In this paper,the Earth rotation parameters are estimated with the GPS observation data from 22 IGS sites in the ITRF2005 which have high accuracy coordinates and velocities,and the solutions were compared with the IERS C04(UTC 0h) series.It shows that the difference between the two series is very small within the accuracy of the ERP estimated by IERS.In order to study the estimation of the earth rotation parameters based on COMPASS data from the tracking stations of future international COMPASS service system,observation data with the international COMPASS network of domestic stations and 2 foreign stations,together the 8 stations,were analyzed.

1 课题意义 随着卫星导航、飞行器编队等航天活动的深入开展,对星座自主时间同步和自主定轨产生了重大需求.在这种需求背景下,本课题开展星间双向时间同步方法的研究,并开展星座自主时间同步和定轨的仿真计算和分析.本课题研究成果对于发展我国卫星导航系统具有重要参考意义.

The processing of the GPS observations of the site survey at Sheshan 25-m radio telescope in August 2008 is reported. Because each session in this survey is only about six hours, not allowing the subdaily high frequency variations in the station coordinates to be reasonably smoothed, and because there are serious cycle slips in the observations and a large volume of data would be rejected during the software automatic adjustment of slips, the ordinary solution settings of GAMIT needed to be adjusted by loosening the constraints in the a priori coordinates to 10 m, adopting the "quick" mode in the solution iteration, and combining Cview manual operation with GAMIT automatic fixing of cycle slips. The resulting coordinates of the local control polygon in ITRF2005 are then compared with conventional geodetic results. Due to large rotations and translations in the two sets of coordinates (geocentric versus quasi-topocentric), the seven transformation parameters cannot be solved for directly. With various trial solutions it is shown that with a partial pre-removal of the large parameters, high precision transformation parameters can be obtained with post-fit residuals at the millimeter level. This analysis is necessary to prepare the follow-on site and transformation survey of the VLBI and SLR telescopes at Sheshan

The direct and indirect methods on predicting ionosphere are proposed in this paper.These methods are using ARIMA(p,d,q)model of the time series theory to predict ionosphere.The direct method is predicting the TEC in each node of grid forming time series.The indirect method is:Firstly,the ionospheric TEC is fitted by spherical-harmonic expansion,the fitted coefficients for different time forming time series can be obtained;and then,these time series will be analyzed by ARIMA(p,d,q)model and will be used to predict the spherical-harmonic coefficients;and finally,the ionospheric TEC will be predicted by the predicted spherical-harmonic coefficients.The TEC data in the duration of 2004 Jan 1 to 2005 Jan 31 from International GPS Service(IGS)is used to verify and compare the two methods.The results of the two methods are nearly the same in the first 12 days.In last days,the prediction of the indirect method is more accurate than the direct method. Within 20 days,the percentage of the grids number of the difference between prediction value and original value less than 3 TECU is about 80%.As time going,this percentage of the indirect method clearly descends but this percentage of the direct method descends un-couspicuously.The direct method is suitably applied to local predicting TEC while the indirect method to global predicting TEC.

The direct and indirect methods for predicting the ionospheric total electron content (TEC) by using the ARIMA (p, d, q) model in the theory of time-series analysis are proposed. The direct method predicts directly the time series composed of the TECs at the every grid point. The indirect method is: at first, to fit the ionospheric TECs with the spherical harmonics and obtain the time series of the fitting coefficients; then, to predict forward the fitting coefficients with the ARIMA (p, d, q) model in the theory of time-series analysis; and finally, to calculate the TEC for the specific time and grid point. Using the ionospheric data of the International GPS Service (IGS) in the period from 1 January 2004 to 31 January 2005, the testing and comparisons on the proposed methods are performed, the results indicate that within 12 days, the results of the two methods are basically consistent, and that for the predictions longer than 12 days, the accuracy of the indirect method is higher than the direct method. In the duration of 20 days, relative to the total ionospheric grid points, the percentage of the grid points with a prediction error less than 3 TECUs is about 80%; as the duration becomes longer, compared with the indirect method, the decline of this percentage is not apparent for the direct method. Obviously, the direct method suits the prediction of regional TECs, and the indirect method suits the prediction of global TECs.

Taking the ionospheric TEC(total electron content)data released by IGS(international GPS service)for the sample,the ionospheric TEC for the whole world is predicted by using the time series model.Different order-determining rules can lead to different predicted results in the time series prediction model;It has been proved by test that the BIC order-determining rule used in this paper is suitable for realizing the TEC prediction.The results show that for the prediction period of ten days or so,the relative precision of the TEC calculated with the time series model is high and the gird nodes,for which the relative precision of the predicted TEC is better than 60%,amount to 90 percent of the total gird nodes.

对空间飞行器精密定轨软件COMPASS的开发作了详细的需求分析,包括软件功能、定轨模式、可分析的数据类型、参数解算、运行环境等,以便为COMPASS软件系统的设计提供依据.

The radio wave used in communications at distance and navigation by satellite is affected by the ionosphere. Therefore the study on the total electron content (TEC) in the ionosphere is very important. There are some prediction models of the ionosphere. But the accuracy of prediction by them is 50% similar to 60% only. A new ionosphere model to predict total electron content is proposed. In this model the total electron content given by IGS at each node of grid is fitted by spherical-harmonic expansion. The fitted coefficients at different times form the time series, which are predicted by the ARMA(p, q) model so as that the prediction of total electron content in the ionosphere is implemented. The TEC data of IGS in 2004 and 2005 are analyzed by our method in order to predict the TEC in the geographic frame. The relative accuracy of prediction for 5 days obtained by our method is about 90%.

Based on the geometric, dynamic and reduced dynamic precise orbit determination (POD), a kinematic POD by the onboard GPS zero-differential phase observations was discussed and programmed. It applies the observations of GPS receive onboard LEO (Low Earth Orbit) and the precise GPS ephemeris of IGS rather than the complicated dynamic models and ground observations. It is simple and convenient in computation, rapid and precise in orbit determination and could provide estimations of some dynamic parameters too. However, it is unable to predict the orbit. The coefficient matrix of the normal equation is very huge and so in its reverse it is divided into sub-matrixes and then is transformed into upper-triangular. As an example of application of this new method the CHAMP data are analyzed in order to estimate the precision of POD.

On the basis of introducing Blewitt method, new idea and arithmetic were put forward on bad observations deletion, cycle-slip detection and correction, and ambiguity float solution in allusion to some questions of Blewitt method. To discussed the feasibility from error theory and to analyze it with some samples, it was tested: cycle-slip detection was more clean and more reasonable and viable after improving.

GPS data from Shanghai GPS Comprehensive and Application Network(SGCAN) in the summer of 2002 are analyzed. The Ultra-rapid orbit of IGS(IGU) is used directly in real-time processing. Reliable Precipitable Water Vapor (PWV) series can be obtained with the assistant of remote stations. Considering the effect of ocean tide, the accuracy of PWV can be improved. The difference between GPS/PVFV and Radiosonde observations is about 2mm. Comparison between the outputs of MM5 and GPS/PWV shows that GPS can be regarded as one means to real-time check up the result of MM5 numerical prediction. Continuous GPS/PWV series in the whole Meiyu season reflects the changing processes of PWV in detail before and after the onset of the Meiyu Season in the Yangtz River Delta in 2002 summer. The variations of GPS/PWV show that the onset of the Meiyu season was from southwest to northeast and completed in about 7 similar to 8 hours. The rainband moved back and forth among the Yangtz River Delta, Huaihe area and the south to the Yangtz river area in the Meiyu season. The statistics of PWV peaks and one-hour rain explain some short-term forecast ability of GPS/PWV for rainstorms. The humidity condition of numerical forecast model is optimized after GPS/PWV being interpolated to the grids of the initial field using the Cressman method. The accuracy of numerical forecast is improved. One example is provided in this paper which shows the potential of GPS/PWV in improving numerical forecast.

On the basis of current methods of cycle-slip detection and correction, a new method was discussed in this paper. Firstly, we divided the observation arc into some sub-arcs according to the discontinuous epochs and detected the cycle-slip by means of differential method, judging cycle-slip or outliers by the character of the amplification of the cycle-slip after difference and determining their location, then both the wide-lane combination and the ionosphere-free combination were used to detect and correct the cycle-slip. An example was taken to prove the validness of the method.

上海GPS综合应用网(SGCAN)是我国第一个区域性连续实时的综合性服务GPS网络,该网包括:由14个GPS基准站组成的,以上海为中心覆盖整个长江三角洲地区的GPS气象服务网;由50个基准控制点建立的上海高精度(点位精度达厘米级)三维大地测量控制网;20个基准监测点建立的上海高精度地壳形变和地面沉降监测网;另外5个GPS基准站作为上海地理信息系统(GIS)的GPS基准站,实时连续发布高精度GPS改正信息,满足整个上海地区GIS用户(包括工程测量、交通航运和公安消防等)快速实时(或准实时)的定位和导航需要.该网已于2002年6月投入正常运行,在GPS气象、地壳形变和地面沉降方面已经获得初步结果,也将为改善长江三角洲地区数值天气预报初始场和监测、治理地面沉降提供充足的信息.

Slant water vapor (SWV) measurements along GPS ray paths have the potential to be useful in reconstructing three dimensional water vapor field, which is the key problem of GPS meteorology. A direct method of estimating SWV using GPS non-difference LC observation combinations without the effect of ionosphere is presented. Comparing with Water Vapor Radiometer (WVR) measurements showed that it can get millimeter level accuracy of SWV estimated by this method every 30 seconds. The difference between the averages of SWV in 5 minutes after scaled to zenith and PWV estimated directly by GIPSY very 5 minutes is less than 2mm. SWV obtained by the this method can be used in tomography to sense the three dimensional structure of water vapor and improve the initial conditions of numerical weather forecast. It's also useful in correcting the error of GPS geodesy and radar images.

简要介绍了上海GPS综合应用网（SCGAN）情况,分析了该网从2002年6月投入正常运行后,获取的2002年入梅前后长江三角洲地区高分辨率可降水量（PWV）资料,描述了PWV所反映的长江三角洲地区的入梅过程和特点,以及把GPS/PWV同化到中尺度数值预报模式初始场中的试验。

利用GAMIT软件,采用有基准算法对乌鲁木齐南山观测基地新建GPS跟踪站GUAO的观测资料进行了归算,结果表明该站观测资料的质量是可靠的,并首次获得了该站在ITRF2000中毫米级精度的地心坐标.

Applying recent 10-year GPS measurement data from several nationside GPS networks, serveral regional GPS monitoring networks and the Asia-Pacific Regional Geodetic Project (APRGP), we give out a combined and consistent velocity field solution in ITRF97 by rotation transformation of regional GPS network results. In order to study the characteristics of present-time intra-plate crustal deformation of China, we have constructed a new present-time plate motion model named ITRF97VEL. The model can better describe present-time features of global plate motion than the geological model NNR-NUVEL1A. Based on ITRF97VEL, deformation velocities of more than 260 GPS sites are determined. The results show that the crustal motion is very inhomogenous. The crustal deformation in the west of China is far stronger and more complicated than that in the east of China, taking the N-S seismic belt of China as a boundary. The deformation velocity gradually reduces from south to north in the west of China by energy release in several W-E direction arc suture zones. The Qinghai-Xizang plateau is shortening in north-south direction and extending in west-east direction due to the strong shove of Indian plate. The shortening of about 15mm/a and 9-13mm/a is accommodated across Himalayan block and the west Tianshan, respectively. Between the longitudes of 80degreesE to 91degreesE in southern Tibet, there is E-W extension of 20.2 +/- 1.2mm/a. The slip rates of KJFZ in south Qinghai-Xizang plateau and Altun Tahg fault are 2-3 mm/a and 4-6mm/a, respectively. Our GPS results indicate that there is a shortening of less than 7 mm/a within the Longmen shan. These results support the supposition of crustal thickening.

By analyzing daily continuous data of Chinese Global Positioning System (GPS) fiducial network with 25 sites from 1999 to 2001, seasonal altitude variations with amplitude of 3–10 mm are detected. Most part of the variations can be explained by the seasonal vertical crustal movements caused by atmospheric pressure variation and mass loading redistribution of non-tidal ocean loading, snow, and soil moisture. Nevertheless, there exists a systematic discrepancy between GPS deduced result and the counterpart predicted by combining various geophysical sources. Much longer time series of GPS site coordinates and further studies are still needed to give out a reasonable interpretation for this discrepancy.

To monitor and study the crustal motion in China, some nationwide GPS networks and several regional GPS monitoring networks have been set up since 1991. Using recent 10-year GPS measurement data of about 180 sites from these networks and three-campaign GPS measurements provided by the Asia-Pacific Regional Geodetic Project (APRGP), a combined and consistent velocity field solution in ITRF2000 are obtained. In order to study the characteristics of contemporary intra-plate crustal deformation of China, we have constructed a new present-time plate motion model named ITRF2000VEL based on ITRF2000 velocity field. By calculation of total angular momentum, we find there is also net rotation in ITRF2000 like ITRF96 and ITRF97. ITRF2000VEL can better describe contemporary features of global plate motion than the geological model NNR-NUVEL1A. Taking the ITRF2000VEL motion of the Eurasia plate as the background motion, we calculated the residual velocities of all GPS sites. From these results, we can see the crustal deformations in the west of China are far stronger and more complicated than those in the east of China taking the N-S seismic belt of China as a boundary. The deformation velocity gradually reduces from south to north in the west of China by energy release in several W-E direction arc suture zones. The Qinghai-Tibet plateau is shortening in north-south direction and extending in west-east direction due to the strong shove of Indian plate. The shortening of about 15 mm/yr and 9~13 mm/yr is accommodated across Himalayan block and the west Tian Shan respectively. Within southern Tibet, between the longitudes of 80 E to 91E, there is E-W extension of 20.2 1.2 mm/yr. The slip rates of KJFZ in south Tibet and Altyn Tagh fault are 2~3 mm/yr and 4~6 mm/yr respectively. Our GPS results indicate there is a lesser than 7 mm/yr shortening within the Longmen Shan. These results support the supposition of crustal thickening.

通过归算中国GPS(全球定位系统)基准网1999～2001年近3年的观测数据, 监测到了振幅为3～ 10 mm的高程季节性变化. 并通过大气压、非潮汐海洋负荷、雪和地表水的质量负荷变化引起的地壳垂向季节性位移, 可以解释所监测到的季节性变化的大部分. 但GPS估计的季节性变化结果与质量负荷预报结果存在明显的系统性差别, 合理的物理解释有待更长的GPS站坐标时间序列的获得和更进一步的研究.