The original idea of a new method for determination of satellite orbits by transfer is from Two-Way Satellite Time and Frequency Transfer (TWSTFT). The original method is called "determination of satellite orbit by transfer". The method is not only for determination of satellite orbit but also for the time transfer with high accuracy and precision. The advantage is that the accuracy and the precision for determination of satellite orbit are very high and the new method is favorable for various applications. The combination of various signals disseminated and received forms various modes of satellite orbit determinations. If receivers at stations receive the own station-disseminated signals via a satellite transponder, it forms an orbit determination mode called "receiving the own station-disseminated signals mode". If receivers at all stations receive the signals disseminated from the master station via satellite transponders, it forms an orbit determination mode called "receiving the master station-disseminated signals mode". If all of receivers at stations receive all stations-disseminated signals via satellite transponders, it forms an orbit determination mode called "receiving all stations-disseminated signals mode". Also there are other combinations of signals for satellite orbit determination. For different orbit determination modes with different signal combinations, their rigorous formulae of processing are hereby presented in this paper. The accurate and the precise satellite orbit determination for both of the modes, "receiving the own station-disseminated signals mode" and "receiving the master station-disseminated signals mode" is attempted. It shows that the accuracy and precision for both of modes are nearly the same, the ranging accuracy is better than 1 cm, and the observation residuals of satellite orbit determination are better than 9 cm in the observation duration of 1 day. TWSTFT, transfer, satellite orbit determinationThere are several kinds of techniques for satellite orbit determinations. Recently, the united system for S Band (USB) is used for regular observations of orbit determinations. The ranging accuracy for the USB is 3-5 m and the precision for orbit determination is about few hundreds meters. It meets the requirements for spacecraft long-term management, so the USB is still used in the observations of orbit determinations of spacecraft at present. With the development of deep space tracking and satellite navigation system, especially for the area positioning system, such as Chinese Area Positioning System (CAPS), requirements of accuracy and precision for orbit determination are very high. The CAPS is consisted by sets of Geostationary Satellites (GEO) placed at an altitude of 36000 km above the equator. The angle of the GEO satellite to Earth is very small (17.6°). If the ranging stations are only placed in the area of China, the angle of the GEO satellite to the area is only few degrees. Viewing from space, the directions from satellite to all stations are nearly parallel. Furthe...
Abstract. This paper presents an analysis of astrometric reduction methods for the calibration of a CCD target. To compare these methods, we collected about 3000 recent CCD observations between 1990-1997. We discuss the comparison of the four main contemporary theories describing the eight major satellites of Saturn, used in recent CCD astrometric reduction. We show that these theories developed by Taylor & Shen (1988), Dourneau (1993), Harper & Taylor (1999) and Duriez & Vienne (1997), give a rather good representation of the orbits of the eight main satellites, especially for satellites III-VI. In the CCD astrometric reduction, we point out a bias of the theories on the derived satellite positions, which can reach about 0. 03. Duriez and Vienne's TASS theory (1997), built with significantly higher consistency than the other three, generally leads to the lowest residuals for the observations analysed here. Due to its high quality, we recommend use of this theory for CCD reduction. Systematic errors affecting satellites' derived positions should be small, due to the quality of the TASS theory. This procedure might be an alternative to the multi-theory reduction method previously proposed by Qiao et al. (1999). Observations of satellites obtained from CCD reduction using TASS are expected to be significantly more accurate (0. 015) than observations reduced from any other theory (about 0. 05).
Notopterygium incisum Ting ex H. T. Chang is a rare and endangered traditional Chinese medicinal plant. In this research, we built a comprehensive habitat suitability (CHS) model to analyze the potential suitable habitat distribution of this species in the present and future in China. First, using nine different algorithms, we built an ensemble model to explore the possible impacts of climate change on the habitat distribution of this species. Then, based on this model, we built a CHS model to further identify the distribution characteristics of N. incisum‐suitable habitats in three time periods (current, 2050s, and 2070s) while considering the effects of soil and vegetation conditions. The results indicated that the current suitable habitat for N. incisum covers approximately 83.76 × 103 km2, and these locations were concentrated in the Tibet Autonomous Region, Gansu Province, Qinghai Province, and Sichuan Province. In the future, the areas of suitable habitat for N. incisum would significantly decrease and would be 69.53 × 103 km2 and 60.21 × 103 km2 in the 2050s and 2070s, respectively. However, the area of marginally suitable habitat would remain relatively stable. This study provides a more reliable and comprehensive method for modelling the current and future distributions of N. incisum, and it provides valuable insights for highlighting priority areas for medicinal plant conservation and resource utilization.
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