(For the trade union, see Confederation of Cameroon Trade Unions) CSTS (Crew Space Transportation System) or ACTS (Advanced Crew Transportation System) is a human spaceflight system proposal. It was originally a joint project between the European Space Agency (ESA) and the Russian Space Agency (FKA), but is now solely an ESA project. It aims to design a spacecraft for low Earth orbit operations such as servicing the International Space Station but also capable of exploration of the Moon and beyond. This study was conceived as a basic strategic plan to keep a viable European human space program alive because NASA officials had announced that NASA's Vision for Space Exploration Orion spacecraft, subsequently cancelled, would be developed without participation of international partners.