Interplanetary Autonomous Navigation Using Visible Planets

An interplanetary autonomous navigation system using only onboard star tracker is proposed and numerically tested. The idea is to point the star tracker to a visible known planet and, using an angle-only space-based initial orbit determination (IOD) method, provide the initial guess to an extended Kalman filter (EKF) for subsequent more-accurate, filtered orbit estimation. Method Pn has been selected as the space-based IOD method. Because of large distances and velocities involved, Pn and EKF estimations include two corrections: one due to the finite velocity of light, known as space-time correction, and another due to the observer's velocity, known as starlight aberration. Using Earth as the visible planet, numerical simulations have been included to validate the proposed method. The interplanetary trajectory of the observer was selected a few million kilometers from Earth. Position and velocity estimation convergence has been provided.