The final launch of Europe’s advanced heavy lifter, Ariane 5, is scheduled for Friday, June 16, from the European Space Base in Kourou, French Guiana. But that plan simply changed.

“A critical function appeared to be at risk of redundancy on Ariane 5. In accordance with safety requirements, Arianespace has decided to delay the launch of the #VA261 launch vehicle. Analysis continues to determine the new launch. Arianespace, the French company that operates Ariane 5, today (June 15) He said on Twitter: (VA261 is Arianespace’s name for this mission.)

“The satellite and its satellites Heinrich-Hertz-Satellit and Syracuse 4B are undergoing final assembly in stable and safe conditions,” the company wrote in another tweet.

As stated in the second tweet, the final Ariane 5 mission is to fly two satellites. Arianespace writes in its mission statement that the Heinrich-Hertz-Satellit is a German spacecraft designed to research and test new communication technologies and scenarios.

Syracuse 4B is also a communications satellite to be operated by the French military. Arianespace writes that the spacecraft will “allow the French armed forces to remain in constant communication during deployment.”

“Syracuse 4B will be fully protected against the most extreme methods of jamming,” the company said. Designed to protect French sovereignty, the satellite will also be able to support NATO and EU-led operations.”

Arianespace operates Ariane 5 for the European Space Agency (ESA). This heavy rocket debuted in 1996 and has now done over 100 launches, including some key missions.

Ariane 5, for example, launched ESA’s Rosetta comet tracking mission in 2004, the agency’s JUICE Jupiter probe last April, and NASA’s James Webb Space Telescope in December 2021. Ariane 5’s successor isn’t quite ready to take over. The Ariane 6 heavy lifter, which has been in development for ten years, is expected to begin flying before the end of 2023.