ECSS-E-40A, SPACE ENGINEERING: SOFTWARE (13 APR 1999)., This software engineering standard concerns the "Product software", i.e. software that is part of a space system product tree and developed as part of a space project. This standard is applicable to all the elements of a space system, including the space segment, the launch service segment and the ground segment. This standard covers all aspects of space software engineering including requirements definition, design, production, verification and validation, and transfer, operations and maintenance. It defines the scope of the space software engineering process and its interfaces with management and product assurance, which are addressed in the Management (-M) and Product assurance (-Q) branches of the ECSS System, and explains how they apply in the software engineering process.