基于GNSS的分布式InSAR编队星间基线高精度确定与校准

For the combination of the satellite formation flying technique and the SAR interferometry technique, the distributed InSAR system becomes a kind of new conceptual radar systems with enormous potential, however, the inter satellite baseline needs to be determined accurately, whose precision even reaches 1mm. The high precision determination of the inter satellite baseline faces many challenges, such as the formation-keeping maneuvers, system errors due to satellite mass center variation and antenna phase center variation, and so on, and is hard to attain directly. We hope to solve this problem by improving data processing method in practice. This project researches the high precision determination and calibration of the inter satellite baseline for distributed InSAR system base on spaceborne GNSS. The key technologies include highly precise post-facto relative satellite positioning in the circumstance of many formation-keeping maneuvers, the double-difference phase integer ambiguity estimation with high success rate and robustness, the effects of satellite mass center variation modeling and eliminating, relative phase center variations self-calibration for formation GNSS antennas, spaceborne BDS and GPS measurements fusing, baseline errors calibration and compensation, etc., which can improve the precision and robustness of baseline estimation. Analysis of baseline determination precision will be also performed, which can offer the support for the top precision requirement design of baseline measurement system. Furthermore, this project will develop a high precision inter satellite baseline determination software platform based on BDS and GPS measurements with self-owned intellectual property rights, and this software platform will verify the correctness and efficiency of the key technologies.

分布式InSAR系统将卫星编队与InSAR技术相结合，是一种具有巨大潜力的新概念雷达体制。该系统对星间基线的测量精度要求尤为苛刻，达到了1mm。编队构型保持机动、卫星质心与天线相位中心变化系统误差等对星间基线的高精度确定提出了挑战，难以直接实现，实际中需要结合数据处理方法的创新来解决这个问题。本项目研究基于GNSS的分布式InSAR编队星间基线高精度确定与校准技术，主要研究编队构型保持机动情况下的高精度事后相对定位、高成功率且可靠的双差相位整周模糊度固定、卫星质心变化影响建模消除、编队GNSS天线“相对”相位中心变化自校准、星载BDS/GPS测量数据融合处理、基线误差校准与补偿等关键技术，提高星间基线估计精度和可靠性，并对基线确定精度进行分析，为星间测量系统的顶层指标设计提供支撑。开发一套基于BDS/GPS的分布式InSAR编队星间基线高精度确定软件平台，验证核心关键技术的正确性和有效性。

本项目研究基于GNSS的分布式InSAR编队星间基线高精度确定与校准技术，取得的主要进展包括：提出一种机动条件下的编队基线确定新方法，在机动条件下仍能获得GRACE编队全弧段、优于1mm的高精度基线解；发明一种模糊度固定新方法，避免传统方法使用M-W组合时伪码、相位被等权组合，模糊度固定成功率提高5%；提出一种编队导航天线“相对”相位中心变化估计新方法，GRACE编队基线确定精度提高40%，达到0.68mm；研究高精度姿态确定系统误差建模补偿技术，首次利用我国试验卫星数据完整地提取国产星敏感器低频误差，并发现其轨道重复特性，补偿后光轴夹角精度显著提高；研究联合GNSS与地面控制点的基线误差校准技术，提出一种抑制斜距误差影响的新方法；针对北斗GEO卫星低仰角相位数据中的频繁小周跳问题，提出一种增强周跳探测新方法，采用GARCH模型自适应调整周跳探测阈值，提高北斗周跳探测可靠性；研究BDS+GPS融合，融合后基线精度较GPS、BDS单系统分别提高29.73%、21.21%；研究多机构比对融合方法，通过互比对识别基线精度较差弧段，降低单机构基线产品不可靠风险，且多机构融合后的基线产品精度较单机构分别提高8.97%、29.21%；自主研制定轨软件NUDTTK，对GRACE双星编队绝对定轨三维精度达到3cm，相对定轨KBR检核精度达到0.7mm，模糊度固定成功率达到92%，达到国际同类优秀软件同等水平。受基金资助取得的成果主要包括：共发表学术论文29篇，其中SCI检索13篇，EI检索7篇，获会议优秀论文、最佳口头报告等4项；获军队科技进步一等奖2项；授权国家发明专利1项；培养博士研究生5人，硕士研究生4人；邀请国内外专家来校学术交流6次，参加国内外学术会议14次。