Nonlinear Two-Stage Kalman Filter for in-Orbit Calibration of Magnetometers

Magnetometers are commonly utilized for attitude determination control systems on low Earth orbit (LEO) small satellite. The scale factor and bias of the magnetometer must be determined in order to appropriately estimate the orientation of the satellite in space. The bias error and scale factor error are combined to form equivalent no-steady bias noise, which is removed from magnetometer measurements as bias noise. For in-orbit estimate of magnetometer biases and scale factors, a Nonlinear Two-Stage Kalman Filter (NTSKF)-based technique is presented. Each iteration of the estimation process has two stages: the first stage uses the Kalman filter to estimate equivalent magnetometer biases as well as three state parameters; the second stage uses a newly suggested modification to the Kalman filter to estimate three scale factors.