Highlights • A notable spurious signal appears for the 3-plane BDS MEO and Galileo constellations. • Y-pole rate derived from Galileo is affected by three orbital planes and station distribution. • Unoptimized models, orbital planes, station distribution impact ERPs derived from BDS. • Systematic bias in Earth rotation parameters derived from BDS and Galileo is verified.

Abstract The Earth Rotation Parameters (ERPs) are estimated with the BeiDou Navigation Satellite System (BDS), GPS, and Galileo observations from approximately 100 selected International Global Navigation Satellite System (GNSS) Service (IGS) tracking stations around the world. The results are compared with the IGS final products (IGSF) and the International Earth Rotation and Reference Systems Service (IERS) series 14C04 at 12 UTC. The accuracy of the ERPs derived from the GPS-only reaches the IGS accuracy level. The standard deviations of the differences in the X-pole, Y-pole, and Length of Day (LOD), compared with the IGSF, are 23 $\mu as$, 20 $\mu as$, and 7 $\mu s/day$, respectively. Meanwhile, the standard deviations of the differences in the X-pole, Y-pole, and LOD, in contrast with IERS 14C04, are 28 $\mu as$, 25 $\mu as$, and 9 $\mu s/day$, respectively. Similarly, the ERPs are estimated using BDS-only and Galileo-only observations from approximately 100 selected IGS stations. For ERPs derived from BDS Medium Earth Orbit (MEO-only) satellites, the standard deviations of the differences in the X-pole, Y-pole, and LOD, compared with the IGSF, are 76 $\mu as$, 53 $\mu as$, and 19 $\mu s/day$, respectively, and 75 $\mu as$, 55 $\mu as$, and 19 $\mu s/day$, respectively, compared with IERS 14C04. Likewise, for the ERPs derived from Galileo-only observations, the standard deviations of the differences in the X-pole, Y-pole, and LOD, compared with the IGSF, are 48 $\mu as$, 31 $\mu as$, and 12 $\mu s/day$, respectively, and 48 $\mu as$, 30 $\mu as$, and 14 $\mu s/day$, respectively, in contrast with IERS 14C04. Despite the three orbital planes, tracking station distribution, and unoptimized models for the BDS MEO satellites, these results are close to the IGS accuracy level. The impact of spurious system-specific signals on these solutions is investigated using spectral analysis, a notable spurious signal appears for the 3-plane BDS MEO and Galileo constellations. The pronounced peaks at the frequencies of 2.97 cycles per year (cpy) for Polar Motion and Polar Motion rate, 1.98 cpy for LOD are significantly larger than those from GPS.