Report on satellites for the period July 2005 - June 2008 (J.E. Arlot) 1) Activities of the Working Group on Natural Planetary Satellites The main goal of the Working Group was to gather astrometric observations made during the triennum as well as old observations not yet published in the Data base. The WG encouraged the making of new observations in order to maintain the ephemerides of all satellites. A Spring School was organized in China in order to teach the observational techniques of natural satellites to students and young astronomers. New theoretical models of the motion of the satellites and fit of the current models to new observations were used in order to make ephemerides of all the planetary satellites with tools useful for observations such as configurations. These ephemerides named MULTISAT are available at www.imcce.fr/sat or at lnfm1.sai.msu.ru/neb/nss/nssephme.htm. Original ephemerides are also available on JPL's Horizons ephemerides at http://ssd.jpl.nasa.gov/ and on MPC ephemerides for irregular satellites at http://cfa-www.harvard.edu/iau/NatSats/NaturalSatellites.html. A workshop has been held in Paris on November 2006 for organizing campaigns of observations. The problem of a standard format for the astrometric observations of the natural satellites raised and will have to be solved during the next triennum. 2) Selected works performed during the triennum a) The Martian satellites The data from MEX and MGS were analysed and information on the tidal dissipation within Mars were deduced from observation of the shadow of Phobos on Mars (Bills et al.,Journal of Geophysical Research, 110, E7, p.7004) Numerically integrated orbits for Phobos and Deimos were produced from fits to all observations including MEX and MGS (Lainey et al., Astronomy and Astrophysics, 465, p. 1075, and Jacobson, LPI Contribution 1377). Jacobson's orbits were produced in support of the MRO Project and incorporated MRO imaging observations as well. b) The Galilean satellites Observations of the 1997 mutual events were published (Arlot et al. Astronomy and Astrophysics, 451, p.733-737) and astrometric data were deduced from these photometric observations (Emelyanov and Gilbert, Astronomy and Astrophysics, 453, p.1141-1149) A new theory was published (Lainey et al. Astronomy and Astrophysics, 456, p.783-788) and studies have been made on the tidal dissipation in Io (Lainey and Tobie, Icarus 179, p.85), on the rotation of Io and Europa (Henrard, Icarus 178, p.144 and Celestial Mechanics and Dynamical Astronomy vol.91, p.131, vol.93, p.101) and on the free and forced obliquities of the Galileans (Bills, Icarus 175, p.233). c) the Inner satellites of Jupiter Several papers were published on Amalthea after the fly-by of Galileo on the gravity field (Weinwurm, Advances in Space Research 38, p.2125-2130) and on the density of Amalthea (Anderson et al., Science 308, p.1291). Results were obtained from Cassini observations (Cooper et al., Icarus 181, 223) d) the Outer satellites of Jupiter Observations were reported (Veiga, Astronomy and Astrophysics 453, p.349). New orbits were calculated using all observations (Emelyanov A&A 435, 1173). The mass of Himalia was determined from perturbations on other satellites using ground-based observations (Emelyanov, A&A 438, L33). Theoretical works were performed on an analytical theoretical model (Beauge' et al. AJ 131, p.2299) and the dynamical evolution of this family of satellites (Christou, Icarus 174, 215). e) the Main satellites of Saturn The data of the Cassini probe provide many results on the gravity field, the shape (Jacobson et al., AJ 132, p.711 and p.2520). Star occultations by Titan were reported (Sicardy et al. JGR 111, S91) as astrometric observations by the HST (French et al. PASP, 118, p.246). A new analysis technique for mutual events data was published (Ramirez et al. Astron. Astrophys. 448, 1197) as a new image-processing technique for astrometry (Peng, MNRAS, 359, 15, p.97) f) the faint inner satellites of Saturn The hypothetical satellites seen by Cassini led to study of their stability (Mourao et al., MNRAS 372, p.1614). New orbits of the inner satellites have been deduced from Cassini and old observations (Spitale et al., AJ, 132, p.692; Jacobson et al., AJ 135, p.261). The orbit of the newly discovered satellite Anthe was fit to Cassini data (Cooper et al., Icarus, 195, p.765). g) the outer satellites of Saturn A new orbit of Phoebe was calculated using all the available observations (Emelyanov, A&A 473, 343). An analysis of albedo was made using Cassini data (Porco et al., Science 307, P.1237) as spectrophotometry, useful to characterize the families of satellites and their formation (Buratti et al., Icarus, 175, p.490) h) the satellites of Uranus Astrometric observations of the main satellites were performed (Izmailov et al, Solar System Research, 41, p.42), of Puck (Veiga and Bourget Astron. Astrophys. 454, p.683), mutual events were predicted (Arlot et al., Astron. Astrophys. 456, p.1173, Christou, Icarus, 178, p.171)) and observed (Hidas et al., MNRAS 384, p.38) Satellites U-12 to 17 have been named (CBET 323, 2005). New ephemerides for the main satellites were produced from fits to all but the mutual event data (Jacobson, BAAS, 39(3), 453). i) the satellites of Neptune Astrometric observations of Triton were performed (Qiao et al. MNRAS 376, p.1707) as predictions of eclipses of Nereide (Mallama, Icarus 187, p.620). Constraints on the orbital evolution of Triton was published (Matija and Gladman, Astrophysical Journal 626, 113) and a study has been made of the disturbing function on the inner satellites (Yokoyama, Advances in Space Research, vol.36, p.569) followed by the modelling of the precession of the equator of Neptune (Nascimento et al., 35th COSPAR Scientific Assembly, held on 18-25 July 2004, in Paris, France). New ephemerides for Triton, Nereid, and Proteus were produced by fitting all observations through the opposition of 2007 (Jacobson, BAAS, 40(2), p.296). NOTE: Qiao's observations contain systematic errors are are unusable. j) the satellites of asteroids These objects are in fact binary or triple objects, the center of mass of the system being not inside the largest object. Nowadays a lot of binary (or triple) systems have been discovered. No data base of astrometric observations is available and no ephemeris is published. k) the rings The rings of the giant planets have been extensively observed by the space probes Galileo and Cassini and also by the HST. The dynamics are studied and the systems ring-moon have also been studied. The ring-moon system of Uranus has been studied (Showalter and Lissauer, Science 311, p.973, Gibbard et al., Icarus 174, p.253) l) miscellaneous The observability of the Natural planetary satellites has been explored by Tanga and Mignard (Proceedings of the Gaia symposium, Paris, 2004). The capture of irregular satellites of the giant planets has been studied (Nesvorny et al., AJ 133, p.1962) as their chaotic behaviour (Mel'Nikov A. V. and Shevchenko I. I., Solar System Research 39, P.322).