A method for direct in-space thrust estimation from low-acceleration orbital maneuvers

Abstract

This paper presents a method for performing direct in-space thrust estimation for low-acceleration propulsion systems using measurements of the spacecraft’s position taken during an orbital maneuver. The method is based on the ensemble Kalman update which does not require linearization of the spacecraft dynamics nor does it require Gaussian distributions for parameter uncertainties and measurement noise, allowing for a more general approach to thrust estimation. In addition, modeling error, such as that caused by the truncation of a spherical-harmonics representation of the Earth’s gravitational field, can be explicitly accounted for by representing the error with Gaussian processes. Simulated experiments show that uncertainty in the propulsive acceleration magnitude on the order of 0.1 mum/s^2 (1sigma) can be achieved at an orbit altitude of approximately 410 km with temporally-sparse measurements even in the presence of uncertain atmospheric drag, and Monte Carlo analysis demonstrates the consistency of the inference results. Trends in the estimate of the propulsive acceleration with the true acceleration value are explored empirically and theoretically in order to allow for generalization of the results. The outcome of this work is a systematic approach to direct in-space thrust estimation that can support the final steps of development for future in-space electric propulsion systems or the calibration of a thruster during a mission.