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  • 401.
    Pontoni, Angèle
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Evolution of the signal induced by ChemCam on Mars as a function of focus2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    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.

  • 402.
    Pope, Charles
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Calibration and Uncertainty Analysis of a Spacecraft Attitude Determination Test Stand2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    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.

  • 403.
    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 wake2014Inngår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 41, nr 11, s. 3766-3773Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 404.
    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 Analyser2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    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. 

  • 405.
    Ramavaram, Harish Rao
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Software and Control Design for 2-D Floating Satellite Simulator2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 406.
    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 SONATE2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    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.

  • 407.
    Ricchi, Mattia
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Performance Scatter Analysis using 3D CFD Simulations2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this report the performance scatter of a turbine used in the turbo pump for PROMETHEUS has been analyzed. The study is split in two phases:

    • First only the rotor has been modified in dimensions;

    • Lastly both stator and rotor have been modified together.

    In the first case, Numeca Autogrid 12.1 has been used for quickly produce meshes of the different configurations of the rotor that are matched always with a nominal stator. After that, 3D CFD simulations have been run using Ansys CFX 19.1, for a total of nine cases combining together the rotor’s geometry deviations.For the second phase, the method of mesh deformation has been used in order to obtain the geometry variations needed for both stator and rotor. The stator has been transformed in the nozzle throat and outlet sections, the rotor has been varied in the same manner as per the first phase with the difference that only the blade thickness has been displaced using the mesh deformation method, taking advance of the work done in phase one for hub and shroud deviations.The advantage of using mesh deformation instead of variations using CAD tool, is that this method is built-in in Ansys CFX 19.1 and allows the aerodynamic designers to be more autonomous from the CAD designers.The results are then post processed and several tables are provided as output for comparing them later on and evaluate the changes computed. As a last step, all the results are collected and run into optiSLang in order to compute a sensitivity analysis, so that it is possible to evaluate what is the most influent input parameter for each output.

  • 408.
    Rijal, Samundra
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Case Study: Conceptual Ground Station Design for N66 Connect AB2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    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.

  • 409.
    Romero, Faviola
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    In-orbit performance analysis of the image sensors from Pleiades mission2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    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. 

  • 410.
    Roos, Tobias
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A Framework for Autonomous Heterogeneous Robot Teams2018Konferansepaper (Fagfellevurdert)
  • 411.
    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 data2007Inngår i: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 133, nr Suppl.2, s. 151-162Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 412.
    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 measurements2009Inngår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 2, nr 2, s. 621-637Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 413.
    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 WIRA2014Inngår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 7, s. 4491-4505Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 414.
    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 WIRA2014Inngår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 7, s. 7717-7752Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 415.
    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 data2018Inngår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 61, nr 8, s. 2050-2056Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 416.
    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, Toronto, Canada.
    Large-scale Altitude Distribution Profile of Auroral Parallel Electric Potentials: A Statistical Analysis of Cluster Data2019Inngår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 64, nr 2, s. 378-384Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is generally believed that the heart of the Auroral Acceleration Region (AAR) is located between 5000 and 8000 km altitude above the auroral oval. Various altitude distribution profiles are suggested by different theories, including the transition layer model, which predicts that the strongest electric fields can be found at about 1 RE, and can vary depending on the plasma and geomagnetic conditions. However, there have been no specific experimental results that cover regions both below and well above such altitude. This paper presents a method for obtaining such a profile from AAR satellite crossings, applies it to a data set gathered from 116 Cluster spacecraft encounters with acceleration potential structures, and discusses the results. The crossings cover an altitude range between 0.63 RE and 2.9 RE. The outcome is the first empirical altitude distribution profile of the auroral acceleration potentials. The results suggest that the region within the altitude range of 0.9245 RE and 1.158 RE statistically contains 30% of the total potential, which is the largest fraction of the parallel potentials among all altitude segments of the same size. The altitude which equally divides the distribution of acceleration potentials was found at 1.076 RE (6863 km). The obtained parallel potential distribution is in agreement with both the magnetic mirror force theory and the transition layer model, and can hence provide a proper baseline for future missions to the AAR.

  • 417.
    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 Nanosatellites2017Inngår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 59, nr 5, s. 1173-1188Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 418.
    Sagaria, Shehna
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mechanical Design of a Hybrid Navigation System for the Reusability Launch Vehicle Technology Demonstrator: ReFEx2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Space missions are always cost depended and one of the effective ways for cost control is to reuse the launch system completely or partially. DLR, the German Aerospace Center, is currently developing a flight experiment called Reusability Flight Experiment (ReFEx), which is a winged re-entry launch system. One of the main features of this vehicle is its Hybrid Navigation System (HNS), an autonomous navigation system that is vital to vehicle re-entry. The main goal of this thesis is to develop a highly integrated, compact, and self-contained mechanical enclosure to accommodate all the components of the hybrid navigation system, except the external sensors and antenna. Integrating the enclosure model to the subsystem models, a mechanical design of HNS is developed.

    The enclosure is to be integrated within the ReFEx, close to the Guidance and Control system. The mechanical design is considered based on the different requirements of the HNS components, like, the orientation, the accessibility for electrical connections and reconnections, and ease of integration. Based on the component and system requirements, an initial outline of the HNS box (HNS dummy) is created. The HNS components are then designed and included into the HNS dummy. Following this, different configurations are studied for the HNS components’ accommodation in the box. A final flight accommodation configuration is chosen based on the structural rigidity and accessibility to different components. Based on the configuration chosen, an initial design is generated through various design iterations using CATIA V5, with proper component supports. This is followed by the preliminary enclosure design, considering the different loads that are subjected to it during flight. This design is checked with the ReFEx outer structure to ensure proper mechanical clearance margins.

    After finalizing the design of the HNS enclosure, a detail enclosure design is generated where the individual enclosure parts are defined. This enclosure model is then integrated with the HNS sensors and electronic component models to produce a detailed HNS mechanical model. The mechanical fitting and physical attributes of the detailed HNS model is tested by producing a prototype though 3D printing technology. The enclosure prototype is assembled in house with all the HNS components using different mechanical fasteners. Based on the observations from the prototype, the HNS production model was created. The production model was used to generate subsequent part drawings for the mechanical production processes. An assembly process flow for the HNS integration is developed based on the prototype assembly for the flight model. The developed HNS model and the corresponding part drawings would be used for the HNS development. The HNS assembly and integration would be according to the assembly process plan developed.

  • 419.
    Saillenfest, Melaine
    et al.
    IMCCE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC Univ. Paris 06, LAL, Université de Lille, Paris, 75014, France.
    Tabone, B
    LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC Univ. Paris 06, Paris, 75014, France.
    Behar, Etienne
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Swedish Institute of Space Physics, Kiruna, Sweden.
    Solar wind dynamics around a comet: The paradigmatic inverse-square-law model2018Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 617, artikkel-id A99Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aims.

    Observations of solar protons near comet 67P/Churyumov-Gerasimenko (67P) by the Rosetta spacecraft can be modelled by the planar motion in an effective magnetic field proportional to 1/r(2). We aim to provide a thorough study of such dynamics, with a clear description of the behaviour of an incoming flux of particles. We will be able, then, to calibrate the free parameters of the model to Rosetta observations. 

    Methods.

    Basic tools of dynamical analysis are used. They lead to a definition of the relevant parameters for the system and a classification of the possible types of trajectories. Using the so-obtained formalism, the structures formed by a flux of particles coming from infinity can be studied. 

    Results.

    All the trajectories are parametrised by two characteristic radii, r(E) and r(C), derived from first integrals. There are three different types of motion possible divided by a separatrix corresponding to r(E) = r(C). An analytical expression of the trajectories, defined by an integral, is developed. Using this formalism, the application to a flux of particles coming from infinity (modelling the incident solar wind) gives one free parameter only, the radius r(E), which scales the problem. A circular cavity of radius 0.28 r(E) is created, as well as an overdensity curve (analogous to a caustic in optics). At each observation time, r(E) can be calibrated to Rosetta plasma measurements, giving a qualitative understanding of the solar particle dynamics (incoming direction, cavity and density map). We also deduce that, in order to properly capture the essence of the dynamics, numerical simulations of the solar wind around a comet must use simulation boxes much larger than r(E) and grids much finer than r(E).

  • 420.
    Sam, Lydia
    et al.
    Institut für Kartographie, Technische Universität Dresden.
    Bhardwaj, Anshuman
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Kumar, Rajesh
    Department of Environmental Science, Sharda University.
    Buchroithner, Manfred F.
    Institut für Kartographie, Technische Universität Dresden.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Armilla, Granada .
    Heterogeneity in topographic control on velocities of Western Himalayan glaciers2018Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, nr 1, artikkel-id 12843Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Studies of the seasonal and annual patterns of glacier velocities improve our understanding of the ice volume, topography, responses to climate change, and surge events of glaciers. Such studies are especially relevant and equally rare for the Himalayan glaciers, which supply many rivers that sustain some of the most heavily populated mountainous regions in the world. In particular, the control of the hypsometric distribution of geomorphometric parameters, such as slope, aspect, and curvature, on the dynamics of Himalayan glaciers have never been studied so far, at the river basin scale. Here, we present the degree to which topographic and hypsometric parameters affect the seasonal and annual average flow velocities of 112 glaciers in the Baspa River basin in the Western Indian Himalaya by analysing Global Land Ice Velocity Extraction from Landsat 8 (GoLIVE) datasets for the years 2013–2017. We observe, (i) significant heterogeneity in topographic controls on the velocities of these glaciers, (ii) elevation and the seasons play important roles in regulating the degree to which morphometric parameters (slope, aspect, and curvature) affect these velocities, (iii) a possible polythermal regime promoting both sliding and deformational forms of motion in a majority of these glaciers, and (iv) a detailed analysis of complex topographic controls within various elevation zones using a novel hypso-morphometric approach. These findings can help us to better model the dynamics of Himalayan glaciers and their responses to the future climatic scenarios. The inferences also suggest the need to incorporate dynamic topography in glacio-hydrological models in the wake of constant glacial evolutions.

  • 421.
    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 Terrain2016Inngår i: Journal of the Indian Society of Remote Sensing, ISSN 0255-660X, Vol. 44, nr 3, s. 409-420Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 422.
    Sam, Lydia
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Kumar, Rajesh
    Bhardwaj, Anshuman
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Climate and Remotely Sensed Markers of Glacier Changes in the Himalaya2019Inngår i: Environmental Change in the Himalayan Region, Springer, 2019, s. 65-88Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    The study of past and future climatic variations in the Hindu Kush–Himalayan (HKH) region is a well-documented topic of scientific research. Recent studies have highlighted the significantly higher rates of warming in the HKH region compared to the global average. The HKH region has the largest reserves of glacial ice outside the poles. These glaciers are predominantly known to be sensitive indicators of changing regional and global climate. The large geographical extent, high elevation and perennial inclemency in weather conditions project remote sensing as the only viable option to study glacial characteristics periodically on a regional scale. The present chapter starts with a review of significant studies to assess the extent of climate change in the HKH. Climate-sensitive glacial markers which can be studied using remote sensing are identified. The chapter focuses on the key markers such as changes in glacier extents, glacier facies and supraglacial debris, and mass balance and thickness. The chapter examines these markers separately with respect to changing climate through recent remote sensing-based studies. It provides an overview of recent studies which deal with regional scale glaciological monitoring and assessment. The conclusive section of the chapter suggests the future role of remote sensing applications in studying these markers of climate change. The chapter uses recent studies to highlight key aspects that should be kept in perspective while undertaking remotely sensed glacial assessments.

  • 423.
    Saradagi, Akshit
    et al.
    Indian Institute of Technology System (IIT System), Dept Elect Engn, Madras 600036, Tamil Nadu, India.
    Muralidharan, Vijay
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Krishnan, Vishaal
    University of California San Diego,Dept Mech Engn, La Jolla, CA 92093 USA .
    Menta, Sandeep
    Indian Institute of Technology System (IIT System), Dept Elect Engn, Madras 600036, Tamil Nadu, India.
    Formation Control and Trajectory Tracking of Nonholonomic Mobile Robots2018Inngår i: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 26, nr 6, s. 2250-2258Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this brief, we design Lyapunov-based control laws to achieve two multi-objective tasks for a network of open-loop unstable, nonholonomic mobile inverted pendulum (MIP) robots, using a connected undirected graph for inter-agent communication. Using the first protocol, translationally invariant formations are achieved along with the synchronization of attitudes and heading velocities to desired values. Using the second protocol, the robots move into a formation and asymptotically track a trajectory. The control laws are based on the kinematic model of the mobile robot, and control torques for the MIPs are extracted using a two-loop control architecture. Both the protocols guarantee boundedness of the linear heading velocity, which is necessary for the stability of the two-loop control architecture. The proposed control laws are experimentally validated on indigenously built MIP robots.

  • 424.
    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 variation2012Inngår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 5, nr 11, s. 2809-2825Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 425.
    Satpute, Sumeet
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. University of Toronto, Toronto, Canada.
    Concurrent co-location maneuver planning for geostationary satellites2018Inngår i: Acta Astronautica, ISSN 0094-5765, E-ISSN 1879-2030Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper details the development of a planning algorithm for multiple co-located geostationary satellites to perform station keeping and momentum unloading maneuvers concurrently. The objective is to minimize the overall fuel consumption while guaranteeing a safe separation distance between the satellites within a specific geostationary slot, as well as managing their stored angular momentum to maintain their nadir pointing orientation. The algorithm adopts the leader-follower architecture to define relative orbital elements of the satellites equipped with four gimbaled on-off electric thrusters, and solves a convex optimization problem with inequality constraints, including momentum unloading requirements, to determine the optimal maneuvers. The proposed algorithm is verified, in terms of fuel consumption, constraints enforcement and satellites performance, using numerical simulations that take into account dominant perturbations in the geostationary environment.

  • 426.
    Satpute, Sumeet
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. University of Toronto.
    Concurrent Manuever Planning for Geostationary Satellites2018Inngår i: 2018 IEEE Aerospace Conference, IEEE Computer Society, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, a planning method is developed using convex optimization for concurrent station keeping and momentum unloading maneuvers of geostationary satellites equipped with on-off electric thrusters. Prediction models for coupled orbital and attitude dynamics are used for generating concurrent maneuver plans. Since the satellite's attitude dynamics is fast compared to the orbital dynamics, a dual-rate model is proposed for addressing time scale differences of the two coupled systems. Based on such a model, a convex optimization problem is formulated and solved in a receding horizon form, which minimizes the fuel consumption and the number of required maneuvers. The proposed algorithm is verified using numerical simulations, taking into account major perturbations in the geostationary environment. The performance of the proposed method is analyzed in terms of fuel consumption and constraint enforcement.

  • 427.
    Satpute, Sumeet
    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, Toronto, Canada.
    Concurrent Station Keeping and Momentum Management of Geostationary Satellites2019Inngår i: The Journal of the astronautical sciences, ISSN 0021-9142, Vol. 66, nr 3, s. 341-360Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article discusses a convex-optimization-based planning method for a geostationary satellite to determine station keeping and momentum unloading maneuvers concurrently. The proposed optimization algorithm incorporates a dual-rate prediction model to address the time scaling difference between the coupled slow orbital and fast attitude dynamics. The use of combined prediction model in the optimization problem facilitates to include state constraints accounting for the desired orbital and momentum unloading requirements. Maneuver plans are determined by solving a convex optimization problem in a receding horizon control form. The main objective of the proposed algorithm is to minimize fuel consumption while managing the stored momentum, in order to maintain a satellite in a tight station keeping window and nadir pointing attitude configuration. Numerical simulations are performed to validate the proposed optimization algorithm in terms of fuel consumption and constraint enforcement.

  • 428.
    Satpute, Sumeet
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Optimal maneuver planning for the co-location of geostationary satellites2018Konferansepaper (Fagfellevurdert)
  • 429.
    Schafer, Ewan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Stereoscopic Light Curve Analysis of Space Debris Objects2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 430.
    Schell, Sebastian
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Generation of Satellite Configuration Files from XML Files2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 431.
    Schilling, Klaus
    et al.
    Julius-Maximilians Universität Würzburg, Informatik VII: Robotics & Telematics.
    Barabash, Victoria
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Space Master: An International, Interdisciplinary Master in Space Science and Technology2017Konferansepaper (Annet vitenskapelig)
    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.

  • 432.
    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, med artikler (Annet vitenskapelig)
    Abstract [en]

    The region of space dominated by the Sun's magnetic field is called the heliosphere. It envelops the entire solar system including Earth. Therefore, a strong coupling exists between the Sun and our planet. The Sun continuously ejects particles, the solar wind, and when these high energy particles hit Earth, the magnetosphere (the region around the Earth governed by the geomagnetic field) is affected. When the solar wind is enhanced this disturbs the magnetosphere and perturbations can be seen also in ground-based observations.

    The upper atmosphere is subjected to solar radiation that ionise the neutral atoms and molecules, this region is referred to as the ionosphere. In the ionosphere, some of the heavier ion populations, such as O+, are heated and accelerated through several processes and flow upward. In the polar regions these mechanisms are particularly efficient and when the ions have enough energy to escape the Earth's gravity, they move outward along open magnetic field lines and may be lost into interplanetary space. Ion outflow in general has already been well studied, however, ion outflow under extreme magnetospheric conditions has not been investigated in detail.

    Disturbed magnetospheric conditions correlate with solar active periods, such as coronal holes or the development of solar active regions. From these regions, strong ejections called coronal mass ejections (CMEs) emerge. When these extreme events interact with Earth, they produce a compression of the magnetosphere as well as reconnection between the terrestrial magnetic field lines and the interplanetary magnetic field (IMF) lines, which most of the time leads to geomagnetic storms. The amounts of incoming solar particles and energy increase during geomagnetic storms and we also observe an increase in the O+ outflow.

    Our observations are made with the Cluster mission, a constellation of 4 satellites flying around Earth in the key magnetospheric regions where ion outflow is usually observed. In this thesis, we estimate O+ outflow under disturbed magnetospheric conditions and for several extreme geomagnetic storms. We find that O+ outflow lost into the solar wind increases exponentially with enhanced geomagnetic activity (Kp index) and increases about 2 orders of magnitude during extreme geomagnetic storms.

  • 433.
    Schillings, Audrey
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Swedish Institute of Space Physics, Kiruna, Sweden.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Swedish Institute of Space Physics, Kiruna, Sweden.
    Slapak, R.
    EISCAT Scientific Association, Kiruna, Sweden.
    Wintoft, P.
    Swedish Institute of Space Physics, Lund, Sweden.
    Yamauchi, M.
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Wik, M.
    Swedish Institute of Space Physics, Lund, Sweden.
    Dandouras, I.
    IRAP, Université de Toulouse, CNRS, UPS, CNES, France.
    Carr, C.M.
    Department of Physics, Imperial College London, London, United Kingdom.
    O+ Escape During the Extreme Space Weather Event of 4–10 September 20172018Inngår i: Space Weather: The international journal of research and applications, ISSN 1542-7390, E-ISSN 1542-7390, Vol. 16, nr 9, s. 1363-1376Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have investigated the consequences of extreme space weather on ion outflow from the polar ionosphere by analyzing the solar storm that occurred early September 2017, causing a severe geomagnetic storm. Several X-flares and coronal mass ejections were observed between 4 and 10 September. The first shock—likely associated with a coronal mass ejection—hit the Earth late on 6 September, produced a storm sudden commencement, and began the initial phase of the storm. It was followed by a second shock, approximately 24 hr later, that initiated the main phase and simultaneously the Dst index dropped to Dst = −142 nT and Kp index reached Kp = 8. Using COmposition DIstribution Function data on board Cluster satellite 4, we estimated the ionospheric O+ outflow before and after the second shock. We found an enhancement in the polar cap by a factor of 3 for an unusually high ionospheric O+ outflow (mapped to an ionospheric reference altitude) of 1013 m−2 s−1. We suggest that this high ionospheric O+ outflow is due to a preheating of the ionosphere by the multiple X-flares. Finally, we briefly discuss the space weather consequences on the magnetosphere as a whole and the enhanced O+ outflow in connection with enhanced satellite drag.

  • 434.
    Schillings, Audrey
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. 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 observations2017Inngår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 5, nr 6, s. 1341-1352Artikkel i tidsskrift (Fagfellevurdert)
    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).

  • 435.
    Schillings, Audrey
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Swedish Institute of Space Physics, Kiruna.
    Slapak, Rikard
    EISCAT Scientifc Association, Kiruna.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Swedish Institute of Space Physics, Kiruna.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics, Kiruna.
    Dandouras, Iannis
    IRAP, Université de Toulouse, CNRS, UPS, CNES, Toulouse, France.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Earth atmospheric loss through the plasma mantle and its dependence on solar wind parameters2019Inngår i: Earth, Planets and Space, Vol. 71, nr 70Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Atmospheric loss and ion outfow play an important role in the magnetospheric dynamics and in the evolution of the atmosphere on geological timescales—an evolution which is also dependent on the solar activity. In this paper, we investigate the total O+ outfow [s−1 ] through the plasma mantle and its dependency on several solar wind param‑ eters. The oxygen ion data come from the CODIF instrument on board the spacecraft Cluster 4 and solar wind data from the OMNIWeb database for a period of 5 years (2001–2005). We study the distribution of the dynamic pressure and the interplanetary magnetic feld for time periods with available O+ observations in the plasma mantle. We then divided the data into suitably sized intervals. Additionally, we analyse the extreme ultraviolet radiation (EUV) data from the TIMED mission. We estimate the O+ escape rate [ions/s] as a function of the solar wind dynamic pressure, the interplanetary magnetic feld (IMF) and EUV. Our analysis shows that the O+ escape rate in the plasma mantle increases with increased solar wind dynamic pressure. Consistently, it was found that the southward IMF also plays an important role in the O+ escape rate in contrast to the EUV fux which does not have a signifcant infuence for the plasma mantle region. Finally, the relation between the O+ escape rate and the solar wind energy transferred into the magnetosphere shows a nonlinear response. The O+ escape rate starts increasing with an energy input of approxi‑ mately 1011W.

  • 436.
    Schillings, Audrey
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Swedish Institute of Space Physics (IRF), Kiruna, Sweden .
    Slapak, Rikard
    EISCAT Scientific Association, Kiruna.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Swedish Institute of Space Physics (IRF), Kiruna.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics (IRF), Kiruna.
    Dandouras, Iannis
    Université de Toulouse, CNRS, UPS, CNES, Toulouse, France.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Earth atmospheric loss through the plasma mantle and its dependence onsolar wind parameters2019Konferansepaper (Fagfellevurdert)
  • 437.
    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 observations2017Konferansepaper (Fagfellevurdert)
  • 438.
    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 evaluation2014Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 137, s. 29-50Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 439.
    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 codes2013Inngår i: International Radiation Symposium: Radiation Processes in the Atmosphere and Ocean, IRS 2012, Berlin, Germany; 6 August 2012-10 August 2012, 2013, s. 119-122Konferansepaper (Fagfellevurdert)
    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

  • 440.
    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 codes2018Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 211, s. 64-77Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 441.
    Schwamb, Megan E.
    et al.
    Gemini Observatory, Northern Operations Center, Hilo, USA.
    Hsieh, Henry
    Planetary Science Institute, Tucson, USA.
    Bannister, Michele T.
    Queen's University Belfast, Belfast, UK.
    Bodewits, Dennis
    Auburn University, Auburn, USA.
    Chesley, Steven R
    California Institute of Technology, Pasadena, USA.
    Fraser, Wesley C.
    Queen's University Belfast, Belfast, UK.
    Granvik, Mikael
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. University of Helsinki, Finland.
    Jones, R. Lynne
    University of Washington, Seattle, USA.
    Jurić, Mario
    University of Washington, Seattle, USA.
    Kelley, Michael S.P.
    University of Maryland, USA.
    Ragozzine, Darin
    Brigham Young University, Provo, USA.
    Trilling, David E.
    Northern Arizona University, Flagstaff, USA.
    Volk, Kathryn
    University of Arizona, Tucson, USA.
    A Software Roadmap for Solar System Science with the Large Synoptic Survey Telescope2019Inngår i: Research Notes of the AAS, E-ISSN 2515-5172, Vol. 3, nr 3, artikkel-id 51Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The 8.4 m Large Synoptic Survey Telescope (LSST) will provide an unprecedented view of the Solar System (Ivezić et al. 2008; LSST Science Collaboration et al. 2009). LSST will detect millions of asteroids and tens of thousands of distant Solar System bodies, within approximately 16 and 24.5 mag (in r-band). Over a ten year period, most of these minor planets will receive hundreds of observations divided between 6 filters (ugrizy). What specifically LSST project will deliver for Solar System detections will soon be updated in the LSST Data Products Definition Document (DPDD; Jurić et al. 2013). A preliminary version of the new LSST Solar System data products schema is available at http://ls.st/ssd and http://ls.st/oug.

    The LSST Solar System Science Collaboration (SSSC; http://www.lsstsssc.org) produced a science roadmap (Schwamb et al. 2018) which outlines the collaboration's highest ranked research priorities utilizing LSST. To achieve these science goals, the SSSC has identified crucial software products and tools that will be required but will not be provided by the LSST project. These will have to be developed by the SSSC and the broader planetary community. To spur this effort, we present below this list of LSST community software development tasks.

  • 442.
    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, Mars2015Konferansepaper (Fagfellevurdert)
  • 443.
    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, Mars2016Inngår i: Meteoritics and Planetary Science, ISSN 1086-9379, E-ISSN 1945-5100, Vol. 51, nr 11, s. 2175-2202Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 444.
    Seth, Tejaswi
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A Software Model for MATS Satellite Payload2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    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.

  • 445.
    Shaik Fareedh, Junaidh
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Design, Fabrication and Modelling of Three Axis Floating Satellite Simulator2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    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. 

  • 446.
    Sharma, Aman
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    System Identification of a Micro Aerial Vehicle2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The purpose of this thesis was to implement an Model Predictive Control based system identification method on a micro-aerial vehicle (DJI Matrice 100) as outlined in a study performed by ETH Zurich. Through limited test flights, data was obtained that allowed for the generation of first and second order system models. The first order models were robust, but the second order model fell short due to the fact that the data used for the model was not sufficient.

  • 447.
    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 age2017Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, artikkel-id 10305Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 448.
    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 field2013Inngår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 118, nr 3, s. 1231-1242Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 449.
    Siderud, Emelie
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Upgrading a groundbased 142 GHz microwave radiometer to higher sensitivity2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    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.

  • 450.
    Singh, Shaktiman
    et al.
    Department of Environmental Science, Sharda University, India. Institut für Kartographie, Technische Universität Dresden, Germany.
    Kumar, Rajesh
    Department of Environmental Science, Sharda University, India.
    Bhardwaj, Anshuman
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Kumar, Ramesh
    Department of Environmental Science, Sharda University, India.
    Singh, Atar
    Department of Environmental Science, Sharda University, India.
    Changing climate and glacio-hydrology: a case study of Shaune Garang basin, Himachal Pradesh2018Inngår i: International Journal of Hydrology Science and Technology, ISSN 2042-7808, E-ISSN 2042-7816, Vol. 8, nr 3, s. 258-272Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The rise in temperature is already evident in Himalaya with rate of increase varying seasonally and spatially. Changes in precipitation are also evident with no clear trend. Several studies in different parts of Himalayas suggest that the glaciers are retreating in general with few exceptions as response to changes in temperature and precipitation. The stream flow in river basins in Indian Himalayan region (IHR) is already showing changes in studies undertaken in the last few decades. Use of glacio-hydrological models gives opportunity to estimate stream flow in glaciated river basins and understand the changes. The present study deals with estimation of discharge in Shaune Garang Basin, Himachal Pradesh using a glacio-hydrological model based on degree day factors. The model was used to estimate long term average of melt season discharge (1985-2007) in the basin. The modelled discharge shows good correlation with measured discharge for simulation period except for first year of comparison.

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