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French military satellite primed for morning launch

Posted: December 9, 2009

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An Ariane 5 rocket is being readied to haul a French reconnaissance satellite to orbit Wednesday in a rare morning launch from the Guiana Space Center in South America.

Artist's concept of the Helios 2B spacecraft. Credit: CNES
The Helios 2B satellite will join an orbiting fleet of military platforms with optical and infrared imagers to map battlefields, monitor terrorist threats and enforce disarmament and non-proliferation treaties.

"Images shouted by the satellites provide necessary intelligence data to the French senior authorities and also to the forces deployed on the ground," the French defense ministry's Helios press kit said.

Officials said French military action in Kosovo, Lebanon, Afghanistan, Chad and Darfur demonstrated the Helios system's value.

The 9,259-pound Helios 2B spacecraft will join two other Helios satellites already in space. Helios 1A was launched in 1995 and Helios 2A arrived in orbit in 2004.

Six European countries, including France, will be users of Helios 2B data.

The satellite is due for liftoff at 1626 GMT (11:26 a.m. EST) Wednesday from the ELA-3 launch pad at the European spaceport in Kourou, French Guiana. The 151-foot-tall rocket must blast off in an instantaneous launch window, or else wait until another day.

The Ariane 5 launcher rolled from its final assembly building to the launch zone Tuesday morning. Workers made electrical, fluid and communications connections between the rocket and ground systems later on Tuesday.

The rocket will be flying in the Ariane 5 GS configuration with Vulcain 1 engine, upgraded solid rocket boosters and an upper stage fueled by storable hydrazine and nitrogen tetroxide propellants.

The launch team will begin assembling early Wednesday morning, beginning the launch countdown at 0456 GMT (11:56 p.m. EST). Engineers will check electrical systems at 0856 GMT (3:56 a.m. EST) and begin fueling the first stage with liquid hydrogen and liquid oxygen at 1136 GMT (6:36 a.m. EST).

The Ariane 5 rolls to the launch pad Tuesday morning. Credit: Arianespace
The first stage's Vulcain main engine will be chilled down at 1306 GMT (8:06 a.m. EST). The launch team will verify good communications with the rocket through telemetry, tracking and command systems at 1516 GMT (10:16 a.m. EST).

Seven minutes before launch, computers will take control of the countdown in a synchronized sequence of events to pressurize propellant tanks, switch to on-board power and take the rocket's guidance system to flight mode.

The Vulcain engine will ignite as the countdown clock reaches zero, followed by a health check and ignition of the Ariane 5's solid rocket boosters seven seconds later to send the nearly 1.7 million-pound launcher skyward.

Rolling onto a northerly trajectory from the launch site, the Ariane 5 will burst through the speed of sound in less than a minute and empty its solid-fueled boosters 2 minutes, 20 seconds after liftoff.

The conical payload shroud will jettison three minutes into the flight after the rocket passes through the atmosphere. The Vulcain engine will fire until 9 minutes, 36 seconds after launch, when it will shut down and the first stage will separate nearly 250 miles over the Atlantic Ocean.

The storable propellant upper stage's Aestus engine will next light for a lengthy burn lasting more than 16 minutes.

At the time of second stage shutdown, Helios 2B and its upper stage should be in a sun-synchronous orbit at an altitude of about 423 miles over the Arctic Ocean.

The rocket and payload will coast halfway around the world before Helios 2B is deployed in communications range of a ground station in Perth, Australia. Spacecraft separation is targeted for 59 minutes, 23 seconds after liftoff.

Wednesday's mission will be the seventh flight of an Ariane 5 rocket this year on commercial, scientific and military launches. It will also be the 193rd launch of an Ariane rocket since the family's debut in 1979. The Ariane 5 launcher will have conducted 49 of those missions after Wednesday's flight.