General description of avionics architecture

According to the preliminary choices made, the avionics architecture of the Ariane 5 launcher retains a duplex system, based on two electric channels, physically and geographically independent and segregated. 

The duplex architecture is centralized around the mission computer (OBC -OBC) itself redundant, and is based on two independent channels, each connected to both OBCs by a MIL-STD-1553B [MIL 78] bus. Each electrical channel is independent of the other channel and connected to a single MIL-STD-1553B bus. 

Furthermore, each of the nominal and redundant OBCs is connected to two 1553 buses. The OBC master, unique at any given moment, simultaneously manages both the electrical channel buses, and thus the related equipment for both channels. 

The redundant architecture is centralized around the OBC, manager of the two 1553 buses that, based on acquisitions made on both channels, then identifies the failing equipment - via word of their condition or of inconsistent data received - and causes their retirement if necessary. 

Most of the equipment is located in the equipment bay of the Atiane lanneher, but equipment is distributed at various stages of the launcher. The topology of the avionics of the launcher ean thus be represented. 

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