空间环境指数是描述空间碎片对空间环境长期影响的量化评估指数。用该指数可以对比分析某空间物体的在轨运行是否对其他物体乃至整体环境产生较大威胁。对现有典型空间碎片环境指数及其建模方法进行分析和比较,并针对过去模型中平均碰...空间环境指数是描述空间碎片对空间环境长期影响的量化评估指数。用该指数可以对比分析某空间物体的在轨运行是否对其他物体乃至整体环境产生较大威胁。对现有典型空间碎片环境指数及其建模方法进行分析和比较,并针对过去模型中平均碰撞风险计算方法的不足,提出一种空间环境指数模型,即基于轨道间最小距离(minimum orbital intersection distance,MOID)的空间环境指数(MOID-based space index,MBSI)。该指数综合空间碎片的质量、有效截面积等因素,基于MOID考虑碰撞风险,计算近地轨道(low Earth orbit,LEO)区域中不同空间物体的MBSI指数,并与已有的R_(N)指数、CSI(criticality of spacecraft index,CSI)指数的结果进行比对和分析。MBSI与R_(N)指数、CSI指数符合度超过60%,而MBSI更能体现空间物体寿命期内的危险程度。展开更多
To understand the formation mechanism of blue stragglers in open clusters, we conducted a photometric analysis for a blue straggler eclipsing binary in the old open cluster NGC 2141. By using the least square fitting ...To understand the formation mechanism of blue stragglers in open clusters, we conducted a photometric analysis for a blue straggler eclipsing binary in the old open cluster NGC 2141. By using the least square fitting of times of minima, we derived the ephemeris and redetermined the orbital period of this system to be 0.6227 d. We have also done a photometric analysis for light curve with the Wilson-Devinney Code （2003）. The photometric solutions reveal a semi-detached binary with the second- ary component filling its Roche lobe. The photometric mass ratio MJMI （secondary/primary） was determined to be 0.190_＋0.002 and the ratio of V-band luminosity L2/LI（V） is about 0.033_＋0.001, which indicates the secondary component is overluminous. Thus, this blue straggler likely results from a substantial mass exchange between these two components.展开更多
X-ray pulsars offer stable, periodic X-ray pulse sequences that can be used in spacecraft positioning systems. A method using X-ray pulsars to determine the initial orbit of a satellite is presented in this paper. Thi...X-ray pulsars offer stable, periodic X-ray pulse sequences that can be used in spacecraft positioning systems. A method using X-ray pulsars to determine the initial orbit of a satellite is presented in this paper. This method suggests only one detector to be equipped on the satellite and assumes that the detector observes three pulsars in turn. To improve the performance, the use of incremental phase in one observation duration is proposed, and the incremental phase is combined with the time difference of arrival(TDOA). Then, a weighted least squares(WLS) algorithm is formulated to calculate the initial orbit. Numerical simulations are performed to assess the proposed orbit determination method.展开更多
文摘空间环境指数是描述空间碎片对空间环境长期影响的量化评估指数。用该指数可以对比分析某空间物体的在轨运行是否对其他物体乃至整体环境产生较大威胁。对现有典型空间碎片环境指数及其建模方法进行分析和比较,并针对过去模型中平均碰撞风险计算方法的不足,提出一种空间环境指数模型,即基于轨道间最小距离(minimum orbital intersection distance,MOID)的空间环境指数(MOID-based space index,MBSI)。该指数综合空间碎片的质量、有效截面积等因素,基于MOID考虑碰撞风险,计算近地轨道(low Earth orbit,LEO)区域中不同空间物体的MBSI指数,并与已有的R_(N)指数、CSI(criticality of spacecraft index,CSI)指数的结果进行比对和分析。MBSI与R_(N)指数、CSI指数符合度超过60%,而MBSI更能体现空间物体寿命期内的危险程度。
基金supported by the National Natural Science Foundation of China (Grant Nos. 11033008 and 11103072)the Chinese Academy of Sciences (Grant No. KJCX2-YW-T24)the National Basic Research Program of China (Grant No. 2009CB824800)
文摘To understand the formation mechanism of blue stragglers in open clusters, we conducted a photometric analysis for a blue straggler eclipsing binary in the old open cluster NGC 2141. By using the least square fitting of times of minima, we derived the ephemeris and redetermined the orbital period of this system to be 0.6227 d. We have also done a photometric analysis for light curve with the Wilson-Devinney Code （2003）. The photometric solutions reveal a semi-detached binary with the second- ary component filling its Roche lobe. The photometric mass ratio MJMI （secondary/primary） was determined to be 0.190_＋0.002 and the ratio of V-band luminosity L2/LI（V） is about 0.033_＋0.001, which indicates the secondary component is overluminous. Thus, this blue straggler likely results from a substantial mass exchange between these two components.
基金supported by the National Natural Science Foundation of China(No.61401340)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2016JM6035)+1 种基金the Fundamental Research Funds for the Central Universities,China(No.JB161303)and the Areospace T.T.&C.Innovation Program(No.201515A)
文摘X-ray pulsars offer stable, periodic X-ray pulse sequences that can be used in spacecraft positioning systems. A method using X-ray pulsars to determine the initial orbit of a satellite is presented in this paper. This method suggests only one detector to be equipped on the satellite and assumes that the detector observes three pulsars in turn. To improve the performance, the use of incremental phase in one observation duration is proposed, and the incremental phase is combined with the time difference of arrival(TDOA). Then, a weighted least squares(WLS) algorithm is formulated to calculate the initial orbit. Numerical simulations are performed to assess the proposed orbit determination method.
