Atmospheric drag is the main source of error in the determination and prediction of the orbit of low Earth orbit （LEO） satellites; however, empirical models that are used to account for this often have density error...Atmospheric drag is the main source of error in the determination and prediction of the orbit of low Earth orbit （LEO） satellites; however, empirical models that are used to account for this often have density errors of around 15%-30%. Atmospheric density determination has thus become an important topic for researchers. Based on the relationship between file atmospheric drag force and the decay of the semi-major axis of the orbit, we derived atmospheric density along the trajectory of challenging mini-satellite payload （CHAMP） satellite with its rapid science orbit （RSO） data. Three primary parameters--the ratio of cross-sectional area to mass, the drag coefficient, and the decay of the semi-major axis caused by atmospheric drag--were calculated. We also analyse the source of the error and made a comparison between the GPS-derived and reference density. The result for December 2, 2008, showed that the mean error of the GPS-derived density could be decreased from 29.21% to 9.20%, if the time span adopted for the process of computation was increased from 10 min to 50 min. The result for the entire month of December indicated that a density precision of 10% could be achieved, when the time span meets the condition that the amplitude of the decay of the semi-major axis is much greater than its standard deviation.展开更多
1 Scope This standard specifies the definition, prineiple, apparatus and materials, procedure, expression of resuits and test report of determination of bulk density, apparent porosity and true porosity of dense shap...1 Scope This standard specifies the definition, prineiple, apparatus and materials, procedure, expression of resuits and test report of determination of bulk density, apparent porosity and true porosity of dense shaped refractory products.展开更多
基金supported by the National High Technology Research and Development Program(Grant No.2015AA 7033102B)the State Key Laboratory of Aerospace Dynamics(Grant No.2016ADL-DW0304)
文摘Atmospheric drag is the main source of error in the determination and prediction of the orbit of low Earth orbit （LEO） satellites; however, empirical models that are used to account for this often have density errors of around 15%-30%. Atmospheric density determination has thus become an important topic for researchers. Based on the relationship between file atmospheric drag force and the decay of the semi-major axis of the orbit, we derived atmospheric density along the trajectory of challenging mini-satellite payload （CHAMP） satellite with its rapid science orbit （RSO） data. Three primary parameters--the ratio of cross-sectional area to mass, the drag coefficient, and the decay of the semi-major axis caused by atmospheric drag--were calculated. We also analyse the source of the error and made a comparison between the GPS-derived and reference density. The result for December 2, 2008, showed that the mean error of the GPS-derived density could be decreased from 29.21% to 9.20%, if the time span adopted for the process of computation was increased from 10 min to 50 min. The result for the entire month of December indicated that a density precision of 10% could be achieved, when the time span meets the condition that the amplitude of the decay of the semi-major axis is much greater than its standard deviation.
文摘1 Scope This standard specifies the definition, prineiple, apparatus and materials, procedure, expression of resuits and test report of determination of bulk density, apparent porosity and true porosity of dense shaped refractory products.
