January 31, 2023

Two Pléiades Neo Earth-imaging satellites lost in failure of Europe’s Vega C rocket

EDITOR’S NOTE: Updated at 12 p.m. EST (1700 GMT) with details from news conference.

Illustration of the Vega C rocket with its Zefiro 40 second stage firing. Credit: Arianespace

The final two spacecraft in Airbus’s four-satellite, 600 million-euro commercial Pléiades Neo Earth observation fleet crashed into the Atlantic Ocean shortly after launch from French Guiana Tuesday night, falling victim to a failure of a European Vega C rocket.

The Vega C rocket’s launch operator, Arianespace, confirmed the mission failed to place the two Pléiades Neo optical imaging satellites into orbit. The preliminary focus of the failure investigation centered on the Vega C rocket’s second stage.

The 114-foot-tall (34.8-meter) rocket lifted off from the Guiana Space Center at 8:47:31 p.m. EST Tuesday (0147:31 GMT Wednesday) with the Pléiades Neo 5 and 6 Earth-imaging satellites for Airbus Defense and Space. The target was a polar sun-synchronous orbit.

The Vega C’s powerful solid-fueled P120C first stage booster burned nearly two-and-a-half minutes, producing a million pounds of thrust to accelerate the rocket into the upper atmosphere. Heading north from the South American coastline, the rocket shed its spent first stage motor casing and fired a second stage Zefiro 40 motor to continue the climb into space.

But Arianespace officials said the rocket ran into trouble soon after the start of the Zefiro 40 motor firing.

“After the liftoff and the nominal ignition of P120C, which is the first stage of the Vega, an underpressure has been observed on the Zefiro 40, which is the second stage of the Vega,” said Stéphane Israël, Arianespace’s CEO. And after this underpressure, we have observed a deviation of the trajectory and a very strong anomaly. Unfortunately, we can say that the mission is lost.”

Telemetry showed a “progressive decrease” the chamber pressure in the Zefiro 40 solid rocket motor beginning about seven seconds after it ignited, following a good burn by the P120C first stage motor, said Pierre-Yves Tissier, Arianespace’s chief technical officer, in a press briefing Wednesday. The chamber pressure suddenly dropped at about T+plus 3 minutes, 28 seconds, about two-thirds of the way through the Zefiro 40’s planned burn.

Tissier said Wednesday that range safety officials at the Guiana Space Center sent a destruct command to the rocket when it veered off its planned course.

“I want to deeply apologize to our customer, Pléiades Neo and Airbus Defense and Space, for this failure tonight,” Israël said Tuesday night. “And we will now have to work with all our partners to better understand why the Zefiro 40 has not worked properly tonight, triggering the failure of the mission.”

Speaking to reporters Wednesday, Israël said a preliminary look at the data from the Vega C launch failure shows no impact on Europe’s Ariane 5 and Ariane 6 rockets. There are two flights of the workhorse Ariane 5 rocket remaining to launch next year before Europe moves on to the Ariane 6, which is scheduled to debut in late 2023. The Ariane 6 rocket shares the P120C solid rocket motor design with the Vega C, but so far, the investigation shows the failure Tuesday night was limited to the Zefiro 40 second stage.

An inquiry chaired by Arianespace’s chief technical officer and the inspector general of the European Space Agency will investigate the root cause of the Vega C launch failure.

Europe’s Vega C rocket on the launch pad in French Guiana, hours before liftoff on the doomed mission with the Pléiades Neo 5 and 6 satellites. Credit: ESA/CNES/Arianespace/JM Guillon

The Zefiro 40 second stage, like the Vega C’s other solid-fueled booster stages, is produced by the rocket’s prime contractor, the Italian aerospace company Avio. The second stage motor is designed to burn its supply of 40 tons (36 metric tons) of pre-packed solid propellant in about 90 seconds.

The Vega C rocket replaces the old Vega rocket’s solid-fueled first and second stages with wider, heavier motor casings. The third stage motor is unchanged, and the restartable liquid-fueled fourth stage has the same type of engine but carries more propellant. The upgraded Vega C is taller than the original Vega rocket configuration, and has a larger payload fairing provided by the Swiss company Beyond Gravity, formerly known as RUAG Space.

The wider Zefiro 40 second stage on the Vega C rocket replaces the Zefiro 23 motor on the basic model of the Vega rocket, adding 50% more solid propellant and generating 293,000 pounds of thrust.

The launch Tuesday night was the first commercial flight of Europe’s upgraded Vega C rocket, following the Vega C’s flawless inaugural test flight July 13.

Europe’s Vega rocket family has now suffered three failures in 22 flights. The three failures have occurred on the Vega rocket’s last eight launches, following 14 straight successful flights since the Vega launcher entered service in 2012.

Investigators blamed a 2019 launch mishap on a “thermo-structural failure” on the Vega rocket’s Zefiro 23 second stage. A 2020 launch failure was traced to misplaced cables on the Vega rocket’s liquid-fueled upper stage, called the Attitude and Vernier Upper Module.

The Vega rocket had amassed four straight successful launches, including the debut of the Vega C, before Tuesday night’s doomed mission.

The satellites lost on the Vega C rocket were the third and fourth spacecraft in a quartet of Airbus-built and -owned Earth observation satellites. The first two Pléiades Neo satellites launched in 2021 on separate Vega rockets, but Airbus put the third and fourth spacecraft of the constellation on the same mission to take advantage of the Vega C rocket’s heavier carrying capacity.

File photo of stacking of a Zefiro 40 second stage motor ahead of the first Vega C launch. Credit:
ESA-Manuel Pedoussaut

The Pléiades Neo satellites feature improvements over Airbus’s two first-generation Pléiades Earth observation satellites launched in 2011 and 2012. Airbus says it entirely funded the development of the Pléiades Neo satellites, with intentions to sell the imagery commercially to private companies and government users. The company announced the Pléiades Neo program in 2016, and Airbus assembled the Pléiades Neo spacecraft at its facility in Toulouse, France.

The four-satellite program was expected to cost Airbus about 600 million euros, or roughly $700 million. An Airbus spokesperson said Wednesday the Pléiades Neo satellites lost in the launch failure were insured.

The Pléiades Neo satellites can produce optical imagery of Earth’s surface with a resolution of 11.8 inches, or 30 centimeters, according to Airbus. That’s good enough to resolve features such as vehicles and road markings. The first two Pléiades satellites launched more than a decade ago have 19.6-inch, or 50-centimeter, resolution.

Airbus has released imagery from the first two Pléiades Neo satellites showcasing their capabilities, picturing lava flows from volcanic eruptions, large-scale music and sports events, and views of aircraft and rockets at airports and spaceports.

The imaging resolution of Airbus’s four Pléiades Neo satellites is comparable to the resolution provided by Maxar’s six-satellite WorldView Legion surveillance satellites due to begin launching next year. The companies are competitors, providing the highest-resolution Earth observation imagery on the global commercial market.

With the help of laser inter-satellite communications links, the Pléiades Neo satellites will be able to respond rapidly to tasking requests within a half-hour, according to Airbus.

The Pléiades Neo 5 and 6 satellites stacked one on top of the other before encapsulation inside the Vega C rocket’s payload fairing. Credit: ESA/CNES/Arianespace/P. Baudon

A single Pléiades Neo satellite, using a new agile pointing capability enabled by control moment gyroscopes, can turn side-to-side to observe the same location every two days. Once all four satellites are in orbit, the constellation will be able to image any location on Earth twice a day.

Each Pléiades Neo spacecraft is designed to operate for at least 10 years. One Pléiades Neo satellite can collect images covering an area of nearly 200,000 square miles (500,000 square kilometers) every day, Airbus says.

The applications for Pléiades Neo imagery include urban planning and city management, climate change assessments, and determining the impacts of pollution. The satellites can also be tasked to assess the damage from natural disasters, and the imagery also has military applications.

The Vega C rocket aimed to deploy the Pléiades Neo 5 and 6 satellites into a polar, or north-south, orbit about 385 miles (620 kilometers) above Earth.

Europe’s Vega rocket family is designed to carry small to medium-size satellites into orbit. Developed in partnership between Avio and the European Space Agency, the upgraded Vega C rocket is capable of hauling up to 5,070 pounds (2.3 metric tons) of payload mass to a 435-mile-high (700-kilometer) polar orbit, an increase over the 3,300-pound (1.5-metric ton) capacity of the basic model of the Vega rocket.

ESA and the European Commission reached an agreement with Arianespace last month to launch five satellites for Europe’s Copernicus Earth observing system on Vega C rockets. The new deal increased Arianespace’s backlog to 15 Vega missions, including 13 Vega C missions and two more launches with the original Vega rocket configuration.

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Follow Stephen Clark on Twitter: @StephenClark1.

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