月球起源之谜团揭开还待时日

关于月球究竟来自何方？它到底是怎样形成的？一直作为一个谜而留在人们心问。和其他卫星来比,月球有好多奇异之处,让人难以理解。关于月球的起源,归纳起来主要有以下5种学说。     

星星为什么会眨眼？

“一闪一闪亮晶晶,满天都是小星星”是我们再熟悉不过的童谣了,夜晚仰望星空看繁星闪烁,有没有在脑海中飘过这个问题：小星星们为什么会一闪一闪“眨眼睛”呢？     

Instructions for authors

正Research in Astronomy and Astrophysics publishes original research papers and reviews on all branches of astronomy and astrophysics.Reviews are by invitation only.Important new results that require rapid publication can be submitted as a Letter(Letters must be restricted in length     

The New Doppler Shift-and-Range Positioning Algorithm for the Global Navigation Satellite System

Under some circumstances in using the Global Navigation Satellite System （GNSS）, since navigation signals from the satellites are blocked a receiver cannot simultaneously track four or more satellites to estimate its 3-dimensional （3D） coordinates and clock bias. This paper proposes a Doppler Shift-and-Range （DS-R） positioning algorithm with which pseudoranges and Doppler shifts are simultaneously measured. The measurement results are used as inputs to four equations in the algorithm, and the 3D position can be estimated from the equations. Through this approach the algorithm can achieve real-time 3D positioning. By synthesizing multi-frequency observational results and adopting a new method of jointly using code-carrier phases, this algorithm expectably has accuracies similar to those of the standard approach of point positioning.     

Relativistic transformation between y and TCG for Mars missions under IAU Resolutions

Considering the fact that the general theory of relativity has become an in- extricable part of deep space missions, we investigate the relativistic transformation between the proper time of an onboard clock τ and the Geocentric Coordinate Time （TCG） for Mars missions. By connecting τ with this local timescale associated with the Earth, we extend previous works which focus on the transformation between τ and the Barycentric Coordinate Time （TCB）. （TCB is the global coordinate time for the whole solar system.） For practical convenience, the relation between τ and TCG is recast to directly depend on quantities which can be read from ephemerides. We find that the difference between τ and TCG can reach the level of about 0.2 seconds in a year. To distinguish various sources in the transformation, we numerically calculate the contributions caused by the Sun, eight planets, three large asteroids and the space- craft. It is found that if the threshold of 1 microsecond is adopted, this transformation must include effects due to the Sun, Venus, the Moon, Mars, Jupiter, Saturn and the velocities of the spacecraft and Earth.     

行星科学与深空探测（一）——行星科学的起源发展及重要性

行星是在宇宙演化到一定的时间后形成的,它是天体形成的重要类型。与星系宇宙以及恒星不同,行星由于其质量相对较小,因此其演化也有其特殊的过程,比如,总体来讲没有像宇宙、星系和恒星那样,物质与性态变化那么剧烈。行星的形成和演化有其自己独特的规律。行星科学研究是人类在全面认识宇亩演化过程中不可缺少的环节,是天文学的重要分支学科。     

火星无线电掩星探测进展

火星是地球的姊妹星，研究火星对了解火星、地球乃至太阳系的演化具有重要意义.自从1964年美国水手4号发射，首次成功地运用无线电掩星技术探知到火星的环境特征之后，国际上不少的火星任务都开展了掩星实验，取得了重要进展.本文依据采用了无线电掩星技术进行勘探的火星探测器发射时间顺序展开调研，针对具有开创性的水手系列、火星全球勘测者、火星快车、火星大气挥发演化探测器、天问一号等，梳理分析和总结了各任务的火星无线电掩星方式以及所获取的廓线数量、位置分布、获取方式等产品信息，以及部分相关的研究结果.本文还分析了当前火星无线电掩星探测方式存在的局限性，并探讨了可能的对策.火星无线电掩星后续可重点考虑多颗星-星掩星结合星-地掩星方式形成掩星星座；并通过选用适当的信号探测频率、改进反演算法等方式进一步提高掩星质量；火星掩星探测手段还可与火星顶部探测雷达、直接探测等手段相结合，发展火星多源数据融合技术.随着探测方式的不断改进，无线电掩星探测将是火星探测的重要手段.未来会有数量越来越多、时间与空间覆盖越来越全面、精度越来越高的掩星数据用于火星的整个空间环境研究，包括大、中尺度乃至小尺度结构的特征与演化规律都将...