Abstract
Future space exploration missions require increased autonomy. This is especially true for navigation, where continued reliance on Earth-based resources is often a limiting factor in mission design and selection. In response to the need for autonomous navigation, this work introduces the StarNAV framework that may allow a spacecraft to autonomously navigate anywhere in the Solar System (or beyond) using only passive observations of naturally occurring starlight. Relativistic perturbations in the wavelength and direction of observed stars may be used to infer spacecraft velocity which, in turn, may be used for navigation. This work develops the mathematics governing such an approach and explores its efficacy for autonomous navigation. Measurement of stellar spectral shift due to the relativistic Doppler effect is found to be ineffective in practice. Instead, measurement of the change in inter-star angle due to stellar aberration appears to be the most promising technique for navigation by the relativistic perturbation of starlight.
Highlights
This work presents a method—referred to here as StarNAV—for using perturbations in observed starlight to autonomously navigate a spacecraft in the Solar System
The performance of velocity-only initial orbit determination (IOD) using StarNAV measurements is demonstrated for an example spacecraft in geostationary orbit (GEO)
The velocity of the spacecraft causes a change in the apparent wavelength and direction of a star as seen by sensor aboard the spacecraft
Summary
The spectrum of a star observed by a moving spacecraft is altered by cosmological redshift (due to expansion of the Universe), gravitational redshift/blueshift (due to potential fields near the source and observer), and the relativistic Doppler effect (due to kinematic velocity between the source and observer) Each of these natural phenomena contain numerous contributing effects, with the kinematic relative velocity being the most troublesome due to the active nature of stellar surfaces at short timescales. The fundamental concept of using stellar aberration for autonomous navigation was suggested in [9] This earlier work presented only a cursory analysis, considered only first-order stellar aberration effects (despite requiring measurement accuracy corresponding to third-order relativistic effects), and neglected entirely the gravitational deflection of starlight (which is orders of magnitude larger than the required measurement accuracy). The remaining sections consider the efficacy of StarNAV for navigation: Section 5 considers an instantaneous velocity fix, Section 6 considers initial orbit determination (IOD), and Section 7 considers real-time navigation with an extended Kalman filter (EKF)
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