Precise Line-of-Sight Modelling for Angles-Only Relative Navigation

This work presents a precise analytical model to reconstruct the line-of-sight vector to a target satellite over time, as required by angles-only relative navigation systems for application to rendezvous missions. The model includes the effects of the geopotential, featuring: the analytical propagation in the mean relative orbital elements (up to second-order expansion), the analytical two-way osculating/mean orbital elements’ conversion (second-order in J 2 and up to a given degree and order of the geopotential), and a second-order mapping from the perturbed osculating elements’ set to the local orbital frame. Performances are assessed against the line-of-sight reconstructed out of the precise GPS-based positioning products of the PRISMA mission. The line-of-sight modelled over a far-range one day long scenario can be fitted against the true one presenting residuals of the order of ten arc-seconds, which is below the typical sensor noise at far-range

Trame cosmopolite. Minorità, migrazioni e città intorno al Mediterraneo. Figure, attraversamenti, comunità = Cosmopolitan weaves. Minorities, migrations and cities around the Mediterranean. Figures, crossings, communities

Following the suggestion proposed by the philosopher Pascal Bruckner in his essay Le vertige de Babel (2000) on the capacities of societies to integrate and mobilise a "plurality of belongings", the project of RiMe Issues 10/I and 10/II n.s. was initiated. The reading of cosmopolitanism proposed here, free from the uncritical praise of a harmonious society, without tensions or conflicts between groups, communities or minorities, should be seen as an investigation and questioning of the social and pragmatic capacities that societies have (or have had) to construct forms of coexistence and inclusion in the identity and cultural complexity of the Mediterranean context. An interdisciplinary research project called “Cosmomed”, which involved some fifteen researchers, including geographers, historians, anthropologists and archivists, preceded the work presented here, and concluded with the international conference "Tracce di Cosmopolitismo intorno al Mediterraneo. Migrazioni, memorie e attualità” held in Cagliari in autumn 2019. (From the Introduction

Trame cosmopolite. Minorità, migrazioni e città intorno al Mediterraneo. Prospettive cosmopolite sulla città = Cosmopolitan weaves. Minorities, migrations and cities around the Mediterranean. Cosmopolitan perspectives on the city

In conjunction with the papers in RiMe 10/I n.s., in this second Special Issue dedicated to the theme 'Cosmopolitan perspectives on the city: Readings, gazes, practices', we find alternating geographical, historical and anthropological approaches on 'Border communities (Ventimiglia), on forms of 'overlap' and 'interaction' in public spaces (Cagliari), on 'migrant histories', on 'Tunis cosmopolitan and colonial city', on the 'Jewish community of Istanbul', on the 'plural and changing' identity of Odessa and finally a reflection on the 'cosmo-political' city. The themes of cosmopolitanism are discussed through questions of urbanity, public space, the effects of international mobility and political management, as well as the subjectivities of 'communities of communities' or minorities that 'fabricate', shape and animate cities

Safe picosatellite release from a small satellite carrier

The Berlin Infrared Optical System satellite, which is scheduled for launch in 2016, will carry onboard a picosatellite and release it through a spring mechanism. After separation, it will perform proximity maneuvers in formation with the picosatellite solely based on optical navigation. Therefore, it is necessary to keep the distance of the two spacecraft within certain boundaries. This is especially challenging because the employed standard spring mechanism is designed to impart a separation velocity to the picosatellite. A maneuver strategy is developed in the framework of relative orbital elements. The goal is to prevent loss of formation while mitigating collision risk. The main design driver is the performance uncertainty of the release mechanism. The analyzed strategy consists of two maneuvers: the separation itself, and a drift-reduction maneuver of the Berlin Infrared Optical System satellite after 1.5 revolutions. The selected maneuver parameters are validated in a Monte Carlo simulation. It is demonstrated that both the risk of formation evaporation (separation of more than 50 km) as well as the eventuality of a residual drift toward the carrier are below 0.1%. In the latter case, formation safety is guaranteed by a passive safety achieved through a proper relative eccentricity/inclination vector separation

Costruzioni territoriali e migrazione. Spazi del sacro e identità religiose a Cagliari

Partendo dall’evidenza di una correlazione strutturale fra l’amplificazione del fenomeno migrato- rio in Italia e in Europa (in termini di crescita numerica e di diversificazione di origine) e l’emergere di nuove pratiche religiose, il contributo propone alcune piste che incociano tre campi: gli spazi del sa- cro, i migration studies e la geografia sociale. Il contributo, che rende conto dei primi passi di una ricerca in corso, è volto a considerare in che modo, nell’area metropolitana di Cagliari, il vissuto religioso praticato presso ‚nuovi‛ luoghi di culto e aggregazione comunitaria come chiese ortodosse o cattoliche di riti orientali, o moschee e templi, of- fra ad alcuni gruppi di migranti la possibilità di mettere in atto strategie di appropriazione di partico- lari spazi urbani, cercando di comprenderne le dinamiche, le ricadute sociali e comunitarie, in partico- lare nello spazio pubblico condiviso. Lo studio, che si muove per il caso di Cagliari su un terreno poco battuto dalla ricerca, più che inserirsi in una ‚geografia delle religioni‛ o in una ‚geografia del sacro‛3, suggerisce di indagare su come la dimensione religiosa (e del sacro) interviene a qualificare e a strut- turare il territorio (Turco, 2010), dal punto di vista sociale, politico e simbolico, contemplando sia for- me di competizione per l’appropriazione dello spazio, sia configurazioni che esprimono forme di resi- stenza di un’alterità da recuperare o di una cittadinanza da rivendicar