Capping off nearly two months of frenzied activity at SpaceX's California headquarters, the company's beleaguered Falcon 1 rocket stands ready for a fourth shot at success, officials announced Saturday.

Everything is on schedule for launch between 7 p.m. and midnight EDT Sunday night, according to an update posted on the company's Web site.

The Falcon 1 rocket to fly Sunday evening is seen in this August photo as technicians prepared the vehicle at the SpaceX factory. Credit: Chris Miller/Spaceflight Now SEE MORE PANORAMAS HERE

The 70-foot-tall black-and-white booster will blast off from SpaceX's launch facility on Omelek Island, a seven-acre stretch of land at the U.S. Army's Reagan Test Site at Kwajalein Atoll in the Marshall Islands.

The two-stage rocket and its dummy payload will turn east from Kwajalein and reach orbit about nine-and-a-half minutes after launch. See a detailed launch timeline here.

The launch window opening equates to 11 a.m. local time Monday at the central Pacific site.

SpaceX has four days to get the Falcon 1 off the ground or else wait until the end of October. An air-launched Pegasus rocket has range tracking and communications facilities booked for an Oct. 19 mission.

The announcement came after more than eight weeks of work to overcome the failed launch of the last Falcon 1 booster on Aug. 2.

Elon Musk, founder, CEO and chief technical officer of Space Exploration Technologies Corp., ordered a new rocket to be ready within weeks after the company's third failure in as many tries.

Earlier launches in 2006 and 2007 also fell short of orbit, delaying Musk's dream of revolutionizing space travel through lower costs and easier access to space. The Falcon 1, priced at $7.9 million per launch, was privately developed by a team of engineers bankrolled by Musk's independent fortune.

Engineers quickly traced the August failure to a collision between the rocket's first and second stages as the two bodies separated about two-and-a-half minutes after liftoff.

The root cause of the crash was unexpected residual thrust emanating from the first stage Merlin engine after shutdown. On-board timers triggered stage separation one-and-a-half seconds after the engine cutoff command, but the Merlin was still producing about one percent of its total thrust.

The thrust propelled the spent first stage into the base of the second stage, dooming the mission.

The problem did not occur on earlier Falcon missions because the August launch included an upgraded Merlin 1C engine with a regenerative cooling system. The new engine takes longer to shut down than expected.

SpaceX changed the timer setting to five seconds for this mission, allowing enough time for the Merlin to shut down and reach zero thrust before stage separation.

Hardware for Sunday's mission, called Flight 4 in the SpaceX naming system, was already under construction when Flight 3 launched in August.

Engineers later shipped the rocket for pressure and structural integrity checks at the company's test facility in McGregor, Texas. The vehicle was transported back to SpaceX headquarters in Hawthorne, Calif., for final preparations, painting and engine work.

Officials said the rocket completed testing in Texas within 24 hours.

Tim Buzza, SpaceX's vice president of launch operations, said the rocket for Flight 4 will be identical to the booster lost during Flight 3. The launch trajectory will also mimic the design of the doomed August flight.

"This is the first time we've duplicated a mission like this," Buzza said. "We just changed that one little timer setting."

The quick turnaround precluded any significant changes, and engineers are eager to compare data from the two flights.

"We're really back to the fundamentals of what test flights are all about," Buzza said. "You tweak little things here and there, then go off and try again."

SpaceX previously upgraded software and engine components between flights.

Flight 4 had been slated to launch a small Malaysian satellite called RazakSat, but Musk pulled the payload from the upcoming mission. The decision made good on a commitment to complete a successful Falcon 1 flight before launching RazakSat, Musk said.

SpaceX instead hastily developed a 364-pound aluminum dummy to take the place of RazakSat. The six-sided mass simulator, fabricated by SpaceX specifically for this mission, stands about five feet tall and will remain attached to the Falcon 1's second stage after reaching orbit.

The Falcon 1 stages were loaded aboard the cargo hold of an Air Force C-17 Globemaster for a chartered flight from Los Angeles Sept. 3. The hardware arrived at Kwajalein the next day, according to SpaceX.

SpaceX previously used a regularly-scheduled cargo freighter to deliver rocket parts from California to Kwajalein. The 6,000-mile trip took more than a week, and Buzza said the launch would probably be pushed well into October if the company used the ship to transport Flight 4 equipment.

Engineers connected the rocket stages and attached the payload fairing inside the Falcon 1 assembly hangar at Omelek. The rocket was hoisted vertically on the pad about two weeks after the hardware arrived at the launch site.

SpaceX completed a static ignition test of the first stage's Merlin 1C engine Sept. 20.

Technicians spent the past week replacing and testing a component in the liquid oxygen supply line of the second stage Kestrel engine.

Less than 25 people, including managers, engineers and technicians, support normal Falcon 1 launch operations at Kwajalein.

Kwajalein Atoll is located 2,500 miles southwest of Hawaii in the Marshall Islands. The U.S. Army leases a portion of the island chain as part of the military's Reagan Test Site.

"There's no question that Kwajalein throws us some logistics challenges," Buzza said.

Shipping needed parts and rocket components to Kwajalein on short notice usually depends on finding extra room on cargo flights to the remote outpost, according to Buzza.

SpaceX chose to launch the Falcon 1 from Kwajalein after the Air Force said the company's original pad at Vandenberg Air Force Base, Calif., interfered with Atlas 5 rocket operations nearby.

The 2005 decision to move to Kwajalein added more complexities to rocket processing but opened up more payload opportunities for the light launcher, Buzza said.

With open ocean for thousands of miles in nearly every direction, Omelek Island offers launch trajectories to both polar and equatorial orbits.

The company's Falcon 9 rocket, a heavy-lifting scaled-up version of the Falcon 1, will begin flights from Cape Canaveral's Space Launch Complex 40 sometime early next year.

Discussions may soon be underway with Air Force officials for SpaceX to use Space Launch Complex 4 for Falcon 9 polar orbit launches from Vandenberg, Buzza said. The hillside pad was formerly used to launch Titan rockets from the West Coast.

The combination of East Coast and West Coast pads would allow SpaceX to fully compete for military launches with Atlas and Delta rockets offered by United Launch Alliance.

But SpaceX must first master launches of the smaller Falcon 1. Musk said last month he wants at least one successful Falcon 1 launch under his belt before attempting a Falcon 9 launch.

"Better to have learned this lesson now than to learn it at 10 times greater scale," Musk said after the August failure.

Production of Flight 5 hardware is already underway in Hawthorne. Both stages of the fifth Falcon 1 are mostly fabricated and will be ready for launch by January. Full-scale Flight 6 production will begin in the next few months, according to Musk.