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  • 151.
    Fernández-Remolar, David C.
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Harir, Mourad
    Research Unit Analytical Biogeochemistry, Department of Environmental Sciences, Helmholtz Zentrum München, Neuherberg, Germany.
    Carrizo, Daniel
    Centro de Astrobiología (INTA-CSIC), Torrejón de Ardoz, Madrid, Spain.
    Schmitt-Kopplin, Philippe
    Research Unit Analytical Biogeochemistry, Department of Environmental Sciences, Helmholtz Zentrum München, Neuherberg, Germany.
    Amils, Ricardo
    Centro de Astrobiología (INTA-CSIC), Torrejón de Ardoz, Madrid, Spain; Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Madrid, Spain.
    Productivity contribution of Paleozoic woodlands to the formation of shale hosted massive sulfide deposits in the Iberian Pyrite Belt (Tharsis, Spain)2018Inngår i: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 123, nr 3, s. 1017-1040Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The geological materials produced during catastrophic and destructive events are an essential source of paleobiological knowledge. The paleobiological information recorded by such events can be rich in information on the size, diversity, and structure of paleocommunities. In this regard, the geobiological study of late Devonian organic matter sampled in Tharsis (Iberian Pyrite Belt) provided some new insights into a Paleozoic woodland community,which was recorded as massive sulfides and black shale deposits affected by a catastrophic event. Sample analysis using TOF-SIMS (Time of Flight Secondary Ion Mass Spectrometer), and complemented by GC/MS (Gas Chromatrograph/Mass Spectrometer) identified organic compounds showing a very distinct distribution in the rock. While phytochemical compounds occur homogeneously in the sample matrix that is composed of black shale, the microbial-derived organics are more abundant in the sulfide nodules. The co-occurrence of sulfur bacteria compounds and the overwhelming presence of phytochemicals provide support for the hypothesis that the formation of the massive sulfides resulted from a high rate of vegetal debris production and its oxidation through sulfate reduction under suboxic to anoxic conditions. A continuous supply of iron from hydrothermal activity coupled with microbial activity was strictly necessary to produce this massive orebody. A rough estimate of the woodland biomass was made possible by accounting for the microbial sulfur production activity recorded in the metallic sulfide. As a result, the biomass size of the late Devonian woodland community was comparable to modern woodlands like the Amazon or Congo rainforests.

  • 152.
    Flores Garcia, Erick
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Simulation of attitude and orbital disturbances acting on ASPECT satellite in the vicinity of the binary asteroid Didymos2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Asteroid missions are gaining interest from the scientific community and many new missions are planned. The Didymos binary asteroid is a Near-Earth Object and the target of the Asteroid Impact and Deflection Assessment (AIDA). This joint mission, developed by NASA and ESA, brings the possibility to build one of the first CubeSats for deep space missions: the ASPECT satellite. Navigation systems of a deep space satellite di er greatly from the common planetary missions. Orbital environment close to an asteroid requires a case-by-case analysis. In order to develop the Attitude Determination Control System (ADCS) for the mission, one needs detailed information about orbital disturbances in the vicinity of the asteroid.

    This work focuses on the development of a simulator that characterises the orbital disturbances a ecting the ASPECT satellite in the space environment near the Didymos asteroid. In this work, a model of orbital conditions and disturbances near the Didymos system was defined. The model integrates several classical and modern models of spacecraft motion and disturbance. An existing Low Earth Orbit (LEO) simulator was modified and updated accordingly to the ASPECT mission scenario. The developed simulator can be used to analyse the disturbances to be counteracted by the ADCS of the ASPECT satellite. The objective of the study was to quantify the e ect of both non-gravitational and gravitational disturbances. The simulator was used to analyse di erent orbit scenarios related to the period of the mission and to the relative distance between the spacecraft and the asteroid system. In every scenario, the solar radiation pressure was found to be the strongest of the disturbance forces. With the developed simulator, suitable spacecraft configurations and control systems can be chosen to mitigate the e ect of the disturbances on the attitude and orbit of the ASPECT satellite. 

  • 153.
    Fonseca, Ricardo
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Earth Observatory of Singapore, Nanyang Technological University, Singapore.
    Koh, Tieh-Yong
    Earth Observatory of Singapore, Nanyang Technological University, Singapore; UC, Singapore University of Social Sciences, Singapore.
    Teo, Chee-Kiat
    UC, Singapore University of Social Sciences, Singapore; Centre for Climate Research Singapore, Meteorological Services Singapore, Singapore.
    Multi-scale interactions in a high-resolution tropical-belt experiment and observations2018Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Weather Research and Forecasting (WRF) model is used to dynamically downscale 27 years of the Climate Forecast System Reanalysis (CFSR) in a tropical belt configuration at 36 km horizontal grid spacing. WRF is found to give a good rainfall climatology as observed by the Tropical Rainfall Measuring Mission (TRMM) and to reproduce well the large-scale circulation and surface radiation fluxes. The impact of conventional and Modoki-type El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) are confirmed by linear regression. Madden–Julian Oscillation (MJO) and Boreal Summer Intra-seasonal Oscillation (BSISO) are also well-simulated. The WRF simulation shows that conventional El Niño increases (La Niña decreases) the MJO amplitude in the boreal summer while Modoki-type ENSO and IOD impacts are MJO-phase dependent. While WRF is found to perform well on seasonal to sub-seasonal timescales, it does not capture well the diurnal cycle of precipitation over the Maritime Continent. For the investigation of multi-scale interactions through the local diurnal cycle, TRMM data is used instead. In the Maritime Continent, moderate El Niño and La Niña causes anti-symmetric enhancement/reduction of the MJO’s influence on the diurnal cycle amplitudes with little change in the diurnal phase. Non-linear impacts on the diurnal amplitude with changes in diurnal phase manifest during strong ENSO. Given that the simulation does not employ data assimilation, this modified version of WRF submitted to the model developers is a suitable downscaling tool of CFSR for sub-seasonal to seasonal tropical atmospheric research.

  • 154.
    Fonseca, Ricardo
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Granada.
    Andersson, Kent
    Swedish Space Corporation, Esrange Space Center, Kiruna.
    Wind Forecasts for Rocket and Balloon Launches at the Esrange Space Center Using the WRF Model2018Inngår i: Weather and forecasting, ISSN 0882-8156, E-ISSN 1520-0434, Vol. 33, nr 3, s. 813-833Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High-altitude balloons and rockets are regularly launched at the Esrange Space Center (ESC) in Kiruna, Sweden, with the aim of retrieving atmospheric data for meteorological and space studies in the Arctic region. Meteorological conditions, particularly wind direction and speed, play a critical role in the decision of whether to go ahead with or postpone a planned launch. Given the lack of high-resolution wind forecasts for this remote region, the Weather Research and Forecasting (WRF) Model is used to downscale short-term forecasts given by the Global Forecast System (GFS) for the ESC for six 5-day periods in the warm, cold, and transition seasons. Three planetary boundary layer (PBL) schemes are considered: the local Mellor-Yamada-Janjic' (MYJ), the nonlocal Yonsei University (YSU), and the hybrid local-nonlocal Asymmetric Convective Model 2 (ACM2). The ACM2 scheme is found to provide the most skillful forecasts. An analysis of the WRF Model output against the launch criteria for two of the most commonly launched vehicles, the sounding rockets Veículo de Sondagem Booster-30 (VSB-30) and Improved Orion, reveals probability of detection (POD) values that always exceeds 60% with the false alarm rate (FAR) generally below 50%. It is concluded that the WRF Model, in its present configuration, can be used to generate useful 5-day wind forecasts for the launches of these two rockets. The conclusions reached here are applicable to similar sites in the Arctic and Antarctic regions.

  • 155.
    Fonseca, Ricardo
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Martín-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), 18100 Granada, Spain.
    High-Resolution Dynamical Downscaling of Re-Analysis Data over the Kerguelen Islands using the WRF Model2018Inngår i: Journal of Theoretical and Applied Climatology, ISSN 0177-798X, E-ISSN 1434-4483Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have used the Weather Research and Forecasting (WRF) model to simulate the climate of the Kerguelen Islands (49° S, 69° E) and investigate its inter-annual variability. Here, we have dynamically downscaled 30 years of the Climate Forecast System Reanalysis (CFSR) over these islands at 3-km horizontal resolution. The model output is found to agree well with the station and radiosonde data at the Port-aux-Français station, the only location in the islands for which observational data is available. An analysis of the seasonal mean WRF data showed a general increase in precipitation and decrease in temperature with elevation. The largest seasonal rainfall amounts occur at the highest elevations of the Cook Ice Cap in winter where the summer mean temperature is around 0 °C. Five modes of variability are considered: conventional and Modoki El Niño-Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), Subtropical IOD (SIOD) and Southern Annular Mode (SAM). It is concluded that a key mechanism by which these modes impact the local climate is through interaction with the diurnal cycle in particular in the summer season when it has a larger magnitude. One of the most affected regions is the area just to the east of the Cook Ice Cap extending into the lower elevations between the Gallieni and Courbet Peninsulas. The WRF simulation shows that despite the small annual variability, the atmospheric flow in the Kerguelen Islands is rather complex which may also be the case for the other islands located in the Southern Hemisphere at similar latitudes.

  • 156.
    Fonseca, Ricardo
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zorzano Mier, María-Paz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Centro de Astrobiología (INTA-CSIC).
    Martín-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR).
    Planetary Boundary Layer and Circulation Dynamics at Gale Crater, Mars2018Inngår i: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 302, s. 537-559Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Mars implementation of the Planet Weather Research and Forecasting (PlanetWRF) model, MarsWRF, is used here to simulate the atmospheric conditions at Gale Crater for different seasons during a period coincident with the Curiosity rover operations. The model is first evaluated with the existing single-point observations from the Rover Environmental Monitoring Station (REMS), and is then used to provide a larger scale interpretation of these unique measurements as well as to give complementary information where there are gaps in the measurements.

    The variability of the planetary boundary layer depth may be a driver of the changes in the local dust and trace gas content within the crater. Our results show that the average time when the PBL height is deeper than the crater rim increases and decreases with the same rate and pattern as Curiosity's observations of the line-of-sight of dust within the crater and that the season when maximal (minimal) mixing is produced is Ls 225°-315° (Ls 90°-110°). Thus the diurnal and seasonal variability of the PBL depth seems to be the driver of the changes in the local dust content within the crater. A comparison with the available methane measurements suggests that changes in the PBL depth may also be one of the factors that accounts for the observed variability, with the model results pointing towards a local source to the north of the MSL site.

    The interaction between regional and local flows at Gale crater is also investigated assuming that the meridional wind, the dynamically important component of the horizontal wind at Gale, anomalies with respect to the daily mean can be approximated by a sinusoidal function as they typically oscillate between positive (south to north) and negative (north to south) values that correspond to upslope/downslope or downslope/upslope regimes along the crater rim and Mount Sharp slopes and the dichotomy boundary. The smallest magnitudes are found in the northern crater floor in a region that comprises Bradbury Landing, in particular at Ls 90° when they are less than 1 m s−1, indicating very little lateral mixing with outside air. The largest amplitudes occur in the south-western portions of the crater where they can exceed 20 m s−1. Should the slope flows along the crater rims interact with the dichotomy boundary flow, which is more likely at Ls 270° and very unlikely at Ls 90°, they are likely to interact constructively for a few hours from late evening to nighttime (∼17-23 LMST) and from pre-dawn early morning (∼5-11 LMST) hours at the norther crater rim and destructively at night (∼22-23 LMST) and in the morning (∼10-11 LMST) at the southern crater rim.

    We conclude that a better understanding of the PBL and circulation dynamics has important implications for the variability of the concentration of dust, non-condensable and trace gases at the bottom of other craters on Mars as mixing with outside air can be achieved vertically, through changes in the PBL depth, and laterally, by the transport of air into and out of the crater.

  • 157.
    Forsberg, Fredrik
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Providing Air Traffic Control Services for Small Unmanned Aircraft Through LTE2016Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
  • 158.
    Freissinet, C.
    et al.
    Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland.
    Glavin, D.P.
    Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland.
    Mahaffy, P.R.
    Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland.
    Miller, K.E.
    Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge.
    Eigenbrode, J.L.
    Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland.
    Summons, R.E.
    Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge.
    Brunner, A.E.
    Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland.
    Buch, A.
    Laboratoire de Génie des Procédés et les Matériaux, Ecole Centrale Paris.
    Szopa, C.
    Laboratoire Atmosphères, Milieux, Observations Spatiales, Univ. Pierre et Marie Curie, Univ. Versailles Saint-Quentin & CNRS, Paris.
    Archer Jr., P.D.
    Jacobs Technology, NASA Johnson Space Center.
    Franz, H.B.
    Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland.
    Atreya, S.K.
    Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor.
    Brinckerhoff, E.B.
    Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland.
    Cabane, M.
    Laboratoire Atmosphères, Milieux, Observations Spatiales, Univ. Pierre et Marie Curie, Univ. Versailles Saint-Quentin & CNRS, Paris.
    Coll, P.
    Laboratoire Interuniversitaire des Systèmes Atmosphériques, Université Paris-Est Créteil, Univ. Paris Diderot and CNRS.
    Conrad, P.G.
    Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland.
    Marais, D.J. Des
    Exobiology Branch, NASA Ames Research Center, Moffett Field, Kalifornien.
    Dworkin, J.P.
    Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland.
    Fairén, A.G.
    Department of Astronomy, Cornell University, Ithaca, New York.
    François, P.
    Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor.
    Grotzinger, J.P.
    Division of Geological and Planetary Sciences, California Institute of Technology.
    Kashyap, S.
    Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland.
    Kate, I.L. ten
    Earth Sciences Department, Utrecht University.
    Leshin, L.A.
    Department of Earth and Environmental Science and School of Science, Rensselaer Polytechnic Institute, Troy, New York.
    Malespin, C.A.
    Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zorzano, María-Paz
    Centro de Astrobiologia, INTA-CSIC, Madrid.
    Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars2015Inngår i: Journal of Geophysical Research - Planets, ISSN 2169-9097, E-ISSN 2169-9100, Vol. 120, nr 3, s. 495-514Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Sample Analysis at Mars (SAM) instrument [Mahaffy et al., 2012] onboard the Mars Science Laboratory (MSL) Curiosity rover is designed to conduct inorganic and organic chemical analyses of the atmosphere and the surface regolith and rocks to help evaluate the past and present habitability potential of Mars at Gale Crater [Grotzinger et al., 2012]. Central to this task is the development of an inventory of any organic molecules present to elucidate processes associated with their origin, diagenesis, concentration and long-term preservation. This will guide the future search for biosignatures [Summons et al., 2011]. Here we report the definitive identification of chlorobenzene (150–300 parts per billion by weight (ppbw)) and C2 to C4 dichloroalkanes (up to 70 ppbw) with the SAM gas chromatograph mass spectrometer (GCMS), and detection of chlorobenzene in the direct evolved gas analysis (EGA) mode, in multiple portions of the fines from the Cumberland drill hole in the Sheepbed mudstone at Yellowknife Bay. When combined with GCMS and EGA data from multiple scooped and drilled samples, blank runs and supporting laboratory analog studies, the elevated levels of chlorobenzene and the dichloroalkanes cannot be solely explained by instrument background sources known to be present in SAM. We conclude that these chlorinated hydrocarbons are the reaction products of martian chlorine and organic carbon derived from martian sources (e.g. igneous, hydrothermal, atmospheric, or biological) or exogenous sources such as meteorites, comets or interplanetary dust particles.

  • 159.
    Friedman, Jonathan S.
    et al.
    National Astronomy and Ionosphere Center, Arecibo Observatory.
    Teplay, Carig A.
    National Astronomy and Ionosphere Center, Arecibo Observatory.
    Raizada, Shikira
    National Astronomy and Ionosphere Center, Arecibo Observatory.
    Zhou, Qihou H.
    Manufacturing and Mechanical Engineering Department, Miami University.
    Hedin, Jonas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Delgado, Ruben
    University of Puerto Rico, Department of Chemistry.
    Potassium Doppler-resonance lidar for the study of the mesosphere and lower thermosphere at the Arecibo Observatory2003Inngår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 65, nr 16-18, s. 1411-1424Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have developed a lidar to study the temperature structure of the nighttime mesopause region over the Arecibo Observatory (18.35°N, 66.75°W) by measuring the lineshape of the fluorescence spectrum of atomic potassium that is deposited in the mesosphere and lower thermosphere (MLT) by meteors. To demonstrate how the potassium lidar can enhance MLT studies at Arecibo, we show recent results for: (1) comparisons with airglow temperature measurements; (2) simultaneous operations with stratospheric and mesospheric temperature profiling by Rayleigh lidar; (3) simultaneous observations of K, Ca+, and E-region electron density profiles; and (4) occurrences of sporadic K layers, and relationships to sporadic E layers.

  • 160.
    Gao, S-W
    et al.
    Department of Automation, Shanghai Jiaotong University.
    Lin, Chen
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zhang, W-D
    Department of Automation, Shanghai Jiaotong University.
    Enhanced NEH method in solving permutation flow shop problem2007Inngår i: Shanghai Jiaotong University. Journal, ISSN 1007-1172, Vol. 12E, nr 1, s. 47-52Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper proposed an enhanced NEH with full insertion moves to solve the permutation flow shop problem. The characteristics of the original NEH are investigated and analyzed, and it is concluded that the given method would be promising to find better solutions, while the cost would be increased. Fast makespan calculating method and eliminating non-promising permutation policy are introduced to reduce the evaluation effort. The former decreases the time complexity from O(n4m) to O(n3m), which is an acceptable cost for medium and small size instances considering the obtained solution quality. The results from computational experience show that the latter also can eliminate a lot of non-promising solutions.

  • 161.
    Garcia Hernandez, Juan Camilo
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Development of a Class D motor amplifier for a next-generation mechanism control electronics2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This thesis was written at Airbus DS GmbH in Friedrichshafen, Germany, as part of a project which aims to develop a new generation of class-D power amplification circuits for sinusoidal commutating motors controlling the movement of different mechanisms in satellites. Currently used topologies have disadvantages such as high power loss, analog controlling and high degree of signal distortion.

    This work first simulates available topologies which were previously developed by the company in order to compare them and build a trade-off list so the most suitable circuit is selected. Then, by further simulating and analysis several improvements to the circuit are suggested and a final schematic is developed including an analogue-to-digital converter and a total of three phases to power a motor. After a demonstrator circuit was designed and built, it was tested by using an external real time target machine to generate the corresponding PWM signals in correspondence to a controlling signal generated via Simulink.

    The final product of this thesis confirmed the simulation results such as an improved signal quality at higher frequencies in comparison to an available measurement from a previous generation circuit. The flexibility of the topology as well as the possibility of implementing a digital control was also confirmed during this phase of the project. Upon further work, the dimensioning of the output low pass filter should be improved and a digital PID controller should be implemented in the controlling FPGA.

    NOTE: This version of the Master Thesis deviates from the formal original  submitted for examination in order not to disclose confidential information of Airbus DS GmbH. All positions in the document, where additional information was removed are properly identified. This document can be published according to the general rules of the Julius-Maximilians-Universität Würzburg and the Lulea University of Technology.

  • 162.
    Garcia, Laura
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    UKF-SLAM Implementation for the Optical Navigation System of a Lunar Lander2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 163.
    Garg, Kanika
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. kanika.garg@ltu.se .
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Aerobot design for planetary explorations2016Inngår i: AIAA Space and Astronautics Forum and Exposition, SPACE 2016, American Institute of Aeronautics and Astronautics, 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper studies the design of planetary aerobots with different types and shapes under various atmospheric conditions. The design framework and specifications are discussed. The development of a simulation tool is described, which is used for analyzing the behaviour of aerobots on Venus, Mars and Titan. The software is verified through the comparison of its performance with some experimental data as well as the state-of-the-art simulation tools. Based on the simulation results, some recommendations are made for different aerobot exploration missions

  • 164.
    Gasteiger, J.
    et al.
    Meteorologisches Institut, Ludwig-Maximilians-Universität.
    Emde, C.
    Meteorologisches Institut, Ludwig-Maximilians-Universität.
    Mayer, B.
    Meteorologisches Institut, Ludwig-Maximilians-Universität.
    Buras, R.
    Meteorologisches Institut, Ludwig-Maximilians-Universität.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Lemke, Oliver
    Representative wavelengths absorption parameterization applied to satellite channels and spectral bands2014Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 148, s. 99-115Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Accurate modeling of wavelength-integrated radiative quantities, e.g. integrated over a spectral band or an instrument channel response function, requires computations for a large number of wavelengths if the radiation is affected by gas absorption which typically comprises a complex line structure. In order to increase computational speed of modeling radiation in the Earth׳s atmosphere, we parameterized wavelength-integrals as weighted means over representative wavelengths. We parameterized spectral bands of different widths (1 cm−1, 5 cm−1, and 15 cm−1) in the solar and thermal spectral range, as well as a number of instrument channels on the ADEOS, ALOS, EarthCARE, Envisat, ERS, Landsat, MSG, PARASOL, Proba, Sentinel, Seosat, and SPOT satellites. A root mean square relative deviation lower than 1% from a “training data set” was selected as the accuracy threshold for the parameterization of each band and channel. The training data set included high spectral resolution calculations of radiances at the top of atmosphere for a set of highly variable atmospheric states including clouds and aerosols. The gas absorption was calculated from the HITRAN 2004 spectroscopic data set and state-of-the-art continuum models using the ARTS radiative transfer model. Three representative wavelengths were required on average to fulfill the accuracy threshold. We implemented the parameterized spectral bands and satellite channels in the uvspec radiative transfer model which is part of the libRadtran software package. The parameterization data files, including the representative wavelengths and weights as well as lookup tables of absorption cross sections of various gases, are provided at the libRadtran webpage.In the paper we describe the parameterization approach and its application. We validate the approach by comparing modeling results of parameterized bands and channels with results from high spectral resolution calculations for atmospheric states that were not part of the training data set. Irradiances are not only compared at the top of atmosphere but also at the surface for which this parameterization approach was not optimized. It is found that the parameterized bands and channels provide a good compromise between computation time requirements and uncertainty for typical radiative transfer problems. In particular for satellite radiometer simulations the computation time requirement and the parameterization uncertainty is low. Band-integrated irradiances at any level as well as heating and cooling rates below 20 km can also be modeled with low uncertainty.

  • 165.
    Gellert, Uwe
    et al.
    Universität Hamburg, Freie Universität Berlin.
    III, Benton Clark
    Space Science Institute, Boulder, Colorado.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    In Situ Compositional Measurements of Rocks and Soils with the Alpha Particle X-ray Spectrometer on NASA's Mars Rovers2015Inngår i: Elements, ISSN 1811-5209, E-ISSN 1811-5217, Vol. 11, nr 1, s. 39-44Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Alpha Particle X-ray Spectrometer (APXS) is a soda can–sized, arm-mounted instrument that measures the chemical composition of rocks and soils using X-ray spectroscopy. It has been part of the science payload of the four rovers that NASA has landed on Mars. It uses 244Cm sources for a combination of PIXE and XRF to quantify 16 elements. So far, about 700 Martian samples from about 50 km of combined traverses at the four landing sites have been documented. The compositions encountered range from unaltered basaltic rocks and extensive salty sandstones to nearly pure hydrated ferric sulfates and silica-rich subsurface soils. The APXS is used for geochemical reconnaissance, identification of rock and soil types, and sample triage. It provides crucial constraints for use with the mineralogical instruments. The APXS data set allows the four landing sites to be compared with each other and with Martian meteorites, and it provides ground truth measurements for comparison with orbital observations.

  • 166.
    Georgieva, Iskra
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Searching for Exoplanets in K2 Data2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The field of extrasolar planets is undoubtedly one of the most exciting and fast-moving in astronomy. Thanks to the Kepler Space Telescope, which has given us the Kepler and K2 missions, we now have thousands of planets to study and thousands more candidates waiting to be confirmed.For this thesis work, I used K2 data in the form of stellar light curves for Campaign 15 – the 15th observation field of this mission – to search for transiting exoplanets. I present one way to produce a viable list of planetary candidates, which is the first step to exoplanet discovery. I do this by first applying a package of subroutines called EXOTRANS to the light curves. EXOTRANS uses two wavelet-based filter routines: VARLET and PHALET. VARLET is used to remove stellar variability and abrupt discontinuities in the light curve. Since a transit appears box-like, EXOTRANS utilises a box-fitting least-squares algorithm to extract the transit event by fitting a square box. PHALET removes disturbances of known frequencies (and their harmonics) and is used to search the light curve for additional planets. Once EXOTRANS finishes its run, I examine the resulting plots and flag the ones, which contain a transit feature that does not appear to be a false positive. I then perform calculations on the shortlisted candidates to further refine their quality. This resulted in a list of 30 exoplanet candidates. Finally, for eight of them, I used a light curve detrending routine (Exotrending) and another software package, Pyaneti, for transit data fitting. Pyaneti uses MCMC sampling with a Bayesian approach to derive the most accurate orbital and candidate parameters. Based on these estimates and combined with stellar parameters from the Ecliptic Plane Input Catalogue, I comment on the eight candidates and their host stars.However, these comments are only preliminary and speculative until follow-up investigation has been conducted. The most widely used method to do this is the radial velocity method, through which more detailed information is obtained about the host star and in turn, about the candidate. This information, specifically the planetary mass, allows for the bulk density to be estimated, which can give indication about a planet’s composition.Although the Kepler Space Telescope is at the end of its life, new missions with at least a partial focus on exoplanets, are either ongoing (Transiting Exoplanets Survey Satellite – TESS) or upcoming (Characterising Exoplanets Satellite – CHEOPS, James Webb Space Telescope – JWST, Planetary Transits and Oscillations – PLATO). They will add thousands of new planets, providing unprecedented accuracy on the transit parameters and will make significant advances in the field of exoplanet characterisation. The methods used in this work are as applicable to these missions as they have been for the now retired Convection, Rotation et Transits planétaires (CoRoT) – the first space mission dedicated to exoplanet research, and Kepler.

  • 167.
    Girard, Justin
    et al.
    Institute for Aerospace Studies, University of Toronto.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A robust approach to robot team learning2016Inngår i: Autonomous Robots, ISSN 0929-5593, E-ISSN 1573-7527, Vol. 40, nr 8, s. 1441-1457Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The paper achieves two outcomes. First, it summarizes previous work on concurrent Markov decision processes (CMDPs) currently demonstrated for use with multi-agent foraging problems. When using CMDPs, each agent models the environment using two Markov decision process (MDP). The two MDPs characterize a multi-agent foraging problem by modeling both a single-agent foraging problem, and multi-agent task allocation problem, for each agent. Second, the paper studies the effects of state uncertainty on a heterogeneous robot team that utilizes the aforementioned CMDP modelling approach. Furthermore, the paper presents a method to maintain performance despite state uncertainty. The resulting robust concurrent individual and social learning (RCISL) mechanism leads to an enhanced team learning behaviour despite state uncertainty. The paper analyzes the performance of the concurrent individual and social learning mechanism with and without a particle filter for a heterogeneous foraging scenario. The RCISL mechanism confers statistically significant performance improvements over the CISL mechanism

  • 168.
    Girard, Justin
    et al.
    Institute for Aerospace Studies, University of Toronto.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Concurrent Markov decision processes for robot team learning2015Inngår i: Engineering applications of artificial intelligence, ISSN 0952-1976, E-ISSN 1873-6769, Vol. 39, s. 223-234, artikkel-id 12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Multi-agent learning, in a decision theoretic sense, may run into deficiencies if a single Markov decision process (MDP) is used to model agent behaviour. This paper discusses an approach to overcoming such deficiencies by considering a multi-agent learning problem as a concurrence between individual learning and task allocation MDPs. This approach, called Concurrent MDP (CMDP), is contrasted with other MDP models, including decentralized MDP. The individual MDP problem is solved by a Q-Learning algorithm, guaranteed to settle on a locally optimal reward maximization policy. For the task allocation MDP, several different concurrent individual and social learning solutions are considered. Through a heterogeneous team foraging case study, it is shown that the CMDP-based learning mechanisms reduce both simulation time and total agent learning effort.

  • 169.
    Granvik, Mikael
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Department of Physics, University of Helsinki.
    Brown, Peter
    Department of Physics and Astronomy, University of Western Ontario.
    Identification of meteorite source regions in the solar system2018Inngår i: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 311, s. 271-287Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Over the past decade there has been a large increase in the number of automated camera networks that monitor the sky for fireballs. One of the goals of these networks is to provide the necessary information for linking meteorites to their pre-impact, heliocentric orbits and ultimately to their source regions in the solar system. We re-compute heliocentric orbits for the 25 meteorite falls published to date from original data sources. Using these orbits, we constrain their most likely escape routes from the main asteroid belt and the cometary region by utilizing a state-of-the-art orbit model of the near-Earth-object population, which includes a size-dependence in delivery efficiency. While we find that our general results for escape routes are comparable to previous work, the role of trajectory measurement uncertainty in escape-route identification is explored for the first time. Moreover, our improved size-dependent delivery model substantially changes likely escape routes for several meteorite falls, most notably Tagish Lake which seems unlikely to have originated in the outer main belt as previously suggested. We find that reducing the uncertainty of fireball velocity measurements below  ∼ 0.1 km/s does not lead to reduced uncertainties in the identification of their escape routes from the asteroid belt and, further, their ultimate source regions. This analysis suggests that camera networks should be optimized for the largest possible number of meteorite recoveries with measured speed precisions of order 0.1 km/s.

  • 170.
    Grigat, Felix
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. ONERA.
    Optimizing the architecture of the Salammbô-EnKF data assimilation tool for radiation belt modeling2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 171.
    Grosse, Christian
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Development of a Star Camera Algorithm for Calculating thePosition on Earth and Mars (VaMEx DLR)2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Within the scope of the Valles Marineris Explorer mission of the German Aerospace Center(DLR), the position of a ground vehicle on Mars needs to be determined. Due to the fact thatMars has no global magnetic field and no positioning system like Earth, a facility independentsystem is necessary. In this context, a star camera based positioning system shall be developed.The subject of this thesis is the development, implementation and verification of a star camerabased transformation algorithm for calculating the latitudinal and longitudinal position on Mars.In addition, an Earth based transformation algorithm is developed, implemented and evaluated fortesting purposes, that is for testing the hardware for the mission under real conditions on Earth.The thesis gives an insight into the fundamental theory of transformation algorithms commonlyused for the transformation between celestial and planet coordinate systems. A self-developedtransformation algorithm is presented which is able to transform a tilted star vector in TopocentricHorizon Coordinate System into observer longitude and latitude position. Moreover, themodular implementation in MATrix LABoratory (MATLAB) and Realtime Onboard DependableOperating System (RODOS) is described in detail. In the further course of the thesis the results ofdifferent test scenarios are outlined and evaluated. The overall results are eventually discussed regardingtheir implications for the mission and subsequently, suggestions for further improvementof the algorithm are made.

  • 172.
    Grotzinger, J.P.
    et al.
    California Institute of Technology, Pasadena, Division of Geological and Planetary Sciences, California Institute of Technology.
    Crisp, J.A.
    Indiana University, Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Vasavada, Ashwin
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Curiosity's Mission of Exploration at Gale Crater, Mars2015Inngår i: Elements, ISSN 1811-5209, E-ISSN 1811-5217, Vol. 11, nr 1, s. 19-26Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Landed missions to the surface of Mars have long sought to determine the material properties of rocks and soils encountered during the course of surface exploration. Increasingly, emphasis is placed on the study of materials formed or altered in the presence of liquid water. Placed in the context of their geological environment, these materials are then used to help evaluate ancient habitability. The Mars Science Laboratory mission—with its Curiosity rover—seeks to establish the availability of elements that may have fueled microbial metabolism, including carbon, hydrogen, sulfur, nitrogen, phosphorus, and a host of others at the trace element level. These measurements are most valuable when placed in a geological framework of ancient environments as interpreted from mapping, combined with an understanding of the petrogenesis of the igneous rocks and derived sedimentary materials. In turn, the analysis of solid materials and the reconstruction of ancient environments provide the basis to assess past habitability.

  • 173.
    Grulich, Maria
    et al.
    Technische Universität München.
    Conte, Davide
    The Pennsylvania State University.
    Borg, Kyle
    University of Colorado, Boulder.
    Burg, Alexander
    George Washington University.
    Burgoyne, Hayden
    California Institute of Technology.
    Celik, Onur
    School of Aerospace, Transport and Manufacturing, Cranfield University.
    Kraetzig, Benjamin
    Neptec Design Group, Atlas Building (R27), Harwell Campus Didcot, Fermi Avenue, Oxfordshire.
    Meskoob, Behnoosh
    Electrical and Electronics Faculty, Istanbul Technical University, Maslak.
    Tió, Meritxell Viñas
    Thales Alenia Space Cannes, 5 Allée des Gabians, Cannes.
    Yesil, Ali
    Institute of Space Systems, University of Stuttgart.
    Heizmann, Sören
    Universität Stuttgart.
    Scherrmann, Marcel
    Institute of Space Systems, University of Stuttgart.
    Laudan, Katarina
    Technical University Berlin.
    Pérez, Ana Alexandra
    Universidad Simón Bolívar, Sartenejas, Caracas.
    Roos, Tobias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Weisser, Constantin
    Massachusetts Institute of Technology.
    Next - Exploration universal station (NEXUS)2016Inngår i: Proceedings of the International Astronautical Congress, IAC, 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

     From July 25 to August 1, 2015 the Space Station Design Workshop (SSDW) was held at the University of Stuttgart in Germany with students coming from around the world. During the SSDW the participants where challenged to develop a concept for a new international platform like the International Space Station (ISS) for future space research. This paper discuss the Preliminary Design Document of the architectural design, deployment strategy and operational phase of NEXUS: the Next EX-ploration Universal Station, an international crewed space platform in cis-lunar space to support the current vision for future deep space exploration. This station is designed to be modular, extensible, sustainable and serves a number of novel applications, including unique research, supporting current and future robotic and human planetary exploration, and providing a platform for international cooperation and commercial development. This space station will be the center of space exploration during its operation and will dramatically enhance the opportunities for every partner to explore the unknown and new locations beyond Low Earth Orbit. The world has successfully collaborated for many years at the ISS. However, the ISS is only currently supported through mid-2020s. The next step is to further the research and exploration done in space and provide an intermediate staging location for missions beyond Earths sphere of influence. NEXUS is located in cis-lunar space, in a halo orbit around the Earth-Moon Libration Point 2 (EML2). While the priorities of potential international partners are extremely varied, NEXUS location enhances and supports the vision of nearly every international space agency and commercial companies. The station offers numerous opportunities for research and technology testing in space and on the Moon. The overall mission architecture is separated into two phases: the construction phase and the operations phase. In order to align with the end of the ISS, the construction will begin in 2024. The construction phase would last 6 years during which the various station modules are sent to EML2 using heavy lift launchers such as the SLS Block 1 and 1B through weak stability boundary trajectories. The station will become fully operational in 2030 and will receive supplies from Earth by using a solar electric tug which would taxi supplies from Earth to NEXUS. NEXUS will be used as an intermediate location for human and robotic missions to explore the Moon, Mars, and other destinations in our Solar System

  • 174.
    Guha, Yash
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Investigation of progressive damage mechanisms in aerospace grade composites2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 175.
    Guldevall, Peter
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Development of an FPGA based Trigger for Slow Moving Events for the EUSO-TA Telescope2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 176.
    Gultepe, Ismail
    et al.
    Cloud Physics and Severe Weather Research Section, Environment Canada.
    Kuhn, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Pavolonis, Michael J.
    NOAA, NESDIS, Madison, WI.
    Calvert, C.
    CIMSS, University of Wisconsin-Madison, Madison, WI.
    Gurka, James J.
    NOAA, NESDIS, Greenbelt, MD.
    Heymsfield, Andrew J.
    NCAR, Boulder, Colorado.
    Liu, P.S.K.
    Cloud Physics and Severe Weather Research Section, Environment Canada.
    Zhou, B.
    I.M. Systems Group, NOAA/NWS/NCEP, Camp Springs, MD.
    Ware, Randolph H.
    Radiometrics Corporation, CIRES, University of Colorado, Boulder, CO.
    Ferrier, Brad Schoenberg
    I.M. Systems Group, NOAA/NWS/NCEP, Camp Springs, MD.
    Milbrandt, Jason A.
    RPN, CMC, Environment Canada.
    Bernstein, Ben C.
    Leading Edge Atmospherics, Boulder, CO.
    Ice fog in arctic during fram-ice fog project aviation and nowcasting applications2014Inngår i: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 95, nr 2, s. 211-226Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Increased understanding of ice fog microphysics can improve frost and ice fog prediction using forecast models and remote-sensing retrievals, thereby reducing potential hazards to aviation

  • 177.
    Gultepe, Ismail
    et al.
    Cloud Physics and Severe Weather Research Section, Environment Canada.
    Zhou, B.
    I.M. Systems Group, NOAA/NWS/NCEP, Camp Springs, MD.
    Milbrandt, Jason A.
    RPN, CMC, Environment Canada.
    Bott, A.
    Meteorolooieches lnstitut, University of Bonn.
    Li, Y.
    Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing.
    Heymsfield, Andrew J.
    National Center for Atmospheric Research, Boulder, Colorado.
    Ferrier, Brad Schoenberg
    I.M. Systems Group, NOAA/NWS/NCEP, Camp Springs, MD.
    Ware, Randolph H.
    Radiometrics Corporation, CIRES, University of Colorado, Boulder, CO.
    Pavolonis, Michael J.
    NOAA, NESDIS, Madison, WI.
    Kuhn, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Gurka, James J.
    NOAA, NESDIS, Greenbelt, MD.
    Liu, P.
    Cloud Physics and Severe Weather Research Section, Environment Canada.
    Cermak, J.
    Ruhr-Universität Bochum, Department of Geography.
    A review on ice fog measurements and modeling2015Inngår i: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895, Vol. 151, s. 2-19Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The rate of weather-related aviation accident occurrence in the northern latitudes is likely 25 times higher than the national rate of Canada. If only cases where reduced visibility was a factor are considered, the average rate of occurrence in the north is about 31 times higher than the Canadian national rate. Ice fog occurs about 25% of the time in the northern latitudes and is an important contributor to low visibility. This suggests that a better understanding of ice fog prediction and detection is required over the northern latitudes. The objectives of this review are the following: 1) to summarize the current knowledge of ice fog microphysics, as inferred from observations and numerical weather prediction (NWP) models, and 2) to describe the remaining challenges associated with measuring ice fog properties, remote sensing microphysical retrievals, and simulating/predicting ice fog within numerical models. Overall, future challenges related to ice fog microphysics and visibility are summarized and current knowledge is emphasized.

  • 178.
    Guzewich, Scott D.
    et al.
    Universities Space Research Association/NASA Goddard Space Flight Center.
    Newman, C.
    Ashima Research Inc.
    De La Torre Juárez, Manuel
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Mason, E.
    Texas A&M University, College Station, TX.
    Battalio, M.
    Texas A&M University, College Station, TX.
    Zorzano Mier, Maria-Paz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Moores, John E.
    Earth and Space Science and Engineering , York University.
    Moore, C.A.
    Earth and Space Science and Engineering , York University.
    Kloos, J.L
    Earth and Space Science and Engineering , York University.
    Martinez, M.D.
    Uni-versity of Michigan, Ann Arbor.
    Smith, M.D.
    NASA Goddard Space Flight Center, Greenbelt.
    The Mars Science Laboratory dust storm campaign2017Konferansepaper (Annet vitenskapelig)
  • 179.
    Guzewich, Scott D.
    et al.
    NASA Goddard Spaceflight Center, Greenbelt, MD.
    Newman, C. E.
    Aeolis Research, Pasadena, CA.
    Smith, M. D.
    NASA Goddard Spaceflight Center, Greenbelt, MD.
    Moores, J. E.
    Department of Earth and Space Science and Engineering, York University, Toronto, ON, Canada.
    Smith, C. L.
    Department of Earth and Space Science and Engineering, York University, Toronto, ON, Canada.
    Moore, C.
    Department of Earth and Space Science and Engineering, York University, Toronto, ON, Canada.
    Richardson, M. I.
    Aeolis Research, Pasadena, CA.
    Kass, D.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA.
    Kleinböhl, A.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA.
    Mischna, M.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA.
    Martín-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Granada, Spain.
    Zorzano Mier, Maria-Paz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Centro de Astrobiología (INTA-CSIC), Torrejón de Ardoz, Madrid, Spain.
    Battalio, M.
    Department of Atmospheric Sciences, Texas A&M University, College Station, TX.
    The Vertical Dust Profile over Gale Crater, Mars2017Inngår i: Journal of Geophysical Research - Planets, ISSN 2169-9097, E-ISSN 2169-9100, Vol. 122, nr 12, s. 2779-2792Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We create a vertically coarse, but complete, vertical profile of dust mixing ratio from the surface to the upper atmosphere over Gale Crater, Mars, using the frequent joint atmospheric observations of the orbiting Mars Climate Sounder (MCS) and the Mars Science Laboratory (MSL) Curiosity rover. Using these data and an estimate of planetary boundary layer (PBL) depth from the MarsWRF general circulation model, we divide the vertical column into three regions. The first region is the Gale Crater PBL, the second is the MCS-sampled region, and the third is between these first two. We solve for a well-mixed dust mixing ratio within this third (middle) layer of atmosphere to complete the profile.

    We identify a unique seasonal cycle of dust within each atmospheric layer. Within the Gale PBL, dust mixing ratio maximizes near southern hemisphere summer solstice (Ls = 270°) and minimizes near winter solstice (Ls = 90-100°) with a smooth sinusoidal transition between them. However, the layer above Gale Crater and below the MCS-sampled region more closely follows the global opacity cycle and has a maximum in opacity near Ls = 240° and exhibits a local minimum (associated with the “solsticial pause” in dust storm activity) near Ls = 270°. With knowledge of the complete vertical dust profile, we can also assess the frequency of high-altitude dust layers over Gale. We determine that 36% of MCS profiles near Gale Crater contain an “absolute” high-altitude dust layer wherein the dust mixing ratio is the maximum in the entire vertical column.

  • 180.
    Gúrpide Lasheras, Andrés
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Galaxies, High Energy Astrophysics and Cosmology at Institut de Recherche en Astrophysique et Planétologie.
    Investigating super-Eddington accretion flows in Ultraluminous X-ray sources2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    It is now widely known that most of the large galaxies we observe (e.g. the Milky Way) host in their center a supermassive black hole ($10^{6}-10^{9}$ $M_\odot$). Several relationships between the central black hole mass and the properties of the stars in the central part of the galaxy have been established in the past 3 decades indicating that the central black hole is able to efficiently structure the matter around it due to episodes of accretion of matter onto the black hole. Recent infrared and optical sky surveys have detected supermassive black holes with masses around $10^{8-9}$ $M_\odot$ when the universe was less than a tenth of its current age and current theories have difficulties explaining how such massive objects could have formed over such short timescales. The goal of the present work is to shed light on the properties of a still largely unknown extreme accretion regime, the so called super-Eddington accretion regime. If such accretion regime could be sustained over sufficient timescales, it could play an important role in both the rapid growth of supermassive black holes as well as its co-evolution with its host galaxy. The aim of this work is therefore to apply high resolution spectroscopy to Ultraluminous X-ray sources in order to identify narrow spectral features to derive constrains on the outflows expected from super-Eddington accreting sources using data from the XMM-Newton observatory. For this purpose I developed a framework to analyse low count background dominated spectra that uses a Monte Carlo approach to detect these narrow features. After analysis of the source Holmberg II X-1, I identify 7 unresolved discrete features with a 3$\sigma$ confidence level that can be tentatively identified with ionic species. Furthermore, the instrumental resolution allows us to put upper limits on the broadening of the lines. This findings will allow us to probe the properties of the outflows of the super-Eddington regime and by extending the analysis to other sources we will able to characterize the observational properties of this accretion regime.

  • 181.
    Güttler, Johannes
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Field-Site Prototype for HABIT (FSP-HABIT): Characterizing Martian Salts Prior to the ExoMars 2020 Mission2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    One of the major remaining question about Mars is its habitability - if the requirements necessary to allow for life are presently fulfilled. One of the most relevant ingredients for life, as we know it, is water. Indirect evidence of transient liquid water on Mars has been retrieved from both rover [Martín-Torres et al., 2015] and orbiter [Ojha et al., 2015].

    [Martín-Torres et al., 2015] inferred the existence of an active water cycle, driven by chlorate and perchlorate salts, which are commonly found on the Martian surface, and absorb atmospheric water to form stable hydrated compounds and liquid solutions. This happens through a process called deliquescence (absorption of moisture from the atmosphere by the salts and dissolving into a liquid solution). One of the goals of HABIT is to confirm the hypothesis about the water cycle on Mars. HABIT will record the behavior of a selection of salts on Mars, and will also record Martian environmental conditions (UVdose, air and ground temperatures).

    The Field-Site Prototype for HABIT (FSP-HABIT) was the first prototype of HABIT deployed during field-site campaigns. Three campaigns took place during summer 2016: First, a short preparatory campaign in Abisko, Sweden, was carried out. The second campaign took place in Iceland, within the EU COST Action TD1308 ORIGINS (Origins and evolution of life on Earth and in the Universe), and the third campaign was conducted within the NASA Spaceward Bound India Program in Ladakh. After providing the corresponding background on the mission framework and the scientific background, this document covers the mechanical, electrical, and software design of the instrument. Afterwards, the steps taken to test the instrument and their results are covered, followed by a rating of the instrument and ideas for future improvements. Instruments like FSP-HABIT will enable the characterization of hygroscopic salts by their conductivity as liquid brines are good conductors, hydrated salts are poor conductors, and dehydrated salts are insulators. During the field-site campaigns, the measurements of FSP-HABIT were used to characterize the near surface environment by its temperature, pressure and relative humidity. Now, these measurements are available for comparison with microbiological studies of the water, ice and soils to characterize the habitability of the explored site. The lessons learned while designing and building FSP-HABIT can be used to inform the development of further prototypes for space missions such as HABIT.

  • 182.
    Hagen, Christoph
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A Bluetooth based intra-satellite communication system2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This thesis presents a wireless communication system for intra-satellite communication based on Bluetooth Low Energy technology, which can have many benefits regarding the design and operation of satellites. The proposed design based on the nRF53832 chip from Nordic Semiconductor is described, followed by the results of several tests regarding the most important design criteria for its application in small satellites. The tested aspects include the power consumption of the wireless module in different operation modes, which is sufficiently low for the application even in small satellites. Signal strength measurements for various output power settings and obstacles show that reliable communication is possible in a satellite mockup. No packet error was detected, and latencies of less than 30 ms combined with achievable data rates between 200 and 700 kbps should be sufficient for most CubeSat satellites. Additionally, details are given to successfully integrate the chip with existing satellite subsystems. A code library is provided to simplify the communication between the modules, and a concept of a redundant system is established to increase the reliability for critical satellite subsystems. The overall assessment of the technology suggests that the presented system is suitable for in-orbit deployment with the Aalto-3 satellite (currently being developed at Aalto University), which will provide further validation of the technology. 

  • 183.
    Hagos, Tesfamichael Marikos
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Aalto University .
    Estimation of phases for compliant motion: Auto-regressive HMM, multi-class logistic regression, Learning from Demonstration (LfD), Gradient descent optimization,2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 184.
    Hakima, Houman
    et al.
    Institute for Aerospace Studies, University of Toronto .
    Bazzocchi, Michael C. F.
    Institute for Aerospace Studies, University of Toronto.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Institute for Aerospace Studies, University of Toronto.
    A Deorbiter CubeSat for Active Orbital Debris Removal2018Inngår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 61, nr 9, s. 2377-2392Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper introduces a mission concept for active removal of orbital debris based on the utilization of the CubeSat form factor. The CubeSat is deployed from a carrier spacecraft, known as a mothership, and is equipped with orbital and attitude control actuators to attach to the target debris, stabilize its attitude, and subsequently move the debris to a lower orbit where atmospheric drag is high enough for the bodies to burn up. The mass and orbit altitude of debris objects that are within the realms of the CubeSat’s propulsion capabilities are identified. The attitude control schemes for the detumbling and deorbiting phases of the mission are specified. The objective of the deorbiting maneuver is to decrease the semi-major axis of the debris orbit, at the fastest rate, from its initial value to a final value of about 6,471 km (i.e., 100 km above Earth considering a circular orbit) via a continuous low-thrust orbital transfer. Two case studies are investigated to verify the performance of the deorbiter CubeSat during the detumbling and deorbiting phases of the mission. The baseline target debris used in the study are the decommissioned KOMPSAT-1 satellite and the Pegasus rocket body. The results show that the deorbiting times for the target debris are reduced significantly, from several decades to one or two years.

  • 185.
    Hakima, Houman
    et al.
    University of Toronto Institute for Aerospace Studies, 4925 Dufferin Street, Toronto.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Institute for Aerospace Studies, University of Toronto.
    Assessment of active methods for removal of LEO debris2018Inngår i: Acta Astronautica, ISSN 0094-5765, E-ISSN 1879-2030, Vol. 144, s. 225-243Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper investigates the applicability of five active methods for removal of large low Earth orbit debris. The removal methods, namely net, laser, electrodynamic tether, ion beam shepherd, and robotic arm, are selected based on a set of high-level space mission constraints. Mission level criteria are then utilized to assess the performance of each redirection method in light of the results obtained from a Monte Carlo simulation. The simulation provides an insight into the removal time, performance robustness, and propellant mass criteria for the targeted debris range. The remaining attributes are quantified based on the models provided in the literature, which take into account several important parameters pertaining to each removal method. The means of assigning attributes to each assessment criterion is discussed in detail. A systematic comparison is performed using two different assessment schemes: Analytical Hierarchy Process and utility-based approach. A third assessment technique, namely the potential-loss analysis, is utilized to highlight the effect of risks in each removal methods

  • 186.
    Hakima, Houman
    et al.
    University of Toronto Institute for Aerospace Studies, 4925 Dufferin Street, Toronto.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Debris detumbler: An alternative approach to active debris removal2016Inngår i: Proceedings of the International Astronautical Congress, IAC, 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Since the launch of the first artificial satellite, i.e., Sputnik in 1957, several thousand man-made objects have been launched into the Earth orbits, great majority of which remained in their orbit despite the termination of their mission. A number of viable solutions have been suggested in the research community for actively removing the orbital debris, some of which require the capturing of the debris, while others are contactless methods. A challenging aspect of capturing an orbital debris using any method is due to the tumbling motion of the debris. A majority of the suggested methods require zero or very low rates of debris attitude to perform successfully, or need to follow a synchronization phase with the debris before the capturing and removal operation. This is technically costly and challenging, if not infeasible. This paper proposes an alternative approach to orbital debris removal, which can make various state-of-the-art methods of active debris removal perform at lower costs and risks. The approach utilizes one or more detumbler platforms, in the form of miniaturized cubesats, which are de-signed to be lunched from the remover spacecraft, attach to the target debris, and reduce its attitude rate to zero using the onboard attitude determination sensors and control actuators. The paper outlines the operation of debris detumblers. The conceptual design of such platforms is also presented, based on the one- to three-unit cubesat bus and commercial off-the-shelf technologies. Orbital insertion, rendezvous and attachment maneuvers are also discussed. Finally, through simulations the performance of the proposed approach is compared with that of some well-studied methods in various scenarios using several catalogued debris, based on performance metrics such as delta-v, operation time, trajectory simplicity, total thrust, etc

  • 187.
    Hammarsten, Michael
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A statistical study of incoherent scatter plasma line enhancements during the International Polar Year ’07-’08 in Svalbard2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    There was a large radar campaign during 2007 and 2008, the International Polar Year (IPY),and at that time the EISCAT Svalbard Radar was operated and measured the ionosphere continuouslyat most times. This report presents statistical results from an electron enhancementpoint of view. Until now there has been some research into the field and results based on theions in the ionosphere, and the enhancements we refer to as Naturally enhanced ion acousticlines (NEIALs). Plasma line data from May 2007 to February 2008 has been analysed inorder to find and classify enhancements as NEIALs have been classified but with respect tothe electron distribution instead of the ion distribution. A method of detection was developedin order to differentiate the enhancements from the background with a relation between theminimum and maximum power of each measured dump. Results show that there is a largedifference between the downshifted plasma lines and the upshifted plasma lines, both has arange distribution peak at 180 km and the upshifted plasma line has another peak at 230 kmwhich the downshifted plasma line does not. The occurrence rate of the enhancements was1.64 % for the downshifted plasma line and 4.69 % for the upshifted plasma line. Threedifferent types of enhancements are classified using the variance distribution for the peakfrequency of that detected dump, Single, Profile, and Diffuse. The Single enhancements havea bit different spectral, range, and time of day distributions than of the Profile and Diffusedistributions. The Diffuse classifications are mostly wrong classifications and aliasing and itis very similar to Profile enhancements as seen by its distribution.

  • 188.
    Harju, Jorma
    et al.
    Department of Physics, University of Helsinki, Finland; Max-Planck-Institut für extraterrestrische Physik, Garching, Germany.
    Lehtinen, Kimmo
    Finnish Geospatial Research Institute FGI, Masala, Finland.
    Romney, Jonathan
    Long Baseline Observatory, Socorro, USA.
    Petrov, Leonid
    Astrogeo Center, Falls Church, USA.
    Granvik, Mikael
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Department of Physics, University of Helsinki, Finland.
    Muinonen, Karri
    Department of Physics, University of Helsinki; Finnish Geospatial Research Institute FGI, Masala, Finland.
    Bach, Uwe
    Max-Planck-Institut für Radioastronomie, Bonn, Germany.
    Poutanen, Markku
    Finnish Geospatial Research Institute FGI, Masala, Finland.
    Radio Interferometric Observation of an Asteroid Occultation2018Inngår i: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 156, nr 4, s. 1-10, artikkel-id 155Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The occultation of the radio galaxy 0141+268 by the asteroid(372)Palma on 2017 May 15 was observed using sixantennas of the Very Long Baseline Array(VLBA). The shadow of Palma crossed the VLBA station at Brewster,Washington. Owing to the wavelength used, and the size and the distance of the asteroid, a diffraction pattern in theFraunhofer regime was observed. The measurement retrieves both the amplitude and the phase of the diffractedelectromagnetic wave. This is thefirst astronomical measurement of the phase shift caused by diffraction. Themaximum phase shift is sensitive to the effective diameter of the asteroid. The bright spot at the shadow’s center,the so called Arago–Poisson spot, is clearly detected in the amplitude time-series, and its strength is a goodindicator of the closest angular distance between the center of the asteroid and the radio source. A sample ofrandom shapes constructed using a Markov chain Monte Carlo algorithm suggests that the silhouette of Palmadeviates from a perfect circle by 26±13%. The best-fitting random shapes resemble each other, and we suggesttheir average approximates the shape of the silhouette at the time of the occultation. The effective diameterobtained for Palma, 192.1±4.8 km, is in excellent agreement with recent estimates from thermal modeling ofmid-infrared photometry. Finally, our computations show that because of the high positional accuracy, a singleradio interferometric occultation measurement can reduce the long-term ephemeris uncertainty by an order ofmagnitude.

  • 189.
    Helmi, A.
    et al.
    University of Groningen, Kapteyn Astron Institute.
    Granvik, Mikael
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Department of Physics, University of Helsinki.
    Zwitter, T.
    University of Ljubljana, Faculty of Mathematics & Physics.
    Gaia Data Release 2: Kinematics of globular clusters and dwarf galaxies around the Milky Way2018Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 16, nr A12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aims. The goal of this paper is to demonstrate the outstanding quality of the second data release of the Gaia mission and its power for constraining many different aspects of the dynamics of the satellites of the Milky Way. We focus here on determining the proper motions of 75 Galactic globular clusters, nine dwarf spheroidal galaxies, one ultra-faint system, and the Large and Small Magellanic Clouds. Methods. Using data extracted from the Gaia archive, we derived the proper motions and parallaxes for these systems, as well as their uncertainties. We demonstrate that the errors, statistical and systematic, are relatively well understood. We integrated the orbits of these objects in three different Galactic potentials, and characterised their properties. We present the derived proper motions, space velocities, and characteristic orbital parameters in various tables to facilitate their use by the astronomical community. Results. Our limited and straightforward analyses have allowed us for example to (i) determine absolute and very precise proper motions for globular clusters; (ii) detect clear rotation signatures in the proper motions of at least five globular clusters; (iii) show that the satellites of the Milky Way are all on high-inclination orbits, but that they do not share a single plane of motion; (i v) derive a lower limit for the mass of the Milky Way of 9.1(-2.6)(+6.2) x 10(11) M-circle dot based on the assumption that the Leo I dwarf spheroidal is bound; (v) derive a rotation curve for the Large Magellanic Cloud based solely on proper motions that is competitive with line-of-sight velocity curves, now using many orders of magnitude more sources; and (v i) unveil the dynamical effect of the bar on the motions of stars in the Large Magellanic Cloud. Conclusions. All these results highlight the incredible power of the Gaia astrometric mission, and in particular of its second data release.

  • 190.
    Hirschmüller, Korbinian
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Development and Evaluation of a 3D Point Cloud Based Attitude Determination System2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 191.
    Hladký, Maroš
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Julius-Maximilians-University Würzburg, Informatics VII : Robotics and Telematics .
    Vision Based Attitude Control2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The problematics of precise pointing and more specifically an attitude control is present sincethe first days of flight and Aerospace engineering. The precise attitude control is a matter ofnecessity for a great variety of applications. In the air, planes or unmanned aerial vehicles needto be able to orient precisely. In Space, a telescope or a satellite relies on the attitude control toreach the stars or survey the Earth. The attitude control can be based on various principles, pre-calculated variables, and measurements. It is common to use the gyroscope, Sun/Star/horizonsensors for attitude determination. While those technologies are well established in the indus-try, the rise in a computational power and efficiency in recent years enabled processing of aninfinitely more rich source of information - the vision. In this Thesis, a visual system is used forthe attitude determination and is blended together with a control algorithm to form a VisionBased Attitude Control system.A demonstrator is designed, build and programmed for the purpose of Vision Based AttitudeControl. It is based on the principle of Visual servoing, a method that links image measure-ments to the attitude control, in a form of a set of joint velocities. The intermittent steps arethe image acquisition and processing, feature detection, feature tracking and the computationof joint velocities in a closed loop control scheme. The system is then evaluated in a barrage ofpartial experiments.The results show, that the used detection algorithms, Shi&Tomasi and Harris, performequally well in feature detection and are able to provide a high amount of features for tracking.The pyramidal implementation of the Lucas&Kanade tracking algorithm proves to be a capablemethod for a reliable feature tracking, invariant to rotation and scale change. To further evaluatethe Visual servoing a complete demonstrator is tested. The demonstrator shows the capabilityof Visual Servoing for the purpose of Vision Based Attitude Control. An improvement in thehardware and implementation is recommended and planned to push the system beyond thedemonstrator stage into an applicable system.

  • 192.
    Holl, Gerrit
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Microwave and infrared remote sensing of ice clouds: measurements and radiative transfer simulations2011Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This licentiate thesis considers the combination of multiple instruments for remote sensing of the Earth atmosphere from space. The primary focus is on remote sensing of atmospheric ice. Ice clouds are important for the Earth’s radiation budget, but their properties are difficult to measure and therefore poorly known. A better quantification of ice clouds is needed to improve global climate models. This thesis introduces the reader to the subject and describes how to combine measurements and radiative transfer simulations in an attempt to improve our understanding. A major part of this work is the development of a toolkit to find co-incident measurements, or collocations, between any pair of down-looking satellite sensors. Firstly, this toolkit is used to collocate passive microwave and thermal infrared sensors on meteorological satellites with the Cloud Profiling Radar on CloudSat. With the resulting collocated dataset, the Ice Water Path (IWP) signal in passive thermal radiation is studied and an improved IWP retrieval is presented. The toolkit is also used to better characterise the bias between different copies of passive microwave radiometers on-board polar-orbiting operational satellites. For the Atmospheric Radiative Transfer Simulator (ARTS), version 2, an optimised frequency grid for infrared broadband simulations is shown to be applicable for cloudy simulations. This frequency grid can and will be used to study the IWP signal in thermal infrared radiances. An outlook on a comparison between collocations and simulations is presented in the thesis.

  • 193.
    Holl, Gerrit
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Remote sensing of ice clouds: synergistic measurements and radiative transfer simulations2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis primarily considers the spaceborne remote sensing of ice clouds and frozen precipitation. Ice clouds are important for hydrology and for the Earth’s radiation budget, but many properties are difficult to measure, in particular using spaceborne instruments. A better quantification of ice clouds is needed to improve global climate models. This thesis presents steps toward such an improvement.The first part of the thesis introduces topics related to the research presented in the second part, but presents no new scientific results. It gives a brief introduction to the history of atmospheric remote sensing and describes how the different parts of the electromagnetic spectrum can be used actively or passively. Then, it describes why ice clouds are important and what microphysical, optical, and macrophysical properties are used to describe atmospheric ice. Next, it briefly introduces the relevant topics in atmospheric radiative transfer. The first part concludes with a description of various approaches to retrievals, with a particular focus on those applied in this thesis.The second part of the thesis describes new results. The bulk of the new results is described in five peer-reviewed publications, that are appended verbatim.A major part of the work builds on the development of a toolkit to easily find co-incident measurements, or collocations, between any pair of satellite sensors. Four appended articles rely on this toolkit.The first appended article uses the toolkit to obtain collocations between passive microwave and infrared on operational meteorological satellites with the Cloud Profiling Radar on CloudSat. It presents three examples. Firstly, from the collocated dataset and a dataset of synthetic profiles, the article compares the statistical relations between an official CloudSat Ice Water Path (IWP) product and microwave radiances. Secondly, it shows a point-by-point comparison between the same CloudSat IWP product, and an IWP product based on passive microwave. A more sophisticated set of systematic comparisons, including more satellites and sensors, is presented in a dedicated paper. Finally, the first paper provides a first preview of how the collocations can be used to train a new IWP retrieval from passive operational measurements. This too is the topic of a dedicated paper, where solar, terrestrial infrared, and microwave radiances are combined to obtain an improved IWP product from passive operational sensors, by training with an active combined radar-lidar product from CloudSat-CALIPSO.The second appended article also relies on the collocations toolkit. Here, collocations between different copies of identical or very similar microwave sounders are used to assess how the inter-satellite bias depends on radiance and latitude.The remaining two studies described in the thesis do not use existing measurements, but are based on radiative transfer modelling. One attached paper verifies that optimised frequency grids obtained in clear-sky simulations for terrestrial infrared instrument studies, can be applied directly for cloudy simulations. This result is relevant for future studies. Finally, the thesis includes a short study with retrieval simulations for a new sub-millimetre instrument concept.

  • 194.
    Holl, Gerrit
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mendrok, Jana
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Kottayil, Ajil
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Optimised frequency grids for infrared radiative transfer simulations in cloudy conditions2012Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 113, nr 16, s. 2124-2134Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper shows that radiometer channel radiances for cloudy atmospheric conditions can be simulated with an optimised frequency grid derived under clear-sky conditions. A new clear-sky optimised grid is derived for AVHRR channel . For HIRS channel 11 and AVHRR channel 5, radiative transfer simulations using an optimised frequency grid are compared with simulations using a reference grid, where the optimised grid has roughly 100–1000 times less frequencies than the full grid. The root mean square error between the optimised and the reference simulation is found to be less than 0.3 K for both comparisons, with the magnitude of the bias less than 0.03 K. The simulations have been carried out with the radiative transfer model Atmospheric Radiative Transfer Simulator (ARTS), version 2, using a backward Monte Carlo module for the treatment of clouds. With this module, the optimised simulations are more than 10 times faster than the reference simulations. Although the number of photons is the same, the smaller number of frequencies reduces the overhead for preparing the optical properties for each frequency. With deterministic scattering solvers, the relative decrease in runtime would be even more. The results allow for new radiative transfer applications, such as the development of new retrievals, because it becomes much quicker to carry out a large number of simulations. The conclusions are applicable to any downlooking infrared radiometer.

  • 195. Holl, Gerrit
    et al.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Rydberg, B.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Jiménez, C.
    Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique, Centre National de la Recherche Scientifique, Observatoire de Paris.
    Collocating satellite-based radar and radiometer measurements: methodology and usage examples2010Inngår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 3, nr 3, s. 693-708Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Collocations between two satellite sensors are occasions where both sensors observe the same place at roughly the same time. We study collocations between the Microwave Humidity Sounder (MHS) on-board NOAA-18 and the Cloud Profiling Radar (CPR) on-board CloudSat. First, a simple method is presented to obtain those collocations and this method is compared with a more complicated approach found in literature. We present the statistical properties of the collocations, with particular attention to the effects of the differences in footprint size. For 2007, we find approximately two and a half million MHS measurements with CPR pixels close to their centrepoints. Most of those collocations contain at least ten CloudSat pixels and image relatively homogeneous scenes. In the second part, we present three possible applications for the collocations. Firstly, we use the collocations to validate an operational Ice Water Path (IWP) product from MHS measurements, produced by the National Environment Satellite, Data and Information System (NESDIS) in the Microwave Surface and Precipitation Products System (MSPPS). IWP values from the CloudSat CPR are found to be significantly larger than those from the MSPPS. Secondly, we compare the relation between IWP and MHS channel 5 (190.311 GHz) brightness temperature for two datasets: the collocated dataset, and an artificial dataset. We find a larger variability in the collocated dataset. Finally, we use the collocations to train an Artificial Neural Network and describe how we can use it to develop a new MHS-based IWP product. We also study the effect of adding measurements from the High Resolution Infrared Radiation Sounder (HIRS), channels 8 (11.11 mu m) and 11 (8.33 mu m). This shows a small improvement in the retrieval quality. The collocations described in the article are available for public use

  • 196.
    Holl, Gerrit
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Rydberg, Bengt
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Jiménez, Carlos
    LERMA, CNRS, Observatoire de Paris, Paris, France.
    Collocating satellite-based radar and radiometer measurements –: methodology and usage examples2010Konferansepaper (Annet vitenskapelig)
  • 197.
    Holl, Gerrit
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Rydberg, Bengt
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Jiménez, Carlos
    Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique, Centre National de la Recherche Scientifique, Observatoire de Paris.
    Collocating satellite-based radar and radiometer measurements: methodology and usage examples2011Inngår i: Proceedings of the ESA Living Planet Symposium, European Space Agency, ESA , 2011Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Collocations between two satellite sensors are occasions where both sensors observe the same place at roughly the same time. We study collocations between the Microwave Humidity Sounder (MHS) on-board NOAA-18 and the Cloud Profiling Radar (CPR) on-board CloudSat. We present some statistical properties of the collocations. For 2007, we find approximately two and a half million MHS measurements with CPR pixels close to their centrepoints. We present some possible applications. We use the collocations to validate an operational Ice Water Path (IWP) product from MHS measurements, produced by the National Environment Satellite, Data and Information System (NESDIS) in the Microwave Surface and Precipitation Products System (MSPPS). IWP values from the CloudSat CPR are found to be significantly larger than those from the MSPPS. Finally, we use the collocations to train an Artificial Neural Network and describe how we can use it to develop a new MHS-based IWP product. The collocations described in the article are available for public use.

  • 198.
    Holl, Gerrit
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Rydberg, Bengt
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Jiménez, Carlos
    LERMA, CNRS, Observatoire de Paris, Paris, France.
    Collocating satellite-based radar and radiometer measurements: methodology and usage examples2010Konferansepaper (Annet vitenskapelig)
  • 199.
    Holl, Gerrit
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Rydberg, Bengt
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Jiménez, Carlos
    LERMA, CNRS, Observatoire de Paris, Paris, France.
    Hunting ice clouds: quantifying ice from passive infrared and microwave measurements by collocating with the CloudSat radar2011Konferansepaper (Annet vitenskapelig)
  • 200.
    Holl, Gerrit
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Eliasson, Salomon
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mendrok, Jana
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    SPARE-ICE: Synergistic ice water path from passive operational sensors2014Inngår i: Journal of Geophysical Research: Atmospheres, ISSN 2169-8996, Vol. 119, nr 3, s. 1504-1523Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article presents SPARE-ICE, the Synergistic Passive Atmospheric Retrieval Experiment-ICE. SPARE-ICE is the first Ice Water Path (IWP) product combining infrared and microwave radiances. By using only passive operational sensors, the SPARE-ICE retrieval can be used to process data from at least the NOAA 15 to 19 and MetOp satellites, obtaining time series from 1998 onward. The retrieval is developed using collocations between passive operational sensors (solar, terrestrial infrared, microwave), the CloudSat radar, and the CALIPSO lidar. The collocations form a retrieval database matching measurements from passive sensors against the existing active combined radar-lidar product 2C-ICE. With this retrieval database, we train a pair of artificial neural networks to detect clouds and retrieve IWP. When considering solar, terrestrial infrared, and microwave-based measurements, we show that any combination of two techniques performs better than either single-technique retrieval. We choose not to include solar reflectances in SPARE-ICE, because the improvement is small, and so that SPARE-ICE can be retrieved both daytime and nighttime. The median fractional error between SPARE-ICE and 2C-ICE is around a factor 2, a figure similar to the random error between 2C-ICE ice water content (IWC) and in situ measurements. A comparison of SPARE-ICE with Moderate Resolution Imaging Spectroradiometer (MODIS), Pathfinder Atmospheric Extended (PATMOS-X), and Microwave Surface and Precipitation Products System (MSPPS) indicates that SPARE-ICE appears to perform well even in difficult conditions. SPARE-ICE is available for public use.

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