Extension of low-thrust propulsion to the autonomous coplanar circular restricted four body problem with application to future Trojan Asteroid missions

An Autonomous Coplanar Circular Restricted Four Body Problem (CRFBP) is considered, where the massless body is a low-thrust spacecraft. 'Natural' and 'artificial' (i.e. created with the use of continuous low-thrust propulsion) equilibrium solutions are identified, that have the potential to be exploited in future science missions. Results show that, with zero thrust, there are unstable equilibrium points close to the third primary. However, artificial equilibrium points, displaced from the natural ones, can be generated with the use of constant low-thrust. Furthermore, these points are proved to be stable in certain regions about the third primary mass. This is particularly advantageous since it means that it would be possible to continuously maintain a spacecraft about these strategic observation points, close to the smaller primary, without the need for state feedback control. The Sun-Jupiter-Trojan Asteroid-Spacecraft system is considered, as a particular case of the Autonomous Coplanar CRFBP. Curves of artificial equilibrium points are then identified. Furthermore, the stability analysis of these points reveals the region where they are stable. In this region four bounded orbits close to the Asteroid are proved to exist, that can be reached and maintained with a constant low-thrust lower than 10µN

THE VALUE OF DEEP LEARNING FOR LANDSCAPE REPRESENTATION COMPARISON BETWEEN SEGMENTATION IMAGES MAPS AND GIS

Abstract. Landscape refers to the qualities of a place, the result of a structural, territorial and environmental component, and the attribution of meanings, which is certainly the fundamental issue of the interpretative process. Percepire etymologically derives from "per", which means "by means of, through", and "capere", which translates as "to take", "to collect" (information, sensory data), "to learn". Since images are derived from the territory, it is of first interest to propose a comparison between representations derived from automated processes on photographs and the synthetic data interpreting the territory inherent in the plans developed with GIS in order to obtain a more precise perceptual analysis. The emergence of new tools for the processing and reproduction of data offers new opportunities for the knowledge and representation of the landscape, in architectural and urban contexts, and the integrative support that these processes can bring to the representation of the qualities of a place have to be reinterpreted in a Spatial Information Dataset in order to make synthetic and intelligible information. Identifying specific themes by questioning these data through criteria and placing at the centre the capacity of the digital environment in its mathematisation to compare data, transforming them into information, in an automated process is aimed at the exploitation of Big Data and the full replicability of the procedure. In this way, it is possible to enter into the analysis of the quality of space, of that notion of landscape concieved as "that part of the territory perceived by the population that lives it"

Studio delle potenzialità delle piattaforme UAV nel campo del rilievo dei Beni Culturali

L'uso di piattaforme aeree senza pilota a bordo (UAV) sta diventando sempre più frequente nel campo del rilievo fotogrammetrico soprattutto grazie ai numerosi vantaggi che tali sistemi presentano rispetto alle classiche riprese di fotogrammetria aerea. Il lavoro condotto descrive i primi risultati ottenuti utilizzando sistemi UAV per il rilievo di Beni Culturali. Lo studio è stato svolto acquisendo alcuni dataset relativi a siti archeologici; tali dataset presentano caratteristiche differenti in relazione ai velivoli utilizzati, alle caratteristiche dei voli ed all’estensione delle aree rilevate. Il lavoro ha permesso di eseguite delle prime valutazioni sulla precisione metrica degli orientamenti e sul livello di dettaglio ottenuto dai modelli 3D e dalle ortofoto

Influence of the dynamic classification of asteroids on observation astrometric errors: a statistical analysis

The ephemerides of minor planets are computed on the basis of astrometric observations. The asteroid orbit determination process requires these observations to be properly weighted to take into account the expected accuracy of the data. If not directly provided by the observers, the weights are, in general, computed after a station-specific statistical analysis on the observation residuals, where the influence of external factors such as epoch of observation, magnitude, and employed catalogue has been proven. In this paper, we perform a statistical analysis on observation residuals of the major surveys taking into account a new factor, i.e. the dynamical classification of asteroids, to understand whether the observation quality may have a dependence on the different type of observed object. If an influence is actually found, then it will be possible to develop a new weighting system based on these results. The weights will be easily applicable once one knows the asteroid orbit. In particular, four stations have been found having different qualities depending on whether they are observing near-Earth asteroids or main-belt asteroids. Moreover, the cross-correlation between the dynamic classification and epoch, magnitude, and catalogue is investigated, as well as the influence of these factors on observations’ quality

The course of the cystic artery during laparoscopic cholecystectomy

Proper recognition of the particular structures that form the triangle of Calot is essential for the proper and safe performance of laparoscopic cholecystectomy. Proper recognition, ligation, and cut of the cystic duct and cystic artery with branches (dorsal and ventral) remain an integral condition for the removal of the gallbladder. Calot’s triangle, as an orientation structure, determines the most common location of the cystic artery. The triangle of Calot is one of the most variable regions of the abdomen in terms of anatomy. The aim of this study was to evaluate how important for surgery is the detailed anatomical recognition of the main branches of the cystic artery in Calot’s triangle during laparoscopic cholecystectomy. Relations of the main branches of the cystic artery were evaluated in 88 patients that underwent laparoscopic cholecystectomy at the Department of General Surgery of the District Specialistic Hospital of Lublin. The anatomical relations of cystic duct and artery were classified into typical and variant types. Significantly more frequently variants of cystic artery were observed in women. However, the time of the procedure was not significantly related with the type of cystic artery

Defining principles for mobile apps and platforms development in citizen science

Apps for mobile devices and web-based platforms are increasingly used in citizen science projects. While extensive research has been done in multiple areas of studies, from Human-Computer Interaction to public engagement in science, we are not aware of a collection of recommendations specific for citizen science that provides support and advice for planning, design and data management of mobile apps and platforms that will assist learning from best practice and successful implementations. In two workshops, citizen science practitioners with experience in mobile application and web-platform development and implementation came together to analyse, discuss and define recommendations for the initiators of technology based citizen science projects. Many of the recommendations produced during the two workshops are applicable to citizen science project that do not use mobile devices to collect data. Therefore, we propose to closely connect the results presented here with ECSA’s Ten Principles of Citizen Science

Analytical method for perturbed frozen orbit around an Asteroid in highly inhomogeneous gravitational fields : A first approach

This article provides a method for nding initial conditions for perturbed frozen orbits around inhomogeneous fast rotating asteroids. These orbits can be used as reference trajectories in missions that require close inspection of any rigid body. The generalized perturbative procedure followed exploits the analytical methods of relegation of the argument of node and Delaunay normalisation to arbitrary order. These analytical methods are extremely powerful but highly computational. The gravitational potential of the heterogeneous body is rstly stated, in polar-nodal coordinates, which takes into account the coecients of the spherical harmonics up to an arbitrary order. Through the relegation of the argument of node and the Delaunay normalization, a series of canonical transformations of coordinates is found, which reduces the Hamiltonian describing the system to a integrable, two degrees of freedom Hamiltonian plus a truncated reminder of higher order. Setting eccentricity, argument of pericenter and inclination of the orbit of the truncated system to be constant, initial conditions are found, which evolve into frozen orbits for the truncated system. Using the same initial conditions yields perturbed frozen orbits for the full system, whose perturbation decreases with the consideration of arbitrary homologic equations in the relegation and normalization procedures. Such procedure can be automated for the first homologic equation up to the consideration of any arbitrary number of spherical harmonics coefficients. The project has been developed in collaboration with the European Space Agency (ESA)

The Role of Citizen Science in Promoting Ocean and Water Literacy in School Communities: The ProBleu Methodology

Human activities continue to degrade oceanic, coastal and inland waters. The generational change in the role of society in actively looking after the health of water resources can be achieved through the expansion of ocean and water literacy in schools. The Network of European Blue Schools established under the EU4Ocean Coalition for Ocean Literacy has improved ocean and water literacy; however, this Network needs to grow and be supported. Here, we present ProBleu, a recently funded EU project that will expand and support the Network, partly through the use of citizen science. The core of the proposed methodology is facilitating school activities related to ocean and water literacy through funding calls to sustain and enrich current school activities, and kick-start and support new activities. The outcomes of the project are anticipated to have widespread and long-term impacts across society, and oceanic, coastal and inland water environments

Low thrust propulsion in a coplanar circular restricted four body problem

This paper formulates a circular restricted four body problem (CRFBP), where the three primaries are set in the stable Lagrangian equilateral triangle configuration and the fourth body is massless. The analysis of this autonomous coplanar CRFBP is undertaken, which identies eight natural equilibria; four of which are close to the smaller body, two stable and two unstable, when considering the primaries to be the Sun and two smaller bodies of the solar system. Following this, the model incorporates `near term' low-thrust propulsion capabilities to generate surfaces of articial equilibrium points close to the smaller primary, both in and out of the plane containing the celestial bodies. A stability analysis of these points is carried out and a stable subset of them is identied. Throughout the analysis the Sun-Jupiter-Asteroid-Spacecraft system is used, for conceivable masses of a hypothetical asteroid set at the libration point L4. It is shown that eight bounded orbits exist, which can be maintained with a constant thrust less than 1:5 10􀀀4N for a 1000kg spacecraft. This illustrates that, by exploiting low-thrust technologies, it would be possible to maintain an observation point more than 66% closer to the asteroid than that of a stable natural equilibrium point. The analysis then focusses on a major Jupiter Trojan: the 624-Hektor asteroid. The thrust required to enable close asteroid observation is determined in the simplied CRFBP model. Finally, a numerical simulation of the real Sun-Jupiter-624 Hektor-Spacecraft is undertaken, which tests the validity of the stability analysis of the simplied model