星间基线高精度确定是分布式干涉合成孔径雷达（InSAR）系统完成科学任务的重要保证，受星载全球定位系统（GPS）接收机连续跟踪弧段短、个别弧段共视GPS卫星个数少或模糊度固定成功率低、频繁轨道机动等因素影响，分布式InSAR高精度基线确定仍有不可靠的风险。通过多机构产品互比来识别基线精度较差的时间段，降低不可靠风险，并通过多机构产品融合进一步提高基线精度。选用重力反演与气候实验（GRACE）卫星数据进行实验，国防科技大学（NDT）和西安测绘研究所（CHS）采用不同的基线处理软件和简化动力学策略，保证了各自的基线产品具有一定的独立性。实验表明，多机构互比对可以有效识别基线精度较差的时间段，NDT和CHS的基线产品之间具有很好的一致性，互比对残差的均方根（RMS）在R、T、N方向分别为0.7、0.9、0.7 mm，二者之间没发现明显系统偏差，大约97.86%的基线三维互比对残差量级在2 mm以内。两个机构基线产品融合后发现可进一步降低基线产品中的随机波动误差，K/Ka波段测距（KBR）系统校核结果表明融合基线产品精度较NDT基线产品提高8.97%，较CHS基线产品提高29.21%。
Precise determination of the baseline of the distributed Interferometric Synthetic Aperture Radar (InSAR) satellite system is a prerequisite for completion of scientific missions; however, reliability of the baseline determination is often affected by some unfavorable factors, such as shorter continuous carrier phase tracking arcs of the satellite-borne Global Positioning System (GPS) receiver, few visible GPS satellites from formation flying satellites or low success rate of ambiguity resolution, and frequent orbit maneuvers. In this paper, we try to identify the time when the baseline accuracy is lower by inter-agency comparison, and to improve the accuracy and reliability of the baseline by inter-agency fusion. The GPS observation data of Gravity Recovery and Climate Experiment (GRACE) satellites are processed by the National University of Defense Technology (NDT) and Xi'an Research Institute of Surveying and Mapping (CHS) using different software packages and reduced-dynamic baseline solutions to guarantee independence of the generated baseline products. The results show that inter-agency comparison can be used to identify the time during which the accuracy of the baseline determined by one agency is lower than that of the other. A high consistency is found between results of the NDT and CHS, with Root Mean Square (RMS) being about 0.7, 0.9, 0.7 mm in the radial, along-track, and out-of-plane components, respectively. Around 97.86% of differences between the 3-dimensional GRACE relative position obtained from the NDT and CHS in is less than 2 mm, indicating that there is no obvious systematic deviation between them. Furthermore, it is shown that fusion of the baseline products of the two agencies can reduce the error of random fluctuations, with the precision validated by K/Ka-Band Ranging (KBR) observations of the fused baseline products being improved by 8.97% and 29.21% compared to the NDT and CHS products, respectively.
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