WASHINGTON — Program delays have forced Eumetsat to reserve a pair of Ariane 6 rockets for two European weather satellites originally anticipated to launch on Ariane 5 rockets. 

Eumetsat had signed a contract with Arianespace in 2015 to launch two or three Meteosat Third Generation satellites on Ariane 5 rockets between 2019 and 2023. Of those satellites, only one, MTG-I1, will be completed before Arianespace switches completely to Ariane 6 rockets. 

MTG-I1, an imaging satellite, will launch on an Ariane 5 rocket in 2022, the last year Ariane 5 will be available, Paul Counet, Eumetsat’s head of strategy, communication and international relations, told SpaceNews by email July 6. 

The sounding satellite MTG-S1, for which Eumetsat had a firm Ariane 5 launch contract, is now scheduled to launch in 2023 on an Ariane 6, Eumetsat announced July 2. The third satellite, MTG-I2, for which Eumetsat had an Ariane 5 contract option, will now launch on an Ariane 6 in 2025, the agency said. 

Counet said the switch for both satellites “was triggered by the unavailability of Ariane 5 after 2022.”

Thales Alenia Space of France and Italy is building the MTG satellites using platforms from German manufacturer OHB. The companies are building six MTG satellites in total — four imagers and two sounders — with half launching in the 2020s and the other half launching in the 2030s. 

A Thales Alenia Space spokesperson said “new technological challenges” discovered this year with the instruments for the first two MTG satellites, compounded by the coronavirus pandemic, delayed those satellites and had a knock-on effect on the third satellite. 

OHB Head of Investor Relations Martina Lilienthal declined to comment on the cause of the MTG manufacturing delays. The MTG satellites are based on OHB’s SmallGEO bus, which has experienced delays with early builds. 

Counet said Eumetsat plans to launch all three satellites with a co-passenger satellite, though discussions are ongoing about using the Ariane 62, the lighter version of Ariane 6 with two strap-on boosters, for the MTG-I2 satellite, which would likely make it a standalone mission. 

MTG-S1 will launch on an Ariane 64, the more powerful version equipped with four solid rocket boosters, he said. 

Caleb Henry is a former SpaceNews staff writer covering satellites, telecom and launch. He previously worked for Via Satellite and NewSpace Global.He earned a bachelor’s degree in political science along with a minor in astronomy from...