In a successful return to flight following a trajectory error on the previous launch, an Ariane 5 ECA successfully placed two major communications satellites, DSN-1/Superbird 8 and Hylas 4, into a Geosynchronous Transfer Orbit (GTO). The launch took place at 2134 GMT on 5 April 2018 from the Kourou launch site in French Guiana.
The Mitsubishi Electric Corp (MELCO) built 5,348kg DSN-1/Superbird 8 communications satellite will be used mainly for Japanese X-band military and government communications, but it also carries a commercial communications payload for the Japanese Space Communications Corp firm. The DSN-1/Superbird 8 satellite was originally planned for launch in 2016, but had been damaged during aircraft transit to the launch site and returned to the manufacturer for repair.
The Hylas 4 was a 4,050kg model built by Orbital ATK. This commercial communications satellite was carried for Avanti to provide high throughput communications over Africa and Europe.