The paper centers on the problems of developing failure- and fault-tolerant systems for Earth remote sensing satellite constellation control. The study defines the concept of a complex that fail-safely performs a target task, in this case, the task of detecting a target event and monitoring its behavior and development, i.e. monitoring the target event, and gives a hierarchical satellite constellation structure. Findings of the research show that it is necessary to use dynamic redundancy, which can significantly increase the trajectory of self-controlled degradation and, accordingly, the satellite constellation active life. The complexity of the problem lies in ensuring the reliability of the results obtained when a large number of target events, both natural and man-caused, occur. The study introduces an approach to reduce hardware redundancy, i.e. monitor a larger number of events using a lower power satellite constellation, and proves that is possible to use the approach without losing the system reliability.

For the most general, so-called byzantine, failures that lie in an arbitrary, "malevolent" behavior of the faulty computer, a method of distributed system diagnosis was proposed. It is applicable to the partially connected multicomputer systems featuring certain structural characteristics and enables the system to detect and identify the manifested failures on its own without an outside aid.

Consideration was given to the multipath information transmission in the multilevel computer systems from one or more first-level computers to several last-level computers with the aim of improving reliability of information transmission. It was assumed that (i) at each system level known are system structure, information paths, and permissible number of faulty computers and (ii) there exists at least one path through-passing good computers. It was assumed in Part I that the valid values of the information received by all last-level computers are traceable. For these conditions, proposed was a method of determining each feasible variant of the valid value of the source information sent from the first-level computers with indication of each possible combination of admissible byzantine system faults under which this variant may occur. Conditions for which a subsystem consisting of the last-level computers can independently perform the functional self-diagnosis of information transmission in the system were established in Part II, and a method of self-diagnosis was proposed which determines each feasible variant of the initial information sent from different first-level computers with indication of each possible combination of the admissible byzantine system faults for which in the good last-level computers the true results of transmission under this variant of values may be generated.

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The paper examines issues of introducing the distributed computational technologies in constructing the fail-safe and fault-tolerant control systems for spacecraft constellations of various purposes. Various target objectives require various tools to achieve the task. Comparative analysis of the existing distributed computational technologies operating with the responsive application systems was performed including the spacecraft constellation control systems, to identify the most acceptable solutions. Principles of constructing the network-centric systems in controlling the spacecraft constellations were considered. Distributed computational technologies were analyzed not only from the point of view of solving the target problems by the spacecraft constellations, but also from the point of view of ensuring their reliability, as well as in organizing the spacecraft constellation control systems.