This Standard specifies the requirements applicable to the concept definition, design, analysis, development, production, test verification and inorbit operation of space mechanisms on spacecraft and payloads in order to meet the mission performance requirements. This version of the standard has not been produced with the objective to cover also the requirements for mechanisms on launchers. Applicability of the requirements contained in this current version of the standard to launcher mechanisms is a decision left to the individual launcher project. Requirements in this Standard are defined in terms of what shall be accomplished, rather than in terms of how to organise and perform the necessary work. This allows existing organizational structures and methods to be applied where they are effective, and for the structures and methods to evolve as necessary without rewriting the standards. Complementary non-ECSS handbooks and guidelines exist to support mechanism design. This standard may be tailored for the specific characteristic and constrains of a space project in conformance with ECSS-S-ST-00.