**4.1 Interface design and practical design challenges**

The interfaces between satellite subsystem components can be SW, HW or MW interfaces. The design and build of these interfaces are well incorporated into any satellite subsystem components "Design Product" and associated "Design Process".

The Design Product includes System Architecture, Interface Product, Independent Verification and Validation (IV&V) Test Plan, Schedule, Design Approach, Acceptance Criteria, and System-Built Product.

For MOSA, the Design Process is expected to incorporate MOSA into: Architecture Process, Interface Management, IV&V Process, and System Engineering and Integration (SE&I) Process. The Interface Product and its open interface design using MOSA along with the Interface Management are the key challenges in the development of open-and-modular satellite systems. The key design challenges for the design and build of open-and-modular satellite systems are:


**Figure 8.** *MOSA and U.S. NOA approach.*

by the time of Full Operational Capability (FOC) deployment. Section 4.3 discusses DOD guidance for managing key interfaces for military satellite system development.
