Star-based Navigation in the Outer Solar System

Abstract

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.

Figures (7)

• Figure 1: Parallactic shift of nearby stars located at (a) 5 ly and (b) 10 ly, considering spacecraft positions within 250 AU from the Sun, and (c) aberration effect for velocities up to 30 km/s ($\beta \approx 10^{-4}$). The angle between the heliocentric spacecraft position vector and the star direction with respect to the SSB is denoted $\alpha$, while the angle between the velocity vector and the star direction is denoted $\psi$. Parallax and aberration values given in arcseconds.
• Figure 2: Heliocentric trajectories of the representative Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons spacecraft in the J2000 reference frame. The Sun is denoted with a yellow circle, while the current spacecraft positions at the time of writing are indicated by black dots. Planetary orbits and the ecliptic plane are included for reference.
• Figure 3: Position estimation in a least squares sense along the (a) VG-1, (b) VG-2, (c) PR-10, (d) PR-11, and (e) NH mission trajectories. The estimation considers the parallax and aberration effects in the line-of-sight directions to nearby stars. The nearby stars are assumed to be tracked simultaneously along the mission trajectories.
• Figure 4: Kalman filter outputs in terms of sample run error and filter covariance bounds for position error ($\delta x$, $\delta y$, $\delta z$) and velocity error ($\delta v_x$, $\delta v_y$, $\delta v_z$) components for the VG1 mission trajectory in the J2000 reference frame.
• Figure 5: Sample errors and numerical covariance bounds across Monte carlo runs for VG-1, VG-2, PR-10, PR-11, and NH trajectories. Results shown in terms of position and velocity norm errors and covariance bounds in the J2000 reference frame. A total of 1000 samples have been run per mission.