Freezing, foggy conditions at Baikonur Cosmodrome in Kazakhstan did nothing to prevent Russia’s venerable Proton-M booster from successfully rocketing aloft on its seventh mission of 2013, which intends to deliver the 13,000-pound (5,900-kg) Inmarsat 5-F1 satellite into geostationary transfer orbit for the U.K.-headquartered International Maritime Satellite Organisation. Operated by International Launch Services (ILS), the three-stage Proton lifted off on time from Launch Complex 39 at Baikonur’s Site 200 at 6:12 p.m. local time (7:12 a.m. EST) Sunday, 8 December, and at the time of writing the rocket’s Briz-M upper stage was midway through executing five “burns” to inject the payload into its proper orbital position.
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 London 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 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.
Final preparations for today’s mission got underway about nine hours before liftoff, as technicians worked to fuel-up the Proton’s three stages with a mixture of nitrogen tetroxide and unsymmetrical dimethyl hydrazine. 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 provided the initial impetus to boost Inmarsat 5-F1 toward space. At T-5 minutes, the Briz-M upper stage was transferred to internal power and confirmed the health of its on-board systems. Ignition of the RD-276 engines commenced at T-2.7 seconds, with all six powerplants 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.
Within seconds of clearing the tower, the vehicle disappeared into a bank of thick fog. A little over a minute into the ascent, the Proton encountered a period of maximum aerodynamic stress (known as “Max Q”) on its flight surfaces, and the separation of the first stage occurred at the two-minute point. The vehicle’s second stage then picked 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—at 6:22 p.m. Baikonur time (7:22 a.m. EST)—by which time the vehicle had been precisely established onto a suborbital trajectory.
After a 90-second period of coasting, the turn next came for the Briz-M, which has exhibited a mixture of success and failure since its maiden voyage in May 2000. Last year, 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. Then, in March 2013, 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 currently midway through the procedure of executing 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. According to AmericaSpace’s Launch Tracker, the first burn got underway at 6:23:16 p.m. Baikonur time (7:23:16 a.m. EST), about 11 minutes into the mission. “This burn will last for 4 minutes 31 seconds,” explained the Tracker, “before entering an extended coast phase.” A second burn then got underway at 8:02 p.m. Baikonur time (9:02 a.m. EST), followed by the beginning of the third burn at 10:34 p.m. Baikonur time (11:34 a.m. EST). Based on current estimates, Inmarsat 5-F1 should be injected directly into its geostationary orbit about 15 hours and 31 minutes into the mission—at about 9:43 a.m. Baikonur time Monday (10:43 p.m. EST Sunday)—and should communicate with ground stations shortly thereafter.
Although today’s mission is the seventh Proton flight executed by 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 now supported no less than 392 discrete 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 on 25/26 October by launching Sirius FM-6 and on 12 November by launching Raduga-1M-3.Missions » Inmarsat-5F1 »