GPS卫星钟差分析、建模及仿真

卫星钟差是卫星导航系统中的一项重要误差源,本文根据IGS观测数据分析GPS卫星铷钟和铯钟的噪声特性,并对星钟误差进行建模和仿真.首先采用修正Allan方差表征和分析了GPS卫星上不同种类原子钟随机噪声的时域特性;然后基于最小二乘分段拟合确定了卫星钟差确定性分量的时差、频差、线性频漂参数值;对于多项式拟合后的残差部分,利用随机噪声幂律谱模型建立了随机性分量误差模型;最后利用修正Allan方差反演的方法模拟产生了各噪声分量的独立随机序列并进行合成;对合成序列与原始数据进行了对比分析以验证本文所提出建模与仿真方法的正确性.

Analysis,modeling and simulation of GPS satellite clock errors

The satellite clock error is an essential error source for a navigation satellite system.This paper analyses the noise characteristics of the Rb/Cs clocks onboard GPS satellites based on IGS observations,and establish the model of clock error simulation.First,different Rb/Cs clocks are characterized and analyzed using modified Allan variance in the time-domain.Next,the time offset,frequency offset and linear frequency drift parameters are determined using a piecewise least-square polynomial fitting method.And the residual random noises after the polynomial fitting are modelled by a power law spectrum.Finally,an Allan variance decomposition and inversion method is proposed to generate the independent random sequence and then the sequences are superposed together.The synthesized clock error sequence is compared with the original data to validate the modeling and simulation methodology.