张衡一号卫星VLF电磁场数据高精度时间同步校正研究

我国首颗地震电磁监测试验卫星张衡一号（ZH-1）已在轨稳定运行3周年，获取了海量宝贵的电磁波场、等离子体参量等一手观测资料。然而随着电磁场数据定标校检与科学应用的不断深入，发现若要进一步提升ZH-1电磁场观测对空间环境不同信号的溯源能力，加深对电离层、等离子体层波动传播与产生机制的理解，亟需解决数据中存在的两个主要问题：首先是因频率域传递函数校正方法的不足造成的变化磁场波形不连续；其次是因高采样率电场与变化磁场授时精度与时间标记等不同而造成VLF频段数据时间不同步。本项目针对这两个问题，拆解传递函数校正过程，克服人为截断、未加窗造成的频谱泄露、栅栏效应等问题以提升波形数据质量，其次开展基于生成对抗网络的时频图像降噪算法适用性研究，从时间域和频率域开展电场和变化磁场高精度时间同步研究，提出一套电磁场高精度时间同步校正算法，优化ZH-1卫星VLF电磁场波形和频谱数据处理算法，提高数据产品质量。

ZH-1 satellite, also the China Seismo-Electromagnetic Satellite, has been in orbit for three years and has obtained valuable first-hand data of electromagnetic wave field and plasma parameters. However, with the deepening of calibration and scientific application of electromagnetic data, it is found that to further improve the ability to trace different sources of signals in the space environment and deepen the understanding of the propagation and generation mechanism of ionospheric and/or plasma wave, two main problems in the current data must be solved: first, the correction of transfer function correction in the frequency domain; secondly, the time synchronization problem of VLF band caused by the difference of timing accuracy and time mark strategy between electric field detector (EFD) and search coil magnetometer (SCM), both with extremely high sampling rate. Therefore, aiming at solving the above two problems, this project will re-examine the transfer function correction process, overcoming the problems of artificial truncation, spectrum leakage, and picket fence effect caused by un-windowing, to improve the quality of waveform data. Meanwhile, with the research of the applicability of denoising algorithm on time-frequency graphs based on Generative Adversarial Network (GAN), the study on the high-precision time synchronization of EFD and SCM both in time and frequency domain. This project will provide a basic reference for improving the electromagnetic data quality，optimizing the data processing method of the ZH-1 satellite, and accumulating more advantages of data processing technology for subsequent electromagnetic satellites.