Investigation of geomagnetic reference models based on the Iridium^{circledR } constellation

Samuel Califf,Sarah Vines,Kenneth Rock,Kan Liou,Arnaud Chulliat,Patrick Alken,Brian Anderson,Robin Barnes

doi:10.1186/s40623-022-01574-w

Abstract

The World Magnetic Model (WMM) is a geomagnetic main field model that is widely used for navigation by governments, industry and the general public. In recent years, the model has been derived using high accuracy magnetometer data from the Swarm mission. This study explores the possibility of developing future WMMs in the post-Swarm era using data from the Iridium satellite constellation. Iridium magnetometers are primarily used for attitude control, so they are not designed to produce the same level of accuracy as magnetic data from scientific missions. Iridium magnetometer errors range from 30 nT quantization to hundreds of nT errors due to spacecraft contamination and calibration uncertainty, whereas Swarm measurements are accurate to about 1 nT. The calibration uncertainty in the Iridium measurements is identified as a major error source, and a method is developed to calibrate the spacecraft measurements using data from a subset of the INTERMAGNET observatory network producing quasi-definitive data on a regular basis. After calibration, the Iridium data produced main field models with approximately 20 nT average error and 40 nT maximum error as compared to the CHAOS-7.2 model. For many scientific and precision navigation applications, highly accurate Swarm-like measurements are still necessary, however, the Iridium-based models were shown to meet the WMM error tolerances, indicating that Iridium is a viable data source for future WMMs.Graphical

Highlights

Introduction TheEarth’s core produces a large-scale magnetic field that is the dominant signal as measured by magnetometers on the surface of the Earth and in low-Earth orbit
The Earth’s core produces a large-scale magnetic field that is the dominant signal as measured by magnetometers on the surface of the Earth and in low-Earth orbit. Main field models such as the International Geomagnetic Reference Field (IGRF) (Alken et al 2021b) and World Magnetic Model (WMM) (Chulliat et al 2021), are used as references for navigation purposes, with applications ranging from aviation maps to spacecraft attitude control
We considered three norms for our model: the minimum energy norm (Shure et al 1982), the norm which minimizes the rms of Br over the core mantle boundary (CMB) (Shure et al 1982), and the minimum curvature of Br over the CMB (Smith and Wessel 1990)

Summary

Introduction

Introduction TheEarth’s core produces a large-scale magnetic field that is the dominant signal as measured by magnetometers on the surface of the Earth and in low-Earth orbit. In this study we use a version of the Iridium magnetometer data that has been corrected for spacecraft contamination signals, but has not been calibrated relative to a reference model.

Results

Conclusion