Satellite architecture

The rest of the paper is organised as follows Section 2 offers a general overview of UPMSat-2 satellite system. Section 3 presents the general characteristics and duties of the ADCS. Section 4 describes the details of the ADCS hardware. Section 5 presents the software architecture and the tasks schema that motivates the discussion. Section 6 discuses the scheduling analysis. Section 7 presents the validation approach. Finally, section 8 presents the conclusions of the analysis and some ideas for future work. 

In this paper, we propose and investigate formal concepts that aim to overcome this bias. They support the construction of FMEA tables solely based on the system model and the failure modes, i.e., without requiring the set of effects as input. More concretely, given a system specification in the Architecture Analysis and Design Language (AADL), we show how to derive relations that characterize the effects of failures based on the state transition system of that specification. We also demonstrate the benefits and limitations of these concepts on a satellite case study. 

In this chapter, we focus on the solutions implemented in space systems, in terms of onboard computer (OBC) system architecture regarding the needs and constraints of dependability. After presenting the background and the different types of systems involved, we clarify the regulatory framework and the needs and constraints of dependability. We then describe architectural solutions covering three main areas of space systems (launchers, satellites, and orbital transport vehicles). Finally, we propose a sitmmary of the different system types, needs and solutions. 

The telecommand function is particularly important because its loss generally leads in the short-term to total loss of the satellite. It is therefore subject to an architecture in hot redundancy (first degree). Telecommands are received, processed and transmitted to the computer by two independent entities. However, this is not a... 

Figure 7.23. Avionic architecture - example of a telecommunications satellite...

By employing the automatic procedures onboard, the FDIR exploits the possibihties offered by the architecture for achieving the dependability goals. The definition of FDIR is a compromise between the needs for autonomy and availabihty, and the requirements for reliability (lifespan) and safety, even though these safety requirements are low for satellites. 

Although the missions and their eonstraints are different from those of satellites, the architeetural solutions are often very similar, even if the architecture is typically more integrated with a weaker distinction between a specific platform part and a specific payload part (even if only because of stronger interactions between the mission or the management of the instruments and functions such as attitude and oibit control). 

The supervision and coordination of the chair s movements are made through a close loop architecture based on a satellite camera of the environment. 

The dectrical architecture is standard for a space e eriment. It is organized around a 16 bit 80C86 microprocessor, powered by hybrid DC/DC converters using the satellite 28 volt power line. Redundancy is obtained by mounting two independent microprocessor units and DC/DC units which can be sdected by external switches. 

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