It is a rocket launch like no other.

On the launch pad three times in the past three years, getting as close as 30 seconds from liftoff in early 2001, a $450 million military weather satellite mission could finally fly this week from California.

The Defense Meteorological Satellite Program F16 spacecraft is scheduled for blastoff Wednesday atop a refurbished Titan 2 ICBM missile from Vandenberg Air Force Base. The daily 10-minute launch window extends from 9:17 to 9:27 a.m. local time (1617-1627 GMT; 12:17-12:27 p.m. EDT).

The Lockheed Martin-built spacecraft will be placed into a 458-nautical mile orbit around Earth's poles to track global weather conditions for the U.S. military.

The first shot at launching the satellite occurred on Bill Clinton's last day as president of the United States. But an epic saga has played out in the following 33 months as the mission encountered a nearly unbelievable chain of postponement after postponement. Technicians have fixed numerous problems that, if left undiscovered, could have doomed the mission.

"Clearly nobody wanted to have issues that we couldn't fix on the ground and launch a satellite that may not have met its mission need," Col. Randy Odle, DMSP system program director at Los Angeles Air Force Base, said in a recent interview. "We had to deal with those kinds of issues a number of times. Then we had to deal with issues of how do we compete with other launches going on and how do you compete with the Range priority. It has been frustrating in some ways but it's been exciting."

The satellite has gone to the launch pad three times in its life, the first in December 2000 for a planned liftoff in January 2001. After resolving a handful of minor hardware issues, launch was set for January 20.

The DMSP satellite failed to make it off the ground that day when the countdown was halted at T-minus 3 minutes due to a ground support equipment glitch. Liftoff was rescheduled for the following morning.

The second countdown halted at T-minus 28 seconds when computers detected one of the rocket's fuel valves had not opened as planned. In the end, the valve worked just fine but a sluggish indicator switch didn't register the opening fast enough for the computers' liking.

Faced with just a 10-minute window to launch the Titan 2, officials tried to reset liftoff for the end of the period but simply ran out of time.

That afternoon, as workers were preparing to roll the protective mobile service tower back around the Titan 2, faint traces of hydrazine rocket fuel were detected in the air at the Space Launch Complex-4 West launch pad. The time needed to clean up the minor leak prompted officials to cancel plans to launch the next morning.

But later that night, ground controllers watched as the DMSP's Inertial Measurement Unit -- the craft's navigation brain -- began acting erratically. First, the gyroscopes within the IMU suddenly dropped out of flight mode. That incident was followed 20 minutes later by the AC and DC power supplies switching from primary to backup systems on their own.

"If those anomalies occurred during the ascent phase of the launch, the likelihood is we would have lost the satellite and the mission," Odle said at the time.

Without the IMU working properly, the spacecraft would have been unable to navigate itself during the climb to orbit. Most troublesome would have been the portion of launch when a kick motor attached the satellite fires to propel the craft the rest of the way to space after separating from the Titan 2 booster while on a sub-orbital trajectory.

Without the IMU functioning up to par, the satellite wouldn't have been able to point itself correctly, likely resulting in the craft failing to reach orbit and instead reentering the atmosphere.

Over the next month, the satellite's hydrazine thruster fuel was drained and the craft was detached from the Titan 2. After being hauled off the launch pad and returned to the processing building at Vandenberg, technicians determined that a cable on the satellite had broken due to of poor workmanship during assembly, causing the IMU trouble.

Rescheduled for launch in November 2001, another postponement was ordered to replace leaky engine turbopump seals on the Titan 2's first stage. Officials said the rocket's extended wait on the pad -- it was assembled on the seaside complex in October 2000 -- caused the seals to leak.

The satellite headed back to the launch pad at the end of 2001, and the Air Force targeted February 1, 2002 to get the mission airborne. But in mid-January as workers prepared to re-load the hydrazine fuel into the satellite at the launch pad, one of the craft's thrusters failed a vacuum leak check.

The satellite features four of these thrusters, each delivering 100 pounds of thrust. They are crucial during the launch, providing the boost to separate from the Titan 2 rocket and then to keep the satellite on course when its kick motor is firing to achieve orbit.

"These are very critical to us in our ascent phase and clearly if we had a thruster malfunction that would be a serious problem for us. Obviously when we convinced ourselves that Thruster Four was not working properly we had to do something to fix that before we launched," Odle said in an interview at the time.

The satellite was removed from the launch pad a second time and transported back to its hangar. The craft's propulsion system was replaced after engineers discovered that carbazic acid residue, a by-product of hydrazine and air interaction, had contaminated the satellite's thrusters.

"Apparently, air was introduced into the thrusters/propulsion system during testing and interacted with residual hydrazine remaining from the hydrazine defueling accomplished after the January '01 launch abort," Odle said.

"The contamination found in the two thrusters also implicated the remaining two thrusters and the entire propulsion system. As such, we decided to replace the hydrazine-contaminated F16 propulsion system with one from another DMSP spacecraft."

The two-stage Titan 2 was also disassembled from the launch pad during this postponement, freeing up SLC-4W so another rocket could lift off carrying a civilian weather satellite for NASA and NOAA. That launch successfully occurred on June 24, 2002.

The DMSP's rocket was restacked on the pad in July to support launch on October 6, 2002. But concerns were raised with soldering joints in the circuitry for one of the satellite's weather instruments -- the Special Sensor Microwave Imager/Sounder (SSMIS).

Bad solder joints were found on the instrument for DMSP F17 and others in the factory. However, the instrument installed on the DMSP F16 never experienced a problem. In the end, officials said the lack of confidence that the sensor would operate for two-to-three years in space forced F16 to be grounded so its SSMIS could be replaced with a repaired one.

Faced with another extended delay to fix the instrument, the Air Force decided to again destack the Titan 2 rocket to clear the pad for the Coriolis ocean-wind research satellite launch. Coriolis successfully flew in January 2003.

The DMSP satellite returned to the pad in August 2003 for a mid-September liftoff. A summer launch attempt was passed up while engineers reviewed a possible concern with a gyroscope on the Titan 2. That was put to rest, but it bumped the DMSP mission until after the launch of a Titan 4 rocket from Cape Canaveral, Florida.

With a few weeks of separation needed between Titan rocket launches, and troubles that delayed the Titan 4 liftoff from mid-August into September, DMSP was re-targeted for liftoff in October.

Now, DMSP's day to fly is finally near.

"I am cautiously optimistic, but clearly as we approach launch again it is hard not to be excited about this and clearly our team is anxious to see a good mission, a good launch, a good early-orbit checkout," Odle said in an interview last week. "We are excited to be at this point in the launch flow."

But given the history of this mission, one can't help but wonder if another problem could arise.

"You get a little bit paranoid when you have done this a couple times already," Odle said.

Nonetheless, deploying a healthy satellite into space to serve U.S. military forces around the world will help erase the 33 months of frustration.

"Fate sometimes works in interesting ways. Because of all the issues that had to deal with the last two-and-a-half, three years, we now have F16 in probably best condition it ever has been in," Odle said.

"Clearly mission success has been the foremost in everybody's mind...We have never veered from that mission success focus and we expect to see that pay off (Wednesday)."