Attitude Control System for an Earth observation satellite

The objective of the research was to develop the Attitude Control System algorithm to be implemented in the Earth Observation Satellite System composed of leader-follower formation. The main task of the developed Attitude Control System is to execute attitude change manoeuvres required to point the axis of the image acquisition sensor to the fixed target on the Earth’s surface, while the satellite is within the segment of an orbit, where image acquisition is possible. Otherwise, the satellite maintains a nadir orientation. The control strategy is realized by defining the high-level operational modes and control laws to manage the attitude control actuators: magnetorquers used for desaturation of the reaction wheels and reaction wheels used for agile attitude variation. A six-degree-of-freedom satellite model was used to verify whether the developed Attitude Control System based on PID controllers for actuators performs attitude control in line with the requirements of an Earth Observation System. The simulations done for a variety of combinations of orbital parameters and surface target positions proved that the designed Attitude Control System fulfils the mission requirements with sufficient accuracy This high-level architecture supplemented by a more detailed control system model allowed proving efficient functionalities performance

Architectural optimization framework for earth-observing heterogeneous constellations : marine weather forecast case

Earth observation satellite programs are currently facing, for some applications, the need to deliver hourly revisit times, subkilometric spatial resolutions, and near-real-time data access times. These stringent requirements, combined with the consolidation of small-satellite platforms and novel distributed architecture approaches, are stressing the need to study the design of new, heterogeneous, and heavily networked satellite systems that can potentially replace or complement traditional space assets. In this context, this paper presents partial results from ONION, a research project devoted to studying distributed satellite systems and their architecting characteristics. A design-oriented framework that allows selecting optimal architectures for the given user needs is presented in this paper. The framework has been used in the study of a strategic use-case and its results are hereby presented. From an initial design space of 5586 potential architectures, the framework has been able to preselect 28 candidate designs by an exhaustive analysis of their performance and by quantifying their quality attributes. This very exploration of architectures and the characteristics of the solution space are presented in this paper along with the selected solution and the results of a detailed performance analysis.Postprint (author's final draft

Architectural optimization results for a network of earth-observing satellite nodes

Earth observation satellite programs are currently facing, for some applications, the need to deliver hourly revisit times, sub-kilometric spatial resolutions and near-real-time data access times. These stringent requirements, combined with the consolidation of small-satellite platforms and novel distributed architecture approaches, are stressing the need to study the design of new, heterogeneous and heavily networked satellite systems that can potentially replace or complement traditional space assets. In this context, this paper presents partial results from ONION, a research project devoted to study distributed satellite systems and their architecting characteristics. A design-oriented framework that allows selecting optimal architectures for a given user needs is presented in this paper. The framework has been used in the study of a strategic use-case and its results are hereby presented. From an initial design space of 5586 unique architectures, the framework has been able to pre-select 28 candidate designs by an exhaustive analysis of their performance and by quantifying their quality attributes. This very exploration of architectures and the characteristics of the solution space, are presented in this paper along with the selected solution and the results of a detailed performance analysis.Postprint (published version

Triterpenoid Saponins from Washnut (Sapindus mukorossi Gaertn.)—A Source of Natural Surfactants and Other Active Components

Sapindus mukorossi Gaertn., also called the washnut, is a tropical tree of the Sapindaceae family. The plant owes its name to its cleaning and washing properties used by the local population as a natural detergent. The most important ingredients of the plant are triterpenoid saponins contained in many parts of the plant, inducing fruits, galls, or roots. The tree also contains other valuable, biologically active compounds that are obtained by extraction methods. Raw or purified extract and isolated saponins are valuable plant products that can be used in the food, pharmaceutical, cosmetic, and chemical industries. This review includes the most important biological and surfactant properties of extracts and isolated saponins obtained from various parts of the plant

Generic Model of a Satellite Attitude Control System

A generic model of a nanosatellite attitude control and stabilization system was developed on the basis of magnetorquers and reaction wheels, which are controlled by PID controllers with selectable gains. This approach allows using the same architectures of control algorithms (and software) for several satellites and adjusting them to a particular mission by parameter variation. The approach is illustrated by controlling a satellite attitude in three modes of operation: detumbling after separation from the launcher, nominal operation when the satellite attitude is subjected to small or moderate disturbances, and momentum unloading after any reaction wheel saturation. The generic control algorithms adjusted to each mode of operation were implemented in a complete attitude control system. The control system model was embedded into a comprehensive simulation model of satellite flight. The simulation results proved the efficiency of the proposed approach

Comparison of algorithms for satellite attitude determination using data from visual sensors

The objective of the research was to investigate the efficiency of selected methods of data fusion from visual sensors used on-board satellites for attitude measurements. Data from a sun sensor, an earth sensor, and a star tracker were fused, and selected methods were applied to calculate satellite attitude. First, a direct numerical solution, a numerical and analytical solution of the Wahba problem, and the TRIAD method for attitude calculation were compared used for integrating data produced by a sun sensor and an earth sensor. Next, attitude data from the star tracker and earth/sun sensors were integrated using two methods: weighted average and Kalman filter. All algorithms were coded in the MATLAB environment and tested using simulation models of visual sensors. The results of simulations may be used as an indication for the best data fusion in real satellite systems. The algorithms developed may be extended to incorporate other attitude sensors like inertial and/or GNSS to form a complete satellite attitude system

Neutrophil Count as Atrioventricular Block (AVB) Predictor following Pediatric Heart Surgery

Neutrophils play a significant role in immune and inflammatory reactions. The preoperative inflammatory activation may have a detrimental effect on postoperative outcomes. The aim of the study was to investigate the relation between preoperative hematological indices on postoperative complications’ risk in pediatric cardiac congenital surgery. The retrospective single center analysis included 93 pediatric patients (48 (65%) males and 45 (35%) females), mean age of 7 (3–30) months referred for cardiac surgery in cardiopulmonary bypass due to functional single ventricle disease (26 procedures), shunts lesions (40 procedures) and cyanotic disease (27 procedures). Among simple hematological indices, the receiver-operating-characteristic curve showed that a neutrophil count below 2.59 K/uL was found as an optimal cut-off point for predicting postoperative atrioventricular block following pediatric cardiac surgery (AUC = 0.845, p p < 0.0001) for postoperative atrioventricular block in pediatric cardiac surgery

Mission and system architecture for an operational network of earth observation satellite nodes

Over the next few years, Europe will take important steps towards implementing the architecture of the Copernicus Space Component for Earth Observation (EO), fulfilling the needs of stakeholders concerned with land monitoring, marine monitoring, atmosphere monitoring, emergency management, security, and climate change. Nowadays, constellations and distributed networks of satellites are emerging as clear development trends in the space system market to enable augmentation, enhancement, and possibilities of new applications for future EO Missions. It is of paramount importance for Europe to properly analyse these trends and assess whether or not they could provide a competitive advantage for EO systems. The paper presents the mission and system architecture design of the H2020 ONION project, a European Union research activity that proposes a system concept to supplement in a progressive way the current European EO infrastructures and to serve emerging needs in an optimal fashion. Among several use cases considered, the ONION project focussed on proposing system architectures to provide competitive revisit time, data latency and image resolution for a demanding application scenario of interest: marine weather forecast (MWF). A set of promising system architectures has been subject of a comprehensive assessment, based on mission analysis expertise and detailed simulation for evaluating several key parameters such as revisit time and data latency of each measurement of interest, on-board memory evolution and power budget of each satellite of the constellation, ground station contacts and inter-satellite links. The architectures are built with several heterogeneous satellite nodes distributed in different orbital planes. Each platform can embark different instrument sets, which provide the required measurements for each use case. A detailed mission analysis has then been applied to the selected architecture for the MWF use case, including refined data flow analysis to optimize system resources; refined power budget analysis; delta-V and fuel budget analysis considering all the possible phases of the mission, encompassing correction of launcher injection errors and acquisition of nominal satellite position inside the constellation, orbit maintenance to control altitude, collision avoidance to avoid collision with space debris objects and end-of-life (EOL) disposal to comply with EOL guidelines. The relevance of the system architecture selected for the MWF has been evaluated for 3 use cases of interest (arctic sea-ice monitoring, maritime fishery pressure and aquaculture, agricultural hydric stress) to show the versatility and the feasibility of the chosen architecture to be adapted for other EO applications.Postprint (author's final draft

Mission and system architecture for an operational network of earth observation satellite nodes

© . This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Nowadays, constellations and distributed networks of satellites are emerging as clear development trends in the space system market to enable augmentation, enhancement, and possibilities of new applications for future Earth Observation (EO) missions. While the adoption of these satellite architectures is gaining momentum for the attaining of ever more stringent application requirements and stakeholder needs, the efforts to analyze their benefits and suitability, and to assess their impact for future programmes remains as an open challenge to the EO community. In this context, this paper presents the mission and system architecture conceived during the Horizon 2020 ONION project, a European Union research activity that proposes a systematic approach to the optimization of EO space infrastructures. In particular, ONION addressed the design of complementary assets that progressively supplement current programs and took part in the exploration of needs and implementation of architectures for the Copernicus Space Component for EO. Among several use cases considered, the ONION project focused on proposing system architectures to provide improved revisit time, data latency and image resolution for a demanding application scenario of interest: Marine Weather Forecast (MWF). A set of promising system architectures has been subject of a comprehensive assessment, based on mission analysis expertise and detailed simulation for evaluating several key parameters such as revisit time and data latency of each measurement of interest, on-board memory evolution and power budget of each satellite of the constellation, ground station contacts and inter-satellite links. The architectures are built with several heterogeneous satellite nodes distributed in different orbital planes. Each platform can embark different instrument sets, which provide the required measurements for each use case. A detailed mission analysis has then been performed to the selected architecture for the MWF use case, including a refined data flow analysis to optimize system resources; a refined power budget analysis; a delta-V and a fuel budget analysis considering all the possible phases of the mission. This includes from the correction of launcher injection errors and acquisition of nominal satellite position inside the constellation, orbit maintenance to control altitude, collision avoidance to avoid collision with space debris objects and end-of-life (EOL) disposal to comply with EOL guidelines. The relevance of the system architecture selected for the MWF has been evaluated for three use cases of interest (Arctic sea-ice monitoring, maritime fishery pressure and aquaculture, agricultural hydric stress) to show the versatility and the feasibility of the chosen architecture to be adapted for other EO applications.This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 687490.Peer ReviewedPostprint (author's final draft

Architectural optimization framework for earth-observing heterogeneous constellations : marine weather forecast case

Earth observation satellite programs are currently facing, for some applications, the need to deliver hourly revisit times, subkilometric spatial resolutions, and near-real-time data access times. These stringent requirements, combined with the consolidation of small-satellite platforms and novel distributed architecture approaches, are stressing the need to study the design of new, heterogeneous, and heavily networked satellite systems that can potentially replace or complement traditional space assets. In this context, this paper presents partial results from ONION, a research project devoted to studying distributed satellite systems and their architecting characteristics. A design-oriented framework that allows selecting optimal architectures for the given user needs is presented in this paper. The framework has been used in the study of a strategic use-case and its results are hereby presented. From an initial design space of 5586 potential architectures, the framework has been able to preselect 28 candidate designs by an exhaustive analysis of their performance and by quantifying their quality attributes. This very exploration of architectures and the characteristics of the solution space are presented in this paper along with the selected solution and the results of a detailed performance analysis