Soyuz leaves Galileo satellites short of target orbit
A Russian-built rocket left a pair of European navigation satellites in a wrong orbit following its launch on August 22, 2014.
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Above: Soyuz lifts off with the first pair operational Galileo satellites on Aug. 22, 2014.
Above: Artist rendering of the operational version of Galileo satellite.
A Soyuz-ST-B rocket lifted off as scheduled from the ELS launch pad in Kourou, French Guiana on August 22, 2014, at 16:27:11 Moscow Time (8:27 a.m. EDT, 12:27 GMT, 9:27 a.m. local time). The launch vehicle carried two 730-kilogam Galileo FOC M1 satellites, where FOC stands for the Full Operational Capacity.
The launch seemed to be flawless, however at the end of the day on August 22, Arianespace, which managed the mission, announced that "complementary observations gathered after separation of the Galileo FOC M1 satellites on Soyuz Flight VS09 have highlighted a discrepancy between targeted and reached orbit. Investigations are underway. More information will be provided after a first flight data analysis to be completed on August 23, 2014."
Radar observations showed that three objects from the launch were in a 13,720 by 25,920-kilometer orbit with an inclination 49.7 degrees toward the Equator. Galileo FOC M1 No. 5 and No. 6 satellites (a.k.a. Doresa and Milena) were the first of 22 operational satellites scheduled to be inserted into a 23,522-kilometer orbit with an inclination 55.04 degrees toward the Equator.
The European Space Agency, ESA, then announced that "following the announcement made by Arianespace on the anomalies of the orbit injection of the Galileo satellites, the teams of industries and agencies involved in the early operations of the satellites are investigating the potential implications on the mission. Both satellites have been acquired and are safely controlled and operated from ESOC, ESA's Operations Center in Darmstadt, Germany. Further information on the status of the satellites will be made available after the preliminary analysis of the situation."
Peculiarly, during the live coverage launch, observers noticed wrong speed readings displayed along the visualizations of the launch. It seemed that its altitude parameters were fed into the speed channel. Speed parameters were dropped from screen during later part of orbital insertion. Still, all reports from mission control confirmed normal flight and the Arianespace declared the mission success shortly after the separation of the satellites.
Multiple independent sources analyzing the situation suggested that the Fregat upper stage had fired its engine for the right duration, however the stage's orientation in space during the second or both maneuvers had probably been wrong. According to Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics and a veteran space historian, the Fregat's angular orientation error during the engine firing could reach as much as 145 degrees.
According to industry sources, an investigation commission was formed in Moscow to look into the botched launch. Sources at RKTs Progress, the developer of the Soyuz rocket, and NPO Lavochkin, the developer of the Fregat upper stage, indicated that telemetry from the launch had showed normal performance of their respective systems.
Galileo launch sequence (for the FOC M1 mission):
The liftoff and first part of the mission proceeded nominally, leading to release of the satellites according to the planned timetable, and reception of signals from the satellites. It was only a certain time after the separation of the satellites that the ongoing analysis of the data provided by the telemetry stations operated by the European Space Agency (ESA) and the French space agency CNES showed that the satellites were not in the expected orbit.
The targeted orbit was circular, inclined at 55 degrees with a semi major axis of 29,900 kilometers. The satellites are now in an elliptical orbit, with excentricity of 0.23, a semi major axis of 26,200 km and inclined at 49.8 degrees.
Both the Fregat upper stage and the two satellites are in a stable condition and position that entails absolutely no risk for people on the ground. The residual propellants on the Fregat stage have been purged and the stage was depressurized normally.
According to the initial analyses, an anomaly is thought to have occurred during the flight phase involving the Fregat upper stage, causing the satellites to be injected into a noncompliant orbit.
Studies and data analyses are continuing in Kourou, French Guiana, and at Arianespace headquarters in Evry, near Paris, under the direction of Stéphane Israël, Chairman and CEO of Arianespace, in conjunction with the Russian partners in the Soyuz in French Guiana program (Russian space agency Roskosmos and the manufacturers RKTs Progress and NPO Lavochkin, as well as Arianespace's customer ESA and its industrial partners, to determine the scope of the anomaly and its impact on the mission.
"Our aim is of course to fully understand this anomaly," said Stéphane Israël, Chairman and CEO of Arianespace. "Everybody at Arianespace is totally focused on meeting this objective. Starting Monday, Arianespace, in association with ESA and the European Commission, will designate an independent inquiry board to determine the exact causes of this anomaly and to draw conclusions and develop corrective actions that will allow us to resume launches of Soyuz from the Guiana Space Center, CSG, in complete safety and as quickly as possible. The board will coordinate its work with Russian partners in the Soyuz at CSG program. Arianespace is determined to help meet the European Union's goals for the Galileo program without undue delay. We would like to thank ESA, the European Commission and CNES for the very productive discussions since becoming aware of the occurrence of the anomaly. While it is too early to determine the exact causes, we would like to offer our sincere excuses to ESA and the European Commission for this orbital injection that did not meet expectations."
The Moscow-based investigation commission into the Galileo launch accident was expected to convene for the first time on Monday (August 24). As of August 24, all publicly available data from the flight pointed toward a wrong orientation of the Fregat upper stage during its second engine firing. However whether it was caused by the faulty attitude control system, or by its software or by some failure during the flight remains a mystery. Peculiarly, the telemetry from the flight control system on the Fregat apparently indicated flawless performance of all systems.
By August 25, several reliable posters on the Novosti Kosmonavtiki web forum indicated that the attention had quickly focused on two out of 12 small thrusters that are used to keep the Fregat upper stage in right orientation during an unpowered flight and also place the stage in correct attitude for the firing of the main engine. It seems that the firing of two thrusters was interrupted, even though they had received all the correct commands from the flight control system. As a result, the Fregat started its second main engine firing in the wrong direction, causing the change in the orbital inclination toward the Equator, instead of boosting its altitude. The role of the flight control system in failing to detect or report this problem to ground control remained unclear.
The Fregat is equipped with 12 thrusters fed from a common hydrazine fuel distribution line. Four such thrusters are used to control the roll of the stage during the powered phase of the flight (when the main engine fires).
Following the major anomaly that occurred on August 22, 2014, during the Soyuz ST mission carrying two satellites in the Galileo constellation, Arianespace announced today, in conjunction with the European Space Agency
The commission is chaired by Peter Dubock, former ESA Inspector General. Its mandate is to establish the circumstances of the anomaly, to identify the root causes and associated aggravating factors, and make recommendations to correct the identified defect and to allow for a safe return to flight for all Soyuz launches from the Guiana Space Center (CSG).
The commission will start its work on August 28, 2014, and submit its initial conclusions as early as September 8, 2014.
The inquiry commission comprises the following members:
To maintain links with the Russian partners in the Soyuz at CSG program, the head of the Russian space agency Roskosmos, on request from the head of Arianespace, has designated Alexander Daniliuk, Deputy Director General of TsNIImash, as board liaison.
Arianespace Chairman and CEO Stéphane Israël said: "I would like to thank Peter Dubock for having accepted the chairmanship of this commission, which was appointed in conjunction with ESA and the European Commission and with the support of the space agencies from France (CNES), Germany (DLR) and Italy (ASI), along with a team of high-level European experts. The commission will now be able to carry out its work independently, operating
Also on August 25, Johann-Dietrich Woerner, the chairman of the German space agency, DLR, published an account of the failure. "The first problem became apparent when the two satellites proved unable to deploy their solar arrays as intended. A more detailed analysis then revealed that the eccentricity, the altitude and the inclination of the satellites' orbits with respect to Earth's equator did not meet specifications."
According to Woerner during its passive flight in the period between two engine firings, Fregat had failed to initiate the planned rotation around the longitudal axis of the spacecraft known as the barbecue mode. It is usually conducted to ensure even heating of the spacecraft by the Sun.
However Russian industry sources said that according to the telemetry from the Fregat upper stage, the barbecue mode had been implemented as planned. Still, it was not possible to immediately confirm that the rate of rotation was correct and its axis was pointed in the right direction to ensure that all sides of the spacecraft are evenly heated by the Sun.
One unlikely failure scenario that observers discussed on the Novosti Kosmonavtiki forum involved premature deployment of solar panels on Galileo satellites, which could dramatically shift the center of gravity of the Fregat/Galileo stack and result in its wrong orientation. However, the fact that the satellites were designed to be inactive during their ride on Fregat makes this hypothesis very unlikely. In addition, it would not explain the apparent interruption in the work of attitude control thrusters onboard Fregat.
Other scenarios for changing the orientation of Fregat could include some unexpected jet force that could affect the stage, such as sudden evaporation of ice from the surface of the vehicle.
Work at ESA’s ESOC control centre continues relentlessly on the two Galileo satellites. Despite the non-nominal orbit, the satellites are safely under control after they were released from the launcher upper stage and their orbital position was determined by the European ground teams deployed at ESOC in Darmstadt, Germany.
Controllers there, in cooperation with the satellite manufacturer OHB, confirm the good health and the nominal behavior of both satellites. A procedure to deploy the solar arrays that had remained partially folded on both satellites was successfully executed on the first satellite in the course of Monday night. A similar procedure will be executed soon on the second satellite.
Both satellites continue to be kept in a safe state, correctly pointing to the Sun, properly powered and fully under control of the ESA/CNES integrated team and the teams of OHB deployed at ESA’s control centre. In parallel, the teams are investigating the possibilities to exploit the satellites to their best despite the non-nominal injection orbit and within the limited propulsion capabilities of the satellites.
By August 28, specialists familiar with the operation of the Fregat upper stage and with basic details of the investigation had been able to discern a rough sequence of events that had likely led to the failure of the Soyuz mission with Galileo satellites last week. As it turned out, the so-called barbecue mode (a rotation of the Fregat stage to even out heating of the satellites by the Sun) is always preceded by a special "re-orientation" maneuver. It is designed to prevent sensitive mechanical gyroscopes onboard the stage from stalling. Such a re-orientation is conducted individually for each of three axis with a certain angular speed and over a certain time period.
It appears that during the delivery of Galileo satellites on August 22, at the very end of the re-orientation routine, the flight control system detected a wrong angular speed and sent commands to Fregat's thrusters to correct the situation. For a yet unknown reason, engines failed to achieve that, even though available telemetry confirms that electric valves activated the thrusters as directed. It seemed that thrusters failed to operate for some 100 seconds. Specialists were still debating what force or abstraction could prevent the thrusters from doing their job in the emptiness of space or whether firing engines somehow did not deliver required thrust. One hypothesis considered whether loose pieces of thermal insulation could block the engines.
To make matters worse, the flight control system also perceived that thrusters had worked and thus failed to recognize that they did not provide correct parameters to the Fregat. Instead, the flight control system completed all "re-orientation" maneuvers within the assigned time and concluded that the stage was in correct attitude to continue its mission.
Beyond this short period of time, there were no deviations from the flight program. Unfortunately, it was enough to begin the following "barbecue" mode with wrong orientation of the stage toward the Sun. Even worse, when the time came to fire the Fregat's main engine for the second time, the stage was pointing in a wrong direction. Surprisingly, to highly intelligent computers onboard Fregat everything looked normal.
It seems that a coincidence of several small glitches led to the overall failure of the mission. According to European officials, there was little chance that the Galileo FOC M1 satellites could be used for their intended purpose. Both spacecraft would need twice as much hydrazine propellant onboard to reach their target orbit.
By mid-September 2014, reports surfaced in the semi-official Russian press pointing at freezing of the Fregat's fuel supply line, because on this particular vehicle, it ended up next to another line providing super-cold helium to pressurize propellant tanks onboard Fregat. The resulting freezing would explain the failure of orientation thrusters to fire leading to the loss of the mission. According to the Interfax news agency, investigators found a similar assembly error on three out of more than 10 other Fregat stages being manufactured or prepared for flight at NPO Lavochkin.
A poster on the web forum of the Novosti Kosmonavtiki magazine explained that a close review of the assembly documentation for the Fregat stage had showed that there had been no specific requirement to keep hydrazine fuel lines away from the cold helium lines. Official instructions gave assembly workers flexibility on exact routing of those lines and only asked to avoid a configuration that would put mechanical pressure on the lines. As a result, on various vehicles, hydrazine lines would be either bundled together with "warm" drainage line of the propellant tank or with "cold" helium line. The thermal dynamics requirements for the Fregat stage were formulated early in its development process when only shorter engine firings had been planned. However, the Galileo FOC M1 mission had an ill-fated combination of a prolonged orbital insertion process with the assembly configuration that had placed the hydrazine line right next to the "cold" helium line. In this case, the real culprit in the failure of the mission would be an old, deep-rooted and really obscure design flaw rather than lack of quality control or poor manufacturing which are often blamed for recent Russian space failures.
Before the end of the first week of October, Russian officials were expected to provide their European partners with the final account of the failure and the investigative commission would make a final determination on the accident by October 7, 2014.
On October 7, following a meeting at Arianespace headquarters in Evry, near Paris, the Independent Inquiry Board announced its definitive conclusions into the August 22 Soyuz rocket failure to deliver Galileo FOC M1 satellites, the company announced on October 8.
According to Arianespace, conclusions draw on data supplied by Russian partners in the program, and are consistent with the final conclusions of the inquiry board appointed by the Russian space agency, Roskosmos. The Board's conclusions confirm that the first part of the mission proceeded nominally, which means that the three-stage Soyuz launcher was not at fault. The Inquiry Board also eliminated the hypothesis that the anomaly could have been caused by the abnormal behavior of the Galileo satellites.
The anomaly occurred during the flight of the launcher's fourth stage, Fregat, designed and produced by NPO Lavochkin. It occurred about 35 minutes after liftoff, at the beginning of the ballistic phase preceding the second
The scenario that led to an anomaly in the orbital injection of the satellites was precisely reconstructed, as follows:
The root cause of the anomaly on flight VS09 is therefore a shortcoming in the system thermal analysis performed during stage design, and not an operator error during stage assembly. The system thermal analyses have been reexamined in depth to identify all areas concerned by this issue.
Given this identified and perfectly understood design fault, the Board has chosen the following corrective actions for the return to flight:
These measures can easily and immediately be applied by NPO Lavochkin to the stages already produced, meaning that the Soyuz launcher could be available for its next mission from the Guiana Space Center as from December 2014.
Beyond theses corrective actions, sufficient for return to flight, NPO Lavochkin will provide Arianespace with all useful information regarding Fregat’s design robustness, which is proven by 45 successful consecutive missions before this anomaly, Arianespace said.
It was the ninth launch of the Soyuz rocket from French Guiana and the mission is known as VS09 in the flight manifest of Arianespace, that operates the Russian-built rockets based in Guiana along with Europe's own Ariane-5 and Vega rockets. At the time of final preparations for the FOC M1 mission, another launch with Galileo satellites was scheduled for the last quarter of 2014.
The operational Galileo satellites were built by a prime contractor OHB System, while their payloads were supplied by SSTL (Surrey Satellite Technology Ltd), a British subsidiary of Airbus Defense and Space.
On Jan. 26, 2010, Arianespace announced signing of a contract for five Soyuz missions to deliver pairs of Galileo FOC satellites.The first of these launches was previously delayed from December 2012 to the second half of 2013.
The first attempt to launch Galileo FOC M1 mission on August 21, 2014, was scrubbed less than eight hours before the liftoff scheduled for 16:31:14 Moscow Time (8:31 a.m. EST) due to bad weather. The Russian space agency, Roskosmos, then posted a press-release announcing that the mission was rescheduled for Aug. 22, 2014, at 16:27:11 Moscow Time (8:27 a.m. EST, 12:27 GMT). However Arianespace said that "another launch date will be decided depending on the evolution of the weather conditions in Kourou." By the end of the day, Arianespace reported that "a favorable trend in weather conditions is forecasted for tomorrow over the Guiana Space Center, Europe’s Spaceport. Therefore, Arianespace has decided to restart the countdown..."
Flight scenario of the FOC M1 mission.
Above: Artist rendering of the separation between Galileo satellites and a Fregat upper stage.
Next Galileo mission: VS11, FOC M2
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Last update: December 16, 2015
Galileo satellites inside the payload section of the Soyuz-ST-B rocket. Credit: ESA
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Soyuz lifts off with the first pair operational Galileo satellites on Aug. 22, 2014. Credit: Arianespace