Analysis of Orbit Determination Error Impact on Clutter Doppler Frequency for Space‐Based Early Warning Radar

ABSTRACT

The accuracy of clutter Doppler frequency in space‐based early warning radar (SBR) directly determines moving target detection performance, and satellite orbit determination error is an important cause of clutter Doppler deviation. Taking the satellite position and velocity in the Geocentric Celestial Reference System (GCRS) as the core variables, this paper derives the analytical expression for clutter Doppler frequency through co‐ordinate transformations from GCRS to the International Terrestrial Reference System (ITRS) and then to the North‐East‐Zenith (NEZ) local coordinate system. The multi‐variate function gradient analysis method is used to quantitatively reveal the influence laws of GCRS position and velocity errors on Doppler frequency. Results indicate that satellite velocity error is the linear dominant term of Doppler variation with a constant gradient magnitude of 2/ λ , and only the velocity component along the satellite–ground line‐of‐sight contributes to frequency shift. Satellite position error acts as a nonlinear modulation term, whose gradient magnitude is inversely proportional to the satellite–ground distance and coupled with satellite velocity. Under typical SBR operating parameters and BeiDou receiver orbit determination errors, a velocity error of 0.1 m/s causes a Doppler deviation below 1 Hz, and a 10 m position error results in a deviation less than 1.6 Hz, both negligible in practice. This research study clarifies orbit determination error propagation characteristics and provides a theoretical foundation for clutter Doppler accuracy control and SBR orbit precision design.