Browsing by Author "Ceccaroni, Marta"

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    Addressing imminent impactors threat from distant retrograde orbits (DRO)
    (International Astronautical Federation (IAF), 2022-09-22) Martinez Mata, Alfonso; Perozzi, Ettore; Ceccaroni, Marta
    Planetary Defence is gaining momentum after the launching toward the Didymos binary system of NASA DART, the first asteroid deflection mission, foreseeing also the deployment of ASI’s LICIAcube. Moreover, the ESA Hera spacecraft, which will contribute to assessing the DART impact momentum transfer, is in full realization phase. After the well established US planetary defence activities, the European Union has recently included the NEO hazard in its own Space Programme in order to extend and complement the ESA initiatives i.e. the establishment of NEO Coordination centre at ESRIN and the realization of the wide-field high-sensitivity Flyeye telescope. Both NASA and ESA also plan to improve the efficiency of their observational networks by launching space mission devoted to NEO observations from space. Finally, the ever-growing NEO discovery rate moves toward increasingly smaller objects passing close to our planet, thus posing new challenges in performing follow- up observations for determining their orbital and physical properties. Within this framework, addressing the so called ”imminent impactors” threat, posed by objects in the 10-40 m range in route of collision with the Earth (the Tunguska-class objects), has become a key issue for planetary defence. Deflection capabilities are useless if a celestial body large enough to produce significant damage can sneak up on the Earth undetected, as could asteroids hiding by the Sun, lurking in the well-known blind spot that ground-based observations can never peer into. In this respect the advantages of placing a telescope on a stable Distant Retrograde Obit (DRO) around the Earth when compared with other orbital configurations have already been proven, and they are now well established in the literature. In this work the feasibility of a mission scenario foreseeing a constellation of four spacecraft in DRO is invesitgated in detail, comparing several target orbits and different transfer strategies, including lunar swing-bys. The more efficient orbital configurations in terms of accessibility and detection capabilities are investigated and validated using case studies of historic asteroid undetected close encounters. Results prove that a DRO constellation would be able to detect and refine the trajectory of a Tunguska-size object with a warning time exceeding the requirement set for natural disasters. The possibility of contributing to the physical characterization of an imminent impactor is also discussed, which is essential for building up an efficient rapid response system for civil protection purposes.
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    Assessment of flyby methods as applied to close encounters among asteroids
    (MDPI, 2024-08-09) Stronati, Nicolò; Fenucci, Marco; Micheli, Marco; Ceccaroni, Marta
    Orbital flybys have been extensively studied for spacecraft missions, resulting in effective mathematical and physical models. However, these models’ applicability to natural encounters involving asteroids has not been explored. This paper examines the applicability of two such theories, patched conics (PC) and the Keplerian map (KM), to asteroid encounters. A review of the two methods will be provided, highlighting their assumptions and range of applicability. Simulations of asteroid–asteroid encounters will then be performed to evaluate their effectiveness in these scenarios. The simulation parameters are set by collecting data on actual asteroid–asteroid encounters, hereby presented, generally characterised by high close approach distances and small masses of the perturbing bodies, if compared to those used to build the flyby theories. Results show that the PC theory’s effectiveness diminishes with increasing approach distances, aligning with its assumptions. Moreover, the prediction of the model is better in the geometric configurations where the flyby has major effects on the orbital energy change. The KM theory has shown good effectiveness for encounters occurring outside the sphere of influence of the perturbing body, even for very high distances. This research investigates flyby models’ strengths and weaknesses in asteroid encounters, offering practical insights and future directions.
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    The evolution of the Line of Variations at close encounters: an analytic approach
    (Springer, 2019-09-28) Valsecchi, G. B.; Del Vigna, A.; Ceccaroni, Marta
    We study the post-encounter evolution of fictitious small bodies belonging to the so-called Line of Variations (LoV) in the framework of the analytic theory of close encounters. We show the consequences of the encounter on the local minimum of the distance between the orbit of the planet and that of the small body and get a global picture of the way in which the planetocentric velocity vector is affected by the encounter. The analytical results are compared with those of numerical integrations of the restricted three-body problem
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    Influence of the dynamic classification of asteroids on observation astrometric errors: a statistical analysis
    (Oxford University Press, 2023-03-24) Stronati, Nicolo'; Faggioli, Laura; Micheli, M.; Ceccaroni, Marta
    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.
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    Rectifying homographies for stereo vision: analytical solution for minimal distortion
    (Springer, 2022-07-07) Lafiosca, Pasquale; Ceccaroni, Marta
    Stereo rectification is the determination of two image transformations (or homographies) that map corresponding points on the two images, projections of the same point in the 3D space, onto the same horizontal line in the transformed images. Rectification is used to simplify the subsequent stereo correspondence problem and speeding up the matching process. Rectifying transformations, in general, introduce perspective distortion on the obtained images, which shall be minimised to improve the accuracy of the following algorithm dealing with the stereo correspondence problem. The search for the optimal transformations is usually carried out relying on numerical optimisation. This work proposes a closed-form solution for the rectifying homographies that minimise perspective distortion. The experimental comparison confirms its capability to solve the convergence issues of the previous formulation. Its Python implementation is provided.
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    Statistical analysis of a weighting scheme for asteroid observation astrometric errors taking into consideration the classification of the observed asteroids
    (International Astronautical Federation (IAF), 2022-09-22) Stronati, Nicolo; Faggioli, Laura; Micheli, Marco; Ceccaroni, Marta
    Observations of asteroids and other near-Earth objects are of great importance for planetary defence activities, the purpose of which is to determine their positions in space and the probabilities of Earth impacts, as well as developing strategies to mitigate this risk. In this framework, having precise observations is important to describe accurately the orbits of near-Earth asteroids. However, given a general absence of a-priori uncertainty information, the single observations are given proper weights that reflect the accuracy expected by the observers who perform the observations. The weights are calculated for each observer on the base of statistical analysis of systematic and random errors and providing them with an accurate definition is necessary if the magnitude of the error of a single observation is to be correctly estimated. In this paper a statistical analysis on the residuals of the astrometric data provided by the major surveys is presented introducing a dynamic classification of observed asteroids. The observations are thus subdivided between those relative to Near Earth and Main Belt Asteroids and the quality of the data for each station is studied focussing on this classification. The results show that most of the considered stations have the same quality regardless of the measured object, while four of them show a dependency on this factor.
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    The Aegis orbit determination and impact monitoring system and services of the ESA NEOCC web portal
    (Springer, 2024-12-01) Fenucci, M.; Faggioli, L.; Gianotto, F.; Bracali Cioci, D.; Cano, J. L.; Conversi, L.; Devogèle, M.; Di Girolamo, G.; Drury, C.; Föhring, D.; Gisolfi, L.; Kresken, R.; Micheli, M.; Moissl, R.; Ocaña, F.; Oliviero, D.; Porru, A.; Ramirez-Moreta, P.; Rudawska, R.; Bernardi, F.; Bertolucci, A.; Dimare, L.; Guerra, F.; Baldisserotto, V.; Ceccaroni, Marta; Cennamo, R.; Chessa, A.; Del Vigna, A.; Koschny, D.; Teodorescu, A. M.; Perozzi, E.
    The NEO Coordination Centre (NEOCC) of the European Space Agency is an operational centre that, among other activities, computes the orbits of near-Earth objects and their probabilities of impact with the Earth. The NEOCC started providing information about near-Earth objects in 2012 on a dedicated web portal, accessible at https://neo.ssa.esa.int/. Since the beginning of the operational phase, many developments and improvements have been implemented regarding the software, the data provided, and the portal. One of the most important upgrades is that the NEOCC is now independently providing data through a newly developed Orbit Determination and Impact Monitoring system, named Aegis. All the data computed by Aegis are publicly available on the NEOCC web portal, and Aegis is also used to maintain all the major services offered. The most important services comprise an orbital catalogue of all known asteroids, a list of possible future impacts with the Earth (also called Risk List), a list of forthcoming close approaches, a set of graphical toolkits, and an on-demand ephemerides service. Many of the services are also available through dedicated APIs, which can be used to automatically retrieve data. Here we give an overview of the algorithms implemented in the Aegis software and provide a summary of the services offered by the NEOCC that are supported by Aegis.