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Proton delivers Ekspress-AM8 A Proton rocket successfully launched a light-weight communications satellite for the Russian satellite operator. The mission was also the third attempt to flight-test the unlucky Block DM-03 upper stage, which had never made it into orbit in two botched missions of the Proton rocket in 2010 and 2013. With the flawless delivery of Ekspress-AM8, the new variant of the veteran Block-D stage, featuring enlarged propellant tanks and affording larger payload, was finally certified for the high-profile missions to replenish Russia's GLONASS navigation constellation. Even more importantly, the door is now open to adapt the same space tug for the new-generation Angara-5 rocket.
Proton lifts off with Ekspress-AM8 on Sept. 14, 2015.
Ekspress-AM8 spacecraft Developed at ISS Reshetnev in the city of Zheleznogorsk, the Ekspress-AM8 satellite was based on the company's standard Ekspress-1000NTV platform. The transponder payload for the satellite was developed by the French division of the Thales Alenia Space company. The payload included 42 transponders operating in C-, Ku and L-band of radio frequencies. The satellite was developed for the Federal State Enterprise Kosmicheskaya Svyaz, previously known as the Russian Satellite Communications Company, RSCC. According to the company, the spacecraft will be used for television broadcasts, data transmissions, including high-speed Internet access, multimedia services, telephone and mobile communications during its 15-year life span. From its orbital position over the Atlantic Ocean, Ekspress-AM8 will be able to provide communications over much of Europe, Middle East, Africa, South America and Eastern part of North America. According to the Russian Ministry of Communications, Ekspress-AM8 was funded with non-federal funds and will be used to provide most advanced forms of communications throughout the European part of Russia, Europe, Africa, Middle East and Latin America. ISS Reshetnev also quoted secured government communications among services provided by the satellite.
General architecture of the Ekspress-AM8 satellite, when deployed in orbit. Credit: ISS Reshetnev
Known specifications of the Ekspress-AM8 satellite:
Torturous road to the launch pad The launch of Ekspress-AM8 was initially expected in the third quarter of 2013, but around August 2013, it was postponed until 2014. At the end of 2012, ISS Reshetnev shipped a payload platform from the Ekspress-AM8 satellite to France for a six-month process of installation of transponder payloads developed by Thales Alenia Space. The module was then returned back to Zheleznogorsk for the final integration with the satellite. The thermal and vacuum testing of the satellite was completed in October 2014. By the end of 2014, as the satellite was undergoing final testing at ISS Reshetnev, the launch was scheduled for March 30, 2015, but at the beginning of 2015, the launch slipped to April 6, after the Proton mission with the Ekspress-AM7 satellite. Ekspress-AM8 finally arrived at Baikonur on March 2, 2015, in preparation for launch on April 6. However by March 18, reports surfaced on the web forum of the Novosti Kosmonavtiki magazine that small metallic particles had been discovered in the fuel line of the second stage of the Proton rocket assigned to launch the spacecraft. Coincidently, on the same day, the Block DM-03 upper stage for the mission arrived at the fueling station in Baikonur, which would begin the countdown for irreversible operations on stage due to corrosive action of propellant components, but, fortunately, the operation was stopped at the last minute. Additional inspections revealed a similar contamination problem in the third stage and the mission had to be postponed until at least May 18, or after the launch of the MexSat-1 satellite, which originally next in line in the Proton flight manifest. By March 20, when it became clear that the problem would not be resolved quickly, it was decided to transport Block DM-03 from the fueling station back to its processing area at Site 254 on March 27, because RKK Energia, which developed the stage, had only one railway car for thermal control and until then needed it for the transportation of the Soyuz TMA-16M spacecraft, which was set for launch on March 27. On April 8, the Interfax news agency reported that the commission investigating the contamination of the second stage on the Proton had ruled out the possibility of fixing the problem at the launch site and had made a decision to return the rocket back to its manufacturing plant in Moscow for thorough repairs. It would set back the launch date by several months until at least July or August 2015. Indeed, on April 13, the Interfax reported that the Ekspress-AM8 liftoff was re-scheduled for the third decade of August. Peculiarly, all other Proton missions, which involved Briz-M upper stage built at GKNPTs Khrunichev, like the rest of the rocket, were allowed to proceed, hinting at overzealous vigilance toward the vehicle, which was equipped with a Block DM-03 stage developed by a rival company. The particular rocket was rolled out off the production line in December 2014 and was originally intended to be equipped with a Briz-M stage, however in January 2015, it was reassigned for the Ekspress-AM8 mission with Block DM-03. By the beginning of May, the shipment of the third stage back to Baikonur was scheduled for June 15. In any case, new delays were caused by the Proton rocket failure with the MexSat-1 satellite on May 16, 2015. Around a week after the MexSat-1 accident, planners tentatively considered launching the Garpun military satellite in mid-July 2015, followed by the Ekspress-AM8 satellite at the end of July or beginning of August 2015. However by the end of June, it was decided to resume Proton missions with the Inmarsat-5 F3 launch, followed by Ekspress-AM8 in September. Initial plans aimed at launch on September 23 or 24, but by the end of July, Roskosmos set the launch for September 14. The agency wanted to test Block DM-03 as soon as possible to certify it for the high-priority mission to replenish Russia's Global Navigation System, GLONASS. As a result, during much of August, specialists involved in Proton operations had to prepare two rockets with two different upper stages and payloads almost in parallel, while also applying the lessons from the latest failure. The Ekspress-AM8 launch campaign was resumed at the beginning of August, aiming the liftoff on September 14, 2015, at 22:00 Moscow Time. The fueling of the Block DM-03 upper stage took place on Sept. 2, 2015. Two days later, Ekspress-AM8 was integrated with Block DM-03. After the assembly of the fairing, the payload section was integrated with the launch vehicle on September 8. The launch vehicle with Ekspress-AM8 satellite was rolled out to the launch pad on Sept. 11, 2015. The final integrated testing was successfully conducted on the pad on the same day, during a four-day processing cycle, instead of five-day timeline for most Proton missions.
While most Western communications satellites use their own propulsion to reach their operational orbits 36,000 kilometers above the Equator, the 2,100-kilogram Ekspress-AM8 is light enough to be carried directly into the geostationary orbit by the Block DM-03 upper stage. As a result, the Proton-M/Block DM-03 mission profile will be significantly different from a typical Proton launch with a commercial payload. Instead, the flight will resemble Soviet and Russian federal launches to the geostationary orbit, involving three firings of the upper stage. To deliver the Ekspress-AM8 satellite, a Proton-M/Block DM-03 No. 5L rocket was scheduled to lift off from Pad No. 24 at Site 81 in Baikonur on Sept. 14, 2015, at 22:00 Moscow Time, under power of six RD-276 engines. The separation of the first stage was to take place at T+2 minutes 3.8 seconds into the flight. The empty stage was to fall in the Karaganda Region in Kazakhstan. Moments before separation, the four-engine cluster of the second stage would take over the powered flight, initially firing through a lattice structure connecting two stages. The second stage was to separate at T+5 minutes 35.8 seconds in flight and crash near the border of the Tuva and Khakassia Republics of the Russian Federation. The third stage would then take over the powered ascent and just seconds later, at T+5 minutes 48.7 seconds into the flight, the payload fairing protecting the satellite from aerodynamic loads in the lower atmosphere was to split into two halves and drop away. Both fragments were expected to fall in the same drop zone with the second stage. The third stage was to fire its main RD-0213 engine until T+9 minutes 34.2 seconds into the flight. Still, the four-nozzle steering engine of the stage would continue firing for another 12 seconds to refine the velocity to an exactly precise parameter. The steering engine would shutdown at T+9 minutes 46.1 seconds into the flight. A fraction of a second later, the payload section, including the Block DM-03 upper stage and the Ekspress-AM8 satellite, was to separate at T+9 minutes 46.2 seconds into the flight into a suborbital trajectory. The third stage would then reenter the atmosphere and any of its surviving debris were to fall into the Pacific Ocean. After nearly six minutes in a ballistic flight, Block DM-03 upper stage was to fire its main engine for slightly more than a minute to insert itself and its payload into an initial parking orbit around the Earth. The stack would then fly passively around the planet for around one revolution. The main engine of Block DM-03 was re-start at T+1 hour 13 minutes 6 seconds and was to last for slightly more than eight minutes. The maneuver would stretch the orbit into an ellipse with an apogee (the highest point) near the altitude of the geostationary orbit 36,000 kilometers above the Earth's surface. The space tug and its cargo would then climb passively away from Earth for more than five hours. Upon reaching an apogee of the transfer orbit more than six and a half hours after the liftoff, Block DM-03 was to fire for the third time for almost four minutes to make the orbit circular at an altitude of 36,000 kilometers. The same maneuver would also tilt the orbital inclination from the latitude of Baikonur to match the plane of the Equator. The energy-hungry inclination change was intentionally conducted at the highest altitude to minimize the influence of the Earth's gravitational pull. Just one minute after the completion of the third engine burn and six hours 37 minutes after leaving Baikonur, Block DM-03 was to release Ekspress-AM8 into its operational orbit. The spacecraft is expected to be deployed over the Atlantic Ocean at an orbital position 14 degrees West longitude over the Equator. According to the official Russian sources, this launch scenario played out exactly as planned. Timeline of the Proton mission to deliver Ekspress-AM8 satellite on Sept. 14, 2015:
Several minutes after the planned separation of Ekspress-AM8 from Block DM-03 at 04:37 Moscow Time on Sept. 15, 2015, Roskosmos confirmed the successful delivery of the satellite. RKK Energia, which developed the 11S861-03 (DM-03) upper stage, announced that after the separation, the space tug had performed another maneuver to leave the vicinity of the satellite, which had been transferred under the control of its operator. The Interfax news agency quoted a spokesman for the Russian Military Space Forces as saying that after the release of the satellite, the Block DM-03 had conducted several firings to enter a 37,000-kilometer burial orbit. According to the satellite manufacturer, ISS Reshetnev, Ekspress-AM8 entered its target orbit, oriented itself toward the Sun and deployed solar panels. Ground control had established and maintained communications with the spacecraft, whose systems operated in nominal mode, the company said. Posters on the online forum of the Novosti Kosmonavtiki magazine confirmed that the satellite had completed its initial deployment in 17 minutes requiring little effort to stabilize it in correct orientation. According to ISS Reshetnev, on Sept. 20, 2015, Ekspress AM8 would test fire its electric engines, which would be eventually used to move the satellite into a temporary testing location in the geostationary orbit at 80.15 degrees West longitude. The completion of all in-orbit tests and the transfer of the satellite to its permanent operational position at 14 degrees West longitude was scheduled by the end of November, followed by the handover of the satellite for operational service at the beginning of December 2015, ISS Reshetnev's officials said. Also, on Sept. 15, the Russian Ministry of Communications announced that specialists of the Satellite Communications Company, GPKS Kosmicheskaya Svyaz had taken control of the satellite for the upcoming tests of its systems. Ekspress-AM was reported reaching its temporary testing orbital position at 80.15 degrees West longitude on Sept. 29, 2015.
A ground tracking telescope captured this view of an engine firing of the Block DM-03 upper stage during the delivery of Ekspress-AM8 into orbit. Credit: Viktor Voropaev / Novosti Kosmonavtiki
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