中文摘要：

GPS接收机差分码偏差（Differential Code Bias,DCB）是利用COSMIC低轨卫星观测值反演电离层总电子含量TEC的一项重要误差源.本文将COSMIC卫星轨道高度以上的电离层作为一个单层,采用球谐函数来参数化电离层TEC值,并利用最小二乘法同时估算电离层球谐系数和DCB参数.运用这种方法对2012年12月份的所有COSMIC卫星GPS接收机DCB进行了解算,并与COSMIC数据分析与档案中心CDAAC提供的产品进行了比较.实验结果表明：在2012年12月期间,估计的接收机DCB与CDAAC结果符合的较好,二者DCB变化趋势相近,DCB差值的RMS值在2TECU以内,且最大绝对差值小于3TECU;此外,本文计算的接收机DCB估计误差主要分布在0.2～0.4TECU之间,具有较高的内符合精度.

英文摘要：

GPS receiver differential code bias（DCB）is an important error source in inversing ionospheric total electron content（TEC）using COSMIC LEO satellite observations.In this paper,the ionosphere above COSMIC satellite orbit altitude is assumed to be concentrated on a single layer and the TEC is parameterized using spherical harmonic expansion,and then we estimate the ionospheric spherical harmonic coefficients and DCB parameters with least square method.The entire COSMIC GPS receiver DCBs in December 2012are calculated and compared to the products provided by COSMIC Data Analysis and Archival Center（CDAAC）.The result shows that estimated receiver DCBs match better with CDAAC products：the variation trend of DCBs is similar,the RMS of DCBs differences is lower than 2TECU and maximum absolute difference is less than 3TECU in December 2012.In addition,the estimated errors of receiver DCBs calculated in this paper are mainly distributed in 0.2～0.4TECU suggesting the inner precision is higher.