2016A&A...596A..37R

Context. Accurate positional measurements of planets and satellites are used to improve our knowledge of their orbits and dynamics, and to infer the accuracy of the planet and satellite ephemerides.
Aims. In the framework of the European FP7 ESPaCE program, we provide the positions of Saturn and its main satellites taken with the US Naval Observatory 26-inch refractor from 1974 to 1998.
Methods. We measured 526 astrophotographic plates with the digitizer of the Royal Observatory of Belgium and reduced them through an optimal process that includes image, instrumental, and spherical corrections using the UCAC4 catalog to provide the most accurate equatorial (RA, Dec) positions.
Results. We compared the observed positions of the satellites with the theoretical positions from INPOP13c and DE432 planetary ephemerides and from NOE-6-2015-SAT and SAT375 satellite ephemerides. The mean post-fit rms residuals in equatorial positions range from ±68mas for the Titan observations or 400km at Saturn, to ±100mas for the Hyperion observations or 600km at Saturn. The mean post-fit rms intersatellite residuals range from ±46mas for the Rhea-Titan observations or 280km at Saturn, to ±72mas for the Hyperion-Titan observations or 430km at Saturn.