SYRACUSE IV (SYstème de RAdioCommunication Utilisant un SatellitE, formerly COMSAT-NG) is a geostationary military satcom programme designed to replace the Syracuse 3A and Syracuse 3B satellites currently in orbit.

The Syracuse IV programme intends to develop, sustain, build and orbit two geostationary satellites.

The French defence procurement agency DGA has tasked the consortium of Airbus Defence & Space and Thales Alenia Space, the two Syracuse IV prime contractors, with developing two types of satellite. Airbus Defence & Space will be supplying a satellite built around its Eurostar 3000 all-electric spacecraft bus, while Thales Alenia Space is developing another all-electric satellite around its SpaceBus Neo 100 bus.

Syracuse IV is developing a number of innovations to improve communications for the armed forces. These include new main antennas and new ground control centres, as well as larger frequency bands (X band and Ka band) and an anti-jamming system to boost communications capacity, flexibility and resistance to jamming. The two satellites will carry identical payloads.

Syracuse 4A was launched by an Ariane 5 vehicle from Kourou in October 2021. Its in-orbit acceptance review took place in September 2022 with the expected level of permormance. Syracuse 4B was also launched from Kourou by Ariane 5, during its final flight, in July 2023.