|Russia launches a twin for its largest comsat
Russia's workhorse Proton rocket launched a new and improved version of the nation's largest indigenously built communications satellite on Oct. 21, 2014. However the Ekspress-AM6 satellite was released into less than ideal orbit.
Proton-M lifts off with Ekspress-AM6 on Oct. 21, 2014.
The liftoff of a Proton rocket with a Briz-M upper stage from Site 81 in Baikonur Cosmodrome took place as scheduled on Oct. 21, 2014, at 19:09:32 Moscow Time. The launch vehicle carried the Ekspress-AM6 communications satellite for the Russian Satellite Communications Company, RSCC.
According to the flight plan, the first, second and third stages of the Proton rocket fired for a total of 582 seconds, sending the payload section, including the Briz-M upper stage and the satellite, into a suborbital ballistic trajectory. Then, the first engine firing of the Briz-M upper stage inserted the stack into an initial parking orbit with an altitude of around 180 kilometers and an inclination 51.5 degrees toward the Equator. The Briz-M then fired its engine again to reach an elliptical (egg-shaped) orbit with an altitude of 272 by 5,007 kilometers.
The Briz-M fired for the third time to enter a 398 by 37,795-kilometer orbit then jettisoned its external propellant tank. (It was detected by a US radar on a 382 by 37,723-kilometer orbit with an inclination 49.56 degrees toward the Equator). Upon reaching an apogee, Briz fired for the fourth time to enter the so-called super-synchronous orbit, which is above 36,000-kilometer altitude required for communications satellites in order to synchronize their movement with the rotation of the Earth and thus appear "hanging" at same point in the sky. The separation of the satellite from the upper stage took place at 04:31 Moscow Time on October 22 or around 9.5 hours after the liftoff. Following the separation, Briz-M was scheduled to conduct two engine firings to enter a disposal orbit.
The 3,358-kilogram Ekspress-AM6 will need from three to four months to spiral down to its final geostationary orbit using four low-thrust but efficient electric engines powered by xenon gas. The same engines would be used for attitude control of the satellite during its 15-year-long operational lifetime and for eventual maneuvering to a burial orbit.
On the morning of October 22, ISS Reshetnev, the satellite developer, announced that a communication session with the spacecraft had confirmed that all mechanical systems onboard Ekspress-AM6 had deployed and it oriented itself toward the Sun. According to the plan, the satellite will reach its operational orbital position at the beginning of 2015, the company said.
Russian long-range cameras likely deployed at Byurokan Observatory in Armenia captured the 4th firing of the Briz-M immediately after the space tug shed its external tank during the delivery of Ekspress-AM6 on Oct. 21, 2014. Credit: A. Lapshin / ASPOS OKP via Viktor Voropaev and Novosti Kosmonavtiki
Ekspress-AM6 launch timeline on Oct. 21, 2014:
Despite claims by Roskosmos and ISS Reshetnev about the successful delivery of the Ekspress-AM6 into its planned orbit, multiple unofficial sources on Russian web forums presented strong evidence that the satellite's orbit was less than accurate, even if not wrong. The available information indicated that the satellite would still be able to reach its operational orbit but, possibly, at the expense of its onboard propellant cache, which would also be needed to maintain the spacecraft's position in space. As a result, the operational life of the satellite could be shorter than projected 15 years.
As evident from the available data about the actual duration of four engine firings of the Briz upper stage during the delivery of Ekspress-AM6, all its maneuvers had a tendency to last several seconds less than planned. The final fourth firing ended 24 seconds early or 50 meters per second short of required velocity. The resulting perigee (lowest point) of the satellite's orbit ended up to be 2,500 kilometers lower than planned, a Russian journalist Igor Lisov estimated.
Although parameters of the final orbit planned for the Ekspress-AM6 had not been yet released, they would have to be very close to those of the Ekspress-AM5 satellite, which was delivered into the correct orbit. The Ekspress-AM6 was expected to be released within 0.2 degrees of the projected orbital inclination and within 9.17 minutes of its planned orbital period (the time that takes for the satellite to make a single orbit around the Earth). However, according to a reliable source on the web forum of the Novosti Kosmonavtiki magazine, Ekspress-AM6 was released into orbit with an inclination 0.65 degrees toward the Equator and an orbital period of 1,373.0 minutes. The comparison of this data to the known orbital parameters of Express-AM5, makes it clear that Ekspress-AM6 delivery was completed outside of the required specifications:
Still, according to the same source, the satellite was expected to reach the correct orbit without shortening its life span.
Such devitations from the specified orbit were likely caused by imperfections of the flight control system onboard Briz-M rather than by a failure of its propulsion system, observers said.
The data from US radar also confirmed that Ekspress-AM6 had been circling the Earth 2,487 kilometers lower at its perigee than Ekspress-AM5 and its orbital inclination had been more than half a decree higher than that of its predecessor.
Due to lower than expected orbit after the launch, Ekspress-AM6 was making a single revolution around the Earth in around 22.8 hours, instead of 24 hours required for the spacecraft to "hang" over a single point over the Equator. As a result, Ekspress-AM6 started "drifting" relative to the Earth surface. Unless mission control was able to command the satellite to raise its orbit in time, it would leave the range of Russian ground stations, making communications impossible until its eventual reappearance on the other side of the globe. As of October 24, Ekspress-AM6 was located at 95 degrees East longitude.
As expected, following its botched launch on October 21, the Ekspress-AM6 satellite went out of contact with the Russian ground control stations as it drifted above the Western hemisphere. Only at the beginning of November, as the spacecraft reappeared over the horizon of Russian ground stations, mission control began sending commands to Express-AM6 to correct its wrong orbit. The goal was to enter a 36,000-kilometer circular equatorial orbit with an orbital period of 24 hours. After around two weeks of maneuvers, Ekspress-AM6 increased its orbital period by 20.7 minutes and decreased its orbital inclination by 0.05 degrees.
Ironically, the path to a geostationary orbit for this mission involved increasing an apogee (highest point) of the satellite's orbit above the operational altitude. In turn, it would increase an orbital period of the satellite to 24 hours and thus prevent its drifting out of range of mission control. According to an official letter to the Russian Satellite Communications Company, GKPS, cited on the online forum of the Novosti Kosmonavtiki magazine, a journey of Ekspress-AM6 to its operational orbit would have to be extended from planned three months to estimated four or five months. The spacecraft was now not expected to enter service until at least July 2015.
The Ekspress-AM6 successfully reached a 24-hour orbital period by December 8, 2014. It finally prevented the "drifting" of the satellite out of range of ground stations in Russia, however the spacecraft was yet to enter the correct circular orbit 36,000 kilometers above the Equator and reduce its orbital inclination to zero degrees, in order to completely stop its visible movement in the sky.
Still, the head of the ISS Reshetnev, Nikolai Testoedov told the Interfax-AVN news agency on December 11, that "...now we are transitioning into the testing phase and, as planned, inserting the satellite into its prescribed point in the geostationary orbit. Testoedov also said that the satellite's wrong orbit was corrected with the use of extra xenon gas onboard the satellite, thus leaving a full load of propellant necessary for a planned 15-year life span of the spacecraft.
Largest Russian communications satellite
The Express-AM6 satellite and its predecessor -- Ekspress-AM5 -- were built by the ISS Reshetnev in the Siberian town of Zheleznogorsk, Russia's chief developer of communications satellites. The company based the design of both spacecraft on its standard platform known as Ekspress-2000. The resulting seven-meter-tall satellites became the largest vehicles of their kind developed in Russia. They continued a long-running Ekspress (Express) series.
According to ISS Reshetnev, the communications payload onboard Ekspress-AM6 is comprised of 72 transponders operating in four bands of radio frequencies. A total of 11 antennas onboard Ekspress-AM6 include a three-mirror dish for Ka-band transponders and two steerable antennas (one more than on Ekspress-AM5) for Ku-band transponders. The satellite would be able to provide such services as mobile presidential and governmental communications, digital television and radio-broadcasting services, multimedia (telephony, videoconferencing, data transmission, access to the Internet) and VSAT networks. Besides European Russia and Western Siberia, Ekspress-AM6 would be able to cover Central Europe, Africa and the Middle East.
The dry (unfueled) mass of Ekspress-AM6 was expected to be just 20 kilograms higher than that of its predecessor -- Ekspress-AM5 -- however a total mass for the second satellite would be brought to the same amount of 3,358 kilograms in order to simplify the planning of the launch. At the same time, the xenon tank for the satellite's maneuvering thrusters was lightened, which afforded to increase the propellant load from 284 kilograms onboard Ekspress-AM5 to 316 kilograms for its successor.
From the outset of the project, the Ekspress-AM6 satellite was intended for deployment at 53 degrees East longitude over the Equator for a 15-year service. At that orbital position, the new spacecraft would replace the Ekspress-AM22 satellite, which by that time had outlived its operational life. However after the loss of the Ekspress-AM4R satellite in a launch mishap on May 16, 2014, the Ministry of Communications hinted that it had been considering sending Eksprees-AM6 at 80 degrees East longitude originally intended for the lost satellite in order to "protect" Russia's ownership of that orbital slot, even though it would not be an optimal position for the replacement satellite. However, the idea was later dropped.
During the launch and its first year of operation, Ekspress-AM6 was insured by OSAO Ingosstrakh for 5.5 billion rubles.
On Aug. 12, 2009, ISS Reshetnev reached an agreement with the Russian Satellite Communications Company, RSCC, to develop a pair of new-generation communications satellites, Ekspress-AM5 and Ekspress-AM6. However in the summer of 2010, Kazakhstan imposed a ban on all launch trajectories for Proton rockets from Baikonur Cosmodrome but the one enabling to reach a parking orbit with an inclination 51.6 degrees toward the Equator. It left the Proton rocket more than 200 kilograms short of the payload needed to deliver Ekspress-AM5 and AM6, whose mass was estimated at the time at 3,250 kilograms. Before the ban, the rocket had an advantage of heading further south, entering a parking orbit with an inclination 48 degrees.
To resolve the problem, ISS Reshetnev proposed to equip both satellites with highly efficient electric engines, which would complete the job of the underpowered launch vehicle during the trip to orbit. The main drawback of the proposal was a prolonged period between the launch and the arrival of the satellite to its final orbit due to very low thrust of electric engines. After a careful analysis, the scheme was approved in July 2012. ISS Reshetnev quickly developed a high-pressure propellant tank for around 300 kilograms of xenon to be fitted into the satellite.
During the first half of 2012, the launch was planned for the second quarter of 2013 and by September of that year it was postponed to the third quarter of 2013. In November 2012, the launch slipped to October or November 2013.
During the second half of 2012, ISS Reshetnev reported that the qualification model of the new solar panel rotation mechanism intended for Ekspress-AM5 and Ekspress-AM6 satellites had been completed. The device enabled channeling power from the electricity producing panel to the main body of the satellite. Soon afterwards, the company also successfully conducted autonomous tests of the satellite's attitude control system. The new software for the spacecraft was also qualified for the flight, clearing the way for integrated tests of the flight-worthy satellite. The transponders for the spacecraft arrived from Canada in the Fall of 2012. The assembly of the service module approached completion in November 2012. By the end of the year, ISS Reshetnev started integration of the payloads with the service module, which was to continue until mid January 2013. Electric tests started in the first quarter of 2013 and were planned to continue until mid-March. By October 2013, the mission was postponed until 2014. The launch was then scheduled for July 4, 2014.
Developments in 2014
By the end of April 2014, the launch of Eksprees-AM6 was set for July 4. To meet this launch date, the spacecraft arrived to Baikonur on May 26. However by that time, the launch had to be postponed to the end of July, at the earliest, pending the investigation of the latest Proton accident just 10 days earlier.
By the end of June, within the Proton's return-to-flight manifest, the launch of Ekspress-AM6 was set for October 21. Following the Proton's successful launch on September 28, the Briz-M upper stage for the Express-AM6 mission was loaded with propellant during the first week of October. It was integrated with the satellite on October 8. A day later, the payload section was covered with a payload fairing. On October 14, the completed payload section was integrated with the three lower stages of the Proton rocket. On October 16, a fully assembled vehicle left Building 92-A50 and traveled to a specialized site for a two-day loading of pressurized gas onboard Briz-M. On October 18, at 04:30 Moscow Time, the Proton with Ekspress-AM6 was rolled out to a launch pad at Site 81 in Baikonur.
Loss of Ka-band in 2020
As of March 25, 2020, satellite operators reported a loss of Ka-band capacity provided by Ekspress-AM6 due to an anomaly within the liquid radiator systems aboard the spacecraft. By March 30, the thermal control system failed completely forcing to turn off 30 out of 72 transponders aboard the satellite, according to the information of the Russian procurement service.
The pre-launch processing of the Ekspress-AM6 satellite.
Proton with Ekspress-AM6 shortly after its arrival to the launch pad on October 18, 2014.
Known contractors in the Ekspress-AM6 project:
Known specifications of the Ekspress-AM6 satellite:
Original specifications of Ekspress-AM5 and Ekspress-AM6:
Ekspress-AM6 in deployed configuration. Credit: ISS Reshetnev
Click to enlarge. Credit: Roskosmos
Ekspress-AM6 and Briz-M stage are being prepared for integration with a payload fairing on Oct. 10, 2014. Click to enlarge. Credit: Roskosmos
Payload section is being integrated with the Proton rocket on Oct. 13, 2014. Click to enlarge. Credit: Roskosmos
The Proton rocket with the Ekspress-AM6 satellite is delivered to the fueling site, TZP, for loading low-pressure tanks of the Briz-M upper stage with propellant on Oct. 17, 2014. Click to enlarge. Credit: Roskosmos
Click to enlarge. Credit: Roskosmos
Click to enlarge. Credit: Roskosmos
Proton with Ekspress-AM6 shortly after its arrival to the launch pad on Oct. 18, 2014. Click to enlarge. Credit: Roskosmos
Click to enlarge. Credit: Roskosmos
Proton-M lifts off with Ekspress-AM6 on Oct. 21, 2014. Click to enlarge. Credit: Roskosmos