昆明站流动VLBI首次长距离实验观测

我国流动VLBI首次在昆明与上海佘山站组成长基线观测。本文对实验观测、射电源的选取、数据文件的生成以及数据处理等情况作了介绍，并对流动VLBI今后的观测提出了一些建议。     

CEI对静止轨道共位卫星的轨道确定

主要考察了CEI对静止轨道共位卫星的轨道确定能力。仿真结果表明,利用CEI对共位卫星进行定轨时,需采用基线阵列。对于110°E共位卫星采用三亚-昆明基线阵列、10 km基线和2 d的数据,可使绝对轨道精度达百米级;外推至14 d时,相对轨道精度保持在m级。同样,要使绝对和相对轨道精度达到相同的量级,对于80°E共位卫星,需选用昆明-三亚基线阵列、100 km基线和1 d的观测弧段;对于140°E共位卫星,需选用上海-三亚基线阵列5、0 km基线和2 d的观测弧段。     

DCW－01型流动VLBI测量仪时频系统性能检测

我国自行研制的第一台DCW 0 1型流动VLBI测量仪已在昆明进行了试观测 ,文中介绍了该仪器的时频系统 ,并在观测实验中对其精度、稳定度作了检测。结果显示 ,所采用的时频系统 ,其精度及稳定度分别优于 1× 1 0 -12 和 1× 1 0 -14 ,较好地满足了流动VLBI测量仪时频系统的既定要求 ,能够精密、可靠地适用于流动VLBI的观测实验。最后对仪器的检测工作提出了一些改进和建议。     

DCW-01型流动VLBI测量仪时频系统性能检测

我国自行研制的第一台DCW-01型流动VLBI测量仪已在昆明进行了试观测,文中介绍了该仪器的时频系统,并在观测实验中对其精度、稳定度作了检测.结果显示,所采用的时频系统,其精度及稳定度分别优于1×10-12和1×10-14,较好地满足了流动VLBI测量仪时频系统的既定要求,能够精密、可靠地适用于流动VLBI的观测实验.最后对仪器的检测工作提出了一些改进和建议.     

不同时长北斗基线精度差异分析

北斗导航系统已经可以为亚太地区提供导航服务,其中精度的测试和评估是目前研究的热点。本文以4个连续观测站的观测数据为基础,进行了不同时长静态基线解算,并与精确定位结果进行比较,发现静态解算精度优于3 cm,E、U、V三个方向的向量精度随着基线观测时长的增加而提高。同时进行北斗动态单历元基线解算,与精确定位结果相比,计算发现北斗单历元动态基线解算精度优于0.2 m,并且E、U、V三个方向的向量精度随着基线观测时间的长度增加而提高,有趋于稳定的趋势。比较结果表明,北斗系统具有良好的稳定性,监测时间越长,定位精度越高。     

北斗三号短基线四频组合定位方法研究

北斗三号全球卫星导航系统现已提供4个频率以上的观测数据,支持多频组合定位理论和方法的研究。基于此,文中提出一种短基线下的北斗四频组合定位解算方法,利用北斗B1I,B3I,B1C,B2a 4个频率的观测数据两两组合形成独立不相关的窄巷观测值联立,以位置参数和双差模糊度组成状态向量,结合卡尔曼滤波估计进行定位解算。基于该方法,文中针对两组不同长度的短基线进行测试,结果显示：在17 m短基线中,该方法平面精度优于2 mm,高程方向精度优于4 mm;在3 km的短基线中,平面精度优于4.5 mm,高程精度优于6 mm。测试结果表明,在短基线情况下,该方法的定位精度相较于北斗单频及三频方法在平面和高程方向均有不同程度的提高。     

基于等价观测方程的GPS/GLONASS组合多基线解算方法

进行独立参数化时,GNSS观测方程的双差、单差与非差观测方程理论上是等价的。利用按高度角定权的模型以及不同测站跟踪不同数量卫星的等价观测方程,实现基于简化等价观测方程的GPS/GLONASS组合多基线解算,包括多基线模糊度的固定、基线向量的解算与精度分析,并用多个测站的GPS/GLONASS同步实测载波相位和码伪距观测数据完成多基线解算分析。计算结果表明,由于多个测站的同时作用导致几何强度增强,降低模糊度间的相关性,有利于模糊度的快速解算;同时简化等价观测方程,提高法方程的形成速度,解算的基线精度也优于单基线解算模式。     

流动VLBI观测频率窗口的选择

为即将启动的流动ＶＬＢＩ系统选取了频率窗口, 并对我国ＶＬＢＩ站所组成基线的系统性能和观测精度进行了估计。结果表明该频窗的选取是可行的。     

中国新一代流动卫星激光测距系统研究

我国新一代流动卫星激光测距（SLR）系统TROS-I于2000年建成，并成功地在乌鲁木齐、拉萨西部地区进行了流动观测．弥补了国家SLR跟踪网在亚洲腹地的空缺。本文介绍了TROS—I的组成结构及其在中国西部对Lageos等卫星的观测情况。结果表明，观测标准点精度优于10mm，最大测程达2万km，可见，流动观测能有效地增强我国激光测距网的监测能力．对于我国自主卫星的精密定轨、中国大陆地壳现今运动的研究可发挥重要作用。     

陆态网络灵山重力基线场初值测定与数据分析

介绍了灵山重力基线重力观测情况,并对观测结果进行了分析。分析结果表明,相对重力联测成果互差优于40.0×10-8ms-2,绝对重力观测成果中误差优于5.0×10-8ms-2,重力垂直梯度观测成果中误差优于3.0×10-8ms-2,最终各点成果精度优于5.0×10-8ms-2,满足中国大陆构造环境监测网络的技术要求,可供相关项目重力仪标定使用。     

昆明固置流动VLBI站点归心

参考《全球定位系统（GPS）测量规范》之附录G归心元素测定，采用测GPS的方法，对固置在昆明的流动VLBI站进行了归心计算，在得到流动VLBI用GPS技术所测量的地心坐标同时，指出了参考文献[1]中存在的矛盾与错误，并结合实际应用，给出了一组实用的计算公式。     

The mobile VLBI campaigns in Norway (1989–1993)

Summary Since 1989 several mobile VLBI campaigns have been carried out in Europe with a total of 14 sites occupied. The Norwegian stations at Tromsø and Trysil are the only mobile VLBI stations in Europe observed in more than one epoch, so they have produced the most interesting data from these campaigns. Tromsø is the only station observed in the two summer campaigns (1989 and 1992), while Trysil has been the winter site for MV-2 since late 1991 until the spring of 1993. In this paper we describe the mobile VLBI campaigns in Norway including the observational work and the detailed geodetic analysis performed with OCCAM V3.3. We have also analyzed a series of GPS data sets from Tromsø in order to check the reliability of the VLBI results for that station. The results reveal the need for a very careful design of mobile VLBI experiments, in particular regarding the consistency of the network and of the observation schedules, and the special care that is required in the analysis of the mobile VLBI data in order to achieve significant conclusions.     

我国VLBI观测网备选射电源的扩充

针对我国 VL BI观测网对射电源的特殊要求 ,给出了现有备选射电源的列表和天球分布图 ,提出了扩充备选射电源数量的必要性。结合 2 0 0 0年 1月“上海 -昆明基线”试观测 ,在原有的 12个备选射电源的基础上 ,又增选了 4个。观测及计算结果显示 ,12个备选源中 ,有 11个的信噪比和相关流量都很好 ,1个勉强能用 ;4个增选的源中 ,有 3个达到指标 ,应放入以后的备选源中。     

流动VLBI天线系统噪声温度及天线效率测量

我国自行研制的第一套流动VLBI系统——DCW—01型流动VLBI测量仪，目前已在国家重大科学工程“中国地壳运动观测网络”中投入使用。在流动VLBI的观测试验中，天线系统噪声温度和天线效率是观测前系统调试和检测的两项重要内容。天线系统噪声温度是衡量流动VLBI观测系统内部噪声程度的特性指标；天线效率反映了天线系统对到达天线能量的刊用率，在很多计算公式中是一个很重要的参数。因此，精确地测量它们的值是进行相关处理和计算的前提。文中结合我国流动VLBI观测站的研制与建设，介绍了流动VLBI测量仪的天线及接收机系统，并详细阐述了其天线系统噪声温度和天线效率的测量。     

利用2006—2015年VLBI数据进行地球定向参数解算与分析

目前正处在下一代甚长基线干涉测量（very long baseline interferometry,VLBI）系统的建设时期。利用维也纳VLBI与卫星软件（Vienna VLBI and satellite software,VieVS）解算了2006—2015年的VLBI数据,得到了10 a的地球定向参数（Earth orientation parameters,EOP）时间序列,并与国际地球自转服务机构的结果进行了对比。利用解算结果得到了10 a的日长变化时间序列,通过傅里叶分析得出了日长变化的短周期、半月周期、月周期、半年周期和周年周期,同时还分析得到了极移序列中的周年项和张德勒周期项以及章动改正序列中的自由核章动项。此次解算工作可为武汉大学卫星台站日后的VLBI数据解析积累一定的经验。     

Modeling thermal deformation of VLBI antennas with a new temperature model

Temperature variations at very long baseline interferometry (VLBI) sites cause thermal deformations of the VLBI antennas and corresponding displacements of the VLBI reference points. The thermal deformation effects typically contain seasonal and daily signatures. The amplitudes of the annual vertical motion of the antenna reference point can reach several millimeters, depending on the design of the antenna structure, on the material, and on the environmental effects such as global station position, station height and climatology effects. Simple methods to correct this effect use the difference of the environmental temperature with respect to a defined reference temperature, the antenna dimensions, the elevation of the antenna, the material of antenna structure. Applying these simple models for thermal deformation in the VLBI data analysis improves the baseline length repeatability by 3.5%. A comparison of these simple models with local thermal deformation measurements at the antennas in Onsala and Wettzell show that the local measurements and the modeled corrections agree well when the temperature of the antenna structure is used, but agree less good when the surrounding air temperatures are used. To overcome this problem we present a method to model temperature penetration into the antenna structures, that allows to model thermal deformation effects that agree with the observed vertical deformation of the Onsala and Wettzell radio telescopes with a root mean square deviation of 0.07 and 0.13 mm, respectively. Possible implementations in the VLBI analysis are presented, and the definition of an adequate reference temperature is discussed.     

On the long-term stability of terrestrial reference frame solutions based on Kalman filtering

The Global Geodetic Observing System requirement for the long-term stability of the International Terrestrial Reference Frame is 0.1 mm/year, motivated by rigorous sea level studies. Furthermore, high-quality station velocities are of great importance for the prediction of future station coordinates, which are fundamental for several geodetic applications. In this study, we investigate the performance of predictions from very long baseline interferometry (VLBI) terrestrial reference frames (TRFs) based on Kalman filtering. The predictions are computed by extrapolating the deterministic part of the coordinate model. As observational data, we used over 4000 VLBI sessions between 1980 and the middle of 2016. In order to study the predictions, we computed VLBI TRF solutions only from the data until the end of 2013. The period of 2014 until 2016.5 was used to validate the predictions of the TRF solutions against the measured VLBI station coordinates. To assess the quality, we computed average WRMS values from the coordinate differences as well as from estimated Helmert transformation parameters, in particular, the scale. We found that the results significantly depend on the level of process noise used in the filter. While larger values of process noise allow the TRF station coordinates to more closely follow the input data (decrease in WRMS of about 45%), the TRF predictions exhibit larger deviations from the VLBI station coordinates after 2014 (WRMS increase of about 15%). On the other hand, lower levels of process noise improve the predictions, making them more similar to those of solutions without process noise. Furthermore, our investigations show that additionally estimating annual signals in the coordinates does not significantly impact the results. Finally, we computed TRF solutions mimicking a potential real-time TRF and found significant improvements over the other investigated solutions, all of which rely on extrapolating the coordinate model for their predictions, with WRMS reductions of almost 50%.     

Satellite emission radio interferometric earth surveying series—GPS geodetic system

The satellites of the Global Positioning System (GPS) offer an important new geodetic resource making possible a highly accurate portable radio geodetic system. A concept called SERIES (Satellite Emission Radio Interferometric Earth Surveying) makes use of GPS radio transmissions without any satellite modifications. By employing the technique of very long baseline interferometry (VLBI) and its calibration methods, 0.5 to 3 cm three dimensional baseline accuracy can be achieved over distances of 2 to 200 km respectively, with only 2 hours of on-site data acquisition. The use of quasar referenced ARIES Mobile VLBI to establish a sparse fundamental control grid will provide a basis for making SERIES GPS measurements traceable to the time-invariant quasar directions. Using four SERIES stations deployed at previously established ARIES sites, allows the GPS satellite apparent positions to be determined. These apparent positions then serve as calibrations for other SERIES stations at unknown locations to determine their positions in a manner traceable to the quasars. Because this proposed radio interferometric configuration accomplishes its signal detection by cross-correlation, there is no dependence upon knowledge of the GPS transmitted waveforms which might be encrypted. Since GPS radio signal strengths are 10⁵ stronger than quasar signals, a great reduction in telecommunications sophistication is possible which will result in an order of magnitude less cost for a SERIES GPS station compared to a quasar based mobile VLBI system. The virtually all-weather capability of SERIES offers cost-effective geodetic monitoring with applications to crustal dynamics and earthquake research.     

Tropospheric parameters: combination studies based on homogeneous VLBI and GPS data

The combination of tropospheric parameters derived from different space-geodetic techniques has not been of large interest in geodesy so far. However, due to the high correlation between station coordinates and tropospheric parameters, the latter should not be neglected in combinations. This paper deals with the comparison and combination of tropospheric parameters derived from global positioning system (GPS) and very long baseline interferometry (VLBI) observations stemming from a 15-day campaign of continuous VLBI observations in 2002 (CONT02). The observation data of both techniques were processed homogeneously to avoid systematic differences between the solutions. We compared the tropospheric estimates of GPS and VLBI at eight co-location sites and found a very good agreement in the temporal behavior of the tropospheric zenith path delays (ZPD), reflected by correlation factors up to 0.98. Following this, a combination of the tropospheric parameters was performed. We demonstrate that the combination of tropospheric parameters leads to a stabilization of combined station networks. This becomes visible in the improvement of the repeatabilities of the station height components. Furthermore, the potential use of independent data from water vapor radiometers (WVRs) to validate space-technique-derived tropospheric parameters was investigated. Correlation coefficients of 0.95 or better were estimated between the tropospheric parameters of WVR and GPS or VLBI. Additionally, the utility of the tropospheric parameters for validation of local tie vectors was investigated. Both tropospheric zenith delays and tropospheric gradients were found to be very suitable to validate the height component and the horizontal components of the local tie, respectively.