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  • 51.
    Brett, Christopher
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Control System Design for an Orbital Inspection Vehicle and Servicing Satellite Using Thrust-Vectoring Cold-Gas Propulsion2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This Thesis presents the work leading to the design of a closed loop control system for a prototype six-degree-of-freedom orbital inspection vehicle named Cerberus. Each of Cerberus' three compressed Nitrogen gas thrusters can be rotated about their elevation and azimuth axes, providing a thrust-vectored control capability. In order to test this capability in a simulated space environment Cerberus is mounted on the DAWN six-degree-of-freedom air-bearing vehicle. The control schemes presented in this thesis allow joystick control, station-keeping at a set distance from a moving target and inspection fly-around manoeuvres to be conducted before a docking procedure is initiated with a non-cooperative client vehicle. The following Thesis describes the decision-making process used to select the appropriate control scheme for each control mode, with the purpose of providing accurate position control for the module.

  • 52.
    Brolies, Thomas W.
    et al.
    Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Burch, James L.
    Southwest Research Institute, 6220 Culebra Road, San Antonio, Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Clark, Grace A.
    Heliophysics Division, Goddard Space Flight Center.
    Koenders, Christoph
    Institut für Geophysik und Extraterrestrische Physik, Technische Universität Braunschweig.
    Behar, Etienne
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Goldstein, Raymond M.
    Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Fuselier, Stephen Anthony
    Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Mandt, Kathleen E.
    Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Mokashi, Prachet
    Southwest Research Institute, 6220 Culebra Road, San Antonio, Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Samara, M.
    Heliophysics Division, Goddard Space Flight Center.
    Rosetta observations of solar wind interaction with the comet 67P/Churyumov-Gerasimenko2015Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 583, artikkel-id A21Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Context. The Rosetta spacecraft arrived at the comet 67P/Churyumov-Gerasimenko on August 6, 2014, which has made it possible to perform the first study of the solar wind interacting with the coma of a weakly outgassing comet. Aims. It is shown that the solar wind experiences large deflections (>45°) in the weak coma. The average ion velocity slows from the mass loading of newborn cometary ions, which also slows the interplanetary magnetic field (IMF) relative to the solar wind ions and subsequently creates a Lorentz force in the frame of the solar wind. The Lorentz force in the solar wind frame accelerates ions in the opposite direction of cometary pickup ion flow, and is necessary to conserve momentum. Methods. Data from the Ion and Electron Sensor are studied over several intervals of interest when significant solar wind deflection was observed. The deflections for protons and for He++ were compared with the flow of cometary pickup ions using the instrument's frame of reference. We then fit the data with a three-dimensional Maxwellian, and rotated the flow vectors into the Comet Sun Equatorial coordinate system, and compared the flow to the spacecraft's position and to the local IMF conditions. Results. Our observations show that the solar wind may be deflected in excess of 45° from the anti-sunward direction. Furthermore, the deflections change direction on a variable timescale. Solar wind protons are consistently more deflected than the He++. The deflections are not ordered by the spacecraft's position relative to the comet, but large changes in deflection are related to changes in the orthogonal IMF components

  • 53.
    Browne Mwakyanjala, Moses
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Beek, Jaap van de
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Software-defined radio transceiver for QB50 CubeSat telemetry and telecommand2016Inngår i: Proceedings of the 34th AIAA International Communications Satellite Systems Conference (ICSSC 2016), American Institute of Aeronautics and Astronautics, 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents the development of a ground system based on software-defined radio for supporting both ground testing and space telemetry and telecommand of one of the nanosatellites in the QB50 mission. The QB50 project is an ongoing European Commission Seventh Framework initiative, which aims at launching a constellation of 50 CubeSats in the lower thermosphere to carry out in-situ scientific measurements. The paper discusses the implementation of amateur radio protocols and telecommunication modulation schemes on the ground system. The system setup, deployment and scheduling are also discussed using two separate ground stations. The use of different software for testing the system is detailed, the results show the operability of the developed ground system. © 2016, American Institute of Aeronautics and Astronautics Inc

  • 54.
    Browne Mwakyanjala, Moses
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Institute for Aerospace Studies, University of Toronto.
    Beek, Jaap van de
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Verification of phase and frequency modulation for software-defined radio baseband systems using field data2017Inngår i: 35th AIAA International Communications Satellite Systems Conference, ICSSC 2017, American Institute of Aeronautics and Astronautics, 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents the verification of phase and frequency modulation schemes for a software-defined radio baseband system that is being prototyped to support satellite telemetry, telecommand and ranging. It presents the theory behind the two modulation schemes, implementation and verification against emulated signals from a space-qualified hardware-based baseband system as well as from the Odin satellite.

  • 55.
    Browne Mwakyanjala, Moses
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    van de Beek, Jaap
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Verication of phase and frequency modulation for software-defined radio baseband systems using field data2017Konferansepaper (Fagfellevurdert)
  • 56.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Atmospheric radiative-transfer simulator2006Inngår i: Thermal Microwave Radiation: Applications for Remote Sensing, London: Institution of Engineering and Technology, 2006, s. 54-56Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 57.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    UTH-MOS: Wasserdampf und Cirren in der oberen Troposphäre aus operationellen meteorologischen Satellitendaten2006Rapport (Annet vitenskapelig)
  • 58.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Courcoux, N.
    Universität Bremen, Institute of Environmental Physics.
    John, Viju Oommen
    University of Miami, Rosenstiel School of Marine and Atmospheric Sciences, Miami.
    Radiative transfer calculations for a passive microwave satellite sensor: comparing a fast model and a line-by-line model2006Inngår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 111, nr 20, s. 20304-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    [1] A comparison between the fast radiative transfer model Radiative Transfer for the TIROS Operational Vertical Sounder (RTTOV-7) and the physical radiative transfer model Atmospheric Radiative Transfer Simulator ( ARTS) was carried out. Radiances were simulated for the sounding channels of the Advanced Microwave Sounding Unit B (AMSU-B) for the whole globe for a single time of a single day ( 1 January 2000, 0000 UT). Temperature, pressure, and specific humidity profiles from the reanalysis data set ERA-40 of the European Centre for Medium-Range Weather Forecasts (ECMWF) were used as input for both models; geopotential height profiles were also used but only as input for ARTS. The simulations were made for two different surface emissivities, 0.60 and 0.95. The low surface emissivity case exhibits the larger radiance differences. Although the global values of the mean difference and standard deviation are small ( for example, the global mean difference for channel 18 is 0.014 K and the standard deviation is 0.232 K), the examination of the geographical distribution of the differences shows that large positive or negative values are observed over dry regions of high northern and southern latitudes and over dry elevated regions. The origin of these differences was found to be due to errors introduced by the transmittance parametrization used in RTTOV.

  • 59.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Defer, E.
    CNRS, Laboratoire d'Etudes du Rayonnement et de la Matière en Astrophysique, Observatoire de Paris.
    Evans, F.
    Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder.
    Eliasson, Salomon
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mendrok, Jana
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Erikssson, P.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Lee, C.
    Met Office Hadley Centre, Exeter.
    Jimenez, C.
    CNRS, Laboratoire d'Etudes du Rayonnement et de la Matière en Astrophysique, Observatoire de Paris.
    Prigent, C.
    CNRS, Laboratoire d'Etudes du Rayonnement et de la Matière en Astrophysique, Observatoire de Paris.
    Crewell, S.
    Institute for Geophysics and Meteorology, University of Cologne.
    kasai, Y.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Bennartz, R.
    Atmospheric and Oceanic Sciences, University of Wisconsin.
    Gasiewski, A.J.
    NOAA-CU Center for Environmental Technology (CET), Department of Electrical and Computer Engineering, University of Colorado at Boulder.
    Observing ice clouds in the submillimeter spectral range: the CloudIce mission proposal for ESA's Earth Explorer 82012Inngår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 5, nr 7, s. 1529-1549Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Passive submillimeter-wave sensors are a way to obtain urgently needed global data on ice clouds, particularly on the so far poorly characterized 'essential climate variable' ice water path (IWP) and on ice particle size. CloudIce was a mission proposal to the European Space Agency ESA in response to the call for Earth Explorer 8 (EE8), which ran in 2009/2010. It proposed a passive submillimeter-wave sensor with channels ranging from 183 GHz to 664 GHz. The article describes the CloudIce mission proposal, with particular emphasis on describing the algorithms for the data-analysis of submillimeter-wave cloud ice data (retrieval algorithms) and demonstrating their maturity. It is shown that we have a robust understanding of the radiative properties of cloud ice in the millimeter/submillimeter spectral range, and that we have a proven toolbox of retrieval algorithms to work with these data. Although the mission was not selected for EE8, the concept will be useful as a reference for other future mission proposals.

  • 60.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Lemke, Oliver
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Absorption lookup tables in the radiative transfer model ARTS2011Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 112, nr 10, s. 1559-1567Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We describe the lookup table approach that is used to store pre-calculated absorption data in the radiative transfer model ARTS. The table stores absorption cross sections as a function of frequency, pressure, temperature, and the water vapor volume mixing ratio, where the last dimension is only included for those gas species that require it. The table is used together with an extraction strategy, which uses polynomial interpolation, with recommended interpolation orders between five and seven. We also derived recommended default settings for grid spacings and interpolation orders, and verified that the approach gives very accurate results with these default settings. The tested instrument setups were for AMSU-B, HIRS, and Odin, three well-known satellite remote sensing instruments covering a wide range of frequencies and viewing geometries. Errors introduced by the lookup table were found to be always below a few millikelvin, in terms of the simulated brightness temperature.

  • 61.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Jimenez, C.
    Evans, K. F.
    Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder.
    Eriksson, P.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Rydberg, B.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Heymsfield, A.
    NCAR, Boulder, Colorado.
    Stubenrauch, C.
    CNRS/IPSL - Laboratoire de Meteorologie Dynamique, Ecole Polytechnique, Palaiseau.
    Lohmann, U.
    ETH Zurich, Institute for Atmospheric and Climate Science.
    Emde, C.
    Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen.
    John, V. O.
    Met Office Hadley Centre, Exeter.
    Sreerekha, T. R.
    Met Office Hadley Centre, Exeter.
    Davis, C. P.
    School of Geosciences, University of Edinburgh.
    A concept for a satellite mission to measure cloud ice water path, ice particle size, and cloud altitude2007Inngår i: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 133, nr Suppl.2, s. 109-128Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A passive satellite radiometer operating at submillimetre wavelengths can measure cloud ice water path (IWP), ice particle size, and cloud altitude. The paper first discusses the scientific background for such measurements. Formal scientific mission requirements are derived, based on this background and earlier assessments. The paper then presents a comprehensive prototype instrument and mission concept, and demonstrates that it meets the requirements. The instrument is a conically scanning 12-channel radiometer with channels between 183 and 664 GHz, proposed to fly in tandem with one of the Metop satellites. It can measure IWP with a relative accuracy of approximately 20% and a detection threshold of approximately 2 g m-2. The median mass equivalent sphere diameter of the ice particles can be measured with an accuracy of approximately 30 µm, and the median IWP cloud altitude can be measured with an accuracy of approximately 300 m. All the above accuracies are median absolute error values; root mean square error values are approximately twice as high, due to rare outliers.

  • 62.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    John, V.O.
    Met Office Hadley Centre, Exeter.
    Kottayil, Ajil
    Milz, Mathias
    Eriksson, P.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Efficient radiative transfer simulations for a broadband infrared radiometer: combining a weighted mean of representative frequencies approach with frequency selection by simulated annealing2010Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 111, nr 4, s. 602-615Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a method to efficiently simulate the measurements of a broadband infrared instrument. The High Resolution Infrared Radiation Sounder (HIRS) instrument is used as example to illustrate the method. The method uses two basic ideas. Firstly, the channel radiance can be approximated by a weighted mean of the radiance at some representative frequencies, where the weights can be determined by linear regression. Secondly, a near-optimal set of representative frequencies can be found by simulated annealing.The paper does not only describe and analyze the method, it also describes how the method was used to derive optimized frequency grids for the HIRS instruments on the satellites TIROS N, NOAA 6-19, and Metop A. The grids and weights, as well as the optimization algorithm itself are openly available under a GNU public license.

  • 63.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Kuhn, Thomas
    Universität Bremen, Institute of Environmental Physics.
    Bauer, Agnes
    Institute of Environmental Physics, University of Bremen.
    Corrigendum to 'Water vapor continuum: Absorption measurements at 350 GHz and model calculations' [JQSRT 2002;74:545-62]2008Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 109, nr 9, s. 1743-1744Artikkel i tidsskrift (Annet vitenskapelig)
  • 64.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Kuvatov, M.
    Institut für Umweltphysik (Institute for Environmental Physics) (IUP), University of Bremen.
    John, V. O.
    Meteorology and Physical Oceanography, Rosenstiel School for Marine and Atmospheric Science (RSMAS), University of Miami.
    Milz, Mathias
    Soden, B.J.
    Meteorology and Physical Oceanography, Rosenstiel School for Marine and Atmospheric Science (RSMAS), University of Miami.
    Jackson, D.L.
    Cooperative Institute for Research in Environmental Science (CIRES), University of Colorado, NOAA Earth System Research Laboratory.
    Norholt, J.
    Institut für Umweltphysik (Institute for Environmental Physics) (IUP), University of Bremen.
    An upper tropospheric humidity data set from operational satellite microwave data2008Inngår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 113, nr 14, s. D14110-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    183.31 GHz observations from the Advanced Microwave Sounding Unit B (AMSUB) instruments onboard the NOAA 15, 16, and 17 satellites were used to derive a new data set of Upper Tropospheric Humidity (UTH). The data set consist of monthly median and mean data on a 1.5 degrees latitude-longitude grid between 60 degrees S and 60 degrees N, and covers the time period of January 2000 to February 2007. The data from all three instruments are very consistent, with relative difference biases of less than 4% and relative difference standard deviations of 7%. Radiometric contributions by high ice clouds and by the Earth's surface affect the measurements in certain areas. The uncertainty due to clouds is estimated to be up to approximately 10%RH in areas with deep convection. The uncertainty associated with contamination from surface emission can exceed 10%RH in midlatitude winter, where the data therefore should be regarded with caution. Otherwise the surface influence appears negligible. The paper also discusses the UTH median climatology and seasonal cycle, which are found to be broadly consistent with UTH climatologies from other sensors. Finally, the paper presents an initial validation of the new data set against IR satellite data and radiosonde data. The observed biases of up to 9%RH (wet bias relative to HIRS) were found to be broadly consistent with expectations based on earlier studies. The observed standard deviations against all other data sets were below 6%RH. The UTH data are available to the scientific community on http://www.sat.ltu.se.

  • 65.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Kuvatov, Mashrab
    IUP, University of Bremen.
    Sreerekha, T. R.
    UK Met Office, Exeter.
    John, Viju Oommen
    RSMAS, University of Miami.
    Rydberg, Bengt
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Notholt, Justus
    IUP, University of Bremen.
    A cloud filtering method for microwave upper tropospheric humidity measurements2007Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 7, nr 21, s. 5531-5542Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The paper presents a cloud filtering method for upper tropospheric humidity (UTH) measurements at 183.31±1.00 GHz. The method uses two criteria: a viewing angle dependent threshold on the brightness temperature at 183.31±1.00 GHz, and a threshold on the brightness temperature difference between another channel and 183.31±1.00 GHz. Two different alternatives, using 183.31±3.00 GHz or 183.31±7.00 GHz as the other channel, are studied. The robustness of this cloud filtering method is demonstrated by a mid-latitudes winter case study. The paper then studies different biases on UTH climatologies. Clouds are associated with high humidity, therefore the possible dry bias introduced by cloud filtering is discussed and compared to the wet biases introduced by the clouds radiative effect if no filtering is done. This is done by means of a case study, and by means of a stochastic cloud database with representative statistics for midlatitude conditions. Both studied filter alternatives perform nearly equally well, but the alternative using 183.31±3.00 GHz as other channel is preferable, because that channel is less likely to see the Earth's surface than the one at 183.31±7.00 GHz. The consistent result of all case studies and for both filter alternatives is that both cloud wet bias and cloud filtering dry bias are modest for microwave data. The recommended strategy is to use the cloud filtered data as an estimate for the true all-sky UTH value, but retain the unfiltered data to have an estimate of the cloud induced uncertainty. The focus of the paper is on midlatitude data, since atmospheric data to test the filter for that case were readily available. The filter is expected to be applicable also to subtropical and tropical data, but should be further validated with case studies similar to the one presented here for those cases.

  • 66.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Milz, Mathias
    Eliasson, Salomon
    Upper tropospheric humidity and cloud ice: comparing global climate models and satellite observations2008Inngår i: 2008 European Geosciences Union General Assembly, Austria Center Vienna, Vienna (Austria), 13-18 Apr 2008, European Geosciences Union (EGU), 2008Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Upper tropospheric humidity (UTH) and cloud ice (measured as ice water content IWC or vertically integrated ice water path IWP) are parameters of the climate system on which current global climate models do not agree well. This is illustrated by intercomparing the models in the IPCC AR4 archive. It is then discussed, to what extent different satellite measurements agree on these parameters. The focus is on passive observations from different infrared (HIRS, IASI) and microwave (AMSU-B, HSB) sensors.

  • 67.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Östman, S.
    Luleå tekniska universitet.
    Melsheimer, C.
    Institute of Environmental Physics, University of Bremen.
    Holl, Gerrit
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Eliasson, Salomon
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    John, V.O.
    Met Office Hadley Centre, Exeter.
    Blumenstock, T.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Hase, F.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Ekgered, G.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Raffalski, U.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Nasuno, T.
    Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, Yokohama.
    Satho, M.
    Atmosphere and Ocean Research Institute, University of Tokyo.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mendrok, Jana
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A multi-instrument comparison of integrated water vapour measurements at a high latitude site2012Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 12, nr 22, s. 10925-10943Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We compare measurements of integrated water vapour (IWV) over a subarctic site (Kiruna, Northern Sweden) from five different sensors and retrieval methods: Radiosondes, Global Positioning System (GPS), ground-based Fourier-transform infrared (FTIR) spectrometer, ground-based microwave radiometer, and satellite-based microwave radiometer (AMSU-B). Additionally, we compare also to ERA-Interim model reanalysis data. GPS-based IWV data have the highest temporal coverage and resolution and are chosen as reference data set. All datasets agree reasonably well, but the ground-based microwave instrument only if the data are cloud-filtered. We also address two issues that are general for such intercomparison studies, the impact of different lower altitude limits for the IWV integration, and the impact of representativeness error. We develop methods for correcting for the former, and estimating the random error contribution of the latter. A literature survey reveals that reported systematic differences between different techniques are study-dependent and show no overall consistent pattern. Further improving the absolute accuracy of IWV measurements and providing climate-quality time series therefore remain challenging problems.

  • 68.
    Carlsson, Ella
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Cold Mars2006Konferansepaper (Annet vitenskapelig)
  • 69. 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 tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    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 beams2008Inngår i: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 56, nr 6, s. 861-867Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 70. Carlsson, Ella
    et al.
    Fedorov, A.
    Budnik, E.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Fredriksson, Sverker
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    First results from ASPERA-3 Ion Mass Analyzer (IMA) on CO2+ escape2005Konferansepaper (Annet vitenskapelig)
  • 71.
    Castro, Juan Francisco Buenestado
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mier, Maria-Paz Zorzano
    Centro de Astrobiologia, INTA-CSIC, Madrid.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Liquid water at crater Gale, Mars2015Inngår i: Journal of Astrobiology and Outreach, ISSN 2332-2519, Vol. 3, nr 3, artikkel-id 131Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 72.
    Castro, Juan Francisco Buenestado
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mier, Maria-Paz Zorzano
    Centro de Astrobiologia, INTA-CSIC, Madrid.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Planetary exploration; Mars on the scope2015Inngår i: Journal of Astrobiology and Outreach, ISSN 2332-2519, Vol. 3, nr 3, artikkel-id 133Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 73.
    Charlton, J E
    et al.
    Sula systems.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    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 clouds2010Inngår i: International Geoscience and Remote Sensing Symposium (IGARSS): Cape Town, South Africa, 12 - 17 July 2009, Piscataway, NJ: IEEE Communications Society, 2010, Vol. 3, s. 1023-1026Konferansepaper (Fagfellevurdert)
    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).

  • 74.
    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 tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    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 MLS2009Inngår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, nr 2, s. 337-353Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 75.
    Chen, Fengxiang
    et al.
    Department of Automation, Shanghai Jiaotong University.
    Chen, Lin
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zhang, Weidong
    Department of Automation, Shanghai Jiaotong University.
    Robust control of chaos in the Lorenz system with the variable structure control approach2008Inngår i: Physica scripta. T, ISSN 0281-1847, Vol. 77, nr 2Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    This paper is concerned with the robust control for a class of the uncertain Lorenz system subject to sector nonlinear input. Based on rigorous mathematical analysis, the proposed variable structure controller can drive the system state exactly to a class of a specific point or in the predictable neighborhood of an arbitrary desired point in the state space even with mismatch uncertainties. Moreover, the controller ensures that one of the error components can approach zero as time approaches infinity. Finally, numerical simulation results show the effectiveness of our work.

  • 76.
    Chen, Fengxiang
    et al.
    Department of Automation, Shanghai Jiaotong University.
    Chen, Lin
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zhang, Weidong
    Department of Automation, Shanghai Jiaotong University.
    Stabilization of parameters perturbation chaotic system via adaptive backstepping technique2008Inngår i: Applied Mathematics and Computation, ISSN 0096-3003, E-ISSN 1873-5649, Vol. 200, nr 1, s. 101-109Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The work of Yassen [M.T. Yassen, Chaos control of chaotic dynamical systems using backstepping design, Chaos Soliton Fract. 27 (2006) 537-548] which mainly investigated the stabilization problem for a class of chaotic systems without the parameters perturbation. This paper is concerned with stabilization problem for a class of parameters perturbation chaotic systems via both backstepping design method and adaptive technique. The proposed controllers can guarantee that the parameters perturbation systems will be stabilized at a fixed bounded point. Furthermore, the paper also proposes controllers to stabilize the uncertain chaotic system at equilibrium point with only backstepping design method. Finally, numerical simulations are given to illustrate the effectiveness of the proposed controllers

  • 77.
    Chen, Fengxiang
    et al.
    Shanghai Jiao Tong University.
    Wang, Wei
    Shanghai Jiao Tong University.
    Chen, Lin
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zhang, Weidong
    Shanghai Jiao Tong University.
    Adaptive chaos synchronization based on LMI technique2007Inngår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 75, nr 3, s. 285-288Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The paper investigates the robust synchronization for two identical uncertain chaotic systems with different parameters perturbation and external disturbances. Based on Lyapunov stability theory, linear matrix inequality (LMI) techniques and adaptive techniques, a novel controller is proposed. With the resulting controller, global asymptotical synchronization between two identical uncertain chaotic systems is achieved. Finally, a Lorenz system is given as an example to verify the effectiveness of the proposed controller.

  • 78.
    Chhabra, Robin
    et al.
    Department of Mathematics and Statistics, University of Calgary.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A linguistic approach to concurrent design2015Inngår i: Journal of Intelligent & Fuzzy Systems, ISSN 1064-1246, E-ISSN 1875-8967, Vol. 28, nr 5, s. 1985-2001Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 79.
    Chhabra, Robin
    et al.
    MacDonald, Dettwiler and Associates Ltd., Brampton.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A Unified Approach to Input-output Linearization and Concurrent Control of Underactuated Open-chain Multi-body Systems with Holonomic and Nonholonomic Constraints2016Inngår i: Journal of dynamical and control systems, ISSN 1079-2724, E-ISSN 1573-8698, Vol. 22, nr 1, s. 129-168Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 80.
    Chhabra, Robin
    et al.
    Institute for Aerospace Studies, University of Toronto, MacDonald, Dettwiler and Associates Ltd., Brampton.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Symplectic reduction of holonomic open-chain multi-body systems with constant momentum2015Inngår i: Journal of Geometry and Physics, ISSN 0393-0440, E-ISSN 1879-1662, Vol. 89, s. 82-110Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 81.
    Chhabra, Robin
    et al.
    MacDonald, Dettwiler and Ass. Ltd.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Karshon, Yael
    Department of Mathematics, University of Toronto.
    Reduction of Hamiltonian Mechanical Systems With Affine Constraints: A Geometric Unification2017Inngår i: Journal of Computational and Nonlinear Dynamics, ISSN 1555-1415, E-ISSN 1555-1423, Vol. 12, nr 2, artikkel-id 021007Artikkel i tidsskrift (Fagfellevurdert)
    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

  • 82.
    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 tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    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 20032007Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 7, nr 22, s. 5861-5872Artikkel i tidsskrift (Fagfellevurdert)
    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

  • 83.
    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 tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    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 tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Habitability: a review2016Inngår i: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 16, nr 1, s. 89-117Artikkel i tidsskrift (Fagfellevurdert)
    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

  • 84.
    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 tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    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) mission2016Inngår i: AIAA Space and Astronautics Forum and Exposition, SPACE 2016, American Institute of Aeronautics and Astronautics, 2016Konferansepaper (Fagfellevurdert)
    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

  • 85.
    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 tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    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 moons2017Inngår i: Acta Astronautica, ISSN 0094-5765, E-ISSN 1879-2030, Vol. 139, s. 545-563Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 86.
    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 tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    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 study2006Inngår i: Atmospheric Chemistry and Physics Discussions, ISSN 1680-7367, E-ISSN 1680-7375, Vol. 6, s. 12701-12728Artikkel i tidsskrift (Annet vitenskapelig)
  • 87.
    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 tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    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 study2007Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 7, nr 15, s. 4149-4158Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 88.
    Delgado-Bonal, A.
    et al.
    Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR).
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Human vision is determined based on information theory2016Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, artikkel-id 36038Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 89.
    Delgado-Bonal, Alfonso
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Evaluation of the Atmospheric Chemical Entropy Production of Mars2015Inngår i: Entropy, ISSN 1099-4300, E-ISSN 1099-4300, Vol. 17, nr 7, s. 5047-5062Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 90.
    Delgado-Bonal, Alfonso
    et al.
    Centro de Astrobiologia, INTA-CSIC, Madrid.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Solar cell temperature on Mars2015Inngår i: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 118, s. 74-79Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 91.
    Delgado-Bonal, Alfonso
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Martín, Sandra Vázquez
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mier, Maria-Paz Zorzano
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Solar and wind exergy potentials for Mars2016Inngår i: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 102, s. 550-558Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 92.
    Delgado-Bonal, Alfonso
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mier, Maria-Paz Zorzano
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Martian Top of the Atmosphere 10–420 nm spectral irradiance database and forecast for solar cycle 242016Inngår i: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 134, s. 228-235Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 93.
    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 tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Holmström, M.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    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 flow2013Inngår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 40, nr 2, s. 2913-2917Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 94.
    Dieval, Catherine
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Solar wind ions inside the induced magnetosphere of Mars2012Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The subject of the thesis is analysis and modeling of the entry, transport, and atmospheric precipitation of solar wind ions, H+ and He2+, into the induced magnetosphere of Mars. The solar wind is a flow of charged particles emitted by the Sun. The solar wind carries with it a magnetic field, the interplanetary magnetic field (IMF). The IMF piles up on the dayside of the non-magnetized Mars and is then convected towards the nightside. The solar wind ions can normally not cross the magnetic barrier, formed by the pile up IMF. However, in situ observations by the Mars Express spacecraft reveal that downward moving solar wind H+ and He2+ are sometimes present in the Martian ionosphere, below the magnetic barrier. The gyroradii of shocked solar wind ions may be comparable to the size of the dayside Martian magnetic barrier and for certain circumstances, these ions can gyrate through. Observations by Mars Express are used to analyze H+ and He2+ penetrating through the magnetic barrier and precipitating into the Martian ionosphere, identified by the presence of ionospheric photo-electrons. A case study shows evidence of narrower energy distributions for H+ (with energy ≥ solar wind energy), as the spacecraft moves down in altitude. From this, the study concludes that the magnetic barrier prevents the lower energy H+, from reaching low altitudes. The thesis also describes a statistical study of precipitating H+ fluxes, which indicate that H+ precipitation is rare (detected during 3% of the dayside observation time only) and carries on average 0.2% of the upstream solar wind particle flux. In another statistical study, the thesis shows that the precipitation of H+ and He2+ decreases even further when Mars encounters solar wind pressure pulses. A possible explanation is that the enhanced mass loading of the magnetic field flux tubes by planetary heavy ions, while the tubes drag through the ionosphere at lower altitudes, slows down their velocity and allows more magnetic flux to pile up. The magnetic barrier becomes a more effective obstacle to the solar wind ion precipitation. Furthermore, the thesis describes a model of H+ precipitation onto the Martian upper atmosphere using a hybrid code of the Mars solar wind interaction. The spatial patterns of the precipitation depend on the H+ energy, on the H+ origin (solar wind or generated from the hydrogen corona) and on the altitude. Some features of the observed H+ distributions are reproduced by simulations, while others are not, indicating a more complex physics than in the model. The thesis also describes amodel study of transport of H+, fast H atoms and He2+ through the atmosphere using a Direct Simulation Monte Carlo model. This study demonstrates the crucial role of the magnetic field in determining the energy deposition of the solar wind ions in the topside atmosphere. For instance, a horizontal magnetic field with strength of 50 nT backscattered almost all H+, thus preventing these particles to deposit their energy at lower altitudes. The conclusion of the thesis work is that although some solar wind ions do precipitate, the magnetic barrier effectively protects the onospherefrom precipitating solar wind ions.

  • 95.
    Dieval, Catherine
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    The solar wind protons inside the induced magnetosphere of Mars2011Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Mars is an unmagnetized planet. Mars has no intrinsic magnetic field but has local magnetic anomalies in the crust. The solar wind, which is the plasma flowing from the Sun at supersonic speed, interacts with the magnetic fields of the currents induced in the conductive Martian ionosphere, deviates and slows down to subsonic speeds. A void in the solar wind is formed around the planet as an induced magnetosphere.At the boundary of the induced magnetosphere, the plasma composition changes from being dominated by the major ion in the solar wind (protons) to being dominated by heavy ions of planetary origin. Also, the interplanetary magnetic field, being carried by the solar wind, starts to pile up against the planet to form a magnetic barrier on the dayside, drapes around the planet, stretches due to mass loading, and forms a magnetotail.The gyroradius of a heated proton in the magnetosheath is large in comparison with the size of the induced magnetosphere. Therefore, a fraction of the proton population penetrates the induced magnetosphere boundary, enters the upper layer of the atmosphere (the ionosphere) and subsequently neutralizes at low altitudes. We have conducted a detailed study of an event, in which the magnetosheath protons penetrate the Martian induced magnetosphere boundary (IMB). The spatial extent of the proton precipitation region reached several thousands of kilometers along the orbit of the Mars Express spacecraft.The interaction of the precipitating protons with the Martian atmosphere was modeled using a direct simulation Monte Carlo method. The inclusion of a horizontal magnetic field in the model significantly increased the backscattering of protons compared to the case without a magnetic field. More than 50% of the incoming energy is reflected backwards for a magnetic field of strength 30 nT, compared to 4% in the case of no magnetic field. We have also used hybrid modeling to study the spatial pattern of the precipitation onto the Martian atmosphere both for solar wind protons and protons originating from the planetary atmosphere. The solar wind protons and the exospheric (planetary) protons contribute 60% and 40%, respectively, of the deposition of mass at the exobase for the given input parameters. The precipitating flux decreases substantially at the subsolar point, due to the backscattering of the incoming protons by the more intense piled-up magnetic field.

  • 96.
    Dieval, Catherine
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Kallio, E.
    Finnish Meteorological Institute.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    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 simulations2012Inngår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 97.
    Dieval, Catherine
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Stenberg, G.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Nilsson, H.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A statistical study of proton precipitation onto the Martian upper atmosphere: Mars Express observations2013Inngår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, s. 1972-1983Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 98.
    Dieval, Catherine
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Stenberg, G.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Edberg, N.J.T.
    Swedish Institute of Space Physics, Uppsala.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Reduced proton and alpha particle precipitations at Mars during solar wind pressure pulses: Mars Express results2013Inngår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 118, nr 6, s. 3421-3429Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 99.
    Dikmen, Serkan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Development of Star Tracker Attitude and Position Determination System for Spacecraft Maneuvering and Docking Facility2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    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. 

  • 100.
    Dillibabu, Surender
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Design,Analysis, and prototype of underwater glider2016Independent thesis Advanced level (degree of Master (Two Years)), 80 poäng / 120 hpOppgave
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  • modern-language-association-8th-edition
  • vancouver
  • Annet format
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Språk
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  • nn-NO
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Utmatningsformat
  • html
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  • asciidoc
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