Arianespace's Ariane 5 rocket will deliver two communications satellites into geostationary orbit, one for Arabsat and a second for SES North America.
This launch will mark the sixtieth Ariane 5 launch, and the fifth and last of 2011.
The heavy lifter is riding on a string on forty-five consecutive successful launches and Arianespace's Chariman and CEO Jean-Yves Le Gall commented days ago on an August 31 decision to delay this flight three days to make additional inspections on the rocket's upper stage engine.
"We do not tolerate any defect on our launchers," Le Gall said. "There was no hesitation on our part in delaying this upcoming flight to ensure the highest level of quality for a successful mission.”
Arianespace expressed concern "by (recent) mission failures of other vehicles" in the launch community.
Russia's Soyuz U rocket was lost en route to delivering cargo to the space station in August, and the country lost contact with their Proton-M upper stage and it's payload during a launch a week earlier.
Even China suffered a setback on August 18 as it's Long March 2C was lost due to an issue with it's second stage engine as it carried a satellite toward orbit.
The Ariane launch team will begin loading the liquid oxygen and liquid hydrogen fuels into the main stage for use by it's core engine at 12:48 p.m. EDT, on launch day.
Launch of Ariane 5 is set for Tuesday at 5:38:07 p.m. EDT (9:38 p.m. GMT) -- the opening of an eighty-four minute launch window -- from launch complex ELA-3 at Kourou, French Guiana.
Twin solid rocket boosters will ignite lift-off combined with a Vulcain 2 core liquid fueled main engine to send the white rocket eastward out over the central Atlantic waters.
As the 165-foot tall Ariane travels higher and faster, the boosters will exhaust it's propellant a little over two minutes after launch and separate as the rocket soars 43 miles high.
Meanwhile, the main engine burns for nine minutes.
One critical milestone will happen three minutes into the launch phase as the rocket's protective payload fairing is jettisoned as it moves into the upper atmosphere.
Just over nine minutes after launch, the engine will shutdown at an altitude of 116 miles, and the first stage will then separate seconds later. The second stage's HM-7B engine will then fire up for the next few minutes.
The first payload to be deployed will be that of Arabsat 5C which will ride to orbit on the top of the two satellite stack.
Built by Thales Alenia Space and Europe’s EADS Astrium, the Arabsat 5C will be used for both private and government communications using both Ka-Band and C-band range.
Thales Alenia Space designed and constructed nearly fifty percent of the International Space Station's living area for the crew; and, the European Automated Transfer Vehicles which delivered supplies to the outpost from Kourou.
The satellite is intended to operate for nearly 15 years from a position of 20 degrees East providing communications from north Africa and the Middle East region.
Arabsat 5C will separate from the upper stage at 6:05 pm, based on an on time launch, from an altitude of 605 miles.
Ariane's second payload, the Orbital Sciences built SES-2 will support both high definition television and communications for North America and the Caribbean over a planned 15 years.
SES-2 will separate and fly free at 6:14 p.m. from an altitude of 1,725 miles.
Once on orbit 22,300 miles above a position at 82 degrees East over the equator, the nearly 78-foot long satellite will undergo a few weeks of testing before becoming operational.
Once Ariane has successfully completed it's mission, Arianespace will begin preparing for the inaugural launch of a Soyuz rocket from Kourou.
The Soyuz launch complex is located seven miles northwest of the Ariane complex, and is mostly based on the configuration of Russia's Soyuz launch pad in Kazakhstan.
The first launch of the Soyuz 2 is planned for just after sunrise on October 20, with a pair of European Galileo navigation satellites.
Arianespace then hopes to get a second Soyuz off the ground before 2011 concludes.
(Charles Atkeison reports on aerospace, science & technology. Follow his updates via Twitter @AbsolutSpaceGuy.)