By telescopic tracking, we have established that the orbit of the trans-neptunian object (2000 CR 105 ) has a perihelion of ≃44 AU, and is thus outside the domain controlled by strong gravitational close encounters with Neptune. Because this object is on a very large, eccentric orbit (with semimajor axis a ≃216 AU and eccentricity e ≃0.8) this object must have been placed on this orbit by a gravitational perturbation which is not direct gravitational scattering off of any of the giant planets (on their current orbits). The existence of this object may thus have profound cosmogonic implications for our understanding of the formation of the outer Solar System. We discuss some viable scenarios which could have produced it, including long-term diffusive chaos and scattering off of other massive bodies in the outer Solar System. This discovery implies that there must be a large population of trans-neptunian objects in an 'extended scattered disk' with perihelia above the previously-discussed 38 AU boundary.

We present BVRI colors of 13 Jovian and 8 Saturnian irregular satellites obtained with the 2.56m Nordic Optical Telescope on La Palma, the 6.5m Magellan Baade Telescope on La Campanas, and the 6m MMT on Mt. Hopkins. The observations were performed between December 2001 to March 2002. Nearly all of the known irregular satellites can be divided into two distinct classes based on their colors. One, the grey color class, has the similar colors to the C-type asteroid, and the other, the light red color class, has colors similar to P/D-type asteroids. We also find at least one object, the Jovian irregular J XXIII Kalyke, that has colors similar to the red colored Centaurs/TNOs, although its classification is unsecure.We find that there is a correlation between the physical properties and dynamical To which of these two clusters the remaining Saturnian irregulars with inclinations close to 174• belong is not clear from our analysis, but determination of their colors should help constrain this.We also show through analysis of possible fragmentation and dispersion of the six known Uranian irregulars that they most likely make up two clusters, one centered on U XVI Caliban and another centered on U XVII Sycorax. We further show that, although -4 -the two objects have similar colors, a catastrophic fragmentation event creating one cluster containing both U XVI Caliban and U XVII Sycorax would have involved a progenitor with a diameter of ∼ 395km. While such an event is not impossible it seems rather improbable, and further we show that such an event would leave 5-6 fragments with sizes comparable or lager than U XVI Caliban. Given that the stable region around Uranus has been extensively searched to limiting magnitudes far beyond that of U XVI Caliban. The fact that only U XVI Caliban and the larger U XVII Sycorax have been found leaves us with a distribution not compatible with a catastrophic event with such a large progenitor. The most likely solution is therefore two separate events creating two Uranian dynamical clusters.

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The Rosetta spacecraft has been successfully launched on 2nd March 2004 to its new target comet 67 P/Churyumov-Gerasimenko. The science objectives of the Rosetta Radio Science Investigations (RSI) experiment address fundamental aspects of cometary physics such as the mass and bulk density of the nucleus, its gravity field, its interplanetary orbit perturbed by nongravitational forces, its size and shape, its internal structure, the composition and roughness of the nucleus surface, the abundance of large dust grains, the plasma content in the coma and the combined dust and gas mass flux. The masses of two asteroids, Steins and Lutetia, shall be determined during flybys in 2008 and 2010, respectively. Secondary objectives are the radio sounding of the solar corona during the superior conjunctions of the spacecraft with the Sun during the cruise phase.The radio carrier links of the spacecraft Telemetry, Tracking and Command (TT&C) subsystem between the orbiter and the Earth will be used for these investigations. An Ultrastable oscillator (USO) connected to both transponders of the radio subsystem serves as a stable frequency reference source for both radio downlinks at X-band (8.4 GHz) and S-band (2.3 GHz) in the one-way mode. The simultaneous and coherent dual-frequency downlinks via the High Gain Antenna (HGA) permit separation of contributions from the classical Doppler shift and the dispersive media effects caused by the motion of the spacecraft with respect to the Earth and the propagation of the signals through the dispersive media, respectively.The investigation relies on the observation of the phase, amplitude, polarization and propagation times of radio signals transmitted from the spacecraft and received with ground station antennas on Earth. The radio signals are affected by the medium through which the signals propagate (atmospheres, ionospheres, interplanetary medium, solar corona), by the gravitational influence of the planet on the spacecraft and finally by the performance of the various systems involved both on the spacecraft and on ground.

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