Ariane 5 ECA delivered two communication satellites during VA231 mission

Arianespace conducted successfully another launch of their Ariane 5 ECA rocket. It delivered to GTO orbit two communication satellites with total weight of over 9500 kg (10663 kg including payload adapters) after 35 minutes of flight.

It was 8th mission by Arianespace and 5th launch of Ariane 5 in 2016. Originally launch was planned for October 5, but due the strong wind around launch tower, Arianespace decided to postpone launch for 24 hours. Finally weather was evaluated as favorable for launch and eight minutes before T=0 set for 20:30 GMT; rocket and the payload were ready to enter last phase of launch sequence. At T-7' onboard computer of the Ariane 5 started countdown and five minutes later  fuel tanks reached flight pressure level. Last check of the Ariane 5 systems gave positive results and rocket was ready for its mission.

Punctually at 20:32 GMT rocket started to lift off over ELA-3 complex at Guiana Space Center. Ariane 5 ECA configuration assumes utilization of two solid rocket boosters (EAB); each one is long for 36 m with diameter at 3.05 m what makes them longer than first stage of the rocket, which is long for 30.5 m (with diameter at 5.4 m). During first phase of flight boosters along with first stage are generating over 7000 kN of thrust. Boosters were separated after one minute of flight at T+1'; at T+3'30 nose cone was jettisoned and both satellites installed on ACU payload adaptor were exposed. It is worth to remind, that satellites were installed one over another, with Sky Muster-2 (known also as NBN-Co-1B) over GSAT-18 using special structure called SYLDA-5. Next key point of flight was cutting off main Vulcain-2 engine at T+9'15", which stopped providing 1390 kN of thrust. This allowed rocket to jettison first stage and start its HM7B upper stage engine fueled with liquid oxygen and hydrogen. Second stage weighing 4540 kg and long for 5.4 m with diameter at 4.7 m begun its autonomous flight. Two minutes later rocket was tracked for the first time by Natal tracking station in Brazil after leaving range of Galliot tracking station in French Guiana. Rocket reached at that point altitude of 150 km and speed of around 24000 km/h. At T+25'20" upper stage switched off its engine after reaching orbit of 250 km x 35786 km with inclination at 6°. Four minutes later Sky Muster-2 was deployed successfully and SYLDA-5 adapter was partially jettisoned at T+31' to expose GSAT-18.  GSAT-18 was deployed at T+34' at 21:03 GMT. VA231 was finished with success!

GSAT-18 and Sky Muster-2 are both communication satellites. GSAT-18 was designed and manufactured by ISRO (Indian space agency) for Digital Satellite News Gathering (DSNG) and VSAT services along with supporting satellite television and telecommunication over India. I-3K bus provides 6000 W of power for transponders operating on  C band (24), Upper C band (12), Ku band (12) and two transmitters working also on Ku band.  Weight of the satellite is 3404 kg with following dimensions: 3.1 m x 1.7 m x 2 m. It is powered with two deployable solar arrays and onboard batteries and it will remain on 74° E orbital slot for at least 12 years. Sky Muster-2 is based on SSL-1300 bus communication satellite and was made by SSL. It will be operated by NBN Co Limited and will provide broadband internet access over Australian Interior via 202 onboard Ka band transponders. Powered by two deployable solar arrays and onboard batteries (with output after 15 years at 16.4 kW), satellite weighs 6404 kg with following dimensions: 8.5 m x 3.5 m x 3 m.  Satellite will spent on orbit at least 15 years. It will use its twin ion thrusters and 3 axis attitude control system to change position from 135° E to 150° E.

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