An Innovative Technique for Reaction wheel Interference Separation in Satellite Magnetic Field Signals

Natural magnetic field measurement is essential for discovering fundamental physical mechanisms in space. Both the CSES mission and the DEMETER satellite equipped with the search coil magnetometer to observe the magnetic field waves. The CSES mission’s search coil magnetometer was developed by the School of Space Sciences Department of Beihang University. But the accuracy of these measurements is often degraded by artificial interference from reaction wheels on satellites. These wheels produce complex harmonic interference, often overlapping with the natural signal in both time and frequency domain, which makes it difficult to observe natural signals.

Traditional methods usually construct filters to separate interference. Advanced signal technologies have focused on reducing interference using self-adaptive signal decomposition methods in either time or frequency domain. In this field, Finley and Robert have used singular spectrum analysis to remove interference from in situ magnetic field data from the CASSIOPE/Swarm-Echo mission. But they did not settle the time-frequency overlap problem. In fact, most signal decomposition methods do not work well. These methods usually damage the natural signal because the overlapping areas remain indistinguishable.

In this paper, a novel method named the Instantaneous Phase Discontinuity (IPD) method is proposed to address this issue. Based on the sensitivity of instantaneous phase to variation of signal frequency, this method utilizes the discontinuities in the phase function to identify overlapping time-frequency regions. Subsequently, the natural signal within the overlapping region is carefully separated through frequency band contraction and envelope correction. IPD holds broad application prospects. As an example, IPD effectively separates interference from the time-frequency overlapping regions while preserving the integrity of natural signals when applied to data obtained from the CSES mission.