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  Subjects -> COMPUTER SCIENCE (Total: 2091 journals)
    - ANIMATION AND SIMULATION (31 journals)
    - ARTIFICIAL INTELLIGENCE (101 journals)
    - AUTOMATION AND ROBOTICS (105 journals)
    - CLOUD COMPUTING AND NETWORKS (64 journals)
    - COMPUTER ARCHITECTURE (10 journals)
    - COMPUTER ENGINEERING (11 journals)
    - COMPUTER GAMES (21 journals)
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    - COMPUTER SCIENCE (1215 journals)
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    - DATA BASE MANAGEMENT (14 journals)
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    - ELECTRONIC DATA PROCESSING (22 journals)
    - IMAGE AND VIDEO PROCESSING (40 journals)
    - INFORMATION SYSTEMS (108 journals)
    - INTERNET (94 journals)
    - SOCIAL WEB (52 journals)
    - SOFTWARE (34 journals)
    - THEORY OF COMPUTING (9 journals)

COMPUTER SCIENCE (1215 journals)                  1 2 3 4 5 6 7 | Last

Showing 1 - 200 of 872 Journals sorted alphabetically
3D Printing and Additive Manufacturing     Full-text available via subscription   (Followers: 21)
Abakós     Open Access   (Followers: 4)
ACM Computing Surveys     Hybrid Journal   (Followers: 28)
ACM Journal on Computing and Cultural Heritage     Hybrid Journal   (Followers: 8)
ACM Journal on Emerging Technologies in Computing Systems     Hybrid Journal   (Followers: 15)
ACM Transactions on Accessible Computing (TACCESS)     Hybrid Journal   (Followers: 3)
ACM Transactions on Algorithms (TALG)     Hybrid Journal   (Followers: 15)
ACM Transactions on Applied Perception (TAP)     Hybrid Journal   (Followers: 5)
ACM Transactions on Architecture and Code Optimization (TACO)     Hybrid Journal   (Followers: 9)
ACM Transactions on Autonomous and Adaptive Systems (TAAS)     Hybrid Journal   (Followers: 9)
ACM Transactions on Computation Theory (TOCT)     Hybrid Journal   (Followers: 12)
ACM Transactions on Computational Logic (TOCL)     Hybrid Journal   (Followers: 3)
ACM Transactions on Computer Systems (TOCS)     Hybrid Journal   (Followers: 18)
ACM Transactions on Computer-Human Interaction     Hybrid Journal   (Followers: 15)
ACM Transactions on Computing Education (TOCE)     Hybrid Journal   (Followers: 6)
ACM Transactions on Design Automation of Electronic Systems (TODAES)     Hybrid Journal   (Followers: 6)
ACM Transactions on Economics and Computation     Hybrid Journal   (Followers: 1)
ACM Transactions on Embedded Computing Systems (TECS)     Hybrid Journal   (Followers: 3)
ACM Transactions on Information Systems (TOIS)     Hybrid Journal   (Followers: 19)
ACM Transactions on Intelligent Systems and Technology (TIST)     Hybrid Journal   (Followers: 8)
ACM Transactions on Interactive Intelligent Systems (TiiS)     Hybrid Journal   (Followers: 3)
ACM Transactions on Multimedia Computing, Communications, and Applications (TOMCCAP)     Hybrid Journal   (Followers: 9)
ACM Transactions on Reconfigurable Technology and Systems (TRETS)     Hybrid Journal   (Followers: 6)
ACM Transactions on Sensor Networks (TOSN)     Hybrid Journal   (Followers: 8)
ACM Transactions on Speech and Language Processing (TSLP)     Hybrid Journal   (Followers: 9)
ACM Transactions on Storage     Hybrid Journal  
ACS Applied Materials & Interfaces     Hybrid Journal   (Followers: 32)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 2)
Acta Informatica Malaysia     Open Access  
Acta Universitatis Cibiniensis. Technical Series     Open Access  
Ad Hoc Networks     Hybrid Journal   (Followers: 11)
Adaptive Behavior     Hybrid Journal   (Followers: 11)
Advanced Engineering Materials     Hybrid Journal   (Followers: 28)
Advanced Science Letters     Full-text available via subscription   (Followers: 10)
Advances in Adaptive Data Analysis     Hybrid Journal   (Followers: 7)
Advances in Artificial Intelligence     Open Access   (Followers: 15)
Advances in Calculus of Variations     Hybrid Journal   (Followers: 4)
Advances in Catalysis     Full-text available via subscription   (Followers: 5)
Advances in Computational Mathematics     Hybrid Journal   (Followers: 19)
Advances in Computer Engineering     Open Access   (Followers: 4)
Advances in Computer Science : an International Journal     Open Access   (Followers: 14)
Advances in Computing     Open Access   (Followers: 2)
Advances in Data Analysis and Classification     Hybrid Journal   (Followers: 55)
Advances in Engineering Software     Hybrid Journal   (Followers: 28)
Advances in Geosciences (ADGEO)     Open Access   (Followers: 14)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 22)
Advances in Human-Computer Interaction     Open Access   (Followers: 20)
Advances in Materials Science     Open Access   (Followers: 14)
Advances in Operations Research     Open Access   (Followers: 12)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Remote Sensing     Open Access   (Followers: 49)
Advances in Science and Research (ASR)     Open Access   (Followers: 6)
Advances in Technology Innovation     Open Access   (Followers: 6)
AEU - International Journal of Electronics and Communications     Hybrid Journal   (Followers: 8)
African Journal of Information and Communication     Open Access   (Followers: 9)
African Journal of Mathematics and Computer Science Research     Open Access   (Followers: 4)
AI EDAM     Hybrid Journal  
Air, Soil & Water Research     Open Access   (Followers: 12)
AIS Transactions on Human-Computer Interaction     Open Access   (Followers: 6)
Algebras and Representation Theory     Hybrid Journal   (Followers: 1)
Algorithms     Open Access   (Followers: 11)
American Journal of Computational and Applied Mathematics     Open Access   (Followers: 5)
American Journal of Computational Mathematics     Open Access   (Followers: 4)
American Journal of Information Systems     Open Access   (Followers: 6)
American Journal of Sensor Technology     Open Access   (Followers: 4)
Anais da Academia Brasileira de Ciências     Open Access   (Followers: 2)
Analog Integrated Circuits and Signal Processing     Hybrid Journal   (Followers: 7)
Analysis in Theory and Applications     Hybrid Journal   (Followers: 1)
Animation Practice, Process & Production     Hybrid Journal   (Followers: 5)
Annals of Combinatorics     Hybrid Journal   (Followers: 4)
Annals of Data Science     Hybrid Journal   (Followers: 12)
Annals of Mathematics and Artificial Intelligence     Hybrid Journal   (Followers: 13)
Annals of Pure and Applied Logic     Open Access   (Followers: 3)
Annals of Software Engineering     Hybrid Journal   (Followers: 13)
Annual Reviews in Control     Hybrid Journal   (Followers: 8)
Anuario Americanista Europeo     Open Access  
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 2)
Applied and Computational Harmonic Analysis     Full-text available via subscription   (Followers: 1)
Applied Artificial Intelligence: An International Journal     Hybrid Journal   (Followers: 12)
Applied Categorical Structures     Hybrid Journal   (Followers: 2)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 13)
Applied Computer Systems     Open Access   (Followers: 2)
Applied Informatics     Open Access  
Applied Mathematics and Computation     Hybrid Journal   (Followers: 33)
Applied Medical Informatics     Open Access   (Followers: 10)
Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Soft Computing     Hybrid Journal   (Followers: 16)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 5)
Applied System Innovation     Open Access  
Architectural Theory Review     Hybrid Journal   (Followers: 3)
Archive of Applied Mechanics     Hybrid Journal   (Followers: 5)
Archive of Numerical Software     Open Access  
Archives and Museum Informatics     Hybrid Journal   (Followers: 143)
Archives of Computational Methods in Engineering     Hybrid Journal   (Followers: 5)
arq: Architectural Research Quarterly     Hybrid Journal   (Followers: 8)
Artifact     Hybrid Journal   (Followers: 2)
Artificial Life     Hybrid Journal   (Followers: 7)
Asia Pacific Journal on Computational Engineering     Open Access  
Asia-Pacific Journal of Information Technology and Multimedia     Open Access   (Followers: 1)
Asian Journal of Computer Science and Information Technology     Open Access  
Asian Journal of Control     Hybrid Journal  
Assembly Automation     Hybrid Journal   (Followers: 2)
at - Automatisierungstechnik     Hybrid Journal   (Followers: 1)
Australian Educational Computing     Open Access   (Followers: 1)
Automatic Control and Computer Sciences     Hybrid Journal   (Followers: 5)
Automatic Documentation and Mathematical Linguistics     Hybrid Journal   (Followers: 5)
Automatica     Hybrid Journal   (Followers: 13)
Automation in Construction     Hybrid Journal   (Followers: 6)
Autonomous Mental Development, IEEE Transactions on     Hybrid Journal   (Followers: 9)
Basin Research     Hybrid Journal   (Followers: 5)
Behaviour & Information Technology     Hybrid Journal   (Followers: 52)
Big Data and Cognitive Computing     Open Access   (Followers: 2)
Biodiversity Information Science and Standards     Open Access  
Bioinformatics     Hybrid Journal   (Followers: 305)
Biomedical Engineering     Hybrid Journal   (Followers: 15)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 13)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 21)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 37)
Briefings in Bioinformatics     Hybrid Journal   (Followers: 49)
British Journal of Educational Technology     Hybrid Journal   (Followers: 145)
Broadcasting, IEEE Transactions on     Hybrid Journal   (Followers: 12)
c't Magazin fuer Computertechnik     Full-text available via subscription   (Followers: 1)
CALCOLO     Hybrid Journal  
Calphad     Hybrid Journal   (Followers: 2)
Canadian Journal of Electrical and Computer Engineering     Full-text available via subscription   (Followers: 15)
Capturing Intelligence     Full-text available via subscription  
Catalysis in Industry     Hybrid Journal   (Followers: 1)
CEAS Space Journal     Hybrid Journal   (Followers: 2)
Cell Communication and Signaling     Open Access   (Followers: 2)
Central European Journal of Computer Science     Hybrid Journal   (Followers: 5)
CERN IdeaSquare Journal of Experimental Innovation     Open Access   (Followers: 3)
Chaos, Solitons & Fractals     Hybrid Journal   (Followers: 3)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
ChemSusChem     Hybrid Journal   (Followers: 7)
China Communications     Full-text available via subscription   (Followers: 8)
Chinese Journal of Catalysis     Full-text available via subscription   (Followers: 2)
CIN Computers Informatics Nursing     Hybrid Journal   (Followers: 11)
Circuits and Systems     Open Access   (Followers: 15)
Clean Air Journal     Full-text available via subscription   (Followers: 1)
CLEI Electronic Journal     Open Access  
Clin-Alert     Hybrid Journal   (Followers: 1)
Cluster Computing     Hybrid Journal   (Followers: 2)
Cognitive Computation     Hybrid Journal   (Followers: 4)
COMBINATORICA     Hybrid Journal  
Combinatorics, Probability and Computing     Hybrid Journal   (Followers: 4)
Combustion Theory and Modelling     Hybrid Journal   (Followers: 14)
Communication Methods and Measures     Hybrid Journal   (Followers: 12)
Communication Theory     Hybrid Journal   (Followers: 23)
Communications Engineer     Hybrid Journal   (Followers: 1)
Communications in Algebra     Hybrid Journal   (Followers: 3)
Communications in Computational Physics     Full-text available via subscription   (Followers: 2)
Communications in Information Science and Management Engineering     Open Access   (Followers: 4)
Communications in Partial Differential Equations     Hybrid Journal   (Followers: 3)
Communications of the ACM     Full-text available via subscription   (Followers: 51)
Communications of the Association for Information Systems     Open Access   (Followers: 16)
COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering     Hybrid Journal   (Followers: 3)
Complex & Intelligent Systems     Open Access   (Followers: 1)
Complex Adaptive Systems Modeling     Open Access  
Complex Analysis and Operator Theory     Hybrid Journal   (Followers: 2)
Complexity     Hybrid Journal   (Followers: 6)
Complexus     Full-text available via subscription  
Composite Materials Series     Full-text available via subscription   (Followers: 8)
Computación y Sistemas     Open Access  
Computation     Open Access   (Followers: 1)
Computational and Applied Mathematics     Hybrid Journal   (Followers: 3)
Computational and Mathematical Methods in Medicine     Open Access   (Followers: 2)
Computational and Mathematical Organization Theory     Hybrid Journal   (Followers: 2)
Computational and Structural Biotechnology Journal     Open Access   (Followers: 2)
Computational and Theoretical Chemistry     Hybrid Journal   (Followers: 9)
Computational Astrophysics and Cosmology     Open Access   (Followers: 1)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computational Chemistry     Open Access   (Followers: 2)
Computational Cognitive Science     Open Access   (Followers: 2)
Computational Complexity     Hybrid Journal   (Followers: 4)
Computational Condensed Matter     Open Access  
Computational Ecology and Software     Open Access   (Followers: 9)
Computational Economics     Hybrid Journal   (Followers: 9)
Computational Geosciences     Hybrid Journal   (Followers: 17)
Computational Linguistics     Open Access   (Followers: 23)
Computational Management Science     Hybrid Journal  
Computational Mathematics and Modeling     Hybrid Journal   (Followers: 8)
Computational Mechanics     Hybrid Journal   (Followers: 5)
Computational Methods and Function Theory     Hybrid Journal  
Computational Molecular Bioscience     Open Access   (Followers: 2)
Computational Optimization and Applications     Hybrid Journal   (Followers: 8)
Computational Particle Mechanics     Hybrid Journal   (Followers: 1)
Computational Research     Open Access   (Followers: 1)
Computational Science and Discovery     Full-text available via subscription   (Followers: 2)
Computational Science and Techniques     Open Access  
Computational Statistics     Hybrid Journal   (Followers: 14)
Computational Statistics & Data Analysis     Hybrid Journal   (Followers: 30)
Computer     Full-text available via subscription   (Followers: 98)
Computer Aided Surgery     Open Access   (Followers: 6)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 8)
Computer Communications     Hybrid Journal   (Followers: 16)
Computer Journal     Hybrid Journal   (Followers: 9)
Computer Methods in Applied Mechanics and Engineering     Hybrid Journal   (Followers: 24)
Computer Methods in Biomechanics and Biomedical Engineering     Hybrid Journal   (Followers: 12)
Computer Methods in the Geosciences     Full-text available via subscription   (Followers: 2)

        1 2 3 4 5 6 7 | Last

Journal Cover
CEAS Space Journal
Journal Prestige (SJR): 0.278
Citation Impact (citeScore): 1
Number of Followers: 2  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1868-2510 - ISSN (Online) 1868-2502
Published by Springer-Verlag Homepage  [2351 journals]
  • Multiple beacons for supporting lunar landing navigation
    • Authors: Stephan Theil; Leonardo Bora
      Pages: 295 - 305
      Abstract: The exploration and potential future exploitation of solar system bodies requires technologies for precise and safe landings. Current navigation systems for landing probes are relying on a combination of inertial and optical sensor measurements to determine the current flight state with respect to the target body and the desired landing site. With a future transition from single exploration missions to more frequent first exploration and then exploitation missions, the implementation and operation of these missions changes, since it can be expected that a ground infrastructure on the target body is available in the vicinity of the landing site. In a previous paper, the impact of a single ground-based beacon on the navigation performance was investigated depending on the type of radiometric measurements and on the location of the beacon with respect to the landing site. This paper extends this investigation on options for ground-based multiple beacons supporting the on-board navigation system. It analyzes the impact on the achievable navigation accuracy. For that purpose, the paper introduces briefly the existing navigation architecture based on optical navigation and its extension with radiometric measurements. The same scenario of lunar landing as in the previous paper is simulated. The results are analyzed and discussed. They show a single beacon at a large distance along the landing trajectory and multiple beacons close to the landing site can improve the navigation performance. The results show how large the landing area can be increased where a sufficient navigation performance is achieved using the beacons.
      PubDate: 2018-09-01
      DOI: 10.1007/s12567-018-0199-3
      Issue No: Vol. 10, No. 3 (2018)
       
  • Project-based learning applied to spacecraft power systems: a long-term
           engineering and educational program at UPM University
    • Authors: Santiago Pindado; Javier Cubas; Elena Roibás-Millán; Félix Sorribes-Palmer
      Pages: 307 - 323
      Abstract: The IDR/UPM Institute is the research center responsible for the Master in Space Systems (MUSE) of Universidad Politécnica de Madrid (UPM). This is a 2-year (120 ECTS) master’s degree focused on space technology. The UPMSat-2 satellite program has become an excellent educational framework in which the academic contents of the master are trained through project-based learning and following a multidisciplinary approach. In the present work, the educational projects developed and carried out in relation to spacecraft power systems at the IDR/UPM Institute are described. These projects are currently being developed in the framework represented by the aforementioned MUSE master’s program and UPMSat-2.
      PubDate: 2018-09-01
      DOI: 10.1007/s12567-018-0200-1
      Issue No: Vol. 10, No. 3 (2018)
       
  • ATON (Autonomous Terrain-based Optical Navigation) for exploration
           missions: recent flight test results
    • Authors: S. Theil; N. Ammann; F. Andert; T. Franz; H. Krüger; H. Lehner; M. Lingenauber; D. Lüdtke; B. Maass; C. Paproth; J. Wohlfeil
      Pages: 325 - 341
      Abstract: Since 2010 the German Aerospace Center is working on the project Autonomous Terrain-based Optical Navigation (ATON). Its objective is the development of technologies which allow autonomous navigation of spacecraft in orbit around and during landing on celestial bodies like the Moon, planets, asteroids and comets. The project developed different image processing techniques and optical navigation methods as well as sensor data fusion. The setup—which is applicable to many exploration missions—consists of an inertial measurement unit, a laser altimeter, a star tracker and one or multiple navigation cameras. In the past years, several milestones have been achieved. It started with the setup of a simulation environment including the detailed simulation of camera images. This was continued by hardware-in-the-loop tests in the Testbed for Robotic Optical Navigation (TRON) where images were generated by real cameras in a simulated downscaled lunar landing scene. Data were recorded in helicopter flight tests and post-processed in real-time to increase maturity of the algorithms and to optimize the software. Recently, two more milestones have been achieved. In late 2016, the whole navigation system setup was flying on an unmanned helicopter while processing all sensor information onboard in real time. For the latest milestone the navigation system was tested in closed-loop on the unmanned helicopter. For that purpose the ATON navigation system provided the navigation state for the guidance and control of the unmanned helicopter replacing the GPS-based standard navigation system. The paper will give an introduction to the ATON project and its concept. The methods and algorithms of ATON are briefly described. The flight test results of the latest two milestones are presented and discussed.
      PubDate: 2018-09-01
      DOI: 10.1007/s12567-018-0201-0
      Issue No: Vol. 10, No. 3 (2018)
       
  • Measurement of fracture toughness of metallic materials produced by
           additive manufacturing
    • Authors: O. Quénard; O. Dorival; Ph. Guy; A. Votié; K. Brethome
      Pages: 343 - 353
      Abstract: This study focuses on the microstructure and mechanical properties of metallic materials produced by additive layer manufacturing (ALM), especially the laser beam melting process. The influence of the specimen orientation during the ALM process and that of two post-build thermal treatments were investigated. The identified metal powder is Ti-6Al-4V (titanium base). Metallographic analysis shows their effects on the microstructure of the metals. Mechanical experiments involving tensile tests as well as toughness tests were performed according to ASTM (American Society for Testing and Materials) norms. The results show that the main influence is that of the thermal treatments; however the manufacturing stacking direction may lead to some anisotropy in the mechanical properties.
      PubDate: 2018-09-01
      DOI: 10.1007/s12567-018-0202-z
      Issue No: Vol. 10, No. 3 (2018)
       
  • Orbital Hub: a concept for human spaceflight beyond ISS operations
    • Authors: Stephan S. Jahnke; Volker Maiwald; Claudia Philpot; Dominik Quantius; Oliver Romberg; Wolfgang Seboldt; Vincent Vrakking; Conrad Zeidler
      Pages: 355 - 379
      Abstract: The International Space Station (ISS) is the greatest endeavour in low-Earth orbit since the beginning of the space age and the culmination of human outposts like Skylab and Mir. While a clear schedule has yet to be drafted, it is expected that ISS will cease operation in the 2020s. What could be the layout for a human outpost in LEO with lessons learnt from ISS' What are the use cases and applications of such an outpost in the future' The System Analysis Space Segment group of the German Aerospace Center investigated these and other questions and developed the Orbital Hub concept. In this paper an overview is presented of how the overall concept has been derived and its properties and layouts are described. Starting with a workshop involving the science community, the scientific requirements have been derived and Strawman payloads have been defined for use in further design activities. These design activities focused on Concurrent Engineering studies, where besides DLR employees participants from the industry and astronauts were involved. The result is an expandable concept that is composed of two main parts, the Base Platform, home for a permanent crew of up to three astronauts, and the Free Flyer, an uncrewed autonomous research platform. This modular approach provides one major advantage: the decoupling of the habitat and payload leading to increased quality of the micro-gravity environment. The former provides an environment for human physiology experiments, while the latter allows science without the perturbations caused by a crew, e.g. material experiments or Earth observation. The Free Flyer is designed to operate for up to 3 months on its own, but can dock with the space station for maintenance and experiment servicing. It also has a hybrid propulsion system, chemical and electrical, for different applications. The hub’s design allows launch with just three launches, as the total mass of all the hub parts is about 60,000 kg. The main focus of the design is on autonomy and reducing crew maintenance and repair efforts, and reducing the need for extravehicular activities. Following a description of the design approach and technical details, cost estimation and a detailed discussion of the use cases for such a station concept, along with the possible scenarios of international cooperation, are also presented in this paper.
      PubDate: 2018-09-01
      DOI: 10.1007/s12567-018-0203-y
      Issue No: Vol. 10, No. 3 (2018)
       
  • OMA analysis of a launcher under operational conditions with time-varying
           properties
    • Authors: M. Eugeni; G. Coppotelli; F. Mastroddi; P. Gaudenzi; S. Muller; B. Troclet
      Pages: 381 - 406
      Abstract: The objective of this paper is the investigation of the capability of operational modal analysis approaches to deal with time-varying system in the low-frequency domain. Specifically, the problem of the identification of the dynamic properties of a launch vehicle, working under actual operative conditions, is studied. Two OMA methods are considered: the frequency-domain decomposition and the Hilbert transform method. It is demonstrated that both OMA approaches allow the time-tracking of modal parameters, namely, natural frequencies, damping ratios, and mode shapes, from the response accelerations only recorded during actual flight tests of a launcher characterized by a large mass variation due to fuel burning typical of the first phase of the flight.
      PubDate: 2018-09-01
      DOI: 10.1007/s12567-018-0209-5
      Issue No: Vol. 10, No. 3 (2018)
       
  • Performance analysis of an IMU-augmented GNSS tracking system on board the
           MAIUS-1 sounding rocket
    • Authors: Benjamin Braun; Andreas Grillenberger; Markus Markgraf
      Pages: 407 - 425
      Abstract: Satellite navigation receivers are adequate tracking sensors for range safety of both orbital launch vehicles and suborbital sounding rockets. Due to high accuracy and its low system complexity, satellite navigation is seen as well-suited supplement or replacement of conventional tracking systems like radar. Having the well-known shortcomings of satellite navigation like deliberate or unintentional interferences in mind, it is proposed to augment the satellite navigation receiver by an inertial measurement unit (IMU) to enhance continuity and availability of localization. The augmented receiver is thus enabled to output at least an inertial position solution in case of signal outages. In a previous study, it was shown by means of simulation using the example of Ariane 5 that the performance of a low-grade microelectromechanical IMU is sufficient to bridge expected outages of some ten seconds, and still meeting the range safety requirements in effect. In this publication, these theoretical findings shall be substantiated by real flight data that were recorded on MAIUS-1, a sounding rocket launched from Esrange, Sweden, in early 2017. The analysis reveals that the chosen representative of a microelectromechanical IMU is suitable to bridge outages of up to thirty seconds.
      PubDate: 2018-09-01
      DOI: 10.1007/s12567-018-0206-8
      Issue No: Vol. 10, No. 3 (2018)
       
  • On the accuracy of the SGP4 to predict stellar occultation events using
           ENVISAT/GOMOS data and recommendations for the ALTIUS mission
    • Authors: Jan Thoemel; Nina Mateshvili; Philippe Demoulin; Filip Vanhellemont; Didier Pieroux; Christine Bingen; Emmanuel Dekemper; Ghislain Franssens; Charles Robert; Didier Fussen
      Abstract: In preparation for the operations of the ALTIUS mission, research is carried out to assess the accuracy of the SGP4 orbital propagator in predicting stellar occultation events. The quantification of the accuracy and its consequent improvement will enable reliable measurement planning and, therefore, maximize the number of measurements. To this end, predictions are made for the timing of occultations for the GOMOS instrument on-board the ENVISAT, which are then compared to actual occultation occurrences. It is found that the error is substantial but follows a trend that can be interpolated. This enables devising a method for highly accurate predictions given a sufficient number of data points. Statistically significant results for the accuracy of the propagator and a calibration method are presented. Recommendations for a measurement planning procedure of ALTIUS are formulated.
      PubDate: 2018-10-10
      DOI: 10.1007/s12567-018-0221-9
       
  • Dynamic guidance of orbiter gliders: alignment, final approach, and
           landing
    • Authors: João Fonseca; Rui Dilão
      Abstract: A new algorithm capable of guiding an orbiter glider to a target point with a prescribed alignment and descent path angle is presented. This algorithm can initiate Terminal Area Energy Management (TAEM) before reaching steady state and perform the Final Approach and Landing (FA&L). During TAEM, runway alignment is done through a moving virtual target derived from steady state, while during FA&L, a transient (or flare) is used to reach the extremely shallow descent path angles. All decisions are made dynamically relying solely on local information (position, speed, attitude, and atmospheric parameters), and all structural limits of the glider are respected at all times. As a proof of concept, a Space Shuttle return flight is simulated. For a large multitude of initial conditions and targets, the algorithm is able to consistently deliver distance errors below 19 m (transverse errors below 4 m), alignment errors below \(1^{\circ }\) , descent path angles at the intended \(-\,2^{\circ }\) , and vertical descent speeds below 8.5 m/s with control time intervals of 0.1 s.
      PubDate: 2018-10-03
      DOI: 10.1007/s12567-018-0219-3
       
  • FAINTSTAR: an intelligent single-chip sensor head for star
           trackers—prototype results
    • Authors: W. Ogiers; K. Ruythooren; K. Van Wichelen; M. Dendoncker; S. Kowaltschek; B. Razgus
      Abstract: Since 2003 the European Space Agency’s roadmap for star tracker CMOS APS (active pixel) image sensors has included developments to integrate significant logic functionality with the pixel array, aiming at an imaging system-on-chip. FaintStar (FS) will be the first commercially available product resulting from these activities. FaintStar is being developed by ams Sensors Belgium (formerly CMOSIS) in two phases. Phase 1 served to specify, design, manufacture, and characterise a prototype chip, informally named FaintStar1 (FS1), the subject of this paper. FaintStar is a one megapixel image sensor with 10 µm pixels and rolling shutter. All interactions with the user are over a single 80 Mb/s SpaceWire link. FaintStar offers various readout modes (full frame, windowed, windowed with dual rolling shutter, etc.). The chip has ‘pixels-to-centroids’ processing, including transfer curve linearisation, bad pixel replacement, background image estimation and suppression, spike filtering, bright object extraction, and photometric barycentre calculation. The algorithms used are generic, i.e., non-reliant on third-party IP, yet highly user-configurable. Data-compressed or raw image output is also supported. The device has been developed for star trackers mainly, although applications such as high-accuracy sun sensing, and navigation, rendezvous, or rover cameras are also served. The prototype chip exceeds its expectations. This article starts with an overview of the FS1 design and reports on the Phase 1 characterisation results, including electro-optical performance, proton displacement damage, total dose, and single event radiation effects. Started end of 2017, the project’s Phase 2 entails minor design refinements, creating FaintStar2 (FS2), its manufacturing, and then a formal evaluation campaign. After this, the sensor will be offered as a commercial off-the-shelf product.
      PubDate: 2018-09-28
      DOI: 10.1007/s12567-018-0220-x
       
  • Finite element modelling and performance optimization of an ion thruster
           depending on the nature of the propellant
    • Authors: Ionuț-Florian Popa; Anna-Maria Theodora Andreescu; Dan Ifrim; Radu Mihalache; Dragoș Mihai; Grigore Cican
      Abstract: The electrostatic propulsion is a class of space propulsion which makes use of electrical power and this kind of systems are characterized by high exhaust velocities and specific impulse, enhancing the propulsive performances of thrusters compared to conventional chemical thrusters. Since the ionized particle exhaust velocity is a function of the ratio between the electrical charge and their molecular mass, the obvious solution is to use ions with low electrical charge–molecular mass ratio. Currently, the most used propellant for the space propulsion is the Xenon gas, as it has a series of important advantages, but is quite expensive when compared to other propellants. This paper aims to make an optimization of the ideal ion propulsion systems depending on the nature of the propellant, like common used substances in the space propulsion, but also other substances which are potential candidates for this application. A variety of ion thruster performances will be analyzed, such as force, specific impulse, efficiency for the same power available onboard, the same accelerating voltage, and the same ion current. Also, for the Xenon case a numerical simulation was performed to highlight the behavior and trajectory of the ionized particles and their velocity. The conclusion obtained following the study is that a reasonable ion thruster regarding the dimensions should use an accelerating potential of at least 4000 V and 2 A of ion current.
      PubDate: 2018-08-13
      DOI: 10.1007/s12567-018-0218-4
       
  • A GMSK VHF-uplink/UHF-downlink transceiver for the CubeSat missions
    • Authors: Yaseen Zaidi; Robert Ryk van Zyl; Norman G. Fitz-Coy
      Abstract: Functional and thermal performance characteristics of a very high frequency/ultra high frequency (VHF/UHF) transceiver based on Gaussian minimum shift keying (GMSK) modulation are presented. The transceiver has been designed for CubeSats telemetry and commanding needs or low rate data download. The design is validated at 27 dBm, 30 dBm and 33 dBm transmitting powers over −20 \(^\circ \hbox {C}\) to +51 \(^\circ \hbox {C}\) . Under these thermal conditions, the transmitter spurious dynamic response shows little if any change and the average sensitivity of receiver at the 12 dB signal noise and distortion (SINAD) is −116.7 dBm at 140 MHz and −116.78 dBm at 149.98 MHz. The transmitter and receiver frequencies are stable and the current consumption as well the output RF levels are steady. The design has been verified against a simulation model which allows system tradeoff analysis. The measurements demonstrate the transceiver made with commercial grade parts has dependable performance at the low earth altitudes and orbital heating conditions.
      PubDate: 2018-08-02
      DOI: 10.1007/s12567-018-0217-5
       
  • Computational modeling of nonlinear propellant sloshing for spacecraft
           AOCS applications
    • Authors: Manuel Hahn; Stefan Adami; Roger Förstner
      Abstract: During all operational phases, propellant sloshing may have a significant influence on spacecraft performance and stability. The proper description of propellant sloshing effects is then essential for the verification of the Attitude and Orbit Control System (AOCS). As soon as nonlinear effects predominate (e.g. for high-agility or in a micro-gravity environment), classical approaches as mechanical analog models (e.g. pendulums) fail and computational models need to be utilized to describe the propellant dynamics. These computational models currently lack the ability to accurately describe nonlinear effects like high-velocity impacts, as well as cohesion and adhesion forces in a micro-gravity environment. Additionally these models are computationally very expensive, so that they are commonly not directly used in AOCS verification campaigns, where a large number of simulations are performed. The scope of this work is the development of a computational model based on smoothed particle hydrodynamics, which is able to accurately describe nonlinear propellant sloshing effects in gravity-dominated regimes, which is of relevance for example for high-agility spacecraft missions. The newly developed code is validated using analytical expressions, experimental data as well as other numerical codes. Subsequently, a study is performed showing that the global variables like forces acting on the tank wall or the center of mass are still approximated reasonably well when using lower spatial resolutions, resulting in much faster simulation runs and making it feasible to use the computational model directly in AOCS verification campaigns. Finally, the coupling of the propellant sloshing code to an AOCS and Flight Dynamics rigid-body simulator is demonstrated by simulating a nonlinear forced-roll motion of a partially-filled tank under Earth-gravity.
      PubDate: 2018-08-01
      DOI: 10.1007/s12567-018-0216-6
       
  • Lunar landing navigation supported by ranging to an orbiter
    • Authors: Ennio Condoleo; Stephan Theil
      Abstract: Precise and safe landings on celestial bodies as the Moon are needed for the further exploration and potential future exploitation of solar system bodies. The current navigation systems for landing probes are based on sensor data fusion of inertial and optical sensor measurements to determine the current flight state with respect to the target body and the desired landing site. To improve the accuracy of lunar landing navigation, radiometric measurements (range and range-rate) with respect to an orbiting vehicle have been proposed in several studies. This paper analyzes the impact of range and range-rate measurements from an orbiting vehicle on the navigation accuracy. For that purpose, a baseline configuration of an optical navigation system is used which has already been taken as a reference for investigating the effect of ground-based beacons. First, the influence of the orbiter trajectory in relation to the landing trajectory is investigated. In particular, the line of sight between orbiter and lander permits a preliminary assessment of the navigation performance. Later, the effects of sensor noise for all measurements and of the orbiter ephemeris error are also evaluated. Finally, for a selected scenario, it is demonstrated that radiometric measurements with respect to an orbiter can reduce the positioning error by about 40%.
      PubDate: 2018-07-27
      DOI: 10.1007/s12567-018-0215-7
       
  • VHF Data Exchange System (VDES): an enabling technology for maritime
           communications
    • Authors: Francisco Lázaro; Ronald Raulefs; Wei Wang; Federico Clazzer; Simon Plass
      Abstract: This work presents an overview of the radio interface of VHF Data Exchange System (VDES), which is currently on its way to become an ITU standard supported by International Association of Marine Aids to Navigation and Lighthouse Authorities. VDES includes the already existing collision avoidance tracking system Automatic Identification System and the messaging system Application Specific Messages. Additionally, a new third component for digital maritime communications of any kind, named VHF Data Exchange is included. On the one hand, there is a traditional terrestrial component, on the other hand, a satellite communication link is also envisioned partly by the same spectrum usage. In this article, focus is given towards the technical design aspects and challenges of this hybrid communications transmission scheme.
      PubDate: 2018-07-20
      DOI: 10.1007/s12567-018-0214-8
       
  • Evaluating the stability of NASA’s space launch system with adaptive
           augmenting control
    • Authors: Tannen S. VanZwieten; Michael R. Hannan; John H. Wall
      Abstract: NASA’s baseline space launch system (SLS) flight control system (FCS) design includes an adaptive augmenting control (AAC) component that modifies the attitude control system response by augmenting the classical gain-scheduled architecture with additional performance and robustness. The NASA Engineering and Safety Center (NESC) teamed with the SLS Program to perform a comprehensive assessment of the stability and robustness of this FCS with emphasis on the AAC component. Multiple analysis techniques applicable to nonlinear systems were commissioned as part of this assessment, which was conducted in parallel with the program’s standard design analysis cycle. The following analyses were included, with each technique adding unique valuable insights: Lyapunov-based stability analysis, classical stability analysis with static AAC gain variations, circle criterion-based analysis of the FCS with a time-varying gain element, time-domain stability margin assessment, Monte Carlo simulations with expanded dispersions, and an extensive set of stressing cases. Several of the completed analyses focused on determining whether the inclusion of AAC introduced risk to the FCS, while others quantified the benefits of the adaptive augmentation.
      PubDate: 2018-06-28
      DOI: 10.1007/s12567-018-0211-y
       
  • AOCS design for the ATHENA X-ray telescope: challenges and solutions
    • Authors: T. Ott; S. Goerries; A. Schleicher; S. Winkler
      Abstract: The ATHENA—Advanced Telescope for High-ENergy Astrophysics—mission is currently assessed in a phase A feasibility study as L-class mission in ESA’s Cosmic Vision 2015–2025 plan, with launch foreseen in 2028. Primary mission goal is the mapping of hot gas structures and the determination of their physical properties to search for supermassive black holes. ATHENA is an X-ray telescope with a focal length of 12 m. It has a mass of ~ 7000 kg and it is ~ 15 m high with a diameter of ~ 3 m. The main mass is distributed to the mirror on the one side of the spacecraft and to the science instrument module on the other side of the spacecraft. To achieve its science goals, ATHENA performs a sky survey with precision line-of-sight pointing requirements in the order of arc seconds for absolute pointing and sub-arc seconds for relative pointing in time windows > 1 ks, all at 95% confidence level. That is very demanding for large X-ray telescopes. In addition to the precision pointing requirements, ATHENA cannot violate a certain sun exclusion zone. This is a hard constraint to prevent any stray-light falling onto the instruments, as it would immediately destroy them. The sky survey is defined by an observation plan that is demanding in terms of availability and thus spacecraft agility. The pointing and agility requirements and the fact that ATHENA is a spacecraft with high mass and volume introduce several design challenges for the attitude and orbit control system. This paper presents those challenges, corresponding solutions, and preliminary results, which have been achieved during the phase A study led by Airbus in Friedrichshafen, Germany. The main focus and contribution of this paper are the identification of research and development needs for attitude and orbit control systems to enable the ATHENA mission. In this respect, the ATHENA design challenges are discussed and addressed with the state-of-the-art design methods. This paper concludes with the main identified technology development needs and formulates specific research questions related to practical design problems. In particular, the following attitude and orbit control system design challenges are addressed: autonomous and agile large angle slew manoeuvres with exclusion zones, availability for science observations, precision line-of-sight determination as well as analysis during the design process using the ESA Pointing Error Engineering Tool and pointing control with a hexapod as line-of-sight actuator in the control loop. The last challenge, namely, the hexapod in the control loop, is without precedence in Europe and to the best knowledge of the authors in the world.
      PubDate: 2018-06-28
      DOI: 10.1007/s12567-018-0213-9
       
  • Beyond L ∞ reaction wheel commanding: increased on-board autonomy
           through enhanced wheel failure handling
    • Authors: Stefan Winkler; Maik Evers; Benjamin Kraft
      Abstract: Latest large spacecraft and/or agility requirements have led to configurations of five or more reaction wheels. To avoid (1) handling a significant amount of pre-stored parameters on board and (2) intervening by ground (classical approach) to recover single- and multiple-wheel failures, the orthogonal null space basis must be robustly computed on board. Two deterministic methods are presented in this paper: (1) via virtual torque commands using L∞ and L2 commanding, (2) via generalized inverse. Furthermore, a cascading null space control approach that autonomously respects predefined wheel momentum operating bands is introduced. The presented work is dedicated to the demand of high on-board autonomy driven by more and more customers requiring just a working spacecraft with minimum interventions by ground. The presented solutions are already part of the Airbus high-power satellite avionics system Astrobus AS400 for current and future missions such as MetOp-SG. Furthermore, the presented functionalities are essential towards on-board real-time spacecraft reconfiguration which is; however, beyond the scope of this paper.
      PubDate: 2018-06-18
      DOI: 10.1007/s12567-018-0212-x
       
  • Sentinel-1 near real-time application for maritime situational awareness
    • Authors: Detmar Krause; Egbert Schwarz; Sergey Voinov; Heiko Damerow; Daniel Tomecki
      Abstract: In the context of the project real-time services for maritime security (Echtzeitdienste für die Maritime Sicherheit—security), an experimental research platform for validation of maritime products derived from remote sensing data, was developed. This article describes the work carried out to derive ship-, wind-, and wave detection products out of Sentinel-1 remote-sensing data by DLR’s Maritime Safety and Security Lab in Neustrelitz, part of the German Remote Data Center DFD. The activity aims to the fulfilment of project requirements, primarily to support the need for near real-time performance up to 15 min, as those in maritime situational awareness. The development and implementation cover the task of level 0 processing, based on DLR’s front end processor, the implementation of the framework for real-time processing up to level 2 (value adding), as well as the development of a hardware-independent virtual-processing platform.
      PubDate: 2018-06-13
      DOI: 10.1007/s12567-018-0210-z
       
  • Thank you to our CEAS Space Journal Reviewers
    • PubDate: 2018-03-08
      DOI: 10.1007/s12567-018-0198-4
       
 
 
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