GRACE Follow-On卫星的星载GNSS相位测速法

Precise GNSS phase velocity determination for GRACE Follow-On satellites

通常认为,低轨卫星的速度和加速度信息需要首先进行卫星精密定轨,再通过轨道微分法得到最终解算结果。本文基于GRACE Follow-On卫星的GPS载波相位观测数据,通过数值微分方法直接对载波进行微分,解算得到卫星的速度和加速度。基于2018-11-01—2018-11-10的GRACE Follow-On C/D卫星实测数据进行了试验,利用CODE精密星历和5 s钟差产品,结果表明,当微分器长度设置为9点时,载波相位直接法确定C和D卫星速度的3D RMS分别可达0.2276 mm/s和0.2384 mm/s(微分间隔为60 s);确定卫星加速度的3D RMS分别可达4.1μm/s^(2)和4.5μm/s^(2)(微分间隔为90 s)。载波相位直接微分法相比于运动学轨道差分法而言,无须固定模糊度,削弱了轨道历元间相关性对其微分速度和加速度的影响,可为GRACE Follow-On任务的精密定轨和重力场解算提供高精度的速度和加速度信息。

In this study,we composed the velocity and acceleration of GRACE Follow-On satellites directly estimated from the onboard carrier phase observations based on the FIR(finite impulse response)differentiator instead of the orbit differentiation method.Using the level 1B data of GRACE Follow-On from DOY 305 to 314 in 2018,CODE(Center for Orbit Determination in Europe)precise ephemeris and 5 s clock corrections,the results showed that based on the ninth-point differentiator,the 3D root mean square(RMS)of satellite C and D velocity can achieve the accuracy at 0.2276 mm/s and 0.2384 mm/s(differentiator interval=60 s);Meanwhile,the 3D RMS values of acceleration can achieve the accuracy at 4.1μm/s^(2) and 4.5μm/s^(2) for satellite C and D respectively(differentiator interval=90 s).The GNSS phase direct differentiation method does not require a fixed ambiguity,which weakens the influence of the correlation between orbit epochs,respect to the kinematic orbit difference method and provides high-precision velocity and acceleration information for gravity field model determination.