On October 23 at 02:30 UTC, an Ariane 5 ECA successfully launched the SES 17 and Syracuse 4A satellites into subsynchronous geostationary transfer orbit from pad ELA-3 at the Guiana Space Center in Kourou, French Guiana.

This particular Ariane 5 launch was a bit different than your standard Ariane 5 launch. This launch carried more mass into orbit than any previous Ariane 5 launch – a whopping 11,210 kilograms. Both SES-17 and Syracuse 4A are massive satellites, having a combined mass of 10,263 kilograms. (The remaining 947 kilograms is the dual launch adapter and other components such as the separation mechanisms.) To accommodate this bigger payload, the standard Ariane 5 fairing was swapped out for one that was exactly 1.5 meters longer.

As satellites launched on Ariane 5 go, SES-17 and Syracuse 4A are pretty pedestrian. SES-17 will provide maritime and aviation communications over the Atlantic Ocean and the Americas. It will do this with the first fully digital payload on an SES satellite, which will allow it to dynamically change coverage from area to area depending on demand.

Syracuse 4A was built for the French military and will allow the nation to communicate securely (and jam-free!) with its armed forces around the world, including moving aircraft, ships, and ground vehicles. It is the first of three satellites in a new constellation of French military communications satellites.

This was the last launch of Ariane 5 before it will be entrusted to send NASA’s James Webb Space Telescope towards Sun-Earth Lagrange Point 2, beginning its “six months of terror”. Once the space telescope reaches its destination, it will begin the process of unfurling the spacecraft’s sunshade with its hundreds of single-point failure components and unfolding the massive honeycomb mirror — all before calibrating its instruments prior to its first light. 

The ESA signed on back in 2007 to provide an instrument on the spacecraft and the launch of the telescope at no cost to NASA in exchange for 15% of all observation time and fifteen astronomers on the science support staff.  With the success of this flight, some of the pressure is off of the initial half-hour of JWST’s flight.

More Information

PDF: Arianespace launch kit

Europe’s Contributions to the JWST Mission (ESA)

Launch video