Desenvolvimento de um navegador autônomo, usando GPS, aplicado ao controle autônomo de órbita. / Autonomous orbit navigator development, using GPS, applied to autonomous orbit control.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2001

RESUMO

The appearance of modern global positioning systems motivated the study and development of precise and robust systems for autonomous orbit determination of artificial satellites. These systems maintain, independently from human intervention from the ground, a precise knowledge of the satellite orbital state, through the processing of the information, autonomously generated on-board, by a receiver of the positioning system used. One of the major motivations for the research and development of autonomous navigators, is the availability of real time information about the position and velocity of the satellite, required, for instance, in earth observation missions, for interpretation and analysis of the generated images. The appearance of global positioning systems and the consequent development of autonomous navigators, by making available onboard space vehicles, updated orbit estimations, with good accuracy level, made feasible the research and development of orbit autonomous control procedures. It allowed the orbital maneuvers execution process to be performed in a way totally independent from ground human intervention. Whereas the satellite attitude control reached a high level of autonomy, due to the fact that the attitude measurements are, in general, naturally generated on-board the spacecraft, the orbit control is still now almost totally planned and executed from ground commanded actions. The proposed work consists of the study, development, simulation and analysis of a simplified navigator coupled to an autonomous orbit control system, applied to the China-Brazil Earth Resources Satellites (CBERS). At first, an autonomous orbit determination procedure is developed and analyzed. Its objective is to improve the coarse geometric solution provided by Global Positioning System (GPS) receivers. This will be done by directly using this solution as input (observation) for a real time Kalman filtering process. The orbital state vector will be extended in order to include the systematic error imposed to the GPS geometric solution due to changes in the set of satellites which are visible to the receiver. The improved outputs of this process will then be used in the implementation of an autonomous control system for the Longitude Phase Drift of the spacecraft orbit (parameter which presents the higher frequency of corrective maneuvers application for heliosynchronous orbits in phase with the earth?s rotation, as is the case for the CBERS serie satellites. Finally, the performance of the proposed autonomous control procedure will be analyzed and comparated with the other results achieved by autonomous control systems previously studied at Instituto Nacional de Pesquisas Espaciais (INPE), that directly use the coarse GPS navigation solution.

ASSUNTO(S)

engenharia e tecnologia espacial orientação de satélite controle automático de vôo navegação espacial orbit determination cbers low earth orbits global positioning system automatic fligh control autonomous navigation determinação de orbita sistema de posicionamento global solar orbits navegação autônoma Órbita baixa terrestre engineering and space technology space navigation Órbitas heliosíncronas satellite guidance

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