|Ariane 5 ECA launch|
|Launch||5 April 2018, 21:34:00 UTC|
The launcher was carrying the DSN-1/Superbird-8 and HYLAS-4 geostationary satellites. The satellites were accommodated together on the SYLDA adapter inside the long version of the upper stage fairing, with a total payload mass of approximately 10,260 kilograms (22,620 lb).
Superbird-8, built by Mitsubishi Electric (with manufacturing management by NEC) for the DSN Corporation Japanese joint venture, was in the upper position. It had a mass at liftoff of about 5,348 kilograms (11,790 lb), hosting the DSN-1 payload for the Japanese Ministry of Defense. The satellite is a semi-classified payload due to military purpose.
The satellite was supposed to launch in mid-2016, but due to overpressurization within the container during shipping to the launch site that caused significant damage, the satellite was returned to the manufacturer for repair work and additional testing, delaying the launch for almost two years.
HYLAS-4 is a Ka-band communications satellite, that will occupy the 33.5° West orbital position, covering Africa and Europe. It has a design lifetime of 15 years and it is the second based on Orbital ATK's GEOStar-3 satellite bus to be launched by Arianespace.
The launch campaign activities started on 30 January 2018. DSN-1/Superbird-8 and HYLAS-4 arrived in French Guiana respectively on 6 February 2018 and 15 February 2018. They were fuelled between 22 March 2018 and 2 March 2018 and were integrated between 2 March 2018 and 28 March 2018.
The second Ariane 5 launch of 2018, just after the partial failure of VA241, was planned to take place within a launch window of 50 minutes starting on 5 April 2018 at 21:34 UTC (18:34 local time). The launcher engines effectively were ignited at the very beginning of that window, from Ariane Launch Complex No. 3 (ELA 3) in Kourou, French Guiana.
The mission was planned to last 33 minutes and 56 seconds, placing both satellites into a geostationary transfer orbit, with an apogee of about 35,786 kilometres (22,236 mi) and a perigee of about 250 kilometres (160 mi), at an inclination of about 3 degrees.
The planned sequence was as follows:
|T-11:23||Start of final countdown|
|T-10:33||Check of electrical systems|
|T-04:38||Start of filling of the main stage with liquid oxygen and liquid hydrogen|
|T-03:28||Start of filling of the upper stage with liquid oxygen and liquid hydrogen|
|T-03:18||Chilldown of Vulcain main stage engine|
|T-01:15||Check of connections between launcher and the telemetry, tracking and command systems|
|T-00:07||“All systems go” report, allowing start of synchronised sequence|
|T-00:04||Tanks pressurised for flight|
|T-00:01||Switch to on-board power mode|
|T-00:00:05||Opening command for the cryogenic arms|
|T-00:00:04||On-board systems take over|
|T+00:00:01||Ignition of the main stage|
|T+00:00:07.05||Ignition of solid boosters|
|T+00:00:12.3||End of vertical climb, beginning of pitch motion|
|T+00:00:17.1||Beginning of roll maneuver|
|T+00:07:53||Acquisition by the Natal tracking station|
|T+00:08:53||End of main stage thrust phase|
|T+00:08:59||Main stage separation|
|T+00:09:03||Ignition of the upper stage|
|T+00:13:48||Start of acquisition by the Ascension tracking station|
|T+00:18:25||Start of acquisition by the Libreville tracking station|
|T+00:23:07||Start of acquisition by the Malindi tracking station|
|T+00:25:08||Injection into orbit|
|Undisclosed||DSN-1/Superbird-8 satellite separation|
|T+00:33:56||HYLAS-4 satellite separation|