Innovative methods of correlation and orbit determination for space debris

We propose two algorithms to provide a full preliminary orbit of an Earth-orbiting object with a number of observations lower than the classical methods, such as those by Laplace and Gauss. The first one is the Virtual debris algorithm, based upon the admissible region, that is the set of the unknown quantities corresponding to possible orbits for objects in Earth orbit (as opposed to both interplanetary orbits and ballistic ones). A similar method has already been successfully used in recent years for the asteroidal case. The second algorithm uses the integrals of the geocentric 2-body motion, which must have the same values at the times of the different observations for a common orbit to exist. We also discuss how to account for the perturbations of the 2-body motion, e.g., the $J_2$ effect.Comment: 18 page

On the Juno Radio Science Experiment: models, algorithms and sensitivity analysis

Juno is a NASA mission launched in 2011 with the goal of studying Jupiter. The probe will arrive to the planet in 2016 and will be placed for one year in a polar high-eccentric orbit to study the composition of the planet, the gravity and the magnetic field. The Italian Space Agency (ASI) provided the radio science instrument KaT (Ka-Band Translator) used for the gravity experiment, which has the goal of studying the Jupiter's deep structure by mapping the planet's gravity: such instrument takes advantage of synergies with a similar tool in development for BepiColombo, the ESA cornerstone mission to Mercury. The Celestial Mechanics Group of the University of Pisa, being part of the Juno Italian team, is developing an orbit determination and parameters estimation software for processing the real data independently from NASA software ODP. This paper has a twofold goal: first, to tell about the development of this software highlighting the models used, second, to perform a sensitivity analysis on the parameters of interest to the mission.Comment: Accepted for publication in MONTHLY NOTICES of the Royal Astronomical Society 2014 October 31. Received 2014 July 28; in original form 2013 October

Constraining the Nordtvedt parameter with the BepiColombo Radioscience experiment

BepiColombo is a joint ESA/JAXA mission to Mercury with challenging objectives regarding geophysics, geodesy and fundamental physics. The Mercury Orbiter Radioscience Experiment (MORE) is one of the on-board experiments, including three different but linked experiments: gravimetry, rotation and relativity. The aim of the relativity experiment is the measurement of the post-Newtonian parameters. Thanks to accurate tracking between Earth and spacecraft, the results are expected to be very precise. However, the outcomes of the experiment strictly depends on our "knowledge" about solar system: ephemerides, number of bodies (planets, satellites and asteroids) and their masses. In this paper we describe a semi-analytic model used to perform a covariance analysis to quantify the effects, on the relativity experiment, due to the uncertainties of solar system bodies parameters. In particular, our attention is focused on the Nordtvedt parameter $\eta$ used to parametrize the strong equivalence principle violation. After our analysis we estimated $\sigma[\eta]\lessapprox 4.5\times 10^{-5}$ which is about 1~order of magnitude larger than the "ideal" case where masses of planets and asteroids have no errors. The current value, obtained from ground based experiments and lunar laser ranging measurements, is $\sigma[\eta]\approx 4.4\times 10^{-4}$. Therefore, we conclude that, even in presence of uncertainties on solar system parameters, the measurement of $\eta$ by MORE can improve the current precision of about 1~order of magnitude

Testing General Relativity with the Radio Science Experiment of the BepiColombo mission to Mercury

The relativity experiment is part of the Mercury Orbiter Radio science Experiment (MORE) on-board the ESA/JAXA BepiColombo mission to Mercury. Thanks to very precise radio tracking from the Earth and accelerometer, it will be possible to perform an accurate test of General Relativity, by constraining a number of post-Newtonian and related parameters with an unprecedented level of accuracy. The Celestial Mechanics Group of the University of Pisa developed a new dedicated software, ORBIT14, to perform the simulations and to determine simultaneously all the parameters of interest within a global least squares fit. After highlighting some critical issues, we report on the results of a full set of simulations, carried out in the most up-to-date mission scenario. For each parameter we discuss the achievable accuracy, in terms of a formal analysis through the covariance matrix and, furthermore, by the introduction of an alternative, more representative, estimation of the errors. We show that, for example, an accuracy of some parts in 10−6 for the Eddington parameter β and of 10−5 for the Nordtvedt parameter η can be attained, while accuracies at the level of 5 × 10−7 and 1 × 10−7 can be achieved for the preferred frames parameters α1 and α2, respectively

New Tools for the Optimized Follow-Up of Imminent Impactors

The solar system is populated with, other than planets, a wide variety of minor bodies, the majority of which are represented by asteroids. Most of their orbits are comprised of those between Mars and Jupiter, thus forming a population named Main Belt. However, some asteroids can run on trajectories that come close to, or even intersect, the orbit of the Earth. These objects are known as Near Earth Asteroids (NEAs) or Near Earth Objects (NEOs) and may entail a risk of collision with our planet. Predicting the occurrence of such collisions as early as possible is the task of Impact Monitoring (IM). Dedicated algorithms are in charge of orbit determination and risk assessment for any detected NEO, but their efficiency is limited in cases in which the object has been observed for a short period of time, as is the case with newly discovered asteroids and, more worryingly, imminent impactors: objects due to hit the Earth, detected only a few days or hours in advance of impacts. This timespan might be too short to take any effective safety countermeasure. For this reason, a necessary improvement of current observation capabilities is underway through the construction of dedicated telescopes, e.g., the NEO Survey Telescope (NEOSTEL), also known as “Fly-Eye”. Thanks to these developments, the number of discovered NEOs and, consequently, imminent impactors detected per year, is expected to increase, thus requiring an improvement of the methods and algorithms used to handle such cases. In this paper we present two new tools, based on the Admissible Region (AR) concept, dedicated to the observers, aiming to facilitate the planning of follow-up observations of NEOs by rapidly assessing the possibility of them being imminent impactors and the remaining visibility time from any given station

Orbit determination of space objects based on sparse optical data

While building up a catalog of Earth orbiting objects, if the available optical observations are sparse, not deliberate follow ups of specific objects, no orbit determination is possible without previous correlation of observations obtained at different times. This correlation step is the most computationally intensive, and becomes more and more difficult as the number of objects to be discovered increases. In this paper we tested two different algorithms (and the related prototype software) recently developed to solve the correlation problem for objects in geostationary orbit (GEO), including the accurate orbit determination by full least squares solutions with all six orbital elements. Because of the presence in the GEO region of a significant subpopulation of high area to mass objects, strongly affected by non-gravitational perturbations, it was actually necessary to solve also for dynamical parameters describing these effects, that is to fit between 6 and 8 free parameters for each orbit. The validation was based upon a set of real data, acquired from the ESA Space Debris Telescope (ESASDT) at the Teide observatory (Canary Islands). We proved that it is possible to assemble a set of sparse observations into a set of objects with orbits, starting from a sparse time distribution of observations, which would be compatible with a survey capable of covering the region of interest in the sky just once per night. This could result in a significant reduction of the requirements for a future telescope network, with respect to what would have been required with the previously known algorithm for correlation and orbit determination.Comment: 20 pages, 8 figure

Las trasformaciones a través de ventanas territoriales: Quebrada de Humahuaca, Jujuy

El trabajo ensaya el redibujo, construcción y análisis de nuevas cartografías y esquemas interpretativos de algunas ventanas territoriales, en varia escalas de acercamiento, para ciertos centros urbanos de la Quebrada de Humahuaca (Jujuy, Argentina) como un instrumento de conocimiento. En este sentido, esta investigación busca interpretar los procesos morfológicos de transformación de las últimas décadas, en relación a la crisis económica de la Argentina de principios del siglo XXI, la declaratoria de la Quebrada de Humahuaca como Patrimonio de la Humanidad (UNESCO, 2003) y la promoción turística nacional, entre otros acontecimientos que han modificado las lógicas locales. Para esto, estudia los cambios y permanencias en el espacio construido y los distintos tipos de desarrollo urbano –agregación de nuevas manzanas, anexión de nuevos barrios y loteos discontinuos a la mancha urbana o densificación gradual de los usos urbanos, rurales y rururbanos, entre otros- a la luz de la historia reciente de la Quebrada.The paper works on the redraw, construction and analysis of new maps and interpretations in some territorials windows, in various scales, for few urban centers of the Quebrada de Humahuaca (Jujuy, Argentina) as an instrument of knowledge. In this sense, this research is looking to understand the morphological processes of transformation in recent decades, in relation to the economic crisis in Argentina at the beginning of the XXI century, the declaration of the Quebrada de Humahuaca as a World Heritage Site (UNESCO, 2003) and national tourism promotion, among other events that have changed the local’s logics. For this, study the changes and continuities in the territory and the types of urban development -adding new blocks, annexation of new neighborhoods and subdivisions in the urban discontinuous or gradual densification of urban, rural and rururban, among others- knowing the recent history of the Quebrada.Peer Reviewe

The institutionalization of heritage in Quebrada de Humahuaca: the case of Purmamarca

La Quebrada de Humahuaca fue declarada en el año 2003 como patrimonio de la Humanidad por la UNESCO. No obstante, la institucionalización del patrimonio de este territorio comenzó por lo menos a principios del siglo XX. Dentro del complejo proceso influyeron variadas acciones académicas, turísticas, legislativas, entre otras. En esta oportunidad, analizamos los trabajos académicos que se vinculan con la valoración de ciertos objetos, lugares y paisajes. Asimismo, estudiamos las normativas y las acciones de conservación y recuperación de ciertos bienes patrimoniales. Por último, examinamos cómo se entrecruza el saber experto y el poder político en la institucionalización del patrimonio. Para ello, tomamos como caso de estudio a Purmamarca, una aglomeración quebradeña, que ha sido reconocida como un lugar con elementos de interés histórico y turístico a preservar en diferentes ocasiones, desde comienzos del siglo XX hasta nuestros días. Este proceso de selección patrimonial y de valoración de los bienes ha tenido distintas etapas y modos de activación patrimonial, donde se vislumbran tres momentos de selección en la valoración académica y en las normativas: los objetos -principalmente arquitectónicos y arqueológicos-, los centros urbanos, y los paisajes. En ese recorrido, algunos objetos y prácticas se han destacado y otros han quedado fuera de la legitimación de los expertos y de las normativas del poder político.In 2003, Quebrada de Humahuaca was proclaimed as World Heritage by UNESCO. However, the institutionalization of heritage in this territory began at least in the early twentieth century. Within this complex process there is the influence of several actions (academic, tourism, legislation, among others). As part of this research we analysed here how the academic knowledge is linked to the valorisation of some objects, places and landscape. We also studied the regulations, the actions for conservation and the recovery of certain heritage assets. Finally, we examine how the expert knowledge and the political power relate to each other. In order to do so, we take as a case study Purmamarca, a town from Quebrada de Humahuaca, that has been recognized as a place of historical and tourist interest to preserve since the early twentieth century until today. This process of selection and valorisation of heritage has had different stages and forms that can be sum up to three: The moment of the objects (mainly the archaeological and architectural ones), the moment of the urban centres, and moment of the landscapes. In that journey, some objects and practices were highlighted and others had been miss looked by the experts and the regulations from the political power.Fil: Mancini, Clara Elisa. Universidad de Buenos Aires. Facultad de Filosofía y Letras. Instituto de Arqueología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Tommei, Constanza Inés. Universidad de Buenos Aires. Facultad de Arquitectura y Urbanismo. Instituto de Arte Americano e Investigación Estéticas "Mario Buschiazzo"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Addressing some critical aspects of the BepiColombo MORE relativity experiment

The Mercury Orbiter radio Science Experiment (MORE) is one of the experiments on-board the ESA/JAXA BepiColombo mission to Mercury, to be launched in October 2018. Thanks to full on-board and on-ground instrumentation performing very precise tracking from the Earth, MORE will have the chance to determine with very high accuracy the Mercury-centric orbit of the spacecraft and the heliocentric orbit of Mercury. This will allow to undertake an accurate test of relativistic theories of gravitation (relativity experiment), which consists in improving the knowledge of some post-Newtonian and related parameters, whose value is predicted by General Relativity. This paper focuses on two critical aspects of the BepiColombo relativity experiment. First of all, we address the delicate issue of determining the orbits of Mercury and the Earth-Moon barycenter at the level of accuracy required by the purposes of the experiment and we discuss a strategy to cure the rank deficiencies that appear in the problem. Secondly, we introduce and discuss the role of the solar Lense-Thirring effect in the Mercury orbit determination problem and in the relativistic parameters estimation.Comment: 29 pages, 5 figures. Presented at the Seventh International Meeting on Celestial Mechanics, San Martino al Cimino (Viterbo, Italy), 3-9 September 201

La politica online del MoVimento 5 Stelle: il caso di Facebook

Il MoVimento 5 Stelle si è imposto come un partito politico che ha trovato nello slogan della capacità della rete quale veicolo di democrazia uno dei punti fondamentali del proprio successo. Grazie al tema della democrazia diretta online si è affermata all’interno dell’ambiente politico italiano una realtà partitica che si dichiara di rottura rispetto al passato e che difficilmente raggiunge compromessi con i suoi avversari. Il successo elettorale che ha permesso l’accesso del partito nel Parlamento italiano fa sorgere una domanda relativa alle capacità e volontà degli esponenti del MoVimento di utilizzare la rete come strumento democratico di partecipazione politica dei cittadini. In particolare ci si interroga sulla concretezza del progetto di coinvolgimento dei cittadini in una e-democracy. Le possibilità che si affacciano sono date dalla presenza di un caso concreto di partecipazione politica online, o in alternativa si proporrebbe una situazione tale da ricondurre il comportamento del partito all’interno della variegata categoria dei populismi, in questa sede definibile come un “populismo digitale”. A seguito di una ricostruzione del percorso che ha portato il MoVimento 5 Stelle dalle sue origini fino al Parlamento si è identificata la piattaforma più vicina all’obiettivo della democrazia digitale, tra le varie piattaforme utilizzate dal partito. Per verificare quale delle alternative tra populismo digitale e partecipazione politica online sia più corretta si è proceduto ad attuare un’analisi dei contenuti avente come oggetto i profili di tre parlamentari e le pagine istituzionali di Camera e Senato dei parlamentari 5 Stelle presenti all’interno del social network Facebook. Si è cercato inoltre di verificare che tipo di relazione si stabilisce eventualmente tra il blog di Beppe Grillo e le pagine Facebook analizzate. Il periodo di tempo preso in analisi è quello che va dal 14 febbraio 2014 fino al 14 marzo 2014. I risultati più significativi mostrano: l’esistenza di una debole dipendenza dei contenuti del blog di Grillo rispetto a quelli dei parlamentari che risultano autonomi rispetto al blog; la presenza di una comunicazione sporadica, broadcast e finalizzata a una funzione informativa dei contenuti dei messaggi analizzati; l’esclusione di una qualsiasi finalità controversiale e deliberativa dei messaggi data dall’assenza di repliche agli interventi dei propri contatti. Tali risultati escludono che fino ad ora per i soggetti analizzati si possa riferire una condotta coerente con l’obiettivo fondamentale del partito di creazione di una democrazia diretta digitale, rendendo più corretta per il caso di studio l’attribuzione di un’etichetta di populismo digitale