Precise GNSS phase velocity determination for GRACE Follow-On satellites

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 0.227 6 mm/s and 0.238 4 mm/s (differentiator interval=60 s); Meanwhile, the 3D RMS values of acceleration can achieve the accuracy at 4.1 μm/s2 and 4.5 μm/s2 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. © 2021, Surveying and Mapping Press. All right reserved.