A commercial satellite to distribute television programs to Europe and a German military communications bird are shrouded inside an Ariane 5 rocket scheduled to lift off Friday evening on its 50th flight.

File photo of the Ariane 5 rocket rolling to the launch pad. Credit: Arianespace

The 166-foot-tall rocket can launch during a 49-minute window opening at 2159 GMT (5:59 p.m. EDT) Friday. The Ariane 5 will blast off from the French-run spaceport in Kourou, French Guiana.

The rocket rolled atop a mobile launch table to the ELA-3 pad Thursday morning. The trip on dual rail tracks took nearly two hours, according to Arianespace, the rocket's commercial operator.

Once on the launch pad, the Ariane 5 was hooked up to the complex's electrical, fluid and communications systems for its one-day stay.

The launch was postponed two weeks because of a problem with a rocket subsystem. Engineers resolved the issue and cleared the Ariane 5 for flight earlier this week.

The mission will be the 50th launch of the Ariane 5 rocket since its disastrous debut flight in 1996, which was ended by an infamous computer glitch causing the vehicle to spin out of control 30 seconds after liftoff.

The Ariane 5 rocket overcame its dark beginnings and has amassed 35 straight successful launches since 2003. The European rocket now leads the cutthroat commercial launch industry.

Friday's launch is typical of Ariane 5 missions today. Powered into space by the combined force of hydrogen and solid rocket propulsion, the Ariane 5 ECA launcher will drop off two communications satellites in a preliminary transfer orbit. From there, the spacecraft will push themselves to their permanent stations in the geosynchronous arc 22,300 miles above the planet.

It will take more than 33 minutes for the Ariane 5 to deploy its payloads in an elliptical orbit that will take the satellites as far as 22,236 miles from Earth. The orbit should have an inclination angle of 3 degrees to the equator, according to Arianespace, which has managed the Ariane 5 rocket's commercial operations since 1999.

After providing the bulk of the thrust needed to propel that Ariane 5 into the upper atmosphere, the launcher's two cylindrical solid rocket boosters will be released at T+2 minutes, 20 seconds.

The hydrogen-fueled Vulcain 2 main engine of the first stage will give way to a cryogenic upper stage just after the 9-minute point in the flight. The Ariane 5's second stage will fire for nearly 16 minutes before shutting down at T+24 minutes, 45 seconds.

Workers add a special logo to the Ariane 5 rocket commemorating its 50th launch. Credit: Arianespace

ASTRA 3B will separate from the Ariane 5 first at T+Plus 27 minutes, 40 seconds, according to Arianespace data. A barrel-shaped satellite adapter will be jettisoned three-and-a-half minutes later, exposing the COMSATBw 2 spacecraft for deployment at T+33 minutes, 21 seconds.

After arriving in geosynchronous orbit, ASTRA 3B will be positioned at 23.5 degrees east longitude to replace two aging satellites covering communications users across Europe and the Middle East.

Operated by SES ASTRA, the 12,063-pound satellite will broadcast television services directly to homes in Europe and provide two-way broadband communications for Middle East customers. ASTRA 3B's service life is projected to be at least 15 years.

COMSATBw 2 will join a nearly identical satellite launched in October to serve Germany's military with secure communications. The sister satellites will ensure the German Armed Forces receives reliable voice and data relay, video and multimedia broadcasting services for the next 15 years.

Germany's new satellite constellation will reach from the Americas to the Far East. COMSATBw 2 will focus its coverage on Europe and Africa.

Controllers at the Guiana Space Center will begin the Ariane 5's final countdown at 1033 GMT (6:33 a.m. EDT) Friday. Four hours later, at 1433 GMT (10:33 a.m. EDT), engineers will check the rocket's electrical systems. The first stage liquid oxygen and liquid hydrogen propellant loading sequence should begin just after 1700 GMT (1 p.m. EDT). Fueling of the second stage is expected about an hour later.

A final test of telemetry, tracking and command connections between the launcher and ground systems is scheduled for around 2053 GMT (4:53 p.m. EDT).

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 2 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 1.7 million-pound launcher skyward.