In this paper, the phenomena of Earth’s motion about its own axis, the ecliptic plane of the Earth’s orbit around the Sun, the definitions of equinoxes, the precession of equinoxes, Earth’s wobble and other astrono...In this paper, the phenomena of Earth’s motion about its own axis, the ecliptic plane of the Earth’s orbit around the Sun, the definitions of equinoxes, the precession of equinoxes, Earth’s wobble and other astronomical terminology are briefly described. Some of the existing theories explaining the precession of equinox and their inadequacies are brought out. New Hypothesis is that precession of equinoxes is a direct result of Orbital spin of Earth in a retrograde direction—a celestial phenomenon similar to that of Moon’s Orbital spin around the Earth. The study of Moon’s orbit round the Earth reveals the exact movement of Earth’s orbit, which causes precession of equinoxes without any ambiguity. The analogy presented herein demonstrates the plausible hypothesis.展开更多
Chevrolet Equinox是以GM全球Crossover底盘所推出的第一辆新车。Chevrolet预估这具新的2.4升高效能引擎（最大马力182hp）搭配前驱系统．将会有同级车中最佳的油耗值1062km／L．比前一代车型提升了25％的引擎效率。另一款则是搭配30升V...Chevrolet Equinox是以GM全球Crossover底盘所推出的第一辆新车。Chevrolet预估这具新的2.4升高效能引擎（最大马力182hp）搭配前驱系统．将会有同级车中最佳的油耗值1062km／L．比前一代车型提升了25％的引擎效率。另一款则是搭配30升V6引擎．展开更多
Geostationary(GEO) satellites form an indispensable component of the constellation of Beidou navigation system(BDS). The ephemerides, or predicted orbits of these GEO satellites(GEOs), are broadcast to positioning, na...Geostationary(GEO) satellites form an indispensable component of the constellation of Beidou navigation system(BDS). The ephemerides, or predicted orbits of these GEO satellites(GEOs), are broadcast to positioning, navigation, and timing users. User equivalent ranging error(UERE) based on broadcast message is better than 1.5 m(root formal errors: RMS) for GEO satellites. However, monitoring of UERE indicates that the orbital prediction precision is significantly degraded when the Sun is close to the Earth's equatorial plane(or near spring or autumn Equinox). Error source analysis shows that the complicated solar radiation pressure on satellite buses and the simple box-wing model maybe the major contributor to the deterioration of orbital precision. With the aid of BDS' two-way frequency and time transfer between the GEOs and Beidou time(BDT, that is maintained at the master control station), we propose a new orbit determination strategy, namely three-step approach of the multi-satellite precise orbit determination(MPOD). Pseudo-range(carrier phase) data are transformed to geometric range(biased geometric range) data without clock offsets; and reasonable empirical acceleration parameters are estimated along with orbital elements to account for the error in solar radiation pressure modeling. Experiments with Beidou data show that using the proposed approach, the GEOs' UERE when near the autumn Equinox of 2012 can be improved to 1.3 m from 2.5 m(RMS), and the probability of user equivalent range error(UERE)<2.0 m can be improved from 50% to above 85%.展开更多
文摘In this paper, the phenomena of Earth’s motion about its own axis, the ecliptic plane of the Earth’s orbit around the Sun, the definitions of equinoxes, the precession of equinoxes, Earth’s wobble and other astronomical terminology are briefly described. Some of the existing theories explaining the precession of equinox and their inadequacies are brought out. New Hypothesis is that precession of equinoxes is a direct result of Orbital spin of Earth in a retrograde direction—a celestial phenomenon similar to that of Moon’s Orbital spin around the Earth. The study of Moon’s orbit round the Earth reveals the exact movement of Earth’s orbit, which causes precession of equinoxes without any ambiguity. The analogy presented herein demonstrates the plausible hypothesis.
基金supported by the National Natural Science Foundation of China(Grant Nos.11033004,41204022 and 41204023)the Opening Project of Shanghai Key Laboratory of Space Navigation and Position Techniques(Grant Nos.12DZ2273300 and 13DZ2273300)Surveying and Mapping Basic Research Program of National Administration of Surveying,Mapping and Geoinformation(Grant No.2013-01-06)
文摘Geostationary(GEO) satellites form an indispensable component of the constellation of Beidou navigation system(BDS). The ephemerides, or predicted orbits of these GEO satellites(GEOs), are broadcast to positioning, navigation, and timing users. User equivalent ranging error(UERE) based on broadcast message is better than 1.5 m(root formal errors: RMS) for GEO satellites. However, monitoring of UERE indicates that the orbital prediction precision is significantly degraded when the Sun is close to the Earth's equatorial plane(or near spring or autumn Equinox). Error source analysis shows that the complicated solar radiation pressure on satellite buses and the simple box-wing model maybe the major contributor to the deterioration of orbital precision. With the aid of BDS' two-way frequency and time transfer between the GEOs and Beidou time(BDT, that is maintained at the master control station), we propose a new orbit determination strategy, namely three-step approach of the multi-satellite precise orbit determination(MPOD). Pseudo-range(carrier phase) data are transformed to geometric range(biased geometric range) data without clock offsets; and reasonable empirical acceleration parameters are estimated along with orbital elements to account for the error in solar radiation pressure modeling. Experiments with Beidou data show that using the proposed approach, the GEOs' UERE when near the autumn Equinox of 2012 can be improved to 1.3 m from 2.5 m(RMS), and the probability of user equivalent range error(UERE)<2.0 m can be improved from 50% to above 85%.
