Autonomous Spacecraft Orbit Determination from Incident Light Intensity via Eclipse Transient Timing

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Autonomous Spacecraft Orbit Determination from Incident Light Intensity via Eclipse Transient Timing

Fitzgerald, Riley M.

Autonomous orbit determination methods requiring minimal hardware, computational power, and external reference are desirable for small, low-cost spacecraft, or as a backup on larger craft. This paper presents a set of methods for orbit identification and estimation using only scalar measurements of the incident sunlight intensity, which should be available to most spacecraft without the need for additional dedicated hardware. By using these data to time the duration and transients of eclipse, a spacecraft may maintain a provided orbital estimate or develop a new orbital estimate from scratch. The presented methods use a novel sun-referenced orbit parameter conversion to identify candidate orbits, and an unscented Kalman filter based on the simplified general perturbations model and an atmosphere-corrected eclipse transient model to refine estimates and identify the correct candidate. These navigation methods are tested against public two-line element set data and are shown to provide continuous position estimates with an orbit-averaged error typically on the order of several kilometers in a variety of low-Earth-orbit geometries. So long as the spacecraft is in an eclipsing orbit about a known body, the algorithms described herein can provide orbital state estimates even to satellites without dedicated navigation hardware or external tracking.