arXiv subjects

Silvia Giuliatti Winter

Publications and source records attributed to Silvia Giuliatti Winter.

5 recordsLinked to original sources

arXiv2024

Orbital maneuvers for a space probe around Titania

For most space missions, it is interesting that the probe remains for a considerable time around the mission target. The longer the lifetime of a mission, the greater the chances of collecting information about the orbited body. In this work, we present orbital maneuvers that aim to show how to avoid a collision of a space probe with the surface of Titania. Through an expansion of the gravitational potential to the second order, the asymmetry of the gravitational field due to the coefficient $C_{22}$ of Titania, the zonal coefficient $J_2$, and the gravitational perturbation of Uranus are considered. Two models of coplanar bi-impulse maneuvers are presented. The first maneuver consists of transferring an initial elliptical orbit to a final circular orbit, and the second has the objective of transferring an initial elliptical orbit to a final orbit that is also elliptical. The lag in the inclination and semi-major axis of the orbits is investigated before performing the maneuvers. To point out the best scenarios for carrying out the maneuvers, a study is presented for different points of an orbit where transfers could be made. In addition, a maneuver strategy is presented to correct the variation of the periapsis argument. The results show that maneuvers performed a few days after integration are more economical than maneuvers performed later, a few days before the collision. The economy of the maneuvers is also demonstrated through an analysis of the ratio of the increase in speed to the lifetime.

astro-ph.EP↗

arXiv2023

Mapping and maneuvering long-term natural orbits around Titania, a satellite of Uranus

In this work, we present the results of a set of numerical simulations carried out to obtain long-duration orbits for a probe around Titania, Uranus' largest satellite. We also propose orbital maneuvers to extend the lifetime of some orbits. Titania's $J_2$ and $C_{22}$ gravitational coefficients and Uranus' gravitational perturbation are considered. The analysis of lifetime sensitivity due to possible errors in $J_2$ and $C_{22}$ values is investigated using multiple regression models. Simulations were performed for eccentricity equal 10-4, and lifetime maps were constructed. The results show that low-altitude orbits have longer lifetimes due to the balance between the disturbance of Uranus and the gravitational coefficients of Titania. The results also show that non-zero values of periapsis longitude ($ω$) and ascending node longitude ($Ω$) are essential to increase lifespan. Furthermore, the results indicate that the most economical maneuver occurs for final orbits of radius equal to 1050 km, this is observed for all inclination values.

astro-ph.EP↗

arXiv2023

Exploring the recycling model of Phobos formation: rubble-pile satellites

Phobos is the target of the return sample mission Martian Moons eXploration by JAXA that will analyze in great details the physical and compositional properties of the satellite from orbit, from the surface and in terrestrial laboratories, giving clues about its formation. Some models propose that Phobos and Deimos were formed after a giant impact giving rise to an extended debris disk. Assuming that Phobos formed from a cascade of disruptions and re-accretions of several parent bodies in this disk, and that they are all characterized by a low material cohesion, Hesselbrock & Milton (2017) have showed that a recycling process may happen during the assembling of Phobos, by which Phobos' parents are destroyed into a Roche-interior ring and reaccreted several times. In the current paper we explore in details the recycling model, and pay particular attention to the characteristics of the disk using 1D models of disk/satellite interactions. In agreement with previous studies we confirm that, if Phobos' parents bodies are gravitational aggregates (rubble piles), then the recycling process does occur. However, Phobos should be accompanied today by a Roche-interior ring. Furthermore, the characteristics of the ring are not reconcilable with today`s observations of Mars' environment, which put stringent constraints on the existence of a ring around Mars. The recycling mechanism may or may not have occurred at the Roche limit for an old moon population, depending on their internal cohesion. However, the Phobos we see today cannot be the outcome of such a recycling process.

astro-ph.EP↗

arXiv2021

Long-term Dynamical Evolution of Pallene (Saturn XXXIII) and its Diffuse, Dusty Ring

The distinctive set of Saturnian small satellites, Aegaeon, Methone, Anthe, and Pallene, constitutes an excellent laboratory to understand the evolution of systems immersed in co-orbital dusty rings/arcs, subjected to perturbations from larger satellites and non-gravitational forces. In this work, we carried out a comprehensive numerical exploration of the long-term evolution of Pallene and its ring. Through frequency map analysis, we characterised the current dynamical state around Pallene. A simple tidal evolution model serves to set a time frame for the current orbital configuration of the system. With detailed short and long-term N-body simulations we determine whether Pallene is currently in resonance with one or more of six of Saturn's major moons. We analysed a myriad of resonant arguments extracted from the direct and indirect parts of the disturbing function, finding that Pallene is not in mean motion resonance from the present up to 5~Myr into the future; nonetheless, some resonant arguments exhibit intervals of libration and circulation at different timescales and moon pairings. We studied the dynamical evolution of micrometric particles forming the ring, considering gravitational and non-gravitational forces. Non-gravitational forces are responsible for particles vertical excursions and outward migration. By estimating the satellite's mass production rate, we find that Pallene could be responsible for keeping its ring in steady-state only if it is mainly composed of large micrometre-sized particles. If mainly composed of particles with a few micrometres for which Pallene is the only source, the ring will spread out, both radially and vertically, until it finally disappears.

astro-ph.EP↗

arXiv2017

Long-term Evolution and Stability of Saturnian Small Satellites: Aegaeon, Methone, Anthe, and Pallene

Aegaeon, Methone, Anthe, and Pallene are four Saturnian small moons, discovered by the Cassini spacecraft. Although their orbital characterization has been carried on by a number of authors, their long-term evolution has not been studied in detail so far. In this work, we numerically explore the long-term evolution, up to $10^5$ yr, of the small moons in a system formed by an oblate Saturn and the five largest moons close to the region: Janus, Epimetheus, Mimas, Enceladus, and Tethys. By using frequency analysis we determined the stability of the small moons and characterize, through diffusion maps, the dynamical behavior of a wide region of geometric phase space, $a$ vs $e$, surrounding them. Those maps could shed light on the possible initial number of small bodies close to Mimas, and help to better understand the dynamical origin of the small satellites. We found that the four small moons are long-term stable and no mark of chaos is found for them. Aegaeon, Methone, and Anthe could remain unaltered for at least $\sim0.5$Myr, given the current configuration of the system. They remain well-trapped in the corotation eccentricity resonances with Mimas in which they currently librate. However, perturbations from nearby resonances, such as Lindblad eccentricity resonances with Mimas, seem responsible for largest variations observed for Methone and Anthe. Pallene remains in a non-resonant orbit and it is the more stable, at least for 64 Myr. Nonetheless, it is affected by a quasi-resonance with Mimas, which induces long-term orbital oscillations of its eccentricity and inclination.

astro-ph.EP↗