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In recent years, the escalating risk of natural disasters caused by Near-Earth Objects (NEOs) has garnered heightened scrutiny, particularly in the aftermath of the 2013 Chelyabinsk event. This has prompted increased interest from governmental and supranational entities, leading to the formulation of various measures and strategies aimed at mitigating the potential threat posed by NEOs. This paper delves into the analysis of the 2011 AG5 asteroid within the context of small celestial bodies (e.g., asteroids, comets, or meteoroids) exhibiting resonant orbits with Earth's heliocentric revolution. Initial observations in 2011 raised alarms regarding the asteroid's orbital parameters, indicating a significant risk of Earth impact during its resonant encounter in 2040. Subsequent observations, however, mitigated these concerns. Here, we manipulate the orbital elements of the 2011 AG5 asteroid to simulate its behavior as a virtual impactor (a virtual asteroid whose orbit could impact Earth). This modification facilitates the assessment of impact mitigation resulting from a deflection maneuver utilizing a kinetic impactor. The deflection maneuver, characterized as an impulsive change in the asteroid's momentum, is executed during a resonant encounter occurring approximately two decades before the potential impact date. The paper systematically evaluates the dependence of the deflection maneuver's efficacy on critical parameters, including the position along the orbit, epoch, and momentum enhancement factor. [ABSTRACT FROM AUTHOR]

In the exploration of celestial bodies, including planets, moons, and asteroids, it is useful to identify stable orbits in which the orbital elements remain, on average, constant (referred to as frozen orbits). This paper aims to investigate the feasibility of frozen orbits for a small body, such as a probe, orbiting a main body under the perturbation due to the gravitational attraction of an inner third-body, on a circular (or slightly eccentric) orbit coplanar with the main body equator, by means of an approach based on mean element theory. The disturbing potential has been developed in Legendre polynomials up to order l = 5 (triakontadipole level of approximation). Thus, the double-averaged potential function and the associated constants of motion have been determined up to the same order. Then, by applying the Lagrange Planetary Equations, the secular and long-term orbital element variations have been obtained. Therefore, frozen orbital solutions have been evaluated, and the effects on them of the addition of main body oblateness perturbation have been considered. Furthermore, the procedure has been repeated, and the frozen solutions are re-evaluated in the case of a disturbing body with small eccentricity up to order l = 4 (hexadecapole level of approximation). These solutions offer significant advantages in exploring bodies subject to a notable perturbation from an inner third-body, such as binary asteroid systems. • Frozen orbits for the inner third-body problem. • Inner circular planar third-body: Double-averaged potential up to triakontadipole. • Inner slightly eccentric planar third-body up to hexadecapole. • Orbital solutions for binary asteroid observation. [ABSTRACT FROM AUTHOR]

• An averaged approach is considered to obtain first guess solutions for science orbits. • Dynamical properties are determined by exploiting two prime integrals of motion. • A numerical investigation has been carried out to gain the precise initial conditions leading to the longest lifetimes for a probe orbiting Ganymede. An important aspect concerning the dynamics of a probe around a natural satellite is represented by the probe lifetime. In fact, the science orbits, usually characterised by low altitude and high inclination, are subjected to an important increase in eccentricity, due to the mother planet's gravitational attraction, which can lead the probe to collide with the surface of the natural satellite. In the present work, the issue is addressed at the Jupiter's moon Ganymede, which represents one of most important targets in the exploration of the Solar System. Thus, taking advantage from theoretical aspects and analytical relationships concerning the evolution of the mean orbit elements of the probe, a numerical investigation aimed at determining the initial conditions of the probe orbit which allow the longest lifetime has been carried out. [ABSTRACT FROM AUTHOR]

The High Energy Modular Ensemble of Satellites (HERMES) project intends to build an all-sky monitor operating from keV to MeV for the detection and localisation of transient events, like gamma ray bursts. HERMES is a modular observatory composed by detectors on-board of nanosatellites. HERMES aims to revolutionise the world of multi-messenger astrophysics thanks to the innovative concept of a modular instrument based on small satellites and characterised by reduced design and development times and low costs, in the face of high technological content and scientific profile of the mission. A first part of the project, HERMES Technological Pathfinder, composed of three CubeSats, aims to demonstrate the feasibility of detecting transient phenomena in high energy with small satellites. The next phase of the project, HERMES Scientific Pathfinder, will expand the constellation up to six satellites, allowing routinely accurate triangulation measurements. This paper presents an analysis that aims to be propaedeutic for the design of the final HERMES Full Constellation, which will be an all-sky monitor made up of tens/hundreds of nanosatellites in Low Earth Orbit with a total effective area of ∼ m 2. An adequate number of nanosatellites, simultaneously detecting a transient, provides a source localisation accuracy of the order of magnitude of few arcmin and large effective area. The objective of this work is to define possible strategies of injection in orbit of the complete constellation. In this first analysis we used only the number of triangulable Gamma Ray Bursts (simultaneously detected by at least three nanosatellites) as discriminating factor in order to maximise the constellation performance. By achieving the goal of at least a mean number of 20 Gamma Ray Bursts triangulated per nanosatellite over the two years life-time, optimal configurations for the complete constellation, consisting of seven to fourteen CubeSats, have been identified. • High Energy Modular Ensemble of Satellites (HERMES) mission. • Propaedeutic analysis for the design of the final Full Constellation. • Nanosatellites constellation for fast detection and positioning of Gamma Ray Bursts. • All-sky coverage constellation based on small satellites in Low Earth Orbit. • Maximisation of Gamma Ray Bursts triangulable during the lifetime by each satellite. • Robustness analysis: atmospheric drag, solar radiation pressure and early failures. [ABSTRACT FROM AUTHOR]

In this paper, the feasibility of exploiting the Sun's gravitational force to design the final phase (capture and orbit circularisation) to Mercury with a low propellant consumption has been investigated. The initial conditions, on the eccentricity and argument of pericentre, for the circularisation phase are obtained from a prime integral of motion, which takes place when the probe moves over a polar orbit. A numerical analysis has highlighted how these initial conditions allow, under the third-body effect, an optimal reduction of eccentricity (circularisation phase) with limited variations of the other orbit elements, without requiring orbital manoeuvres. Then, by introducing a small velocity variation, the phase of ballistic capture has been joined to the circularisation phase. The obtained results can encourage the exploitation of this phenomenon in future missions for the exploration of Mercury. [ABSTRACT FROM AUTHOR]

Abstract Due to conservative design models and safe construction practices, infrastructure usually has unknown amounts of reserve capacity that exceed code requirements. Quantification of this reserve capacity has the potential to lead to better asset-management decisions by avoiding unnecessary replacement and by lowering maintenance expenses. However, such quantification is challenging due to systematic uncertainties that are present in typical structural models. Field measurements, collected during load tests, combined with good structural-identification methodologies may improve the accuracy of model predictions. In most structural-identification tasks, engineers usually select and place sensors based on experience and high signal-to-noise estimations. Since the success of structural identification depends on the measurement system, research into measurement system design has been carried out over several decades. Despite the multi-criteria nature of the problem, most researchers have focused only on the information gained by the measurement system. This study presents a framework to evaluate and rank possible measurement-system designs based on a tiered multi-criteria strategy. Performance criteria for the design of measurement systems include monitoring costs, information gain, ability to detect outliers and impact of loss of information in case of sensor failure. Through including conflicting criteria, such as cost of monitoring and information gain, the optimal measuring system becomes a Pareto-like choice that ultimately depends on asset-manager preference hierarchies. Several potential preference scenarios are generated and results are compared using a full-scale test study, the Exeter Bascule Bridge. The framework successfully supports an informed design of measurement systems by providing an extensive set of alternatives, including the best solution defined probabilistically and for specific conditions when other near-optimal solutions might be preferred. [ABSTRACT FROM AUTHOR]

To improve lunar landing performances in terms of mission costs, trajectory determination and visibility the use of a single probe located over an assistance orbit around the Moon has been taken into consideration. To this end, the properties of two quasi-circular orbits characterised by a stable behaviour of semi-major axis, eccentricity and inclination have been investigated. The analysis has demonstrated the possibility of using an assistance probe, located over one of these orbits, as a relay satellite between lander and Earth, even in the case of landings on the far side of the Moon. A comparison about the accuracy in retrieving the lander’s state with respect to the use of a probe located in the Lagrangian point L2 of the Earth-Moon system has also been carried out. [ABSTRACT FROM AUTHOR]

Following an approach based on ground track analysis, original and compact relationships which permit the construction of ground track patterns and the determination of satellite arrangements able to generate appropriate track distance and revisit frequency over a given area are presented. These equations are valid in the general case of elliptical orbit and can easily be implemented in computer codes devoted to the design of single and multi-plane satellite constellations. [ABSTRACT FROM AUTHOR]

This paper proposes a robustness analysis based on Multiple Criteria Decision Aiding (MCDA). The ensuing model was used to assess the implementation of green chemistry principles in the synthesis of silver nanoparticles. Its recommendations were also compared to an earlier developed model for the same purpose to investigate concordance between the models and potential decision support synergies. A three-phase procedure was adopted to achieve the research objectives. Firstly, an ordinal ranking of the evaluation criteria used to characterize the implementation of green chemistry principles was identified through relative ranking analysis. Secondly, a structured selection process for an MCDA classification method was conducted, which ensued in the identification of Stochastic Multi-Criteria Acceptability Analysis (SMAA). Lastly, the agreement of the classifications by the two MCDA models and the resulting synergistic role of decision recommendations were studied. This comparison showed that the results of the two models agree between 76% and 93% of the simulation set-ups and it confirmed that different MCDA models provide a more inclusive and transparent set of recommendations. This integrative research confirmed the beneficial complementary use of MCDA methods to aid responsible development of nanosynthesis, by accounting for multiple objectives and helping communication of complex information in a comprehensive and traceable format, suitable for stakeholders and/or decision-makers with diverse backgrounds. [ABSTRACT FROM AUTHOR]

Nanotechnology applications (nanoproducts) have entered the market or are expected to do so in the near future. Robust and science-based criteria are required to appraise and manage their sustainability. This paper describes the approach used to develop a comprehensive and reliable framework of criteria, which was missing until now, for evaluating the sustainability of nanoproducts. A literature review of the frameworks and tools employed to assess nanoproducts sustainability implications was firstly performed to select an initial set of criteria. A survey of experts in the sustainable nanotechnology domain was then conducted to elicit their knowledge in terms of completeness, reliability and validity of the criteria set. Ranking and correlation analyses completed the research by identifying the parameters of major interest as well as the links and dependencies between them. A total of 54 and 65 experts replied to the pilot and main survey, respectively. The reliability and validity of the criteria was assessed with the responses from both questionnaires, whereas the answers from the main survey were used to calculate the relative index of the criteria as well as their correlations. This research resulted in a framework composed of 68 criteria, which are structured into six main areas: (i) economic performance; (ii) environmental impacts, (iii) environmental risk assessment; (iv) human health risk assessment; (v) social implications and (vi) technical performance. This study helps to broaden the understanding on the identification of criteria for sustainability assessments. It also provides those interested in evaluating nanotechnology implications with the basis for real case studies, possibly by integrating available information with the stakeholders using tools that support decision-making. [ABSTRACT FROM AUTHOR]

The determination of analytical expressions which, including the main perturbative effects, allow the retrieval of the orbit elements of a probe represents an important requirement in designing science trajectories. One of these perturbations is given by the third body attraction. The case in which the perturbing body moves on a plane coincident with the equatorial plane of the primary body has been investigated in previous studies and equations able to provide the temporal evolution of the orbit elements have been determined and applied to the main moons of the Solar System. In this paper an extension of this topic has been carried out and equations which allow the determination of the orbit evolution have been analytically retrieved in the general case in which one or more perturbing bodies describe elliptical and inclined orbits with respect to the equatorial plane of the primary. Then, introducing these equations into the periodicity condition for the probe ground track, and considering the $$J_{2}$$ and $$J_{4}$$ effects coming from the primary body, an equation able to provide repeating ground track orbits has been determined. [ABSTRACT FROM AUTHOR]

In this paper, the design of science orbits for the observation of a celestial body has been carried out using polynomial equations. The effects related to the main zonal harmonics of the celestial body and the perturbation deriving from the presence of a third celestial body have been taken into account. The third body describes a circular and equatorial orbit with respect to the primary body and, for its disturbing potential, an expansion in Legendre polynomials up to the second order has been considered. These polynomial equations allow the determination of science orbits around Jupiter's satellite Europa, where the third body gravitational attraction represents one of the main forces influencing the motion of an orbiting probe. Thus, the retrieved relationships have been applied to this moon and periodic sun-synchronous and multi-sun-synchronous orbits have been determined. Finally, numerical simulations have been carried out to validate the analytical results. [ABSTRACT FROM AUTHOR]

The assessment of the implementation of green chemistry principles in the syntheses of nanomaterials is a complex decision-making problem that necessitates the integration of several evaluation criteria. Multiple Criteria Decision Aiding (MCDA) provides support for such a challenge. One of its methods – Dominance-based Rough Set Approach (DRSA) – was used in this research to develop a model for the green chemistry-based classification of silver nanoparticle synthesis protocols into preference-ordered performance classes. DRSA allowed integration of knowledge from both peer-reviewed literature and experts (decision makers, DMs) in the field, resulting in a model composed of decision rules that are logical statements in the form: “if conditions, then decision”. The approach provides the basis for the design of rules for the greener synthesis of silver nanoparticles. Decision rules are supported by synthesis protocols that enforce the principles of green chemistry to various extents, resulting in robust recommendations for the development and assessment of silver nanoparticle synthesis that perform at one of five pre-determined levels. The DRSA-based approach is transparent and structured and can be easily updated. New perspectives and criteria could be added into the model if relevant data were available and domain-specific experts could collaborate through the MCDA procedure. [ABSTRACT FROM AUTHOR]

Sustainability assessments require the management of a wide variety of information types, parameters and uncertainties. Multi criteria decision analysis (MCDA) has been regarded as a suitable set of methods to perform sustainability evaluations as a result of its flexibility and the possibility of facilitating the dialogue between stakeholders, analysts and scientists. However, it has been reported that researchers do not usually properly define the reasons for choosing a certain MCDA method instead of another. Familiarity and affinity with a certain approach seem to be the drivers for the choice of a certain procedure. This review paper presents the performance of five MCDA methods (i.e. MAUT, AHP, PROMETHEE, ELECTRE and DRSA) in respect to ten crucial criteria that sustainability assessments tools should satisfy, among which are a life cycle perspective, thresholds and uncertainty management, software support and ease of use. The review shows that MAUT and AHP are fairly simple to understand and have good software support, but they are cognitively demanding for the decision makers, and can only embrace a weak sustainability perspective as trade-offs are the norm. Mixed information and uncertainty can be managed by all the methods, while robust results can only be obtained with MAUT. ELECTRE, PROMETHEE and DRSA are non-compensatory approaches which consent to use a strong sustainability concept, accept a variety of thresholds, but suffer from rank reversal. DRSA is less demanding in terms of preference elicitation, is very easy to understand and provides a straightforward set of decision rules expressed in the form of elementary “if … then …” conditions. Dedicated software is available for all the approaches with a medium to wide range of results capability representation. DRSA emerges as the easiest method, followed by AHP, PROMETHEE and MAUT, while ELECTRE is regarded as fairly difficult. Overall, the analysis has shown that most of the requirements are satisfied by the MCDA methods (although to different extents) with the exclusion of management of mixed data types and adoption of life cycle perspective which are covered by all the considered approaches. [ABSTRACT FROM AUTHOR]

Composite Indicators (CIs, a.k.a. indices) are increasingly used as they can simplify interpretation of results by condensing the information of a plurality of underlying indicators in a single measure. This paper demonstrates that the strength of the correlations between the indicators is directly linked with their capacity to transfer information to the CI. A measure of information transfer from each indicator is proposed along with two weight-optimization methods, which allow the weights to be adjusted to achieve either a targeted or maximized information transfer. The tools presented in this paper are applied to a case study for resilience assessment of energy systems, demonstrating how they can support the tailored development of CIs. These findings enable analysts bridging the statistical properties of the index with the weighting preferences from the stakeholders. They can thus choose a weighting scheme and possibly modify the index while achieving a more consistent (by correlation) index. • Composite indicator development is enhanced with advanced statistical analysis. • Tools to assess the information transferred from indicators to the index are proposed. • Two weight-optimization methods allow adjusting information transfer to the index. • The approaches are applied to a real case study on resilience of electricity supply. [ABSTRACT FROM AUTHOR]

This study proposes a set of key decision-making features of the contaminated site remediation process to assist in selecting the most appropriate decision support method(s). Using a case study consistent with the requirements of the U.S. regulation for contaminated sites management, this article shows that suitable Multiple Criteria Decision Analysis methods can be selected based on a dynamic and evolving problem structuring. The selected methods belong to the family of PROMETHEE methods and can provide ranking recommendations of the considered alternatives using variable structures of the criteria, evaluation of the alternatives and exploitation of the preference model. It was found that in order to support a quick and up-to-date application of powerful decision support techniques in the process of remediation of contaminated sites, decision analysts and stakeholders should interact and co-develop the process. This research also displays how such interactions can guarantee a transparent and traceable decision recommendation so that stakeholders can better understand why some alternatives perform comprehensively better than others when a multitude of inputs is used in the decision-making process. • Decision-making features for remediation of contaminated sites are proposed. • Decision analysis is used to aid the process of contaminated sites management. • The proposed approach is consistent with the relevant U.S. regulation. • Decision analysts and stakeholders should co-develop remediation processes. • A case study for land remediation is used to dynamically rank target alternatives. [ABSTRACT FROM AUTHOR]

The interest in studying energy systems' resilience is increasing due to a rising awareness of the importance of having a secure energy supply. This growing trend is a result of a series of recent disruptions, among others also affecting electricity systems. Therefore, it is of crucial importance for policymakers to determine whether their country has a resilient electricity supply. Starting from a set of 12 indicators, this paper uses data envelopment analysis (DEA) to comprehensively evaluate the electricity supply resilience of 140 countries worldwide. Two DEA models are applied: (1) the original ratio-based Charnes, Cooper, and Rhodes (CCR) model and (2) a novel hybrid framework for robust efficiency analysis incorporating linear programming and Monte Carlo simulations. Results show that the CCR model deems 31 countries as efficient and hence lacks the capability to differentiate them. Furthermore, the CCR model considers only the best weight vectors for each country, which are not necessarily representative of the overall performance of the countries. The robustness analysis explores these limitations and identifies South Korea, Singapore and Canada as the most resilient countries. Finally, country analyses are conducted, where Singapore's and Japan's performances and improvement potentials are discussed. [ABSTRACT FROM AUTHOR]

The impacts of energy accidents are of primary interest for risk and resilience analysts, decision makers, and the general public. They can cause human health and environmental impacts, economic and societal losses, which justifies the interest in developing models to mitigate these adverse outcomes. We present a classification model for sorting energy accidents in the natural gas sector into hazard classes, according to their potential fatalities. The model is built on decision rules, which are knowledge blocks in the form of "if (condition), then (classification to hazard class x)". They were extracted by the rough sets method using natural gas accident data from 1970–2016 of the Energy-related Severe Accident Database (ENSAD) of the Paul Scherrer Institut (PSI), the most authoritative information source for accidents in the energy sector. This was the first attempt to explore the relationships between the descriptors of energy accidents and the consequence (fatalities). The model was applied to a set of hypothetical accidents to show how the decision-making process could be supported when there is an interest in knowing which class (i.e., low, medium, high) of fatalities an energy accident could cause. The successful use of this approach in the natural gas sector proves that it can be also adapted for other energy chains, such as oil and coal. [ABSTRACT FROM AUTHOR]

Background: To date (April 2021), medical device (MD) design approaches have failed to consider the contexts where MDs can be operationalised. Although most of the global population lives and is treated in Low- and Middle-Income Countries (LMCIs), over 80% of the MD market share is in high-resource settings, which set de facto standards that cannot be taken for granted in lower resource settings. Using a MD designed for high-resource settings in LMICs may hinder its safe and efficient operationalisation. In the literature, many criteria for frameworks to support resilient MD design were presented. However, since the available criteria (as of 2021) are far from being consensual and comprehensive, the aim of this study is to raise awareness about such challenges and to scope experts' consensus regarding the essentiality of MD design criteria.Results: This paper presents a novel application of Delphi study and Multiple Criteria Decision Analysis (MCDA) to develop a framework comprising 26 essential criteria, which were evaluated and chosen by international experts coming from different parts of the world. This framework was validated by analysing some MDs presented in the WHO Compendium of innovative health technologies for low-resource settings.Conclusions: This novel holistic framework takes into account some domains that are usually underestimated by MDs designers. For this reason, it can be used by experts designing MDs resilient to low-resource settings and it can also assist policymakers and non-governmental organisations in shaping the future of global healthcare. [ABSTRACT FROM AUTHOR]

The JUpiter ICy moons Explorer mission of the European Space Agency, that will be launched in the year 2022, will study the geodesy and physical characteristics of Jupiter and its icy moons Europa, Callisto and Ganymede. The final phase of this mission, planned for the year 2032, is still under investigation and foresees phases in circular orbit around Ganymede. In this paper two types of science orbits around Ganymede, that optimize the observational performances and the probe life-time, are proposed. While the first type allows, at “zero cost”, the obtaining of repeated observations of a given point of the surface, the second type, with a limited cost, adds to the periodicity of observation, the condition of synchronism with the Sun. This synchronism permits both the achievement of a condition of permanent sunlight for the probe, thus leading to an extension of the mission duration, and a minimization of the variations of spectral signature due to the Sun's position. [ABSTRACT FROM AUTHOR]

Substantial limitations and uncertainties hinder the exposure assessment of engineered nanomaterials (ENMs). The present deficit of reliable measurements and models will inevitably lead in the near term to qualitative and uncertain exposure estimations, which may fail to support adequate risk assessment and management. Therefore it is necessary to complement the current toolset with user-friendly methods for near-term nanosafety evaluation. This paper proposes an approach for relative exposure screening of ENMs. For the first time, an exposure model explicitly implements quantitative weight of evidence (WoE) methods and utilises expert judgement for filling data gaps in the available evidence-base. Application of the framework is illustrated for screening of exposure scenarios for nanoscale titanium dioxide, carbon nanotubes and fullerenes, but it is applicable to other nanomaterials as well. The results show that the WoE-based model overestimates exposure for scenarios where expert judgement was substantially used to fill data gaps, which suggests its conservative nature. In order to test how variations in input data influence the obtained results, probabilistic Monte Carlo sensitivity analysis was applied to demonstrate that the model performs in stable manner. [ABSTRACT FROM AUTHOR]

We consider a problem of multi-decision sorting subject to multiple criteria. In the newly formulated decision problem, besides performances on multiple criteria, alternatives get evaluations on multiple interrelated decision attributes involving preference-ordered classes. We propose a dedicated method for dealing with such a problem, incorporating a threshold-based value-driven sorting procedure. The Decision Maker (DM) is expected to holistically evaluate a subset of reference alternatives by indicating the quality or risk level on a pre-defined scale of each decision attribute. Based on these evaluations, we construct a set of interrelated preference models, one for each decision attribute, compatible with intra- and inter-decision constraints imposed by such indirect preference information. We also formulate a new way of dealing with potentially non-monotonic criteria by discovering local monotonicity changes in different performance scale regions. The marginal value functions for criteria with unknown monotonicity are represented as a sum of two value functions assuming opposing preference directions, one non-decreasing and the other non-increasing. This permits to obtain an aggregated marginal value function with an arbitrary non-monotonic shape. The practical usefulness of the approach is demonstrated on a case study concerning risk management related to handling (i.e., production, use, manipulation, and processing) nanomaterials in different conditions. We analyze the expert judgments and discuss the inferred preference models, which can be applied to support health and safety managers in reducing the possible risk associated with the respective exposure scenario. • We introduce a problem of multi-decision sorting in Multi-Criteria Decision Analysis. • We propose a dedicated value-driven threshold-based preference disaggregation method. • We translate the assignment examples into intra- and inter-decision constraints. • We consider a study on the nanomaterials' exposure management in various conditions. • We propose a new way of dealing with potentially non-monotonic criteria. [ABSTRACT FROM AUTHOR]

• A structured approach for robustness assessment of rankings is proposed. • Resilience of electricity supply security is analyzed for 140 countries. • 12 resilience-related indicators are quantified using a structured methodology. • 38 combinations of normalization methods and aggregation functions are applied. • General ranking trends and different levels of compensation are identified. Indicator-based approaches are suitable to assess multi-dimensional problems. In order to compare a set of alternatives, one strategy is to normalize individual indicators to a common scale and aggregate them into a comprehensive score. This study proposes the Electricity Supply Resilience Index (ESRI), which is a measure of a nation's electricity supply resilience. Starting from an initial set of individual indicators derived through a structured selection process, the ESRI is calculated for 140 countries worldwide. To account for robustness of the resulting resilience index, 38 combinations of eight normalization methods and six aggregation functions were considered. Results show a clear country ranking trend, with robust top- and low-performing countries across all combinations. However, the ranking disparity becomes large for average performing countries, especially if their indicators show high variability. Furthermore, the differences of the rankings are quantified through the Rank Difference Measure (RDM), which identifies the categorical scales and the minimum aggregator as the most different ones. Finally, the effects of different compensation levels of the aggregation functions are discussed. The findings of the present study aim to provide recommendations for policymakers on how composite indexes results depend on assumptions and chosen approaches. [ABSTRACT FROM AUTHOR]

Performances of a planetary observation system are strongly related to the choice of the orbit used. Trajectories with characteristics of periodicity are very useful for the assessment of time-varying phenomena and thus Periodic SunSynchronous and Periodic Multi-SunSynchronous Orbits are particularly suitable to this end. In this paper, the research into these kinds of orbits, previously proposed for the Earth and Mars, has been extended to planets of the Solar System and to their principal moons. In general, these trajectories are typically obtained under the hypothesis that the J harmonic is predominant with respect to the other orbital perturbations, since this allows an analytical solution. However, the hypothesis of J predominant is not always verified in the Solar System and so analytical techniques must be replaced by numerical simulations. Interesting results have been obtained for the planets Mars and Jupiter and for the moons Europa, Callisto and Titan, where periodic trajectories with reduced revisit times and low altitudes have been found. These solutions allow the observation of time-varying phenomena with high spatial and temporal resolution. [ABSTRACT FROM AUTHOR]