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The integration of non-terrestrial networks into the 5G ecosystem is mainly driven by the possibility of provisioning service in remote areas. In this context, the advent of flying base stations at the low Earth orbit (LEO) will enable anywhere and anytime connectivity. To materialize this vision, it is of utmost importance to improve radio protocols with the aim of allowing direct satellite access. Bearing this aspect in mind, we present a new random access signal, which is based on the filter bank multicarrier (FBMC) waveform, and a computationally efficient detection scheme. The proposed solution outperforms the standardized access scheme based on single-carrier frequency division multiplexing (SC-FDM), by reducing out-of-band (OOB) emissions and reducing the missed detection probability in presence of very high carrier frequency offset (CFO), which is inherent to LEO satellite systems. The improvement is related to the fine frequency resolution of the detector and the use of pulse shaping techniques. Interestingly, the FBMC-based random access signal achieves a high level of commonality with 5G new radio, as the preamble generation method and the time-frequency allocation pattern can be kept unchanged. Concerning the practical implementation aspects, the complexity of the detector is similar in both SC-FDM and FBMC. This paper is part of the R+D+i project (PID2020-115323RB-C31) funded by MCIN/AEI/ 10.13039/501100011033. This work is supported by the grant from Spanish Ministry of Economic Affairs and Digital Transformation and the European union - NextGenerationEU (UNICO-5G I+D/AROMA3D-Space (TSI-063000-2021-70))

Applying chaos theory for secure digital communications is promising and it is well acknowledged that in such applications the underlying chaotic systems should be carefully chosen. However, the requirements imposed on the chaotic systems are usually heuristic, without theoretic guarantee for the resultant communication scheme. Among all the primitives for secure communications, it is well-accepted that (pseudo) random numbers are most essential. Taking the well-studied two-dimensional coupled map lattice (2D CML) as an example, this paper performs a theoretical study towards pseudo-random number generation with the 2D CML. In so doing, an analytical expression of the Lyapunov exponent (LE) spectrum of the 2D CML is first derived. Using the LEs, one can configure system parameters to ensure the 2D CML only exhibits complex dynamic behavior, and then collect pseudo-random numbers from the system orbits. Moreover, based on the observation that least significant bit distributes more evenly in the (pseudo) random distribution, an extraction algorithm E is developed with the property that, when applied to the orbits of the 2D CML, it can squeeze uniform bits. In implementation, if fixed-point arithmetic is used in binary format with a precision of $z$ bits after the radix point, E can ensure that the deviation of the squeezed bits is bounded by $2^{-z}$ . Further simulation results demonstrate that the new method not only guide the 2D CML model to exhibit complex dynamic behavior, but also generate uniformly distributed independent bits. In particular, the squeezed pseudo random bits can pass both NIST 800-22 and TestU01 test suites in various settings. This study thereby provides a theoretical basis for effectively applying the 2D CML to secure communications., Comment: 10 pages, 11figures

The high maneuverability of fixed-wing unmanned aerial vehicles (UAVs) exposes these systems to several dynamical and parametric uncertainties, severely affecting the fidelity of modeling and causing limited guidance autonomy. This article shows enhanced autonomy via adaptation mechanisms embedded in the guidance law: a vector-field method is proposed that does not require a priori knowledge of the UAV course time constant, coupling effects, and wind amplitude/direction. Stability and performance are assessed using the Lyapunov theory. The method is tested on software-in-the loop and hardware-in-the-loop UAV platforms, showing that the proposed guidance law outperforms state-of-the-art guidance controllers and standard vector-field approaches in the presence of significant uncertainty.

The tethered formation system has been widely studied due to its extensive use in aerospace engineering, such as Earth observation, orbital location, and deep space exploration. The deployment of such a multitethered system is a problem because of the oscillations and complex formation maintenance caused by the space tether's elasticity and flexibility. In this article, a triangle tethered formation system is modeled, and an exact stable condition for the system's maintaining is carefully analyzed, which is given as the desired trajectories; then, a new control scheme is designed for its spinning deployment and stable maintenance. In the proposed scheme, a novel second-order sliding mode controller is given with a designed nonsingular sliding-variable. Based on the theoretical proof, the addressed sliding variable from the arbitrary initial condition can converge to the manifold in finite time, and then sliding to the equilibrium in finite time as well. The simulation results show that compared with classic second sliding-mode control, the proposed scheme can speed up the convergence of the states and sliding variables.

A novel adaptive method to achieve both path following and formation moving along desired orbits in the presence of a spatio-temporal flowfield is presented. The flowfield is a spatio-temporal general flow with unknown time-varying parameters. The so-called \emph{congelation of variables} method is used to estimate the time-varying flow parameters, which do not have any restrictions on the rate of their variation. The asymptotic properties of the resulting adaptive system are studied in detail. Simulation results demonstrate the effectiveness of the proposed method.

In this paper we prove explicit estimates for the size of small lifts of points in homogeneous spaces. Our estimates are polynomially effective in the volume of the space and the injectivity radius., Comment: 31 pages

Low-Earth orbit (LEO) satellite networks are meant to be fundamental to closing the digital divide, enabling new market opportunities and providing fifth-generation (5G) New Radio (NR) connectivity everywhere at any time. Despite the advantages of LEO deployments, these systems are characterized by a high mobility and a challenging propagation channel that compromise several procedures of the current 5G standards. One of the impacted areas is the radio mobility management, which is used to ensure continuous and satisfactory service while users handover among cells. Current research shows that the measurement-based 5G NR handover (HO) procedures, designed for terrestrial networks, fail to ensure optimal mobility performance. In this work, we provide a mobility performance analysis through extensive system-level simulations of state-of-the-art HO procedures for 5G NR over LEO satellite networks with Earth-moving cells. Furthermore, this article presents a novel antenna gain-based HO solution for intra-satellite mobility that exploits the predictability of the satellites movement and the antenna gain of the satellite beams, making user equipment (UE)’s radio measurements obsolete. The system-level simulation results, which consider users in rural and urban scenarios, show that by exploiting the known satellite’s trajectory, the UE eliminates service failures and undesired HO events, maximises the time-of-stay in a cell and experiences improved downlink signal-to-interference-plus-noise ratio. This article also includes a sensitivity study of the impact on the mobility performance of satellite-specific and UE-specific errors such as the UE’s location error, the satellite beam’s antenna radiation error and the satellite’s pointing error. Finally, the impact of the UE’s mobility is analyzed.

Artificial intelligence is paving the way for a new era of algorithms focusing directly on the information contained in the data, autonomously extracting relevant features for a given application. While the initial paradigm was to have these applications run by a server hosted processor, recent advances in microelectronics provide hardware accelerators with an efficient ratio between computation and energy consumption, enabling the implementation of artificial intelligence algorithms ‘at the edge’. In this way only the meaningful and useful data are transmitted to the end-user, minimising the required data bandwidth, and reducing the latency with respect to the cloud computing model. In recent years, European Space Agency is promoting the development of disruptive innovative technologies on-board Earth Observation missions. In this field, the most advanced experiment to date is the Φ-sat-1, which has demonstrated the potential of Artificial Intelligence as a reliable and accurate tool for cloud detection on-board a hyperspectral imaging mission. The activities involved included demonstrating the robustness of the Intel Movidius Myriad 2 hardware accelerator against ionising radiation, developing a Cloudscout segmentation neural network, run on Myriad 2, to identify, classify, and eventually discard on-board the cloudy images, and assessing of the innovative Hyperscout-2 hyperspectral sensor. This mission represents the first official attempt to successfully run an AI Deep Convolutional Neural Network (CNN) directly inferencing on a dedicated accelerator on-board a satellite, opening the way for a new era of discovery and commercial applications driven by the deployment of on-board AI.

The Circular-Restricted Three-Body Problem (CR3BP) describes the motion of a small celestial body in the gravitational field of two larger bodies. The present study focuses on the application of the CR3BP to the Sun-Earth system. To that end, the governing and defining equations for the CR3BP are described in-depth; and key periodic orbits around the Lagrange Points L1, L2, L4, and L5 are mapped. These last two points, located at the vertices of an equilateral triangle in the rotating frame of reference, are particularly useful for observation and exploration due to their stability. Thus, the L4 and L5 points are the final objective of the present study. The study focuses on optimizing transfer trajectories from the previously mapped orbits around L1 and L2 to orbits around L4 and L5, respectively. The procedures utilized significantly reduce the required delta-V budget to perform these transfers to approximately 3 km/s, a value lower than the minimum requirements for interplanetary transfers departing from Earth. This finding has the potential to open up new opportunities for asteroid science and solar observation based at the equilateral Lagrange Points of the Sun-Earth system; ultimately contributing to advancing the current era of scientific research in the field of astrodynamics.

International audience; Low-Earth orbit (LEO) constellations are revolutionizing the world of satellite communication (Satcom), providing new opportunities to manufacturers and operators and enabling innovative and attractive services to users.

Treballs Finals de Grau de Matemàtiques, Facultat de Matemàtiques, Universitat de Barcelona, Any: 2023, Director: Ernest Fontich, [en] The Sitnikov Problem is the study of the dynamics of a particular system in the restricted Three-Body Problem, where the masses interact with each other through Newton’s law of universal gravitation. This paper studies the motion of the constrained mass of the Sitnikov Problem in order to demonstrate, through the Bernoulli Shift, the existence of periodic orbits.

Die Visualisierung von Hypergraphen ist äquivalent zur Visualisierung von Sets, da die Knoten eines Hypergraph als Setelemente und die Hyperedges als Sets interpretiert werden können. Daher ist die Visualisierung dieser Strukturen ein wichtiges Thema sowohl in der Graphendarstellung als auch in der Informationsvisualisierung. Bei einigen Hypergraphen kann die Zuordnung von Knoten im Graphen zu Positionen in der Visualisierung nicht beliebig gewählt werden (beispielsweise bei der Visualisierung von geographischen Daten auf einer Karte). Die Visualisierung solcher Hypergraphen mit einer existierenden Knotenzuordnung ist ein aktives Forschungsgebiet, für das in den letzten Jahren mehrere verschiedene Methoden entwickelt worden sind. Diese bestehenden Visualisierungsmethoden sind im Allgemeinen für eine statische Knotenzuordnung entwickelt worden. In der Praxis ist es jedoch möglich, dass sich diese Knotenzuordnung im Laufer der Zeit ändert oder auf Benutzereingaben reagieren muss. Ein Beispiel dafür wäre die Visualisierung von Flugzeugen auf einer Karte, bei der die Flugzeuge durch Knoten dargestellt werden und die Hyperedges die Zugehörigkeit zu einer Fluggesellschaft darstellen. In dieser Arbeit schlagen wir eine Technik vor, die die Grundlage für eine solche Hypergraph-Visualisierung bildet. Diese Technik ist inspiriert von State of the Art Hypergraph-Visualisierungstechniken und anderen Konzepten der Graphendarstellung, um Hypergraphen nicht nur in einer statischen Umgebung zu visualisieren, sondern auch mit zeitlich veränderlichen Daten umgehen zu können. Zu diesem Zweck entwickeln und implementieren wir neue Algorithmen, um diese Art der Visualisierung zu konstruieren. Darüber hinaus führen wir Qualitätsmetriken für die Visualisierung ein und verwenden diese Metriken, um die von den implementierten Algorithmen erzeugten Visualisierungen zu bewerten., Visualizing hypergraphs is equivalent to visualizing sets, since the vertices of a hypergraph can be interpreted as set items and the hyperedges as sets. Therefore, visualizing these structures is a prominent topic in both graph drawing and information visualization. For some hypergraphs, the mapping of vertices in the graph to positions in the visualization cannot be chosen arbitrarily (e.g. when visualizing geospatial data on a map). Visualizing such hypergraphs with a fixed vertex mapping is an active area of research for which several different methods have been developed in recent years. These existing visualization methods are generally designed with static vertex mappings in mind. However, in practice, it is possible that vertex mappings change over time or have to react to user input. An example of this would be a visualization of planes on a map, where the planes are represented by vertices and the hyperedges represent the membership to an airline. In this thesis, we propose a technique that builds the foundation to handle such a hypergraph visualization. It takes inspiration from state-of-the-art hypergraph visualizations and other graph drawing concepts to not only visualize hypergraphs in a static environment but is also adept at dealing with time-varying data. To that end, we develop and implement new algorithms to compute this type of visualization. We furthermore introduce quality metrics for the visualization and use those metrics to evaluate visualizations produced by the implemented algorithms.

The vector field method was originally proposed to guide a single fixed-wing Unmanned Aerial Vehicle (UAV) towards a desired path. In this work, a non-uniform vector field method is proposed that changes in both magnitude and direction, for the purpose of achieving formations of UAVs. As compared to related work in the literature, the proposed formation control law does not need to assume absence of wind. That is, due to the effect of the wind on the UAV, one can handle the UAV air speed being different from its ground speed, and the UAV heading angle being different from its course angle. Stability of the proposed formation method is analyzed via Lyapunov stability theory, and validations are carried out in software-in-the-loop and hardware-in-the-loop comparative experiments. Note to Practitioners - The software-in-the-loop and hardware-in-the-loop experiments, which are done with PX4 autopilot software and hardware, show that the proposed method can be implemented on board of UAVs and integrated with the control architecture of existing autopilot suites. Comparisons with standard formation algorithms show that the proposed method is effective in achieving formation in different path scenarios.

This paper investigates a dual satellite transmission scheme with coherent reception. The receiver has a single synchronization circuit and is locked to only one of the satellites. Beam-centric pre-compensation techniques are considered in the paper. The cooperation area in which coherent reception is feasible is characterized analytically. The application of precoding to the orthogonal time and frequency space (OTFS) waveform is considered to counteract the residual offsets, which result from the displacement of the receiver from the selected reference point. Numerical evaluations show that the dual satellite scheme improves the system spectral efficiency as well the link reliability in comparison with the single satellite transmission scheme. This paper is part of the R+D+i project (PID2020-115323RB-C31) funded by MCIN/AEI/ 10.13039/501100011033.

Earth’s gravity plays a major role in molding our world. Monitoring the geopotential and its time variability reveals the mass redistribution occurring across our planet, thus informing us on matters like climate change and availability of water resources. The gravity features we are most interested in are characterized by spatial and temporal scales that can only be accessed via a mission in space. Among the most important gravity missions are GRACE/GRACE-FO and GOCE, which sense gravity through the derivatives of the Earth’s gravity field. We propose to apply chronometric geodesy, whose task is to measure gravity with clocks, in space through frequency comparison between orbiting clocks by means of the Doppler-canceling technique. The novelty of this approach consists in estimating Earth’s gravity via measurements of the geopotential itself, rather than its derivatives. The behavior of clocks in a gravitational field is governed by Einstein’s general relativity, which provides the best available description of gravitation. On the other hand, the frequency stability of clocks is now reaching 10¹⁹, becoming precise enough for geodesy applications. After describing the proposed gravity mission architecture, we provide a mathematical derivation of the Doppler-canceled frequency shift measurement. Then, we outline the estimation method and its numerical implementation, followed by a presentation of results. Our findings indicate the measurement can retrieve the geopotential coefficients with an accuracy potentially better than currently available gravity models employing clocks with a frequency stability of 10¹⁹. This result represents a proof of concept for the measurement, with gravity field solutions obtained from a mission simulation being shown here for the first time. However, once we introduce the orbit error, the kinematical approach utilized to solve the estimation problem presents severe limitations. The remedy is to adopt a dynamical approach, which would let us directly address the orbit error and other issues, e.g., frequency drift in clocks. In the conclusions, we discuss how to improve on our analysis and the necessary steps to follow in preparation for a future gravity mission, whose realization will be possible only when clock technology reaches the required performance (high frequency stability in a short integration time)

The global navigation satellite systems (GNSSs) are increasingly suffering from interferences, such as coming from jammers and spoofers, and their performance is still modest in challenging urban and indoor scenarios. Therefore, there are efforts worldwide to develop complementary positioning, navigation, and timing (PNT) solutions. One such complementary method under current research is the so-called LEO-PNT, namely, PNT solutions based on low-Earth orbit (LEO) satellites, and in particular on small-sized or miniaturized satellites. Such satellites have low-to-moderate costs of building, launching, and maintenance. Several challenges are to be overcome when designing a new LEO-PNT solution, concerning all three satellite segments: 1) the signal-in-space (SIS) or space segment; 2) the ground segment; and 3) the user/receiver segment. This article presents a survey of the SIS design challenges under the inherent constraints of wireless-channel propagation impairments as well as some design recommendations for SIS features. We address different constellation types, achievable coverage limits, and geometric dilution of precision (GDOP) bounds, as well as achievable carrier-to-noise ratios (CNRs) under a realistic wireless channel model, based on a MATLAB Quadriga simulator. We also discuss several optimization criteria regarding LEO-PNT SIS design, by taking into account the tradeoff between a low cost/low number of satellites in orbit on the one hand, and a sufficient coverage and good CNR for PNT purposes on the other hand. publishedVersion

The fifth generation (5G) Wireless Communication systems development has brought out a paradigm shift using advanced technologies e.g., softwarization, virtualization, Massive MIMO, ultra-densification and introduction of new frequency bands. However, as the societal needs grow, and to satisfy UN's Sustainable Development Goals (SDGs), 6G and beyond systems are envisioned. Non- Terrestrial Networks including satellite systems, Unmanned Aerial Vehicles (UAVs) and High-Altitude Platforms (HAPs) provide the best solutions to connect the unconnected, unserved and underserved in remote and rural areas in particular. Over the past few decades, Geo Synchronous Orbits (GSO) satellite systems have been deployed to support broadband services, backhauling, Disaster Recovery and Continuity of Operations (DR-COOP) and emergency services. Recently, there is a considerable renewed interest in planning and developing non-GSO satellite systems. Within the next few years several thousands of Low Earth Orbit (LEO) satellites and mega LEO constellations will be ready to provide global Internet services. This report is the 2022 Edition of the INGR Satellite Working Group Report, subsequent to the previous two editions [1] [2]. The topics considered in this INGR Satellite WG 2022 Edition of the roadmap are the following taking 6G systems into account: applications and services, reference architectures (both backhaul and direct access), satellite loT, mm Wave use for satellite networks, machine learning and artificial intelligence, edge computing, QoS/QoE, security, network management and standardization. The work on the roadmap will continue towards the next edition of the roadmap addressing new challenges and potential solutions for future networks. © 2022 IEEE.

The orbit of an n-variate polynomial f(x) over a field 𝔽 is the set {f(Ax+b) ∣ A ∈ GL(n, 𝔽) and b ∈ 𝔽ⁿ}, and the orbit of a polynomial class is the union of orbits of all the polynomials in it. In this paper, we give improved constructions of hitting-sets for the orbit of read-once oblivious algebraic branching programs (ROABPs) and a related model. Over fields with characteristic zero or greater than d, we construct a hitting set of size (ndw)^{O(w²log n⋅ min{w², dlog w})} for the orbit of ROABPs in unknown variable order where d is the individual degree and w is the width of ROABPs. We also give a hitting set of size (ndw)^{O(min{w²,dlog w})} for the orbit of polynomials computed by w-width ROABPs in any variable order. Our hitting sets improve upon the results of Saha and Thankey [Chandan Saha and Bhargav Thankey, 2021] who gave an (ndw)^{O(dlog w)} size hitting set for the orbit of commutative ROABPs (a subclass of any-order ROABPs) and (nw)^{O(w⁶log n)} size hitting set for the orbit of multilinear ROABPs. Designing better hitting sets in large individual degree regime, for instance d > n, was asked as an open problem by [Chandan Saha and Bhargav Thankey, 2021] and this work solves it in small width setting. We prove some new rank concentration results by establishing low-cone concentration for the polynomials over vector spaces, and they strengthen some previously known low-support based rank concentrations shown in [Michael A. Forbes et al., 2013]. These new low-cone concentration results are crucial in our hitting set construction, and may be of independent interest. To the best of our knowledge, this is the first time when low-cone rank concentration has been used for designing hitting sets., LIPIcs, Vol. 207, Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2021), pages 30:1-30:23

We explore the dynamics of the sequence of Kasner quadrilaterals (AnBnCnDn)n≥0 defined via a complex parameter α. We extend the results concerning Kasner triangles with a fixed complex parameter obtained in earlier works and determine the values of α for which the generated dynamics are convergent, divergent, periodic, or dense.

With numerous ongoing deployments owned by private companies and startups, dense satellite constellations deployed in low Earth orbit (LEO) will play a major role in the near future of wireless communications. In addition, the 3rd Generation Partnership Project (3GPP) has ongoing efforts to integrate satellites into 5G and beyond-5G networks. Nevertheless, numerous challenges must be overcome to fully exploit the connectivity capabilities of satellite constellations. These challenges are mainly a consequence of the low capabilities of individual small satellites, along with their high orbital speeds and small coverage due to the low altitude of deployment. In particular, inter-plane inter-satellite links (ISLs), which connect satellites from different orbital planes, are greatly dynamic and may be considerably affected by the Doppler shift. In this paper, we present a framework and the corresponding algorithms for the dynamic establishment of the inter-plane ISLs in LEO constellations. Our results show that the proposed algorithms increase the sum of rates in the constellation 1) by up to 115% with respect to the state-of-the-art benchmark schemes in an interference-free environment and 2) by up to 71% when compared to random resource allocation in a worst-case scenario for interference., To be published in IEEE Transactions on Wireless Communications

The speedy data reception with useful applications such as disaster management remains to be need of the hour. This paper addresses the major concerns relating to deployment and control of the larger small satellite (mainly cubesats) constellations in LEO by determining their relative position and velocity errors under certain acceptable limits with collision avoidance techniques. The article will also discuss the importance of Inter-satellite link to significantly to strengthen the satellite tracking and their data sharing speeds. The issue of optimal dispatch of the satellites by optimizing the constellation size is detailed though observing and controlling the orbits using a well-defined cost and objective function. Given the fact that the small satellites have certain physical constraints such as size and capacity to communicate among satellites and in-orbit exchange of resources, the overall control and optimization of the satellite coverage with travel time through a ground station and their orbit becomes inevitable. Hence, a detailed optimization analysis has been carried to observe and make important conclusions. Th same autonomy of a small satellite constellation is also discussed briefly for deep-space communication considering the cislunar space (NHRO) as one potential destination.

Aquest treball ha rebut finançament del programa europeu DISCOVERER (Disruptive Technologies for Very Low Earth Orbit Platforms, EC-H2020-737183) This thesis studies the complementarity of VLEO satellite technologies with existing solutions in the telecommunications market, both in the space and terrestrial sectors. All the characteristics and particularities of VLEO orbits are defined and explained in detail, showing advantages and disadvantages compared to traditional higher orbits. Study of the deployment of the satellite constellation concept within the New Space framework. Next, the business opportunities that can be generated by the introduction of VLEO technologies in the telecommunications market are studied, analysing the possible reshaping of each vertical market and how can they be most benefited. Finally, a business opportunity is proposed and qualitatively analysed in detail using the Value Proposition Canvas methodology.

Modern satellites deployed in low Earth orbit (LEO) accommodate processing payloads that can be exploited for edge computing. Furthermore, by implementing inter-satellite links, the LEO satellites in a constellation can route the data end-to-end (E2E). These capabilities can be exploited to greatly improve the current store-and-forward approaches in Earth surveillance systems. However, they give rise to an NP-hard problem of joint communication and edge computing resource management (RM). In this paper, we propose an algorithm that allows the satellites to select between computing the tasks at the edge or at a cloud server and to allocate an adequate power for communication. The overall objective is to minimize the energy consumption at the satellites while fulfilling specific service E2E latency constraints for the computing tasks. Experimental results show that our algorithm achieves energy savings of up to 18% when compared to the selected benchmarks with either 1) fixed edge computing decisions or 2) maximum power allocation., Accepted in ICC Workshops 2022

We introduce a novel one-handed input technique for mobile devices that is not based on pointing, but on motion matching -where users select a target by mimicking its unique animation. Our work is motivated by the findings of a survey (N=201) on current mobile use, from which we identify lingering opportunities for one-handed input techniques. We follow by expanding on current motion matching implementations - previously developed in the context of gaze or mid-air input - so these take advantage of the affordances of touch-input devices. We validate the technique by characterizing user performance via a standard selection task (N=24) where we report success rates (>95%), selection times (~1.6 s), input footprint, grip stability, usability, and subjective workload - in both phone and tablet conditions. Finally, we present a design space that illustrates six ways in which motion matching can be embedded into mobile interfaces via a camera prototype application.

We present a new approach to observationally constrain where the tails of Jellyfish (JF) galaxies in groups and clusters first appear and how long they remain visible with respect to the moment of their orbital pericenter. This is accomplished by measuring the distribution of their tail directions with respect to their host's center, and their distribution in a projected velocity-radius phase-diagram. We then model these observed distributions using a fast and flexible approach where JF tails are painted onto dark matter halos according to a simple parameterised prescription, and perform a Bayesian analysis to estimate the parameters. We demonstrate the effectiveness of our approach using observational mocks, and then apply it to a known observational sample of 106 JF galaxies with radio continuum tails located inside 68 hosts such as groups and clusters. We find that, typically, the radio continuum tails become visible on first infall when the galaxy reaches roughly three quarters of r$_{200}$, and the tails remain visible for a few hundred Myr after pericenter passage. Lower mass galaxies in more massive hosts tend to form visible tails further out and their tails disappear more quickly after pericenter. We argue that this indicates they are more sensitive to ram pressure stripping. With upcoming large area surveys of JF galaxies in progress, this is a promising new method to constrain the environmental conditions in which visible JF tails exist., Accepted to ApJ June 2022, 24 pages, 13 figures, 2 tables

Treballs Finals de Grau d'Enginyeria Informàtica, Facultat de Matemàtiques, Universitat de Barcelona, Any: 2022, Director: Gerardo Gómez Muntané, [en] In the modern world, artificial satellites orbiting around the Earth are used in a wide variety of areas. The tracking and modeling of their orbits is of utmost importance. In the following text, a mathematical framework for their study as well as a software implementation and the use of a software suite, GMAT, are presented.

We study a new object that can be attached to an abelian variety or a complex torus: the invariant Brauer group, as recently defined by Yang Cao. Over the field of complex numbers this is an elementary abelian 2-group with an explicit upper bound on the rank. We exhibit many cases in which the invariant Brauer group is zero, and construct complex abelian varieties in every dimension starting with 2, both simple and non-simple, with invariant Brauer group of order 2. We also address the situation in finite characteristic and over non-closed fields., Comment: 32 pages, to appear in Israel J. Math

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2022, Tutors: Francesca Figueras, Toni Santana-Ros, This work’s main goal is to study the classical methods of orbit determination developed by Gauss and Laplace. To do so, simulations of objects orbiting the Earth have been programmed to test these methods and compare the results. They show poor accuracy and don’t allow for predictions in the studied cases, but they improve for large enough orbits where they could be a first approach for more complex orbit determination schemes

This article presents an innovative mechatronic design of a high-accuracy pointing mechanism for orbital laser communication terminals.The system is based on a dual-stage architecture and is miniaturized to fit nanosatellite-class spacecraft, aiming to enable optical communication on small-size space platforms. The focus is on control design aspects and on the performance assessment of an experimental prototype under emulated external environmental disturbances.

Cachexia is a significant contributor to cancer mortality as it is responsible for up to 30% of cancer deaths. Magnetic resonance imaging offers a noninvasive approach to detect features of cachexia. T1-weighted images of cachectic patients have a “pseudo fat-saturated” appearance secondary to disappearance of subcutaneous and fascial fat throughout the body, as well as fat in the bone marrow. Orbital fat remains preserved until late disease. We present 2 cases with these classic imaging findings of cancer cachexia in the subcutaneous tissues of the head, neck, and spine. This imaging phenomenon is often misinterpreted by radiologists and may lead to delayed diagnosis or unnecessary repeat imaging.

In the explosively increased number of applications of earth observation satellites (EOSs), scheduling is a significative issue to satisfy more requests and obtain a high observation efficiency. This article investigates the scheduling of multiple EOSs under the impact of clouds. First, we formulate the presences of clouds as stochastic events, and propose an expectation model. Afterwards, for the first time, a branch-and-price algorithm based on Dantzig–Wolfe decomposition is devised to solve the model optimally and efficiently. In order to obtain initial columns for column generation, a dynamic programming algorithm and a heuristic algorithm are suggested, respectively. Furthermore, we discuss the impact of clouds in the case of joint probabilities, and establish a sample average approximation (SAA) model accordingly. With respect to the expectation model, numerical experiment results demonstrate the relative dominance of the proposed branch-and-price algorithm in terms of solution time compared to CPLEX. In addition, the solution of the proposed SAA model is proven to be more robust than that of the expectation model.

The article concerns the estimation of land deformation in an area of copper mining using the Persistent Scatterer Interferometry (PSI) technique and C-band data coming from the Sentinel-1 satellite. The aim of the work is a comparison of two different PSI approaches exploiting passive corner reflectors deployed pairwise, oriented towards the satellites in ascending and descending orbits. The comparison was done in the line of sight geometry. In addition, a validation was carried out using GNSS measurements. The results achieved using the two PSI approaches are consistent and mutually coherent. They are also congruent with observations from GNSS stations. These results proves that the method proposed to identify pixels on multi-looked images is correct. In addition, the intermediary results on the corner reflectors shows that their responses, in terms of dispersion of amplitude and the coherence, is slightly different. This needs to be further studied.

Mini-EUSO is a small orbital telescope with a field of view of 44◦ × 44◦, observing the night-time Earth mostly in 320-420 nm band. Its time resolution spanning from microseconds (triggered) to milliseconds (untriggered) and more than 300 × 300 km of the ground covered, already allowed it to register thousands of meteors. Such detections make the telescope a suitable tool in the search for hypothetical heavy compact objects, which would leave trails of light in the atmosphere due to their high density and speed. The most prominent example are the nuclearites – hypothetical lumps of strange quark matter that could be stabler and denser than the nuclear matter. In this paper, we show potential limits on the flux of nuclearites after collecting 42 hours of observations data., PoS: Proceedings of Science, 395, ISSN:1824-8039, Proceedings of 37th International Cosmic Ray Conference

The JEM-EUSO (Joint Experiment Missions for Extreme Universe Space Observatory) program aims at the realization of the ultra-high energy cosmic ray (UHECR) observation using wide field of view fluorescence detectors in orbit. Ultra-violet (UV) light emission from the atmosphere such as airglow and anthropogenic light on the Earth’s surface are the main background for the space-based UHECR observations. The Mini-EUSO mission has been operated on the International Space Station (ISS) since 2019 which is the first space-based experiment for the program. The Mini-EUSO instrument consists of a 25 cm refractive optics and the photo-detector module with the 2304-pixel array of the multi-anode photomultiplier tubes. On the nadir-looking window of the ISS, the instrument is capable of continuously monitoring a ∼300 km × 300 km area. In the present work, we report the preliminary result of the measurement of the UV light in the nighttime Earth using the Mini-EUSO data downlinked to the ground. We mapped UV light distribution both locally and globally below the ISS obit. Simulations were also made to characterize the instrument response to diffuse background light. We discuss the impact of such light on space-based UHECR observations and the Mini-EUSO science objectives., PoS: Proceedings of Science, 395 (385), ISSN:1824-8039, Proceedings of 37th International Cosmic Ray Conference

The Extreme Universe Space Observatory on a Super Pressure Balloon II (EUSO-SPB2) is a second generation stratospheric balloon instrument for the detection of Ultra High Energy Cosmic Rays (UHECRs, E > 1 EeV) via the fluorescence technique and of Very High Energy (VHE, E > 10 PeV) neutrinos via Cherenkov emission. EUSO-SPB2 is a pathfinder mission for instruments like the proposed Probe Of Extreme Multi-Messenger Astrophysics (POEMMA). The purpose of such a space-based observatory is to measure UHECRs and UHE neutrinos with high statistics and uniform exposure. EUSO-SPB2 is designed with two Schmidt telescopes, each optimized for their respective observational goals. The Fluorescence Telescope looks at the nadir to measure the fluorescence emission from UHECR-induced extensive air shower (EAS), while the Cherenkov Telescope is optimized for fast signals (∼10 ns) and points near the Earth's limb. This allows for the measurement of Cherenkov light from EAS caused by Earth skimming VHE neutrinos if pointed slightly below the limb or from UHECRs if observing slightly above. The expected launch date of EUSO-SPB2 is Spring 2023 from Wanaka, NZ with target duration of up to 100 days. Such a flight would provide thousands of VHECR Cherenkov signals in addition to tens of UHECR fluorescence tracks. Neither of these kinds of events have been observed from either orbital or suborbital altitudes before, making EUSO-SPB2 crucial to move forward towards a space-based instrument. It will also enhance the understanding of potential background signals for both detection techniques. This contribution will provide a short overview of the detector and the current status of the mission as well as its scientific goals., PoS: Proceedings of Science, 395, ISSN:1824-8039, Proceedings of 37th International Cosmic Ray Conference

We study the transit timings of 10 exoplanets in order to investigate potential transit timing variations in them. We model their available ground-based light curves, some presented here and others taken from the literature, and homogeneously measure the mid-transit times. We statistically compare our results with published values and find that the measurement errors agree. However, in terms of recovering the possible frequencies, homogeneous sets can be found to be more useful, of which no statistically relevant example has been found for the planets in our study. We corrected the ephemeris information of all 10 planets we studied and provide these most precise light elements as references for future transit observations with space-borne and ground-based instruments. We found no evidence for secular or periodic changes in the orbital periods of the planets in our sample, including the ultra-short period WASP-103 b, whose orbit is expected to decay on an observable time-scale. Therefore, we derive the lower limits for the reduced tidal quality factors (Q$^{\prime }_{\star }$) for the host stars based on best-fitting quadratic functions to their timing data. We also present a global model of all available data for WASP-74 b, which has a Gaia parallax-based distance value ∼25 per cent larger than the published value.

We present an interesting case of biopsy-proven multiorgan metastatic invasive lobular carcinoma to the orbits and kidney, initially presenting in a 76-year-old woman with diplopia. Invasive lobular carcinoma is a less common subtype of breast cancer and is often difficult to detect on imaging with an unusual metastatic pattern when compared to invasive ductal carcinoma. Metastatic invasive lobular carcinoma most frequently involves the orbits, ovaries, gastrointestinal tract, retroperitoneum and bone. Disease involving these organ systems detected on imaging should raise concern for metastatic disease when appropriate.

We investigated the dynamical behavior in the potential of the primary in the triple asteroid (45) Eugenia with the calculation of the full gravitational potential caused by its 3D irregular shape. We presented the whole structure of the gravitational potential and the effective potential of (45) Eugenia in the coordinate planes, and showed the surface height, surface gravitational force accelerations, and the surface effective potential. The surface gravitational environment has been discussed. The zero-velocity curves and the position of external equilibrium points are calculated and showed relative to the 3D shape of the asteroid to help compare the relationship of the characteristic of the gravitational potential and the shape of the asteroid. There are five equilibrium points in the gravitational potential (45) Eugenia. We presented the positions, eigenvalues, topological cases, and stability of these equilibrium points. To analyze the variety of the orbital parameters close to (45) Eugenia, we computed two different orbits and compared the results. The mechanical energy, the semi-major axis, and the eccentricity have two different periods: the long period and the short period. The inclination have three different periods, an intermediate period is occurred. The longitude of the ascending node and the argument of periapsis not only have two periodic terms, but also have a secular term.

In this paper we study some combinatorial properties of biquadratic irrational number field ${\mathbb{Q}}( {i,\sqrt{3} } ) $, under the action of a Bianchi group ${\Gamma _3} = PSL({2,{O_3}} ) $. In this experiment it is revealed that a special class of elements exists; that is, for an element $\xi $ its conjugate $\bar{\xi } $ has different signs in the closed path (orbits) for the action of ${\Gamma _3} $ over ${\mathbb{Q}}( {i,\sqrt{3} } ) $, known as ambiguous numbers. It is also proved that the orbit $\Gamma \xi $ defined on a finite number of ambiguous numbers succeeding a unique closed path.

Periodic orbits often describe desired state trajectories of dynamical systems in various engineering applications. Stability analysis of periodic solutions lays a foundation for control design to achieve convergence to a prescribed orbit. Here we consider a class of perturbed nonlinear systems with fast and slow dynamics and develop a novel averaging method for analyzing the local exponential orbital stability of a periodic solution. A framework is then proposed for feedback control design to stabilize a natural oscillation of an uncertain nonlinear system using a synchronous adaptive oscillator. The idea is applied to linear mechanical systems and a design theory is established. In particular, we propose a controller based on the Andronov–Hopf oscillator with additional adaptation mechanisms for estimating the unknown natural frequency and damping parameters. We prove that, with sufficiently slow adaptation, the estimated parameters locally converge to their true values and entrainment to the natural oscillation is achieved as part of an orbitally stable limit cycle. Numerical examples demonstrate that adaptation and convergence can in fact be fast.

We present a survey of some recent results concerning joint numerical ranges ofn-tuples of Hilbert space operators, accompanied with several new observations and remarks. Thereafter, numerical ranges techniques will be applied to various problems of operator theory. In particular, we discuss problems concerning orbits of operators, diagonals of operators and their tuples, and pinching problems. Lastly, motivated by known results on the numerical radius of a single operator, we examine whether, given bounded linear operatorsT1, . . .,Tnon a Hilbert spaceH, there exists a unit vectorx ∈ Hsuch that|〈Tjx,x〉|is “large” for allj= 1, . . . ,n.

In general, the construction of subspace codes or, in particular, cyclic Grassmannian codes in some projective space Pq(n) is highly mathematical and requires substantial computational power for the resulting searches. In this paper, we present a new method for the construction of cyclic Grassmannian codes. To do that was designed and implemented a series of algorithms using the GAP System for Computational Discrete Algebra and Wolfram Mathematica software. We also present a classification of such codes in the space Pq(n), with n at most 9. The fundamental idea to construct and classify the cyclic Grassmannian codes is to endow the projective space Pq(n) with a graph structure and then find cliques.

The integration of non-terrestrial networks into the 5G ecosystem is mainly driven by the possibility of provisioning service in remote areas. In this context, the advent of flying base stations at the low Earth orbit (LEO) will enable anywhere and anytime connectivity. To materialize this vision, it is of utmost importance to improve radio protocols with the aim of allowing direct satellite access. Bearing this aspect in mind, we present a new random access signal, which is based on the filter bank multicarrier (FBMC) waveform, and a computationally efficient detection scheme. The proposed solution outperforms the standardized access scheme based on single-carrier frequency division multiplexing (SC-FDM), by reducing out-of-band (OOB) emissions and reducing the missed detection probability in presence of very high carrier frequency offset (CFO), which is inherent to LEO satellite systems. The improvement is related to the fine frequency resolution of the detector and the use of pulse shaping techniques. Interestingly, the FBMC-based random access signal achieves a high level of commonality with 5G new radio, as the preamble generation method and the time-frequency allocation pattern can be kept unchanged. Concerning the practical implementation aspects, the complexity of the detector is similar in both SC-FDM and FBMC. IEEE

International audience; Meteor shower outbursts happen every year, but cannot be observed by a single meteor camera network. In addition, bad weather might prevent the recording of such event. In order to enable the observation of meteor shower outburst, we developed a "Mobile Observation of METeor" device. It involves two suitcases for meteor double station observations. Each case includes a total of 5 cameras to maximise the scientific output. Each camera is controlled by a mini-PC (RaspBerry pi or Odroid) and runs the "RMS" software (Vida et al. 2021, MNRAS, 506, 4, 5046). The MoMET devices were successfully used to record the 2021 Arids meteor shower from Chile.

International audience; This paper presents orbits and masses for 22 visual double stars, partly derived using their last observations made with the speckle camera PISCO. For 13 of them we have determined their first time orbits. Masses were calculated from Hipparcos and Gaia parallaxes when available, and from dynamical parallaxes otherwise. They are compared with masses deduced from spectral types. Other physical and orbital properties are also considered.This paper presents orbits and masses for 22 visual double stars, partly derived using their last observations made with the speckle camera PISCO. For 13 of them we have determined their first-time orbits. Masses were calculated from Hipparcos and Gaia parallaxes when available, and from dynamical parallaxes otherwise. They are compared with masses deduced from spectral types. Other physical and orbital properties are also considered.