Distributed Spacecraft Path Planning and Collision Avoidance via Reciprocal Velocity Obstacle Approach

This paper presents the development of a combined linear quadratic regulation and reciprocal velocity obstacle (LQR/RVO) control algorithm for multiple satellites during close proximity operations. The linear quadratic regulator (LQR) control effort drives the spacecraft towards their target position while the reciprocal velocity obstacle (RVO) provides collision avoidance capabilities. Each spacecraft maneuvers independently, without explicit communication or knowledge in term of collision avoidance decision making of the other spacecraft in the formation. To assess the performance of this novel controller different test cases are implemented. Numerical results show that this method guarantees safe and collision-free maneuvers for all the satellites in the formation and the control performance is presented in term of Δv and fuel consumption

Caracterización fitoquímica de la especie Ilex guayusa Loes. y elaboración de un prototipo de fitofármaco de interés comercial

De los 17 países megadiversos del mundo cuatro de ellos se ubican en la zona andina y concentran el 75% de la diversidad en especies de animales y plantas, estos son: Colombia, Perú, Venezuela y Ecuador (Estrella et al. 2005). La Amazonía ecuatoriana representa una de las áreas con mayor biodiversidad del planeta y por su enorme variedad de plantas se convierte en una fuente de investigación de interés permanente, especialmente para el desarrollo de nuevas materias primas del mercado farmacéutico, cosmético y alimentario. Al interés comercial se unen también el científico y el antropológico, sobre todo cuando se trata de recuperar una de las plantas sagradas de las nacionalidades indígenas que habitan en la región amazónica ecuatoriana conocida con el nombre vernáculo de guayusa (Ilex guayusa Loes.) y que es usada tradicionalmente por los Achuar y mestizos en forma de infusión

Electromagnetic Formation Flying with Eccentric Reference Orbits

Over the last decade, a considerable amount of research work has been done in the area of spacecraft formation flight, with particular emphasis on control techniques using thruster-based systems. Nevertheless, thrusters require propellant to work and this limit the lifetime of the mission. Electromagnetic Formation Flight (EMFF) is presented in this paper as a fuel-less strategy to control spacecraft formations by means of electromagnets. In EMFF, spacecraft can be equipped with one or more coils and reactions wheels which could be arranged in several combinations according to mission requirements. An electric current flows through the coils in order to produce a magnetic dipole in a specific direction. The magnetic field of a spacecraft reacts against the magnetic dipoles of the others, generating forces and torques which in turn could be used as control inputs. The main objective of this paper is to provide a formulation for EMFF when a formation is moving in eccentric reference orbits and for this purpose, the Tschauner and Hempel model will be used. Results are presented after analysing different formation scenarios providing the necessary magnetic requirements for station keeping and resolving which cases are suitable to be controlled by this technology. High-Temperature Semiconductor (HTS) plays an important role in EMFF and for that reason the paper also investigates the correlation of the magnetic force and the coil mass, which in turn affects the total mass of the spacecraft

Orbital dynamics of large solar power satellites

Designs for geostationary SPS are extremely large in scale, more than an order of magnitude larger than the International Space Station. The problem of how to control the orbital motion of such large structures, accounting for various perturbing forces, is therefore a topic worthy of further study. The primary objective of the proposed research is to perform a detailed study of SPS orbit dynamics, obtaining a comprehensive understanding of the effect of perturbations on orbits of large SPS structures over a time-frame commensurate with proposed SPS lifetimes (30-40 years). Analytical equations derived by the process of averaging of the SPS equations of motion shall be used in determining the long-term orbital behaviour. Previous studies have simply assumed a geostationary orbit (GEO) then designed control systems for maintaining it thus. It is found that an alternative SPS orbital location known as the geosynchronous Laplace plane (GLP) is superior to GEO. An SPS in GLP requires virtually no fuel to maintain its orbit, avoids the main orbital debris population originating from GEO satellites and is extremely robust, i.e. loss of control is inconsequential. The GLP SPS saves of order 10<sup>4</sup> to 10<sup>5</sup> kg per year in fuel compared to a GEO SPS for equivalent power delivery compared to GEO

Towards Designing a Credible Hazardous NEA Mitigation Campaign of Dual-deflection Act

Given a limited warning time, an asteroid impact mitigation campaign would hinge on uncertainty-based information consisting of remote observational data of the identified Earth-threatening object, general knowledge on near-Earth asteroids, and engineering judgment. Due to these ambiguities, the campaign credibility could be profoundly compromised. It is therefore imperative to comprehensively evaluate the inherent uncertainty in deflection and plan the campaign accordingly to ensure successful mitigation. This research demonstrates dual-deflection mitigation campaigns consisting of primary and secondary deflection missions, where both deflection performance and campaign credibility are taken into consideration. The results of the dual-deflection campaigns show that there are trade-offs between the competing aspects: the total interceptor mass, interception time, deflection distance, and the confidence in deflection. The design approach is found to be useful for multi-deflection campaign planning, allowing us to select the best possible combination of deflection missions from a catalogue of various mitigation campaign options, without compromising the campaign credibility

Hazardous Near Earth Asteroid Mitigation Campaign Planning Based on Uncertain Information on Asteroid Physical Properties

Given a limited warning time, an asteroid impact mitigation campaign would hinge on uncertainty-based information consisting of remote observational data of the identified Earth-threatening object, general knowledge on near-Earth asteroids (NEAs), and engineering judgment. Due to these ambiguities, the campaign credibility could be profoundly compromised. It is therefore imperative to comprehensively evaluate the inherent uncertainty in deflection and plan the campaign accordingly to ensure successful mitigation. This research demonstrates dual-deflection mitigation campaigns consisting of primary and secondary deflection missions, where both deflection performance and campaign credibility are taken into consideration. The results of the dual-deflection campaigns show that there are trade-offs between the competing aspects: the total interceptor mass, interception time, deflection distance, and the confidence in deflection. The design approach is found to be useful for multi-deflection campaign planning, allowing us to select the best possible combination of deflection missions from a catalogue of various mitigation campaign options, without compromising the campaign credibility

Investigating SAR algorithm for spaceborne interferometric oil spill detection

The environmental damages and recovery of terrestrial ecosystems from oil spills can last decades. Oil spills have been responsible for loss of aquamarine lives, organisms, trees, vegetation, birds and wildlife. Although there are several methods through which oil spills can be detected, it can be argued that remote sensing via the use of spaceborne platforms provides enormous benefits. This paper will provide more efficient means and methods that can assist in improving oil spill responses. The objective of this research is to develop a signal processing algorithm that can be used for detecting oil spills using spaceborne SAR interferometry (InSAR) data. To this end, a pendulum formation of multistatic smallSAR carrying platforms in a near equatorial orbit is described. The characteristic parameters such as the effects of incidence angles on radar backscatter, which support the detection of oil spills, will be the main drivers for determining the relative positions of the small satellites in formation. The orbit design and baseline distances between each spaceborne SAR platform will also be discussed. Furthermore, results from previous analysis on coverage assessment and revisit time shall be highlighted. Finally, an evaluation of automatic algorithm techniques for oil spill detection in SAR images will be conducted and results presented. The framework for the automatic algorithm considered consists of three major steps. The segmentation stage, where techniques that suggest the use of thresholding for dark spot segmentation within the captured InSAR image scene is conducted. The feature extraction stage involves the geometry and shape of the segmented region where elongation of the oil slick is considered an important feature and a function of the width and the length of the oil slick. For the classification stage, where the major objective is to distinguish oil spills from look-alikes, a Mahalanobis classifier will be used to estimate the probability of the extracted features being oil spills. The validation process of the algorithm will be conducted by using NASA’s UAVSAR data obtained over the Gulf of coast oil spill and RADARSAT-1 dat

A deformation model of flexible, HAMR objects for accurate propagation under perturbations and the self-shadowing effects

A new type of space debris in near geosynchronous orbit (GEO) was recently discovered and later identified as exhibiting unique characteristics associated with high area-to-mass ratio (HAMR) objects, such as high rotation rates and high reflection properties. Observations have shown that this debris type is very sensitive to environmental disturbances, particularly solar radiation pressure, due to the fact that its motion depends on the actual effective area, orientation of that effective area, reflection properties and the area-to-mass ratio of the object is not stable over time. Previous investigations have modelled this type of debris as rigid bodies (constant area-to-mass ratios) or discrete deformed body; however, these simplifications will lead to inaccurate long term orbital predictions. This paper proposes a simple yet reliable model of a thin, deformable membrane based on multibody dynamics. The membrane is modelled as a series of flat plates, connected through joints, representing the flexibility of the membrane itself. The mass of the membrane, albeit low, is taken into account through lump masses at the joints. The attitude and orbital motion of this flexible membrane model is then propagated near GEO to predict its orbital evolution under the perturbations of solar radiation pressure, Earth’s gravity field (J2), third body gravitational fields (the Sun and Moon) and self-shadowing. These results are then compared to those obtained for two rigid body models (cannonball and flat rigid plate). In addition, Monte Carlo simulations of the flexible model by varying initial attitude and deformation angle (different shape) are investigated and compared with the two rigid models (cannonball and flat rigid plate) over a period of 100 days. The numerical results demonstrate that cannonball and rigid flat plate are not appropriate to capture the true dynamical evolution of these objects, at the cost of increased computational time

Electromagnetic Formation Flying with Eccentric Reference Orbits

Over the last decade, a considerable amount of research work has been done in the area of spacecraft formation flight, with particular emphasis on control techniques using thruster-based systems. Nevertheless, thrusters require propellant to work and this limit the lifetime of the mission. Electromagnetic Formation Flight (EMFF) is presented in this paper as a fuel-less strategy to control spacecraft formations by means of electromagnets. In EMFF, spacecraft can be equipped with one or more coils and reactions wheels which could be arranged in several combinations according to mission requirements. An electric current flows through the coils in order to produce a magnetic dipole in a specific direction. The magnetic field of a spacecraft reacts against the magnetic dipoles of the others, generating forces and torques which in turn could be used as control inputs. The main objective of this paper is to provide a formulation for EMFF when a formation is moving in eccentric reference orbits and for this purpose, the Tschauner and Hempel model will be used. Results are presented after analysing different formation scenarios providing the necessary magnetic requirements for station keeping and resolving which cases are suitable to be controlled by this technology. High-Temperature Semiconductor (HTS) plays an important role in EMFF and for that reason the paper also investigates the correlation of the magnetic force and the coil mass, which in turn affects the total mass of the spacecraft

Studi di attivita’ biologica cosmeceutica di derivati di specie della zona sud orientale amazzonica ecuadoriana

The South American Natives, Shuar and Achuar people and their ethnomedical culture constituted the background subject of the PhD research, performed both in Ecuador (Salesian Politechnic University, Quito), and in Italy (Pharmaceutical biology labs, University of Ferrara). Based on ethnomedical and ethnocosmetic tradition, Oenocarpus bataua was chosen as Amazonian plant speciessubject of the research. Cosmetic plant derivatives were selected, extracted, characterized and studied. AIMS The research has been focused on: . Botanical source identification; . Selection and extraction of plant oil native of south eastern Ecuador; . Chemical characterization of selected oil; . Prototype development of cosmetic formulations employing Oenocarpus bataua oil; . Bioactivity assays regarding cosmetic applications; . Testing of alternatives extraction methods adequate to rural areas; . ECOCERT cosmetic prototypes; . GC-MS analysis of non-saponifiable fraction of O. bataua; . Oil purification studies by supercritical fluids; . Chemical and physical stability of ECOCERT cosmetic prototypes. RESULTS Oenocarpus bataua derivatives have potential cosmetic applications, in line with Natives Ecuadorian ethnocosmetic traditions. The oil extracted from the date pulp was chemically characterized and it showed a very similar composition to the olive oil. The extraction method does not influence significantly the oil composition and quality. Moreover the oil non-saponifiable fraction was investigated, together with the polar fraction. Cosmetic features were also studied; the O. bataua oil showed a high moisturizing property, while a low performance was recorded for cutaneous elasticity. Furthermore, 14 cosmetic products were developed and 3 emulsion products certifiable according to ECOCERT standards. The chemical and physical stability gave good results as well as the microbiological one achieved with preservatives permitted by the ECOCERT standards. CONCLUSIONS Many Amazonian species have a widespread ethnocosmetic potential. The studied species allowed us to isolate and chemically characterize the lipid fraction, one of the most interesting. The O. bataua oil showed a good moisturizing property and allows to produce diverse cosmetic formulations. In particular, the prototypes obtained following the ECOCERT standards have an important potential application for development of eco-friendly cosmetic supply chain from Amazonian origin