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Descripción
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| Recent gravity field determination missions have shown the possibility of improving our Earth knowledge from space. GRACE has helped to the determination of temporal variations of the field while GOCE has improved the precision in the determination of lower degrees of the gravity field. But there is still a certain number of needs for geophysics that these missions have not furnished. Perpetuity of the observations and temporal variations of lower degrees of the gravity field are areas where improvements must be done. These improvements can be achieved thanks to new measurement technologies with higher precision, but also using new observables. Historically, geodesy has used laser ranging from ground stations, and onboard gradiometry. More recently, GRACE mission has introduced the use of satellite-to-satellite ranging. Authors consider that alternative technologies should be investigated, and that formation flying should be largely explored, not only for follower-leader strategies. This work is done in this paper. The authors have explored the possibilities of tethers and formation flying for the determination of the gravity field. The method used for this study is the so-called lumped coefficients. Lumped coefficients present several advantages with respect other analysis methods. The most important is the no need of data for analysis of results precision. The inversion of covariance matrix enables direct study with no data. Lumped coefficients are used for the determination of measurement error propagation, and for the determination of optimal mission parameters. This method is used in tethered systems, in formation flying, and in gradiometry, for comparison purposes. Tethers appear as a very long base gradiometers, with very interesting properties, but also very challenging from a technological point of view. One of the major advantages of the tethered systems is their multitask design. It is, the same cable can be used for propulsion purposes in some phases of the mission, and for geodesy purposes in other phases. Several studies have been presented using formation flying, but any of them is exhaustive in terms of number of satellites, configuration, and plan of the motion. We study formation flying using differential orbital elements. The advantage of this representation is the possibility of study all sort of initial conditions and reference orbit with a posterior analysis of lumped coefficients. Obtained results show the intrinsic possibilities of these two systems, their comparison with respect to precedent ones and the conditions when their use is interesting. We also have defined some baseline scenarios for future missions. | |
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Internacional
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Si |
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Lugar
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Grasse, Francia |
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Tipo
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Miembros en el extranjero |
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Fecha inicio
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01/07/2007 |
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Fecha fin
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20/12/2007 |