An Improved Redundancy Scheme for the Optimal Utilization of Onboard Computers

• The onboard computer systems used in satellite launch vehicles have stringent timing requirements due the mission critical nature of their tasks. The complete control of launch vehicles is done by onboard computers (OBC) which relate to the navigation guidance, all prelaunch operations and generation of mission critical events. A fault in these systems could lead to a mission failure and catastrophic consequences. Various redundancy schemes are built into such mission critical applications to ensure the overall success of the missions. Typically a dual redundant scheme with active hot standby system has been employed in Indian Satellite launch vehicles which have been found to be very satisfactory so far. The past two decades of flight experience shows very reliable performance of the primary computers and almost no incidences demanding any serious usage of the standby computer during launches. In this paper we propose a new approach to use the standby computer to optimize the onboard computing resources which allow more slack time for further computation requirements. The slack time thus acquired can effectively be used for ‘utility enhancing computations’, such as faster control loops or specialised guidance computations. We also present a system level algorithm which depicts the overall allocation and scheduling of tasks. The proposed scheme enables an optimised usage of system resources.

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