the rocket in hot and humid conditions. Soyuz-2.1a The 2.1a version includes conversion from analog to digital flight control system and uprated engines on the booster and the first stage with improved injection systems. The new digital flight control and telemetry systems allow the rocket to launch from a fixed rather than angled launch platform and adjust its heading in flight. A digital control system also enables the launch of larger commercial satellites with wider and longer payload fairings such as the ST-type fairing. These fairings introduce too much aerodynamic instability for the old analog system to handle. This stage continues to use the RD-0110 engine. The 2.1a/ST version is sometimes called Soyuz ST-A. The first launch, from Guiana, (17 December 2011 for Pléiades-HR 1A, SSOT, ELISA (4 satellites)) was a success. Soyuz-2.1b The 2.1b version adds an upgraded engine (RD-0124) which greatly increases the specific impulse of the upper stage (326 seconds to 359 seconds), and hence improves payload capability from 7 tonnes to 8.2 tonnes. First launch took place from Plesetsk Cosmodrome Site 43 on 26 July 2008 with a classified military payload. The 2.1b/ST version is sometimes called Soyuz ST-B. The first launch, from Centre Spatial Guyanais, was a success (21 October 2011), for the first two Galileo IOV satellites. Soyuz-2.1v The first flight vehicle of the 2.1v version was finished in 2009. It is a "light" version of the Soyuz-2 without the side boosters (blocks B, V, G and D ). The Block A engine was replaced by the more powerful NK-33-1, which , was to eventually be replaced with the RD-193. The new launcher version was able to deliver up to 2.8 tonnes in low Earth orbit. Modifications for various launch sites The Soyuz-2.1a/1b versions launched from the Vostochny Cosmodrome and the Centre Spatial Guyanais have a series of modifications over the stock units. Some of these might later be implemented on all the Soyuz-2, while some are particular requirements to the space port design. Modifications for the Centre Spatial Guyanais (CSG) version includes: First use of a mobile service tower at the ELS that enabled vertical payload integration. European supplied payload adapters. European supplied KSE (), a system to locate and transmit a flight termination signal. It would activate the engine shutdown command and leave the vehicle in a ballistic trajectory. Adaptation of the S-Band telemetry system on all stages from the 5 TM