Research On The Designment Of Chinese Space VLBI System And Computation Simulation

The unique radio astronomical technique of Space Very Long Baseline Interferometry (SVLBI) is an extension of the ground-based VLBI into the space. It has some important potential applications in geodesy and geodynamics, including the definition, practical realization, and the interconnection of different reference frames, determining the geocentric positions of VLBI stations, estimation of the gravity field of the Earth, and satellite orbit determination using the delay and delay rate observables. With the launching of the first SVLBI satellite of the VLBI Space Observatory Program (VSOP) of Japan, in February 1997, this technique has become a reality. An international team of scientists, working under the auspices of the F?MI Satellite Geodesy Observatory, Hungary, has designed the GEDEX, for the purpose of exploring the feasibility of the geodetic applications of SVLBI. However, several major problems also exist. As a result, the current realization of SVLBI cannot be considered as an'extension'to the traditional ground-based geodetic VLBI, as was often assumed in the early studies (Fejes et al. 1996, and references therein). In other words, although the space baselines are indeed added to the interferometer network, on the other hand, some crucial features are missing because the VSOP mission is designed for astrophysical (radio imaging) purposes. It is not suitable for geodetic and geodynamic study, which requires a regular shape, small area-to-mass ratio, precise tracking capabilities resulting in cm orbit accuracy, negligible slew times and long operational life (10-15 years). But the shape of VSOP satellite is quite irregular, with a large a/m and a short operational life (5 years). The orbit determination of HALCA is accurate to 2-5 m (Frey 2002), and it is quite difficult to be accurate to 10 cm. Also, VSOP cannot frequently change observing object, hence it cannot supply more observations to many quasars, which are required for geodesy and geodynamics. Besides, VSOP terminated operation on Nov. 30, 2005. Hence, a new space VLBI satellite is needed to support geodetic and geodynamic study.At present, there is no dedicated research thesis on the design of geodetic and geodynamic space VLBI, hence this investigation studies and summarizes the geodetic requirements of space VLBI satellite. The result of GEDEX indicates that the orbit determination precision of space VLBI satellite is one of the main problems for geodetic study, therefore this investigation studies several technologies which possibly will be able to determine the orbit of space VLBI satellite. And then, according to the kind of satellite and the requirements for geodetic and astrometric study and the geometry of GNSS (GPS, GALILEO) satellite to track the space VLBI satellite, the six Keplerian elements of Chinese space VLBI satellite (TEST-SVLBI) are selected and determined. According to the space and deep space detection plan of China, the realization of Chinese satellite surveying and control network are studied. A program is designed to analyze the coverage area of the space of different heights by the stations of the network, with...