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COMPUTER SCIENCE (1228 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: 24)
Abakós     Open Access   (Followers: 4)
ACM Computing Surveys     Hybrid Journal   (Followers: 30)
ACM Journal on Computing and Cultural Heritage     Hybrid Journal   (Followers: 8)
ACM Journal on Emerging Technologies in Computing Systems     Hybrid Journal   (Followers: 17)
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: 16)
ACM Transactions on Computing Education (TOCE)     Hybrid Journal   (Followers: 7)
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: 20)
ACM Transactions on Intelligent Systems and Technology (TIST)     Hybrid Journal   (Followers: 8)
ACM Transactions on Interactive Intelligent Systems (TiiS)     Hybrid Journal   (Followers: 4)
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: 33)
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: 10)
Advanced Engineering Materials     Hybrid Journal   (Followers: 28)
Advanced Science Letters     Full-text available via subscription   (Followers: 11)
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: 5)
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: 59)
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: 23)
Advances in Human-Computer Interaction     Open Access   (Followers: 21)
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: 50)
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   (Followers: 1)
Air, Soil & Water Research     Open Access   (Followers: 14)
AIS Transactions on Human-Computer Interaction     Open Access   (Followers: 7)
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: 12)
Annals of Pure and Applied Logic     Open Access   (Followers: 3)
Annals of Software Engineering     Hybrid Journal   (Followers: 13)
Annals of West University of Timisoara - Mathematics and Computer Science     Open Access  
Annual Reviews in Control     Hybrid Journal   (Followers: 8)
Anuario Americanista Europeo     Open Access  
Applicable Algebra in Engineering, Communication and Computing     Hybrid Journal   (Followers: 3)
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: 3)
Applied Clinical Informatics     Hybrid Journal   (Followers: 2)
Applied Computational Intelligence and Soft Computing     Open Access   (Followers: 14)
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: 11)
Applied Numerical Mathematics     Hybrid Journal   (Followers: 5)
Applied Soft Computing     Hybrid Journal   (Followers: 17)
Applied Spatial Analysis and Policy     Hybrid Journal   (Followers: 6)
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: 151)
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 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: 6)
Automatic Documentation and Mathematical Linguistics     Hybrid Journal   (Followers: 5)
Automatica     Hybrid Journal   (Followers: 12)
Automation in Construction     Hybrid Journal   (Followers: 7)
Autonomous Mental Development, IEEE Transactions on     Hybrid Journal   (Followers: 8)
Balkan Journal of Electrical and Computer Engineering     Open Access  
Basin Research     Hybrid Journal   (Followers: 5)
Behaviour & Information Technology     Hybrid Journal   (Followers: 51)
Big Data and Cognitive Computing     Open Access   (Followers: 3)
Biodiversity Information Science and Standards     Open Access  
Bioinformatics     Hybrid Journal   (Followers: 317)
Biomedical Engineering     Hybrid Journal   (Followers: 16)
Biomedical Engineering and Computational Biology     Open Access   (Followers: 13)
Biomedical Engineering, IEEE Reviews in     Full-text available via subscription   (Followers: 20)
Biomedical Engineering, IEEE Transactions on     Hybrid Journal   (Followers: 35)
Briefings in Bioinformatics     Hybrid Journal   (Followers: 50)
British Journal of Educational Technology     Hybrid Journal   (Followers: 152)
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)
Clinical eHealth     Open Access  
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: 15)
Communication Methods and Measures     Hybrid Journal   (Followers: 13)
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: 4)
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 Biophysics     Open Access   (Followers: 1)
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: 1)
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   (Followers: 1)
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: 24)
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: 9)
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: 33)
Computer     Full-text available via subscription   (Followers: 104)
Computer Aided Surgery     Open Access   (Followers: 6)
Computer Applications in Engineering Education     Hybrid Journal   (Followers: 8)
Computer Communications     Hybrid Journal   (Followers: 16)

        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  [2352 journals]
  • Interference and multipath suppression with space-time adaptive
           beamforming for safety-of-life maritime applications
    • Authors: Manuel Appel; Andreas Iliopoulos; Friederike Fohlmeister; Emilio Pérez Marcos; Manuel Cuntz; Andriy Konovaltsev; Felix Antreich; Michael Meurer
      Abstract: In this work, we present mitigation algorithms to protect GNSS receivers against malicious interference. Maritime applications with an antenna array-based receiver are considered as a use case. A two-stage mitigation algorithm, that tackles multipath and radio frequency interference (RFI), caused by personal privacy devices (PPD) or additive white Gaussian noise (AWGN) interferers is presented. Our approach consists of a pre-whitening step, followed by a space-time adaptive principle component analysis (PCA) beamformer that uses a dimensionality reduction (i.e. compression) method based on Canonical Components (CC) with a bank of signal-matched correlators. The algorithms are capable of suppressing strong RFI and separating highly correlated and even coherent multipath signals, thus achieving a reliable time delay and, therefore, pseudorange estimation performance. Finally, we evaluate and compare the proposed algorithms not only via numerical simulations but also with real data collected from a measurement campaign performed at DLR’s maritime jamming testbed in the Baltic sea. A complete description of the test platform and the scenarios is provided.
      PubDate: 2019-01-19
      DOI: 10.1007/s12567-019-0236-x
  • Robustness of Astrix Fiber Optic Gyros in space radiative environment
    • Authors: A. Paveau; G. Cros; S. Masson; R. Mangeret; S. Marioujouls; J.-J. Bonnefois
      Abstract: When developing the Fiber Optics Gyro Astrix™ family, Airbus and Ixblue faced the problematics of the possible radiation effects on optical and opto-electronics parts. After bibliographic research on the subject, selection of parts was made according to existing knowledge, and batch qualification tests performed to quantify the radiation effects. On-ground test results were introduced in worst case optical budget for the optical loop dimensioning. Several years later, following consequent in-orbit data gathering, we can assess that radiation effect are barely noticeable and that inertial performances remain tremendously stable. The careful design of the Astrix optical loop and the proper selection of opto parts were mastered key factor for such an in-flight success.
      PubDate: 2019-01-14
      DOI: 10.1007/s12567-018-0231-7
  • Automatic bathymetry retrieval from SAR images
    • Authors: Stefan Wiehle; Andrey Pleskachevsky; Claus Gebhardt
      Abstract: Bathymetry, the topography of the sea floor, is in high demand due to the increase in offshore constructions like wind parks. It is also an important dataset for climate change modelling, when sea level rises and changes in circulation currents are to be simulated. The retrieval of accurate bathymetry data is a cost-intensive task usually requiring a survey vessel charting the respective area. However, bathymetry can also be retrieved remotely using data from Earth observation satellites. The main point of this study is the development of a processor that allows the automatic derivation of gridded bathymetry information from spaceborne Synthetic Aperture Radar (SAR) data. Observations of sea state modifications in SAR images are used to derive the bathymetry in shelf areas using the shoaling effect, which causes wavelengths to become shorter when reaching shallower waters. The water depth is derived using the dispersion relation for surface water waves, which requires wavelength and wave period as input parameters. While the wavelength can be directly retrieved from the SAR image, for the peak period additional information and procedures are required, e.g. local measurements or complex SAR data. A method for automatically deriving the wave period for swell waves in SAR images was developed and tested in this paper. It uses depth data from public databases as initial values which are compared to derived depths iterating through possible peak periods along the calculation grid; the peak period resulting in a minimal root-mean-square deviation is then used for bathymetry calculation. The bathymetry derived from a TerraSAR-X acquisition of the Channel Islands is presented; the resulting peak wave period of 11.3 s fits well to nearby in situ measurement data.
      PubDate: 2019-01-09
      DOI: 10.1007/s12567-018-0234-4
  • In Memoriam: Dr. Julián Santiago-Prowald, Senior Advisor for the
           Structures, Mechanisms and Materials Division of ESA (1969–2018)
    • Authors: Santiago Pindado
      PubDate: 2019-01-02
      DOI: 10.1007/s12567-018-0233-5
  • ACLAD: a new philosophy for launcher coupled load analyses
    • Authors: Marco Trucchi
      Abstract: The new ACLAD philosophy for launcher/spacecraft mechanical-coupled load analysis (CLA) is presented. ACLAD stands for “A CLA a Day”. We encourage the development of a work method that would allow spacecraft manufacturers to perform a very high number of CLA, instead of once or twice per each program as done today. Such analyses provide the best possible estimation of the spacecraft loads during flight and often underline that the mechanical requirements are much higher than the actual need. If performed many times during a project, CLA could help prevent overdesign and overtesting by inducing lower specifications. Lower costs and mass of the structures could be attained. Some possible implementations of ACLAD are presented in this paper.
      PubDate: 2019-01-02
      DOI: 10.1007/s12567-018-0229-1
  • Integration of thermo-elastic characteristics in finite element method
           reduced models
    • Authors: Marco Trucchi; Vincent Torrelli
      Abstract: A simple method for integrating thermo-elastic characteristics in finite element method (FEM) reduced models is presented. Methods like Guyan or Craig-Bampton reductions are widely used in the space industry, as they drastically decrease the size of models and also allow safe model exchanges between companies without disclosing sensitive technologies. On the other hand, reduced models cannot be implemented in thermo-elastic analyses, which are of paramount importance for spacecrafts mainly for on-orbit sizing and pointing analyses. The new presented method is simple to implement and consists of replacing the dropped thermo-elastic characteristics of the reduced models by a set of interface forces and moments. These are computed by clamping the physical FEM model at its interfaces and applying unit thermal loads on the different internal zones. An analytical and a numerical example are presented. The implementation in FEM shows high accuracy.
      PubDate: 2019-01-02
      DOI: 10.1007/s12567-018-0230-8
  • Editorial: International ESA Conference on Guidance, Navigation and
           Control Systems 2017
    • Authors: S. Bennani; A. Benoit; G. Ortega; S. Theil
      Pages: 469 - 470
      PubDate: 2018-12-01
      DOI: 10.1007/s12567-018-0227-3
      Issue No: Vol. 10, No. 4 (2018)
  • In-orbit performance of the LISA Pathfinder drag-free and attitude control
    • Authors: A. Schleicher; T. Ziegler; R. Schubert; N. Brandt; P. Bergner; U. Johann; W. Fichter; J. Grzymisch
      Pages: 471 - 485
      Abstract: LISA Pathfinder is a technology demonstrator mission that was funded by the European Space Agency and that was launched on December 3, 2015. LISA Pathfinder has been conducting experiments to demonstrate key technologies for the gravitational wave observatory LISA in its operational orbit at the L1 Lagrange point of the Earth–Sun system until final switch off on July 18, 2017. These key technologies include the inertial sensors, the optical metrology system, a set of µ-propulsion cold gas thrusters and in particular the high performance drag-free and attitude control system (DFACS) that controls the spacecraft in 15 degrees of freedom during its science phase. The main goal of the DFACS is to shield the two test masses inside the inertial sensors from all external disturbances to achieve a residual differential acceleration between the two test masses of less than 3 × 10−14 m/s2/√Hz over the frequency bandwidth of 1–30 mHz. This paper focuses on two important aspects of the DFACS that has been in use on LISA Pathfinder: the DFACS Accelerometer mode and the main DFACS Science mode. The Accelerometer mode is used to capture the test masses after release into free flight from the mechanical grabbing mechanism. The main DFACS Science Mode is used for the actual drag-free science operation. The DFACS control system has very strong interfaces with the LISA Technology Package payload which is a key aspect to master the design, development, and analysis of the DFACS. Linear as well as non-linear control methods are applied. The paper provides pre-flight predictions for the performance of both control modes and compares these predictions to the performance that is currently achieved in-orbit. Some results are also discussed for the mode transitions up to science mode, but the focus of the paper is on the Accelerometer mode performance and on the performance of the Science mode in steady state. Based on the achieved results, some lessons learnt are formulated to extend the results to the drag-free control system to be designed for future space-based gravity wave observatories like LISA.
      PubDate: 2018-12-01
      DOI: 10.1007/s12567-018-0204-x
      Issue No: Vol. 10, No. 4 (2018)
  • MICROSCOPE mission: drag-free and attitude control system expertise
           activities toward the scientific team
    • Authors: Stéphanie Delavault; Pascal Prieur; Thomas Liénart; Alain Robert; Pierre-Yves Guidotti
      Pages: 487 - 500
      Abstract: Microscope is a CNES-ESA-ONERA-CNRS-OCA-DLR-ZARM mission dedicated to the test of the Equivalence Principle with an improved accuracy of 10−15. The 300 kg drag-free microsatellite was launched on April 25th 2016 into a 710 km dawndusk sun-synchronous orbit for a 2-year mission. To comply with stringent requirements, the drag-free and attitude control system (DFACS) involves the scientific accelerometer as main sensor and a set of 8 cold gas proportional thrusters. Once in mission mode, within the CNES drag-free expertise center (CECT) the DFACS team provides several services to the system and to the scientific mission center: cold gas monitoring and management, ‘Attitude’ ancillary data, DFACS expertise ancillary data. For this purpose, expertise tools have been implemented in the CECT, using the flexibility and efficiency of Matlab™ utilities. This paper presents the role of the CECT within the mission and details the expertise activities of the DFACS team illustrated with some typical in flight results.
      PubDate: 2018-12-01
      DOI: 10.1007/s12567-018-0205-9
      Issue No: Vol. 10, No. 4 (2018)
  • GOES-R active vibration damping controller design, implementation, and
           on-orbit performance
    • Authors: Brian R. Clapp; Harald J. Weigl; Neil E. Goodzeit; Delano R. Carter; Timothy J. Rood
      Pages: 501 - 517
      Abstract: GOES-R series spacecraft feature a number of flexible appendages with modal frequencies below 3.0 Hz which, if excited by spacecraft disturbances, can be sources of undesirable jitter perturbing spacecraft pointing. To meet GOES-R pointing stability requirements, the spacecraft flight software implements an Active Vibration Damping (AVD) rate control law which acts in parallel with the nadir point attitude control law. The AVD controller commands spacecraft reaction wheel actuators based upon Inertial Measurement Unit (IMU) inputs to provide additional damping for spacecraft structural modes below 3.0 Hz which vary with solar wing angle. A GOES-R spacecraft dynamics and attitude control system identified model is constructed from pseudo-random reaction wheel torque commands and IMU angular rate response measurements occurring over a single orbit during spacecraft post-deployment activities. The identified Fourier model is computed on the ground, uplinked to the spacecraft flight computer, and the AVD controller filter coefficients are periodically computed on-board from the Fourier model. Consequently, the AVD controller formulation is based not upon pre-launch simulation model estimates but upon on-orbit nadir point attitude control and time-varying spacecraft dynamics. GOES-R high-fidelity time domain simulation results herein demonstrate the accuracy of the AVD identified Fourier model relative to the pre-launch spacecraft dynamics and control truth model. The AVD controller on-board the GOES-16 spacecraft achieves more than a ten-fold increase in structural mode damping for the fundamental solar wing mode while maintaining controller stability margins and ensuring that the nadir point attitude control bandwidth does not fall below 0.02 Hz. On-orbit GOES-16 spacecraft appendage modal frequencies and damping ratios are quantified based upon the AVD system identification, and the increase in modal damping provided by the AVD controller for each structural mode is presented. The GOES-16 spacecraft AVD controller frequency domain stability margins and nadir point attitude control bandwidth are presented along with on-orbit time domain disturbance response performance.
      PubDate: 2018-12-01
      DOI: 10.1007/s12567-017-0190-4
      Issue No: Vol. 10, No. 4 (2018)
  • End-to-end simulation and verification of GNC and robotic systems
           considering both space segment and ground segment
    • Authors: Heike Benninghoff; Florian Rems; Eicke Risse; Bernhard Brunner; Martin Stelzer; Rainer Krenn; Matthias Reiner; Christian Stangl; Marcin Gnat
      Pages: 535 - 553
      Abstract: In the framework of a project called on-orbit servicing end-to-end simulation, the final approach and capture of a tumbling client satellite in an on-orbit servicing mission are simulated. The necessary components are developed and the entire end-to-end chain is tested and verified. This involves both on-board and on-ground systems. The space segment comprises a passive client satellite, and an active service satellite with its rendezvous and berthing payload. The space segment is simulated using a software satellite simulator and two robotic, hardware-in-the-loop test beds, the European Proximity Operations Simulator (EPOS) 2.0 and the OOS-Sim. The ground segment is established as for a real servicing mission, such that realistic operations can be performed from the different consoles in the control room. During the simulation of the telerobotic operation, it is important to provide a realistic communication environment with different parameters like they occur in the real world (realistic delay and jitter, for example).
      PubDate: 2018-12-01
      DOI: 10.1007/s12567-017-0192-2
      Issue No: Vol. 10, No. 4 (2018)
  • Design and validation of a GNC system for missions to asteroids: the AIM
    • Authors: A. Pellacani; P. Kicman; M. Suatoni; M. Casasco; J. Gil; I. Carnelli
      Pages: 555 - 566
      Abstract: Deep space missions, and in particular missions to asteroids, impose a certain level of autonomy that depends on the mission objectives. If the mission requires the spacecraft to perform close approaches to the target body (the extreme case being a landing scenario), the autonomy level must be increased to guarantee the fast and reactive response which is required in both nominal and contingency operations. The GNC system must be designed in accordance with the required level of autonomy. The GNC system designed and tested in the frame of ESA’s Asteroid Impact Mission (AIM) system studies (Phase A/B1 and Consolidation Phase) is an example of an autonomous GNC system that meets the challenging objectives of AIM. The paper reports the design of such GNC system and its validation through a DDVV plan that includes Model-in-the-Loop and Hardware-in-the-Loop testing. Main focus is the translational navigation, which is able to provide online the relative state estimation with respect to the target body using exclusively cameras as relative navigation sensors. The relative navigation outputs are meant to be used for nominal spacecraft trajectory corrections as well as to estimate the collision risk with the asteroid and, if needed, to command the execution of a collision avoidance manoeuvre to guarantee spacecraft safety
      PubDate: 2018-12-01
      DOI: 10.1007/s12567-017-0189-x
      Issue No: Vol. 10, No. 4 (2018)
  • Hybrid optical navigation by crater detection for lunar pin-point landing:
           trajectories from helicopter flight tests
    • Authors: Guilherme F. Trigo; Bolko Maass; Hans Krüger; Stephan Theil
      Pages: 567 - 581
      Abstract: Accurate autonomous navigation capabilities are essential for future lunar robotic landing missions with a pin-point landing requirement, since in the absence of direct line of sight to ground control during critical approach and landing phases, or when facing long signal delays the herein before mentioned capability is needed to establish a guidance solution to reach the landing site reliably. This paper focuses on the processing and evaluation of data collected from flight tests that consisted of scaled descent scenarios where the unmanned helicopter of approximately 85 kg approached a landing site from altitudes of 50 m down to 1 m for a downrange distance of 200 m. Printed crater targets were distributed along the ground track and their detection provided earth-fixed measurements. The Crater Navigation (CNav) algorithm used to detect and match the crater targets is an unmodified method used for real lunar imagery. We analyze the absolute position and attitude solutions of CNav obtained and recorded during these flight tests, and investigate the attainable quality of vehicle pose estimation using both CNav and measurements from a tactical-grade inertial measurement unit. The navigation filter proposed for this end corrects and calibrates the high-rate inertial propagation with the less frequent crater navigation fixes through a closed-loop, loosely coupled hybrid setup. Finally, the attainable accuracy of the fused solution is evaluated by comparison with the on-board ground-truth solution of a dual-antenna high-grade GNSS receiver. It is shown that the CNav is an enabler for building autonomous navigation systems with high quality and suitability for exploration mission scenarios.
      PubDate: 2018-12-01
      DOI: 10.1007/s12567-017-0188-y
      Issue No: Vol. 10, No. 4 (2018)
  • Beyond L ∞ reaction wheel commanding: increased on-board autonomy
           through enhanced wheel failure handling
    • Authors: Stefan Winkler; Maik Evers; Benjamin Kraft
      Pages: 597 - 604
      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: 2018-12-01
      DOI: 10.1007/s12567-018-0212-x
      Issue No: Vol. 10, No. 4 (2018)
  • Experimental validation of GNSS repeater detection based on antenna arrays
           for maritime applications
    • Authors: Manuel Appel; Andreas Iliopoulos; Friederike Fohlmeister; Emilio Pérez Marcos; Manuel Cuntz; Andriy Konovaltsev; Felix Antreich; Michael Meurer
      Abstract: In this work, we present an antenna array-based algorithm to detect GNSS repeater and/or spoofing attacks with an experimental validation. With an array receiver capable of measuring the impinging ranging signals direction of arrival in terms of azimuth and elevation, it is possible to estimate the antenna platforms attitude. The fact that this information is computed (w.r.t. a reference frame) during the position calculation is used. We propose an algorithm aiming to find the relation between both representations. This mapping defines the receiver’s attitude in terms of pitch, roll and yaw angle. The residual of this mapping is used to construct a quality metric for the mapping. If a threshold is undershot, spoofing/repeating is indicated. The performance is demonstrated using software simulations. To show the capabilities under realistic conditions, a test platform is described. It consists of a real-time array receiver and a sampling device enabling post-processing. A maritime measurement campaign including two vessels—one acting as receiver and the other acting as transmitter—is portrayed. Finally, the real-time and post-processing performance of the algorithm is evaluated.
      PubDate: 2018-12-28
      DOI: 10.1007/s12567-018-0232-6
  • An academic approach to the multidisciplinary development of liquid-oxygen
           turbopumps for space applications
    • Authors: Julian D. Pauw; Lucrezia Veggi; Oskar J. Haidn; Christian Wagner; Thomas Thümmel; Daniel J. Rixen; Christoph Ager; Andy Wirtz; Alexander Popp; Wolfgang A. Wall; Bernd Wagner
      Abstract: Since 2015, the Technical University of Munich and the German Aerospace Center have intensified their research on liquid-oxygen turbopumps for space propulsion applications in a joined project. Together, they concentrate on the special challenges concerning the design, construction and operation of parts of turbopumps, as well as the development and validation of tools to interpret and predict the aforementioned. This is accompanied by experimental works on the level of components of the pump, the bearing unit and seals. Alongside this, numerical tools are used which have been developed both commercially and at the Technical University of Munich. The research combines the expertise of several institutes in the fields of space propulsion, applied mechanics, rotordynamics and numerical mechanics in a multidisciplinary approach. The incorporation of student and doctoral theses allows for the investigation of the components of liquid-oxygen turbopumps in a very wide variety. High emphasis is put on the interaction between the turbopump subsystems. The present paper presents the work on each subsystem and the links between them.
      PubDate: 2018-12-19
      DOI: 10.1007/s12567-018-0228-2
  • Evaluation and optimization of heat transfer at the interfaces of
           spacecraft assemblies
    • Authors: Simon Vandevelde; Alain Daidié; Marc Sartor
      Abstract: This paper presents the experimental and numerical work achieved in the aim of evaluating the heat transfer at the interfaces of threaded spacecraft assemblies, where Thermal Interface Materials (TIMs) are placed between two surfaces to improve the thermal performance. Developing a model to predict thermal resistance for such an assembly is a serious challenge, which has to take various influencing parameters into account. First, mechanical and thermal experiments used to characterise TIMs are summarised. Second, a numerical model capable of representing the behaviour of these materials is built. To verify the mechanical model, the preload of a single fastener assembly is measured and compared with a simulation. The thermo-mechanical model is verified by an assembly heated by a power resistor to evaluate the thermal aspects. The proposed material model is able to predict the loss of preload caused by creep/relaxation of the TIM and the temperature distribution of the assembly. This work is part of a broader study that seeks to develop a multi-physics approach to evaluate the heat transfer at interfaces of space application assemblies.
      PubDate: 2018-11-28
      DOI: 10.1007/s12567-018-0226-4
  • 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
  • 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
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