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  • 301.
    Nilsson, Hans
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Hamrin, Maria
    Department of Physics, Umeå University.
    Pitkänen, Timo
    Department of Physics, Umeå University.
    Karlsson, Tomas
    Space and Plasma Physics, School of Electrical Engineering Royal Institute of Technology Stockholm.
    Slapak, Rikard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Andersson, Laila O.
    Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado.
    Gunell, Herbert
    Swedish Institute of Space Physics / Institutet för rymdfysik , Belgian Institute for Space Aeronomy, Brussels.
    Schillings, Audrey
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Vaivads, Andris
    Swedish Institute of Space Physics, Uppsala.
    Oxygen ion response to proton bursty bulk flows2016Ingår i: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, nr 8, s. 7535-7546Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have used Cluster spacecraft data from the years 2001 to 2005 to study how oxygen ions respond to bursty bulk flows (BBFs) as identified from proton data. We here define bursty bulk flows as periods of proton perpendicular velocities more than 100 km/s and a peak perpendicular velocity in the structure of more than 200 km/s, observed in a region with plasma beta above 1 in the near-Earth central tail region. We find that during proton BBFs only a minor increase in the O+ velocity is seen. The different behavior of the two ion species is further shown by statistics of H+ and O+ flow also outside BBFs: For perpendicular earthward velocities of H+ above about 100 km/s, the O+ perpendicular velocity is consistently lower, most commonly being a few tens of kilometers per second earthward. In summary, O+ ions in the plasma sheet experience less acceleration than H+ ions and are not fully frozen in to the magnetic field. Therefore, H+ and O+ motion is decoupled, and O+ ions have a slower earthward motion. This is particularly clear during BBFs. This may add further to the increased relative abundance of O+ ions in the plasma sheet during magnetic storms. The data indicate that O+ is typically less accelerated in association with plasma sheet X lines as compared to H+.

  • 302.
    Nilsson, Hans
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Slapak, Rikard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Barghouthi, I.A.
    Department of Physics, Al-Quds University, Jerusalem.
    Eriksson, A.I.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    André, M.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Hot and cold ion outflow: Spatial distribution of ion heating2012Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ions apparently emanating from the same source, the ionospheric polar cap, can either end up as energized to keV energies in the high-altitude cusp/mantle, or appear as cold ions in the magnetotail lobes. We use Cluster observations of ions and wave electric fields to study the spatial variation of ion heating in the cusp/mantle and polar cap. The average flow direction in a simplified cylindrical coordinate system is used to show approximate average ion flight trajectories, and discuss the temperatures, fluxes and wave activity along some typical trajectories. It is found that it is suitable to distinguish between cusp, central and nightside polar cap ion outflow trajectories, though O+ heating is mainly a function of altitude. Furthermore we use typical cold ion parallel velocities and the observed average perpendicular drift to obtain average cold ion flight trajectories. The data show that the cusp is the main source of oxygen ion outflow, whereas a polar cap source would be consistent with our average outflow paths for cold ions observed in the lobes. A majority of the cusp O+ flux is sufficiently accelerated to escape into interplanetary space. A scenario with significant oxygen ion heating in regions with strong magnetosheath origin ion fluxes, cold proton plasma dominating at altitudes below about 8 RE in the polar cap, and most of the cusp oxygen outflow overcoming gravity and flowing out in the cusp and mantle is consistent with our observations.

  • 303.
    Nilsson, Hans
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Wieser, Gabriella Stenberg
    Swedish Institute of Space Physics.
    Behar, Etienne
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Wedlund, Cyril Simon
    Aalto University, School of Electrical Engineering, Department of Radio Science and Engineering.
    Gunell, Herbert
    Belgian Institute for Space Aeronomy, Brussels.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics.
    Lundin, Rickard
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Barabash, Stas
    Swedish Institute of Space Physics.
    Wieser, Martin
    Swedish Institute of Space Physics.
    Carr, Chris
    Imperial College London.
    Cupido, Emanuele
    Imperial College London.
    Burch, James L.
    Southwest Research Institute, 6220 Culebra Road, San Antonio.
    Fedorov, Andrei
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Savaud, Jean-André
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Koskinen, Hannu
    Department of Physics, University of Helsinki.
    Kallio, Esa
    Aalto University, School of Electrical Engineering, Department of Radio Science and Engineering.
    Lebreton, Jean-Pierre
    Laboratoire de Physique et Chimie de l’Environnement et de l’Espace (LPC2E).
    Eriksson, Anders
    Swedish Institute of Space Physics, Ångström Laboratory.
    Edberg, Niklas
    Swedish Institute of Space Physics, Ångström Laboratory.
    Goldstein, Raymond
    Belgian Institute for Space Aeronomy, Brussels.
    Henri, Pierre
    Laboratoire de Physique et Chimie de l’Environnement et de l’Espace (LPC2E).
    Coenders, Christoph
    Technische Universität–Braunschweig, Institute for Geophysics and Extraterrestrial Physics.
    Mokashi, Prachet
    Southwest Research Institute, 6220 Culebra Road, San Antonio.
    Nemeth, Zoltan
    Wigner Research Centre for Physics, 1121 Konkoly Thege Street 29-33, Budapest.
    Richter, Ingo
    Technische Universität–Braunschweig, Institute for Geophysics and Extraterrestrial Physics.
    Rubin, Martin
    Physikalisches Institut, University of Bern.
    Birth of a comet magnetosphere: A spring of water ions2015Ingår i: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 347, nr 6220, artikel-id aaa0571Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Rosetta mission shall accompany comet 67P/Churyumov-Gerasimenko from a heliocentric distance of >3.6 astronomical units through perihelion passage at 1.25 astronomical units, spanning low and maximum activity levels. Initially, the solar wind permeates the thin comet atmosphere formed from sublimation, until the size and plasma pressure of the ionized atmosphere define its boundaries: A magnetosphere is born. Using the Rosetta Plasma Consortium ion composition analyzer, we trace the evolution from the first detection of water ions to when the atmosphere begins repelling the solar wind (~3.3 astronomical units), and we report the spatial structure of this early interaction. The near-comet water population comprises accelerated ions (

  • 304.
    Nilsson, Hans
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Wieser, Gabriella Stenberg
    Swedish Institute of Space Physics.
    Behar, Etienne
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Wedlund, Cyril Simon
    Aalto University, School of Electrical Engineering, Department of Radio Science and Engineering.
    Kallio, Esa
    Finnish Meteorological Institute, Aalto University, School of Electrical Engineering, Department of Radio Science and Engineering.
    Gunell, Herbert
    Swedish Institute of Space Physics / Institutet för rymdfysik , Belgian Institute for Space Aeronomy, Brussels.
    Edberg, N.J.T.
    Swedish Institute of Space Physics, Uppsala.
    Eriksson, Anders
    Swedish Institute of Space Physics, Ångström Laboratory.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics.
    Koenders, Christoph
    Institut für Geophysik und Extraterrestrische Physik, Technische Universität Braunschweig.
    Wieser, Martin
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Lundin, Rickard
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Barabash, Stas
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Mandt, Kathleen E.
    Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Burch, James L.
    Southwest Research Institute, 6220 Culebra Road, San Antonio.
    Goldstein, Raymond M.
    Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Mokashi, Prachet
    Southwest Research Institute, 6220 Culebra Road, San Antonio.
    Carr, Chris
    Imperial College London.
    Cupido, Emanuele
    Imperial College London.
    Fox, P.T.
    Imperial College London.
    Szego, Karoly
    Wigner Research Centre for Physics, 1121 Konkoly Thege Street 29-33, Budapest.
    Nemeth, Zoltan
    Wigner Research Centre for Physics, 1121 Konkoly Thege Street 29-33, Budapest.
    Fedorov, Andrei
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Sauvaud, J.A.
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Koskinen, Hannu
    Department of Physics, University of Helsinki.
    Geiger, B.
    Rosetta Science Ground Segment, Science and Robotic Exploration (SRE-OOR).
    Evolution of the ion environment of comet 67P/Churyumov-Gerasimenko2015Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 583, artikel-id A20Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context. The Rosetta spacecraft is escorting comet 67P/Churyumov-Gerasimenko from a heliocentric distance of >3.6 AU, where the comet activity was low, until perihelion at 1.24 AU. Initially, the solar wind permeates the thin comet atmosphere formed from sublimation. Aims. Using the Rosetta Plasma Consortium Ion Composition Analyzer (RPC-ICA), we study the gradual evolution of the comet ion environment, from the first detectable traces of water ions to the stage where cometary water ions accelerated to about 1 keV energy are abundant. We compare ion fluxes of solar wind and cometary origin. Methods. RPC-ICA is an ion mass spectrometer measuring ions of solar wind and cometary origins in the 10 eV-40 keV energy range. Results. We show how the flux of accelerated water ions with energies above 120 eV increases between 3.6 and 2.0 AU. The 24 h average increases by 4 orders of magnitude, mainly because high-flux periods become more common. The water ion energy spectra also become broader with time. This may indicate a larger and more uniform source region. At 2.0 AU the accelerated water ion flux is frequently of the same order as the solar wind proton flux. Water ions of 120 eV-few keV energy may thus constitute a significant part of the ions sputtering the nucleus surface. The ion density and mass in the comet vicinity is dominated by ions of cometary origin. The solar wind is deflected and the energy spectra broadened compared to an undisturbed solar wind.

  • 305.
    Nilsson, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Flow Separation Control Utilizing Plasma Actuators2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The goal of this thesis was to both theoretically and experimentally show the effect of a plasma actuator for flow separation control.  In the theoretical part a solver was implemented in MATLAB code, to solve the governing equations describing the plasma actuator.  The experimental part included PIV (Particle Image Velocimetry) measurements of the velocity field induced by the plasma actuator, visualization of the effect in a wind tunnel and the development of a simple model of the plasma actuator based on the empirical result whose purpose is to be used in CFD (Computational Fluid Dynamics). The PIV measurements were performed with an acceptable result even though a lot of disturbance occurred in and near the plasma region.  The empirical result was used to develop the empirical plasma actuator model for CFD, which showed some interesting result.  The model implies that the induced force by the plasma actuator grows exponential with the applied peak-to-peak voltage.   The model was also used to predict airfoil performance with plasma actuators which showed an increase of the lift coefficient on a NACA0012 with a chord length of 0.1m.  Simulations were done for free-stream velocities up to 20m/s with three different configurations, without plasma actuator for comparison, with one actuator at the quarter-chord and one with three actuators on the airfoil.  With three actuators the increase of the lift coefficient was 108 percent at 5m/s and 14 percent at 20m/s. The simulations with one actuator were only performed up to 10m/s were the effect of the actuator still could be seen but for higher velocities the effect would probably be minor. The wind tunnel experiment clearly showed the effect and the advantages of utilizing plasma actuators for flow separation control.  The experiment showed that a single plasma actuator placed at the quarter chord of a fully stalled NACA0012 airfoil with a chord length of 0.1m, at approximately 20 degrees angle of attack and with a free-stream velocity of 1.5m/s, was able to reattach the flow behind the actuator. The result of the theoretical part was inconclusive, the code could not run with the appropriate voltage and frequency of the plasma actuator.  Some result was however obtained, implying that the time-average force induced by the plasma actuator was in the expected direction.  The theoretical model is however considered to have potential, the major problems concern the code which requires further development.

  • 306. Noelle, A
    et al.
    Hartmann, G.K
    Fahr, A
    Larry, D
    Lee, Y.P
    Locht, R
    Limao-Vieira, P
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Orlando, J.J
    Salama, F
    Vandaele, A.C
    Wayne, R.P
    Wu, C.Y.R
    UV/Vis+ Spectra Data base2015Dataset (Refereegranskat)
  • 307. Norberg, O.
    et al.
    Puccio, W.
    Olsen, J.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Andersson, L.
    Winningham, J.D.
    Jonsson, U.
    Luleå tekniska universitet.
    Eriksson, Magnus
    Munin: a student nanosatellite for space weather information1999Ingår i: Microsatellites as research tools: Proceedings of COSPAR Colloquium on Microsatellites as Research Tools held in Tainan, Taiwan, 14-17 December 1997 / edited by Fei-Bin Hsiao., Elsevier, 1999Konferensbidrag (Refereegranskat)
  • 308.
    Nordström, T.
    et al.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Stenberg, G.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zhang, T.L.
    Austrian Academy of Sciences, Space Research Institute, Graz.
    Venus ion outflow estimates at solar minimum: Influence of reference frames and disturbed solar wind conditions2013Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 118, nr 6, s. 3592-3601Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recent estimates of ion escape rates from Venus, based on ASPERA-4 data, differ by more than a factor of 4. Whereas the ASPERA-4 instrument provides state-of-the art observations, the limited field of view of the instrument and the strongly limited geographical coverage of the spacecraft orbit means that significant assumptions must be used in the interpretation of the data. We complement previous studies by using a method of average distribution functions to obtain as good statistics as possible while taking the limited field of view into account. We use more than 3 years of data, more than any of the previous studies, and investigate how the choice of a geographical reference frame or a solar wind electric field oriented reference frame affects the results. We find that the choice of reference frame cannot explain the difference between the previously published reports. Our results, based on a larger data set, fall in between the previous studies. Our conclusion is that the difference between previous studies is caused by the large variability of ion outflow at Venus. It matters significantly for the end result which data are selected and which time period is used. The average escape rates were found to be 5.2±1.0×1024 s−1for heavy ions (m/q ≥16) and 14±2.6×1024 s−1for protons. We also discuss the spatial distribution of the planetary ion outflow in the solar wind electric field reference frame.

  • 309.
    Nyström, Max
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    GNSS Interference Localization Through PDOA-Methods2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    As GPS signals are of low power, the receiving end is always highly susceptible to interference, both unintentional and deliberate. As such there is a need to develop practical ways of detecting and localizing interference sources. This paper evaluates different methods of localization, and also demonstrates a novel method of both practical and cheap localization.

  • 310.
    Pellinen-Wannberg, Asta
    et al.
    Umeå universitet, Swedish Institute of Space Physics.
    Murad, Edmond
    AFRL.
    Broasch, Noah
    The Wise Observatory and Tel Aviv University.
    Häggström, Ingemar
    EISCAT Scientific Association, Kiruna.
    Khayrov, Timur
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Julius Maximilians Universität Würzburg.
    The solar cycle effect on the atmosphere as a scintillator for meteor observations2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    We discuss using high solar cycle atmospheric conditions as sensors for observing meteors and their properties. High altitude meteor trails (HAMTs) have sometimes been observed with HPLA (High Power Large Aperture) radars. At other times they are not seen. In the absence of systematic studies on this topic, we surmise that the reason might be differing atmospheric conditions during the observations. At EISCAT HAMTs were observed in 1990 and 1991. Very high meteor trails were observed with Israeli L-band radars in 1998, 1999 and 2001.Through the Leonid activity, around the latest perihelion passage of comet Tempel-Tuttle, optical meteors as high as 200 km were reported. This was partly due to new and better observing methods. However, all the reported periods of high altitude meteors seem to correlate with solar cycle maximum. The enhanced atmospheric and ionospheric densities extend the meteoroid interaction range with the atmosphere along its path, offering a better possibility to distinguish differential ablation of the various meteoric constituents. This should be studied during the next solar maximum, due within a few years.

  • 311.
    Perez, Javier Roldán
    et al.
    Department of Physics, Systems Engineering and Signal Theory, University of Alicante.
    Pomares, J.
    Department of Physics, Systems Engineering and Signal Theory, University of Alicante.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Image-based control of satellite-mounted robot manipulators2016Ingår i: Proceedings of 2016 7th International Conference on Mechanical and Aerospace Engineering, ICMAE 2016: London, United Kingdom, 18-20 July 2016, Piscataway, NU: IEEE Communications Society, 2016, s. 346-351, artikel-id 7549564Konferensbidrag (Refereegranskat)
    Abstract [en]

    Robot manipulators have multiple uses and are especially useful when dealing with complex manipulation tasks in unstructured environments. This paper presents a direct image-based controller for performing the guidance of a free-floating robot manipulator. A camera is attached to the end-effector of the manipulator and the robot is attached to a base satellite. The proposed direct image-based control strategy computes the torque to be applied to the joints, and takes into account the system's kinematics and dynamics model. The operation is such that the base is completely free and floating in space with no attitude control, and thus freely reacting to the movements of the robot manipulator attached to it. The main objective is to track a desired trajectory in the image space with respect to an observed object in space. The proposed control strategy optimizes the motor commands with respect to a specified metric. The controller is applied to direct visual control of a four-degree-of-freedom robot manipulator.

  • 312.
    Pietranera, Luca
    et al.
    University of Manchester, School of Physics and Astronomy.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Calisse, Paolo
    University of Cardiff, School of Physics and Astronomy.
    Emde, Claudia
    Deutsches Zentrum fuer Luft- und Raumfahrt (DLR) Institut fuer Physik der Atmosphaere, Oberpfaffenhofen.
    Hayton, Darren
    University of Cardiff, School of Physics and Astronomy.
    John, Viju Oommen
    University of Miami, Rosenstiel School of Marine and Atmospheric Sciences, Miami.
    Maffei, Bruno
    University of Manchester, School of Physics and Astronomy.
    Piccirillo, Lucio
    University of Manchester, School of Physics and Astronomy.
    Pisano, Giampaolo
    University of Manchester, School of Physics and Astronomy.
    Savini, Giorgio
    University of Cardiff, School of Physics and Astronomy.
    Sreerekha, T. R.
    Met Office Hadley Centre, Exeter.
    Observing cosmic microwave background polarisation through ice2007Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 376, nr 2, s. 645-650Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ice crystal clouds in the upper troposphere can generate polarization signals at the μK level. This signal can seriously affect very sensitive ground-based searches for E and B modes of cosmic microwave background polarization. In this paper, we estimate this effect within the ...

  • 313.
    Pomares, Jorge
    et al.
    University of Alicante.
    Felicetti, Leonard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Pérez, Javier
    University of Alicante.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Space Mechatronics group, University of Toronto, Institute for Aerospace Studies.
    Concurrent Image-based Visual Servoing with Adaptive Zooming for Non-cooperative Rendezvous Maneuvers2018Ingår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 61, nr 3, s. 862-878Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An image-based servo controller for the guidance of a spacecraft during non-cooperative rendezvous is presented in this paper. The controller directly utilizes the visual features from image frames of a target spacecraft for computing both attitude and orbital maneuvers concurrently. The utilization of adaptive optics, such as zooming cameras, is also addressed through developing an invariant-image servo controller. The controller allows for performing rendezvous maneuvers independently from the adjustments of the camera focal length, improving the performance and versatility of maneuvers. The stability of the proposed control scheme is proven analytically in the invariant space, and its viability is explored through numerical simulations.

  • 314.
    Pontoni, Angèle
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Evolution of the signal induced by ChemCam on Mars as a function of focus2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    ChemCam, mounted on the mast of the Mars Science Laboratory (MSL) rover, uses Laser-Induced Breakdown Spectroscopy (LIBS) to perform remote-sensing science on Mars. ChemCam’s telescope is used to simultaneously focus the laser on martian rocks up to 7 meters away from the rover and collect the light emitted as the plasma plume created on the target cools down. The light is then transmitted to three spectrometers located in the body of the rover, providing spectra from which the composition of the samples is inferred on the ground. Context images of the sampled targets are captured by the Remote Micro Imager (RMI) that completes the instrument.

    A hardware failure that occurred a bit more than two years into the mission caused the ChemCam instrument to lose its original autofocus ability. This resulted in a degraded performance mode for several months while the ChemCam team developed a new autofocus algorithm based on the RMI images. During this period of degraded performance, several observations with different focus conditions were made on each target.  This unusual set of data provides the opportunity to study the influence of less-than-optimal focus conditions on the LIBS signal created on the target and analyzed by ChemCam.

    To this purpose, we look at both raw ChemCam spectra and  post-processed products used for scientific analysis to investigate how the quality of the focus influences the LIBS signal and the quantitative predictions of the composition of the observed targets.

  • 315.
    Pope, Charles
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Calibration and Uncertainty Analysis of a Spacecraft Attitude Determination Test Stand2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Experimental testing of attitude determination systems still plays an important role, despite increasing use of simulations. Testing provides a means to numerically quantify system performance, give confidence in the models and methods, and also discover and compensate for unexpected behaviours and interactions with the attitude determination system. The usefulness of the test results is dependent on an understanding of the uncertainties that contribute to the attitude error. With this understanding, the significance of the results can be assessed, and efforts to reduce attitude errors can be directed appropriately. The work of this thesis is to gain a quantitative understanding of the uncertainties that impact the attitude error of low cost spinning spacecraft using COTS camera (as Sun sensor) and MEMS magnetometer. The sensors were calibrated and the uncertainties in these calibrations were quantified, then propagated through the Triad method to uncertainties in the attitude. It was found that most systematic errors were reduced to negligible levels, except those due to timing latencies. Attitude errors achieved in the laboratory with the experimental setup were around 0.14 degrees (3σ) using either the Triad, q-method or Extended Kalman Filter with a gyro for dynamic model replacement. The errors in laboratory were dominated by magnetometer noise. Furthermore, correlated systematic errors had the effect of reducing the attitude error calculated in the laboratory. For an equivalent Sun-mag geometry in orbit, simulation showed that total attitude error would be of the order of 0.77 degrees (3σ). An uncertainty contribution analysis revealed this error was dominated by uncertainties in the inertial magnetic field model. Uncertainties in knowledge of the inertial Sun model, sensor calibration, sensor alignment and sensor noise were shown to be insignificant in comparison.

  • 316.
    Poppe, A.R.
    et al.
    Space Science Laboratory, University of California, Berkeley.
    Fatemi, Shahab
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Halekas, J.S.
    Space Science Laboratory, University of California, Berkeley.
    Holmström, Mats
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Delory, G.T.
    Space Science Laboratory, University of California, Berkeley.
    ARTEMIS observations of extreme diamagnetic fields in the lunar wake2014Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 41, nr 11, s. 3766-3773Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present two Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun ( ARTEMIS) observations of diamagnetic fields in the lunar wake at strengths exceeding twice the ambient magnetic field during high plasma beta conditions. The first observation was 350 km from the lunar surface while the Moon was located in the terrestrial magnetosheath with elevated particle temperatures. The second observation was in the solar wind ranging from 500 to 2000 km downstream, with a relatively low magnetic field strength of approximately 1.6 nT. In both cases, the plasma beta exceeded 10. We discuss the observations and compare the data to hybrid plasma simulations in order to validate the model under such extreme conditions and to elucidate the global structure of the lunar wake during these observations. The extreme nature of the diamagnetic field in the lunar wake provides an important end-member test case for theoretical and modeling studies of the various plasma processes operating in the lunar wake.

  • 317.
    Potrivitu, George-Cristian
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. University Toulouse III Paul Sabatier France.
    Low–voltage External Discharge Plasma Thruster and Hollow Cathodes Plasma Plume Diagnostics Utilising Electrostatic Probes and Retarding Potential Analyser2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The present thesis is the result of a research period at the Institute of Space and Astronautical Science of the Japanese Aerospace Exploration Agency, ISAS/JAXA within Funaki Laboratory of the Department of Space Flight Systems that followed the path of plume plasma diagnostics for space electric propulsion drives. During the experimental studies two high-current hollow cathodes and an innovative prototype of a low-voltage fully external discharge plasma thruster (XPT) had their plasma plumes diagnosed using electrostatic probes and retarding potential analyser (RPA).

    A Hall thruster and hollow cathode plume is defined as an unmagnetised quasi-neutral plasma which is mainly formed of neutral particles, electrons, singly and doubly charged ions. Plasma diagnostic techniques provide information through practical observations in order to fully understand the dynamics of the aforementioned plume components, the physical processes taking place within the plume and their effects on the spacecraft, for instance. Mastering these aspects of the plasma plume of space electric propulsion drives bolster the design processes, leading to highly efficient devices.

    Firstly, the introduction provides insights on the fundamental principles of hollow cathodes and Hall thrusters and a brief presentation of the plasma diagnostic techniques used during the research: single and double Langmuir probes, emissive probes and retarding potential analyser. Then, the fundamental plume diagnostics principles are depicted in an exhaustive way, departing from classical plasma kinetic theory, energy distribution functions and ending with an overview on the theory of charge collection by cylindrical probes. Subsequently, peculiarities of various analysis techniques are exposed for the Langmuir probes, emissive probes and RPA, with an emphasis on their strengths and demerits.

    The experimental setups for the cathodes and XPT plume diagnostic procedures are then outlined. The experimental logic, setup and electrical diagrams as well as a presentation of each probe design and manufacturing details are extensively discussed.

    The hollow cathodes experimental results are exposed with a discourse that aims of overviewing the difference between the various data analysis methods applied for the raw data. A discussion ensued based on the results in order to effectively identify mechanisms that produced the observed plasma parameters distributions.

    For the first time, the plume of a fully external discharge plasma thruster was diagnosed utilising double Langmuir probes.  The thesis highlights the main results obtained for the XPT far-field plume plasma diagnostics. The experimental findings for both thruster centreline positions and 2D plume maps for several axial distances away from the anode plate offer a ground basis for future measurements, a comparison term and a database to support ongoing computational codes. The results are discussed and related to the thruster performances data obtained during previous experiments.

    The thesis includes consistency analyses between the experimental data and the numerical simulation results and the uncertainties in measured plasma parameters associated with each data analysis procedure are evaluated for each data set. Last, the conclusions underline the main aspects of the research and further work on the previously mentioned plasma diagnostic techniques for hollow cathodes and XPT is suggested. 

  • 318.
    Rapp, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Julius-Maximilians University of Würzburg, Department of Mathematics and Computer Science, Chair of Aerospace Information Technology, Professorship of Space Technology.
    Development and Implementation of a Mission Planning Tool for SONATE2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In the scope of the master's project which is documented with the present thesis a mission planning tool (MPT) for SONATE was developed and implemented. After a thorough research on the current state of the art of MPTs and taking especially the early stage of the SONATE mission into account, it was decided to develop a generic timeline-based MPT. In contrast to existing MPTs a system is envisioned which is both powerful, regarding advanced features like resource control, and applicable for small satellite missions regarding the overall complexity and the associated configuration and training effort. Although it was obvious from an early stage that this vision cannot be reached in the scope of this project, it was kept during the project definition, object oriented analysis and early design stages in order to allow future extensions. Also the decision to develop the MPT on top of the Eclipse Rich Client Platform is mainly due to the argument of future extensibility.

    The MPT, which is released with this thesis, hence is a very basic generic timeline-based MPT omitting all possible advanced features like resource control or procedure validation, but featuring all essential parts of a MPT, i.e. modelling of procedures, scheduling of activities, and the generation of telecommand sequences. Furthermore, the user is supported by an intuitive graphical user interface. The thesis documents the development process, thus giving a broad understanding of the design and the implementation. For specific details of the implementation one may also refer to the separate technical documentation, while a user handbook included as appendix.

    The characteristics of the SONATE mission as a technology demonstrator for highly autonomous systems raise several important questions regarding the overall mission planning process. Therefore, besides the actual development of the MPT, those questions are discussed in a theoretical manner in the scope of this thesis, taking also account of the general emergence of highly autonomous satellites systems.Three concepts, Safe Planning, Sigma Resource Propagation, and Direct Telemetry Feedback, are proposed to face the challenges rising from the foreseen alternation of phases of classical mission operations and phases of autonomous operations of the satellite.

    Concluding the thesis, the final software product's features and capabilities are verified against the previously defined requirements and thus the overall success of the project is determined to be a 100% success fulfilling all primary project objectives. Finally, several fields for further research on the topic in general and work on the MPT itself are identified and outlined to pave the way for follow-up projects.

  • 319.
    Rijal, Samundra
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Case Study: Conceptual Ground Station Design for N66 Connect AB2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    As the communication deficit in the Arctic region is enormous especially above 75 [Deg] N latitude, the concern and opportunity of providing reliable & efficient connectivity in the Arctic region has beenduly noted & understood by N66 Connect AB (N66). This case study documents a comprehensive research which implements system engineering approach for establishment of a Ground Station (GS) at Svalbard, Norway with sole focus of connecting the inaccessible geographical region lying in the Arctic with rest of the world. Several GS system & subsystem are studied and comparative analysis is made on how the communication can be established with the N66 Connect AB (N66)’s potential clients and its satellites that are to be deployed in September, 2018.The case study resulted in analysis of several risks involved during development & operation of the GS,the hardware, software & operational architecture, the features of GS’s system capable of meeting N66’s objectives and the market potential of the service after GS operations.

  • 320.
    Romero, Faviola
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    In-orbit performance analysis of the image sensors from Pleiades mission2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The image sensors embedded in the instruments on board of different satellites are a key aspect in the success of a mission of any type such as Earth observation, astronomy or planetary and universe exploration. The quality of the sensor itself as well as the electronics embedded in the instrument suffer from aging, not only due to the usage, but also due to the space environment factors. The outer space harsh environment is composed of charged particles with an incredibly high energy that can get through the shielding of the spacecraft thus causing damage to the sensors, or any part of the spacecraft. After a satellite is placed in orbit, there is no other way to check on its condition than to analyse the data transmitted to the ground stations.

     

    It is well known that we can measure the evolution of the instrument’s detection unit by measuring the variation of the quality of the images taken in orbit. As it has been done in past work, the atypical behaviour can be detected at a pixel level by analysing the images taken in orbit, preferably in complete darkness to discard any parasitic light. Past analysis of the dark images from the sensors on board the Picard, SPOT4 and Sentinel2A mission, proposed a classification of the different atypical behaviour that a pixel can show, such as hot, transitory-hot or RTS. By the end of the mission this defects may even be present in several pixels.

     

    The purpose of this work is to process the dark images obtained on orbit, at the end of the mission PLEIADES, to better understand the behaviour both Panchromatic and Multispectral CCD sensors and the differences in performance with respect to the tests made previously on ground. For this, a description of the framework of the PLEIADES mission and the technical design aspects of the CCD sensors on board are presented. Subsequently, the different image processing techniques used and developed are described, along with the tests made to get to the positive conclusion of no major anomalies detected in the PLEIADES images sensors. The analysis is done by means of new set of functions adjusted to the structure of the data, as well as the same detection software used in the previous analysis. Finally, a discussion is presented along with a further perspective for the analysis of future sets of data. 

  • 321.
    Rydberg, Bengt
    et al.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Prediction of cloud ice signatures in submillimeter emission spectra by means of ground-based radar and in-situ microphysical data2007Ingår i: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 133, nr Suppl.2, s. 151-162Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Submillimetre down-looking radiometry is a promising technique for global measurements of cloud ice properties. There exist no observation data of sufficient size that can be used for detailed pre-launch studies of such an instrument and other means must be found to obtain data to optimise the instrument design and similar tasks. Several aspects of the observations make traditional retrieval methods not suitable and nonlinear multidimensional regression techniques (e.g. Bayesian Monte Carlo integration and neural networks) must be applied. Such methods are based on a retrieval database and to be successful the database must mimic relevant real conditions closely. A method to generate such databases of high quality is described here. Correct vertical distributions of cloud ice are obtained by basic data from ground-based radars. Cloud ice particle microphysical properties are generated randomly where statistical parameters are selected to mimic in situ measurement data closely. Atmospheric background fields from ECMWF are perturbed to account for variation on sub-grid scales. All these data, together with sensor characteristics, are fed into a state-of-the-art radiative transfer simulator (ARTS). The method was validated by a successful comparison with AMSU data.

  • 322.
    Rydberg, Bengt
    et al.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Murtagh, Donal
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Non-Gaussian Bayesian retrieval of tropical upper tropospheric cloud ice and water vapour from Odin-SMR measurements2009Ingår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 2, nr 2, s. 621-637Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Improved Odin-SMR retrievals of upper tropospheric water are presented. The new retrieval algorithm retrieves humidity and cloud ice mass simultaneously and takes into account of cloud inhomogeneities. Both these aspects are introduced for microwave limb sounding inversions for the first time. A Bayesian methodology is applied allowing for a formally correct treatment of non-unique retrieval problems involving non-Gaussian statistics. Cloud structure information from CloudSat is incorporated into the retrieval algorithm. This removes a major limitation of earlier inversion methods where uniform cloud layers were assumed and caused a systematic retrieval error. The core part ofthe retrieval technique is the generation of a database that must closely represent real conditions. Good agreement with Odin-SMR observations indicates that this requirement is met. The retrieval precision is determined to be about 5–17% RHi and 65% for humidity and cloud ice mass, respectively.For both quantities, the vertical resolution is about 5 km and the best retrieval performance is found between 11 and 15 km. New data show a significantly improved agreement with CloudSat cloud ice mass retrievals, at the same time consistency with the Aura MLS humidity results is maintained. The basics of the approach presented can be applied for all passive cloud observations and should be of broad interest. The results can also be taken as a demonstration of the potential of down-looking sub-mm radiometry for global measurements of cloud ice properties.

  • 323.
    Rüfenacht, R.
    et al.
    Institute of Applied Physics, University of Bern.
    Murk, A.
    Institute of Applied Physics, University of Bern.
    Kämpfer, N.
    Institute of Applied Physics, University of Bern.
    Eriksson, P.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Buehler, S. A.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Division of Space Technology, SRT, Luleä University of Technology.
    Middle-atmospheric zonal and meridional wind profiles from polar, tropical and midlatitudes with the ground-based microwave Doppler wind radiometer WIRA2014Ingår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 7, s. 4491-4505Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    WIRA is a ground-based microwave Doppler spectroradiometer specifically designed for the measurement of profiles of horizontal wind in the upper stratosphere and lower mesosphere region where no other continuously running measurement technique exists. A proof of principle has been delivered in a previous publication. A technical upgrade including a new high-frequency amplifier and sideband filter has improved the signal to noise ratio by a factor of 2.4. Since this upgrade the full horizontal wind field comprising zonal and meridional wind profiles is continuously measured. A completely new retrieval based on optimal estimation has been set up. Its characteristics are detailed in the present paper. Since the start of the routine operation of the first prototype in September 2010, WIRA has been measuring at four different locations at polar, mid- and tropical latitudes (67°22′ N/26°38′ E, 46°57′ N/7°26′ E, 43°56′ N/5°43′ E and 21°04′ S/55°23′ E) for time periods between 5.5 and 11 months. The data presented in this paper are daily average wind profiles with typical uncertainties and resolutions of 10 to 20 m s−1 and 10 to 16 km, respectively. A comparison between the data series from WIRA and European Centre for Medium-Range Weather Forecasts (ECMWF) model data revealed agreement within 10% in the stratospheric zonal wind. The meridional wind profiles agree within their error bars over the entire sensitive altitude range of WIRA. However, significant differences in the mesospheric zonal wind speed of up to 50% have been found.

  • 324.
    Rüfenacht, R.
    et al.
    Institute of Applied Physics, University of Bern.
    Murk, A.
    Institute of Applied Physics, University of Bern.
    Kämpfer, N.
    Institute of Applied Physics, University of Bern.
    Eriksson, P.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Middle-atmospheric zonal and meridional wind profiles from polar, tropical and midlatitudes with the ground-based microwave Doppler wind radiometer WIRA2014Ingår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 7, s. 7717-7752Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    WIRA is a ground-based microwave Doppler spectro radiometer specifically designed for the measurement of profiles of horizontal wind in the upper stratosphere and lower mesosphere region where no other continuously running measurement technique exists. A proof of principle has been delivered in a previous publication. Since a technical upgrade which improved the signal to noise ratio by a factor of 2.4 the full horizontal wind field comprising zonal and meridional wind profiles is continuously measured. A completely new retrieval based on optimal estimation has been set up. Its characteristics are detailed in the present paper.Since the start of the routine operation of the first prototype in September 2010, WIRA has been measuring at four different locations at polar, mid and tropical latitudes for time periods between 5.5 and 11 months. A comparison between the data series from WIRA and ECMWF model data revealed agreement within 10% in the stratospheric zonal wind. The meridional wind profiles agree within their error bars over the entire sensitive altitude range of WIRA. However, significant differences in the mesospheric zonal wind speed of up to 40% have been found.

  • 325.
    Sadeghi, Soheil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Institute for Aerospace Studies, University of Toronto.
    Electric potential structures of auroral acceleration region border from multi-spacecraft Cluster data2018Ingår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 61, nr 8, s. 2050-2056Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper studies an auroral event using data from three spacecraft of the Cluster mission, one inside and two at the poleward edge of the bottom of the Auroral Acceleration Region (AAR). The study reveals the three-dimensional profile of the region’s poleward boundary, showing spatial segmentation of the electric potential structures and their decay in time. It also depicts localized magnetic field variations and field-aligned currents that appear to have remained stable for at least 80 s. Such observations became possible due to the fortuitous motion of the three spacecraft nearly parallel to each other and tangential to the AAR edge, so that the differences and variations can be seen when the spacecraft enter and exit the segmentations, hence revealing their position with respect to the AAR.

  • 326.
    Sadeghi, Soheil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Multi-spacecraft Studies of the Auroral Acceleration Region: From Cluster to Nanosatellites2017Ingår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 59, nr 5, s. 1173-1188Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper discusses the utilization of multiple Cubesats in various formations for studies in the auroral acceleration region. The focus is on the quasi-static properties, spatio-temporal features, electric potential structures, field-aligned currents, and their relationships, all of which are fundamentally important for an understanding of the magnetosphere-ionosphere coupling. It is argued that a multitude of nanosatellites can address some of the relevant outstanding questions in a broader range of spatial, temporal, and geometrical features, with higher redundancy and data consistency, potentially resulting in a shorter mission period and a higher chance of mission success. A number of mission concepts consisting of a cluster of 6 to 12 Cubesats with their specific onboard payloads are suggested for such missions over a period of as short as two months.

  • 327.
    Sam, Lydia
    et al.
    Department of Environmental Science, Sharda University.
    Bhardwaj, Anshuman
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Sinha, Vinay S.P.
    Department of Natural Resources, TERI University.
    Joshi, Pawan Kumar Umar
    Department of Natural Resources, TERI University.
    Kumar, Rajesh C.
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Use of Geospatial Tools to Prioritize Zones of Hydro-Energy Potential in Glaciated Himalayan Terrain2016Ingår i: Journal of the Indian Society of Remote Sensing, ISSN 0255-660X, Vol. 44, nr 3, s. 409-420Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sustainable development of the Himalayan region is directly linked to optimal utilization of available renewable resources. There is a need to first select the zones suitable for hydropower sites, and then to focus on them only; as purely field-based surveying of rugged mountainous regions for hydropower generation requires too much of time and effort. We used geospatial tools to identify suitable sites for hydropower generation. A Geographic Information System (GIS)-based tool called Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) was used for computing annual runoff volume using watershed-wise topography and biophysical variables. The zones suitable for hydropower generation were then identified based on calculated hydropower energy using derived runoff volumes and hydraulic head. The model accuracy was checked using well established efficiency criteria: coefficient of determination (R2 = 0.98), RMSE-observations standard deviation ratio (RSR), Percent bias (PBIAS) and Nash–Sutcliffe efficiency (NSE). For all these parameters, the model was found to be performing satisfactorily.

  • 328.
    Sato, T.O.
    et al.
    Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama.
    Sagawa, H.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Kreyling, D.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Manabe, T.
    Osaka Prefecture University, Naka, Sakai.
    Ochiai, S.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Kikuchi, K.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Baron, P.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Mendrok, Jana
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Urban, J.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Murtagh, D.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Yasui, M.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Kasai, Y.
    Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama.
    Strato-mesospheric ClO observations by SMILES: error analysis and diurnal variation2012Ingår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 5, nr 11, s. 2809-2825Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Chlorine monoxide (ClO) is the key species for anthropogenic ozone losses in the middle atmosphere. We observed ClO diurnal variations using the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on the International Space Station, which has a non-sun-synchronous orbit. This includes the first global observations of the ClO diurnal variation from the stratosphere up to the mesosphere. The observation of mesospheric ClO was possible due to 10–20 times better signal-to-noise (S/N) ratio of the spectra than those of past or ongoing microwave/submillimeter-wave limb-emission sounders. We performed a quantitative error analysis for the strato- and mesospheric ClO from the Level-2 research (L2r) product version 2.1.5 taking into account all possible contributions of errors, i.e. errors due to spectrum noise, smoothing, and uncertainties in radiative transfer model and instrument functions. The SMILES L2r v2.1.5 ClO data are useful over the range from 0.01 and 100 hPa with a total error estimate of 10–30 pptv (about 10%) with averaging 100 profiles. The SMILES ClO vertical resolution is 3–5 km and 5–8 km for the stratosphere and mesosphere, respectively. The SMILES observations reproduced the diurnal variation of stratospheric ClO, with peak values at midday, observed previously by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite (UARS/MLS). Mesospheric ClO demonstrated an opposite diurnal behavior, with nighttime values being larger than daytime values. A ClO enhancement of about 100 pptv was observed at 0.02 to 0.01 hPa (about 70–80 km) for 50° N–65° N from January–February 2010. The performance of SMILES ClO observations opens up new opportunities to investigate ClO up to the mesopause.

  • 329.
    Schafer, Ewan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Stereoscopic Light Curve Analysis of Space Debris Objects2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 330.
    Schilling, Klaus
    et al.
    Julius-Maximilians Universität Würzburg, Informatik VII: Robotics & Telematics.
    Barabash, Victoria
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    SpaceMaster: An International, Interdisciplinary Master in Space Science and Technology2017Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The significant demand for aerospace engineers led 2005 to the foundation of the interdisciplinary program "SpaceMaster" by six European Universities. It was established in the European elite-program "Erasmus Mundus" to train talented young people in the challenging subject of space science and technology. The universities cooperate and contribute their special expertise to the courses in order to cover the broad interdisciplinary area of spacecraft design and space environment. In particular system design techniques are emphasized, which are of interest for a broad spectrum of industrial applications well beyond aerospace.

    The international dimension of this space education is reflected in the distribution of places for education: 1

    st semester in Würzburg (Germany), 2nd semester in Kiruna (Sweden), second year according to the desired specialization in one of the six partner European Universities. The successful students will receive double diploma from the two European Universities, where most credits were received. The student population is also very international: typically from about 600 applications 50 students are selected, half of them from Europe, the other half from outside Europe.

    The students are able to follow the more scientific tracks on space physics with an emphasis on instrumentation and astronomy, or atmospheric and planetary physics. The engineering tracks emphasize the design of spacecraft and mission realization. Here specifically the design of CanSats and educational CubeSats is used to complement the lectures by practical implementation aspects. For more than 10 years, the SpaceMaster-alumni encounter excellent career perspectives in industry, space agencies and research institutes.

    In this contribution the international university cooperation, the contents of the curriculum, as well as the specific challenges and acquired experiences in this international program are addressed.

  • 331.
    Schillings, Audrey
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Swedish Institute of Space Physics, Kiruna, Sweden.
    O+ outflow during geomagnetic storms observed by Cluster satellites2018Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Den del av rymden som domineras av solens magnetfält kallas heliosfären. Helios-fären omfattar hela solsystemet inklusive jorden, vilket gör att det finns en starkkoppling mellan solen och jorden. Solen sänder oavbrutet ut laddade partiklar in denså kallade solvinden och när dessa energika partiklar träffar jorden påverkas mag-netosfären (det område kring jorden där det geomagnetiska fältet dominerar). Närsolvinden är starkare än vanligt uppstår störningar. I magnetosfären som ger effektersom kan uppmätas med markbaserade instrument.

    Den övre atmosfären utsätts för strålning från solen som joniserar atomer ochmolekyler, och formar det område som kallas jonosfären. Några av de tyngre jonpop-ulationerna i jonosfären, som till exempel syrejoner, kan hettas upp och accelererasgenom flera olika möjliga processer. Detta gör att de flödar uppåt i atmosfären. Ipolarområdena är dessa mekanismer särskilt effektiva och om tillräckligt med energitillförs jonerna kan gravitationen övervinnas, vilket gör att jonerna flödar upp längsöppna magnetfältlinjer och kan gå förlorade ut i den interplanetära rymden. Generelltsett har jonutflöde redan studerats väl, men jonutflöde under extrema magnetosfäriskaförhållanden har inte undersökts i detalj.

    Störda magnetosfäriska förhållanden korrelerar med då solen är aktiv, som tillexempel koronahål eller under utvecklingen av aktiva solområden. Från dessa områ-den härstammar koronamassautkastningar. När dessa extrema händelser når jordenkomprimeras magnetosfären och det geomagnetiska och interplanetära magnetiskafältet omkopplas, vilket ofta leder till geomagnetiska stormar. Under dessa införsstora mängder av partiklar i solvinden och energi till magnetosfären, och ett högresyrejonsutflöde är också observerat.

    Data från Clustersatelliterna har använts; dessa utgörs av fyra satelliter i for-mation i omloppsbana kring jorden. Plasmaområdena där de befinner sig är därjonutflödet vanligtvis observeras. Denna avhandling behandlar syrejonsutflöde understörda magnetosfäriska förhållanden och flera extrema geomagnetiska stormar. Detvisas att syrejonsutflödet som förloras till solvinden ökar exponentiellt med geomag-netiskt aktivitet (Kp-index) och ökar med upp till 2 storleksordningar under extremageomagnetiska stormar.

  • 332.
    Schillings, Audrey
    et al.
    Instiutet for rymdfysik, Kiruna, Sweden.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Instiutet for rymdfysik, Kiruna, Sweden.
    Slapak, Rikard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Yamauchi, M
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Westerberg, Lars Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Relative outflow enhancements during major geomagnetic storms: Cluster observations2017Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 5, nr 6, s. 1341-1352Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The rate of ion outflow from the polar ionosphere is known to vary by orders of magnitude, depending on the geomagnetic activity. However, the upper limit of the outflow rate during the largest geomagnetic storms is not well constrained due to poor spatial coverage during storm events. In this paper, we analyse six major geomagnetic storms between 2001 and 2004 using Cluster data. The six major storms fulfil the criteria of Dst 100 nT or Kp 7C. Since the shape of the magnetospheric regions (plasma mantle, lobe and inner magnetosphere) are distorted during large magnetic storms, we use both plasma beta and ion characteristics to define a spatial box where the upward OC flux scaled to an ionospheric reference altitude for the extreme event is observed. The relative enhancement of the scaled outflow in the spatial boxes as compared to the data from the full year when the storm occurred is estimated. Only OC data were used because HC may have a solar wind origin. The storm time data for most cases showed up as a clearly distinguishable separate peak in the distribution toward the largest fluxes observed. The relative enhancement in the outflow region during storm time is 1 to 2 orders of magnitude higher compared to less disturbed time. The largest relative scaled outflow enhancement is 83 (7 November 2004) and the highest scaled OC outflow observed is 2 1014 m2 s1 (29 October 2003).

  • 333.
    Schillings, Audrey
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Slapak, Rikard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics, Kiruna.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Atmospheric loss during major geomagnetic storms: Cluster observations2017Konferensbidrag (Refereegranskat)
  • 334.
    Schreier, Franz
    et al.
    DLR — German Aerospace Center, Remote Sensing Technology Institute, Oberpfaffenhofen.
    García, Sebastián Gimeno
    DLR — German Aerospace Center, Remote Sensing Technology Institute, Oberpfaffenhofen.
    Hedelt, Pascal
    DLR — German Aerospace Center, Remote Sensing Technology Institute, Oberpfaffenhofen.
    Hess, Michael
    DLR — German Aerospace Center, Remote Sensing Technology Institute, Oberpfaffenhofen.
    Mendrok, Jana
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Vasquez, Mayte
    DLR — German Aerospace Center, Remote Sensing Technology Institute, Oberpfaffenhofen.
    Xu, Jian
    DLR — German Aerospace Center, Remote Sensing Technology Institute, Oberpfaffenhofen.
    GARLIC - a general purpose atmospheric radiative transfer line-by-line infrared-microwave code: Implementation and evaluation2014Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 137, s. 29-50Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A suite of programs for high resolution infrared-microwave atmospheric radiative transfer modeling has been developed with emphasis on efficient and reliable numerical algorithms and a modular approach appropriate for simulation and/or retrieval in a variety of applications. The Generic Atmospheric Radiation Line-by-line Infrared Code — GARLIC — is suitable for arbitrary observation geometry, instrumental field–of–view, and line shape. The core of GARLIC's subroutines constitutes the basis of forward models used to implement inversion codes to retrieve atmospheric state parameters from limb and nadir sounding instruments.This paper briefly introduces the physical and mathematical basics of GARLIC and its descendants and continues with an in-depth presentation of various implementation aspects: An optimized Voigt function algorithm combined with a two-grid approach is used to accelerate the line-by-line modeling of molecular cross sections; various quadrature methods are implemented to evaluate the Schwarzschild and Beer integrals; and Jacobians, i.e. derivatives with respect to the unknowns of the atmospheric inverse problem, are implemented by means of automatic differentiation. For an assessment of GARLIC's performance, a comparison of the quadrature methods for solution of the path integral is provided. Verification and validation are demonstrated using intercomparisons with other line-by-line codes and comparisons of synthetic spectra with spectra observed on Earth and from Venus.

  • 335.
    Schreier, Franz
    et al.
    DLR, Remote Sensing Technology Institute, 82234 Oberpfaffenhofen.
    Garcia, S. Gimeno
    DLR, Remote Sensing Technology Institute, 82234 Oberpfaffenhofen.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Kottayil, Ajil
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Höpfner, Michael
    Karlsruhe Institute of Technology.
    Clarmann, Thomas von
    Karlsruhe Institute of Technology.
    Stiller, Gabriele P.
    Karlsruhe Institute of Technology.
    Intercomparison of three microwave/infrared high resolution line-by-line radiative transfer codes2013Ingår i: International Radiation Symposium: Radiation Processes in the Atmosphere and Ocean, IRS 2012, Berlin, Germany; 6 August 2012-10 August 2012, 2013, s. 119-122Konferensbidrag (Refereegranskat)
    Abstract [en]

    An intercomparison of three line-by-line (lbl) codes developed independently for atmospheric sounding - ARTS, GARLIC, and KOPRA - has been performed for a thermal infrared nadir sounding application assuming a HIRS-like (High resolution Infrared Radiation Sounder) setup. Radiances for the HIRS infrared channels and a set of 42 atmospheric profiles from the "Garand dataset" have been computed. Results of this intercomparison and a discussion of reasons of the observed differences are presented

  • 336.
    Schreier, Franz
    et al.
    DLR, Remote Sensing Technology Institute, 82234 Oberpfaffenhofen.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan A.
    Universität Hamburg, Meteorological Institute.
    Clarmann, Thomas von
    KIT — Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research.
    Intercomparison of three microwave/infrared high resolution line-by-line radiative transfer codes2018Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 211, s. 64-77Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An intercomparison of three line-by-line (lbl) codes developed independently for atmospheric radiative transfer and remote sensing – ARTS, GARLIC, and KOPRA – has been performed for a thermal infrared nadir sounding application assuming a HIRS-like (High resolution Infrared Radiation Sounder) setup. Radiances for the 19 HIRS infrared channels and a set of 42 atmospheric profiles from the “Garand dataset” have been computed.

    The mutual differences of the equivalent brightness temperatures are presented and possible causes of disagreement are discussed. In particular, the impact of path integration schemes and atmospheric layer discretization is assessed. When the continuum absorption contribution is ignored because of the different implementations, residuals are generally in the sub-Kelvin range and smaller than 0.1 K for some window channels (and all atmospheric models and lbl codes). None of the three codes turned out to be perfect for all channels and atmospheres. Remaining discrepancies are attributed to different lbl optimization techniques. Lbl codes seem to have reached a maturity in the implementation of radiative transfer that the choice of the underlying physical models (line shape models, continua etc) becomes increasingly relevant.

  • 337.
    Schwenzer, S.P.
    et al.
    Department of Physical Sciences, CEPSAR, Open University, Milton Keynes.
    Bridges, J.C.
    Space Research Centre, Department of Physics and Astronomy, University of Leicester.
    Leveille, R.
    Canadian Space Agency, St-Hubert.
    Wiens, R.C.
    Space Remote Sensing, Los Alamos National Laboratory, Los Alamos.
    Mangold, N.
    Laboratoire Planétologie et Géodynamique de Nantes, LPGN/CNRS and Université de Nantes.
    McAdam, A.
    NASA Goddard Space Flight Center.
    Conrad, P.
    NASA Goddard Space Flight Center.
    Kelley, S.P.
    Department of Physical Sciences, CEPSAR, Open University, Milton Keynes.
    Westall, F.
    Centre de Biophysique Moléculaire, CNRS, Orléans.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Instituto Andaluz de Cienccias de la Tierra (CSIC-UGR), Grenada.
    Zorzano, M.-P.
    Centro de Astrobiologia, INTA-CSIC, Madrid.
    Fluids, evaporation and precipitates at Gale Crater, Mars2015Konferensbidrag (Refereegranskat)
  • 338.
    Schwenzer, Susanne P.
    et al.
    CEPSAR, Open University, Milton Keynes, Department of Physical Sciences, CEPSAR, Open University, Milton Keynes, Open University, Milton Keynes, Department of Physical Science, The Open University, Walton Hall, Milton Keynes.
    Bridges, John C.
    Space Research Centre, University of Leicester, Space Research Centre, Department of Physics and Astronomy, University of Leicester, University of Leicester.
    Wiens, Roger C.
    Los Alamos National Laboratory, Space Remote Sensing, Los Alamos National Laboratory, Los Alamos, International Space and Response Division, Los Alamos National Laboratory.
    Conrad, Pamela G.
    Planetary Environments Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland, NASA Goddard Space Flight Center, Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland, Solar System Exploration Division, Goddard Space Flight Center, National Aeronautics and Space Administration, Greenbelt, Maryland, NASA Goddard Space Flight Center, Greenbelt, Maryland.
    Kelley, S.P.
    Department of Physical Sciences, CEPSAR, Open University, Milton Keynes.
    Leveille, R.
    Canadian Space Agency, St-Hubert.
    Mangold, Nicolas
    Laboratoire Planétologie et Géodynamique de Nantes, LPGN/CNRS and Université de Nantes, Laboratorie de Planetologie et Geodynamique de Nantes, Laboratoire Planétologie et Géodynamique, LPGNantes, CNRS UMR 6112, Université de Nantes, LPGN, CNRS, UMR 6112, Université Nantes, CNRS- UMR 6112, Laboratoire de Planétologie et Géodynamique, Université de Nantes.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    McAdam, Amy C.
    Planetary Environments Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland, Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland, NASA Goddard Space Flight Center, Solar System Exploration Division, Goddard Space Flight Center, National Aeronautics and Space Administration, Greenbelt, Maryland.
    Newsom, Horton E.
    Institute of Meteoritics, University of New Mexico, Albuquerque, Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, University of New Mexico, Albuquerque, Institute of Meteoritics, Department of Earth and Planetary Sciences, Albuquerque, New Mexico.
    Mier, Maria-Paz Zorzano
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Rapin, W.
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Spray, John G.
    Planetary and Space Science Centre, University of New Brunswick, Fredericton.
    Treiman, A.H.
    Lunar and Planetary Institute, Houston.
    Westall, F.
    Centre de Biophysique Moléculaire, CNRS, Orléans.
    Fairen, Alberto G.
    Centro de Astrobiologia, Madrid.
    Meslin, Pierre-Yves
    Institut de Recherche en Astrophysique et Planetologie, Toulouse, IRAP, CNRS/UPS, Toulouse, Université Toulouse III - Paul Sabatier, Toulouse, Université de Toulouse, UPS-OMP, IRAP.
    Fluids during diagenesis and sulfate vein formation in sediments at Gale crater, Mars2016Ingår i: Meteoritics and Planetary Science, ISSN 1086-9379, E-ISSN 1945-5100, Vol. 51, nr 11, s. 2175-2202Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We model the fluids involved in the alteration processes recorded in the Sheepbed Member mudstones of Yellowknife Bay (YKB), Gale crater, Mars, as revealed by the Mars Science Laboratory Curiosity rover investigations. We compare the Gale crater waters with fluids modeled for shergottites, nakhlites, and the ancient meteorite ALH 84001, as well as rocks analyzed by the Mars Exploration rovers, and with terrestrial ground and surface waters. The aqueous solution present during sediment alteration associated with phyllosilicate formation at Gale was high in Na, K, and Si; had low Mg, Fe, and Al concentrations—relative to terrestrial groundwaters such as the Deccan Traps and other modeled Mars fluids; and had near neutral to alkaline pH. Ca and S species were present in the 10−3 to 10−2 concentration range. A fluid local to Gale crater strata produced the alteration products observed by Curiosity and subsequent evaporation of this groundwater-type fluid formed impure sulfate- and silica-rich deposits—veins or horizons. In a second, separate stage of alteration, partial dissolution of this sulfate-rich layer in Yellowknife Bay, or beyond, led to the pure sulfate veins observed in YKB. This scenario is analogous to similar processes identified at a terrestrial site in Triassic sediments with gypsum veins of the Mercia Mudstone Group in Watchet Bay, UK.

  • 339.
    Seth, Tejaswi
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A Software Model for MATS Satellite Payload2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This thesis presents the development of a software model that simulates a payload instrument onboard the MATS satellite. The goal of this model is to provide an understanding of how the instrument impacts the measured data. This model is important for error analysis and may help in correcting the measured data for systematic flaws in the instrument.

    The software will consist of 5 main modules as follows: Scene Generator, Optics Module,Stray Light Module, Charge-Coupled Device Module and Electronics Module. This thesis forms a basic foundation for the software by designing the CCD module and a part of the Optics module, and concludes the effects of both on the output of the system. It takes into account important mission defined procedures that ultimately aim to improve image quality, resolve vertical structures in different bandwidths and analyze noise effects on the measured data.

  • 340.
    Shaik Fareedh, Junaidh
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Design, Fabrication and Modelling of Three Axis Floating Satellite Simulator2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The Floating Satellite (FloatSat) system project which has been developed at the ‘Department of Aerospace Information Technology - University of Würzburg’ is used to test, develop and implement various attitude control algorithms and strategies for small satellites [1]. The FloatSat project is designed to operate on a Frictionless air bearing surface that works with compressed air flowing distributed on a hemisphere. This hemisphere is used to replicate the space environment required for a satellite to perform its attitude control, solar panel deployment and payload mission, the FloatSat basically consist of 1 axis control and stabilization with reaction wheel. Taking FloatSat to the next level, the aim of the Thesis is to Design, Fabricate and Model a three-axis controllable FloatSat that can be contained in a Sphere for free rotation and movement. The best feature of FloatSat is that they are plug & play, easily accessible and compact size; retaining all these features in the design and extending the functionality of the product proves to be challenging. Furthermore, in the thesis it will be explained in detail about the various design consideration and selection of most feasible method on producing the final product. After the preliminary research for the design characteristics it was clear that the new FloatSat will be equipped with a controllable center of gravity mechanism that will provide balancing in any desired orientation. To obtain this feature three controllable moving masses are to be used in each axis of reaction wheel position. With Three reaction wheels and three moving masses to be equipped in the FloatSat the design challenges were high as considering the Sphere diameter is only 198mm.

    The various successful 3 axis satellite simulators are either huge or they are constrained in any one of the axis where it is positioned. On doing literature research it became clear that the sphere configuration with the given size has never been documented with promising results. It makes this thesis work to be first of its kind to perform 3 Axis FloatSat stabilization in a sphere of 198mm diameter. The FloatSat components include microcontroller STM32F4, Wi-Fi module for communication, three reaction wheel motors, three axial moving mass motor, Lithium Polymer batteries and motor controllers. 

  • 341.
    Shekhar, Mayank
    et al.
    Birbal Sahni Institute of Palaeosciences, Lucknow, India.
    Bhardwaj, Anshuman
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Singh, Shaktiman
    Institut für Kartographie, Technische Universität Dresden.
    Ranhotra, Parminder S.
    Birbal Sahni Institute of Palaeosciences, Lucknow, India.
    Bhattacharyya, Amalava
    Birbal Sahni Institute of Palaeosciences, Lucknow, India.
    Pal, Ashish K.
    Birbal Sahni Institute of Palaeosciences, Lucknow, India.
    Roy, Ipsita
    Birbal Sahni Institute of Palaeosciences, Lucknow, India.
    Martín-Torres, F. Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Armilla, Granada, Spain.
    Zorzano Mier, María-Paz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Centro de Astrobiología (INTA-CSIC), 28850, Torrejón de Ardoz, Madrid, Spain.
    Himalayan glaciers experienced significant mass loss during later phases of little ice age2017Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, artikel-id 10305Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To date, there is a gap in the data about the state and mass balance of glaciers in the climate-sensitive subtropical regions during the Little Ice Age (LIA). Here, based on an unprecedented tree-ring sampling coverage, we present the longest reconstructed mass balance record for the Western Himalayan glaciers, dating to 1615. Our results confirm that the later phase of LIA was substantially briefer and weaker in the Himalaya than in the Arctic and subarctic regions. Furthermore, analysis of the time-series of the mass-balance against other time-series shows clear evidence of the existence of (i) a significant glacial decay and a significantly weaker magnitude of glaciation during the latter half of the LIA; (ii) a weak regional mass balance dependence on either the El Niño-Southern Oscillation (ENSO) or the Total Solar Irradiance (TSI) taken in isolation, but a considerable combined influence of both of them during the LIA; and (iii) in addition to anthropogenic climate change, the strong effect from the increased yearly concurrence of extremely high TSI with El Niño over the past five decades, resulting in severe glacial mass loss. The generated mass balance time-series can serve as a source of reliable reconstructed data to the scientific community.

  • 342.
    Shematovich, V.I.
    et al.
    Institute of Astronomy, Russian Academy of Sciences, Moscow.
    Bisikalo, D.V.
    Institute of Astronomy, Russian Academy of Sciences, Moscow.
    Stenberg, G.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Dieval, Catherine
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Gérard, J-C
    LPAP, Université de Liège.
    He2+ transport in the Martian upper atmosphere with an induced magnetic field2013Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 118, nr 3, s. 1231-1242Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Solar wind helium may be a significant source of neutral helium in the Martian atmosphere. The precipitating particles also transfer mass, energy, and momentum. To investigate the transport of He2+ in the upper atmosphere of Mars, we have applied the direct simulation Monte Carlo method to solve the kinetic equation. We calculate the upward He, He+, and He2+ fluxes, resulting from energy spectra of the downgoing He2+ observed below 500 km altitude by the Analyzer of Space Plasmas and Energetic Atoms 3 instrument onboard Mars Express. The particle flux of the downward moving He2+ ions was 1–2 × 106 cm–2 s–1, and the energy flux is equal to 9–10 × 10–3 erg cm–2 s–1. The calculations of the upward flux have been made for the Martian atmosphere during solar minimum. It was found, that if the induced magnetic field is not introduced in the simulations the precipitating He2+ ions are not backscattered at all by the Martian upper atmosphere. If we include a 20 nT horizontal magnetic field, a typical field measured by Mars Global Surveyor in the altitude range of 85–500 km, we find that up to 30%–40% of the energy flux of the precipitating He2+ ions is backscattered depending on the velocity distribution of the precipitating particles. We thus conclude that the induced magnetic field plays a crucial role in the transport of charged particles in the upper atmosphere of Mars and, therefore, that it determines the energy deposition of the solar wind.

  • 343.
    Siderud, Emelie
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Upgrading a groundbased 142 GHz microwave radiometer to higher sensitivity2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The accuracy of ozone measurements in the middle atmosphere is of great importance when determining its diurnal variation. A high time resolution of the measured data is desirable and depends on the sensitivity of the receiver used to detect the ozone. This thesis aims to improve the sensitivity of a groundbased 142 GHz microwave radiometer used for measuring atmospheric ozone data. This is done by replacing the previous receiver components with a series of new components and arranging them in different setups for comparison purposes. Mechanics and wiring were changed in order to install the setups along with changes in the optics. Each test setup could be implemented as a first step towards improving the sensitivity of the radiometer. The result show that the optics contribute with an unexpected addition of noise to the measurements and hence the overall performance and improvement of the radiometer could not be determined. Suggestions are made for further work which include improving the optics and performing cryo-measurements.

  • 344.
    Singh, Shaktiman
    et al.
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Kumar, Rajesh
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Bhardwaj, Anshuman
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Sam, Lydia
    Department of Environmental Science, Sharda University, Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Shekhar, Mayank
    Birbal Sahni Institute of Palaeobotany, Lucknow.
    Singh, Atar
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Kumar, Ramesh
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Gupta, Akhilesh
    Department of Science and Technology, Technology Bhavan, New Delhi.
    Changing climate and glacio-hydrology in Indian Himalayan Region: a review2016Ingår i: Wiley Interdisciplinary Reviews: Climate Change, ISSN 1757-7780, E-ISSN 1757-7799, Vol. 7, nr 3, s. 393-410Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study presents a comprehensive review of the published literature on the evidences of a changing climate in the Indian Himalayan Region (IHR) and its impacts on the glacio-hydrology of the region. The IHR serves as an important source of fresh water for the densely populated areas downstream. It is evident from the available studies that temperature is significantly increasing in all parts of the IHR, whereas precipitation is not indicative of any particular spatiotemporal trend. Glacio-hydrological proxies for changing climate, such as, terminus and areal changes of the glaciers, glacier mass balance, and streamflow in downstream areas, highlight changes more evidently in recent decades. On an average, studies have predicted an increase in temperature and precipitation in the region, along with increase in streamflow of major rivers. Such trends are already apparent in some sub-basins of the western IHR. The region is particularly vulnerable to changing climate as it is highly dependent on snow and glacier melt run-off to meet its freshwater demands. We present a systematic review of key papers dealing with changing temperature, precipitation, glaciers, and streamflow in the IHR. We discuss these interdisciplinary themes in relation to each other, in order to establish the present and future impacts of climatic, glaciological, and hydrological changes in the region.

  • 345.
    Slapak, Rikard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    O⁺ heating in the high altitude cusp and mantle due to wave-particle interaction2011Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis is composed of three articles, which have the common denominator that they are studies of heating of oxygen ions in the high altitude cusp and mantle in the terrestrial magnetosphere. All data analysis are based on observational data from the Cluster satellites. Oxygen ions originate in the ionosphere, from where they flow up along open cusp field lines. This upflowing ionospheric plasma is generally gravitationally bound and will return as ionospheric downflow. However, if the plasma is sufficiently energized it may overcome gravity and reach the magnetosphere. Further energization is able to put the plasma on trajectories leading downstream along the magnetotail, which may cause the plasma to escape into the magnetosheath. This thesis considers energization of oxygen ions through wave-particle interactions. We show that the average electric spectral densities in the altitude range of 8-15 Earth radii are able to explain the average perpendicular temperatures, using a simple gyroresonance model and 50% of the observed spectral density at the O+ gyrofrequency. We also show that the phase velocities derived from the observed low frequency electric and magnetic fields are consistent with Alfvén waves. Strong heating is sporadic and spatially limited. For three case studies of strong heating, we show that the regions of enhanced wave activity are at least one order of magnitude larger than the gyroradius of the ions, which is a condition for the gyroresonance model to be valid. An analysis indicates that enhanced perpendicular temperatures can be observed over several Earth radii after heating has ceased, suggesting that high perpendicular-to-parallel temperature ratio is not necessarily a sign of local heating. This also explains why we sometimes observe enhanced temperatures and low spectral densities. Three events of very high temperatures and simultaneously observed high spectral densities were studied, and we showed that the temperatures could be explained with the simple gyrofrequency model. We have also provided average diffusion coefficients at different altitudes, which can be used for ion heating and outflow modeling.

  • 346.
    Slapak, Rikard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    O+ heating, outflow and escape in the high altitude cusp and mantle2013Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The Earth and its atmosphere are embedded in the magnetosphere, a region in space dominated by the geomagnetic field, shielding our planet as it acts to deflect the energetic solar wind. Even though the atmosphere is protected from direct interaction with the solar wind it is indirectly affected by significant magnetosphere-solar wind interaction processes, causing constituents of the upper atmosphere to flow up into the magnetosphere. The fate of the atmospheric originating ions is interesting from a planetary evolution point of view. If the upflowing ions in the magnetosphere are to escape into the solar wind they need to not only overcome gravity, but also the magnetic forces, and therefore need to be energized and accelerated significantly. The subject of this thesis is analysis of oxygen ions (O+) and wave field observations in the high altitude cusp/mantle and in the high latitude dayside magnetosheath of Earth, investigating magnetospheric processes behind ion heating, outflow and escape. Most data analysis is based on observational data from the Cluster satellites, orbiting the Earth and altitudes corresponding to different key regions of the magnetosphere and the immediate solar wind environment. The mechanism behind O+ heating mainly discussed in this thesis is energization through interactions between the ions and low-frequency waves. The average electric spectral densities in the altitude range of 8-15 Earth radii are able to explain the average perpendicular temperatures, using a gyroresonance model and 50% of the observed spectral density at the O+ gyrofrequency. Strong heating is sporadic and spatially limited. The regions of enhanced wave activity are at least one order of magnitude larger than the local gyroradius of the ions, which is a necessary condition for the gyroresonance model to be valid. An analysis indicates that enhanced perpendicular temperatures can be observed over several Earth radii after heating has ceased, suggesting that high perpendicular-to-parallel temperature ratio is not necessarily a sign of local heating. This also explains why we sometimes observe enhanced temperatures and low spectral densities. We also show that the phase velocities derived from the observed low frequency electric and magnetic fields are consistent with Alfvén waves. Outflowing ions flow along magnetic field lines leading downstream in the magnetotail, where the ions may convect into the plasma sheet and be brought back toward Earth. However, the effective heating in the cusp and mantle provides a majority of the O+ enough acceleration to escape into the solar wind and be lost, rather than entering the plasma sheet. The heating can actually be effective enough to allow outflowing cusp O+ to escape immediately from the high altitude cusp and mantle along recently opened magnetic field lines, facilitating a direct coupling between the magnetospheric plasma and interplanetary space. Observations in the shocked and turbulent solar wind (the magnetosheath) reveals hot O+ flowing downstream and approximately tangentially to the magnetopause and often close to it. An estimated total flux of O+ in the high-latitude magnetosheath of 0.7 ·1025 s-1 is significant in relation to the observed cusp outflows at lower altitudes, pointing to that escape of hot O+ from the cusp and mantle into the dayside magnetosheath being an important loss route.

  • 347.
    Slapak, Rikard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Gunell, H.
    Belgian Institute for Space Aeronomy, Avenue Circulaire, Brussels.
    Hamrin, Maria
    Department of Physics, Umeå University.
    Observations of multiharmonic ion-cyclotron waves due to inverse ion-cyclotron damping in the northern magnetospheric cusp2017Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 44, nr 1, s. 22-29Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a case study of inverse ion-cyclotron damping taking place in the northern terrestrial magnetospheric cusp, exciting waves at the ion-cyclotron frequency and its harmonics. The ion-cyclotron waves are primarily seen as peaks in the magnetic-field spectral densities. The corresponding peaks in the electric-field spectral densities are not as profound, suggesting a background electric field noise or other processes of wave generation causing the electric spectral densities to smoothen out more compared to the magnetic counterpart. The required condition for inverse ion-cyclotron damping is a velocity shear in the magnetic field-aligned ion-bulk flow, and this condition is often naturally met for magnetosheath influx in the northern magnetospheric cusp, just as in the presented case. We note that some ion-cyclotron wave activity is present in a few similar shear events in the southern cusp, which indicates that other mechanisms generating ion-cyclotron waves may also be present during such conditions.

  • 348.
    Slapak, Rikard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Hamrin, Maria
    Department of Physics, Umeä University.
    Pitkänen, Timo
    Department of Physics, Umeä University.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics, Kiruna.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Karlsson, Tomas
    Space and Plasma Physics, School of Electrical Engineering, Royal Institute of Technology, Stockholm.
    Schillings, Audrey
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Quantification of the total ion transport in the near-Earth plasma sheet2017Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 35, nr 4, s. 869-877Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recent studies strongly suggest that a majority of the observed O+ cusp outflows will eventually escape into the solar wind, rather than be transported to the plasma sheet. Therefore, an investigation of plasma sheet flows will add to these studies and give a more complete picture of magnetospheric ion dynamics. Specifically, it will provide a greater understanding of atmospheric loss. We have used Cluster spacecraft 4 to quantify the H+ and O+ total transports in the near-Earth plasma sheet, using data covering 2001-2005. The results show that both H+ and O+ have earthward net fluxes of the orders of 1026 and 1024 s -1, respectively. The O+ plasma sheet return flux is 1 order of magnitude smaller than the O+ outflows observed in the cusps, strengthening the view that most ionospheric O+ outflows do escape. The H+ return flux is approximately the same as the ionospheric outflow, suggesting a stable budget of H+ in the magnetosphere. However, low-energy H+, not detectable by the ion spectrometer, is not considered in our study, leaving the complete magnetospheric H+ circulation an open question. Studying tailward flows separately reveals a total tailward O+ flux of about 0. 5 × 1025 s -1, which can be considered as a lower limit of the nightside auroral region O+ outflow. Lower velocity flows ( < 100kms -1) contribute most to the total transports, whereas the high-velocity flows contribute very little, suggesting that bursty bulk flows are not dominant in plasma sheet mass transport.

  • 349.
    Slapak, Rikard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Nilsson, Hans
    Swedish Institute of Space Physics, Kiruna.
    Schillings, Audrey
    Swedish Institute of Space Physics, Kiruna.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics, Kiruna.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Dandouras, Iannis
    CNSR, Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Atmospheric outflow from the terrestrial magnetosphere: implications forescape on evolutionary time scales2017Konferensbidrag (Refereegranskat)
  • 350.
    Slapak, Rikard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    A statistical study on O+ flux in the dayside magnetosheath2013Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 31, s. 1005-1010Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Studies on terrestrial oxygen ion (O+) escape into the interplanetary space have considered a number of different escape paths. Recent observations however suggest a yet insufficiently investigated additional escape route for hot O+: along open magnetic field lines in the high altitude cusp and mantle. Here we present a statistical study on O+ flux in the high-latitude dayside magnetosheath. The O+ is generally seen relatively close to the magnetopause, consistent with observations of O+ flowing primarily tangentially to the magnetopause. We estimate the total escape flux in this region to be ~ 7 × 1024 s−1, implying this escape route to significantly contribute to the overall total O+ loss into interplanetary space.

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