Accuracy analysis of the ephemerides of the Galilean satellites

TLDR: In this article, an analysis of the time corrections derived for Sampson's theory, concludes that the dominant error in the mean longitudes of the mean-square root of the period is due to the definition of time, which was determined by the observations which he used in constructing the theory.

Abstract: Known discrepancies between Sampson's Theory and observations of the Galilean satellites produce in plane errors of about 1200 km. Since the mean longitude is responsible for most of the discrepancy a simple time correction may be used to significantly reduce these errors. An analysis of the time corrections derived for Sampson's Theory, concludes that the dominant error in the mean longitudes results from Sampson's definition of time, which was determined by the observations which he used in constructing the theory. Imposition of the libration constraint results in changes to the time corrections which are less than the standard deviation of those quantities. The individual eclipse observational errors are shown to be proportional to the square root of the period. With improved star catalogs, the attainable accuracy of the ephemerides of the Galilean satellites is about 100 km from photographic plates versus about 200 km for eclipse observations.-