The Ensemble de Lancement Soyouz (ELS) (in English; Soyuz Launch Complex), is a launch complex at the Guiana Space Centre in Kourou/Sinnamary, French Guiana. It is used by Soyuz-ST rockets; modified versions of the Soyuz-2 optimised for launch from Kourou.
The first launch to use the complex occurred on 21 October 2011, when a Soyuz ST-B launched the first two Galileo IOV-1 & IOV-2 spacecraft.
The location of the launch site allows a greater mass of payload to be placed into geosynchronous transfer orbit compared to existing Soyuz launch facilities at the Baikonur Cosmodrome in Kazakhstan.
ELS is fifteen kilometres northwest of the launch facilities used by Ariane rockets.
It consists of a single launch pad, with a horizontal assembly and processing facility, or MIK, located 700 metres away. As with the Soyuz launch complexes at Baikonur and Plesetsk, the pad is connected to the MIK by means of a railway, which the rocket is rolled along prior to erection at the pad.
Unlike other Soyuz launch complexes, a Mobile Service Tower is present on the complex, and the payload is installed in the vertical position instead of the horizontal.
It also differs in having a fixed launch mount, rather than one which can be rotated, meaning that the rocket may need to execute a roll manoeuvre during its ascent to orbit. Earlier R-7 rockets were incapable of rolling, so their launch complexes were built to allow launch azimuth to be adjusted before launch.
Read more about Ensemble De Lancement Soyouz: Launch History, See Also