Enabling Boomless CubeSat Magnetic Field Measurements With the Quad-Mag Magnetometer and an Improved Underdetermined Blind Source Separation Algorithm

Abstract

In situ magnetic field measurements are often difficult to obtain due to the presence of stray magnetic fields generated by spacecraft electrical subsystems. The conventional solution is to implement strict magnetic cleanliness requirements and place magnetometers on a deployable boom. However, this method is not always feasible on low-cost platforms due to factors such as increased design complexity, increased cost, and volume limitations. To overcome these problems, we propose using the Quad-Mag CubeSat magnetometer with an improved Underdetermined Blind Source Separation (UBSS) noise removal algorithm. The Quad-Mag consists of four magnetometer sensors in a single CubeSat form-factor card that allows distributed measurements of stray magnetic fields. The UBSS algorithm can remove stray magnetic fields without prior knowledge of the magnitude, orientation, or number of noise sources. UBSS is a two-stage algorithm that identifies signals through cluster analysis and separates them through compressive sensing. We use UBSS with single-source point detection to improve the identification of noise signals and iteratively-weighted compressed sensing to separate noise signals from the ambient magnetic field. Using a mock CubeSat, we demonstrate in the lab that UBSS reduces four noise signals producing more than 100 nT of noise at each magnetometer to below the expected instrument resolution (5 nT at 65 Hz). Additionally, we show that the integrated Quad-Mag and improved UBSS system works well for 1U, 2U, 3U, and 6U CubeSats in simulation. Our results show that the Quad-Mag and UBSS noise cancellation package enables high-fidelity magnetic field measurements from a CubeSat without a boom.Plain Language SummaryMeasuring magnetic fields in their natural space environment, or “in situ,” can be difficult because of interference from other artificial magnetic fields. These other magnetic fields, called “stray magnetic fields,” are often created by the electrical subsystems on the spacecraft. The usual way to solve this problem is by making sure the spacecraft is very clean magnetically and by putting special sensors on a long boom that sticks out from the spacecraft. However, this solution can be difficult to use on small spacecraft, such as CubeSats, because it makes the spacecraft more expensive and harder to design. In this study, we propose an alternative solution by using a special sensor called Quad-Mag and a method to cancel out noise called Underdetermined Blind Source Separation (UBSS). This new solution allows accurate measurements without the need for a long arm and it works well even on CubeSats. The combination of Quad-Mag and UBSS technology has the potential to revolutionize CubeSat magnetometry, offering valuable opportunities for space research and exploration.Key PointsThe Quad-Mag CubeSat magnetometer combined with the UBSS noise cancellation technique enable high-fidelity magnetic field measurements without the need for a boomQuad-Mag instrument equipped with four magneto-inductive magnetometers has a resolution two times better than that of any single sensorUBSS algorithm can remove stray magnetic field noise without prior knowledge of the magnitude, orientation, or number of noise sources