New ephemerides of outer planetary satellites

ABSTRACT Ephemerides of planetary satellites require regular updates to take into account new observations of the satellites. Such revision has been all the more necessary in the case of outer planetary satellites, since a number of new moons have been discovered recently. Thus, we present updated versions of the ephemerides of the outer planetary satellites. The problem and the methodology for estimating ephemeris accuracy are discussed. Comparison with the Jet Propulsion Laboratory (JPL) ephemerides proves that the accuracy depends largely on the distribution of the observations. We give examples where, for a few satellites, the O−C residuals increase sharply at time intervals lying significantly beyond the time interval of observations used to generate the ephemerides. This fact alone indicates that there is an urgent need for new observations. Besides the ephemerides of moons, which can be accessed online via the MULTI-SAT server, we provide orbital parameters for the recently discovered faint satellites of Jupiter and Saturn. The problems discussed in this work are important for planning space observations of the outer satellites by future space missions like the European Space Agency (ESA) JUpiter ICy moons Explorer (JUICE) and National Aeronautics and Space Administration (NASA) Europa Clipper missions.