A Proton rocket lifted off from Kazakhstan on Sunday, launching a powerful satellite to kick off a $1.6 billion next-generation fleet for Inmarsat, the London-based operator specializing in the booming mobile communications market.

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International Launch Services confirms the completion of the Breeze M's third burn, a successful jettison of the stage's auxiliary propellant tank, and a good fourth firing of the upper stage.

The Breeze M and Inmarsat 5 F1 should now be in a transfer orbit with a low point of 295 miles, a high point of 40,416 miles, and an inclination of 50.5 degrees.

The upper stage will coast for nearly 6 more hours before igniting a fifth and final time to inject Inmarsat 5 F1 into a "supersynchronous" transfer orbit.

Separation of the 6.7-ton Inmarsat 5 F1 satellite is scheduled for 0343 GMT (10:43 p.m. EST).

The Breeze M upper stage has finished the second of five burns planned for today's mission, ILS says. The more than 19-minute burn was supposed to place the stage and Inmarsat 5 F1 in an intermediate orbit with a low point of 183 miles, a high point of 3,728 miles and an inclination of 51 degrees.

After a two-hour coast, the Breeze M was supposed to ignite its main engine again at about 1635 GMT (11:35 a.m. EST) for two back-to-back burns separated by a brief intermission to jettison the stage's auxiliary propellant tank.

ILS says these maneuvers will occur when the Breeze M is out of communications with ground stations, so confirmation of their completion will come when antennas re-acquire signals from the rocket shortly after 2200 GMT (5 p.m. EST).

T+plus 19 minutes. International Launch Services confirms the Breeze M upper stage has completed the first of five burns in this mission. The first burn was designed to accelerate the rocket and payload from a suborbital trajectory into a low-altitude parking orbit.

The Breeze M is now in a coast phase until ignition of the second upper stage burn at about 1402 GMT (9:02 a.m. EST).

T+plus 15 minutes. International Launch Services confirms the first ignition of the Breeze M upper stage has occurred to place the Inmarsat 5 F1 satellite into a preliminary parking orbit about 100 miles above Earth.

T+plus 12 minutes. Officials confirm successful shutdown of the Proton's third stage and separation of the Breeze M upper stage, which should be firing now for the first of five burns. But ILS has not been able to confirm the successful ignition yet.

This first burn should last about four-and-a-half minutes, placing the Breeze M and Inmarsat 5 F1 in a circular parking orbit 107 miles high with an inclination of 51.5 degrees.

T+plus 7 minutes. Proton's second stage has been confirmed to have separated, and the third stage RD-0213 engine has begun its burn, producing 131,000 pounds of thrust. The rocket's payload fairing has also been released now that the launcher is in the upper atmosphere.

T+plus 3 minutes, 30 seconds. The second stage's RD-0211 main engine and RD-0210 vernier engines continue firing at full power of 540,000 pounds of thrust.

T+plus 2 minutes, 50 seconds. The Proton's first stage has shut down and jettisoned, and the second stage engines are firing with a half-million pounds of thrust.

T+plus 70 seconds. The Proton rocket has passed the speed of sound and the phase of maximum aerodynamic pressure as it heads northeast from Baikonur.

Liftoff of the Proton rocket with Inmarsat 5 F1, a 6.7-ton satellite to transmit broadband communications services for Inmarsat's new Global Xpress service.

T-minus 60 seconds minutes. The ignition sequence for the six first stage RD-276 engines begins at T-minus 2.5 seconds, reaching a 40 percent thrust level at T-minus 1.75 seconds and 100 percent thrust at T-minus 0.9 seconds.

T-minus 2 minutes. The countdown is being run by a master computer sequencer.

Weather at the launch site is favorable, but the Baikonur Cosmodrome is blanketed in clouds and fog with a temperature of 28 degrees Fahrenheit.

Inmarsat 5 F1 will become the first member of Inmarsat's next-generation Global Xpress fleet. It will be positioned at 63 degrees east longitude for a 15-year mission.

T-minus 8 minutes. The readiness of the Proton core vehicle, the Breeze M upper stage and Inmarsat 5 F1 will be verified over the next few minutes.

T-minus 10 minutes. The Proton launcher on the pad weighs about 1.5 million pounds, and it will be powered into the sky by six first stage RD-276 engines producing more than 2 million pounds of thrust.

The Inmarsat 5 F1 satellite weighs 6,100 kilograms, or 13,448 pounds at liftoff. Inmarsat 5 F1 was transitioned to internal power a few minutes ago.

T-minus 12 minutes. The final launch pad workers evacuate to a safe distance away from the rocket.

With 15 minutes left in the countdown, everything remains on schedule for launch at 1212 GMT (7:12 a.m. EST; 6:12 p.m. Baikonur time). It will take more than 15 hours to deploy Sirius FM6 in the proper orbit.

The Proton rocket's first stage will blast off powered by six RD-276 engines producing more than 2 million pounds of thrust. The 191-foot-tall launcher will ascend northeast from Baikonur, dropping its first stage 2 minutes after liftoff, giving way to the Proton's second stage RD-0211 main engine for a three-and-a-half minute burn.

The Proton's third stage, using a RD-0213 main engine with 131,000 pounds of thrust, next will fire for about four minutes. Separation of the 13.1-foot-diameter nose cone occurs during the third stage burn at T+plus 5 minutes, 47 seconds.

The Breeze M upper stage will assume control at T+plus 9 minutes, 42 seconds, when it separates from the Proton's third stage. Five Breeze M engine burns are planned over a 15-hour period to inject Inmarsat 5 F1 in the proper geosynchronous transfer orbit.

Liftoff of the Proton rocket is 30 minutes away. This will be the:

• 392nd Proton rocket launch since 1965
• 84th International Launch Services Proton since 1996
• 70th Proton M using a Breeze M upper stage since 2001
• 16th Boeing satellite on ILS Proton
• 3rd Inmarsat satellite on ILS Proton
• 9th Proton of 2013

The launch pad gantry has moved away from the Proton rocket at Baikonur, revealing the silver booster as the countdown is inside the final hour until liftoff.

The Proton rocket and Breeze M upper stage are fully fueled with liquid hydrazine and nitrogen tetroxide propellants as dusk falls on the Baikonur Cosmodrome, where it is currently 5:30 p.m. local time.

Final preparations are getting underway in Kazakhstan ahead of today's Proton rocket launch of broadband communications satellite for Inmarsat of London.

The 19-story launcher is set to take off at 1212 GMT (7:12 a.m. EST) on a 15-hour flight to deliver the Inmarsat 5 F1 satellite to an egg-shaped geostationary transfer orbit.

The launch is scheduled for 6:12 p.m. local time at the Baikonur Cosmodrome in Kazakhstan.

Check out a launch timeline showing details of the Proton/Breeze M mission.

Inmarsat 5 F1 will finish the job of putting itself in an orbit 22,300 miles over the equator a few weeks after launch.

Based on the Boeing 702HP series satellite bus built by Boeing Co., Inmarsat 5 F1 is the first of four satellites for Inmarsat's Global Xpress mobile broadband communications service.

A Russian Proton rocket is poised for liftoff Sunday with a spacecraft to kick off Inmarsat's $1.6 billion initiative to expand access to high-speed broadband satellite communications services.

The 191-foot-tall rocket is set for launch at 1212 GMT (7:12 a.m. EST) Sunday from the Baikonur Cosmodrome in Kazakhstan, where it will be 6:12 p.m. local time.

At the top of the Proton rocket is the Inmarsat 5 F1 telecommunications satellite, a 13,448-pound platform built by Boeing Co. to beam super-fast broadband to customers for London-based Inmarsat's Global Xpress service.

"Global Xpress is the result of three years of planning and, together with a fourth GX satellite we ordered recently from Boeing, represents an investment of US$1.6 billion in our next generation of high bandwidth, high capacity, mobile broadband communications satellites," said Rupert Pearce, CEO of Inmarsat. "Global Xpress will ensure our satellite services fully support the current and future needs of end-users across the world - whether on land, at sea or in the air."

Three Global Xpress satellites are set for launch before the end of 2014, all flying on Proton rockets marketed by International Launch Services, the U.S.-based, Russian-owned company responsible for commercial Proton launch services.

Designed for a 15-year design life, each Inmarsat Global Xpress satellite will customers on boats, airplanes and other mobile platforms with high-speed Internet links.

The Russian Proton rocket, built by Khrunichev State Research and Production Space Center, will launch east from Baikonur, with its three core stages boosting Inmarsat 5 F1 and a Breeze M upper stage into a suborbital trajectory less than 10 minutes after liftoff.

The Breeze M upper stage will fire five times over 15 hours to put the spacecraft into a "supersynchronous" transfer orbit more than 40,000 miles above Earth at its highest point.

Inmarsat 5 F1 will use its on-board engine to circularize its orbit 22,300 miles high in a geostationary orbit to match the speed of Earth's rotation.