9.3 General Design Process

Modified from Dr. Daniel Selva’s lecture slides

1. Allocate mission and system requirements

• • Establish functional requirements of the avionics system based on mission phases, payload requirements, and spacecraft bus requirements, see Typical Requirements and Design Considerations
  • Evaluate candidate architectures: select potential avionics components, see Typical Avionics
  • Partition by function: develop block diagrams to make sure you meet your functional requirements, see Integrated Computer
  • Determine feasibility: weigh risk vs capabilities of candidate architectures, see Avionics Reliability and Fault Tolerance
  • Develop non-intrusive testing methodologies: “black box” testing, see System Integration and Testing chapter

2. Define the computer system’s operational modes and states, see Flight Software Modes

• • Develop state diagram consistent with functional requirements
  • Define power cycle and duty cycle for low level computer and high level
  • Model different operational stages as different states
  • Ensure degradation/failure states are modeled
  • Consider effects on ground/ops for all states

3. Functionally partition and allocate the computational requirements, see Typical Requirements and Design Considerations

• • Consider the following areas to allocate functions:
    • Space or ground, payload, spacecraft bus (avionics, other subsystems)
    • Distinguish between hardware and software requirements

4. Evaluate internal and external interfaces, see the I/O interface section

• • Determine Input/Output requirements for the avionics subsystem with respect to the other subsystems and payload

5. Select the baseline architecture and form the baseline system specification

• • Detailed design specifications
    • i. Sensor list (type, location, number, criticality)
    • ii. Network strategy
    • iii. Estimate of processing throughput
    • iv. Communications bandwidth
  • Select critical components
    • i. Data management units
    • ii. Redundancy strategies
    • iii. Communications frequencies
  • Data budget and profile analysis based on system design, see Data Budget and Profiling section
  • Integration, Assembly, & Testing strategy