النتائج (
العربية) 1:
[نسخ]نسخ!
board. These libraries may include facilities for hardware initialisation, interrupthandling, hardware clock and timer management.DesignOperating system can be designed as a monolithic (one piece of software withmany interacting modules), layered or client-server structure. A minimal kernel and aset of server and client tasks, makes it a lot easier for the vendor to offer a scalableoperating system with more or less services. Scalability means that a set of servicesused by an application can be optimised, and is even more useful if there is apossibility of dynamic downloading and uploading of services. On the other hand,configurability is a capacity of a RTOS to accommodate changes in underlyinghardware (e.g. location and migration transparency).The space application is a system for guidance, navigation and control ofautonomous spacecraft with critical phases. For example, the Rosetta spacecraft willhave a number of phases when real-time control from ground will not be feasible.Additionally, the software must function in an environment which is highlyconstrained in both the memory space and processor power (e.g., the distance fromthe Sun limits the amount of power available from the solar panels and equipmentneeds to be powered down). Hence the need for configurability and componentoptimisation in critical phases.Space missions require long-term maintenance and support. For somemissions, it is very important to have the ability to upgrade code after spacecraftlaunch in order to correct bugs found during the operation phase, to makemodifications due to changes in the environment requirements, and to improve certainfunctions.StandardsThe space domain covers a lot of very different applications from ground segments,launchers and satellites to probes. However, majority of applications is builtaccording to two main standards: ECSS and DO-178B. The development of allsoftware under the umbrella of European Space Agency (ESA) has to be done inaccordance with the European Cooperation for Space Standardisation (ECSS) spaceproduct assurance standards (ECSS96) which have recently replaced the qualitystandard ESA PSS-05. These standards are mainly focused on the software processrather than on the product and, not surprisingly, COTS RTOS vendors have largelyignored them. This is not the case with DO-178B (RTCA92), internationallyrecognised assurance standard for software development within the aerospaceindustry. As all new space projects will be facing the DO-178B certification process,some RTOS vendors have already made products addressing the standard’srequirements.An RTOS needs to interact with application components and its environment throughwell-defined interfaces. With the technology being in a constant state of flux, it seemsreasonable to choose RTOS conforming to a widely accepted interface standard.RTOS conformance to the POSIX 1003.1 standard was chosen as a major criterion forthe selection of COTS RTOS in the GUARDS project implemented in a space domain(Powell01).
يجري ترجمتها، يرجى الانتظار ..