Less than a month since it successfully delivered a military communications satellite into orbit on behalf of the Russian Government, another venerable Proton-M booster stands ready at the Baikonur Cosmodrome in Kazakhstan, tracking a liftoff at 6:12 p.m. local time (7:12 a.m. EST) Sunday, 8 December. Rollout of the vehicle to the pad took place earlier today (Thursday, 5 December). The mission is being conducted under the auspices of International Launch Services (ILS), a joint U.S.-Russian organization, based in Reston, Va., which operates all Proton-M flights out of Baikonur. It will transport the 13,000-pound (5,900-kg) Inmarsat 5-F1 satellite into geostationary transfer orbit for the U.K.-headquartered International Maritime Satellite Organisation to provide up to 15 years of global mobile broadband communications for deep-sea vessels, in-flight connectivity for airline passengers, and high-resolution streaming of video, voice, and data.
This is the first of three Inmarsat-5 satellites ordered from Boeing in August 2010 for the purposes of providing faster worldwide broadband services. (A fourth was ordered in October 2013 to serve as a spare.) Each satellite is equipped with 89 Ka-band beams with flexible global coverage, whose key objectives include mobile broadband communications for deep-sea vessels, in-flight connectivity for airline passengers, and the streaming of high-resolution video, audio, and data transmissions. Since its formation in 1979, Inmarsat technologies have been employed for disaster relief and the distribution of aid, most recently providing telecommunications support in the catastrophic aftermath of Typhoon Haiyan in the Philippines. A pair of five-panel gallium arsenide solar arrays will provide the satellite buses with sufficient electrical power—about 15 kilowatts at the start of the mission and 13.8 kilowatts at the end—to support some 15 years of orbital operations. A xenon ion propulsion system will be utilized for stationkeeping.
Built in the United States, the Inmarsat 5-F1 spacecraft arrived at Yubileiny Airfield, near Baikonur, on 11 November, aboard an Antonov-124 transport aircraft. The flight had already experienced delays, due to rough weather over Canada and Iceland, and after touchdown the satellite’s container was maneuvered into a railcar for transfer to Hall 92A-50, where it arrived early on 12 November. “The offload requires highly skilled manpower,” ILS explained, “to meticulously transfer the [spacecraft] safely off the railcar, unpack it from its container and place it onto the payload adaptor for the fit check.” Over the next few days Inmarsat 5-F1 underwent rigorous testing, and on 15 November the restartable Briz-M upper stage for its mission arrived at Yubileiny Airfield. With the Briz-M housed in Hall 101 and the Proton-M vehicle itself in Hall 111, all hardware was on-site as the pre-launch campaign gathered momentum.
All components of the Proton-M, including its three main stages and the Briz-M, are fueled by a mixture of nitrogen tetroxide and unsymmetrical dimethyl hydrazine. Loading of these propellants aboard the Briz-M—whose single engine has the capacity to restart on up to eight discrete occasions to inject payloads into orbit—has already taken place, and the Russian State Commission formally granted approval for rollout to the pad on Wednesday, 4 December. With today’s successful rollout, and engineers entering Day One of Countdown operations, the pace will quicken in anticipation of Sunday’s launch.
Based upon previous timelines, fueling of the Proton’s three stages should get underway about nine hours before liftoff, which is presently scheduled for 6:12 p.m. local time (7:12 a.m. EST). The rocket’s first stage consists of a central oxidizer tank, surrounded by six outboard fuel tanks, each fed by an RD-276 engine, and these will provide the initial impetus to boost the mission toward space. At T-5 minutes, the Briz-M upper stage will be transferred to internal power and will confirm the health of its systems. Ignition of the six RD-276 engines will commence at T-2 seconds, ramping up to 100 percent of rated performance to produce 2.3 million pounds (1.04 million kg) of thrust at the moment of liftoff.
A little over a minute into the ascent, the Proton will encounter a period of maximum aerodynamic stress (known as “Max Q”) on its flight surfaces, and the separation of the first stage is timed to occur at the two-minute point. The vehicle’s second stage will then pick up the baton, with its four engines generating a combined 540,000 pounds (244,950 kg) of propulsive yield for a little over 3.5 minutes. Soon after second-stage separation, at T+5 minutes and 47 seconds, the Payload Fairing (PLF) will be jettisoned and the single-engine third stage will add a further 138,000 pounds (62,600 kg) of thrust for the next four minutes of flight. Shutdown of the third stage should occur at T+9 minutes and 42 seconds, by which time the vehicle will have been established onto a suborbital trajectory.
The turn will then come for the Briz-M, which has exhibited a mixture of success and failure since its maiden voyage. In August 2012, a premature shutdown of the Briz-M left Indonesia’s Telkom-3 and Russia’s Ekspress-MD2 satellites in useless orbits, and in December 2012 another launch glitch impacted the Yamal-402 satellite. Last March, a Proton-M/Briz-M successfully injected Mexico’s Satmex-8 communications satellite into orbit, and on 29 September another vehicle lofted Astra 2E. It has also performed flawlessly during October’s launch of Sirius FM-6 and again during last month’s flight of Raduga-1M-3. Capable of restarting up to eight times in flight, the Briz-M has a battery-powered lifetime of 24 hours and is scheduled to execute five “burns” to insert Inmarsat 5-F1 into orbit.
“The Briz-M will perform planned mission maneuvers,” noted ILS in its press kit for Sunday’s mission, “to advance the orbital unit first to a circular parking orbit, then to an intermediate orbit, followed by a transfer orbit, and finally to a supersynchronous transfer orbit.” The burns are calculated to last 4.5 minutes, 19.5 minutes, 9.5 minutes, 8.5 minutes, and 3.5 minutes. Assuming an on-time liftoff, the payload should be injected directly into its geostationary orbit about 15 hours and 31 minutes into the mission and should communicate with ground stations shortly thereafter.
Although Sunday’s mission will be the seventh Proton flight executed by International Launch Services (ILS) in 2013, it has been a troubled 12 months for the family of launch vehicles, which traces its heritage back to the 1960s and which has supported 391 missions. Built by the Khrunichev Research and State Production Centre, it has one of the most reliable track records of any rocket in the world, but suffered a dramatic and highly embarrassing launch failure on 2 July, seconds after liftoff. It was the Proton’s first catastrophic malfunction during first-stage flight in over 30 years and prompted several months of corrective actions and cutting managerial and organizational changes. In August, the Russian government formed the United Rocket and Space Corporation to consolidate the space sector, with Deputy Prime Minister Dmitri Rogozin announcing that it was “so troubled that it needs state supervision to overcome its problems.” A few weeks later the Proton returned triumphantly to flight on 29 September, delivering the Astra 2E communications satellite into orbit, and restored its reliability credentials in October with the Sirius FM-6 launch and last month with the Raduga-1M-3 launch.