has been rolled away from the Delta 2 rocket at the Space Launch Complex 2-West pad over the past few minutes, marking a crucial milestone in the preparations for Saturday's early morning liftoff.

The gantry is used to stack the two-stage vehicle and the nine strap-on solid rocket motors atop the pad's launch mount. The tower also provides the primary weather protection and access to the rocket during its stay on the oceanside complex on North Vandenberg.

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 0600 GMT (2 a.m. EDT; 11 p.m. PDT), the pad will be evacuated of all personnel for the remainder of the countdown.

FRIDAY, MAY 3, 2002

Liftoff of the Aqua spacecraft atop a Boeing Delta 2 rocket is still set for 0955 GMT (5:55 a.m. EDT; 2:55 a.m. PDT) Saturday.

Launch Weather Officer Capt. Greg Fox says there is a 100 percent chance conditions will be favorable for liftoff during Saturday's 10-minute launch window. However, low clouds and fog will mean limited view of the initial portion of flight.

"High pressure continues to build into the area, but has not increased enough to force the marine layer to the surface. As a result, our visibility at the surface has improved from yesterday's forecast, but will still hinder viewing. Upper level winds also continue to weaken, but will remain from the west-southwest with a maximum wind of 32 knots around 45,000 feet," Fox reported today.

The launch time conditions are expected to include complete overcast conditions from 500 feet up to 2,000 feet, visibility of two to four miles, northerly winds from 340 to 360 degrees at 5 to 10 knots and a temperature of 46 to 52 degrees F.

Should the launch be delayed to Sunday, there is again a 100 percent chance of meeting the weather rules.

"Models keep the approaching weak low pressure system well north of California allowing the marine layer to remain firmly entrenched along the Central coast. Surface winds will be light and temperatures will remain relatively cool while upper level winds will increase only slightly - still from the west-southwest at about 40 knots."

Later today technicians will begin countdown activities at the launch pad. Retraction of the mobile service tower from around the Delta 2 rocket is expected at around 0030 GMT (8:30 p.m. EDT; 5:30 p.m. PDT).

Pad securing work will continue through the evening at Vandenberg in preparation for starting the Terminal Countdown at 0655 GMT (2:55 a.m. EDT; 11:55 p.m. PDT) from the T-minus 150 minute mark. Two built-in holds are planned during count. The first will occur at T-minus 20 minutes for a duration of 20 minutes; the second happens at T-minus 4 minutes and should last 10 minutes.

During Terminal Count, the rocket's first stage will be loaded with a highly refined kerosene fuel, called RP-1, starting at 0715 GMT (3:15 a.m. EDT; 12:15 a.m. PDT) and super-cold liquid oxygen at 0810 GMT (4:10 a.m. EDT; 1:10 a.m. PDT).

Other routine pre-launch events during the three-hour countdown include activating the rocket's guidance computer, pressurizing the fuel and oxidizer tanks of the second stage, which were loaded with storable propellants earlier this week, performing engine steering checks and switching onboard systems to internal power.

Watch this page for live coverage of Saturday's countdown and launch with play-by-play updates.

THURSDAY, MAY 2, 2002

Launch of the Boeing Delta 2 rocket with NASA's Aqua spacecraft remains on schedule for the predawn hours Saturday at Vandenberg Air Force Base in California. No technical issues are being worked, officials say. Weather forecasters report there is a zero percent chance conditions will prohibit an on-time liftoff at 0955 GMT (5:55 a.m. EDT; 2:55 a.m. PDT).

We'll post a complete countdown preview on this page on Friday.

WEDNESDAY, MAY 1, 2002

Carrying a price tag of nearly $1 billion, NASA's Aqua environmental satellite is awaiting launch early Saturday for a six-year mission to improve scientists' understanding of the role water plays in the planet's climate.

The three-ton spacecraft will be sent into an orbit around Earth's poles atop a Boeing Delta 2 rocket. Liftoff from Vandenberg Air Force Base on California's Central Coast is expected at precisely 0954:58 GMT (5:54:58 a.m. EDT; 2:54:58 a.m. PDT). The available launch window, which does not change from day to day, extends 10 minutes to 1004:58 GMT.

Air Force meteorologists say there is a 100 percent of meeting the launch rules on Saturday. But despite that rosy forecast, viewing the liftoff will be severely hampered by predicted low clouds and fog.

"An area of high pressure is building into the eastern Pacific bringing favorable conditions for the return of our Central Coast marine layer. Temperatures will remain relatively cool and surface winds will be light as a result of the typical diurnal onshore flow. Upper level winds are expected to be from the west-northwest with a maximum wind of 40 knots around 45,000 feet," Launch Weather Officer Capt. Greg Fox reported in his forecast Wednesday.

The launch time conditions are expected to include complete overcast conditions from the surface up to 1,500 feet, cirrus clouds at 30,000 feet, visibility of one to three miles, northerly winds from 340 to 360 degrees at 5 to 8 knots and a temperature of 46 to 52 degrees F.

Should the launch be delayed to Sunday for some reason, there is a 90 percent chance of acceptable weather.

"The only change for the scrub day forecast is a slight increase in cirrus clouds as a weak low pressure system starts to slide down the Pacific Coast. The marine layer will remain firmly entrenched causing reduced visibilities at the surface. Upper level winds will decrease slightly to about 35 knots - still from the west-northwest," Fox said.

The Aqua spacecraft, built by TRW, features six instruments to gather information of global precipitation, evaporation and the cycling of water on the planet. The satellite is a major part of NASA's Earth Observing System.

"Aqua will observe our Earth's oceans, atmosphere, land, ice and snow covers and vegetation," said Claire Parkinson, the Aqua project scientist at NASA's Goddard Space Flight Center. "This comprehensive approach enables scientists to study the interactions among key elements of the Earth system so as to better understand our planet."

"Aqua will provide unprecedented information on the global water cycle. The spacecraft will enable operational agencies to create more accurate weather forecasts in the future," said Dr. Ghassem Asrar, Associate Administrator for NASA's Earth Science Enterprise.

Aqua is one of the largest and heaviest single satellites ever carried aloft by a Delta 2 rocket. Because of the 21-foot height of the craft, a longer Delta 2 rocket nose cone will be used for the first time on this launch to shroud Aqua as it climbs out of the atmosphere.

"Everyone on the Delta team has dedicated themselves to the time and effort needed to launch and deploy Aqua," said Michael Henderson, Boeing's Aqua program manager. "Our success will set the stage for NASA scientists to embark on a mission that could improve life on Earth."

"It's a lot like running a relay," Henderson said. "The Delta team is at the starting line, ready to launch and deploy the satellite. And just like a relay, proper placement of the baton, or in this case the satellite during the exchange, will help determine the outcome."

It will take 59 minutes and 30 seconds from liftoff until the Delta 2's second stage releases Aqua into the Sun-synchronous orbit 365 by 371 nautical miles above Earth. The deployment will occur above eastern Africa.

Watch this page for complete live updates throughout Saturday's countdown and the launch of Aqua.