Estimation Of SLR Station Coordinates By Using LEO Satellite Co-locations

With a variety of space geodetic techniques establishing their own Earth reference frames and the technique-dependent systematic effects,the combination of solutions from different techniques is hard to accomplish.The inter-technique link is the terrestrial ties obtained from ground geodetic measurements of reference points for different space geodetic instruments.Combination of GNSS and SLR observations using satellite co-locations is possible and important.In this paper,the LEO satellite is used as space co-locations the for GNSS/SLR technology,which realizes the coordinate geometric solution of SLR station and gives a mature solution.The specific work is as follows:(1)This paper proposes a method based on low-orbit satellites as a satellite-based GNSS/SLR co-locations and presents a three-dimensional coordinate geometric solution method for SLR stations based on spaceborne GNSS technology.Based on the GNSS and SLR observation data of LEO satellite,the iterative least squares estimation of SLR station coordinates is established and derived,and the orbit interpolation and error correction involved in the solution process are analyzed The specific calculation methods and processing strategies are given.(2)We investigated the performance of the method for the estimation of SLR station coordinates by applying it to process GRACE-A data in January-December,2012.The GRACE-A was taken as the fast-moving stations to complete the estimation of SLR station coordinates.The distribution of SLR observations and the classical SLR residuals analysis method is applied to estimate range biases and timing offset.These stations,which collected sufficient number of SLR NPs,agree with SLRF2014 with the mean level of 31.8 mm.(3)Considering the limited SLR observation data of a single LEO satellite,the paper adds a number of LEO satellite combination solving modes to estimate the position of the SLR station.One month of SLR and GNSS observations of four satellites of HY-2A,JASON-2 and GRACE-A/B were selected to participate in the solution.According to the different observation conditions of different satellite SLR stations,the Helmert variance component estimation method is used to make reasonable weight distribution of the observation data after adjustment.And compared with the direct use of the iterative least squares estimation results,the results show that the solution of the reasonable allocation of the weight of the observation data by post-processing is better than the direct solution.In this paper,the SLR station estimation result with reasonable observation quantity is compared with SLRF2014,and the average agreement level is 26.4 mm,which is more accurate than the single-star mode.Due to the increase in the number of observation satellites,the number of SLR stations radiated by LEO satellites has increased,the observation data is also richer,and the geometrical distribution of observation data of each station is more reasonable,and the solution results are more reliable and stable.