| dc.description.abstract | This work consists in validation by model and simulation of the Fault Tolerant Attitude Determination System (SDATF), to be tested in terrestrial low orbit as payload of the scientific satellite NanosatC-Br2. This satellite is being developed by the National Institute for Space Research (INPE) in collaboration with Santa Maria Federal University, and its objectives are, besides the associated technology consolidation in Brazil, sendingscientific experiments to space environment. Due to large exposure of the circuits to radiation in orbit, the attitude determination system used in a satellite shall be robust to bit flips caused by this exposure, phenomena denoted as Single Event Effect (SEE). When a SEE affects a memory cell, corrupting the stored information, it is said that a Single Event Upset (SEU) occurred. SDATF, therefore, is proposed to provide informationabout the attitude to satellites onboard computer by means of a SEU fault tolerant solution. Preliminary efforts were already made with the purpose of validating SDATF, but a more flexible and rework reducing validation method is necessary due to possible system improvements and requirements changes along project lifecycle. Although validationby model and simulation meets this necessity, a sistematic procedure to build a realistic model shall be established, since features like task scheduling, parallel operation and non determinism make an unambiguous formal description of the system a complextask. The work that follows presents a procedure for modelling and simulation of SEU like fault tolerant systems, instantiating this method with SDATF. Along this work, concepts related to the effects of high energy particles on integrated circuits in the space environment, their causes and ways of mitigation are covered. The necessary formalismfor modelling the system is presented, as well as the experiments with simulated fault injection and the results that endorse the validity of the system proposed. | |
