Star-based Navigation in the Outer Solar System

This paper investigates an autonomous navigation method for spacecraft operating in the outer solar system, up to 250 AU from the Sun, using the parallactic shifts of nearby stars. These measurements enable estimation of the spacecraft trajectory while distant stars provide attitude information through conventional star-pattern matching. Stellar observation models are developed, accounting for delta light-time, parallax, and aberration effects. Navigation performance is assessed using two approaches: (1) a least-squares estimator using simultaneous multi-star measurements, and (2) a Kalman filter processing sequential single-star observations along deep-space trajectories. Monte Carlo simulations on trajectories representative of Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons missions show sub-AU position accuracies at 250 AU, and velocity accuracies better than 0.00004 AU/day, under realistic spacecraft and instrumentation uncertainties. These values correspond to relative errors below 0.4% in position and velocity with respect to the reference trajectories. Although less precise than radiometric tracking, this performance can support navigation in the outer solar system without reliance on Earth. When ground-based navigation remains necessary, this approach can be employed during long cruising phases, lowering the number of ground contacts. The method additionally shows potential for future missions venturing farther from the Sun.