Search

Context. In 2009, the Sun and the Earth passed through the equatorial plane of Jupiter and therefore the orbital planes of its main satellites. It was the equinox on Jupiter. This occurrence made mutual occultations and eclipses between the satellites possible. Experience has shown that the observations of such events provide accurate astrometric data able to bring new information on the dynamics of the Galilean satellites. Observations are made under the form of photometric measurements, but need to be made through the organization of a worldwide observation campaign maximizing the number and the quality of the data obtained. Aims. This work focuses on processing the complete database of photometric observations of the mutual occultations and eclipses of the Galilean satellites of Jupiter made during the international campaign in 2009. The final goal is to derive new accurate astrometric data. Methods. We used an accurate photometric model of mutual events adequate with the accuracy of the observation. Our original method was applied to derive astrometric data from photometric observations of mutual occultations and eclipses of the Galilean satellites of Jupiter. Results. We processed the 457 lightcurves obtained during the international campaign of photometric observations of the Galilean satellites of Jupiter in 2009. Compared with the theory, for successful observations, the r.m.s. of O-C residuals are equal to 45.8 mas and 81.1 mas in right ascension and declination, respectively; the mean O-C residuals are equal to -2 mas and -9 mas in right ascension and declination, respectively, for mutual occultations; and -6 mas and +1 mas in right ascension and declination, respectively, for mutual eclipses. © ESO, 2014.

The large number and all-sky distribution of quasars from different surveys, along with their presence in large, deep astrometric catalogs, enables us to build of an optical materialization of the International Celestial Reference System (ICRS) following its defining principles. Namely: that it is kinematically non-rotating with respect to the ensemble of distant extragalactic objects; aligned with the mean equator and dynamical equinox of J2000; and realized by a list of adopted coordinates of extragalatic sources. Aims. The Large Quasar Reference Frame (LQRF) was built with the care of avoiding incorrect matches of its constituents quasars, homogenizing the astrometry from the different catalogs and lists in which the constituent quasars are gathered, and attaining a milli-arcsec global alignment with the International Celestial Reference Frame (ICRF), as well as typical individual source position accuracies higher than 100 milli-arcsec. The LQRF contains J2000 referred equatorial coordinates, and is complemented by redshift and photometry information from the LQAC. It is designed to be an astrometric frame, but it is also the basis for the GAIA mission initial quasars' list, and can be used as a test bench for quasars' space distribution and luminosity function studies. The LQRF is meant to be updated when new quasar identifications and newer versions of the astrometric frames used are realized. In the later case, it can itself be used to examine the relations between those frames., Published in Astronomy and Astrophysics, v505 n1 p385-404, Oct 2009. Prepared in collaboration with Observatorio do Valongo/UFRJ, Brazil; Observatoire de Paris/SYRTE, France; US Naval Observatory, Washington, DC; INAF/Osservatorio Astronomico di Torino, Italy, and Centro Universitario Estadual da Zona Oeste, Brazil.