BY JUSTIN RAY

Follow the countdown and launch of the Boeing Delta 2 rocket with NASA's Mars Exploration Rover-B. Reload this page for the very latest on the mission.

0054 GMT (8:54 p.m. EDT Mon.)
Now three minutes into this approximate 25-minute process to fill the first stage liquid oxygen tank. A plume of white vapor is now streaming from the vent port of the first stage.

All continues to go well in tonight's countdown. Engineers are examining voltage measurements from the newly installed flight termination system battery on the rocket. But to repeat -- officials say this isn't a concern for launch.

0051 GMT (8:51 p.m. EDT Mon.)
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 10:35 p.m. EDT launch attempt.

The liquid oxygen is flowing from a storage tank at pad 17B, through plumbing and into the bottom of the rocket. The LOX and the RP-1 kerosene fuel loaded aboard the vehicle in the last half-hour will be consumed by the first stage main engine.

0045 GMT (8:45 p.m. EDT Mon.)
The "go" has been given to the launch team to begin preparations for loading the rocket's first stage liquid oxygen tank.

Here is some clarification on the battery issue. The launch team is seeing some voltage readings that are slightly different than expected. But the readings are within family. This is not considered to be a problem for the countdown tonight.

The voltage readings being discussed are from the replacement battery installed on the Delta 2 rocket's flight termination system yesterday.

0039 GMT (8:39 p.m. EDT Mon.)
NASA Launch Manager Omar Baez just polled his team for a readiness to begin liquid oxygen tanking operations. He did mention a battery issue that is being examined. NASA is awaiting a briefing from Boeing on the situation.

A NASA spokesman said a short time ago that no problems where being worked.

0035 GMT (8:35 p.m. EDT Mon.)
The countdown has now entered the final two hours until launch. There are no technical problems being reported by the launch team and the weather is near-perfect tonight. Liftoff of the Delta 2 rocket and Mars rover Opportunity remains scheduled to occur at 10:35:23 p.m. EDT (0235:23 GMT).

A backup launch time is available at 11:18:15 p.m. EDT (0318:15 GMT), if needed.

0032 GMT (8:32 p.m. EDT Mon.)
Launch Weather Officer Joel Tumbiolo just gave another briefing to the management team in advance of loading the first stage liquid oxygen tank. The weather situation continues to look favorable with no major worries at this time. The prediction of meeting the launch weather rules has improved to a 90 percent chance.

0019 GMT (8:19 p.m. EDT Mon.)
The first stage fuel tank of the Boeing Delta 2 rocket has been fully loaded for today's planned 10:35 p.m. EDT liftoff from Cape Canaveral Air Force Station in Florida.

The tank was filled with a highly refined kerosene, called RP-1, during a 18-minute, 41-second process that concluded at 8:19 p.m. EDT.

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

0012 GMT (8:12 p.m. EDT Mon.)
The launch team has computed that the full load for the first stage fuel tank is 9,988 gallons. Over 7,000 gallons are already aboard.

Once the tank is filled with 9,800 gallons, or 98 percent, the "rapid load" valve will be closed and the slower "fine load" phase will continue top off the tank.

0009 GMT (8:09 p.m. EDT Mon.)
This approximate 20-minute process to load the rocket's first stage with about 10,000 gallons of refined kerosene fuel continues with no problems. Over 5,000 gallons have been loaded to this point.

0005 GMT (8:05 p.m. EDT Mon.)
Now five minutes into the RP-1 loading process. Nearly 3,000 gallons are aboard the rocket.

0000 GMT (8:00 p.m. EDT Mon.)
About 10,000 gallons of a highly refined kerosene propellant, called RP-1, are now being pumped into the base of the rocket from a storage tank at pad 17B. The fuel will be used along with liquid oxygen -- to be loaded into the rocket -- in about an hour by the first stage RS-27A main engine.

MONDAY, JULY 7, 2003
2358 GMT (7:58 p.m. EDT)

The Boeing launch team is currently working through the steps to prepare for loading the Delta 2 rocket's first stage fuel tank. After verifying valves, sensors, flow meters and equipment are ready, the highly refined kerosene fuel will start flowing into the vehicle.

2356 GMT (7:56 p.m. EDT)
Launch Weather Officer Joel Tumbiolo has just completed a briefing to mission managers. "We are looking in real good shape," he reported.

There is no rain in the area and no troublesome anvil clouds moving in our direction. Some thin high clouds are moving through but there is clear skies behind them.

All weather rules are currently "go" for launch and expected to remain that way.

2355 GMT (7:55 p.m. EDT)
The launch team has been given the "go" to begin loading RP-1 propellant into the Boeing Delta 2 rocket's first stage.

2335 GMT (7:35 p.m. EDT)
T-minus 150 minutes and counting. The second Terminal Countdown has begun for NASA's Mars Exploration Rover-B, named Opportunity, aboard the debut flight of Boeing's Delta 2-Heavy rocket.

Over the next three hours, the launch team will ready the three-stage rocket, payload and ground support systems for the planned 10:35:23 p.m. EDT (0235:23 GMT) blastoff from pad 17B at Cape Canaveral Air Force Station in Florida.

With the countdown underway, the Complex 17 area will be verified cleared of workers as a safety precaution. A warning horn will be sounded at the seaside complex to alert personnel to depart and head back to road blocks.

Upcoming in the next few minutes, launch team members in the Delta Operations Building, or "soft blockhouse", located about eight miles west of the pad will oversee the pressurization of helium and nitrogen storage tanks inside the rocket's first and second stages; and the second stage fuel and oxidizer tanks will be pressurized for launch. In addition, the Delta's onboard guidance computer -- called the Redundant Inertial Flight Control Assembly or RIFCA -- will be turned on and configured for the mission.

The loading of 10,000 gallons of RP-1 fuel into the first stage is scheduled to start about 20 minutes from now.

The local weather conditions are promising for liftoff. Forecasters are still calling for an 80 percent chance of acceptable weather tonight.

Also, there are no COLAs tonight. These Collision Avoidance periods are blackouts that prohibit liftoff so the rocket can't be launched on a course that would take it too close to an object already in orbit.

2326 GMT (7:26 p.m. EDT)
The launch team has been polled to ensure all console stations are manned and that systems are ready to continue with the countdown. The Terminal Countdown will start in about 9 minutes.

2315 GMT (7:15 p.m. EDT)
Twenty minutes are remaining in this hold. Polls of the launch team are upcoming before the countdown resumes.

2235 GMT (6:35 p.m. EDT)
T-minus 150 minutes and holding. Clocks at Cape Canaveral have entered a scheduled 60-minute built-in hold in advance of the Terminal Countdown. Liftoff of the Delta 2 rocket is now exactly four hours away.

2112 GMT (5:12 p.m. EDT)
The Delta 2 rocket and the Mars Exploration Rover Opportunity stand ready for launch tonight from pad 17B at Cape Canaveral Air Force Station, Florida.

The mobile service tower has been retracted. Now, workers will be securing the structure in its launch location.

The Terminal Countdown remains scheduled to begin at 7:35 p.m. EDT.

2042 GMT (4:42 p.m. EDT)
The metal cocoon-like mobile service tower is beginning to roll away from the Boeing Delta 2-Heavy rocket at Cape Canaveral's launch pad 17B as the countdown continues for this evening's 10:35 p.m. EDT liftoff.

The tower structure is used to stack the rocket's stages and boosters together, hoist the Mars Exploration Rover spacecraft atop the vehicle and provide weather protection.

2010 GMT (4:10 p.m. EDT)
The sliding doors on the backside of the mobile service tower have been opened in preparation for rolling the tower away from the Boeing Delta 2 rocket this afternoon.

1900 GMT (3:00 p.m. EDT)
A final launch readiness review meeting is being held this afternoon between Boeing, NASA and the Air Force to provide a last confirmation that all systems are "go" for liftoff later tonight. The rollback of the mobile service tower will occur around 4 p.m. EDT, after the meeting is concluded.

1510 GMT (11:10 a.m. EDT)
The weather forecast for tonight's launch attempt is generally favorable. Air Force meteorologists are predicting an 80 percent chance of meeting the launch weather rules. See the full forecast here.

0030 GMT (8:30 p.m. EDT Sun.)
After a nine-day wait to fix problems with its launcher, NASA's Mars Exploration Rover Opportunity will take its second shot at departing Earth on Monday night aboard a Boeing Delta 2-Heavy rocket from Cape Canaveral, Florida.

Liftoff is scheduled for 10:35:23 p.m. EDT (0235:23 GMT). A backup launch time is available at 11:18:15 p.m. EDT (0318:15 GMT).

The first countdown for Opportunity occurred on Saturday, June 28. But Range Safety issues combined with unacceptable high-altitude winds forced the launch to be scrubbed. Hours later, workers found sections of thermal insulating material on the Delta 2 rocket's exterior had come loose from the first stage liquid oxygen tank.

Efforts to repair the debonded cork and understand the problem took almost a week, culminating with a liquid oxygen tanking test on Saturday morning. Although some cork again separated from the rocket's skin, engineers were able to reattach the insulation using a different, stronger adhesive.

The most recent glitch, which delayed liftoff from Sunday to Monday night, was the failure of a battery in the rocket's safety destruct system. Replacement of the faulty battery was underway Sunday.

"Mission managers reported at 6 p.m. today that everything is on track to replace a battery with a failed cell associated with a component of the launch vehicle's flight termination system," a NASA spokesman said Sunday. "Based on an expected successful installation and evaluation of the new battery tonight and tomorrow morning, mission managers were able to schedule Monday's launch attempt."

The mobile service tower enclosing the Delta 2 will be retracted to the launch position mid-day Monday. The Terminal Countdown will commence at 7:35 p.m. EDT.

Watch this page for live reports throughout the countdown and launch of the Opportunity rover!

SUNDAY, JULY 6, 2003
The latest report from NASA:

The launch of the MER-B Mars Exploration Rover "Opportunity" aboard a Boeing Delta 2 rocket has been postponed an additional 24 hours. The delay is due to the failure of a battery cell associated with a component of the launch vehicle's flight termination system. The battery must be removed and replaced.

Launch is now targeted for no earlier than Monday, July 7. The two launch times available are 10:35:23 and 11:18:15 p.m. EDT. The forecast calls for a 30 percent chance of not meeting the launch weather criteria on Monday evening.

At Pad 17B, a tanking test of the Delta rocket was conducted Saturday morning. The first stage was loaded with cryogenic liquid oxygen to evaluate the bonding of the lower band of cork thermal insulation. Saturday afternoon, NASA and Boeing managers met to discuss the outcome of the tanking test and other associated testing and engineering evaluations that have been conducted over the last several days.

After the tanking, inspections revealed some selective debonding of the cork from the surface of the vehicle within a limited area. These locations are being repaired using a different adhesive with a stronger bonding characteristic as demonstrated by tests conducted at KSC late this week. This work was completed Saturday night and the problem has been resolved to the satisfaction of engineers.

0355 GMT (11:55 p.m. EDT Sat.)
ANOTHER DELAY. Problems with a battery on the Delta 2 rocket's flight termination system has forced another launch delay for the Mars Exploration Rover Opportunity. Liftoff is now targeted for no sooner than Monday night.

Monday's launch times are: 10:35:23 p.m. and 11:18:15 p.m. EDT.

We'll post a full update shortly to recap Saturday's liquid oxygen tanking test and the results. Officials had expected to launch Sunday night based on the success of the cork insulation repairs.

THURSDAY, JULY 3, 2003
1245 GMT (8:45 a.m. EDT)

NASA confirms the further slip in the Opportunity rover's launch to Sunday, as we reported last evening. The liquid oxygen loading test for the Delta 2 rocket's first stage is scheduled for Saturday to confirm repairs made to cork insulation have worked. A Launch Readiness Review will follow Saturday afternoon to determine whether to proceed with the countdown on Sunday.

0010 GMT (8:10 p.m. EDT Wed.)
Launch of the Mars rover Opportunity is expected to slip to Sunday night, sources say. NASA is still reviewing analysis and hasn't confirmed the next launch attempt. A liquid oxygen tanking test is likely to occur Saturday morning.

Sunday's launch times will be 10:43:16 p.m. and 11:26:02 p.m. EDT.

The weather forecast for Sunday calls for a 70 percent chance of good conditions.

WEDNESDAY, JULY 2, 2003

Testing and meetings continue for engineers and mission managers today. No news is expected from NASA until Thursday morning.

Meanwhile, the weather forecast for a possible Saturday night launch opportunity is available here.

TUESDAY, JULY 1, 2003
1600 GMT (12:00 p.m. EDT)

Officials could decide by late Wednesday whether to perform a special liquid oxygen loading test on the Boeing Delta 2 rocket to ensure repaired insulation stays adhered to the booster's first stage, NASA Launch Manager Omar Baez told reporters a short time ago.

If and when the test is conducted at Cape Canaveral Air Force Station's pad 17B will determine the target launch date for the Mars Exploration Rover Opportunity aboard its Boeing Delta 2-Heavy rocket.

A section of cork insulation on the rocket -- about 40 feet above the launch pad surface -- came loose following Saturday night's launch attempt. Insulation in that area of the first stage, behind the tops of the solid rocket motors, was removed and replaced last week due to debonding issues.

Early Sunday morning during post-scrub activities at the pad, workers discovered portions of the material had again come loose from the rocket's exterior.

"We had the cork physically raise itself, about a third of it, where we had the bond fail to adhere to the aluminium skin of the tank," Baez said. "The biggest section is about 22 inches by about 19 inches...that we saw unbonded."

Engineers aren't sure if the liquid oxygen tank's contraction during the loading of the cryogenic propellant caused the cork to peel away or if the debonding happened when the tank was drained. The super-cold liquid oxygen is chilled to Minus-298 degrees F.

"We are trying to determine: did it happen after we warmed up? Did it happen when we were cooling down? We don't know that," Baez said. "We are off doing tests to determine that. My guess is it is probably happening as the tank is re-expanding after the tank has gone through its cryo cycle."

For now, NASA hopes to take another shot at launching the Mars Opportunity rover this Saturday. But the space agency and rocket-maker Boeing could delay the liftoff further to finish testing.

Efforts to reinstall the cork have been completed, Baez said, but testing and analytical efforts continue to figure out what is causing the frustrating situation.

"Saturday is truly viable. There is some risk to it, I have to tell you that up front. We have already bonded the cork back on, it is under a vacuum bag as we speak to take moisture out and keep conditions out. And then we will let it air dry for two or three days.

"In addition to that, we have taken multiple samples of this adhesive and we are doing pull-and-peel tests on it at ambient conditions, some at cryo conditions and some that have been cycled through an ambient and cryo cycle. So we are going to pull-and-peel tests to determine the strength of this adhesive under those conditions.

"The other things we are doing are the analytical approach to these things," Baez said.

"There are several analysis teams off looking. One of the things we are looking at is do we need to fly with cork at all? There is a school of thought out there that says we don't even need the cork...There is another school out there searching for if we lost all or just a portion of this 'belly band', how much can we stand and how much temperature rise would there be."

An ultimate test could be performed as early as Thursday when liquid oxygen is pumped into the Delta 2 rocket and then draining, allowing engineers to see if the cork remains attached to the vehicle. Allotting the time perform the test would probably delay the launch at least another day.

"Saturday becomes iffy. It would more likely be Sunday," Baez acknowledged.

"The tanking test is to feel good about what we did. Did this thing bond? Can it take a cryo and warm up cycle?"

The first stage has been standing on the launch pad for several months after having been originally stacked to carry NASA's Space Infrared Telescope Facility into space in April. But worries with delaminations found in the nozzles of solid rocket boosters prompted officials to delay the observatory's mission until after the Mars rover launch. NASA and Boeing opted to leave the rocket stage in place and use it to fly Opportunity.

"This is the booster we were going to use for SIRTF. So it has been sitting out there in that environment since late February. We did do a cryo load during the SIRTF (launch campaign). We believe we got some of moisture trapped behind the cork...(which) expands the cork. The prudent thing is what we did; we removed all the cork that was expanded. We replaced it with new cork.

"Usually we will do a cryo load 13 days (before launch). We load LOX onboard to check the integrity of the tank. Sometimes we will see this kind of damage and we will repair those areas using the methods we are using now. Yet that gets to cure for the 10 or 11 days between that point and launch."

Baez said testing has suggested that the shorter time between the repairs last week and the first launch attempt Saturday night might not have given the adhesive enough time to set.

"One of the things that the lab samples told us was that the adhesive wasn't fully cured."

If the decision is made to perform a liquid oxygen test and officials conclude that the latest repairs should be given more time to cure, the tanking test could slip to Saturday. Under such a situation, liftoff would then slip to Sunday or Monday.

The quarter-inch thick cork is an insulator that protects the liquid oxygen tank from the high temperatures of ascent.

"The only portion of the flight we are really concerned with is when we are flying the air-lit solids," Baez said. "It is that portion from 13 nautical miles to 36 nautical miles when we are flying the three air-lit solids."

During the launch of the Mars rover Spirit aboard a Boeing Delta 2 rocket June 10, a camera mounted on the first stage showed the forward tips of the air-lit boosters turn black from the heat about two minutes after liftoff.

"You notice the forward cones on the solid rocket motors are getting toasty. That is the aero loads on it. It gets very hot up there as this thing is screaming through the atmosphere. The impingement, or that plume, coming off the noses of those three solids obviously is going out 360 degrees, but one quadrant of it is headed for that vehicle and that is what we are trying to protect against."

Baez said the concern delaying the launch is not what would happen if the cork detached during launch and impacted part of the rocket, but rather the loss of thermal protection to the first stage liquid oxygen tank.

"The piece would not have damaged the rocket. We have fairings over everything below that to protect it. So you would never see a Columbia-type scenario," Baez said. Investigators believe a chunk of foam insulation from the shuttle's external fuel tank struck Columbia's left wing during launch, dooming the orbiter and crew during reentry.

"The worst case scenario is we may have had some decreased strength in the tank. We are talking about aluminum and it is about a sixteenth-of-an-inch thick on the skin with a three-quarter-inch isogrid behind it. So it is very structurally stable aluminum. We could have lost some of the strength properties in that.

"The absolute worst case is we would have breached the tank, had a LOX leak and possibly loss of mission. It could be that bad. But things have to align just perfectly for that to happen."

Is Baez happy that the rocket didn't launch on Saturday night?

"I consider ourselves lucky. But I got to think back and say 'you know, we haven't done anything very different on this tank that we've done before.' So I got to think we have flown before with some of this cork debonded and we haven't suffered any kind of failure."

In the back of mission managers' minds is the looming July 15 deadline to launch Opportunity to Mars. If the rover misses its planetary alignment window, it will be four years before launch conditions are right to dispatch the spacecraft the Red Planet. The next Mars launch window in 26 months isn't suitable for the Mars Exploration Rover, Baez explained.

"I don't want to fly where I put the mission at risk. This thing could end up in a museum or could fly again in four years. But I am not going to risk the mission just because I have a deadline approaching," Baez said.

"What is killing us is it is a very simple mechanism there and we are having a very hard time fixing that simple mechanism. It is purely this cork bonded to an aluminum skin and we're having a heck of time keeping it on there."

MONDAY, JUNE 30, 2003
1955 GMT (3:55 p.m. EDT)

Launch of Delta 2 rocket and Mars rover Opportunity has been delayed to Saturday night, NASA officials announced today. The further slip in the liftoff will give workers more time to fix loose insulating material on the rocket's first stage and perform tests.

NASA is planning a news briefing Tuesday morning. We'll update this page with details following the event.

Saturday's two instantaneous launch times are: 10:51:25 p.m. and 11:34:05 p.m. EDT.

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

The chance to launch the Opportunity rover on Wednesday evening now appears in doubt. There is a large amount of work facing teams to repair the cork insulation and to understand what is causing the problems.

An official update from NASA could come later today.

SUNDAY, JUNE 29, 2003
2245 GMT (6:45 p.m. EDT)

The 300 million mile voyage from Earth to Mars for NASA's Opportunity rover won't begin until at least Wednesday night so workers can fix a ring of insulating material on the Boeing Delta 2 rocket.

For the second time in eight days, officials have been forced to postpone the Mars Exploration Rover-B launch to make repairs on the troublesome band of cork on the rocket's first stage.

Last week the band was removed and replaced after technicians discovered that the cork and the adhesive were not bonding properly, NASA said. Inspections performed early Sunday -- after super-cold liquid oxygen was drained from the first stage following the scrubbed countdown -- revealed sections of the new band were not adhering to the rocket's skin, the space agency announced.

"They aren't sure what is causing these problems," NASA spokesman George Diller said.

Problem areas of the ring -- about 10 percent of the entire band -- will have to be reinstalled before the Wednesday night launch attempt, NASA said.

The cork material is used to provide thermal protection on the rocket. The insulator shields against the heating of ascent.

Located near the forward attach points of the strap-on solid rocket boosters, the band extends all the way around the first stage. It is about two-feet in width and a quarter-inch thick, according to NASA.

The two available launch times on Wednesday night are: 11:17:37 p.m. and 11:59:54 p.m. EDT.

The Opportunity rover's window to make its departure for Mars extends to July 15.

2230 GMT (6:30 p.m. EDT)

Launch has been delayed until Wednesday night. Details to follow.

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

Managers and engineers are still meeting to decide what needs to be done with a band of insulating material on the Delta 2 rocket's first stage. Following last night's scrub, workers inspected the launch vehicle and found the strip of cork material wasn't adhering to the rocket's skin. This is the same band of cork that was replaced several days ago, a NASA spokesman said.

1645 GMT (12:45 p.m. EDT)

ANOTHER DELAY. Tonight's launch attempt has been called off while engineers assess concerns with insulation on the Boeing Delta 2 rocket. Meetings are planned today to discuss the situation.

"Problems have arisen with the cork insulation on the Delta first stage, which must be analyzed and resolved before a launch can occur," NASA spokesman George Diller said.

The earliest that launch of the Mars rover Opportunity would happen is Monday evening.

This mission was already delayed three days to replace a band of cork insulation on the rocket.

Watch this page for more information as it becomes available.

0615 GMT (2:15 a.m. EDT)

Launch Weather Officer Joel Tumbiolo is predicting a 60 percent chance of unacceptable conditions for Sunday night's launch attempt. See the full forecast here.

The forecast does not take into count the high-altitude winds because those conditions are not considered a "weather" issue. The upper level winds are a rocket issue, meaning they affect the control and structural limits of the launch vehicle. As such, they are handled separately from the ground weather conditions.

0438 GMT (12:38 a.m. EDT)

The launch team is now preparing to drain the cryogenic liquid oxygen from the Delta 2's first stage. Post-scrub activities will continue over the next couple of hours.

The launch team will begin a fresh countdown mid-day Sunday.

This will conclude our play-by-play call of this launch attempt. Watch this page for updates throughout Sunday evening's countdown.

0432 GMT (12:32 a.m. EDT)

After dealing with weather worries, toxics concerns and a boat in the launch hazard area, a last-minute problem with high-altitude winds has scrubbed today's launch of the Mars Exploration Rover Opportunity aboard the Boeing Delta 2 rocket.

Liftoff is now targeted for Sunday night at 11:46:14 p.m. EDT. A back-up launch attempt is available less than an hour later at 12:28:07 a.m. EDT.

0431 GMT (12:31 a.m. EDT)

SCRUB. A high-altitude wind shear has been measured by the latest weather balloon. So officials have been forced to pass up the 12:38 a.m. EDT launch attempt.

0431 GMT (12:31 a.m. EDT)

NO GO status called due to the winds. Countdown will not resume.

0430 GMT (12:30 a.m. EDT)

Weather is GO for launch. The cloud conditions are verified acceptable for the launch at 12:38 a.m. EDT.

The launch team has been polled by the Boeing Launch Conductor for a "go" to proceed with the countdown. No problems were reported. The team is now receiving final instructions on countdown procedures.

0429 GMT (12:29 a.m. EDT)

NASA Launch Manager Omar Baez is polling his team for a readiness to continue with the countdown. There are no technical problems being worked. It is just a question of the weather cooperating.

0426 GMT (12:26 a.m. EDT)

The weather team is still waiting on the aircraft data. Meanwhile, Tumbiolo reports that the vast area of rain to the west will begin moving into the area in about two hours. Officials were interested in that timing since -- if the launch is scrubbed -- the rocket would be sitting exposed on the pad for a while until the mobile service tower is rolled back around the vehicle.

0421 GMT (12:21 a.m. EDT)

If the weather should remain "go" for launch, the countdown would resume at 12:33:59 a.m. EDT from the T-minus 4 minute mark.

0419 GMT (12:19 a.m. EDT)

Launch Weather Officer Joel Tumbiolo says he's waiting for more data from the weather reconnaissance aircraft to determine if the anvil clouds in the area are acceptable for the Delta 2 rocket to launch tonight. Anvils within 10 nautical miles is the concern.

0416 GMT (12:16 a.m. EDT)

Toxics and the launch hazard area remain "go" for launch. Those were the two problems that forced the first launch time to be passed up. The concern for the second launch time is the weather. There is a weather system moving from the west coast of Florida that could impact the Cape Canaveral area before the 12:38 a.m. EDT liftoff time.

0409 GMT (12:09 a.m. EDT)

Another weather briefing will be performed in about nine minutes.

0408 GMT (12:08 a.m. EDT)

The mission constants have been reloaded. This is the software update in support of the second launch attempt tonight.

0402 GMT (12:02 a.m. EDT)

So the wait continues for the next shot to launch the Mars rover on the proper trajectory for its 305-million-mile trek to the Red Planet. That instant in time is 12:37:59 a.m. EDT. If the weather drifting from the west stays far enough away, the Delta 2 should be able to head skyward tonight.

If this second attempt is called off for some reason, liftoff will be delayed 24 hours.

0358 GMT (11:58 p.m. EDT Sat.)

The Range reports toxics are now "go" for launch!

0354 GMT (11:54 p.m. EDT Sat.)

The boat has moved out of the restricted launch hazard area. However, the toxics models remain "no go" and the west headed our way from the west is a big worry. Officials are hoping a shift in the wind will clear the toxics problem.

0352 GMT (11:52 p.m. EDT Sat.)

Launch Weather Officer Joel Tumbiolo reports that those anvil clouds are moving toward the Cape from the west as predicted. They could be in the local area and presenting a constraint to launch by the 12:38 a.m. EDT lifotff time.

0350 GMT (11:50 p.m. EDT Sat.)

During this extended hold at the T-minus 4 minute mark, the launch team will have to perform software updates for the Delta 2 rocket. The changes reflect the slightly different trajectory that is used by the day's second launch opportunity.

0344 GMT (11:44 p.m. EDT Sat.)

NEW LAUNCH TIME. The decision has been made to re-target liftoff for 12:37:59 a.m. EDT (0437:59 GMT) due to the Range.

Range Safety has a constraint on toxics. The wind is currently blowing toward the south. The concern is the toxic cloud from a launch explosion could drift over populated areas.

There is also a boat in the restricted waters of the Atlantic Ocean.

So the countdown will remain holding at the T-minus 4 minute mark during this delay.

There are two chances to launch the Mars Opportunity spacecraft each night. The first uses a flight azimuth of 93 degrees; the second uses an azimuth of 99 degrees.

0342 GMT (11:42 p.m. EDT Sat.)

T-minus 4 minutes and holding. The countdown has entered the final planned hold point for tonight's launch attempt. During this 10-minute, 16-second hold, officials will poll the various team members in the soft blockhouse, Range Operations Control Center and Mission Directors Center. If all systems are go, the countdown will resume for liftoff at 11:56:16 p.m. EDT.

However, the Range is currently "red" due to the toxics safety constraint. Officials are hoping shifting winds will resolve the situation. If the Range remains "no go", this hold in the countdown would be extended and liftoff would be re-targeted for tonight's second of two launch times at 12:38 a.m. EDT.

0338 GMT (11:38 p.m. EDT Sat.)

The first stage fuel tank vent is being closed and the tank is being pressurized for launch.

0336 GMT (11:36 p.m. EDT Sat.)

T-minus 10 minutes and counting. The Thick Cloud Rule is now "go" for launch.

However, the Range reports that the toxics predictions are "no go" at this time. Safety personnel run computer models to ensure the toxic cloud from a launch mishap won't endanger anyone based on the wind conditions and other factors at launch time.

0333 GMT (11:33 p.m. EDT Sat.)

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

0326 GMT (11:26 p.m. EDT Sat.)

T-minus 20 minutes and counting. The planned pause in the countdown has been completed. Clocks will now tick down to T-minus 4 minutes where the final hold is scheduled. That hold will last 10 minutes and 16 seconds, leading to tonight's launch time of 11:56:16 p.m. EDT.

0322 GMT (11:22 p.m. EDT Sat.)

The full launch team has been polled. The countdown is set to resume at 11:26 p.m. EDT as planned.

0321 GMT (11:21 p.m. EDT Sat.)

Boeing Mission Director has completed his poll for picking up the countdown. The launch team poll is next.

0319 GMT (11:19 p.m. EDT Sat.)

NASA Launch Manager Omar Baez has just completed a poll of the space agency's management team. No problems were reported.

Meanwhile, the Debris Cloud Rule and the flight through precipitation constraint are now "go" for launch. Only the Thick Cloud Rule remains in violation at this time.

0316 GMT (11:16 p.m. EDT Sat.)

Now half-way through this built-in hold at T-minus 20 minutes. A series of readiness polls of the various teams will be performed upcoming in the next few minutes before the countdown is resumed.

0309 GMT (11:09 p.m. EDT Sat.)

Launch Weather Officer Joel Tumbiolo has just completed a weather briefing. There remains optimism that the showers will be moving out of the vicinity as predicted, allowing for launch at 11:56:16 p.m.

0307 GMT (11:07 p.m. EDT Sat.)

The Anvil Cloud Rule and Disturbed Weather Rule are now "go" for launch.

However, the Debris Cloud Rule, the Thick Cloud Rule and the flight through precipitation weather constraints remain "no go" for launch at this time.

0306 GMT (11:06 p.m. EDT Sat.)

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 date from the just-completed steering tests.

Launch is slated for 11:56:16 p.m. EDT from pad 17B at Cape Canaveral Air Force Station, Florida.

0303 GMT (11:03 p.m. EDT Sat.)

The gimbal checks of the nozzles on the Delta 2 first and second stage engines have been completed.

The countdown is three minutes away from entering the planned hold at T-minus 20 minutes.

0256 GMT (10:56 p.m. EDT Sat.)

Liftoff is now just 60 minutes away. The launch team will soon begin 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.

And in the next few minutes, RF link tests between the Range and rocket are scheduled.

0251 GMT (10:51 p.m. EDT Sat.)

The countdown is progressing smoothly for tonight's 11:56 p.m. EDT launch of the Boeing Delta 2 rocket and NASA's Opportunity rover spacecraft. There are no technical problems being reported by the launch team. The rocket has been fueled up for its late-night blastoff.

The only worry has been -- and continues to be -- the local weather conditions. The system that has brought cloudiness and rain over the pad is moving away. There is hope the conditions will clear, producing a hole for the Delta 2 to shoot through before another weather system from the west arrives over the Cape tonight.

0240 GMT (10:40 p.m. EDT Sat.)

The launch team reports the loading of the Delta 2 rocket's first stage liquid oxygen tank was completed at 10:39 p.m. EDT. The operation took 27 minutes and 26 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 on Thursday; the third stage and nine strap-on booster rockets are solid-propellant.

Meanwhile, the Anvil Cloud Rule, the Debris Cloud Rule, the Disturbed Weather Rule, the Thick Cloud Rule and the flight through precipitation weather constraints remain "no go" for launch at this time. It is hoped the weather system moving through the Cape area will be clear by 11:30 p.m.

0227 GMT (10:27 p.m. EDT Sat.)

Now 15 minutes into the cryogenic tanking operation. Once the liquid oxygen tank reaches the 95 percent full level, the "rapid load" valve will be closed and the slower "fine load" phase will continue to fill the tank.

0222 GMT (10:22 p.m. EDT Sat.)

The bottom of the Boeing Delta 2 rocket is icing over as the super-cold liquid oxygen flows into the first stage. LOX loading has passed the 10-minute mark. No problems have been reported.

0214 GMT (10:14 p.m. EDT Sat.)

Now two minutes into this approximate 25-minute process to fill the first stage liquid oxygen tank. The loading was started at 10:12:15 p.m. A plume of white vapor is now streaming from the vent port of the first stage.

0212 GMT (10:12 p.m. EDT Sat.)

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 11:56:16 p.m. EDT launch attempt. The liquid oxygen is flowing from a storage tank at pad 17B, through plumbing and into the bottom of the rocket. The LOX and the RP-1 kerosene fuel loaded aboard the vehicle in the last half-hour will be consumed by the first stage main engine.

0210 GMT (10:10 p.m. EDT Sat.)

The P-3 tracking aircraft supporting tonight's launch reports it is airborne over the Pacific Ocean. The plane will receive telemetry from the Delta 2 rocket during the later portion of the launch and relay that data back to Cape Canaveral. Data flow tests between the P-3 and the Cape are now underway, NASA says.

0206 GMT (10:06 p.m. EDT Sat.)

The "go" has been given to the launch team to begin preparations for loading the rocket's first stage liquid oxygen tank.

0156 GMT (9:56 p.m. EDT Sat.)

Now two hours away from the targeted liftoff time.

Launch Weather Officer Joel Tumbiolo just gave another briefing to the management team. He says the current area of rain is moving through the area from the southwest and should be 10 miles to the east by 11:30 p.m. EDT, about 25 minutes before liftoff time.

There is another system over the western coast of Florida. The anvil clouds associated with that system could be over the Cape in about three hours.

So the hope is launch can occur during a hole between the two systems. The weather aircraft, to be taking to the skies in about 10 minutes, will be checking the cloud conditions between the two systems.

Tumbiolo believes the first launch opportunity tonight will offer better weather -- at 11:56 p.m. EDT. The second launch time is 12:38 a.m. and could be impacted by those anvil clouds.

0142 GMT (9:42 p.m. EDT Sat.)

The first stage fuel tank of the Boeing Delta 2 rocket has been fully loaded for today's planned 11:56 p.m. EDT liftoff from Cape Canaveral Air Force Station in Florida. The tank was filled with a highly refined kerosene, called RP-1, during a 19-minute, 55-second process that concluded at 9:42 p.m. EST.

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

0136 GMT (9:36 p.m. EDT Sat.)

The launch team has computed that the full load for the first stage fuel tank is 9,997 gallons. Over 7,500 gallons are already aboard.

Once the tank is filled with 9,800 gallons, or 98 percent, the "rapid load" valve will be closed and the slower "fine load" phase will continue top off the tank.

0132 GMT (9:32 p.m. EDT Sat.)

This approximate 20-minute process to load the rocket's first stage with about 10,000 gallons of refined kerosene fuel continues with no problems. Over 5,000 gallons have been loaded to this point.

0127 GMT (9:27 p.m. EDT Sat.)

Now five minutes into the RP-1 loading process. Over 2,000 gallons are aboard the rocket.

Boeing Mission Director Rich Murphy just asked the Air Force weather team about the latest radar loops, which seem to suggest a bit of clearing to the southwest of the Cape. The weather reconnaissance aircraft will be checking out that area a little later. So there is some hope of weather cooperating tonight. The forecast still calls for a 60 percent chance of not meeting the weather rules at launch time.

0122 GMT (9:22 p.m. EDT Sat.)

About 10,000 gallons of a highly refined kerosene propellant, called RP-1, are now being pumped into the base of the rocket from a storage tank at pad 17B. The fuel will be used along with liquid oxygen -- to be loaded into the rocket -- in about an hour by the first stage RS-27A main engine.

Meanwhile, the Anvil Cloud Rule, the Debris Cloud Rule, the Disturbed Weather Rule, the Thick Cloud Rule and the flight through precipitation weather constraints remain "no go" for launch at this time.

0118 GMT (9:18 p.m. EDT Sat.)

The Boeing launch team is currently working through the steps to prepare for loading the Delta 2 rocket's first stage fuel tank. After verifying valves, sensors, flow meters and equipment are ready, the highly refined kerosene fuel will start flowing into the vehicle.

0117 GMT (9:17 p.m. EDT Sat.)

The launch team has been given the "go" to begin fueling the first stage.

0056 GMT (8:56 p.m. EDT Sat.)

T-minus 150 minutes and counting. The Terminal Countdown has begun for the launch of the Boeing Delta 2-Heavy rocket carrying NASA's Mars Exploration Rover-B, also called Opportunity.

Over the next three hours, the launch team will ready the three-stage rocket, payload and ground support systems for the planned 11:56:16 p.m. EDT (0356:16 GMT) blastoff from pad 17B at Cape Canaveral Air Force Station in Florida.

Weather conditions remain very iffy. Meteorologists will continue to monitor the situation, passing updates to managers on the forecast and the likelihood the weather will be acceptable at launch time.

With the countdown underway, the Complex 17 area will be verified cleared of workers as a safety precaution. A warning horn will be sounded at the seaside complex to alert personnel to depart and head back to road blocks.

Upcoming in the next few minutes, launch team members in the Delta Operations Building, or "soft blockhouse", located about eight miles west of the pad will oversee the pressurization of helium and nitrogen storage tanks inside the rocket's first and second stages; and the second stage fuel and oxidizer tanks will be pressurized for launch. In addition, the Delta's onboard guidance computer -- called the Redundant Inertial Flight Control Assembly or RIFCA -- will be turned on and configured for the mission.

The loading of 10,000 gallons of RP-1 fuel into the first stage is scheduled to start about 20 minutes from now.

0047 GMT (8:47 p.m. EDT Sat.)

The launch team has been polled to ensure all the console operators are in position and ready to continue with the countdown this evening. The Terminal Countdown is scheduled to commence in about 9 minutes.

0036 GMT (8:36 p.m. EDT Sat.)

Twenty minutes are remaining in this hold. Polls of the launch team are upcoming before the countdown resumes.

0005 GMT (8:05 p.m. EDT Sat.)

Launch Weather Officer Joel Tumbiolo just give mission managers an updated briefing on the current conditions and the forecast for this evening. He has increased the probability of weather prohibiting launch from 40 up to 60 percent. And that percentage could go even higher as the night progresses.

There are several weather rules are that presently being violated due to the electrically-charged clouds and rain in the area. There is another area of bad weather to the southwest that is moving toward the launch site. Thunderstorm debris clouds, thick clouds and precipitation in the rocket's flight path appear to be the main concerns for this evening's launch attempt.

The weather reconnaissance aircraft should be airborne around 10 p.m. to examine the clouds and conditions aloft.

SATURDAY, JUNE 28, 2003
2356 GMT (7:56 p.m. EDT)

T-minus 150 minutes and holding. Clocks at Cape Canaveral have entered a scheduled 60-minute built-in hold in advance of the Terminal Countdown. Liftoff of the Delta 2 rocket is now exactly four hours away.

The weather continues to look iffy. The field mills are now "go". But all the other constraints that were mentioned in our last update as being violated remain in the same status.

2300 GMT (7:00 p.m. EDT)

A check of the current weather conditions at the launch site indicates that the Anvil Cloud Rule, the Debris Cloud Rule, the Disturbed Weather Rule, the Thick Cloud Rule, the field mill electrical charge measurements and the flight through precipitation constraints are all being violated at this time.

The rules governing lightning, cumulus clouds, smoke plume, launch winds and the cloud ceiling are currently "go".

2135 GMT (5:35 p.m. EDT)

It is raining in the Cape Canaveral area now. Launch Weather Officer Joel Tumbiolo is still calling for a 60 percent chance of favorable conditions for tonight's launch time.

The hope is the weather will improve by later this evening, with just the lingering clouds the concern for violating the launch weather rules.

2000 GMT (4:00 p.m. EDT)

The inaugural Boeing Delta 2-Heavy rocket has been fully revealed for the first time following the rollback of the mobile service tower from around the vehicle.

A large crowd of news media representatives, Mars rover project officials and even Bill Nye "The Science Guy" are here at the pad for today's tower rollback.

The 126-foot tall rocket looks like previous Delta 2 rockets. But upon closer look you will see the nine strap-on solid-fueled boosters mounted to the first stage are a few feet taller and six inches larger in diameter than ever flown on a Delta 2.

These solid motors, called GEM 46s, were developed and flown on Boeing's bigger Delta 3 rocket. But to increase the performance of the Delta 2, Boeing and NASA conceived a plan to use the boosters on the workhorse rocket. Tonight will be the first Delta 2-Heavy mission following several years of preparations.

Six of the motors are ignited at liftoff, combining with the rocket's liquid-fueled first stage main engine, to propel the Delta 2 off the launch pad. The motors fire for about 76 seconds before burning out. The three remaining boosters are ignited in the air as the spent ground-lit boosters are jettisoned to fall into the Atlantic. The air-lit motors burn out and separate about two-and-a-half minutes into launch.

With the tower rolled back, workers will now get the structure secured into its launch location. Also, activities to configure the pad for liftoff will include positioning the special sound suppression equipment, which was built for the Delta 3 and its larger solid motors. The Terminal Countdown remains scheduled to begin at 8:56 p.m. EDT.

1946 GMT (3:46 p.m. EDT)

A major milestone in the countdown to tonight's launch is now underway at pad 17B. The metal cocoon-like mobile service tower enclosing the Boeing Delta 2 rocket is currently driving away from the launcher as the countdown continues for this evening's 11:56 p.m. EDT liftoff.

The tower structure is used to assemble the rocket on the seaside pad and provide weather protection.

1930 GMT (3:30 p.m. EDT)

Good day from Cape Canaveral's Complex 17 were we are awaiting the rollback of the mobile service tower from around the Delta 2 rocket. Crews are working to move the tower into the launch position at pad 17B for this evening's planned liftoff of the Mars Exploration Rover-B "Opportunity" for its journey to the Red Planet.

0500 GMT (1 a.m. EDT)

It is deja vu all over again. Two-and-a-half weeks after the successful departure of the Mars Exploration Rover Spirit, the twin Opportunity spacecraft is sitting atop its rocket launcher at Cape Canaveral for this evening's late-night blastoff.

The launch can occur at two precise instants in time: 11:56:16 p.m. and 12:37:59 a.m. EDT.

This 299th flight of the Delta rocket marks the inaugural voyage for Boeing's Delta 2-Heavy. The version is more powerful than any other Delta 2 configuration because it uses the larger solid-propellant strap-on rocket motors developed for the Delta 3 rocket.

The Delta 2-Heavy is needed to launch the Opportunity rover since the liftoff comes after the optimum portion of the planetary alignment window between Earth and Mars that occurs every 26 months. The Spirit rover was carried aloft June 10 by the standard Delta 2-7925 configuration launcher.

"It is purely an energy thing," MER project manager Peter Theisinger said. "We are out of the sweet spot, low-energy part of the transfer trajectory. So we need the Delta 2-Heavy to launch the exact same payload mass to Mars in late-June through mid-July."

The Opportunity's launch window extends to July 15.

This is the first of three Delta 2-Heavy rockets NASA will use over the next year. The Space Infrared Telescope Facility will use the launcher variant in August, followed by the MESSENGER probe to planet Mercury next March.

Opportunity will be deployed from the third stage of the Delta 2 over the Pacific Ocean, off the west coast of North America, about 80 minutes after liftoff. It is due to arrive at Mars on January 25, landing in the Meridiani Planum region that is believed to have a high concentration of iron oxide, or gray hematite.

"Hematite forms in a number of different ways on Earth but most of them involve the action of liquid water," explained Steve Squyres, principal investigator for the Mars Exploration Rovers project. "So you can think of the hematite mineral signatures being kind of a beacon that's saying to us, 'hey, water may have been here.' Now we don't know how it formed, it could have been a hydrothermal system, could have been a lake, we're not sure. But it says, mineralogically, water."

The twin Mars rovers are searching for clues that the Red Planet had a watery past and could have been habitable.

"If you're really looking for life, it's not just having water, but it's the perseverance of water that counts. And that's what these missions do uniquely, they're really going to tell us about the perseverance of water on Mars, whether it was there for a few minutes, a few hours, millions of years," said Ed Weiler, NASA's associate administrator for space science.

"If we have any hope of finding an answer to the question is there life on Mars, was there life on Mars, we have to show that water not only exists on Mars but persevered for long, long periods of time."

Watch this page for comprehensive live coverage throughout Saturday's countdown and launch of the Delta 2 rocket and Opportunity rover!

FRIDAY, JUNE 27, 2003
1800 GMT (2 p.m. EDT)

The Launch Readiness Review was successfully completed this morning with no significant issues to report. Liftoff of the Boeing Delta 2 rocket carrying the Mars Exploration Rover-B, also called Opportunity, remains scheduled for 11:56:16 p.m. EDT Saturday night. A backup launch time is available a short time later at 12:37:59 a.m. EDT.

The rocket's second stage has been loaded with its storable propellants at pad 17A. Work underway today includes beacon checks and ordnance operations.

Launch day activities will begin around 11 a.m. Saturday as workers put the final touches on the MER-B rover spacecraft at the pad. The mobile service tower enclosing the rocket is expected to roll away from the vehicle for launch around 3:30 p.m. If there is bad weather in the area, officials could delay the tower removal by about two hours without impacting the launch attempt, NASA Launch Manager Omar Baez said.

The Terminal Countdown should commence at 8:56 p.m. from the T-minus 150 minute mark.

The loading of RP-1 fuel into the first stage should start at 9:16 p.m. That will be followed by the pumping of super-cold liquid oxygen into the first stage around 10:15 p.m. EDT.

Two planned holds -- T-minus 20 minutes and T-minus 4 minutes -- will lead to the instantaneous liftoff time at the end of the three-hour countdown sequence.

We will post live updates throughout the day on this page starting with confirmation of tower rollback.

1400 GMT (10 a.m. EDT)

The latest launch weather forecast is available here.

THURSDAY, JUNE 26, 2003

The "Opportunity" Mars rover is slated for launch Saturday night from Cape Canaveral aboard the first flight of Boeing's Delta 2-Heavy rocket. Liftoff will occur at precisely 11:56:16 p.m. EDT (0356:16 GMT Sunday).

The weather forecast calls for a 40 percent chance of unacceptable conditions.

The Launch Readiness Review is planned for Friday. The pre-launch news conference will follow at 1 p.m. EDT.

Watch this page for live coverage through the final hours of the countdown and launch!

WEDNESDAY, JUNE 25, 2003

Here is the latest MER-B mission status report from NASA:

The Flight Readiness Review was held on June 21, and afterward, a decision was made to postpone the launch by at least a couple of days. Based on routine post-test inspections, the launch team elected to remove and replace a band of protective cork insulation on the Delta first stage that may not have been adhering properly. The location is below the forward attach points of the strap-on solid rocket boosters. Inspections of a second band located higher on the first stage showed that only minor work is necessary to assure that it is ready for launch.

All of the reapplication and repair of the cork insulation will be completed today. Normal countdown activities will then resume on Thursday, beginning with the fueling of the Delta second stage with its complement of storable hypergolic propellants. A countdown dress rehearsal will also be held on Thursday. The Launch Readiness Review will be held on Friday in the Mission Briefing Room at KSC.

The fairing was installed around the MER-B "Opportunity" spacecraft on June 21. Fairing closeouts will begin tonight. Integrated spacecraft/launch vehicle testing indicates that the flight systems are ready for launch.

At Pad 17B on launch day, the mobile service tower will be retracted from around the Delta 2 about 3:30 p.m. if weather permits. Options are available to retract the mobile service tower later if there are thunderstorms in the vicinity and still reach one or both of the two available launch times.

Loading of the RP-1 fuel aboard the Delta first stage is nominally planned to begin at 9:16 p.m. followed by loading of liquid oxygen at about 10:06 p.m.

SATURDAY, JUNE 21, 2003

DELAY. Officials have delayed the launch of NASA's Mars Exploration Rover "Opportunity" so workers can replace insulation of the Boeing Delta 2 rocket that will propel the spacecraft to the Red Planet.

The launch from pad 17B at Cape Canaveral has been scheduled for early Thursday, June 26. But the unplanned job of removing and replacing a band of protective cork insulation on the rocket's first stage will delay the liftoff until Saturday evening, June 28.

The available launch times are 11:56:16 p.m. EDT and 12:37:59 a.m. EDT (0356:16 and 0437:59 GMT on the 29th).

"The Flight Readiness Review was held today for the MER-B launch of the "Opportunity" Mars Exploration Rover. Afterward, a decision was made to postpone the launch by at least a couple of days," NASA said in a statement.

"Based on routine post-test inspections, the launch team has elected to remove and replace a band of protective cork insulation on the Delta first stage. The location is below the forward attach points of the strap-on solid rocket boosters. Inspections of a second band located higher on the first stage are being performed.

"The time necessary to do this work means a rescheduling of the launch to no earlier than Saturday, June 28 at 11:56:16 p.m. EDT. A firm date will be established on Monday after the engineering team reconvenes."

MONDAY, JUNE 16, 2003

Launch of NASA's Mars Exploration Rover Opportunity has been put off one day -- to June 26 -- to give workers more time to complete pre-flight preparations, the space agency said Monday.

Liftoff aboard the debut Boeing Delta 2-Heavy rocket from pad 17B at Cape Canaveral Air Force Station in Florida is targeted for 12:27:31 a.m. EDT (0427:31 GMT). A backup launch time is available at 1:08:45 a.m. EDT (0508:45 GMT).

The slip was expected. NASA managers said immediately following the successful launch of the Spirit rover on June 10 that schedules leading to the June 25 launch date for Opportunity were extremely tight. Delays in launching Spirit and bad weather at the Cape combined to slow preps for the second rover mission.

Earth and Mars are aligned to permit Opportunity to launch between June 25 and July 15 aboard the Delta 2-Heavy. The rocket uses larger strap-on solid boosters, providing additional power to propel the rover to the Red Planet after the more optimal launch window, which was used by Spirit.

Opportunity will be moved to the launch pad early Tuesday for mating to the Delta 2.

Over the weekend, the simulated flight test of the launcher was completed at pad 17B. The test activates the Delta's mechanical and electrical systems during a mock launch of the rocket.

TUESDAY, JUNE 10, 2003

NASA kicked off an $800 million mission to Mars today, launching the first of two golf cart-sized robots that will creep across the red planet's surface looking for the geological traces of a warmer, wetter past and the environmental conditions necessary for the evolution of life. Read our full launch story.

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   VIDEO: POST-LAUNCH NEWS CONFERENCE QT
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Snapshots

The Delta 2-Heavy rocket is unveiled Saturday afternoon during retraction of the mobile service tower. Photo: Steven Young/Spaceflight Now