The alignment between the radio-based International Celestial Reference Frame (ICRF) and the optical Gaia Celestial Reference Frame (Gaia-CRF) is critical for multi-waveband astronomy, yet systematic offsets at the optical bright end (G less than or similar to 13) limit their consistency. While radio stars offer a potential link between these frames, their utility has been restricted by the scarcity of precise Very Long Baseline Interferometry (VLBI) astrometry. In this study, we present new VLBI astrometry of 11 radio stars using the Very Long Baseline Array (VLBA), expanding the existing sample with positions, parallaxes, and proper motions measured. All 11 radio stars were detected, for 10 of which parallaxes and proper motions can be estimated, achieving median uncertainties better than 0.1 mas and 0.1 mas yr(-1), respectively. These new samples greatly contribute to the link between ICRF and Gaia-CRF at the optical bright end.

The VGOS 13m radio telescope located in Chiang Mai, Thailand is the first VGOS standard station built overseas by China. This station expands Chinese very long baseline interferometry (VLBI) network (CVN) and furthers multiple scientific goals, such as continuous monitoring of Earth orientation parameters and research into the terrestrial and celestial reference frames. The station is equipped with a wideband 2-14GHz receiver and an X/Ka dual-frequency receiver, a fast-slewing antenna, a DBBC3 high-speed data acquisition terminal and a high-speed recording terminal. This is aimed at improving observation efficiency and research quality. We developed the Remote Health Monitoring System (RHMS) specifically for the VGOS 13m radio telescope located in Thailand. This system integrates Tango Controls’ distributed middleware technology, allowing it to furnish the observation team with comprehensive historical and real-time status updates for the Chiang Mai VGOS station. Additionally, it promptly issues alerts for abnormalities, thereby improving the station’s unmanned monitoring, maintenance and operations capabilities, and operational performance. It also provides a feasible solution for remote monitoring of future overseas VGOS stations.

ABSTRACT The Gaia celestial reference frame (Gaia-CRF) will benefit from a close assessment with independent methods, such as Very Long Baseline Interferometry (VLBI) measurements of radio stars at bright magnitudes. However, obtaining full astrometric parameters for each radio star through VLBI measurements demands a significant amount of observation time. This study proposes an efficient observing strategy that acquires double-epoch VLBI positions to measure the positions and proper motions of radio stars at a reduced cost. The solution for CRF link compatible with individual VLBI position measurements is introduced, and the optimized observing epoch scheduling is discussed. Applying this solution to observational data yields results sensitive to sample increase or decrease, yet they remain consistently in line with the literature at the 1σ level. This suggests the potential for improvement with a larger sample size. Simulations show that the double-epoch strategy reduces CRF link parameter uncertainties by over 30 per cent compared to the five-parameter strategy.

Chang'e-5 is the most complicated mission of Chinese lunar project. Many separations of several detectors and unmanned rendezvous and docking in lunar orbit are accomplished. During the course of separating and approaching of two detectors, the same-beam very long baseline interferometry (VLBI) observations are carried on. We firstly present the real-time positioning for multi-detectors and differential positioning of CE-5 ascender and combination of orbiter-returner, which is the more direct and quick method to charge the orbit status. The CE-5 mission first achieved the orbital maneuver of CE-5 orbiter-returner combination from the lunar gravity back to the Earth at the distance of lunar orbit. We use the method of instantaneous states reduction to monitor the twice orbital transfer from the lunar to the Earth in real time, and precisely present the status of orbital maneuver, which provides the important reference for the positioning and orbit determination in the future deep-space exploration.

甚长基线干涉测量(very long baseline interferometry,VLBI)是测量地球定向参数(earth orientation parameters,EOP)的主要空间测地技术之一,中国正在建设名为VLBI全球观测系统(VLBI global observing system,VGOS)的新一代测地VLBI站,通过国际联测优化站网构型是实现高精度EOP测量的必由之路.以3个中国VGOS站为核心站,通过引入2个国外站构建5站联合观测网,分析评估了不同站网构型的EOP测量能力.针对每个站网构型,通过调整4个约束条件的权重因子批量生成相应的观测纲要,采用蒙特卡洛仿真方法选择最优的观测纲要,评价指标为EOP解算值的可重复性.仿真结果表明,由中国站、南非哈特比站以及澳大利亚霍巴特站组成的网型EOP测量能力最强,相对于中国3站组成的网型,dUT1测量精度提高5.7倍,极移的X、Y分量的测量精度分别提高2.8倍和18.3倍.仿真结果可为后续开展高精度EOP组网观测提供参考依据.

嫦娥五号(Change'E-5,CE-5)着上组合体与上升器先后成功着陆于月面.两探测器承担的任务不同,着陆方式不同,因此月面位置解算方法不同.联合统一 X波段(united X-band,UXB)深空测距站及甚长基线干涉测量技术(very long baseline interferometry,VLBI)的测量数据计算两者的月面位置.采用联合统计定位方法得到CE-5着上组合体的月面位置.讨论分别基于数传与侧音差分单向测距(differential one-way ranging,DOR)两种信号对月面位置的影响.观测资料的时间跨度在一定程度上影响定位结果.采用多项式拟合的运动学统计定轨方法归算了上升器受控落月轨迹及落月位置,并与单点定位结果符合在40m内.根据相关处理机最后输出时刻推算得到精确至ms的上升器的落月时刻.

对2021 年VLBI(Very Long Baseline Interferometry)全球观测系统(VLBI Global Observing System,VGOS)单基线开展的1 h世界时(Universal Time,UT1)加强观测数据进行分析,结果表明,VGOS单基线测得的UT1 与IERS(International Earth Rotation Service)C04序列提供的UT1 之差的RMS(Root Mean Square)为25.3 μs,优于传统S/X双频段UT1加强观测(Intensive observation,INT1)试验的28.2 μs,且UT1的平均形式精度提高1倍.因VGOS单基线1 h观测数目比INT1多1倍,其测得的UT1受极移误差的影响更加稳定,每100 μas的极移误差将对UT1引入2.8μs的偏移.此外分析了VGOS 30 min观测数据,除平均形式精度变差外,UT1测量结果与1 h结果相当,表明VGOS单基线30 min观测可用于UT1的超快速服务.同时分析和评估了2021年国内佘山与南山13 m VGOS基线的UT1加强观测能力,统计得到8次观测的RMS为46.2μs,平均形式误差为17.7μs,相比佘山25 m和南山25 m天线的S/X双频观测有显著提升.

The two newly-built VGOS (VLBI global observing system) antennas in Shanghai are blocked by the legacy large antennas nearby. In order to carry out joint observation using the VGOS station network, a new method for calculating the horizon mask based on the geometric position of the antennas is proposed. The horizon mask between the two antennas can be calculated from the geometric position, the antenna aperture and the distance from antenna reference point to the edge of the reflector. The maximum shielding angle of Tianma VGOS antenna is 22.3°, and the ratio between the shielded sky area and the sky area above 5° elevation is 2.19%. The maximum shielding angle of the Sheshan VGOS antenna is 23.4°, and the ratio between the shielded sky area and the sky area above 5° elevation is 3.14%. By adding the horizon mask of the antenna in the scheduling, the joint measurement of the VGOS station network was successfully implemented. The performance of UT1 measurement accuracy of the VGOS antenna on the Tianma-Wettzell baseline is simulated and analyzed by VieVS software. The result shows that the horizon mask of the Tianma VGOS antenna has no significant effect on the measurement accuracy of UT1.

Trying to achieve the best surface accuracy control with the fewest actuators, this article mainly studies the distribution of actuators and the method of panel design. The influence of the number of faulty actuators on the accuracy of the surface shape is demonstrated. In addition, the method incorporating a triangular panel, node index and the fitting solution method of a single panel is also given. This method provides a reference for the design and realization of an active surface or a deformable sub-reflector for high performance large aperture radio telescopes.

Based on the delay and delay rate data from Very Long Baseline Interferometry（VLBI） and range and Doppler data from United S or X band system, the precise point positioning in real-time mode is got and the lunar lander or rover in quasi- real time mode with joint statistical method is obtained. With the precise point positioning method, free of various mechanical constraint, the three-dimensioned position information in real-time can be obtained. In special orbit maneuvering period such as braking at perilune and CE-4 relay satellite entering the Halo orbit at the Lagrangian translation point L2 of Earth-lunar system, the six-orbit elements at real time can be obtained as well, offering a rapid reference for the project. Using the joint statistical method and lunar height constraint, the position of CE-3 lander arrives at 100- meter external coincidence accuracy. With VLBI Same Beam Interferometry（SBI） phase-delay measurements, the external coincidence accuracy of the CE-3 rover reached at 1- meter level. It will promote more positioning analysis in the future deep space exploration projects.

佘山13m射电望远镜作为新一代天体测量与空间大地测量甚长基线干涉测量系统,配备有2～14GHz宽频接收机和X/Ka双频接收机.指向精度是射电望远镜性能的重要指标之一,一般要求好于最高配置频率波束宽度的1/10.对于佘山13 m口径射电望远镜,Ka波段32 GHz时的指向精度约为18 as.基于该望远镜的指向扫描实测数据,探讨了指向改正模型建立方法,包括测量功率曲线拟合、积分时间影响分析、指向改正模型参数设置等,实测评估了该望远镜的指向精度.所得指向改正模型可作为系统调试与改进的依据,也是望远镜系统指标测量和观测目标精确跟踪的保障,数据解析模型与分析流程可用于测量系统的日常指向精度检核,也可供类似工程测量参考.

2018-06嫦娥四号中继星发射任务圆满完成,为2018-12的嫦娥四号月球背面降落任务打下良好的基础,其中甚长基线干涉测量技术(very long baseline interferometry,VLBI)测轨分系统在卫星的定位、变轨等方面起到了重要的作用.统计了嫦娥四号中继星任务实时阶段VLBI观测的时延、时延率和定位结果的精度,讨论了定位归算在嫦娥四号中继星轨控弧段实时轨迹监测中的应用.在中继星进入Halo轨道的过程中,能够实时监测到定位归算结果给出的轨道根数变化,以实时监测变轨情况,并通过事后与定轨结果比对,判断定位结果的正确性与准确性,从而为后续飞行任务提供了一种新的Halo轨道实时监测的方法.

One of the most efficient ways to probe the lunar inner structure at present is through the study of its rotation. Range and range rate (Doppler) data between the Chang'E-3 lander and station on the Earth were collected from the beginning of the Chang'E-3 lunar mission in 2013. These observation data, taken together with the existing lunar laser ranging data, provide a new approach to extend research on the Earth-Moon system. The high precision of current observation data imposes exacting demands, making it necessary to include previously neglected factors. In this paper, motivated by progress of the Chinese lunar exploration project and to use its data in the near future, two lunar models: a one-layer model and a two-layer model with a fluid core, were applied to the rotational equations based on our implemented algorithm of the Moon's motion. There was a difference of about 0.5 '' in phi and psi, but 0.2 '' in theta between the two models. This result confirms that stratification of the inner structure of the Moon can be inferred from rotation data. We also added precise Earth rotation parameters in our model; the results show that this factor is negligible at present, due to the limited precision of the existing data. These results will help us understand the rotational process clearly and build a more realistic Earth-Moon model when we combine Lunar Laser Ranging data with high precision radio data to fit lunar motion in the near future.

Very Long Baseline Interferometry (VLBI) is an essential and supporting technique for the realization of terrestrial and celestial reference frames, the state-of-the-art unique technique to precisely determine all dimensional Earth Orientation Parameters (EOP). The design and implementation aspects of the Sheshan 13-m radio telescope is described in this paper concerning the key components of the system including the antenna, cryogenic receiver, up-down converter, data acquisition and time frequency devices, monitoring and control software. Some preliminary results of typical systematic performance and fringe checking are presented. However, some technique issues require further discussion and investigation and the whole system requires much more testing and improvement.

The 13-meter radio telescope monitor and control software, also called Client Graphics User Interface Library Tools (CGLT), is a set of graphical user interfaces provided to engineers and operators. It is a modular solution for monitoring and controlling the 13-meter radio telescope, which is a telescope under construction in Sheshan, Shanghai. Design philosophy, functionality and implementation of the software will be introduced in this article.

Understanding the structure of and dynamic processes in the deep interior of planets is crucial for understanding their origin and evolution. An effective way to constrain them is through observation of rotation and subsequent simulation. In this paper, a numerical model of the Moon’s rotation and orbital motion is developed based on previous studies and implemented independently. The Moon is modeled as an anelastic body with a liquid core. The equations of the rotation were nonlinear and the Euler angles are cross coupled. We solve them numerically via the Runge-Kutta-Fehlberg (RKF) and multi-steps Adams-Bashforth-Moulton (ABM) predictor-corrector numerical integration. We have found that adequate accuracy is maintained by taking twelve steps per day using eleventh differences in the integrating polynomial. The lunar orbital and rotational equations are strongly coupled, so we integrated the rotation and motion simultaneously. We refer to other planetary informations from the newest planetary and lunar ephemeris INPOP17a, which is reported had fitted the longest LLR (Lunar Laser Ranging) observation data. Using the model GL660B from GRAIL (Gravity Recovery and Interior Laboratory) mission, we firstly compare our numerical results with the INPOP17a to prove the reasonability of our model. After that we apply the lunar gravity model CEGM02 determined from Chang’E-1 mission and SGM100h from SELENE mission to our model, the difference between results from CEGM02 and GL660B are less than \(-0.20 \sim0.15\) arc-second, and \(-0.25 \sim0.20\) arc-second for GL660B and SGM100h. Compared to SGM100h, the results show that the low degree and order coefficients (less than 6 from this paper) of lunar gravity field were improved in CEGM02 as expected. It is the first time to demonstrate that these models can be applied to lunar rotation model. These results manifest that a development of the gravity field measure will help us to know the rotation motion more precisely.

利用最新的GRAIL月球重力数据和LRO地形数据,计算重力/地形导纳及其相关性.结果表明,最新的测月数据能够在球谐系数达到500阶的时候依然保持比较高的相关性,精度得到很大的提高.全月重力/地形导纳在50阶以下(波长大于～ 220 km),之后迅速增加,维持在110 mgal/km附近.利用Gauss-Newton迭代法计算得到全月弹性平均厚度Te =11.7 km,表明很有可能月球地形在月球早期就已经形成.

In accordance with practical needs of a project,the mutual shielding effect between two radio antennas located within some limited area is analyzed in this paper.The concept of the externally connected sphere of an antenna in altazimuth(azimuth-elevation) mount is put forward.A calculation method via numerical integral of the area of a part of spherical crown is given.The mutual shielding effect between the 25 m and 13 m radio telescope at Sheshan is analyzed and estimated.The result is of theoretical reference meanings in the design phase of the project concerning the position selection and height design of the supporting tower of the 13 m antenna.The analytical idea and method can also be used as reference by similar engineering practice.

目前,月面太阳能依然是人类进行月面探测的最主要能量来源之一.因此,对月面光照情况的研究不仅为月球的形成演化研究提供重要科学信息,同时也对月球探测有着重要的工程和国防意义.本文利用LRO(Lunar Reconnaissance Orbiter)获得最新的高精度((1/1 024)°)的月面地形数据,创新性地提出了一个基于多线程编程技术的计算算法,实现了并行计算.分辨率和计算效率都较之前的结果有了很大提高,在较短的时间内生成了月球两极地区最低太阳高度角数据库,为今后的月球两极区域高精度和时间长跨度的光照条件分析提供了数据支持.