The Soyuz-U launch vehicle is an improved version of the original Soyuz rocket. Soyuz-U is part of the R-7 family of rockets based on the R-7 Semyorka missile. Members of this rocket family were designed by the TsSKB design bureau and constructed at the Progress Factory in Samara, Russia (now a united company, TsSKB-Progress). The first Soyuz-U flight took place on 18 May 1973, carrying as its payload Kosmos 559, a Zenit military surveillance satellite. As of 2016 the rocket is still in service, although production has stopped since April 2015 as part of the transition process to Soyuz-2. The last flight is expected to take place on February 1, 2017, carrying Progress MS-05 to the International Space Station.