低轨导航增强卫星的轨道状态型星历参数设计

导航增强卫星从高轨拓展到低轨,需要设计可靠的低轨道LEO广播星历参数。GLONASS广播星历模型能够利用9个状态参数高精度描述30min内中高轨卫星的摄动运动,但不能直接用于低轨卫星。为了适应LEO的摄动力的短期快变化,设计了基于轨道状态型的21参数广播星历模型。分析了低轨卫星主要摄动力的短期变化规律,选取了二次多项式和基于轨道半周期的三角函数来补偿大气阻力等主要摄动在3个方向上的累计。基于星历拟合试验讨论了拟合参数个数、拟合时段和数据间隔对500~1200km轨道高度的LEO圆轨道的拟合精度影响。试验表明,当拟合时段为20min(约1/5个轨道周期)时,轨道高度大于700km的近圆轨道,拟合用户距离误差(FURE)精度优于0.05m;高度为1000km时,FURE平均精度达到0.03m。

Orbital List Ephemerides Design of LEO Navigation Augmentation Satellite

A set of reliable LEO (low earth orbit)broadcast ephemerides is required to be designed specifically if LEOs,with current GEOs,are also utilized as navigation augmentation satellites.The classical nine state parameters-based GLONASS-type broadcast ephemerides model can only represent precisely the 30-minute orbital motions of the medium and high earth orbiters.To directly deal with LEOs,a modified 21-parameter broadcast ephemerides model is proposed.First,the short-term variations of the main perturbation forces of LEOs are analyzed.Then a set of simple quadratic polynomials and harmonic functions is adopted to compensate mathematical ly atmospheric drag perturbation and other effects.A thoroughly simulation for the LEOs of altitude 500~1200 km is given to demonstrate the impact of the numbers of ephemerides parameters,the length of the fitting arcs and the sample rates on the fitting precision.The results of 20-minute fitting arc (approximately 1/5 of orbital period)show that the average RMS of the fitting user range error (FURE)is less than 0.05 m for LEOs higher than 700 km and within 0.03 m for LEOs of altitude 1000 km.