# Fault Diagnosis and Prognosis of Satellites and Unmanned Aerial Vehicles: A Review
## 3 Review Methodology
Different criteria tables were also curated through the reviewing process with a summary table outlining the focus of each in Table 1, under Tables 2-8, that outlined the pros and cons of different categories of work, as well as the finer details of their research. This was performed to provide the reader with a comprehensive overview of the important strong suits and weaknesses of the works and their assumptions for ease in reimplementing and reproducing them in the future. At times, some details we thought would be useful for reproducing or enhancing the existing works were left out in their respective manuscripts or not greatly and definitively expanded on. In such cases, we left those specifications blank in our tables. The layout of the criteria tables also proved to be greatly helpful in determining whether a scientific work is relevant to our review's scope. There is a need to further elaborate on the advantages and disadvantages provided in Tables 2-4. An advantage or pro was defined as a feature that served to solve a persisting problem in the area or gave the proposed strategy an edge over its competitors to be applied in real life. Conversely, a disadvantage or con was defined as an inherent shortcoming that deterred their implementation in real-life applications. The most commonly identified advantage across the works was their capability to be applied to more than only fault detection, isolation, identification, estimation, prognosis, etc. In contrast, the most prominent disadvantage was observed to be the computational burden of the proposed strategies. Generally, the more fault diagnosis modes a strategy can support, the better they are at being suited for more real-life problems. However, higher generalizability often comes with higher computational intensity, making them less suitable for solving other problems requiring less consideration. Therefore, many of the strengths and limitations listed in Tables 2-4 are due to their respective works' problem statements or focus. Even so, there are other types of strengths and limitations that are specific to each study's methodology, such as their assumptions, which should not be neglected if one decides to adopt them in real life. The summary and strengths and limitations tables also aim to provide a bite-sized summary of each work that facilitates the study of this review by readers. The defining criteria and key characteristics have been compiled in Tables 5-8. Table 5 contains the works on single-agent fault diagnosis with the criteria being focused on diagnosis mode, the specific approach, the strategies' application, the fault types considered, and the measurement parameters that are used for monitoring. The diagnosis mode is imperative since it is one of the deciding factors as to whether a strategy is applicable to a problem or not. The strategies' application was included as a criterion to highlight the areas where they have been employed and which applications they have not been utilized in yet. This serves to reduce the risk of oversight on the researchers' part in failing to consider all the possible solutions for a specific application. The fault type details are also extremely useful since different types might need dissimilar monitoring methods or some are more prevalent in certain applications which helps in identifying which works are beneficial in addressing a condition monitoring problem. The studied measurement outputs are also compiled to highlight what information is needed from a system for the readers to be able to incorporate the methodologies in this review into their desired systems. Table 6 includes the works on single-agent fault prognosis with its focus being on the same criteria. Moving on, Table 7 consists of diagnosis studies on multiagent systems with their main criteria being the type of diagnosis, approach, application, and fault type. In the field of multiagent fault diagnosis, there is more focus placed on the relationship between satellites and UAVs.