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  • 51. Carlsson, Ella
    et al.
    Brain, D.
    Space Science Laboratory, University of California, Berkeley.
    Luhmann, J.
    Space Science Laboratory, University of California, Berkeley.
    Barabash, Stas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Grigoriev, Alexander
    Nilsson, H.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Lundin, R.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Influence of IMF draping direction and crustal magnetic field location on Martian ion beams2008In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 56, no 6, 861-867 p.Article in journal (Refereed)
    Abstract [en]

    Data from the Ion Mass Analyzer (IMA) sensor of the ASPERA-3 instrument suite onboard Mars Express and data from the Magnetometer/Electron Reflectometer (MAG/ER) on Mars Global Surveyor have been analyzed to determine whether ion beam events (IBEs) are correlated with the direction of the draped interplanetary magnetic field (IMF) or the proximity of strong crustal magnetic fields to the subsolar point. We examined 150 IBEs and found that they are organized by IMF draping direction. However, no clear dependence on the subsolar longitude of the strongest magnetic anomaly is evident, making it uncertain whether crustal magnetic fields have an effect on the formation of the beams. We also examined data from the IMA sensor of the ASPERA-4 instrument suite on Venus Express and found that IBEs are observed at Venus as well, which indicates the morphology of the Martian and Venusian magnetotails are similar.

  • 52. Carlsson, Ella
    et al.
    Fedorov, A.
    Budnik, E.
    Barabash, Stas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Fredriksson, Sverker
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    First results from ASPERA-3 Ion Mass Analyzer (IMA) on CO2+ escape2005Conference paper (Other academic)
  • 53.
    Castro, Juan Francisco Buenestado
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Mier, Maria-Paz Zorzano
    Centro de Astrobiologia, INTA-CSIC, Madrid.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Liquid water at crater Gale, Mars2015In: Journal of Astrobiology and Outreach, ISSN 2332-2519, Vol. 3, no 3, 131Article in journal (Refereed)
    Abstract [en]

    Suspicion that Mars could have transient liquid water on its surface through deliquescence of salts to form aqueous solutions or brines is an old proposal whose inquiry was boosted by Phoenix Lander observations. It provided some images of what were claimed to be brines, the presence of which at its landing site was compatible with the atmospheric parameters and the composition of the soil observed. On the other hand, the so called Recurrent Slope Lineae (RSL) often imaged by orbiters, were considered as another clue pointing to the occurrence of the phenomenon, since it was thought that they might be caused by it. Now, Curiosity rover has performed the first in-situ multi-instrumental study on Mars’ surface, having collected the most comprehensive environmental data set ever taken by means of their instruments Rover Environmental Monitoring Station (REMS), Dynamic Albedo of Neutrons (DAN), and Sample Analysis at Mars (SAM). REMS is providing continuous and accurate measurements of the relative humidity and surface and air temperatures among other parameters, and DAN and SAM provide the water content of the regolith and the atmosphere respectively. Analysis of these data has allowed to establish the existence of a present day active water cycle between the atmosphere and the regolith, that changes according to daily and seasonal cycles, and that is mediated by the presence of brines during certain periods of each and every day. Importantly, the study shows that the conditions for the occurrence of deliquescence are favourable even at equatorial latitudes where, at first, it was thought they were not due to the temperature and relative humidity conditions. This study provides new keys for the understanding of martian environment, and opens interesting lines of research and studies for future missions which may even have a bearing on extant microbial life.

  • 54.
    Castro, Juan Francisco Buenestado
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Mier, Maria-Paz Zorzano
    Centro de Astrobiologia, INTA-CSIC, Madrid.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Planetary exploration; Mars on the scope2015In: Journal of Astrobiology and Outreach, ISSN 2332-2519, Vol. 3, no 3, 133Article in journal (Refereed)
    Abstract [en]

    This article summarizes a practical case of introduction to research and planetary exploration through the analysis of data from the Rover Environmental Monitoring Station (REMS), one of the ten scientific instruments on board the Curiosity rover of the Mars Science Laboratory (MSL), currently operating at the impact crater Gale, on Mars. It is the main aim of this work to show how the data that are publicly available at the Planetary Data System (PDS) can be used to introduce undergraduate students and the general public into the subject of surface exploration and the environment of Mars. In particular, the goal of this practice was to investigate and quantify the heat flux between the rover spacecraft and the Martian surface, the role of the atmosphere in this interaction, and its dependence with seasons, as well as to estimate the thermal contamination of the Martian ground produced by the rover. The ground temperature sensor (GTS) of the REMS instrument has measured in-situ, for the first time ever, the diurnal and seasonal variation of the temperature of the surface on Mars along the rover traverse. This novel study shows that the rover radiative heat flux varies between 10 and 22 W/m2 during the Martian year, which is more than 10% of the solar daily averaged insolation at the top of the atmosphere. In addition, it is shown that the radiative heat flux from the rover to the ground varies with the atmospheric dust load, being the mean annual amplitude of the diurnal variation of the surface temperature of 76 K, as a result of solar heating during the day and infrared cooling during the night. As a remarkable and unexpected outcome, it has been established that the thermal contamination produced by the rover alone induces, on average, a systematic shift of 7.5 K, which is indeed about 10% of the one produced by solar heating. This result may have implications for the design and operation of future surface exploration probes such as InSight.

  • 55.
    Charlton, J E
    et al.
    Sula systems.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Defer, E.
    L'Observatoire de Paris-LERMA.
    Prigent, C.
    L'Observatoire de Paris-LERMA.
    Moyna, B.
    Rutherford Appleton Laboratory.
    Lee, C.
    Met Office Hadley Centre, Exeter.
    Magt, P. De
    European Space Agency.
    Kangas, V.
    European Space Agency.
    A sub-millimetre wave airborne demonstrator for the observation of precipitation and ice clouds2010In: International Geoscience and Remote Sensing Symposium (IGARSS): Cape Town, South Africa, 12 - 17 July 2009, Piscataway, NJ: IEEE Communications Society, 2010, Vol. 3, 1023-1026 p.Conference paper (Refereed)
    Abstract [en]

    Sub-millimetre remote sensing instruments can provide critical information on cirrus clouds and an alternative way of measuring precipitation with a much smaller antenna than those which microwave sensors currently use. Two satellite concepts CIWSIR and GOMAS were proposed as ESA Earth Explorer missions; these were not funded, however they were recommended for an aircraft demonstrator. ESA studies have been performed to identify the optimum instrument and platform to demonstrate these satellite concepts. This paper reports on one of these preparatory activities; the design of a sub-millimetre wave airborne demonstrator for both ice cloud and precipitation observations which will be able to prove the feasibility of the scientific principles of both satellite missions. The paper will describe the derivation of the demonstrator requirements, consideration of the available platform and instrument options, the design of the selected concept, performance prediction and the outline of a proof of concept flight campaign. It will present the outcome of the study which describes a demonstrator design based upon the new Met Office International Sub-Millimetre Airborne Radiometer (ISMAR).

  • 56.
    Chauhan, Swarup
    et al.
    Forschungszentrum Karlsruhe.
    Höpfner, M.
    Stiller, G.P.
    Clarmann, T. von
    Funke, B.
    Glatthor, N.
    Grabowski, U.
    Linden, A.
    Kellmann, S.
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Steck, T.
    Fischer, H.
    Froidevaux, L.
    Lambert, A.
    Santee, M. L.
    Schwartz, M.
    Read, W.G.
    Livesey, N.
    MIPAS reduced spectral resolution UTLS-1 mode measurements of temperature, O3, HNO3, N2O, H2O and relative humidity over ice: retrievals and comparison to MLS2009In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, no 2, 337-353 p.Article in journal (Refereed)
    Abstract [en]

    During several periods since 2005 the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat has performed observations dedicated to the region of the upper troposphere/lower stratosphere (UTLS). For the duration of November/December 2005 global distributions of temperature and several trace gases from MIPAS UTLS-1 mode measurements have been retrieved using the IMK/IAA (Institut für Meteorologie und Klimaforschung/Instituto de Astrofísica de Andalucía) scientific processor. In the UTLS region a vertical resolution of 3 km for temperaure, 3 to 4 km for H2O, 2.5 to 3 km for O3, 3.5 km for HNO3 and 3.5 to 2.5 km for N2O has been achieved. The retrieved temperature, H2O, O3, HNO3, N2O, and relative humidity over ice are intercompared with the Microwave Limb Sounder (MLS/Aura) v2.2 data in the pressure range 316 to 0.68 hPa, 316 to 0.68 hPa, 215 to 0.68 hPa, 215 to 3.16 hPa, 100 to 1 hPa and 316 to 10 hPa, respectively. In general, MIPAS and MLS temperatures are biased within ±4 K over the whole pressure and latitude range. Systematic, latitude-independent differences of −2 to −4 K (MIPAS-MLS) at 121 hPa are explained by previously observed biases in the MLS v2.2 temperature retrievals. Temperature differences of −4 K up to 12 K above 10.0 hPa are present both in MIPAS and MLS with respect to ECMWF (European Centre for Medium-Range Weather Forecasts) and are likely due to deficiencies of the ECMWF analysis data. MIPAS and MLS stratospheric volume mixing ratios (vmr) of H2O are biased within ±1 ppmv, with indication of oscillations between 146 and 26 hPa in the MLS dataset. Tropical upper tropospheric values of relative humidity over ice measured by the two instruments differ by ±20% in the pressure range ~146 to 68 hPa. These differences are mainly caused by the MLS temperature biases. Ozone mixing ratios agree within 0.5 ppmv (10 to 20%) between 68 and 14 hPa. At pressures smaller than 10 hPa, MIPAS O3 vmr are higher than MLS by an average of 0.5 ppmv (10%). General agreement between MIPAS and MLS HNO3 is within the range of −1.0 (−10%) to 1.0 ppbv (20%). MIPAS HNO3 is 1.0 ppbv (10%) higher compared to MLS between 46 hPa and 10 hPa over the Northern Hemisphere. Over the tropics at 31.6 hPa MLS shows a low bias of more than 1 ppbv (>50%). In general, MIPAS and MLS N2O vmr agree within 20 to 40 ppbv (20 to 40%). Differences in the range between 100 to 21 hPa are attributed to a known 20% positive bias in MIPAS N2O data.

  • 57.
    Chhabra, Robin
    et al.
    Department of Mathematics and Statistics, University of Calgary.
    Emami, Reza
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    A linguistic approach to concurrent design2015In: Journal of Intelligent & Fuzzy Systems, ISSN 1064-1246, E-ISSN 1875-8967, Vol. 28, no 5, 1985-2001 p.Article in journal (Refereed)
    Abstract [en]

    This paper outlines a concurrent design methodology for multidisciplinary systems, which employs tools of fuzzy theory for the tradeoff in the design space. This methodology enhances communication between designers from various disciplines through introducing the universal notion of satisfaction and expressing the behaviour of multidisciplinary systems using the notion of energy. It employs fuzzy rule-bases, membership functions and parametric connectives in fuzzy logic to formalize subjective aspects of design, resulting in a two-phase simplification of the multi-objective constrained optimization of a design process. The methodology attempts to find a pareto-optimal solution for the design problem. In the primary phase of the methodology, a fuzzy-logic model is utilized to identify a region in the design space that contains the pareto-optimal design state, and a proper initial state is suggested for the optimization in the secondary phase, where the pareto-optimal solution is found. Finally, the impact of the designer's subjective attitude on the design is adjusted based on a system performance by utilizing an energy-based model of multidisciplinary systems. As an application, it is shown that the design of a five-degree-of-freedom industrial robot manipulator can be enhanced by using the methodology.

  • 58.
    Chhabra, Robin
    et al.
    MacDonald, Dettwiler and Associates Ltd., Brampton.
    Emami, Reza
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    A Unified Approach to Input-output Linearization and Concurrent Control of Underactuated Open-chain Multi-body Systems with Holonomic and Nonholonomic Constraints2016In: Journal of dynamical and control systems, ISSN 1079-2724, E-ISSN 1573-8698, Vol. 22, no 1, 129-168 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents a unified geometric framework to input-output linearization of open-chain multi-body systems with symmetry in their reduced phase space. This leads us to an output tracking controller for a class of underactuated open-chain multi-body systems with holonomic and nonholonomic constraints. We consider the systems with multi-degree-of-freedom joints and possibly with non-zero constant total momentum (in the holonomic case). The examples of these systems are free-base space manipulators and mobile manipulators. We first formalize the control problem, and rigorously state an output tracking problem for such systems. Then, we introduce a geometrical definition of the end-effector pose and velocity error. The main contribution of this paper is reported in Section 5, where we solve for the input-output linearization of the highly nonlinear problem of coupled manipulator and base dynamics subject to holonomic and nonholonomic constraints. This enables us to design a coordinate-independent controller, similar to a proportional-derivative with feed-forward, for concurrently controlling a free-base, multi-body system. Finally, by defining a Lyapunov function, we prove in Theorem 3 that the closed-loop system is exponentially stable. A detailed case study concludes this paper.

  • 59.
    Chhabra, Robin
    et al.
    Institute for Aerospace Studies, University of Toronto, MacDonald, Dettwiler and Associates Ltd., Brampton.
    Emami, Reza
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Symplectic reduction of holonomic open-chain multi-body systems with constant momentum2015In: Journal of Geometry and Physics, ISSN 0393-0440, E-ISSN 1879-1662, Vol. 89, 82-110 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents a two-step symplectic geometric approach to the reduction of Hamilton's equation for open-chain, multi-body systems with multi-degree-of-freedom holonomic joints and constant momentum. First, symplectic reduction theorem is revisited for Hamiltonian systems on cotangent bundles. Then, we recall the notion of displacement subgroups, which is the class of multi-degree-of-freedom joints considered in this paper. We briefly study the kinematics of open-chain multi-body systems consisting of such joints. And, we show that the relative configuration manifold corresponding to the first joint is indeed a symmetry group for an open-chain multi-body system with multi-degree-of-freedom holonomic joints. Subsequently using symplectic reduction theorem at a non-zero momentum, we express Hamilton's equation of such a system in the symplectic reduced manifold, which is identified by the cotangent bundle of a quotient manifold. The kinetic energy metric of multi-body systems is further studied, and some sufficient conditions are introduced, under which the kinetic energy metric is invariant under the action of a subgroup of the configuration manifold. As a result, the symplectic reduction procedure for open-chain, multi-body systems is extended to a two-step reduction process for the dynamical equations of such systems. Finally, we explicitly derive the reduced dynamical equations in the local coordinates for an example of a six-degree-of-freedom manipulator mounted on a spacecraft, to demonstrate the results of this paper. (C) 2014 Elsevier B.V. All rights reserved.

  • 60.
    Chhabra, Robin
    et al.
    MacDonald, Dettwiler and Ass. Ltd.
    Emami, Reza
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Karshon, Yael
    Department of Mathematics, University of Toronto.
    Reduction of Hamiltonian Mechanical Systems With Affine Constraints: A Geometric Unification2017In: Journal of Computational and Nonlinear Dynamics, ISSN 1555-1415, E-ISSN 1555-1423, Vol. 12, no 2, 021007Article in journal (Refereed)
    Abstract [en]

    This paper presents a geometrical approach to the dynamical reduction of a class of constrained mechanical systems. The mechanical systems considered are with affine nonholonomic constraints plus a symmetry group. The dynamical equations are formulated in a Hamiltonian formalism using the Hamilton-d'Alembert equation, and constraint forces determine an affine distribution on the configuration manifold. The proposed reduction approach consists of three main steps: (1) restricting to the constrained submanifold of the phase space, (2) quotienting the constrained submanifold, and (3) identifying the quotient manifold with a cotangent bundle. Finally, as a case study, the dynamical reduction of a two-wheeled rover on a rotating disk is detailed. The symmetry group for this example is the relative configuration manifold of the rover with respect to the inertial space. The proposed approach in this paper unifies the existing reduction procedures for symmetric Hamiltonian systems with conserved momentum, and for Chaplygin systems, which are normally treated separately in the literature. Another characteristic of this approach is that although it tracks the structure of the equations in each reduction step, it does not insist on preserving the properties of the system. For example, the resulting dynamical equations may no longer correspond to a Hamiltonian system. As a result, the invariance condition of the Hamiltonian under a group action that lies at the heart of almost every reduction procedure is relaxed

  • 61.
    Clarmann, T. von
    et al.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Glatthor, N.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Koukouli, M.E.
    Laboratory of Atmospheric Physics, Physics Department, Aristotle University of Thessaloniki.
    Stiller, G.P.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Funcke, B.
    Instituto de Astrofísica de Andalucía CSIC, Granada.
    Grabowski, U.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Höpfner, M.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Kellmann, S.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Linden, A.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Steck, T.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Fischer, H.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    MIPAS measurements of upper tropospheric C2H6 and O3 during the southern hemispheric biomass burning season in 20032007In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 7, no 22, 5861-5872 p.Article in journal (Refereed)
    Abstract [en]

    Under cloud free conditions, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) provides measurements of spectrally resolved limb radiances down to the upper troposphere. These are used to infer global distributions of mixing ratios of atmospheric constituents in the upper troposphere and the stratosphere. From 21 October to 12 November 2003, MIPAS observed enhanced amounts of upper tropospheric C2H6 (up to about 400 pptv) and ozone (up to about 80 ppbv). The absolute values of C2H6, however, may be systematically low by about 30% due to uncertainties of the spectroscopic data used. By means of trajectory calculations, the enhancements observed in the southern hemisphere are, at least partly, attributed to a biomass burning plume, which covers wide parts of the Southern hemisphere, from South America, the Atlantic Ocean, Africa, the Indian Ocean to Australia. The chemical composition of the part of the plume-like pollution belt associated with South American fires, where rainforest burning is predominant appears different from the part of the plume associated with southern African savanna burning. In particular, African savanna fires lead to a larger ozone enhancement than equatorial American fires. In this analysis, MIPAS observations of high ozone were disregarded where low CFC-11 (below 245 pptv) was observed, because this hints at a stratospheric component in the measured signal. Different type of vegetation burning (flaming versus smouldering combustion) has been identified as a candidate explanation for the different plume compositions

  • 62.
    Cockell, C.S.
    et al.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Bush, T.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Bryce, C.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Direito, S.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Fox-Powell, M.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Harrison, J.P
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Lammer, H.
    Austrian Academy of Sciences, Space Research Institute, Graz.
    Landenmark, H.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Nicholson, N.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Noack, L.
    Department of Reference Systems and Planetology, Royal Observatory of Belgium, Brussels.
    O'Malley-James, J.
    School of Physics and Astronomy, University of St Andrews, St Andrews.
    Payler, S.J.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Rushby, A.
    Centre for Ocean and Atmospheric Science (COAS), School of Environmental Sciences, University of East Anglia, Norwich.
    Samuels, T.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Schwendner, P.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Wadsworth, J.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Mier, Maria-Paz Zorzano
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Habitability: a review2016In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 16, no 1, 89-117 p.Article in journal (Refereed)
    Abstract [en]

    Habitability is a widely used word in the geoscience, planetary science, and astrobiology literature, but what does it mean? In this review on habitability, we define it as the ability of an environment to support the activity of at least one known organism. We adopt a binary definition of “habitability” and a “habitable environment.” An environment either can or cannot sustain a given organism. However, environments such as entire planets might be capable of supporting more or less species diversity or biomass compared with that of Earth. A clarity in understanding habitability can be obtained by defining instantaneous habitability as the conditions at any given time in a given environment required to sustain the activity of at least one known organism, and continuous planetary habitability as the capacity of a planetary body to sustain habitable conditions on some areas of its surface or within its interior over geological timescales. We also distinguish between surface liquid water worlds (such as Earth) that can sustain liquid water on their surfaces and interior liquid water worlds, such as icy moons and terrestrial-type rocky planets with liquid water only in their interiors. This distinction is important since, while the former can potentially sustain habitable conditions for oxygenic photosynthesis that leads to the rise of atmospheric oxygen and potentially complex multicellularity and intelligence over geological timescales, the latter are unlikely to. Habitable environments do not need to contain life. Although the decoupling of habitability and the presence of life may be rare on Earth, it may be important for understanding the habitability of other planetary bodies

  • 63.
    Conte, Davide
    et al.
    The Pennsylvania State University.
    Budzyń, Dorota
    Wrocław Institute of Technology.
    Burgoyne, Hayden
    California Institute of Technology.
    Di Carlo, Marilena
    University of Strathclyde.
    Fries, Dan
    University of Strathclyde.
    Grulich, Maria
    Technische Universität München.
    Heizmann, Sören
    Universität Stuttgart.
    Jethani, Henna
    University of Colorado, Boulder.
    Lapôtre, Mathieu
    California Institute of Technology.
    Roos, Tobias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Serrano Castillo, Encarnación
    Università di Bologna.
    Sherrmann, Marcel
    Universität Stuttgart.
    Vieceli, Rhiannon
    The Pennsylvania State University.
    Wilson, Lee
    California Institute of Technology.
    Wynard, Christopher
    University of Illinois Urbana-Champaign.
    Dees, Stacy
    National Institute of Aerospace .
    Innovative mars global international exploration (IMaGInE) mission2016In: AIAA Space and Astronautics Forum and Exposition, SPACE 2016, American Institute of Aeronautics and Astronautics, 2016Conference paper (Refereed)
    Abstract [en]

    This paper presents the conceptual design of the IMaGInE (Innovative Mars Global International Exploration) Mission whose mission objectives are to deliver a crew of four astronauts to the surface of Deimos and a robotic exploration mission to Phobos for approx-imately 343 days during the years 2031 and 2032, perform surface excursions, technology demonstrations, and In Situ Resource Utilization (ISRU) of the Martian moons as well as site reconnaissance for future human exploration of Mars. This is the winning mis-sion design of the 2016 Revolutionary Aerospace Systems Concepts-Academic Linkage (RASC-AL) competition, awarded with the "Best in Theme," "Best Overall," and "Pio-neering Exceptional Achievement Concept Honor (PEACH)" prizes. This competition was sponsored by NIA and NASA

  • 64.
    Conte, Davide
    et al.
    The Pennsylvania State University.
    Di Carlo, Marilena
    University of Strathclyde.
    Budzyń, Dorota
    ESA/EAC, Linder Höhe, Cologne.
    Burgoyne, Hayden
    Analytical Space, Inc., Boston.
    Fries, Dan
    Georgia Institute of Technology.
    Grulich, Maria
    ESA/ESTEC.
    Heizmann, Sören
    Universität Stuttgart.
    Jethani, Henna
    Blue Origin.
    Lapôtre, Mathieu
    California Institute of Technology.
    Roos, Tobias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Castillo, Encarnación Serrano
    Università di Bologna.
    Scherrmann, Marcel
    ESA/ESTEC.
    Vieceli, Rhiannon
    New Mexico Institute of Mining and Technology.
    Wilson, Lee
    California Institute of Technology.
    Wynard, Christopher
    NASA Johnson Space Center.
    Advanced concept for a crewed mission to the martian moons2017In: Acta Astronautica, ISSN 0094-5765, E-ISSN 1879-2030, Vol. 139, 545-563 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents the conceptual design of the IMaGInE (Innovative Mars Global International Exploration) Mission. The mission's objectives are to deliver a crew of four astronauts to the surface of Deimos and perform a robotic exploration mission to Phobos. Over the course of the 343 day mission during the years 2031 and 2032, the crew will perform surface excursions, technology demonstrations, In Situ Resource Utilization (ISRU) of the Martian moons, as well as site reconnaissance for future human exploration of Mars. This mission design makes use of an innovative hybrid propulsion concept (chemical and electric) to deliver a relatively low-mass reusable crewed spacecraft (approximately 100 mt) to cis-martian space. The crew makes use of torpor which minimizes launch payload mass. Green technologies are proposed as a stepping stone towards minimum environmental impact space access. The usage of beamed energy to power a grid of decentralized science stations is introduced, allowing for large scale characterization of the Martian environment. The low-thrust outbound and inbound trajectories are computed through the use of a direct method and a multiple shooting algorithm that considers various thrust and coast sequences to arrive at the final body with zero relative velocity. It is shown that the entire mission is rooted within the current NASA technology roadmap, ongoing scientific investments and feasible with an extrapolated NASA Budget. The presented mission won the 2016 Revolutionary Aerospace Systems Concepts - Academic Linkage (RASC-AL) competition.

  • 65.
    Davis, C. P.
    et al.
    University of Edinburgh, Institute of Atmospheric and Environmental Science.
    Evans, K. F.
    University of Colorado, Department of Atmosphere and Oceanic Sciences.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Wu, D. L.
    California Institute of Technology, Jet Propulsion Laboratory.
    Pumphrey, H. C.
    University of Edinburgh, Institute of Atmospheric and Environmental Science.
    3-D polarised simulations of space-borne passive mm/sub-mm midlatitude cirrus observations: a case study2006In: Atmospheric Chemistry and Physics Discussions, ISSN 1680-7367, E-ISSN 1680-7375, Vol. 6, 12701-12728 p.Article in journal (Other academic)
  • 66.
    Davis, Cory
    et al.
    University of Edinburgh, Institute of Atmospheric and Environmental Science.
    Evans, K. F.
    Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Wu, D. L.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Pumphrey, H. C.
    University of Edinburgh, Institute of Atmospheric and Environmental Science.
    3-D polarised simulations of space-borne passive mm/sub-mm midlatitude cirrus observations: a case study2007In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 7, no 15, 4149-4158 p.Article in journal (Refereed)
    Abstract [en]

    Global observations of ice clouds are needed to improve our understanding of their impact on earth's radiation balance and the water-cycle. Passive mm/sub-mm has some advantages compared to other space-borne cloud-ice remote sensing techniques. The physics of scattering makes forward radiative transfer modelling for such instruments challenging. This paper demonstrates the ability of a recently developed RT code, ARTS-MC, to accurately simulate observations of this type for a variety of viewing geometries corresponding to operational (AMSU-B, EOS-MLS) and proposed (CIWSIR) instruments. ARTS-MC employs an adjoint Monte-Carlo method, makes proper account of polarisation, and uses 3-D spherical geometry. The actual field of view characteristics for each instrument are also accounted for. A 3-D midlatitude cirrus scenario is used, which is derived from Chilbolton cloud radar data and a stochastic method for generating 3-D ice water content fields. These demonstration simulations clearly demonstrate the beamfilling effect, significant polarisation effects for non-spherical particles, and also a beamfilling effect with regard to polarisation.

  • 67.
    Delgado-Bonal, A.
    et al.
    Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR).
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Human vision is determined based on information theory2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, 36038Article in journal (Refereed)
    Abstract [en]

    It is commonly accepted that the evolution of the human eye has been driven by the maximum intensity of the radiation emitted by the Sun. However, the interpretation of the surrounding environment is constrained not only by the amount of energy received but also by the information content of the radiation. Information is related to entropy rather than energy. The human brain follows Bayesian statistical inference for the interpretation of visual space. The maximization of information occurs in the process of maximizing the entropy. Here, we show that the photopic and scotopic vision absorption peaks in humans are determined not only by the intensity but also by the entropy of radiation. We suggest that through the course of evolution, the human eye has not adapted only to the maximum intensity or to the maximum information but to the optimal wavelength for obtaining information. On Earth, the optimal wavelengths for photopic and scotopic vision are 555 nm and 508 nm, respectively, as inferred experimentally. These optimal wavelengths are determined by the temperature of the star (in this case, the Sun) and by the atmospheric composition.

  • 68.
    Delgado-Bonal, Alfonso
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Evaluation of the Atmospheric Chemical Entropy Production of Mars2015In: Entropy, ISSN 1099-4300, E-ISSN 1099-4300, Vol. 17, no 7, 5047-5062 p.Article in journal (Refereed)
    Abstract [en]

    Thermodynamic disequilibrium is a necessary situation in a system in which complex emergent structures are created and maintained. It is known that most of the chemical disequilibrium, a particular type of thermodynamic disequilibrium, in Earth's atmosphere is a consequence of life. We have developed a thermochemical model for the Martian atmosphere to analyze the disequilibrium by chemical reactions calculating the entropy production. It follows from the comparison with the Earth atmosphere that the magnitude of the entropy produced by the recombination reaction forming O 3 (O + O 2 + CO 2 O 3 + CO 2) in the atmosphere of the Earth is larger than the entropy produced by the dominant set of chemical reactions considered for Mars, as a consequence of the low density and the poor variety of species of the Martian atmosphere. If disequilibrium is needed to create and maintain self-organizing structures in a system, we conclude that the current Martian atmosphere is unable to support large physico-chemical structures, such as those created on Earth.

  • 69.
    Delgado-Bonal, Alfonso
    et al.
    Centro de Astrobiologia, INTA-CSIC, Madrid.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Solar cell temperature on Mars2015In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 118, 74-79 p.Article in journal (Refereed)
    Abstract [en]

    The operating temperature of a solar cell determines its efficiency and performance. This temperature depends on the materials used to build the cell but also on the environmental variables surrounding it (i.e., radiation, ambient temperature, wind speed and humidity). Several equations have been proposed to calculate this temperature, depending on these variables. Also, for Earth conditions, simplifiedequations have been developed, but are not valid for other planets, as Mars, where the environmental conditions are extremely different.In this paper, we develop a simplified equation to calculate the temperature of a solar cell under Mars environmental conditions and discuss the effect that altitude and wind on Mars might have on the solar cell temperature. The correct determination of the operating temperature of the cell will help to optimize the design of the next solar cell powered rovers for the exploration of Mars.

  • 70.
    Delgado-Bonal, Alfonso
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Martín, Sandra Vázquez
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Mier, Maria-Paz Zorzano
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Solar and wind exergy potentials for Mars2016In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 102, 550-558 p.Article in journal (Refereed)
    Abstract [en]

    The energy requirements of the planetary exploration spacecrafts constrain the lifetime of the missions, their mobility and capabilities, and the number of instruments onboard. They are limiting factors in planetary exploration. Several missions to the surface of Mars have proven the feasibility and success of solar panels as energy source. The analysis of the exergy efficiency of the solar radiation has been carried out successfully on Earth, however, to date, there is not an extensive research regarding the thermodynamic exergy efficiency of in-situ renewable energy sources on Mars. In this paper, we analyse the obtainable energy (exergy) from solar radiation under Martian conditions. For this analysis we have used the surface environmental variables on Mars measured in-situ by the Rover Environmental Monitoring Station onboard the Curiosity rover and from satellite by the Thermal Emission Spectrometer instrument onboard the Mars Global Surveyor satellite mission. We evaluate the exergy efficiency from solar radiation on a global spatial scale using orbital data for a Martian year; and in a one single location in Mars (the Gale crater) but with an appreciable temporal resolution (1 h). Also, we analyse the wind energy as an alternative source of energy for Mars exploration and compare the results with those obtained on Earth. We study the viability of solar and wind energy station for the future exploration of Mars, showing that a small square solar cell of 0.30 m length could maintain a meteorological station on Mars. We conclude that the low density of the atmosphere of Mars is responsible of the low thermal exergy efficiency of solar panels. It also makes the use of wind energy uneffective. Finally, we provide insights for the development of new solar cells on Mars.

  • 71.
    Delgado-Bonal, Alfonso
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Mier, Maria-Paz Zorzano
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Martian Top of the Atmosphere 10–420 nm spectral irradiance database and forecast for solar cycle 242016In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 134, 228-235 p.Article in journal (Refereed)
    Abstract [en]

    Ultraviolet radiation from 10 to 420 nm reaching Mars Top of the Atmosphere (TOA) and surface is important in a wide variety of fields such as space exploration, climate modeling, and spacecraft design, as it has impact in the physics and chemistry of the atmosphere and soil. Despite the existence of databases for UV radiation reaching Earth TOA, based in space-borne instrumentation orbiting our planet, there is no similar information for Mars. Here we present a Mars TOA UV spectral irradiance database for solar cycle 24 (years 2008–2019), containing daily values from 10 to 420 nm. The values in this database have been computed using a model that is fed by the Earth-orbiting Solar Radiation and Climate Experiment (SORCE) data. As the radiation coming from the Sun is not completely isotropic, in order to eliminate the geometrically related features but being able to capture the general characteristics of the solar cycle stage, we provide 3-, 7- and 15-days averaged values at each wavelength. Our database is of interest for atmospheric modeling and spectrally dependent experiments on Mars, the analysis of current and upcoming surface missions (rovers and landers) and orbiters in Mars. Daily values for the TOA UV conditions at the rover Curiosity location, as well as for the NASA Insight mission in 2016, and ESA/Russia ExoMars mission in 2018 are provided.

  • 72.
    Dhanaya, M.B.
    et al.
    Space Physics Laboratory, Vikram Sarabhai Space Center, Trivandrum.
    Bhardwaj, A.
    Space Physics Laboratory, Vikram Sarabhai Space Center, Trivandrum.
    Futaana, Y.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Fatemi, Shahab
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Holmström, M.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Barabash, Stas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Wieser, M.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Wurz, P.
    Physikalisches Institut, University of Bern.
    Thampi, R.S.
    Space Physics Laboratory, Vikram Sarabhai Space Center, Trivandrum.
    Proton entry into the near-lunar plasma wake for magnetic field aligned flow2013In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 40, no 2, 2913-2917 p.Article in journal (Refereed)
    Abstract [en]

    We report the first observation of protons in the near-lunar (100–200 km from the surface) and deeper (near anti-subsolar point) plasma wake when the interplanetary magnetic field (IMF) and solar wind velocity (vsw) are parallel (aligned flow; angle between IMF and vsw≤10°). More than 98% of the observations during aligned flow condition showed the presence of protons in the wake. These observations are obtained by the Solar Wind Monitor sensor of the Sub-keV Atom Reflecting Analyser experiment on Chandrayaan-1. The observation cannot be explained by the conventional fluid models for aligned flow. Back tracing of the observed protons suggests that their source is the solar wind. The larger gyroradii of the wake protons compared to that of solar wind suggest that they were part of the tail of the solar wind velocity distribution function. Such protons could enter the wake due to their large gyroradii even when the flow is aligned to IMF. However, the wake boundary electric field may also play a role in the entry of the protons into the wake.

  • 73.
    Dieval, Catherine
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Kallio, E.
    Finnish Meteorological Institute.
    Barabash, Stas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Stenberg, G.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Nilsson, H
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Futaana, Y.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Holmström, M.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Fedorov, A.
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Frahm, R.A.
    Southwest Research Institute, San Antonio, Texas.
    Jarvinen, R.
    Finnish Meteorological Institute, Helsinki.
    Brain, D.A.
    Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado.
    A case study of proton precipitation at Mars: Mars Express observations and hybrid simulations2012In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117Article in journal (Refereed)
    Abstract [en]

    Using the data from the Analyzer of Space Plasma and Energetic Atoms (ASPERA-3) experiment on board Mars Express and hybrid simulations, we have investigated the entry of protons into the Martian induced magnetosphere. We discuss one orbit on the dayside with observations of significant proton fluxes at altitudes down to 260 km on 27 February 2004. The protons observed below the induced magnetosphere boundary at an altitude of less than 700 km have energies of a few keV, travel downward, and precipitate onto the atmosphere. The measured energy flux and particle flux are 108–109 eV cm−2 s−1 and 105–106 H+ cm−2 s−1, respectively. The proton precipitation occurs because the Martian magnetosheath is small with respect to the heated proton gyroradius in the subsolar region. The data suggest that the precipitation is not permanent but may occur when there are transient increases in the magnetosheath proton temperature. The higher-energy protons penetrate deeper because of their larger gyroradii. The proton entry into the induced magnetosphere is simulated using a hybrid code. A simulation using a fast solar wind as input can reproduce the high energies of the observed precipitating protons. The model shows that the precipitating protons originate from both the solar wind and the planetary exosphere. The precipitation extends over a few thousand kilometers along the orbit of the spacecraft. The proton precipitation does not necessarily correlate with the crustal magnetic anomalies.

  • 74.
    Dieval, Catherine
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Stenberg, G.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Nilsson, H.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Barabash, Stas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    A statistical study of proton precipitation onto the Martian upper atmosphere: Mars Express observations2013In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, 1972-1983 p.Article in journal (Refereed)
    Abstract [en]

    Due to the small size of the Martian magnetic pile-up region, especially at the subsolar point, heated protons with high enough energy can penetrate the induced magnetosphere boundary (IMB) without being backscattered, i.e., they precipitate. We present a statistical study of the downgoing ~ keV proton fluxes measured in the Martian ionosphere by the Analyzer of Space Plasma and Energetic Atoms (ASPERA-3) experiment onboard the Mars Express spacecraft. We find that on the dayside, the events of proton penetration occur during 3% of the observation time: the precipitation is an intermittent phenomenon. The proton events carry on average ~0.2% of the incident solar wind flux. Therefore, the induced magnetosphere is an effective shield against the magnetosheath protons. The events are more frequent during fast solar wind conditions than during slow solar wind conditions. The sporadic proton penetration is thought to be caused by transient increases in the magnetosheath temperature. The precipitating flux is higher on the dayside than on the nightside, and its spatial deposition is controlled by the solar wind convective electric field. The largest crustal magnetic anomalies tend to decrease the proton precipitation in the Southern hemisphere. The particle and energy fluxes vary in the range 104-106 cm-2 s-1 and 107-109 eVcm-2 s-1, respectively. The corresponding heating for the dayside atmosphere is on average negligible compared to the solar extreme ultraviolet heating, although the intermittent penetration may cause local ionization. The net precipitating proton particle flux input to the dayside ionosphere is estimated as 1.2 · 1021 s-1.

  • 75.
    Dieval, Catherine
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Stenberg, G.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Nilsson, Hans
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Edberg, N.J.T.
    Swedish Institute of Space Physics, Uppsala.
    Barabash, Stas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Reduced proton and alpha particle precipitations at Mars during solar wind pressure pulses: Mars Express results2013In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 118, no 6, 3421-3429 p.Article in journal (Refereed)
    Abstract [en]

    1] We performed a statistical study of downward moving protons and alpha particles of ~keV energy (assumed to be of solar wind origin) inside the Martian induced magnetosphere from July 2006 to July 2010. Ion and electron data are from the Analyzer of Space Plasma and Energetic Atoms (ASPERA-3) package on board Mars Express. We investigated the solar wind ion entry into the ionosphere, excluding intervals of low-altitude magnetosheath encounters. The study compares periods of quiet solar wind conditions and periods of solar wind pressure pulses, including interplanetary coronal mass ejections and corotating interaction regions. The solar wind ion precipitation appears localized and/or intermittent, consistent with previous measurements. Precipitation events are less frequent, and the precipitating fluxes do not increase during pressure pulse encounters. During pressure pulses, the occurrence frequency of observed proton precipitation events is reduced by a factor of ~3, and for He2+ events the occurrence frequency is reduced by a factor of ~2. One explanation is that during pressure pulse periods, the mass loading of the solar wind plasma increases due to a deeper penetration of the interplanetary magnetic flux tubes into the ionosphere. The associated decrease of the solar wind speed thus increases the pileup of the interplanetary magnetic field on the dayside of the planet. The magnetic barrier becomes thicker in terms of solar wind ion gyroradii, causing the observed reduction of H+/He2+ precipitations.

  • 76.
    Dikmen, Serkan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Development of Star Tracker Attitude and Position Determination System for Spacecraft Maneuvering and Docking Facility2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Attitude and position determination systems in satellites are absolutely necessary to keep the desired trajectory. A very accurate, reliable and most used sensor for attitude determination is the star tracker, which orient itself in space by observing and comparing star constellations with known star patterns. For on earth tests of movements and docking maneuvers of spacecrafts, the new Spacecraft Maneuvering and Docking (SMD) facility at the chair of Aerospace Information Technology at the University of Würzburg has been built. Air bearing systems on the space ve- hicles help to create micro gravity environment on a smooth surface and simulate an artificial space-like surrounding. A new star tracker based optical sensor for indoor application need to be developed in order to get the attitude and position of the vehicles. The main objective of this thesis is to research on feasible star tracking algorithms for the SMD facility first and later to implement a star detection software framework with new developed voting methods to give the star tracker system its fully autonomous function of attitude determination and position tracking. Furthermore, together with image processing techniques, the software framework is embedded into a controller board. This thesis proposes also a wireless network system for the facility, where all the devices on the vehicles can uniquely communicate within the same network and a devel- opment of a ground station to monitor the star tracker process has also been introduced. Multiple test results with different scenarios on position tracking and attitude determination, discussions and suggestions on improvements complete the entire thesis work. 

  • 77.
    Dillibabu, Surender
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Design,Analysis, and prototype of underwater glider2016Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
  • 78.
    Downs, R.T.
    et al.
    University of Arizona, Department of Geosciences, University of Arizona, Tucson, Department of Geology, University of Arizona, Tucson.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Determining Mineralogy on Mars with the CheMin X-Ray Diffractometer2015In: Elements, ISSN 1811-5209, E-ISSN 1811-5217, Vol. 11, no 1, 45-50 p.Article in journal (Refereed)
    Abstract [en]

    The rover Curiosity is conducting X-ray diffraction experiments on the surface of Mars using the CheMin instrument. The analyses enable identification of the major and minor minerals, providing insight into the conditions under which the samples were formed or altered and, in turn, into past habitable environments on Mars. The CheMin instrument was developed over a twenty-year period, mainly through the efforts of scientists and engineers from NASA and DOE. Results from the first four experiments, at the Rocknest, John Klein, Cumberland, and Windjana sites, have been received and interpreted. The observed mineral assemblages are consistent with an environment hospitable to Earth-like life, if it existed on Mars.

  • 79.
    Díaz, José Luis Pérez
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Álvarez-Valenzuela, Marco Antonio
    Saint George Tech Ltd.
    Rodríguez-Celis, F.
    MAG SOAR S.L., Av. de Europa, 82, Valdemoro.
    Surface freezing of water2016In: SpringerPlus, E-ISSN 2193-1801, Vol. 5, no 1, 629Article in journal (Refereed)
    Abstract [en]

    Freezing, melting, evaporation and condensation of water are essential ingredients for climate and eventually life on Earth. In the present work, we show how surface freezing of supercooled water in an open container is conditioned and triggered—exclusively—by humidity in air. Additionally, a change of phase is demonstrated to be triggered on the water surface forming surface ice crystals prior to freezing of bulk. The symmetry of the surface crystal, as well as the freezing point, depend on humidity, presenting at least three different types of surface crystals. Humidity triggers surface freezing as soon as it overpasses a defined value for a given temperature, generating a plurality of nucleation nodes. An evidence of simultaneous nucleation of surface ice crystals is also provided

  • 80.
    Earle, M.E.
    et al.
    Department of Earth and Environmental Sciences, University of Waterloo.
    Kuhn, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Khalizov, A.F.
    Department of Earth and Environmental Sciences, University of Waterloo.
    Sloan, J.J.
    Department of Earth and Environmental Sciences, University of Waterloo.
    Volume nucleation rates for homogeneous freezing in supercooled water microdroplets: results from a combined experimental and modelling approach2009In: Atmospheric Chemistry and Physics Discussions, ISSN 1680-7367, E-ISSN 1680-7375, Vol. 9, no 5, 22883-22927 p.Article in journal (Refereed)
    Abstract [en]

    Temperature-dependent volume nucleation rate coefficients for supercooled water droplets, JV(T), are derived from infrared extinction measurements in a cryogenic laminar aerosol flow tube using a microphysical model. The model inverts water and ice aerosol size distributions retrieved from experimental extinction spectra by considering the evolution of a measured initial droplet distribution via homogeneous nucleation and the exchange of vapour-phase water along a well-defined temperature profile. Experiment and model results are reported for supercooled water droplets with mode radii of 1.0, 1.7, and 2.9 α1/4m. Values of mass accommodation coefficients for evaporation of water droplets and vapour deposition on ice particles are also determined from the model simulations. The coefficient for ice deposition was found to be approximately 0.031, while that for water evaporation was 0.054. Results are considered in terms of the applicability of classical nucleation theory to the freezing of micrometre-sized droplets in cirrus clouds, with implications for the parameterization of homogeneous ice nucleation in numerical models.

  • 81.
    Earle, M.E.
    et al.
    Department of Earth and Environmental Sciences, University of Waterloo.
    Kuhn, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Khalizov, A.F.
    Department of Earth and Environmental Sciences, University of Waterloo.
    Sloan, J.J.
    Department of Earth and Environmental Sciences, University of Waterloo.
    Volume nucleation rates for homogeneous freezing in supercooled water microdroplets: results from a combined experimental and modelling approach2010In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 10, no 16, 7945-7961 p.Article in journal (Refereed)
    Abstract [en]

    Temperature-dependent volume nucleation rate coefficients for supercooled water droplets, JV(T), are derived from infrared extinction measurements in a cryogenic laminar aerosol flow tube using a microphysical model. The model inverts water and ice aerosol size distributions retrieved from experimental extinction spectra by considering the evolution of a measured initial droplet distribution via homogeneous nucleation and the exchange of vapour-phase water along a well-defined temperature profile. Experiment and model results are reported for supercooled water droplets with mean radii of 1.0, 1.7, and 2.9 μ1/4m. Values of mass accommodation coefficients for evaporation of water droplets and vapour deposition on ice particles are also determined from the model simulations. The coefficient for ice deposition was found to be 0.031 ± 0.001, while that for water evaporation was 0.054 ± 0.012. Results are considered in terms of the applicability of classical nucleation theory to the freezing of micrometre-sized droplets in cirrus clouds, with implications for the parameterization of homogeneous ice nucleation in numerical models.

  • 82.
    Ekman, Jonas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Antti, Marta-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Emami, Reza
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Törlind, Peter
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Kuhn, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Nilsson, Hans
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Minami, Ichiro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Öhrwall Rönnbäck, Anna
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Zorzano Mier, Maria-Paz
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Parida, Vinit
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Behar, Etienne
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Wolf, Veronika
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Dordlofva, Christo
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Mendaza de Cal, Maria Teresa
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Jamali, Maryam
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Roos, Tobias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Ottemark, Rikard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Nieto, Chris
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Soria Salinas, Álvaro Tomás
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Vázquez Martín, Sandra
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Nyberg, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Neikter, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lindwall, Angelica
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Fakhardji, Wissam
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Projekt: Rymdforskarskolan2015Other (Other (popular science, discussion, etc.))
    Abstract [en]

    The Graduate School of Space Technology

  • 83.
    Ekström, M.
    et al.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Eriksson, P.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Read, W. G.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Murtagh, D. P.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Comparison of satellite limb-sounding humidity climatologies of the uppermost tropical troposphere2008In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 8, no 2, 309-320 p.Article in journal (Refereed)
    Abstract [en]

    Humidity climatologies of the tropical uppermost troposphere from satellite limb emission measurements have been compared. Four instruments are considered; UARS-MLS, Odin-SMR, and Aura-MLS operating in the microwave region, and MIPAS in the infrared region. A reference for the comparison is obtained by MOZAIC in-situ measurements. The upper tropospheric humidity products were compared on basis of their empirical probability density functions and seasonally averaged horizontal fields at two altitude layers, 12 and 15 km. The probability density functions of the microwave datasets were found to be in very good agreement with each other, and were also consistent with MOZAIC. The average seasonal humidities differ with less than 10%RHi between the instruments, indicating that stated measurement accuracies of 20–30% are conservative estimates. The systematic uncertainty in Odin-SMR data due to cloud correction was also independently estimated to be 10%RHi. MIPAS humidity profiles were found to suffer from cloud contamination, with only 30% of the measurements reaching into the upper troposphere, but under clear-sky conditions there is a good agreement between MIPAS, Odin-SMR and Aura-MLS. Odin-SMR and the two MLS datasets can be treated as independent, being based on different underlying spectroscopy and technology. The good agreement between the microwave limb-sounders, and MOZAIC, is therefore an important step towards understanding the upper tropospheric humidity. The found accuracy of 10%RHi is approaching the level required to validate climate modelling of the upper troposphere humidity. The comparison of microwave and infrared also stresses that microwave limb-sounding is necessary for a complete view of the upper troposphere.

  • 84.
    Eliasson, Salomon
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Ice clouds in satellite observations and climate models2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Ice clouds have an important role in climate. They are strong modulators of the outgoing longwave radiation and the incoming shortwave radiation and are an integral part of the hydrological cycle. However, our knowledge about them is inadequate. Climate models are far from consensus on the magnitude and spatial distribution of several cloud parameters, including the column integrated cloud ice amount, called Ice Water Path (IWP). The lack of adequate constraints from observations is a main contributor to the non-consensus. Cloud ice retrievals from satellite measurements are an important source of observations, since they are global and continuous. However, they carry large uncertainties since different sensors are sensitive to different aspects of clouds, and because clouds are largely inhomogeneous with complicated microphysical properties. Satellite observations are also notoriously difficult to use for model evaluation, due to a mismatch on how cloud parameters are defined in the models compared to what is actually observed. No satellite instrument can measure information from the entire cloud column, as desired from the model point of view. This thesis mainly concerns IWP, which is one of the key cloud parameters. By measuring clouds using different techniques at different wavelengths, the IWP retrievals are sensitive to different parts of the ice particle size distribution, and different depths in the cloud. A main aim of the PhD project is to assess the agreement of datasets based on different techniques and how they may be complementary. This investigation of IWP in observations and models starts by a comparison study of monthly averaged IWP from a climate perspective. The study shows that the differences in IWP within a group of models, and compared to observations are up to an order of magnitude. This confirmed results from previous studies, but in this study, large differences in the spatial distribution of IWP are also identified. The spatial distributions of modelled IWP indicate that they are in disagreement on where the Tropical convective regions are and how much IWP is found there in relation to the global averaged IWP. However, the observational datasets also differ by up to an order of magnitude and the uncertainties for the monthly averaged observations are almost intangibly large. This prompted a new study comparing strictly collocated observations to each other. By doing so, large uncertainties caused by spatially and temporally averaging data were removed. DARDAR, with IWP retrievals based on a combination of Radar and Lidar measurements, is regarded as the best dataset of IWP, and was therefore chosen as the reference dataset. This study determines that DARDAR has a relatively low uncertainty of between 20% to 50%. The validity ranges of the other datasets, i.e., the IWP values where data are trustworthy, are determined by comparing to DARDAR IWP. Once established for each dataset, the systematic and random errors of each dataset are quantified. It is shown that retrievals based on solar reflectance measurements are sensitive to the largest range of IWP values, from ∼30 gm-2 to ∼7000 gm-2, and have random uncertainties less than a factor of two throughout most of this range. To analyse the uncertainties further, the collocated measurements are assessed separately in different types of cloudy scenarios. It is shown that large uncertainties are attributed to the assumed cloud phase and the choice of IWP parameterisations. Further in depth studies on models were carried out using the EC-Earth climate model. A validation study of several upper tropospheric parameters showed that the model captures most large-scale features but has problems with clouds. This led to another study comparing the modelled evolution of several atmospheric variables before and after deep convection events to that of observations. A follow-up study analyses the impacts of clouds on upper tropospheric humidity (UTH) retrievals depending on if they are based on microwave or infrared measurements. By these cross-dataset comparisons we are closer to understanding how to utilise datasets that normally are not comparable due to their different sensitivities.

  • 85.
    Eliasson, Salomon
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Ice clouds in satellite observations and climate models2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis concerns the microphysical properties of clouds made up of ice particles, called ice clouds. Ice clouds are strong modulators of the outgoing longwave radiation and incoming shortwave radiation, yet our knowledge on several key ice cloud properties, which govern the magnitude and sign of the net contribution to the Earth’s atmospheric radiation budget, is inadequate. For instance, currently climate models are far from consensus on the magnitude and spatial distribution of ice water path (IWP), a vital radiative property of ice clouds, and the main property of concern in this thesis. The large spread amongst the models in terms of IWP is mostly due to the lack of constraints from observations on ice cloud properties. The lacking constraints reflect the major difficulties faced in observing global ice cloud properties.In-situ measurements provide useful sources of information on ice clouds, but are far from adequate due to the sparseness of measurements. Cloud ice observations from satellites provides a global view and is the most useful source of information. However, measurements from satellites also carry large uncertainties and are notoriously difficult to use for model evaluation, due to a mismatch on how IWP is defined in the models compared to what is actually observed. Not one satellite instrument can measure ice particle information from the entire ice cloud column, as desired from the model point of view. Satellite observations of IWP depend for the most part on the wavelength spectrum the instrument measures in, hence the instruments measure related, but different information on clouds.A study addressing the satellite observed and modeled IWP is presented in the first appended article: Eliasson et al. [2011]. Large differences between climate models are observations, especially in areas with frequent deep convection, were reported and discussed. The second appended article is a first evaluation study of cloud parameters, such as IWP, in the EC-Earth climate model using satellite A-Train observations. The model captures large-scale features for the most part but has problems related to ice water content and cloud fraction. This is strongly linked to the treatment of precipitation.The thesis contains introductory chapters on ice clouds; their formation, radiative importance, and representation in climate models. This is followed by a more in depth chapter on the observational data. The different satellite techniques are then discussed following a radiation physics and radiative transfer background section.

  • 86. Eliasson, Salomon
    et al.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Milz, Mathias
    A study on the ice water path descrepencies between global climate models2008Conference paper (Other academic)
  • 87.
    Eliasson, Salomon
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Buehler, Stefan
    Milz, Mathias
    Eriksson, P.
    Department of Radio and Space Science, Chalmers University of Technology.
    John, V.O.
    Met Office Hadley Centre, Exeter.
    Assessing modelled spatial distributions of ice water path using satellite data2010In: Atmospheric Chemistry and Physics Discussions, ISSN 1680-7367, E-ISSN 1680-7375, Vol. 10, no 5, 12185-12224 p.Article in journal (Refereed)
    Abstract [en]

    The climate models used in the IPCC AR4 show large differences in monthly mean cloud ice. The most valuable source of information that can be used to potentially constrain the models is global satellite data. For this, the data sets must be long enough to capture the inter-annual variability of Ice Water Path (IWP). PATMOS-x was used together with ISCCP for the annual cycle evaluation in Fig. 7 while ECHAM-5 was used for the correlation with other models in Table 3. A clear distinction between ice categories in satellite retrievals, as desired from a model point of view, is currently impossible. However, long-term satellite data sets may still be used to indicate the climatology of IWP spatial distribution. We evaluated satellite data sets from CloudSat, PATMOS-x, ISCCP, MODIS and MSPPS in terms of monthly mean IWP, to determine which data sets can be used to evaluate the climate models. IWP data from CloudSat cloud profiling radar provides the most advanced data set on clouds. As CloudSat data are too short to evaluate the model data directly, it was mainly used here to evaluate IWP from the other satellite data sets. ISCCP and MSPPS were shown to have comparatively low IWP values. ISCCP shows particularly low values in the tropics, while MSPPS has particularly low values outside the tropics. MODIS and PATMOS-x were in closest agreement with CloudSat in terms of magnitude and spatial distribution, with MODIS being the best of the two. As PATMOS-x extends over more than 25 years and is in fairly close agreement with CloudSat, it was chosen as the reference data set for the model evaluation. In general there are large discrepancies between the individual climate models, and all of the models show problems in reproducing the observed spatial distribution of cloud-ice. Comparisons consistently showed that ECHAM-5 is the GCM from IPCC AR4 closest to satellite observations

  • 88.
    Eliasson, Salomon
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Eriksson, P.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    John, V.O.
    Met Office Hadley Centre, Exeter.
    Assessing observed and modelled spatial distributions of ice water path using satellite data2011In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 11, no 1, 375-391 p.Article in journal (Refereed)
    Abstract [en]

    The climate models used in the IPCC AR4 show large differences in monthly mean ice water path (IWP). The most valuable source of information that can be used to potentially constrain the models is global satellite data. The satellite datasets also have large differences. The retrieved IWP depends on the technique used, as retrievals based on different techniques are sensitive to different parts of the cloud column. Building on the foundation of Waliser et al. (2009), this article provides a more comprehensive comparison between satellite datasets. IWP data from the CloudSat cloud profiling radar provide the most advanced dataset on clouds. For all its unmistakable value, CloudSat data are too short and too sparse to assess climatic distributions of IWP, hence the need to also use longer datasets. We evaluate satellite datasets from CloudSat, PATMOS-x, ISCCP, MODIS and MSPPS in terms of monthly mean IWP, in order to determine the differences and relate them to the sensitivity of the instrument used in the retrievals. This information is also used to evaluate the climate models, to the extent that is possible. ISCCP and MSPPS were shown to have comparatively low IWP values. ISCCP shows particularly low values in the tropics, while MSPPS has particularly low values outside the tropics. MODIS and PATMOS-x were in closest agreement with CloudSat in terms of magnitude and spatial distribution, with MODIS being the better of the two. Additionally PATMOS-x and ISCCP, which have a temporal range long enough to capture the inter-annual variability of IWP, are used in conjunction with CloudSat IWP (after removing profiles that contain precipitation) to assess the IWP variability and mean of the climate models. In general there are large discrepancies between the individual climate models, and all of the models show problems in reproducing the observed spatial distribution of cloud-ice. Comparisons consistently showed that ECHAM-5 is probably the GCM from IPCC AR4 closest to satellite observations

  • 89.
    Eliasson, Salomon
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Holl, Gerrit
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Kuhn, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Stengel, M.
    Iturbe-Sanchez, F.
    Johnston, M.
    Systematic and random errors between collocated satellite ice water path observations2013In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 118, no 6, 2629-2642 p.Article in journal (Refereed)
    Abstract [en]

    There remains large disagreement between IWP in observational datasets, largely because the sensors observe different parts of the ice particle size distribution. A detailed comparison of retrieved IWP from satellite observations in the Tropics ({plus minus}30{degree sign} latitude) in 2007 is made using collocated measurements. The DARDAR IWP dataset, based on combined Radar/Lidar measurements, is used as a reference as it provides arguably the best estimate of the total column IWP. For each dataset, usable IWP dynamic ranges are inferred from this comparison. IWP retrievals based on solar reflectance measurements, MODIS, and AVHRR-based CMSAF, and PATMOS-x, were found to be correlated with DARDAR over a large IWP range (~20-7000 g/m-2;). The random errors of the collocated datasets have a close to log-normal distribution, and the combined random error of MODIS and DARDAR is less than a factor of 2, which also sets the upper limit for MODIS alone. In the same way the upper limit for the random error of all considered datasets is determined. Datasets based on passive microwave measurements,MSPPS, MiRS, and CMO, are largely correlated with DARDAR for IWP values larger than approximately 700 g/m². The combined uncertainty between these datasets and DARDAR in this range is slightly less MODIS-DARDAR, but the systematic bias is nearly an order of magnitude.

  • 90.
    Eliasson, Salomon
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Mendrok, Jana
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Systematic and random errors between collocated satellite ice water path observations2013Conference paper (Other academic)
    Abstract [en]

    There remains large disagreement between ice-water path (IWP) in observational data sets, largely because the sensors observe different parts of the ice particle size distribution. A detailed comparison of retrieved IWP from satellite observations in the Tropics (±30° latitude) in 2007 was made using collocated measurements. The radio detection and ranging(radar)/light detection and ranging (lidar) (DARDAR) IWP data set, based on combined radar/lidar measurements, is used as a reference because it provides arguably the best estimate of the total column IWP. For each data set, usable IWP dynamic ranges are inferred from this comparison. IWP retrievals based on solar reflectance measurements, in the moderate resolution imaging spectroradiometer (MODIS), advanced very high resolution radiometer–based Climate Monitoring Satellite Applications Facility (CMSAF), and Pathfinder Atmospheres-Extended (PATMOS-x) datasets, were found to be correlated with DARDAR over a large IWP range (~20–7000 g m-2). The random errors of the collocated data sets have a close to lognormal distribution, and the combined random error of MODIS and DARDAR is less than a factor of 2, which also sets the upper limit for MODIS alone. In the same way, the upper limit for the random error of all considered data sets is determined. Data sets based on passive microwave measurements, microwave surface and precipitation products system (MSPPS), microwave integrated retrieval system (MiRS), and collocated microwave only (CMO), are largely correlated with DARDAR for IWP values larger than approximately 700 g m-2. The combined uncertainty between these data sets and DARDAR in this range is slightly less MODIS-DARDAR, but the systematic bias is nearly an order of magnitude.

  • 91.
    Emami, Reza
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Bazzocchi, Michael C. F.
    Institute for Aerospace Studies, University of Toronto.
    Low-thrust orbit transfer of Arjuna-type asteroids2016In: AIAA/AAS Astrodynamics Specialist Conference, 2016, American Institute of Aeronautics and Astronautics, 2016Conference paper (Refereed)
    Abstract [en]

    This paper investigates the accessible low-thrust transfer trajectories for a near-Earth asteroid transfer mission. The target asteroids considered are Arjuna type asteroids, which are characterized by their Earth-like orbital paths including low-eccentricity and low-inclination. The asteroid range is characterized by specific semi-major axes and transfer angles to provide an overall assessment of the potential Arjuna transfer domain. A single hovering ion beam spacecraft is employed for the task of asteroid redirection. The method utilizes a continuous thrust over the duration of the transfer maneuver to redirect the asteroid to an Earth bound orbit. The transfer model employs a minimized form of Gauss's variational equations to determine the available trajectories for asteroid redirection. The transfer model employs, in addition to the aforementioned orbital equations, spacecraft thruster and sizing metrics, as well as mission cost analysis formulae. The system parameters and orbital transfer paths are assessed with regards to key mission parameters, namely, timeframe for redirection, number of orbital revolutions, system mass, propellant mass, thrust, power, system cost, and financial return rate

  • 92.
    Emami, Reza
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Institute for Aerospace Studies, University of Toronto.
    Kereluk, Jason Alexander
    Space Mechatronics Group, Institute for Aerospace Studies, University of Toronto.
    System, method and computer program for autonomously emulating robot manipulators of continuously-varying configurationsPatent (Other (popular science, discussion, etc.))
    Abstract [en]

    The invention is a modular and autonomously reconfigurable manipulator system which introduces a new dimension to the versatility of robot manipulation for diverse tasks. The hardware component is a redundant mechanism which can lock any number of its joints at any relative position to form a particular configuration with a certain number of degrees of freedom and specific values for kinematic, dynamic and control parameters, optimum for a given task to be performed. The process of identifying the optimum configuration for a given task and implementing it on the manipulator is done autonomously through the system software. Therefore, no manual interaction is required to form a new configuration most suitable for a given task. The kinematic, dynamic and control parameters of the system can vary continuously enabling the manipulator to form virtually an infinite number of configurations.

  • 93.
    Emami, Reza
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Ng, Larry
    Institute for Aerospace Studies, University of Toronto.
    Concurrent Individual And Social Learning In Robot Teams2016In: Computational intelligence, ISSN 0824-7935, E-ISSN 1467-8640, Vol. 32, no 3, 420-438 p.Article in journal (Refereed)
    Abstract [en]

    This article discusses effective mechanisms that enable a group of robots to autonomously generate, adapt, and enhance team behaviors while improving their individual performance simultaneously. Two promising team learning concepts, namely, cooperative learning and advice-sharing, are integrated to provide a platform that encompasses a comprehensive approach to team-performance enhancement. These methods were examined in relation to the performance characteristics of standard single-robot Q-learning to ascertain whether they retain viable learning characteristics despite the integration of individual learning into team behaviors

  • 94.
    Emami, Reza
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Ragusila, Victor
    Institute for Aerospace Studies, University of Toronto.
    Mechatronics by analogy and application to legged locomotion2016In: Mechatronics (Oxford), ISSN 0957-4158, E-ISSN 1873-4006, Vol. 35, 173-191 p.Article in journal (Refereed)
    Abstract [en]

    A new design methodology for mechatronic systems, dubbed as Mechatronics by Analogy (MbA), is introduced. It argues that by establishing a similarity relation between a complex system and a number of simpler models it is possible to design the former using the analysis and synthesis means developed for the latter. The methodology provides a framework for concurrent engineering of complex systems while maintaining the transparency of the system behavior through making formal analogies between the system and those with more tractable dynamics. The application of the MbA methodology to the design of a monopod robot leg, called the Linkage Leg, is also presented. A series of simulations show that the dynamic behavior of the Linkage Leg is similar to that of a combination of a double pendulum and a spring-loaded inverted pendulum, based on which the system kinematic, dynamic, and control parameters can be designed concurrently.

  • 95.
    Emami, Reza
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Institute for Aerospace Studies, University of Toronto.
    Tedesco, Michael Anthony
    Space Mechatronics Group, University of Toronto, Toronto.
    System, method and computer program for remotely testing system components over a networkPatent (Other (popular science, discussion, etc.))
    Abstract [en]

    The invention is a turn-key, modular platform, including software and hardware, for testing physical system components such as motors remotely over the Internet. The system allows remote customers to test multiple physical system components under the specific loading conditions of the real-world application. This will provide more detailed and accurate information than what is usually given in the data sheets for system component performance, enabling the user to make a more-reliable decision. With respect to motors, the hardware consists of a torque motor that moves autonomously in xy plane to couple to the individual test motors, through a unique coupling mechanism, and emulate various load profiles on them. Test motors are mounted onto modular fixtures that allow for one-time manual positioning in xyz space. The software, consisting of server and target applications, creates user accounts and profiles, controls user access by means of a scheduler, and enables each user to connect to the hardware via Internet and run a customized experiment.

  • 96.
    Engeln, Axel von
    et al.
    Universität Bremen, Institute of Environmental Physics.
    Teixeira, Joao
    UCAR/VSP at Marine meteorology division of Naval research laboratory, Monterey, CA.
    Wickert, Jens
    GeoForschungsZentrum Potsdam, Department of Geodesy and Remote Sensing, Potsdam.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    CHAMP radio occultation detection of the planetary boundary layer top2006In: Atmosphere and climate: studies by occultation methods, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 2006Chapter in book (Other academic)
  • 97.
    Engeln, Axel von
    et al.
    Meteorological Division, European Organization for the Exploitation of Meteorological Satellites, Darmstadt.
    Teixeira, Joao
    NATO Undersea Research Centre, La Spezia.
    Wickert, Jens
    GeoForschungsZentrum Potsdam.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Comment on "Monitoring the atmospheric boundary layer by GPS radio occultation signals recorded in the open-loop mode" by S. Sokolovskiy et al.2007In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 34, no 2, L02806- p.Article in journal (Other academic)
  • 98.
    Enmark, Anita
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Andersen, Torben
    Lund Observatory.
    Owner-Petersen, Mette
    Lund Observatory.
    Chakraborty, Rijuparna
    Collège de France.
    Labeyrie, Antoine
    Collège de France.
    Integrated model of the Carlina Telescope2011In: Symposium on Integrated Modeling of Complex Optomechanical Systems: 15-17 August 2011, Kiruna, Sweden / [ed] Torben Andersen; Anita Enmark, 2011Conference paper (Refereed)
    Abstract [en]

    The Carlina hypertelescope is a planned sparse aperture 100 m telescope with pupil densification. The telescope has a spherical primary with segments located in a valley between mountains, and additional optical elements in a gondola suspended in eight cables some 100 m above the primary mirror. The resolution is about 1.2×10-3 arcsec. It is imperative that the position and attitude of the gondola be maintained within tight tolerances during observation and star tracking. The present design has servo-controlled winches on the ground for control of the gondola via the cables. An integrated model of the system, including optics, cables, gondola, position and attitude control system, and wind disturbances has been set up. The structural and control models are linear. Calculations in the frequency domain and simulations in the time domain show that the performance of the telescope with the present design seems adequate for short exposures. However, for long-exposure operation, the gondola stability should be improved by about two orders of magnitude. Recommendations are given on possible approaches for performance improvement.

  • 99.
    Eriksson, P.
    et al.
    Chalmers University of Technology.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Davis, C.P.
    Meteorological Service of New Zealand.
    Emde, C.
    Meteorological Institute, Ludwig-Maximilians-Universität, Munchen.
    Lemke, Oliver
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    ARTS, the atmospheric radiative transfer simulator, version 22011In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 112, no 10, 1551-1558 p.Article in journal (Refereed)
    Abstract [en]

    The second version of the atmospheric radiative transfer simulator, ARTS, is introduced. This is a general software package for long wavelength radiative transfer simulations, with a focus on passive microwave observations. The core part provides a workspace environment, in line with script languages. New for this version is an agenda mechanism that gives a high degree of modularity. The framework is intended to be as general as possible: the polarisation state can be fully described, the model atmosphere can be one- (1D), two- (2D) or three-dimensional (3D), a full description of geoid and surface is possible, observation geometries from the ground, from satellite, and from aeroplane or balloon are handled, and surface reflection can be treated in simple or complex manners. Remote sensing applications are supported by a comprehensive and efficient treatment of sensor characteristics. Jacobians can be calculated for the most important atmospheric variables in non-scattering conditions. Finally, the most prominent feature is the rigorous treatment of scattering that has been implemented in two modules: a discrete ordinate iterative approach mainly used for 1D atmospheres, and a Monte Carlo approach which is the preferred algorithm for 3D atmospheres. ARTS is freely available, and maintained as an open-source project.

  • 100.
    Eriksson, Patrick E J
    et al.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Jamali, Maryam
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Mendrok, Jana
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Buehler, Stefan
    Meteorological Institute, Center for Earth System Research and Sustainability, University of Hamburg.
    On the microwave optical properties of randomly oriented ice hydrometeors2015In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 8, no 5, 1913-1933 p.Article in journal (Refereed)
    Abstract [en]

    Microwave remote sensing is important for observing the mass of ice hydrometeors. One of the main error sources of microwave ice mass retrievals is that approximations around the shape of the particles are unavoidable. One common approach to represent particles of irregular shape is the soft particle approximation (SPA). We show that it is possible to define a SPA that mimics mean optical particles of available reference data over narrow frequency ranges, considering a single observation technique at the time, but that SPA does not work in a broader context. Most critically, the required air fraction varies with frequency and application, as well as with particle size. In addition, the air fraction matching established density parameterisations results in far too soft particles, at least for frequencies above 90 GHz. That is, alternatives to SPA must be found. One alternative was recently presented by Geer and Baordo (2014). They used a subset of the same reference data and simply selected as "shape model" the particle type giving the best overall agreement with observations. We present a way to perform the same selection of a representative particle shape but without involving assumptions on particle size distribution and actual ice mass contents. Only an assumption on the occurrence frequency of different particle shapes is still required. Our analysis leads to the same selection of representative shape as found by Geer and Baordo (2014). In addition, we show that the selected particle shape has the desired properties at higher frequencies as well as for radar applications. Finally, we demonstrate that in this context the assumption on particle shape is likely less critical when using mass equivalent diameter to characterise particle size compared to using maximum dimension, but a better understanding of the variability of size distributions is required to fully characterise the advantage. Further advancements on these subjects are presently difficult to achieve due to a lack of reference data. One main problem is that most available databases of precalculated optical properties assume completely random particle orientation, while for certain conditions a horizontal alignment is expected. In addition, the only database covering frequencies above 340 GHz has a poor representation of absorption as it is based on outdated refractive index data as well as only covering particles having a maximum dimension below 2 mm and a single temperature

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