Ariane flight VA241

Ariane flight VA241

Company type	Space launch mission
Industry	Aerospace / Spaceflight
Founded	January 25, 2018 (2018-01-25) in Kourou, French Guiana
Headquarters	Kourou , French Guiana
Area served	Global (space)
Key people	Stéphane Israël (Arianespace CEO and chairman)
Products	Launch services for geostationary satellites

Ariane flight VA241 was an Ariane 5 mission launched from the Guiana Space Centre on 25 January 2018 at 22:20 UTC.

Payload

The rocket transported two geostationary satellites, SES-14 and Al Yah 3, with a total payload mass near . Both satellites were installed on the SYLDA dual-payload adapter housed within the extended upper stage fairing.

SES-14

SES-14, manufactured by Airbus Defence and Space in Toulouse for SES based in Luxembourg, occupied the upper position. At launch, it had a mass of and carried the NASA-sponsored GOLD instrument. This satellite marked the second Airbus-built platform using the Eurostar E3000 EOR bus to be launched by Arianespace.

Al Yah 3

Al Yah 3, produced by Northrop Grumman Innovation Systems (formerly Orbital ATK) in the United States for Yahsat of the United Arab Emirates, was mounted beneath SES-14. With a liftoff weight of , it was the inaugural satellite utilizing Orbital ATK's GEOStar-3 bus deployed by Arianespace.

Launch date

This mission represented the first Ariane 5 launch of 2018 and was planned within a 45-minute launch window beginning at 22:20 UTC on 25 January. The ignition sequence started precisely at the opening of this window from Ariane Launch Complex No. 3 (ELA-3) located in Kourou, French Guiana.

Orbit

The objective was to place both spacecraft into a super-synchronous transfer orbit characterized by an apogee near , a perigee around , and an inclination close to 3°, with the operation lasting approximately 35 minutes and 7 seconds.

Countdown and flight sequence

The countdown and flight milestones included:

Time	Event
T-11:23	Start of final countdown
T-10:33	Electrical system verification
T-04:38	Commencement of main stage propellant loading
T-03:28	Upper stage propellant loading begins
T-03:18	Vulcain engine chilldown procedure
T-01:15	Telemetry and command system checks
T-00:07	Confirmation of “all systems go” initiating synchronized sequence
T-00:04	Pressurization of propellant tanks for flight readiness
T-00:01	Transition to onboard power supply mode
T-00:00:05	Command issued to open cryogenic arms
T-00:00:04	Onboard systems assume control authority
T-00:00:00.00	Reference time
T+00:00:01	Ignition of main stage engine
T+00:00:07.05	Activation of solid rocket boosters
T+00:00:07.3	Liftoff
T+00:00:12.4	Completion of vertical ascent; initiation of pitch maneuver
T+00:00:17	Start of roll maneuver
T+00:02:19	Separation of solid boosters
T+00:03:18	Jettisoning of payload fairing
T+00:07:21	Signal acquisition by Natal tracking station
T+00:08:51	Conclusion of main stage thrust phase
T+00:08:58	Separation of main stage
T+00:09:01	Ignition of upper stage engine
T+00:13:36	Signal acquisition by Ascension tracking station
T+00:18:19	Signal acquisition by Libreville tracking station
T+00:22:56	Signal acquisition by Malindi tracking station
T+00:24:46	Injection into target orbit
T+00:27:05	Deployment of SES-14 satellite
T+00:33:22	Separation of SYLDA adapter
T+00:35:07	Deployment of Al Yah 3 satellite

Anomaly

Telemetry signals were lost roughly between 9 and 9.5 minutes into the flight, coinciding with the separation of the main stage (EPC) and the ignition of the upper stage (ESC-A).

Approximately one hour following liftoff, Arianespace CEO and chairman Stéphane Israël disclosed the occurrence of an anomaly, explaining that communication was interrupted shortly after the upper stage began ignition. He indicated that although the payloads were probably placed into orbit, customers had yet to establish contact with their satellites pending further evaluation. He expressed regret over the event and assured full transparency.

Later that evening, Arianespace issued a press statement confirming telemetry remained lost until mission completion; however, both payloads successfully separated and were inserted into Earth orbit, with customers subsequently acquiring satellite signals. A subsequent release detailed that SES and YahSat verified their satellites’ health despite deviations in trajectory; telemetry loss occurred at 9 minutes 26 seconds post-liftoff as a result of this trajectory divergence.

On 26 January 2018, SES revealed that while its satellite remained operational, a revised orbit-raising strategy was necessary, causing a delay of approximately four weeks in reaching geostationary orbit. The satellites were not delivered to their planned super-synchronous transfer orbit (with an apogee of 45,000 km and an inclination of 3°). Orbital parameters indicated a slight apogee discrepancy of about 2,000 km but a substantial inclination error near 18°.

The root cause of the anomaly was traced to an incorrect launch azimuth at liftoff, including an unplanned slow roll maneuver that occurred immediately after liftoff instead of the typical initiation around 17 seconds later.

Preliminary investigations attributed the failure to human error during Guidance, Navigation, and Control (GNC) programming combined with inadequate verification processes. The launch team reportedly omitted a secondary check of guidance computer settings to avoid duplicate efforts, which compromised reliability. Both Arianespace and ArianeGroup asserted that control procedures remained unchanged, while restructuring operations under ArianeGroup’s leadership to enhance engineering oversight.

Frédérique Vidal, Minister of Higher Education, Research and Innovation, highlighted that the rocket flew unusually close to Kourou city rather than over it as is standard practice. Ordinarily, Range Safety Officers or onboard Autonomous Flight Termination Systems would destroy any vehicle deviating from its course immediately. However, when destruction was contemplated in this case, the rocket had already passed near Kourou; terminating it at that point risked debris falling on populated areas. Consequently, despite trajectory deviations, the flight was allowed to continue.

Aftermath

A joint inquiry panel, established by the European Space Agency (ESA) alongside NASA, was led by ESA's inspector general to investigate the reasons behind the Ariane 5's trajectory deviation. The findings, published on 22 February 2018, revealed that engineers had programmed the inertial navigation units with an azimuth angle of 90°, which is typical for geostationary transfer orbit (GTO) missions. However, the mission required a 70° azimuth to reach the atypical supersynchronous transfer orbit (SSGTO) assigned to these payloads. This misconfiguration resulted in the spacecraft veering off course by 17°. The standard validation procedures failed to detect this incorrect azimuth setting. The request to alter the orbit originated suddenly from Al Yah 3's manufacturer (Orbital-ATK), aiming to deploy the satellite at a perpendicular angle relative to the launch vehicle’s trajectory.

Both satellites had to modify their orbital insertion strategies, leading to prolonged commissioning periods. SES-14 needed roughly an additional four weeks, pushing its operational start from July to August, yet it is still projected to achieve its intended service lifespan. Initially slated for a Falcon 9 launch—which requires more fuel due to higher inclination trajectories—SES-14 ultimately benefited from this adjustment. SES affirmed that NASA’s Global-scale Observations of the Limb and Disk (GOLD) instrument data quality was unaffected.

Following initial concerns, Al Yah 3 was verified to be in good condition; its orbital maneuvering plan was updated to meet mission goals. By 30 May 2018, it had attained its designated geostationary orbit and completed all in-orbit tests, with service commencement anticipated around July 2018, aligning with the start of a new Eutelsat fiscal year. Nevertheless, the additional fuel consumed during recovery operations shortened Al Yah 3’s expected operational duration to about nine years. Yahsat projected insurance claims could reach up to half its insured amount, approximately US$108 million.

This incident brought an end to Ariane 5’s record of 82 consecutive successful launches dating back to 2003.

External links

• Ariane Flight VA241 (Arianespace website)