DEMETER卫星ISL离子密度数据一致性检验

Consistency Validation of the Ion Density Data Obtained by the ISL Payload Onboard DEMETER Satellite

中国地震电磁监测卫星计划的首颗地球物理场探测卫星"张衡1号"于2018年2月2日成功发射,目前正在进行在轨测试,数据验证工作亟待展开.为配合此项工作,本文以法国DEMETER卫星朗缪尔探针(ISL)载荷观测数据为例,对因存在问题而被弃之不用的离子密度数据展开大规模数据的计算、分析和验证工作.通过对离子密度数据自身时空一致性、离子密度与电子密度数据随太阳活动的周期及趋势一致性以及离子密度与电子密度在不同空间、时间的一致性计算检验,认为:离子密度数据具有很好的时空一致性,可以反映在不同时空尺度下随太阳活动的周期和趋势性相对变化规律;以电子密度作为参考,离子密度可能存在系统性偏差,这个偏差随昼夜、时空而变化,但由于离子密度与电子密度在不同时空尺度都保持高度一致的相对变化规律,这种偏差不会影响对数据的相对变化研究.进一步的数据模拟分析表明偏差由常数系统误差以及调制于其上的各种周期成分构成,其中常数系统误差是主要偏差,与数据表现出的随太阳活动变化的统计规律相符.由于这种系统差异的存在,离子密度与电子密度间轻微相对变化会使得它们的比例系数发生明显变化,从而有利于从大量数据中发现一些具有特殊规律的情况.本文的研究结果对于地震电测监测试验卫星的数据验证工作具有参考意义.

The first satellite of China Seismo-Electromagnetic Satellite mission(CSES),also called Zhangheng-1,which is the first geophysical field measurement satellite in China,was launched successfully on February 2,2018.The satellite is under in-orbit test now and data validation work will be carried out soon.To cope with this work,data computation,analysis and validation are carried out using the discarded Ion density data measured by the Langmuir Probe(ISL)on onboard the French DEMETER Satellite.Computation and analysis are conducted through the spatio-temporal consistency of the ion density data,periodic and trend consistency between ion density and electron density with the variation of solar activity,and the relationship consistency between ion density and electron density in different spatio-temporal scale.The conclusions are:the ion density data itself has a very good spatio-temporal consistency and can reflect the periodic and trend variation with solar activity in different spatio-temporal scales.Taking electron density as reference,systematic bias may exist between the data of ion density and electron density.Moreover,the bias varies with day and night,space and time.However,this bias will not affect the study of the relative data variation due to the highly relative variation consistency between ion density and electron density in difference spatio-temporal scales.Further analysis based on data simulation shows that the bias is composed of a constant and various periodic components modulated on it,and the constant bias is the major deviation.This error model is consistent with the statistical law shown in the data as it changes with solar activity.In addition,because of this bias,a slight change between ion density and electron density may cause an obvious change in their ratios,which will be helpful to find some special situations from the large amount of measurement.The results of this paper can be used as a reference in the data validation work of the CSES satellite.