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Analysis of disturbing effects in the dynamical model of orbit determination using GPS
Paula C P M Pardal, Rodolpho Vilhena de Moraes, Helio Koiti Kuga
Last modified: 2010-05-29
Abstract
The problem of orbit determination consists essentially of estimating parameters values that completely specify the body trajectory in the space, processing a set of information (measurements) from this body. Such observations can be collected through a tracking network on Earth or through sensors.
The Global Positioning System (GPS) is a powerful and low cost means allowing the computation of orbits for artificial Earth satellites. The T/P satellite is an example of using this system for space positioning.
The orbit determination of artificial satellites is a nonlinear problem in which the disturbing forces are not easily modeled, like geopotential and direct solar radiation pressure. Through an onboard GPS receiver it is possible to obtain measurements (pseudo-ranges) that can be used to estimate the state of the orbit.
The main target here is to determine the orbit of an artificial satellite, using signals of the GPS constellation and least squares algorithms as a method of estimation, with the aim of improving the performance of the orbits estimation process and, at the same time, minimizing the procedure computational cost. Perturbations up to high degree and order for the geopotential coefficients, direct solar radiation pressure, and sun-moon gravitational attraction were taken into account. It was also considered the position of the GPS antenna on the satellite body that, lately, consists of the influence of the satellite attitude motion in the orbit determination process. Pseudo-range measurements were corrected from ionospheric effects, although the accuracy on orbit determination is not expressive. An application has been done, using real data from the Topex/Poseidon satellite, whose ephemeris are freely available at Internet. The best accuracy obtained in position is shown for short period (2 hours) and for long period (24 hours) orbit determination. In both cases, the perturbations mentioned before were taken into consideration and the analysis occurred without selective availability on the signals measurements.
The Global Positioning System (GPS) is a powerful and low cost means allowing the computation of orbits for artificial Earth satellites. The T/P satellite is an example of using this system for space positioning.
The orbit determination of artificial satellites is a nonlinear problem in which the disturbing forces are not easily modeled, like geopotential and direct solar radiation pressure. Through an onboard GPS receiver it is possible to obtain measurements (pseudo-ranges) that can be used to estimate the state of the orbit.
The main target here is to determine the orbit of an artificial satellite, using signals of the GPS constellation and least squares algorithms as a method of estimation, with the aim of improving the performance of the orbits estimation process and, at the same time, minimizing the procedure computational cost. Perturbations up to high degree and order for the geopotential coefficients, direct solar radiation pressure, and sun-moon gravitational attraction were taken into account. It was also considered the position of the GPS antenna on the satellite body that, lately, consists of the influence of the satellite attitude motion in the orbit determination process. Pseudo-range measurements were corrected from ionospheric effects, although the accuracy on orbit determination is not expressive. An application has been done, using real data from the Topex/Poseidon satellite, whose ephemeris are freely available at Internet. The best accuracy obtained in position is shown for short period (2 hours) and for long period (24 hours) orbit determination. In both cases, the perturbations mentioned before were taken into consideration and the analysis occurred without selective availability on the signals measurements.