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  • 251.
    Lanza, N.L.
    et al.
    Los Alamos National Laboratory.
    Wiens, R.C.
    Los Alamos National Laboratory.
    Arvidson, R.E.
    Washington University, St. Louis.
    Clark, B.C.
    Space Science Institute, Boulder, Colorado.
    Fischer, W.W.
    California Institute of Technology, Pasadena.
    Gellert, R.
    University of Guelph, Ontario.
    Grotzinger, J.P.
    California Institute of Technology, Pasadena.
    Hurowitz, J.A.
    Stony Brook University, NY.
    McLennan, S.M.
    Stony Brook University, NY.
    Morris, R.V.
    NASA Johnson Space Center, Houston.
    Rice, M.S.
    Western Washington University, Bellingham.
    III, J.F. Bell
    Arizona State University.
    Berger, J.A.
    University of Western Ontario, London.
    Blaney, D.L.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Blank, J.G.
    NASA Ames, Blue Marble Space Institute of Science, Seattle.
    Bridges, N.T.
    Johns Hopkins University Applied Physics Laboratory, Laurel.
    III, F. Calef
    Jet Propulsion Laboratory.
    Campbell, J.L.
    University of Guelph, Ontario.
    Clegg, S.M.
    Los Alamos National Laboratory.
    Cousin, A.
    Los Alamos National Laboratory.
    Edgett, K.S.
    Malin Space Science Systems.
    Fabre, C.
    Université de Lorraine, Nancy.
    Fisk, M.R.
    Oregon State University, Corvallis.
    Forni, O.
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Frydenvang, J.
    Niels Bohr Institute, University of Copenhagen.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Instituto Andaluz de Cienccias de la Tierra (CSIC-UGR), Grenada.
    Zorzano, M.-P.
    Instituto Nacional de Técnica Aeroespacial, Madrid.
    Oxidation of manganese at Kimberley, Gale Crater: More free oxygen in Mars’ past?2015Konferansepaper (Fagfellevurdert)
  • 252.
    Larsson, Richard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A note on modelling of the oxygen spectral cross-section in the Atmospheric Radiative Transfer Simulator – Zeeman effect combined with line mixing in the Earth’s atmosphere2014Inngår i: International Journal of Remote Sensing, ISSN 0143-1161, E-ISSN 1366-5901, Vol. 35, nr 15, s. 5845-5853Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new module to the Atmospheric Radiative Transfer Simulator is presented that models the strong oxygen spectral band at 60 GHz. The module handles the line mixing effect and works with or without additionally calculating the Zeeman effect. It is shown how the module may be internally reduced to calculations of the Zeeman effect at higher altitudes, and to calculations of the line mixing effect at lower altitudes. The article ends with a short discussion on what is being done to validate the module, and what may be done to refine the theoretical description of line mixing in the simulator.

  • 253.
    Larsson, Richard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Modeling the Zeeman Effect in Planetary Atmospheric Radiative Transfer2014Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    There are special effects in spectroscopy that must be considered in order to fullyexplain how molecular oxygen interacts with radiation in planetary atmospheres.One of these, the Zeeman effect, is described in this thesis. The Zeeman effect is the theory by which energy levels of atoms and molecules are altered by magnetism, and it causes both polarization and line shape to change. The first publication attached to this thesis, Paper I, details the technical and practical implementation of the Zeeman effect in a radiative transfer model. One potential use of magnetically altered spectroscopy is to remotely measure magnetism. Paper II discuss a method for such measurements on weakly magnetized planets by measuring the polarization caused by the Zeeman effect. The article brings up Mars as one potential candidate to utilize the method. To introduce the articles properly, the thesis starts with a shortdescription of the underlying basic theory for radiative transfer and spectroscopy.After the theory chapter, a short description of input necessary to utilize the theory on operational and experimental platforms is presented.

  • 254.
    Larsson, Richard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Modeling the Zeeman Effect in Planetary Radiative Transfer and Applications2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Remote sensing is about retrieving distant physical properties from locally observed radiation. The first step to remote sensing is to describe, or model, the radiative transfer. Without locating the origin of the observed radiation, and without proper interpretation of what it represents, understanding and utilizing instrumental results are nearly impossible. The focus of my thesis is on how radiation interacts with a weakly magnetized medium by means of the Zeeman effect. One molecule of particular interest affected by the Zeeman effect is the oxygen molecule. The thesis work started by an implementation of a module for the Zeeman effect in an existingradiative transfer model. Later works has applied this module to Earth and Mars radiative transfer.The high relative concentration of the oxygen molecule in Earth’s atmosphere, and the fact that the molecule interacts with sub-millimeter radiation, has made it a prime target for temperature retrievals using both ground- and satellite-based radiometers. The Zeeman effect is important for molecular oxygen at mesospheric altitudes on Earth, where the geometry of the magnetic field and of the observation influence the polarized absorption of radiation. Simulations of ground-based measurements by a radiometer in Bern, Switzerland, have the Zeeman module reproduce the dependency on observational geometry for the local magnetic field, partly validating the module. Simulations of satellite measurements comparing the Zeeman module to a fast, parameterized, implementation of the Zeeman effect for numerical weather predictions also indicates that the module works. There are small discrepancies between the two models but both are close to the satellite measurements given the noise of these measurements. Work to move beyond simulation space and analyze these satellite measurements to find the atmospheric temperatures at high altitudes also show promising results.Besides Earth applications, the module has been used for Mars conditions, where only trace amounts of molecular oxygen is available. Mars does not have a global magnetic field but instead have several magnetic sources scattered throughout its crust. This gives a magnetic field that is significantly weaker than on Earth and with much more structures. It is possible to utilize the Zeeman effect on molecular oxygen to measure the magnetic field of Mars. The last part of this thesis work suggests a measurement scheme for a satellite capable of retrieving the horizontal components of the Martian crustal magnetic field. It shows the expected errors associated with such a measurement scheme.

  • 255.
    Larsson, Richard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Mendrok, Jana
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A treatment of the Zeeman effect using Stokes formalism and its implementation in the Atmospheric Radiative Transfer Simulator ARTS2014Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 133, s. 445-453Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article presents the practical theory that was used to implement the Zeeman effect using Stokes formalism in the Atmospheric Radiative Transfer Simulator ARTS. ARTS now treats the Zeeman effect in a general manner for several gas species for all polarizations and takes into account variations in both magnetic and atmospheric fields along a full 3D geometry. We present how Zeeman splitting affects polarization in radiative transfer simulations and find that the effect may be large in Earth settings for polarized receivers in limb observing geometry. We find that not taking a spatially varying magnetic field into account can result in absolute errors in the measurement vector of at least 10 K in Earth magnetic field settings. The article also presents qualitative tests for O2 lines against previous models (61.15 GHz line) and satellite data from Odin-SMR (487.25 GHz line), and the overall consistency between previous models, satellite data, and the new ARTS Zeeman module seems encouraging.

  • 256.
    Larsson, Richard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    McKay, Christopher
    NASA Ames Research Center.
    Timescale for oceans in the past of Titan2013Inngår i: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, s. 22-24Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We estimate the past extent of liquid on the surface of Titan as a function of time assuming the current rate of destruction of methane and no sources or subsurface sinks. As methane increases for increasing past time the polar lakes expand equatorward. We use a spherical harmonics model for the surface topography to compute the fraction of the surface covered as the methane inventory increases. We find that substantial parts of the equator would have been flooded by a polar ocean 300 million years ago and that the equator would have been connected to a global ocean 600 million years ago. This provides one possible explanation for the fluvial features seen at the equator on Titan.

  • 257.
    Larsson, Richard
    et al.
    National Institute of Information and Communications Technology, Tokyo, Japan.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. IRV.
    Eriksson, Patrick
    Chalmers University of Technology, Göteborg.
    Mendrok, Jana
    Chalmers University of Technology, Göteborg.
    Kasai, Yasuko
    National Institute of Information and Communications Technology, Tokyo, Japan.
    Buehler, Stefan A.
    University of Hamburg.
    Diéval, Catherine
    Lancaster University.
    Brain, David
    University of Colorado, Boulder.
    Hartogh, Paul
    Max planck Institute for Solar System Research, Göttingen, Germany .
    Martian magnetism with orbiting sub-millimeter sensor: simulated retrieval system2017Inngår i: Geoscientific Instrumentation, Methods and Data Systems, ISSN 2193-0856, E-ISSN 2193-0864, Vol. 6, nr 1, s. 27-37Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A Mars-orbiting sub-millimeter sensor can be used to retrieve the magnetic field at low altitudes over large areas of significant planetary crustal magnetism of the sur- face of Mars from measurements of circularly polarized radi- ation emitted by the 368 GHz ground-state molecular oxygen absorption line. We design a full retrieval system for one ex- ample orbit to show the expected accuracies on the magnetic field components that one realization of such a Mars satellite mission could achieve. For one set of measurements around a tangent profile, we find that the two horizontal components of the magnetic field can be measured at about 200 nT error with a vertical resolution of around 4 km from 6 up to 70 km in tangent altitude. The error is similar regardless of the true strength of the magnetic field, and it can be reduced by re- peated measurements over the same area. The method and some of its potential pitfalls are described and discussed. 

  • 258.
    Larsson, Richard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Rayer, P.
    UK Met Office, Exeter.
    Saunders, R.
    UK Met Office, Exeter.
    Bell, W.
    UK Met Office, Exeter.
    Booton, A.
    UK Met Office, Exeter.
    Buehler, S.A.
    Meteorological Institute, University of Hamburg, Hamburg.
    Eriksson, P.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    John, V.
    EUMETSAT, Darmstadt.
    Modeling the Zeeman effect in high altitude SSMIS channels for numerical weather prediction profiles: Comparing a fast model and a line-by-line model2015Inngår i: Atmospheric Measurement Techniques Discussions, ISSN 1867-8610, E-ISSN 1867-8610, Vol. 8, nr 10, s. 10179-10211Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a comparison of a reference and a fast radiative transfer model using numerical weather prediction profiles for the Zeeman-affected high altitude Special Sensor Microwave Imager/Sounder channels 19–22. We find that the models agree well for channels 21 and 22 compared to the channels' system noise temperatures (1.9 and 1.3 K, respectively) and the expected profile errors at the affected altitudes (estimated to be around 5 K). For channel 22 there is a 0.5 K average difference between the models, with a standard deviation of 0.24 K for the full set of atmospheric profiles. Same channel, there is 1.2 K in average between the fast model and the sensor measurement, with 1.4 K standard deviation. For channel 21 there is a 0.9 K average difference between the models, with a standard deviation of 0.56 K. Same channel, there is 1.3 K in average between the fast model and the sensor measurement, with 2.4 K standard deviation. We consider the relatively small model differences as a validation of the fast Zeeman effect scheme for these channels. Both channels 19 and 20 have smaller average differences between the models (at below 0.2 K) and smaller standard deviations (at below 0.4 K) when both models use a two-dimensional magnetic field profile. However, when the reference model is switched to using a full three-dimensional magnetic field profile, the standard deviation to the fast model is increased to almost 2 K due to viewing geometry dependencies causing up to ± 7 K differences near the equator. The average differences between the two models remain small despite changing magnetic field configurations. We are unable to compare channels 19 and 20 to sensor measurements due to limited altitude range of the numerical weather prediction profiles. We recommended that numerical weather prediction software using the fast model takes the available fast Zeeman scheme into account for data assimilation of the affected sensor channels to better constrain the upper atmospheric temperatures.

  • 259.
    Larsson, Richard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Rayer, Peter
    UK Met Office, Exeter.
    Saunders, Roger
    UK Met Office, Exeter.
    Bell, William
    UK Met Office, Exeter.
    Booton, Anna
    UK Met Office, Exeter.
    Buehler, Stephan A.
    Meteorological Institute, University of Hamburg, Hamburg.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Earth and Space Sciences.
    John, Viju E.
    EUMETSAT, Darmstadt.
    Modeling the Zeeman effect in high altitude SSMIS channels for numerical weather prediction profiles: Comparing a fast model and a line-by-line model2016Inngår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 9, nr 2, s. 841-857Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a comparison of a reference and a fast radiative transfer model using numerical weather prediction profiles for the Zeeman-affected high altitude Special Sensor Microwave Imager/Sounder channels 19–22. We find that the models agree well for channels 21 and 22 compared to the channels' system noise temperatures (1.9 and 1.3 K, respectively) and the expected profile errors at the affected altitudes (estimated to be around 5 K). For channel 22 there is a 0.5 K average difference between the models, with a standard deviation of 0.24 K for the full set of atmospheric profiles. Same channel, there is 1.2 K in average between the fast model and the sensor measurement, with 1.4 K standard deviation. For channel 21 there is a 0.9 K average difference between the models, with a standard deviation of 0.56 K. Same channel, there is 1.3 K in average between the fast model and the sensor measurement, with 2.4 K standard deviation. We consider the relatively small model differences as a validation of the fast Zeeman effect scheme for these channels. Both channels 19 and 20 have smaller average differences between the models (at below 0.2 K) and smaller standard deviations (at below 0.4 K) when both models use a two-dimensional magnetic field profile. However, when the reference model is switched to using a full three-dimensional magnetic field profile, the standard deviation to the fast model is increased to almost 2 K due to viewing geometry dependencies causing up to ± 7 K differences near the equator. The average differences between the two models remain small despite changing magnetic field configurations. We are unable to compare channels 19 and 20 to sensor measurements due to limited altitude range of the numerical weather prediction profiles. We recommended that numerical weather prediction software using the fast model takes the available fast Zeeman scheme into account for data assimilation of the affected sensor channels to better constrain the upper atmospheric temperatures.

  • 260.
    Larsson, Richard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Ramstad, Robin
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Mendrok, Jana
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Kasai, Yasuko
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    A method for remote sensing of weak planetary magnetic fields: Simulated application to Mars2013Inngår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 40, nr 19, s. 5014-5018Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a method for characterizing the magnetic anomalies from the crustal fields in the lower atmosphere of Mars that requires two perpendicular linear polarization measurements of the Zeeman effect. The maximum effect of the magnetic field on the signal is found at the Doppler broadening width at low pressures rather than at the magnetically induced line frequency shift, and the effect strongly increases with increasing magnetic field strength. Based on simulations of the Zeeman-affected spectral cross section of the 119 GHz O2 line in a model Martian atmosphere at various magnetic field strengths, we conclude that it should be possible to probe the strength of the magnetic anomalies remotely with presently available technology. We discuss limitations of the method, how these results could be relevant to the interpretation of residuals in Herschel/HIFI observations of Mars, as well as the application to detection of exoplanetary magnetic fields.

  • 261.
    Lasue, J.
    et al.
    IRAP-OMP, CNRS-UPS, Toulouse.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zorzano Mier, Maria-Paz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    What ChemCam’s first shots tell us about martian dust?2017Konferansepaper (Annet vitenskapelig)
  • 262.
    Leblebici, Robin
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Development of an automated adjusting process for robotic end-effectors to handle dry textiles for preforming of carbon fiber reinforced plastics2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In order to fulfill increasing production rates, new automated production technologies are required for manufacturing carbon fiber reinforced plastic components for the aerospace industry. Currently, large, double curved composite components have to be manufactured manually, which leads to high process times and poor scalability. As a consequence, a team of cooperating robots with passively adjustable end-effectors was developed, that is capable of handling dry carbon textiles and can be used for layups in double curved molds. This thesis deals with the implementation of a robot program, that performs an automated adjustment of each end-effector to the surface geometry of the manufactured part. The functional principle and the accuracy of the process are evaluated. Further, the automatically adjusted end-effectors are utilized to cooperatively layup carbon plies. The results show, that the accuracy of the automated adjusting process is sufficient to drape carbon fabrics during pick-up and automated layup is possible with this approach. In conclusion, the developed process can be integrated into a fully automated process for future experiments, but hardware inaccuracies should be improved, in order to further enhance the accuracy of the system.

  • 263.
    Li, Yuangui
    et al.
    Department of Automation, Shanghai Jiaotong University.
    Lin, Chen
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Huang, Jinjie
    Department of Automation, Shanghai Jiaotong University.
    Zhang, Weidong
    Department of Automation, Shanghai Jiaotong University.
    A new method to construct reduced vector sets for simplifying support vector machines2006Inngår i: IEEE International Conference on Engineering of Intelligent Systems, Piscataway, NJ: IEEE Communications Society, 2006Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Support vector machines (SVM) are well known to give good results on pattern recognition problems, but for large scale problems, they exhibit substantially slower classification speeds than neural networks. It has been proposed to speed the SVM classification by approximating the decision function of SVM with a reduced vector set. A new method to construct the reduced vector set is proposed in this paper, which is constructed by merging the closest support vectors in an iterative fashion. A minor modification on the proposed method also has been made in order to simplify the decision function of reduced support vector machines (RSVM). The proposed method was compared with previous study on several benchmark data sets, and the computational results indicated that our method could simplify SVMs and RSVMs effectively, which will speed the classification for large scale problems

  • 264.
    Li, Yuangui
    et al.
    Department of Automation, Shanghai Jiaotong University.
    Lin, Chen
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zhang, Weidong
    Department of Automation, Shanghai Jiaotong University.
    Improved sparse least-squares support vector machine classifiers2006Inngår i: Neurocomputing, ISSN 0925-2312, E-ISSN 1872-8286, Vol. 69, nr 13-15, s. 1655-1658Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The least-squares support vector machines (LS-SVM) can be obtained by solving a simpler optimization problem than that in standard support vector machines (SVM). Its shortcoming is the loss of sparseness and this usually results in slow testing speed. Several pruning methods have been proposed. It is found that these methods can be further improved for classification problems. In this paper a different reduced training set is selected to re-train LS-SVM. Then a new procedure is proposed to obtain the sparseness. The performance of the proposed method is compared with other typical ones and the results indicate that it is more effective.

  • 265.
    Lidström, Viktor
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mass Loading of Space Plasmas2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The solar wind interaction with an icy comet is studied through a model problem. A hybrid simulation is done of a box with evenly distributed water ions and protons, where initially the water ions are stationary, and protons move with the speed of the solar wind. The purpose of the thesis is to investigate the interaction between the two species through the convective electric field, and focus is on early acceleration of pick-up ions, and deflection of the solar wind. It is relevant to the cometary case, because it enables study of the physics of this interaction, without involving other mechanisms, such as bow shock, magnetic field pile-up and draping. The species are found to exchange kinetic energy similar to a damped oscillator, where the dampening is caused by kinetic energy being transferred to the magnetic field. At early times, i.e. times smaller than the gyration time for the water ions, the solar wind does not lose much speed when it is deflected. For comparable number densities, the solar wind can be deflected more than 90° at early times, and loses more speed, and water ions are picked up faster. The total kinetic energy of the system decreases when energy builds up in the magnetic field. The nature of the energy exchange is strongly dependent on the number density ratio between water ions and protons. A density instability with behaviour similar to a plasma beam instability forms as energy in the magnetic field increases, and limits the amount of time the simulation preserves total energy, for the particular hybrid solver used. There is a discussion on the structure of the density instability, and it is compared to cometary simulations.

  • 266.
    Lue, Charles
    et al.
    Luleå tekniska universitet.
    Futaana, Yoshifumi
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Wieser, Martin
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Holmström, Mats
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Bhardwaj, Anil
    Space Physics Laboratory, Vikram Sarabhai Space Center, Trivandrum.
    Dhanya, M.B.
    Space Physics Laboratory, Vikram Sarabhai Space Center, Trivandrum.
    Wurz, Peter
    Physikalisches Institut, University of Bern.
    Strong influence of lunar crustal fields on the solar wind flow2011Inngår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 38, nr 3Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We discuss the influence of lunar magnetic anomalies on the solar wind and on the lunar surface, based on maps of solar wind proton fluxes deflected by the magnetic anomalies. The maps are produced using data from the Solar WInd Monitor (SWIM) onboard the Chandrayaan-1 spacecraft. We find a high deflection efficiency (average ∼10%, locally ∼50%) over the large-scale (>1000 km) regions of magnetic anomalies. Deflections are also detected over weak (<3 nT at 30 km altitude) and small-scale (<100 km) magnetic anomalies, which might be explained by charge separation and the resulting electric potential. Strong deflection from a wide area implies that the magnetic anomalies act as a magnetosphere-like obstacle, affecting the upstream solar wind. It also reduces the implantation rate of the solar wind protons to the lunar surface, which may affect space weathering near the magnetic anomalies.

  • 267.
    Lukanovic, Matej
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Evaluation Analysis of the UV-detector on the Mini-EUSO Space Telescope2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Extragalactic charged particles, each with energies rising up to and beyond 1 Joule, have been studied for almost a century. Yet, no precise evidence have proven to show where they might originate from as their energy levels rise above the current familiar acceleration sources in outer space. The highly energetic particles have been given the name Ultra-High Energy Cosmic Rays (UHECR) and investigations of particle properties such as primary energy, mass composition and direction can be made through indirect measurements of the interaction between the UHECR and Earth's atmosphere. The considered interaction induces an Extensive Air Shower (EAS) which emits fluorescent light in the Ultraviolet (UV) range. The probability of detecting such events is, however, as low as a few particles per km2 per century. Making observations more sufficient therefore requires larger detection volumes.

    By introducing the Mini-EUSO instrument, a telescope of which the main purpose is to measure the UV-light radiated from the Earth in the wavelength range of 300-400 nm, allows just for this. To be accommodating the International Space Station and targeting Earth in the nadir direction, the Mini-EUSO instrument will allow for a higher exposure to the interactions than what is currently available. The use of two Fresnel lenses provides the instrument with a large field of view (±22o) and the detections are made through multiple photomultiplier tubes.

    The scope of this thesis is to evaluate the main detector of the Mini-EUSO instrument (i.e. the UV-detector) through ground-based tests. The procedures involved in the evaluation have consisted of; validating the statistical distributions of the signals, implementing dark field and flat field calibrations, and radiations measurements with three kinds of radiation sources. The data from the tests were provided during two periods and the visualization was made by adapting an already existing piece of code, using Python and ROOT Cern, to perform step by step procedures such that all operations are overlooked properly.

    The analysis showed that the implementation of the dark field and flat field procedures improved the original image significantly. It also showed that both the lower and higher photon count values in a pixel indeed gave the expected statistical behaviours, with a Poissonian distribution for low values and a Gaussian distribution for higher values. The flat fielding screen did however show unknown fluctuations in the emitted light and further tests have to be implemented to assure its functionality. Under proper covering, almost no dark current was found, however, observation tests showed that the borders of the Multi-Anode Photomultiplier Tubes (MAPMTs) gave higher photon count values than the center part even when they were emitted with Lambertian light.

  • 268.
    Mahaffy, P.R.
    et al.
    Planetary Environments Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland, NASA Goddard Space Flight Center.
    Conrad, Pamela G.
    NASA Goddard Space Flight Center.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Volatile and Isotopic Imprints of Ancient Mars2015Inngår i: Elements, ISSN 1811-5209, E-ISSN 1811-5217, Vol. 11, nr 1, s. 51-56Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The science investigations enabled by Curiosity rover's instruments focus on identifying and exploring the habitability of the Martian environment. Measurements of noble gases, organic and inorganic compounds, and the isotopes of light elements permit the study of the physical and chemical processes that have transformed Mars throughout its history. Samples of the atmosphere, volatiles released from soils, and rocks from the floor of Gale Crater have provided a wealth of new data and a window into conditions on ancient Mars.

  • 269.
    Mahfouf, J.-F.
    et al.
    CNRM–GAME, Météo-France and CNRS.
    Birman, C.
    CNRM–GAME, Météo-France and CNRS.
    Aires, F.
    Estellus, Paris.
    Prigent, C.
    L'Observatoire de Paris-LERMA.
    Orlandi, E.
    University of Cologne.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Information content on temperature and water vapour from a hyper-spectral microwave sensor2015Inngår i: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 141, nr 693, s. 3268-3284Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study examines the information content on atmospheric temperature and humidity profiles that could be provided by a future spaceborne microwave sensor with a few hundred radiances in the millimetre and submillimetre spectral domains (ranging from 7–800 GHz). A channel selection method based on optimal estimation theory is undertaken, using a database of profiles with associated errors from the European Centre for Medium-Range Weather Forecasts (ECMWF) numerical weather prediction model and the radiative transfer model Atmospheric Radiative Transfer Simulator (ARTS) under clear-sky conditions. The main results indicate that, by increasing the number of channels within the oxygen absorption band around 60 GHz and within the water-vapour absorption band at 183 GHz, the accuracy of temperature and humidity retrievals in the troposphere and stratosphere (for temperature) would be noticeably improved compared with present and planned microwave radiometers. The channels located in the absorption lines at 118 GHz and above 200 GHz do not bring significant additional information regarding atmospheric profiles under clear-sky conditions, partly due to greater radiometric noise. With a set of 137 selected channels that contribute to 90% of the total information content (measured by the degree of freedom for signal), it is possible to achieve almost the same performance in terms of variance error reduction as with 276 candidate channels. Sensitivity studies of various prescribed quantities defining the channel selection have been undertaken, in order to check the robustness of the conclusions. They show that none of the choices modifies the above findings.

  • 270.
    Mannes, Quentin
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    ICE Cubes Mission: Design, Development and Documentation of the Cube-Zero System2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The International Space Station provides a high-quality of microgravity and extended exposure time which makes it a platform of choice for microgravity research. In order to increase accessibility of onboard experimentation, Space Applications Services will soon launch the ICE Cubes facility as part of its ICE Cubes Service. The facility is foreseen to host standardized plug-and-play payload cubes to reduce overall cost and procedure time required to install payloads on the station. To remotely support the facility it is decided to develop a utility cube named Cube-Zero that will be launched and installed with the facility on the station. This thesis work included the complete design, development and documentation of the cube.

    The thesis started by conducting a preliminary needs and market study from which two specific purposes were defined for the cube. In addition to its original function of support-utility, the cube is tasked to be a technical commercial demonstrator for the service. This led to the conceptual design of the cube as a multidisciplinary framework able to host two user-defined experiment modules. The preliminary concept was further refined in this paper and with support of prototypes, simulations and analyses led to a final functional design for the Cube-Zero.

    The work is concluded with the manufacturing of an engineering model of the cube. The model is fully operational, can support the test of the facility before launch and can demonstrate to users its versatility and ease of use in operating any kind of experiment module.

    Eventually, the information gathered in this thesis report will support future users into developing their own Cube-Zero payload module and guide Space Applications Services into manufacturing, testing and operating the Cube-Zero protoflight model.

  • 271.
    Martell, Angel Alfredo
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Benchmarking structure from motion algorithms with video footage taken from a drone against laser-scanner generated 3D models2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Structure from motion is a novel approach to generate 3D models of objects and structures. The dataset simply consists of a series of images of an object taken from different positions. The ease of the data acquisition and the wide array of available algorithms makes the technique easily accessible. The structure from motion method identifies features in all the images from the dataset, like edges with gradients in multiple directions, and tries to match these features between all the images and then computing the relative motion that the camera was subject to between any pair of images. It builds a 3D model with the correlated features. It then creates a 3D point cloud with colour information of the scanned object. There are different implementations of the structure from motion method that use different approaches to solve the feature-correlation problem between the images from the data set, different methods for detecting the features and different alternatives for sparse reconstruction and dense reconstruction as well. These differences influence variations in the final output across distinct algorithms.

    This thesis benchmarked these different algorithms in accuracy and processing time. For this purpose, a terrestrial 3D laser scanner was used to scan structures and buildings to generate a ground truth reference to which the structure from motion algorithms were compared. Then a video feed from a drone with a built-in camera was captured when flying around the structure or building to generate the input for the structure from motion algorithms. Different structures are considered taking into account how rich or poor in features they are, since this impacts the result of the structure from motion algorithms. The structure from motion algorithms generated 3D point clouds, which then are analysed with a tool like CloudCompare to benchmark how similar it is to the laser scanner generated data, and the runtime was recorded for comparing it across all algorithms. Subjective analysis has also been made, such as how easy to use the algorithm is and how complete the produced model looks in comparison to the others.

    In the comparison it was found that there is no absolute best algorithm, since every algorithm highlights in different aspects. There are algorithms that are able to generate a model very fast, managing to scale the execution time linearly in function of the size of their input, but at the expense of accuracy. There are also algorithms that take a long time for dense reconstruction, but generate almost complete models even in the presence of featureless surfaces, like COLMAP modified PatchMacht algorithm. The structure from motion methods are able to generate models with an accuracy of up to \unit[3]{cm} when scanning a simple building, where Visual Structure from Motion and Open Multi-View Environment ranked among the most accurate. It is worth highlighting that the error in accuracy grows as the complexity of the scene increases. Finally, it was found that the structure from motion method cannot reconstruct correctly structures with reflective surfaces, as well as repetitive patterns when the images are taken from mid to close range, as the produced errors can be as high as \unit[1]{m} on a large structure.

  • 272.
    Martin-Torres, Javier
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mier, Maria-Paz Zorzano
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Vida Extraterrestre: Implicaciones2015Inngår i: Burgense, ISSN 0521-8195, Vol. 55, nr 1, s. 197-206Artikkel i tidsskrift (Fagfellevurdert)
  • 273.
    Martin-Torres, Javier
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zorzano, María-Paz
    Centro de Astrobiologia, INTA-CSIC, Madrid , Instituto Nacional de Técnica Aeroespacial, Madrid, Centro de Astrobiologia, Madrid.
    Valentin-Serrano, Patricia
    CSIC-UGR - Instituto Andaluz de Ciencias de la Tierra (IACT), Granada.
    Harri, Ari-Matti
    Earth Observation Research Division, Finnish Meteorological Institute, Helsinki.
    Genzer, Maria
    Finnish Meteorological Institute, Earth Observation Research Division, Finnish Meteorological Institute, Helsinki.
    Kemppainen, Osku
    Finnish Meteorological Institute, Earth Observation Research Division, Finnish Meteorological Institute, Helsinki.
    Rivera-Valentin, Edgard G.
    Arecibo Observatory, Universities Space Research Association, Arecibo, Puerto Rico.
    Jun, Insoo
    California Institute of Technology, Jet Propulsion Laboratory.
    Wray, James J.
    School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta.
    Madsen, Morten B.
    Niels Bohr Institute, University of Copenhagen.
    Goetz, Walter
    Max-Planck-Institut für Solar System Research.
    McEwen, Alfred S,
    Lunar and Planetary Lab, University of Arizona, Tucson.
    Hardgrove, Craig
    Arizona State University, Department of Earth & Planetary Sciences, University of Tennessee, Knoxville, Malin Space Science Systems.
    Renno, Nilton
    University of Michigan, College of Engineering, University of Michigan, Ann Arbor.
    Chevrier, Vincent F.
    Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville.
    Mischna, Michael A.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Navarro-Gonzalez, Rafael
    Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de Mexico, Ciudad Universitaria, Centro de Astrobiologia, INTA-CSIC, Madrid , Universidad Nacional Autónoma de México, Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Mexico D.F., Laboratorio de Química de Plasmas y Estudios Planetarios, Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México.
    Martínez-Frías, Jesús
    Centro de Astrobiologia, INTA-CSIC, Madrid , Instituto de Geociencias (CSIC-UCM), 28040 Madrid.
    Conrad, Pamela G.
    NASA Goddard Space Flight Center, Solar System Exploration Division, Goddard Space Flight Center, National Aeronautics and Space Administration, Greenbelt, Maryland.
    McConnochie, Timothy H.
    Department of Astronomy, University of Maryland, College Park.
    Cockell, Charles
    ESO, UK Centre for Astrobiology, School of Physics and Astronomy,.
    Berger, Gilles
    IRAP/CNRS, Institut de Recherche en Astrophysique et Planetologie, Toulouse, Université de Toulouse, UPS-OMP, IRAP.
    Vasavada, Ashwin
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Sumner, Dawn Y.
    Department of Earth and Planetary Sciences, University of California, Davis, Department of Geology, University of California, Davis.
    Vaniman, David T.
    Planetary Science Institute, Tucson.
    Transient liquid water and water activity at Gale crater on Mars2015Inngår i: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 8, nr 5, s. 357-361Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Water is a requirement for life as we know it1. Indirect evidence of transient liquid water has been observed from orbiter on equatorial Mars2, in contrast with expectations from large-scale climate models. The presence of perchlorate salts, which have been detected at Gale crater on equatorial Mars by the Curiosity rover3, 4, lowers the freezing temperature of water5. Moreover, perchlorates can form stable hydrated compounds and liquid solutions by absorbing atmospheric water vapour through deliquescence6, 7. Here we analyse relative humidity, air temperature and ground temperature data from the Curiosity rover at Gale crater and find that the observations support the formation of night-time transient liquid brines in the uppermost 5 cm of the subsurface that then evaporate after sunrise. We also find that changes in the hydration state of salts within the uppermost 15 cm of the subsurface, as measured by Curiosity, are consistent with an active exchange of water at the atmosphere–soil interface. However, the water activity and temperature are probably too low to support terrestrial organisms8. Perchlorates are widespread on the surface of Mars9 and we expect that liquid brines are abundant beyond equatorial regions where atmospheric humidity is higher and temperatures are lower.

  • 274.
    Martín-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A space rose by another name smells sweeter2017Inngår i: New scientist (1971), ISSN 0262-4079, Vol. 233, nr 3116, s. 52-54Artikkel i tidsskrift (Fagfellevurdert)
  • 275.
    Martín-Torres, Javier
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zorzano Mier, Maria-Paz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Should We Invest in Martian Brine Research to Reduce Mars Exploration Costs?2017Inngår i: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 17, nr 1, s. 3-7Artikkel i tidsskrift (Fagfellevurdert)
  • 276.
    Mendaza de Cal, Maria Teresa
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Blanco-Ávalos, J.J.
    Universidad Alcalá de Henares (UAH) Dpto. Física y Matemáticas, Campus Científico-Tecnológico (Externo) Alcalá de Henares (Madrid).
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Instituto Andaluz de Ciencias de la Tierra (UGR-CSIC), Avenida de las Palmeras 4, Armilla, Granada, Spain.
    Interplanetary Coronal Mass Ejection effects on thermospheric density as inferred from International Space Station orbital data2017Inngår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 60, nr 10, s. 2233-2251Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The solar activity induces long term and short term periodical variations in the dynamics and composition of Earth’s atmosphere. The Sun also shows non periodical (i.e., impulsive) activity that reaches the planets orbiting around it. In particular, Interplanetary Coronal Mass Ejections (ICMEs) reach Earth and interact with its magnetosphere and upper neutral atmosphere. Nevertheless, the interaction with the upper atmosphere is not well characterized because of the absence of regular and dedicated in situ measurements at high altitudes; thus, current descriptions of the thermosphere are based on semi empirical models.

    In this paper, we present the total neutral mass densities of the thermosphere retrieved from the orbital data of the International Space Station (ISS) using the General Perturbation Method, and we applied these densities to routinely compiled trajectories of the ISS in low Earth orbit (LEO). These data are explicitly independent of any atmospheric model. Our density values are consistent with atmospheric models, which demonstrates that our method is reliable for the inference of thermospheric density. We have inferred the thermospheric total neutral density response to impulsive solar activity forcing from 2001 to the end of 2006 and determined how solar events affect this response. Our results reveal that the ISS orbital parameters can be used to infer the thermospheric density and analyze solar effects on the thermosphere.

  • 277.
    Mendrok, Jana
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Eriksson, Patrick
    Chalmers University of Technology.
    PERRIN, Agnes
    LISA, CNRS.
    HARTOGH, Paul
    Max-Planck-Institut für Solar System Research.
    REZAC, Ladislav
    Max-Planck-Institut für Solar System Research.
    Lemke, Oliver
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    ARTS+ - A toolbox for microwave atmospheric radiative transfer in solar system planets2013Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Microwave and (sub)millimetre-wave frequencies have long been of interest for remote sensing of the Earth and space objects. They suffer less from interference by small particles (dust, clouds), hence penetrate deeper into atmospheres revealing their deeper structures hidden to shorter wavelengths, and possess characteristic line absorption features of many gaseous species, which are of interest for the understanding of atmospheric chemistry and dynamics.Models simulating radiative transfer and wave propagation (RT/WP) have been developed by many institutions. Most of them are designed for a particular, narrow region of the electromagnetic spectrum, certain instrument types or missions, and specific atmospheric conditions. In particular, they are usually set up for a specific planetary body. This high level of specialisation allows for accurate modelling results. However, it also limits the flexibility of those models and comparability between them.For various applications there is a demand on easy and quick calculations of propagation characteristics, like feasibility estimates of missions proposed to space agencies and performance estimates of radiocommunication links between satellites or orbiter and lander.Within an ESA study we have developed a toolbox for microwave RT/WP in planetary atmospheres. The toolbox consists of the RT/WP model and a data package. The RT/WP model is a largely revised and extended version of ARTS, a sophisticated, flexible RT model for Earth atmosphere (3D spherical geometry, diverse absorption models, scattering, polarization, Jacobians). Focus has been on creating a consistent, physics-based model. Several features have been added (radio link and cloud radar modes, zeeman splitting, doppler shifts). A new spectroscopic approach has been implemented considering effects of a range of broadening/pressure-shifting/refracting species, a corresponding spectroscopic line catalogue designed and prepared. At the current state, the data package contains atmospheric and surface data for Earth and the planets Venus, Mars, and Jupiter, but is easily extendable.We will illustrate the capabilities of the toolbox introducing several example cases and presenting results from the toolbox validation.

  • 278.
    Mendrok, Jana
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Wu, Dong L.
    Jet Propulsion Laboratory.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Jimenez, Carlos
    Observatoire de Paris.
    Kasai, Yasuko
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Sub-millimeter wave radiometer for observation of cloud ice: a proposal for Japanese mission2009Inngår i: Sensors, Systems, and Next-Generation Satellites XIII: 31 August - 3 September 2009, Berlin, Germany / [ed] Roland Meynart, Bellingham, Wash: SPIE - International Society for Optical Engineering, 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Ice clouds play an important role in the energy budget of the atmosphere as well as in the hydrological cycle. Currently cloud ice is one of the largest remaining uncertainties in climate models. Large discrepancies arise from different assumptions on ice cloud properties, in particular on microphysics, which are not sufficiently constrained by measurements. Passive sub-millimeter wave (SMM) techniques have the potential of providing direct information on ice content and particle sizes with daily global coverage. Here we introduce a concept for a compact 2-receiver SMM sensor and demonstrate its capabilities on measurements of ice content, mean particle size, and cloud altitude.

  • 279.
    Mihalikova, Maria
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mesoscale processes in the polar atmosphere: radar remote sensing, balloon-borne in situ measurements and modelling2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Mesoscale processes (atmospheric phenomena with horizontal scales ranging from a few tens to several hundred kilometres and lasting from a few tens of minutes to a few days) have the potential to influence the chemical composition of the troposphere. Tropopause folds and mountain waves are two important types of mesoscale processes. Concentrations and gradients of trace gases like ozone (O3) can be influenced by these processes. Tropopause folds bring ozone-rich stratospheric air to lower altitudes. Mountain waves and turbulence associated with them influence O3 gradients in the troposphere. Tropospheric O3 is a toxic pollutant and a short-lived greenhouse gas with an influence on the lifetime of many other trace gases. Understanding of its long-term development and budgets are important. For this, better understanding, generalization and representation of mesoscale processes are necessary. Observations made by the 52MHz wind-profiler radar ESRAD (ESrange RADar) and the 54.5MHz wind-profiler radar MARA (Movable Atmospheric Radar for Antarctica) served as the basis for this study. ESRAD is located close to Kiruna in arctic Sweden and has been in operation since July 1996. This is a site with frequent mountain wave activity. By analysis of ESRAD and sonde data we have studied vertical mixing and turbulence associated with mountain waves. An attempt was made to show the influence of these processes on relaxation of the O3 gradient in the lower troposphere. Additional balloon-borne in situ measurements of vertical profiles of atmospheric characteristics (temperature, humidity, O3 mixing ratio) complement the radar measurements and aid in correct identification and improved understanding of the observed processes as well as of the radar backscatter signal itself. MARA was operated at the Swedish summer station Wasa (73°S, 13.5°W) during austral summer 2010/2011 and at the Norwegian year-round station Troll (72°S, 2.5°E) nonstop since December 2011. During its operation at the Wasa station, ozonesonde measurements were successfully undertaken during the passage of a tropopause fold. These provided validity to the radar measurements and proved them to be a useful tool for tropopause fold studies, for the first time at Antarctic latitudes. Data gathered at the Troll station exhibit signs of an annual cycle of tropopause folds with winter maximum and summer minimum in their occurrence rate which is similar to the observed behaviour in the northern hemisphere. Comparisons with ECMWF (European Centre for Medium-Range Weather Forecasts) model data and the WRF model (Advanced Research and Weather Forecasting) show that higher resolution models such as WRF are needed for more adequate representation of these processes. High resolution models can in return serve as a basis for studies of areas that are not at all or only partially covered by measurement networks, as well as for global studies. Thus they can provide useful information about atmospheric transport and the state of trace gases like O3.

  • 280.
    Mihalikova, Maria
    et al.