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The increasing use of Global Navigation Satellite Systems-GNSS in future Aeronautical Navigation Systems-ANS is a current trend in the aeronautical operation and regulation communities. This trend implies the adoption of elements and interactions of a degree of complexity that is still being discussed around the world. Faced with that, we believe that a requirements based approach is an effective tool to deal with such highly complex and integrated systems. In this work we discuss a requirements based approach to future Aeronautical Navigation Systems based on Global Navigation Satellite Systems. To do that, we first briefly present the concept of Communication, Navigation, Surveillance/Air Traffic Management - CNS/ATM, and the current and potential benefits of the adoption of its paradigms.

The aerospace and automotive electronic systems are getting more complex and/or highly integrated, as defined by ARP 4754A, making extensive use of microelectronics and digital memories which, in turn, operates in higher frequencies and lower voltages. In addition, the aircraft are flying in higher altitudes, and polar routes are getting more frequent. These factors raise the probability of occurrence of hazardous effects like the Single Event Upsets in their embedded electronic systems. These must be designed in a way to tolerate and assure the immunity to the Single Event Upsets, based upon criteria such as reliability, availability and criticality. This paper proposes an overview of an assurance process of immunity of embedded electronic systems to Single Event Upsets caused by ionizing particles by means of a review of literature and an analysis of standards as ECSS-E-ST-10-1, NASA Single Event Effects Criticality Analysis and IEC TS 62396-1.

Currently, the use of Global Navigation Satellite Systems-GNSS has been widely disseminated for the most different applications, from the aeronautical navigation to the car traffic, being the Global Positioning System-GPS the most used system for such objectives. New applications have presented challenges in terms of the main requirements associated to such systems, namely: precision, reliability, availability, continuity and integrity. It is because proposed solutions, such as satellite or ground-based augmentation systems, depend on signals provided by the GNSS satellite constellation. It constitutes a limitation for using such systems for position and velocity estimations. On other hand, Inertial Navigation Systems-INS, being independent of external signals, have a big potential to be applied on these circumstances; furthermore, they present characteristics that may be considered complementary to the GNSS.

Currently, the use of Global Navigation Satellite Systems-GNSS has been widely disseminated for the most different applications, from the aeronautical navigation to the car traffic system, being the Global Positioning System-GPS the most used system for such objectives. New applications of such systems have presented more demanding requirements in terms of precision for the position and velocity provided by these systems. Some solutions, as the precision augmentation systems based on satellite or ground improve the precision of the position and velocity estimates. However, the sampling rate of these systems is not substantially improved. Therefore, it constitutes a major limitation of such systems for the position and velocity estimates during high acceleration transients. On other hand, Inertial Navigation Systems- INSs present superior performance under these circumstances.

Avionics Systems are increasingly used to perform safety-critical functions at high altitudes. But their increasing capacity and concentration of memory and logics leads to more frequent occurrences of single event upsets, especially in high altitudes. In this work we discuss the process of eliciting and validating requirements to handle single events upsets in avionic systems. To do that we initially summarize and update the concepts of radiation environment of the atmosphere, radiation induced errors, single event upsets, etc. presented in a previous paper. Then, we discuss some of their effects on avionic systems and ways of mitigation, reported in the literature. Finally, we discuss provisions to demand the adoption of such mitigation measures, and their sufficiency by transforming them into requirements, according to recommendations of compliance described in standards as SAE ARP 4754A and RTCA DO-254.