For various precise navigational applications using Indian NavIC system, it is imperative to have an accurate estimation of the ionospheric line‐of‐sight total electron content (TEC). In dual frequency TEC estimation from code and carrier phase measurements, the error is mainly caused by the satellite and receiver differential instrumental biases, which can be several TEC units. The reason for the existence of these biases is that the signals experience different delays within the satellite and receiver hardware at the two frequencies S1 and L5 of NavIC system. These biases are not stable over the time, maybe due to aging or change in the environment of the satellites and receiver. In this paper, the dynamics of the estimated biases of different satellites of NavIC system and receiver are presented, based on the data collected over 19 months time at Dehradun (Lat.31.26°N, Long.77.99°E), India. Five state Kalman filter algorithm was used for the estimation of differential biases. The initial receiver bias required to run Kalman filter algorithm was determined by applying fitted receiver bias (FRB) technique. The initial satellite biases needed for the purpose were supplied by Space Applications Centre (SAC), Indian Space Research Organization (ISRO), Ahmedabad, India.

中文翻译：

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用卡尔曼滤波估计NavIC卫星和接收机差分仪器偏差的时间变异性

对于使用印度NavIC系统的各种精确导航应用，必须准确估算电离层视线总电子含量（TEC）。在从代码和载波相位测量得出的双频TEC估计中，误差主要是由卫星和接收机的差分仪器偏差引起的，该偏差可能是几个TEC单位。存在这些偏差的原因是，信号在NavIC系统的两个频率S1和L5处在卫星和接收器硬件中经历了不同的延迟。这些偏差在一段时间内不稳定，可能是由于老化或卫星和接收器环境的变化所致。本文介绍了NavIC系统和接收机的不同卫星的估计偏差的动力学，基于印度Dehradun（北纬31.26°，东经77.99°）过去19个月中收集的数据。五态卡尔曼滤波算法用于估计差分偏差。运行卡尔曼滤波算法所需的初始接收器偏置是通过应用拟合接收器偏置（FRB）技术确定的。为此目的所需的初始卫星偏差是由印度艾哈迈达巴德印度空间研究组织（ISRO）的空间应用中心（SAC）提供的。