STi was approached by APL to conduct a Red Team Review of the Thermosphere Ionsphere Mesosphere Energetics & Dynamics (TIMED) Observatory with NASA. The following three analyses were requested as a part of this review:
Failure Modes Effects and Analysis (FMEA)
Fault Tree Analysis (FTA)
Probabilistic Risk Assessment (PRA)
A detailed analysis report was submitted along with a Red Team Review Report. This analysis uses a quantitative approach for the Hardware failure and a qualitative approach for the Mission failure. For instance, a qualitative fault tree is developed for mission failure top event as in the Figure 1, and the quantitative fault tree is integrated for hardware failure top event as in the Figure 2.
FTA is used to perform the PRA for the TIMED spacecraft. The Event Tree also is established. The selection of initiating events is critical, as is the determination of end states. Focusing on specific end states allows the event tree to be simplified. The Figure 3 below illustrates the event tree of AIU Relay Defect.