Bypass as an attribute of unmanned spacecraft operability in anomalous flight situations

The bypass factor as the basis for providing Earth remote sensing spacecraft (ERS SC) operability in anomalous flight conditions, related with onboard equipment (OE) faults, is discussed in the paper. In addition, operability as a complex property is decomposed into three particular characteristics: invulnerability, adaptability, and recoverability. Principles of their implementation during the flight are based not only on structural provisions (for example, protective measures), but also on OE technical state control not only by integrated structural reserves, but also by bypasses based on other resources. Provision of ERS SC operability and target operation with the use of minimum additional resources is the purpose of bypass control in anomalous flight situations. It is based mainly on roundabout ways of accomplishing tasks, in other  words, on bypasses produced on the basis of functional, information-analytic, and natural resources (intrinsic to OE) as well as emergent (synergetic) resources formed as a result of purposeful interaction of dissimilar components, in particular, the complex of the SC onboard equipment. The topicality of this problem increases with the decrease of ERS SC weight-dimension characteristics (caused by tightening the restrictions) and the increase of active life duration (Tаl) under relatively strict requirements of efficiency target (ET). Variants of using available OE redundancies for ERS SC bypass flight control, taking into account the change of ET within the set limits, are proposed in the paper. Schemes of numerical estimation of efficiency and operability as vector parameters on the basis of bypasses including those based on parameters and criteria of SC operability are presented. A possibility of forming requirements to onboard equipment to ensure SC operability in anomalous flight conditions with their help is shown.