Improving Satellite Positioning By Measuring Eclipse Times

More than forty years after its introduction, Simplified General Perturbation Theory No. 4 (SGP4) is still currently in use as the de facto standard in orbit propagation and in generating Two-Line Elements (TLEs). Unfortunately, the positioning error that results from the generated TLEs have remained relatively unchanged and continue to increase with larger TLE update intervals. This paper investigates an approach in analyzing truth data to help in possibly minimizing the errors associated with generated TLEs. The current resulting positioning errors are permissible for general tracking of satellites and pass scheduling; however, the errors that result from SGP4 alone can cause some limitations if used in other applications. This is not necessarily a challenge for large satellites that can afford to include certain instruments to help keep positioning errors low, but due to the power, volume, and cost limitations of small satellites, this can become problematic as there are not as many sensors that can fit within the small form factor. Therefore, shadow time characteristics for Low-Earth Orbit (LEO) satellites will be examined to hopefully improve TLE accuracies by incorporating measured shadow time.Aerospace Engineerin