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  • 1.
    Abudayyeh, H.A.
    et al.
    Department of Physics, Al-Quds University, Jerusalem.
    Barghouthi, I.A.
    Department of Physics, Al-Quds University, Jerusalem.
    Slapak, Rikard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Nilsson, Hans
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Centrifugal acceleration at high altitudes above the polar cap: A Monte Carlo simulation2015In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, no 8, p. 6409-6426Article in journal (Refereed)
    Abstract [en]

    A Monte Carlo simulation was used to study the outflow of O+ and H+ ions along three flight trajectories above the polar cap up to altitudes of about 15 RE. Barghouthi (2008) developed a model on the basis of altitude and velocity-dependent wave-particle interactions and a radial geomagnetic field which includes the effects of ambipolar electric field and gravitational and mirror forces. In the present work we improve this model to include the effect of the centrifugal force, with the use of relevant boundary conditions. In addition, the magnetic field and flight trajectories, namely, the central polar cap (CPC), nightside polar cap (NPC), and cusp, were calculated using the Tsyganenko T96 model. To simulate wave-particle interactions, the perpendicular velocity diffusion coefficients for O+ ions in each region were determined such that the simulation results fit the observations. For H+ ions, a constant perpendicular velocity diffusion coefficient was assumed for all altitudes in all regions as recommended by Nilsson et al. (2013). The effect of centrifugal acceleration was simulated by considering three values for the ionospheric electric field: 0 (no centrifugal acceleration), 50, and 100 mV/m. It was found that the centrifugal acceleration increases the parallel bulk velocity and decreases the parallel and perpendicular temperatures of both ion species at altitudes above about 4 RE. Centrifugal acceleration also increases the temperature anisotropy at high altitudes. At a given altitude, centrifugal acceleration decreases the density of H+ ions while it increases the density of O+ ions. This implies that with higher centrifugal acceleration more O+ ions overcome the potential barrier. It was also found that aside from two exceptions centrifugal acceleration has the same effect on the velocities of both ions. This implies that the centrifugal acceleration is universal for all particles. The parallel bulk velocities at a given value of ionospheric electric field were highest in the cusp followed by the CPC followed by the NPC. In this study a region of no wave-particle interaction was assumed in the CPC and NPC between 3.7 and 7.5 RE. In this region the perpendicular temperature was found to decrease with altitude due to perpendicular adiabatic cooling.

  • 2.
    Agües Paszkowsky, Núria
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab. Research Institutes of Sweden, Unit for Data Center Systems and Applied Data Science, Sweden.
    Brännvall, Rickard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab. Research Institutes of Sweden, Unit for Data Center Systems and Applied Data Science, Sweden.
    Carlstedt, Johan
    Research Institutes of Sweden, Unit for Data Center Systems and Applied Data Science, Sweden.
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Kovács, György
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Liwicki, Marcus
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Vegetation and Drought Trends in Sweden’s Mälardalen Region – Year-on-Year Comparison by Gaussian Process Regression2020In: 2020 Swedish Workshop on Data Science (SweDS), IEEE, 2020Conference paper (Refereed)
    Abstract [en]

    This article describes analytical work carried out in a pilot project for the Swedish Space Data Lab (SSDL), which focused on monitoring drought in the Mälardalen region in central Sweden. Normalized Difference Vegetation Index (NDVI) and the Moisture Stress Index (MSI) – commonly used to analyse drought – are estimated from Sentinel 2 satellite data and averaged over a selection of seven grassland areas of interest. To derive a complete time-series over a season that interpolates over days with missing data, we use Gaussian Process Regression, a technique from multivariate Bayesian analysis. The analysis show significant differences at 95% confidence for five out of seven areas when comparing the peak drought period in the dry year 2018 compared to the corresponding period in 2019. A cross-validation analysis indicates that the model parameter estimates are robust for temporal covariance structure (while inconclusive for the spatial dimensions). There were no signs of over-fitting when comparing in-sample and out-of-sample RMSE.

  • 3.
    Aires, Filipe
    et al.
    LERMA, Observatoire de Paris, Paris, France; Estellus, Paris, France.
    Prigent, Catherine
    LERMA, Observatoire de Paris, Paris, France; Estellus, Paris, France.
    Buehler, Stefan A.
    Universität Hamburg, Hamburg, Germany.
    Eriksson, Patrick
    Chalmers University of Technology, Gothenburg, Sweden.
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Crewell, Susanne
    Cologne University, Cologne, Germany.
    Towards more realistic hypotheses for the information content analysis of cloudy/precipitating situations – Application to a hyperspectral instrument in the microwave2019In: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 145, no 718, p. 1-14Article in journal (Refereed)
    Abstract [en]

    Information Content (IC) analysis can be used before an instrument is built to estimate its retrieval uncertainties and analyse their sensitivity to several factors. It is a very useful method to define/optimise satellite instruments. IC has shown its potential to compare instrument concepts in the infrared or the microwaves. IC is based on some hypotheses such as the the gaussian character of the Radiative Transfer (RT) and instrument errors, the first guess errors (Gaussian character, std and correlation structure), or the linearisation of the RT around a first guess. These hypotheses are easier to define for simple atmospheric situations. However, even in the clear‐sky case, their complexity has never ceased to increase towards more realism, to optimise the assimilation of satellite measurements in the Numerical Weather Prediction (NWP) systems. In the cloudy/precipitating case, these hypotheses are even more difficult to define in a realistic way as many factors are still very difficult to quantify. In this study, several tools are introduced to specify more realistic IC hypotheses than the current practice. We focus on the microwave observations as this is more pertinent for clouds and precipitation. Although not perfect, the proposed solutions are a new step towards more realistic IC assumptions of cloudy/precipitating scenes. A state‐dependence of the RT errors is introduced, the first guess errors have a more complex vertical structure, the IC is performed simultaneously on all the hydrometeors to take into account the contamination effect of the RT input uncertainties, and the IC is performed on a diversified set of cloudy/precipitating scenes with well‐defined hydrometeor assumptions. The method presented in this study is illustrated using the HYperspectral Microwave Sensor (HYMS) instrument concept with channels between 6.9 and 874 GHz (millimeter and sub‐millimeter regions). HYMS is considered as a potential next generation microwave sounder.

  • 4.
    Aires, Filipe
    et al.
    Estellus, Paris, France;LERMA, Observatoire de Paris, Paris, France;Water Center, Columbia University, New York, USA.
    Prigent, Catherine
    Estellus, Paris, France;LERMA, Observatoire de Paris, Paris, France.
    Orlandi, Emiliano
    Institute for Geophysics and Meteorology, University of Cologne, Cologne, Germany.
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Eriksson, Patrick
    Global Environmental Measurements and Modeling, Chalmers University of Technology, Gothenburg, Sweden.
    Crewell, Susanne
    Institute for Geophysics and Meteorology, University of Cologne, Cologne, Germany.
    Lin, Chung-Chi
    Earth Observation Projects Department, ESA, ESTEC, Noordwijk, Netherlands.
    Kangas, Ville
    Earth Observation Projects Department, ESA, ESTEC, Noordwijk, Netherlands.
    Microwave hyperspectral measurements for temperature and humidity atmospheric profiling from satellite: The clear-sky case2015In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 120, no 21, p. 11334-11351Article in journal (Refereed)
    Abstract [en]

    This study investigates the benefits of a satellite HYper-spectral Microwave Sensor (HYMS) for the retrieval of atmospheric temperature and humidity profiles, in the context of Numerical Weather Prediction (NWP). In the infrared, hyper-spectral instruments have already improved the accuracy of NWP forecasts. Microwave instruments so far only provide observations for a limited number of carefully selected channels. An information content analysis is conducted here to assess the impact of hyper-spectral microwave measurements on the retrieval of temperature and water vapor profiles under clear-sky conditions. It uses radiative transfer simulations over a large variety of atmospheric situations. It accounts for realistic observation (instrument and radiative transfer) noise and for a priori information assumptions compatible with NWP practices. The estimated retrieval performance of the HYMS instrument is compared to those of the microwave instruments to be deployed on board the future generation of European operational meteorological satellites (MetOp-SG). The results confirm the positive impact of a HYMS instrument on the atmospheric profiling capabilities compared to MetOp-SG. Temperature retrieval uncertainty, compared to a priori information, is reduced by 2 to 10%, depending on the atmospheric height, and improvement rates are much higher than what will be obtained with MetOp-SG. For humidity sounding these improvements can reach 30%, a significant benefit as compared to MetOp-SG results especially below 250 hPa. The results are not very sensitive to the instrument noise, under our assumptions. The main impact provided by the hyper-spectral information originates from the higher resolution in the O2 band around 60 GHz. The results are presented over ocean at nadir but similar conclusions are obtained for other incidence angles and over land.

  • 5.
    Akner, Malcolm
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Validating results from the Molten Salt Reactor Experiment by use of turbulent CFD simulations: A study of a modified U-tube shell-and-tube primary heat exchanger and radiator with molten salts2021Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Background

    Nuclear reactors utilizing molten fuels rather than solid fuels show a massive advantage in energy yield, waste handling and safety features. The only successful reactor utilizing a molten fuel was called the ‘Molten Salt Reactor Experiment’ (MSRE), built and operated in the Oak Ridge national laboratory (ORNL) in Tennessee, U.S.A. during the 1960s. The molten salts in question are fluoride compounds under the name of “FLiBe”. In this thesis, the heat exchangers of the MSRE are modelled and simulated, with the aim to test whether current computational fluid dynamics (CFD) software and mathematical models can accurately predict molten salt heat transfer behaviour. 

    Methods

    All programs used are open-source and/or free-access to facilitate open collaboration between researchers in this growing field. All models and findings produced in this thesis are free to use for future research.

    • The program Onshape was used to draw CAD-models based on hand-drawn technical documents released by ORNL.
    • Several programs, e.g., Simscale and Salome, were used to create high detailed meshes of the heat exchangers.
    • The CFD software Simscale and OpenFOAM have been used to simulate the heat exchangers, using the 𝑘 − 𝜔 𝑆𝑆𝑇 Reynolds averaged Navier-Stokes (RANS) turbulence model to perform a multiregion conjugate heat transfer (CHT) analysis.
    • The program Paraview has been used for all post-processing on the large datasets. 

    Results

    • A working toolchain with open-source programs for CFD has been identified.
    • Highly detailed, full-scale and accurate CAD-drawings of the two heat exchangers have been produced.
    • Models have been finely meshed, containing tens of millions of cells, with good quality measures.
    • The simulations produced physically sound and valuable data: 
      • Great heat transfer predictive capability with high accuracy to the data presented by ORNL.
      • Pressure data showed a consistent over-prediction with a factor of ~2. Possibility of error within the MSRE measurement. 

    Conclusions

    • CHT using modern turbulence methods work well for the intended purpose and can be used by industry to simulate molten salt heat transfer.
    • Open-source programs perform well and can be used by researchers to share ideas and progress.
    • Doubts around certain measurements from the MSRE, showing large uncertainties.
    • Future projects have been outlined to continue the work performed in this thesis.
    • Molten salt reactors show fantastic promise as an energy generation method and should be seriously considered for the future of clean, reliable energy.
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  • 6.
    Alho, Markku
    et al.
    Department of Electronics and Nanoengineering, School of Electrical Engineering, Aalto University, Aalto, Finland.
    Wedlund, Cyril Simon
    Department of Physics, University of Oslo, Oslo, Norway.
    Nilsson, Hans
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Swedish Institute of Space Physics, Kiruna, Sweden.
    Kallio, Esa
    Department of Electronics and Nanoengineering, School of Electrical Engineering, Aalto University, Aalto, Finland.
    Jarvinen, R.
    School of Electrical Engineering, Aalto University, Aalto, Finland. Finnish Meteorological Institute, Helsinki, Finland.
    Pulkkinen, T.I
    School of Electrical Engineering, Aalto University, Aalto, Finland. Department of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI,USA.
    Hybrid modeling of cometary plasma environments: II. Remote-sensing of a cometary bow shock2019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 630, article id A45Article in journal (Refereed)
    Abstract [en]

    Context. The ESA Rosetta probe has not seen direct evidence of a fully formed bow shock at comet 67P/Churyumov–Gerasimenko (67P). Ion spectrometer measurements of cometary pickup ions measured in the vicinity of the nucleus of 67P are available and may contain signatures of the large-scale plasma environment.

    Aims. The aim is to investigate the possibility of using pickup ion signatures to infer the existence or nonexistence of a bow shock-like structure and possibly other large-scale plasma environment features.

    Methods. A numerical plasma model in the hybrid plasma description was used to model the plasma environment of a comet. Simulated pickup ion spectra were generated for different interplanetary magnetic field conditions. The results were interpreted through test particle tracing in the hybrid simulation solutions.

    Results. Features of the observed pickup ion energy spectrum were reproduced, and the model was used to interpret the observation to be consistent with a shock-like structure. We identify (1) a spectral break related to the bow shock, (2) a mechanism for generating the spectral break, and (3) a dependency of the energy of the spectral break on the interplanetary magnetic field magnitude and bow shock standoff distance.

  • 7.
    Ali, Ahsan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Effect of temperature on early stage adhesion during TiAlN sliding against Inconel 718 and Stainless steel 316L: High temperature tribology2023Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    High-performance materials such as stainless steels and nickel based super alloys are widely used in demanding applications where high mechanical and thermal properties are required. The applications of super alloys are mainly found in jet engines, power plants and gas turbines demanding high fatigue strength, corrosion and oxidation resistance as well as wear resistant properties. In order to use them, they go through various machining processes such as milling, turning, cutting, polishing etc. until the final product is achieved. Modern manufacturing industries employs various machining tools and technologies to improve the machining process of heat resistant super alloys. However, there are still challenges which needs to be addressed. Among them, adhesive wear of the machining tools is one of the main wear mechanism during the tribological interaction of tool and workpiece, preventing them to achieve the desired quality and surface finish of the end product. Moreover, it damages the tool reducing its lifecycle and in return, increasing the production cost. Among the cutting tools tungsten carbide (WC/Co) tools coated with TiAlN coating due to their good high temperature performance are extensively used. Nonetheless, these coatings still face issue like adhesive wear, abrasion, oxidation at higher temperature damaging the tools and subsequent machining. Therefore, it is imperative to understand the initiation mechanism of adhesive wear during the tribological interaction of super alloys and coated cutting tool material.

    In this research work, the tribological response of two coatings deposited by physical vapour deposition (PVD), having the composition Ti60Al40N and Ti40Al60N have been studied against two super alloys material, i.e. Inconel 718 and stainless steel 316L. A high temperature SRV (Schwingung (Oscillating), Reibung (Friction), Verschleiß (Wear)) reciprocation friction and wear test set up was employed to investigate the friction behaviour, wear rate and dominant wear mechanisms. 

    For Ti60Al40N coating, the experimental results revealed that generally, friction increases in case of sliding against Inconel 718 up to 400 °C and drops at 760 °C. A high wear volume at room temperature and a decrease to a minimum at 760 °C has been observed for Inconel 718. On the other side, Stainless steel 316L (SS 316L) faces a continuous rise in friction coefficient with highest value at 760 °C during sliding against Ti60Al40N coating. Wear is highest at 400 °C for SS 316L pin. The worn surfaces shows that both workpiece materials experience increase in material transfer due to adhesive wear with rise in temperature. At 400 °C, adhesion is the primary wear mechanism for both workpiece materials. A further rise in temperature to 760 °C promotes the adhesive wear through oxides formation on both material surfaces. 

    Similarly, Ti40Al60N coating shows the same friction behaviour with change in average steady state friction values for both material of Inconel 718 and SS 316L. Both workpiece materials responds in a similar way to wear volume loss, i.e. lowest at room temperature and highest at 760 °C. For Inconel 718, transfer of coating constituents on to the Inconel 718 pin surface was detected and associated with coating rupture and peeling, exacerbating with rise in temperature. Adhesion, abrasion, and oxidation are primary wear mechanisms at 400 °C and 760 °C. For SS 316L, coating transfer only happen at 400 °C. No damage of coating at 40 °C, a complete damage at 400 °C, and formation of dense porous oxides layers at 760 °C have been noticed. At 400 °C, adhesion, abrasion, and chipping while at 760 °C, adhesion, three body abrasion, ploughing and oxidation are the main wear mechanisms.

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  • 8.
    Ali, Sheikh Nawaz
    et al.
    Birbal Sahni Institute of Palaeobotany, Lucknow.
    Shekhar, Mayank
    Birbal Sahni Institute of Palaeobotany, Lucknow.
    (Pandey, Pratima
    Indian Institute of Technology, Bombay.
    Bhardwaj, Anshuman
    Snow and Avalanche Study Establishment, Defence Research and Development Organization (DRDO), Him Parisar, Sector-37A, Chandigarh.
    Singh, Shaktiman
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Indian Himalayan capacity and adaptation programme: capacity-building in Himalayan glaciology2014In: Current Science, ISSN 0011-3891, Vol. 106, no 3, p. 346-Article in journal (Other academic)
  • 9.
    Alonso Rancurel, Belén
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Investigation of high temperature stability of additive manufactured austenitic stainless steels for space applications2023Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Additive manufacturing (AM) techniques are being studied for their application in the aerospace industry. Numerous benefits come from the already in shape final piece, which needs reduced amount of prime material for its production and can have its shape numerically optimized for weight reduction. Austenitic stainless steels (AuSS) are widely used in aerospace and their manufacturing through AM is a popular research topic in order to accelerate their effective incorporation in air-crafts and spaceships. The special microstructures of AM has been observed with characterization techniques. The present work studies the high temperature stability of three AuSS (316L, MOD-316 and 21-6-9) considering two approaches; surface corrosion and microstructure evolution.

    First, for high temperature corrosion, thermogravimetric analysis has been performed from 850°C to 1150°C. From the results, kinetic analysis were performed and the activation energy was extracted from Arrhenius fits. Two mechanism were found for alloy 316L (first 435.41 kJ/mol and second 593.24 kJ/mol) and MOD-316 (first 740.01 kJ/mol and second 495.58 kJ/mol). Further SEM observations on the scales have shown Ni diffusion through the chromia scale in MOD-316 alloy, which could explain the higher oxidation rates at 1150°C. Alloy 21-6-9 has the best passivation behaviour with an activation energy of 190.47 kJ/mol.

    Secondly, long heat treatment (HT) at 725°C in air atmosphere has been performed, for 24 and 240h. Samples were initially as-built or annealed (900°C for 1h), to compare the effect of the HT on the microstructure evolution and precipitates formation. LOM observation showed preferable nucleation in grain boundaries (GB), an increment of the number of precipitates and a growth towards elongated shapes following GB with increased time. It was also observed a reduction in precipitates number with the annealing HT for all the alloys. XRD, SEM and EDS analysis has been carried out to identify the structure and composition of the precipitates. Various chromium, tungsten, copper, molybdenum and niobium carbides and oxides have been found in MOD-316. Higher porosity is observed in 21-6-9, that presented mainly chromium oxides, carbides and nitrides in GB and surrounding the AM defects.

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  • 10.
    Anantha Raman, Deepa
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Thermal environment and design considerations of the Foresail-2 satellite mission2023Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The thermal design of small satellite missions is critical for ensuring the performance and longevity of onboard instruments. This thesis focuses on the thermal design of Foresail-2, a 6U CubeSat mission to Geostationary Transfer Orbit (GTO), specifically addressing the thermal challenges associated with the magnetometer located at the end of a long boom featured on the satellite.

    The objective of this research is to estimate the orbital loads, study its effects and develop an effective thermal control strategy to maintain the frame, boom and magnetometer temperature within an optimal operational range throughout the mission duration. A steady state thermal analysis is conducted to evaluate the effects of the GTO environment on the satellite structure under different operational scenarios and design conditions. To achieve the desired thermal control, several potential regulation strategies are investigated, including passive thermal coatings, insulation materials, and active cooling methods.

    Furthermore, thermal simulations are performed to predict the temperature profiles and gradients within the boom and magnetometer assembly, enabling the identification of potential hotspots or areas prone to thermal stress using ANSYS software package. These findings contribute to the implementation of thermal design modifications and the optimization of the configuration of the boom and magnetometer to enhance thermal performance.

    The results of this thesis contribute to the development of a robust thermal design for Foresail-2 mission satellite. Moreover, the methodologies and insights gained from this research can be extended to other CubeSat missions with similar thermal requirements and constraints.

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  • 11.
    Andersen, Torben
    et al.
    Lunds universitet.
    Enmark, Anita
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Integrated Modeling of Telescopes2011Book (Other academic)
  • 12.
    Andersen, Torben
    et al.
    Lund Observatory (Sweden) .
    Owner-Petersen, Mette
    Lund Observatory (Sweden) .
    Enmark, Anita
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Image-based wavefront sensing for astronomy using neural networks2020In: Journal of Astronomical Telescopes, Instruments, and Systems, ISSN 2329-4124, Vol. 6, no 3, article id 034002Article in journal (Refereed)
    Abstract [en]

    Motivated by the potential of non-diffraction limited, real-time computational image sharpening with neu7 ral networks in astronomical telescopes, we have studied wavefront sensing with convolutional neural networks basedon a pair of in-focus and out-of-focus point spread functions. By simulation, we generated a large dataset for trainingand validation of neural networks, and trained several networks to estimate Zernike polynomial approximations forthe incoming wavefront. We included the effect of noise, guide star magnitude, blurring by wide band imagining, andbit depth. We conclude that the “ResNet” works well for our purpose, with a wavefront RMS error of 130 nm forr0 = 0.3 m, guide star magnitudes 4–8, and inference time of 8 ms. It can also be applied for closed-loop operation inan adaptive optics system. We also studied the possible use of a Kalman filter or a recurrent neural network and foundthat they were not beneficial to performance of our wavefront sensor

  • 13.
    Andersson, Erik
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Numerical Approach to the Design and Optimisation of a Bi-Propellant Pintle Injector2022Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Rocket propulsion is of vital importance for space travel. New innovations are continuously developed in order to facilitate the demand of the rapidly evolving space sector. Recently a focus on reusable rockets has appeared due to the economical and environmental benefits they bring. When designing reusable launch vehicles the propellant injector becomes very important since it is a critical component when throttleabilty is desired. Which is a key element of landable rockets. Selecting an appropriate injector type therefore becomes crucial, a common injector type used for throttleable rockets is the pintle injector.

    Unfortunately the design process of the pintle injector is complicated due to the large amount of variables that must be determined. This thesis aims to solve this problem by developing a numerical method to design and optimise a pintle injector and then produce a preliminary design.

    The numerical method developed in this thesis is used to produce a preliminary design of a pintle injector designed to utilise a combination of liquid oxygen and gaseous methane, theoretically capable of a max thrust of 1000N and a throttleabilty of 5 to 1. The design had a focus on optimising the performance of the parameters sauter mean diameter, vaporisation distance and spray angle for the injector. The resulting injector showcases great performance and is deemed to show a successful preliminary design. Which shows that the numerical design and optimisation process that was developed also was successful.

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  • 14.
    Andersson, Erik
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Preliminary design of a small-scale liquid-propellant rocket engine testing platform2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Propulsion system testing before mission operation is a fundamental requirement in any project. For both industrial and commercial entities within the space industry, complete system integration into a static test platform for functional and performance testing is an integral step in the system development process. Such a platform - if designed to be relatively safe, uncomplicated and reliable - can be an important tool within academia as well, giving researchers and students a possibility for practical learning and propulsion technology research.

    In this thesis, a preliminary design for a liquid-propellant rocket engine testing platform to be used primarily for academical purposes is developed. Included in the presented design is a bi-propellant Chemical Propulsion system, gas pressure fed with Gaseous Nitrogen and using Gaseous Oxygen as oxidiser and a 70 % concentrated ethanol-water mixture as fuel. The propellant assembly contains all necessary components for operating the system and performing combustion tests with it, including various types of valves, tanks and sensors. An estimation of the total preliminary cost of selected components is presented as well. Also part of the developed platform design is a small thrust chamber made of copper, water-cooled and theoretically capable of delivering 1000 N of thrust using the selected propellants.

    A list of operations to be performed before, during and after a complete combustion test is presented at the end of the document, together with a preliminary design of a Digital Control and Instrumentation System software. Due to time limitations, the software could not be implemented in a development program nor tested with simulated parameters as part of this thesis project.

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  • 15.
    Anthony, Niklas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Emami, M. Reza
    University of Toronto, Canada.
    Cubesat Minimoon Rendezvous Mission Synthesis and Analysis2018In: IAC-18, International Astronautical Federation, 2018, article id IAC-18,A3,IP,65,x44584Conference paper (Refereed)
    Abstract [en]

    This paper introduces a mission concept for the remote characterization of a temporarily-captured asteroid, or “minimoon”, based on the utilization of the CubeSat form-factor. Minimoons are a subpopulation of the estimated two million Near-Earth Objects (NEOs) under 2 meters in diameter, which pass within the Moon’s orbit every year. These temporarily-captured objects do not remain in the Earth-Moon system for long, typically less than one year, and are thus a challenge for developing conventional spacecraft missions. A potential solution to this problem is to utilize the typical rapid-development timelines that CubeSat missions possess. This paper will analyze the requirements and limitations in developing a mission for a CubeSat to rendezvous or fly by a minimoon. This includes exploring the capabilities and applicability of the CubeSat technologies for such a mission, analyzing the erratic nature of minimoon orbits, lying out how such a mission project would be managed, and finally presenting a case study of such missions on the only known minimoon so far, Asteroid 2006 RH120.

  • 16.
    Arora, Aman
    et al.
    Department of Geography, Faculty of Natural Sciences, Jamia Millia Islamia, New Delhi 110025, India.
    Arabameri, Alireza
    Department of Geomorphology, Tarbiat Modares University, Jalal Ale Ahmad Highway, Tehran 9821, Iran.
    Pandey, Manish
    University Center for Research & Development (UCRD), Chandigarh University, Mohali 140413, Punjab, India. Department of Civil Engineering, Chandigarh University, Mohali 140413, Punjab, India.
    Siddiqui, Masood A.
    Department of Geography, Faculty of Natural Sciences, Jamia Millia Islamia, New Delhi 110025, India.
    Shukla, U.K.
    Center for Advanced Study in Geology, Institute of Science, Banaras Hindu University, Varanasi 221005, India.
    Tien Bui, Dieu
    Institute of Research and Development, Duy Tan University, Da Nang 550000, Viet Nam.
    Mishra, Varun Narayan
    Centre for Climate Change and Water Research, Suresh Gyan Vihar University, Jaipur 302017, Rajasthan, India.
    Bhardwaj, Anshuman
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. School of Geosciences, University of Aberdeen, Meston Building, King's College, Aberdeen AB24 3UE, UK.
    Optimization of state-of-the-art fuzzy-metaheuristic ANFIS-based machine learning models for flood susceptibility prediction mapping in the Middle Ganga Plain, India2021In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 750, article id 141565Article in journal (Refereed)
    Abstract [en]

    This study is an attempt to quantitatively test and compare novel advanced-machine learning algorithms in terms of their performance in achieving the goal of predicting flood susceptible areas in a low altitudinal range, sub-tropical floodplain environmental setting, like that prevailing in the Middle Ganga Plain (MGP), India. This part of the Ganga floodplain region, which under the influence of undergoing active tectonic regime related subsidence, is the hotbed of annual flood disaster. This makes the region one of the best natural laboratories to test the flood susceptibility models for establishing a universalization of such models in low relief highly flood prone areas. Based on highly sophisticated flood inventory archived for this region, and 12 flood conditioning factors viz. annual rainfall, soil type, stream density, distance from stream, distance from road, Topographic Wetness Index (TWI), altitude, slope aspect, slope, curvature, land use/land cover, and geomorphology, an advanced novel hybrid model Adaptive Neuro Fuzzy Inference System (ANFIS), and three metaheuristic models-based ensembles with ANFIS namely ANFIS-GA (Genetic Algorithm), ANFIS-DE (Differential Evolution), and ANFIS-PSO (Particle Swarm Optimization), have been applied for zonation of the flood susceptible areas. The flood inventory dataset, prepared by collected flood samples, were apportioned into 70:30 classes to prepare training and validation datasets. One independent validation method, the Area-Under Receiver Operating Characteristic (AUROC) Curve, and other 11 cut-off-dependent model evaluation metrices have helped to conclude that the ANIFS-GA has outperformed other three models with highest success rate AUC = 0.922 and prediction rate AUC = 0.924. The accuracy was also found to be highest for ANFIS-GA during training (0.886) & validation (0.883). Better performance of ANIFS-GA than the individual models as well as some ensemble models suggests and warrants further study in this topoclimatic environment using other classes of susceptibility models. This will further help establishing a benchmark model with capability of highest accuracy and sensitivity performance in the similar topographic and climatic setting taking assumption of the quality of input parameters as constant.

  • 17.
    Arridge, Christopher S.
    et al.
    Mullard Space Science Laboratory, Department of Space and Climate Physics.
    Agnor, Craig B.
    University of Manchester, School of Physics and Astronomy.
    André, Nicolas
    Centre d’Etude Spatiale des Rayonnements, Toulouse.
    Baines, Kevin H.
    NASA Jet Propulsion Laboratory, Pasadena.
    Fletcher, Leigh N.
    Gautier, Daniel
    LESIA, CNRS-Observatoire de Paris.
    Hofstadter, Mark D.
    NASA Jet Propulsion Laboratory, Pasadena.
    Jones, Geraint H.
    Mullard Space Science Laboratory, Department of Space and Climate Physics.
    Lamy, Laurent
    LESIA, CNRS-Observatoire de Paris.
    Langevin, Yves
    Institut d'Astrophysique Spatiale.
    Mousis, Olivier
    Institut UTINAM, CNRS, OSU THETA.
    Nettelmann, Nadine
    Universität Rostock.
    Russell, Christopher T.
    Institute of Geophysics and Meteorology, University of Cologne.
    Stallard, Tom
    Physics and Astronomy Department, Ohio University.
    Tiscareno, Matthew S.
    Cornell University, Ithaca.
    Tobie, Gabriel
    LPG, CNRS.
    Bacon, Andrew
    Systems Engineering and Asssessment Ltd., Bristol, UK.
    Chaloner, Chris
    Systems Engineering and Asssessment Ltd..
    Guest, Michael
    Systems Engineering and Asssessment Ltd..
    Kemble, Steve
    EADS, Astrium.
    Peacocke, Lisa
    EADS, Astrium.
    Achilleos, Nicholas
    Physics and Astronomy Department, Ohio University.
    Andert, Thomas P.
    Universität der Bundeswehr.
    Banfield, Don
    Cornell University, Ithaca.
    Barabash, Stas
    Swedish Institute of Space Physics.
    Martin-Torres, Javier
    Centre for Astrobiology, Madrid.
    Zarka, Philippe
    LESIA, CNRS-Observatoire de Paris.
    Uranus Pathfinder: Exploring the origins and evolution of Ice Giant planets2012In: Experimental astronomy, ISSN 0922-6435, E-ISSN 1572-9508, Vol. 33, no 2-3, p. 753-791Article in journal (Refereed)
    Abstract [en]

    The "Ice Giants" Uranus and Neptune are a different class of planet compared to Jupiter and Saturn. Studying these objects is important for furthering our understanding of the formation and evolution of the planets, and unravelling the fundamental physical and chemical processes in the Solar System. The importance of filling these gaps in our knowledge of the Solar System is particularly acute when trying to apply our understanding to the numerous planetary systems that have been discovered around other stars. The Uranus Pathfinder (UP) mission thus represents the quintessential aspects of the objectives of the European planetary community as expressed in ESA's Cosmic Vision 2015-2025. UP was proposed to the European Space Agency's M3 call for medium-class missions in 2010 and proposed to be the first orbiter of an Ice Giant planet. As the most accessible Ice Giant within the M-class mission envelope Uranus was identified as the mission target. Although not selected for this call the UP mission concept provides a baseline framework for the exploration of Uranus with existing low-cost platforms and underlines the need to develop power sources suitable for the outer Solar System. The UP science case is based around exploring the origins, evolution, and processes at work in Ice Giant planetary systems. Three broad themes were identified: (1) Uranus as an Ice Giant, (2) An Ice Giant planetary system, and (3) An asymmetric magnetosphere. Due to the long interplanetary transfer from Earth to Uranus a significant cruise-phase science theme was also developed. The UP mission concept calls for the use of a Mars Express/Rosetta-type platform to launch on a Soyuz-Fregat in 2021 and entering into an eccentric polar orbit around Uranus in the 2036-2037 timeframe. The science payload has a strong heritage in Europe and beyond and requires no significant technology developments. © 2011 Springer Science+Business Media B.V.

  • 18.
    Athauda, A M Bope Gedara Dharshana Ajith
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Motion Planning Scheme for Collision Free Autonomous Target Acquisition of Mobile Spacecraft Platform Using Reinforcement Learning2023Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Despite the promising results of reinforcement learning in autonomous maneuvers for ground-based applications, its potential for autonomous target acquisition and collision avoidance in space applications has yet to be thoroughly investigated. Therefore, this study attempts to develop a reinforcement learning-based resilient motion planning approach for autonomous target acquisition and collision avoidance, while focusing on the application where a fying robot is providing assistance to astronauts under microgravity conditions inside the International Space Station. Nevertheless, these complex motion planning strategies require comprehensive validations before deployment on real hardware. Therefore, the study is designed around a ground-based mobile spacecraft platform. The problem at hand has been further simplifed to a 3-Degree of Freedom problem as these types of experiments initially tested and validated in simulated microgravity laboratory environments located on earth. During this research, reinforcement learning agents have been trained to perform tasks, including a) target acquisition in obstacle-free environments, b) target acquisition while avoiding static obstacles, and c) target acquisition while avoiding dynamic obstacles. In all tasks, the trained agents efciently reach the target conditions while successfully avoiding collisions with obstacles.

  • 19.
    Atreya, Sushil
    et al.
    University of Michigan.
    Squyres, Steve
    Cornell University, Ithaca.
    Mahaffy, Paul
    Goddard Space Flight Center, Greenbelt, Maryland.
    Leshin, Laurie
    Rensselaer Polytechnic Institute, Troy, New York.
    Franz, Heather
    Goddard Space Flight Center, Greenbelt, Maryland.
    Trainer, Melissa
    Goddard Space Flight Center, Greenbelt, Maryland.
    Wong, Michael
    University of Michigan.
    McKay, Christopher
    NASA Ames Research Center, Moffett Field.
    Navarro-Gonzalez, Rafael
    Universidad Nacional Autónoma de México.
    Martin-Torres, Javier
    Centro de Astrobiología (CSIC-INTA), Madrid.
    MSL/SAM Measurements of Non Condensable Volatiles, Comparison with Viking Lander, and Implications for Seasonal Cycle2013Conference paper (Refereed)
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  • 20.
    Attree, Nicholas
    et al.
    Faculty of Natural Sciences, University of Stirling, UK.
    Kaufmann, Erika
    Faculty of Natural Sciences, University of Stirling, UK. Institute for Space Research Graz, Austrian Academy of Sciences, Austria.
    Hagermann, Axel
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Faculty of Natural Sciences, University of Stirling, UK.
    Gas flow in Martian spider formation2021In: Icarus, ISSN 0019-1035, E-ISSN 1090-2643, Vol. 359, article id 114355Article in journal (Refereed)
    Abstract [en]

    Martian araneiform terrain, located in the Southern polar regions, consists of features with central pits and radial troughs which are thought to be associated with the solid state greenhouse effect under a CO2 ice sheet. Sublimation at the base of this ice leads to gas buildup, fracturing of the ice and the flow of gas and entrained regolith out of vents and onto the surface. There are two possible pathways for the gas: through the gap between the ice slab and the underlying regolith, as proposed by Kieffer (2007), or through the pores of a permeable regolith layer, which would imply that regolith properties can control the spacing between adjacent spiders, as suggested by Hao et al. (2019). We test this hypothesis quantitatively in order to place constraints on the regolith properties. Based on previously estimated flow rates and thermophysical arguments, we suggest that there is insufficient depth of porous regolith to support the full gas flow through the regolith. By contrast, free gas flow through a regolith–ice gap is capable of supplying the likely flow rates for gap sizes on the order of a centimetre. This size of gap can be opened in the centre of a spider feature by gas pressure bending the overlying ice slab upwards, or by levitating it entirely as suggested in the original Kieffer (2007) model. Our calculations therefore support at least some of the gas flowing through a gap opened between the regolith and ice. Regolith properties most likely still play a role in the evolution of spider morphology, by regolith cohesion controlling the erosion of the central pit and troughs, for example.

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  • 21.
    Auenmüller, Christoph
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Automated Controller Design for a Missile Using Convex Optimization2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The focus of the present master thesis is the automation of an existing controllerdesign for a missile using two aerodynamic actuating systems. The motivation isto evaluate more missile concepts in a shorter period of time.The option used is trimming and linearization of a highly nonlinear missile at specic conditions. According to these conditions, either a two-dimensional operatingpoint grid dened by Mach number and height or three-dimensional operatingpoint grid dened by Mach number, height and angle of attack is generated forthe whole operating range of the missile. The controllers are designed at thesepoints using convex optimization. The convex set denes the pole placement areawhich is constrained by linear matrix inequalities according to the dynamic behaviorof the missile at the operating point conditions. These controllers describea validity area where the missile can be stabilized. This area consists all neighboringoperating points and denes therefore the grid density which can dier atspecic regions of the operating range. Controlling the missile to the target makesit necessary to apply gain-scheduling in order to get the manipulated variable byinterpolation of adjacent operating points. During this blending of the controllersa problem called windup can occur when an actuator is saturated. This mightlead to instability in worst case but can be counteracted by a model-recovery antiwindupnetwork which guarantees stability in the presence of saturation. Thisanti-windup design is automated by an ane linear parameter dependency of thegrid parameters and has the same validity area like the controllers.The whole design was successfully developed and tested in MATLAB/Simulink onmissiles using one or two aerodynamic actuating systems. The controllers have agood performance at small and high acceleration steps and the anti-windup keepsthe missile stable even though the actuators are saturated. Stability and robustnessof the controllers and anti-windup networks was veried as well as an airdefense maneuver where the missile starts at the ground and intercepts a targetat high altitude was successfully simulated for dierent grids and missiles.

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  • 22.
    Avasak, Kalyani
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Institute of Space Systems, University of Stuttgart.
    Mission Analysis and Trajectory optimisation for project CAPE2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Atmospheric reentry is a challenging part of human space ight and planetary entry missions.At the Institute of Space Systems in University of Stuttgart the idea of projectCAPE was conceived in 2012. Project Cubesat Atmospheric Probe for Education aimsto demonstrate the capability of miniaturised technologies of the micro electric plasmathruster, reentry vehicle design and ablative shielding material developed in this institute.The mission scenario is such that the CAPE is being deployed from the InternationalSpace Station and needs to complete the de-orbit of the Service and deorbit module andre-entry of the Atmospheric entry module in less than 1 year. The Cube satellite weighs3.0 kg consisting of a 2+1 unit service design module with solar panels, pulsed plasmapropulsion system of the university of Stuttgart (PETRUS) and a micro atmosphericreentry module (MIRKA-2). This reentry vehicle is unique in its size and weighs 0.5kg. During its reentry phase, it will be subjected to the intense aero-thermal loads at theThermal Protection System front which are absorbed by its ablative heat shield. But thecharacteristics of the re-entry trajectory like the ight path angle, entry velocity and entrypoint greatly determine the survivability against the integral heat load for this ballisticreentry vehicle. Although the success of the mission is considerably higher when having acontrolled reentry, in case of ballistic vehicles it is solely determined by the mission design.The main task is to investigate and develop the optimal re-entry trajectories in thedesign-time phase of mission development for MIRKA-2 vehicle that satises the objectiveof minimizing heat loads and adhering to operational constraints. Thus, the aimof this thesis is to provide a novel solution and optimum trajectory of the de-orbit andre-entry ight to maximize the survivability of the reentry module. The con icting parametersin this mission would be the operational limit of the pulsed plasma thruster andminimum heat loads during reentry ight. The simulation of these trajectories is carriedout in MATLAB using the REENT software developed in the Institute of Space Systems,University of Stuttgart. Its source code is composed in Fortran 77 which is integratedinto MATLAB. A careful mission analysis with the constraints of the capacity of pulsedplasma thruster, impulse provided by the separation mechanism and survivability of thereentry vehicle is carried out to prove the feasibility of this mission. In order to accomplishthe survivability during re-entry the aspects that have been modelled are the ight dynamicsof the satellite, aerodynamic and aero-thermal loads, spacecraft behaviour underthe external loads and local heating process.

  • 23.
    Awad, Mahmoud E.
    et al.
    Department of Geology, Faculty of Science, Al-Azhar University, Nasr City, 11884 Cairo, Egypt. Department of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy, University of Granada, 18071 Granada, Spain. Instituto Andaluz de Ciencias de la Tierra, CSIC-UGR, Av. de las Palmeras 4, 18100 Armilla, Granada, Spain.
    Borrego-Sánchez, Ana
    Department of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy, University of Granada, 18071 Granada, Spain. Instituto Andaluz de Ciencias de la Tierra, CSIC-UGR, Av. de las Palmeras 4, 18100 Armilla, Granada, Spain.
    Escamilla-Roa, Elizabeth
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Instituto Andaluz de Ciencias de la Tierra, CSIC-UGR, Av. de las Palmeras 4, 18100 Armilla, Granada, Spain.
    Hernández-Laguna, Alfonso
    Instituto Andaluz de Ciencias de la Tierra, CSIC-UGR, Av. de las Palmeras 4, 18100 Armilla, Granada, Spain.
    Sainz-Díaz, C. Ignacio
    Instituto Andaluz de Ciencias de la Tierra, CSIC-UGR, Av. de las Palmeras 4, 18100 Armilla, Granada, Spain.
    Modeling of the adsorption of a protein-fragment on kaolinite with potential antiviral activity2020In: Applied Clay Science, ISSN 0169-1317, E-ISSN 1872-9053, Vol. 199, article id 105865Article in journal (Refereed)
    Abstract [en]

    This work aimed at studying the potentiality of interactions between kaolinite surfaces and a protein-fragment (350–370 amino acid units) extracted from the glycoprotein E1 in the transmembrane domain (TMD) of hepatitis C virus capsid. A computational work was performed for locating the potential electrostatic interaction sites between kaolinite aluminol and siloxane surfaces and the residues of this protein-fragment ligand, monitoring the possible conformational changes. This hydrated neutralized kaolinite/protein-fragment system was simulated by means of molecular modeling based on atomistic force fields based on empirical interatomic potentials and molecular dynamic (MD) simulations. The MD calculations indicated that the studied protein-fragment interacted with the kaolinite surfaces with an exothermic process and structural distortions were observed, particularly with the hydrophilic aluminol surface by favorable adsorption energy. The viral units isolation or trapping by the adsorption on the kaolinite nanoparticles producing structural distortion of the peptide ligands could lead to the blockage of the entry on the receptor and hence a lack of viral activity would be produced. Therefore, these findings with the proposed insights could be an useful information for the next experimental and development studies in the area of discovering inhibitors of the global challenged hepatitis and other pathogenic viruses based on the phyllosilicate surface activity. These MD studies can be extended to other viruses like the COVID-19 interacting with silicate minerals surfaces.

  • 24.
    Axelsson, Katarina
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Studies of auroral processes using optical methods2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The Aurora is a visual manifestation of the complex plasma processes that occur as the solar wind interacts with the Earth’s magnetosphere and ionosphere. Therefore, studies of the aurora can lead to better understanding of the near-Earth space environment and of fundamental physical processes.This thesis focuses on optical studies of the aurora, both ground-based observations using the Auroral Large Imaging System (ALIS) and measurements from instruments onboard the Japanese micro-satellite Reimei. Various properties of the aurora are studied, such as the characteristic energy of precipitating electrons and scale sizes of diffuse auroral structures. Our understanding of the ionospheric physical processes involved in a particular auroral emission is improved using conjugate particle and optical data.Auroral light is a result of radiative transitions between excited states of the ionospheric gases. These excited states are formed either by direct electron impact or by a series of more complicated processes, involving chemical reactions, where part of the energy is converted into auroral light. Studies of auroral emissions can therefore give information about primary particle fluxes, ionospheric composition, and the magnetospheric and ionospheric processes leading to auroral precipitation. One way of deducing the characteristic energy of the precipitating particles is by using intensity ratios of auroral emissions. To be reliable, this method requires a good understanding of the processes involved in the auroral emissions used. The method works well if the measurements are made along the geomagnetic field lines. Using data from ALIS, both in magnetic zenith and off magnetic zenith, this method is tested for angles further away from the direction of the magnetic field lines. The result shows that it is possible to use this technique to deduce the characteristic energy for angles up to 35 degrees away from magnetic zenith.Using ALIS we have also been able to study structures and variations in diffuse aurora. When mapped to the magnetosphere, this provides information about the characteristics of the modulating wave activity in the magnetospheric source region. A statistical study of the scale sizes of diffuse auroral structures was made and the result shows widths and separation between structures of the order of 13-14 km. When mapped to the magnetosphere, this corresponds to 3-4 ion gyro radii for protons with a typical energy of 7 keV. Magnetometer data show that the structures move southward with a speed close to zero in the plasma convection frame. Stationary mirror mode structures in the magnetospheric equatorial plane are a likely explanation for these diffuse auroral structures. In another study we use measured precipitating electron energy spectra to improve our understanding of how the auroral process itself relates to the 427.8 nm auroral emission, which is often used when studying intensity ratios between different emission lines. The 427.8 nm emission is a fairly simple emission to model, with only a few processes involved, but still has some uncertainties, mostly due to the excitation cross section. Simultaneous measurements of the intensity of this emission from ALIS and the intensity and electron flux from Reimei provide a way to evaluate different sets of cross sections in order to find the best fit to the experimental data. It also allows a comparison of the absolute calibration of ALIS and Reimei imagers, improving the possibility to use the space-borne data for other detailed quantitative studies.In order to compare absolute measurements of aurora using different imagers, optical instruments are usually absolute calibrated by exposing them to a calibration light source. In 2011 an intercalibration workshop was held in Sodankylä, Finland, where nine low light sources were compared to the radioactive Fritz Peak reference source. The results were compared with earlier calibration workshop results and show that the sources are fairly stable. Two sources were also calibrated with the calibration standard source at UNIS, Svalbard, and the results show agreement with the calibration workshop in Sodankylä within 15 to 25%. This confirms the quality of the measurements with ALIS and in turn also of the the Reimei imagers.

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  • 25.
    Axelsson, Katarina
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Sergienko, T.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Nilsson, H.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Brändström, U.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Asamura, K.
    Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara.
    Sakanoi, Takeshi
    Tohoku University, Graduate School of Science, Sendai, Japan.
    First negative system of N2 + in aurora: Simultaneous space-borne and ground-based measurements and modeling results2014In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 32, no 5, p. 499-506Article in journal (Refereed)
    Abstract [en]

    The auroral emission of the first negative system of N2 + at 427.8 nm is analyzed using simultaneous measurements from the ground with ALIS (Auroral Large Imaging System) and from space with optical (MAC) and particle (ESA) instruments of the Reimei satellite. The study has two main objectives. The first is validation of the absolute calibration of the ALIS and the Reimei MAC cameras. The other task is to evaluate different cross sections of the electron excitation of N2 + that are used for the modeling of the auroral 1N system emissions. The simultaneous measurements of the 427.8 nm emission by ALIS and Reimei imagers show excellent agreement, indicating that the calibration of the two instruments is correct. Comparison of the 427.8 nm emission intensity calculated using the incident electron flux measured by the Reimei particle instruments with intensities measured by the optical imagers show that the best match is reached with the cross section from Shemansky and Liu (2005).

  • 26.
    Axelsson, Katarina
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Sergienko, T.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Nilsson, H.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Brändström, U.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Ebihara, Y.
    Research Institute for Sustainable Humanosphere, Kyoto University.
    Asamura, K.
    Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara.
    Hirahara, M.
    Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo.
    Spatial characteristics of wave-like structures in diffuse aurora obtained using optical observations2012In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 30, no 12, p. 1693-1701Article in journal (Refereed)
    Abstract [en]

    We present the results of a statistical study using optical images from ALIS (Auroral Large Imaging System) to investigate the spatial and temporal variations of structures in diffuse aurora. Analysis of conjugate Reimei data shows that such fine structures are a result of modulation of high-energy precipitating electrons. Pitch angle diffusion into the loss cone due to interaction of whistler mode waves with plasma sheet electrons is the most feasible mechanism leading to high-energy electron precipitation. This suggests that the fine structure is an indication of modulations of the efficiency of the wave-particle interaction. The scale sizes and variations of these structures, mapped to the magnetosphere, can give us information about the characteristics of the modulating wave activity. We found the scale size of the auroral stripes and the spacing between them to be on average 13-14 km, which corresponds to 3-4 ion gyro radii for protons with an energy of 7 keV. The structures move southward with a speed close to zero in the plasma convection frame.

  • 27.
    Axelsson, Katarina
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Sergienko, T.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Sandahl, Ingrid
    Brändström, U.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    A study on the possibility to deduce the 2D distribution of the auroral electron precipitation from multi wavelength optical measurements with auroral imagers2011In: Óptica Pura y Aplicada, ISSN 0030-3917, E-ISSN 2171-8814, Vol. 44, no 4, p. 605-609Article in journal (Refereed)
    Abstract [en]

    The intensity ratios of auroral emissions at different wavelengths are widely used for reconstruction of auroral electron parameters. This method works quite well if the measurements of the auroral emissions are conducted in the magnetic zenith direction. In this study we want to investigate the possibility to use the intensity ratio method in the case where the observations are made in a direction not parallel to the magnetic field. In particular, we want to check the possibility of using auroral data for deducing the 2D distribution of the auroral electron precipitation. We use ALIS multi-station measurements of the auroral red and green line emissions (6300 Å and 5577 Å) to get data in zenith and non-zenith directions. We also take into account that the red line emission peak and the green line emission peak are at different altitudes. The results of this investigation show we can obtain reliable results for angles up to 35º away from magnetic zenith.

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  • 28.
    Ayala Fernández, Lucía
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Impact of Collision Avoidance Manoeuvres on Large Satellite Constellations2020Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 29.
    Azari, Pouyan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    An Orbit Control System for UWE-4 Using the High Fidelity Simulation Tool Orekit2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Cubesats are picosatellites that have a mass of less than 1.3kg and have a shape of acube. As a result of their low cost of development and launch, cubesats are gainingpopularity in industry and academia. These satellites are also a cost-efective way forspace technology demonstrations. University of Würzburg has a longstanding cubesatprogram started with the launch of UWE-1 in 2005. This was followed by UWE-2 andUWE-3. Several technologies were tested and validated using the UWE platform. Thelast mission UWE-3 has successfully tested an attitude control system.In the next mission, UWE-4 will demonstrate an orbit control system.

    Being a picosatellite as small as this one (10 x 10 x 10cm 3 and 1kg) brings new challenges intodi↵erent aspects of satellite design, development, control and operation. The orbit con-trol of such a satellite is one of the problems that should be tackled. Being such a smallsatellite means having less propellant mass and much smaller thrusters than conventionalsatellites. These should be addressed in the orbit control.

    UWE-4 will take advantage of four NanoFEEP thrusters, on one side. Because of theiraccuracy and functionality, these thrusters can be used to implement a continuous thrustsystem. They are also a good choice because of their low energy usage. This work startswith the preparation that was needed to implement a control system. Then explains thestate of the art for continuous thrust control systems. Implements two di↵erent methods,based on perfect control and discusses the outcome. It discuses the limiting factors, likefuel mass, available electrical energy and their e↵ect on the controller performance andconcludes with recommendation for the future researches.

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  • 30.
    Azua-Bustos, Armando
    et al.
    Centro de Astrobiología (CSIC-INTA), Madrid, Spain. Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile.
    González-Silva, Carlos
    Facultad de Ciencias, Universidad de Tarapacá, Arica, Chile.
    Fernández-Martínez, Miguel Ángel
    Centro de Astrobiología (CSIC-INTA), Madrid, Spain.
    Arenas-Fajardo, Cristián
    Atacama Biotech, Santiago, Chile.
    Fonseca, Ricardo
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Instituto Andaluz de Ciencias de la Tierra (UGR-CSIC), Armilla, Granada, Spain.
    Fernández-Sampedro, Maite
    Centro de Astrobiología (CSIC-INTA), Madrid, Spain.
    Fairén, Alberto G.
    Centro de Astrobiología (CSIC-INTA), Madrid, Spain. Department of Astronomy, Cornell University, Ithaca, NY, USA.
    Zorzano Mier, María-Paz
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Aeolian transport of viable microbial life across the Atacama Desert, Chile: Implications for Mars2019In: Scientific Reports, E-ISSN 2045-2322, Vol. 9, article id 11024Article in journal (Refereed)
    Abstract [en]

    Here we inspect whether microbial life may disperse using dust transported by wind in the Atacama Desert in northern Chile, a well-known Mars analog model. By setting a simple experiment across the hyperarid core of the Atacama we found that a number of viable bacteria and fungi are in fact able to traverse the driest and most UV irradiated desert on Earth unscathed using wind-transported dust, particularly in the later afternoon hours. This finding suggests that microbial life on Mars, extant or past, may have similarly benefited from aeolian transport to move across the planet and find suitable habitats to thrive and evolve.

  • 31. Barabash, Victoria
    A comparison of PMSE occurrence with energetic particle precipitation detected by riometer in northern Scandinavia2000In: Proceedings of the 9th International Workshop on Technical and Scientific Aspects of MST Radar- MST9 combined with COST-76 Final Profiler Workshop: Toulouse, France, March 13-18, 2000 / [ed] Belva Edwards, Toulouse: SCOSTEP , 2000Conference paper (Other academic)
  • 32. Barabash, Victoria
    Are variations in PMSE intensity affected by energetic particle precipitation?2002In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 20, p. 539-545Article in journal (Refereed)
  • 33. Barabash, Victoria
    ESRAD MST radar analysis of the waves1998In: Proceedings of the 4th European Symposium on Stratospheric Ozone, Air Pollution Research Report 66, European Commision, 1998, p. 70-73Conference paper (Other academic)
  • 34. Barabash, Victoria
    Leewave observations by the MST radar ESRAD in northen Sweden1999In: Mesoscale processes in the stratosphere: their effect on the stratospheric chemistry and microphysics ; proceedings of the European workshop 8 to 11 November 1998 Bad Tölz, Bavaria, Germany / [ed] K.S. Carslaw ; G.T. Amanatidis, Luxemourg: European Commission Joint Research Centre, 1999, p. 233-238Conference paper (Other academic)
  • 35. Barabash, Victoria
    MST radar observations of PMSE in Northern Scandinavia during May-August 19971998In: Proceedings of the Eigth Workshop on Technical and Scientific Aspects of MST Radar : solar-terrestrial energy program: solar-terrestrial energy program ; Bangalore, India, December 15 - 20, 1997 / [ed] Belva Edwards, Boulder, Colo.: SCOSTEP , 1998, p. 326-329Conference paper (Other academic)
  • 36. Barabash, Victoria
    MST-radar lee wave ovservations during winter 1996/97 in northern Scandinavia1997In: Proceedings of 13th ESA Symposium on Rocket and Baloon Programmes and Related Research, ESA-SP-397, 1997, p. 179-183Conference paper (Other academic)
  • 37. Barabash, Victoria
    Wind profiling with ESRAD, the Esrange radar1997In: Extended abstracts COST-76 Profiler Workshop / [ed] Hans Richner, Zürich: Eidgenössische Technische Hochschule (ETH), Institute for Atmospheric Science , 1997, p. 70-73Conference paper (Other academic)
  • 38. Barabash, Victoria
    et al.
    Chilson, P.
    Kirkwood, S.
    Réchou, A.
    Stebel, K.
    Investigations of the possible relationship between PMSE and tides using a VHF MST radar1998In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 25, no 17, p. 3297-3300Article in journal (Refereed)
  • 39.
    Barabash, Victoria
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Ejemalm, Johnny
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Kuhn, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Molin, Sven
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Johansson, Jonny
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Westerberg, Lars-Göran
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Masters Programs in Space Science and Engineering in Northern Sweden2017Conference paper (Refereed)
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  • 40. Barabash, Victoria
    et al.
    Kirkwood, S.
    Feofilov, A.
    Kutepov, A.
    Polar mesosphere summer echoes during the July 2000 solar proton event2004In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 22, no 3, p. 759-771Article in journal (Refereed)
    Abstract [en]

    The influence of the solar proton event (SPE) 14-16 July 2000 on Polar Mesosphere Summer Echoes (PMSE) is examined. PMSE were observed by the Esrange VHF MST Radar (ESRAD) at 67°53'N, 21°06'E. The 30MHz Imaging Riometer for Ionospheric Studies IRIS in Kilpisjärvi (69°30'N, 20°47'E) registered cosmic radio noise absorption caused by ionisation changes in response to the energetic particle precipitation. An energy deposition/ion-chemical model was used to estimate the density of free electrons and ions in the upper atmosphere. Particle collision frequencies were calculated from the MSISE-90 model. Electric fields were calculated using conductivities from the model and measured magnetic disturbances. The electric field reached a maximum of 91mV/m during the most intensive period of the geomagnetic storm accompanying the SPE. The temperature increase due to Joule and particle heating was calculated, taking into account radiative cooling. The temperature increase at PMSE heights was found to be very small. The observed PMSE were rather intensive and extended over the 80-90km height interval. PMSE almost disappeared above 86km at the time of greatest Joule heating on 15 July 2000. Neither ionisation changes, nor Joule/particle heating can explain the PMSE reduction. Transport effects due to the strong electric field are a more likely explanation.

  • 41.
    Barabash, Victoria
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Kuhn, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Ejemalm, Johnny
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Enmark, Anita
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    de Oliviera, Élcio Jeronimo
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Persson, Olle
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Sadeghi, Soheil
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    The influence of international student projects on learning and study environment among the national and international space students2020In: NU2020 — Hållbart lärande: Abstractbok, Sveriges universitets- och högskoleförbund (SUHF) , 2020, p. 74-75Conference paper (Refereed)
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  • 42.
    Barabash, Victoria
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Osepian, A.
    Polar Geophysical Institute, Halturina 15, 183 023 Murmansk, Russia.
    Dalin, P.
    Swedish Institute of Space Physics, Rymdcampus 1, 981 92 Kiruna, Sweden.
    Kirkwood, S.
    Swedish Institute of Space Physics, Rymdcampus 1, 981 92 Kiruna, Sweden.
    Electron density profiles in the quiet lower ionosphere based on the results of modeling and experimental data2012In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 30, no 9, p. 1345-1360Article in journal (Refereed)
    Abstract [en]

    The theoretical PGI (Polar Geophysical Institute) model for the quiet lower ionosphere has been applied for computing the ionization rate and electron density profiles in the summer and winter D-region at solar zenith angles less than 80° and larger than 99° under steady state conditions. In order to minimize possible errors in estimation of ionization rates provided by solar electromagnetic radiation and to obtain the most exact values of electron density, each wavelength range of the solar spectrum has been divided into several intervals and the relations between the solar radiation intensity at these wavelengths and the solar activity index F10.7 have been incorporated into the model. Influence of minor neutral species (NO, H2O, O, O3) concentrations on the electron number density at different altitudes of the sunlit quiet D-region has been examined. The results demonstrate that at altitudes above 70 km, the modeled electron density is most sensitive to variations of nitric oxide concentration. Changes of water vapor concentration in the whole altitude range of the mesosphere influence the electron density only in the narrow height interval 73–85 km. The effect of the change of atomic oxygen and ozone concentration is the least significant and takes place only below 70 km. 

    Model responses to changes of the solar zenith angle, solar activity (low–high) and season (summer–winter) have been considered. Modeled electron density profiles have been evaluated by comparison with experimental profiles available from the rocket measurements for the same conditions. It is demonstrated that the theoretical model for the quiet lower ionosphere is quite effective in describing variations in ionization rate, electron number density and effective recombination coefficient as functions of solar zenith angle, solar activity and season. The model may be used for solving inverse tasks, in particular, for estimations of nitric oxide concentration in the mesosphere.

  • 43.
    Barabash, Victoria
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Osepian, Aleftina
    Polar Geophysical Institute, Murmansk.
    Dalin, Peter
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Influence of water vapour on the height distribution of positive ions, effective recombination coefficient and ionisation balance in the quiet lower ionosphere2014In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 32, p. 207-222Article in journal (Refereed)
    Abstract [en]

    Mesospheric water vapour concentration effects on the ion composition and electron density in the lower ionosphere under quiet geophysical conditions were examined. Water vapour is an important compound in the mesosphere and the lower thermosphere that affects ion composition due to hydrogen radical production and consequently modifies the electron number density. Recent lower-ionosphere investigations have primarily concentrated on the geomagnetic disturbance periods. Meanwhile, studies on the electron density under quiet conditions are quite rare. The goal of this study is to contribute to a better understanding of the ionospheric parameter responses to water vapour variability in the quiet lower ionosphere. By applying a numerical D region ion chemistry model, we evaluated efficiencies for the channels forming hydrated cluster ions from the NO+ and O2+ primary ions (i.e. NO+.H2O and O2+.H2O, respectively), and the channel forming H+(H2O)nproton hydrates from water clusters at different altitudes using profiles with low and high water vapour concentrations. Profiles for positive ions, effective recombination coefficients and electrons were modelled for three particular cases using electron density measurements obtained during rocket campaigns. It was found that the water vapour concentration variations in the mesosphere affect the position of both the Cl2+ proton hydrate layer upper border, comprising the NO+(H2O)nand O2+(H2O)nhydrated cluster ions, and the Cl1+ hydrate cluster layer lower border, comprising the H+(H2O)npure proton hydrates, as well as the numerical cluster densities. The water variations caused large changes in the effective recombination coefficient and electron density between altitudes of 75 and 87 km. However, the effective recombination coefficient, αeff, and electron number density did not respond even to large water vapour concentration variations occurring at other altitudes in the mesosphere. We determined the water vapour concentration upper limit at altitudes between 75 and 87 km, beyond which the water vapour concentration ceases to influence the numerical densities of Cl2+ and Cl1+, the effective recombination coefficient and the electron number density in the summer ionosphere. This water vapour concentration limit corresponds to values found in the H2O-1 profile that was observed in the summer mesosphere by the Upper Atmosphere Research Satellite (UARS). The electron density modelled using the H2O-1 profile agreed well with the electron density measured in the summer ionosphere when the measured profiles did not have sharp gradients. For sharp gradients in electron and positive ion number densities, a water profile that can reproduce the characteristic behaviour of the ionospheric parameters should have an inhomogeneous height distribution of water vapour.

  • 44.
    Barghouthi, Imad A.
    et al.
    Space Research Lab, Department of Physics, Al-Quds University, Jerusalem, Department of Physics, Al-Quds University, Jerusalem.
    Abudayyeh, H.A.
    Department of Physics, Al-Quds University, Jerusalem.
    Slapak, Rikard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Nilsson, Hans
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    O+ and H+ above the polar cap: Observations and semikinetic simulations2016In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, no 1, p. 459-474Article in journal (Refereed)
    Abstract [en]

    A 1-dimensional direct simulation Monte Carlo model is used to study the outflow of O+ and H+ ions from 1.2 RE to 15.2 RE along two flight trajectories originating from the polar cap, namely the central polar cap (CPC) and the cusp. To study the effect of varying geophysical conditions and to deduce the proper set of parameters. several parameters were varied and the results were compared to corresponding data from Cluster spacecraft. First, several sets of diffusion coefficients were considered based on using diffusion coefficients calculated by Barghouthi et al. [1998], Nilsson et al. [2013], and Abudayyeh et al. [2015b] for different altitude intervals. It was found that in the central polar cap using the diffusion coefficients reported by Barghouthi et al. [1998] for altitudes lower than 3.7 RE, zero diffusion coefficients between 3.7 and 7.5 RE and diffusion coefficients from Nilsson et al. [2013] for altitudes higher than 7.5 RE provide the best fit for O+ ions. For O+ ions in the cusp the best fit was obtained for using Barghouthi et al. [1998] diffusion coefficients for altitudes lower than 3.7 RE and Nilsson et al. [2013] diffusion coefficients for altitudes higher than that. The best fit for H+ ions in both regions was obtained by using the diffusion coefficients calculated by Abudayyeh et al. [2015b]. Also, it was found that along an ion's trajectory the most recent heating dominates. Second, the strength of centrifugal acceleration was varied by using three values for the ionospheric electric field namely: 0, 50, and 100 mV/m. It was found that the value of 50 mV/m provided the best fit for both ion species in both regions. Finally the lower altitude boundary conditions and the electron temperature were varied. Increasing the electron temperature and the lower altitude O+ parallel velocity were found to increase the access of O+ ions to higher altitudes and therefore increase the density at a given altitude. The variation of all other boundary conditions only affected the densities of the ions and not the other moments due to the overwhelming effect of wave particle interaction. Furthermore varying the parameters of one ion species has no effect on the other ion species. We also compared the energy gain per ion due to wave particle interaction, centrifugal acceleration, and ambipolar electric field and found that wave particle interaction is the most important mechanism, while ambipolar electric field is relatively unimportant especially at higher altitudes.

  • 45.
    Baron, P.
    et al.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Urban, J.
    Chalmers University of Technology.
    Sagawa, H.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Möller, J.
    Chalmers University of Technology.
    Mendrok, Jana
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Dupuy, E.
    Sato, T.O,
    Ochiai, Satoshi
    National Institute of Information and Communication Technology, Tokyo.
    Suzuk, K.
    Manabe, T.
    Osaka Prefecture University, Naka, Sakai.
    Nishibori, T.
    Japan Aerospace Exploration Agency (JAXA), Tsukuba.
    Kikuchi, K.
    Sato, R.
    Takayanagi, M.
    Murayama, Y.
    Shiotani, M.
    Research Institute for Sustainable Humanosphere, Kyoto University.
    Kasai, Y.
    The Level 2 research product algorithms for the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES)2011In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 4, p. 2105-2124Article in journal (Refereed)
    Abstract [en]

    This paper describes the algorithms of the level-2 research (L2r) processing chain developed for the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES). The chain has been developed in parallel to the operational chain for conducting researches on calibration and retrieval algorithms. L2r chain products are available to the scientific community. The objective of version 2 is the retrieval of the vertical distribution of trace gases in the altitude range of 18–90 km. A theoretical error analysis is conducted to estimate the retrieval feasibility of key parameters of the processing: line-of-sight elevation tangent altitudes (or angles), temperature and ozone profiles. While pointing information is often retrieved from molecular oxygen lines, there is no oxygen line in the SMILES spectra, so the strong ozone line at 625.371 GHz has been chosen. The pointing parameters and the ozone profiles are retrieved from the line wings which are measured with high signal to noise ratio, whereas the temperature profile is retrieved from the optically thick line center. The main systematic component of the retrieval error was found to be the neglect of the non-linearity of the radiometric gain in the calibration procedure. This causes a temperature retrieval error of 5–10 K. Because of these large temperature errors, it is not possible to construct a reliable hydrostatic pressure profile. However, as a consequence of the retrieval of pointing parameters, pressure induced errors are significantly reduced if the retrieved trace gas profiles are represented on pressure levels instead of geometric altitude levels. Further, various setups of trace gas retrievals have been tested. The error analysis for the retrieved HOCl profile demonstrates that best results for inverting weak lines can be obtained by using narrow spectral windows.

  • 46.
    Baron, P.
    et al.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Urban, J.
    Chalmers University of Technology.
    Sagawa, H.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Möller, J.
    Chalmers University of Technology.
    Murtagh, D.P.
    Chalmers University of Technology.
    Mendrok, Jana
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Dupuy, E.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Sato, T.O.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Ochiai, S.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Suzuki, K.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Manabe, T.
    Osaka Prefecture University, Naka, Sakai.
    Nishibori, T.
    Japan Aerospace Exploration Agency (JAXA), Tsukuba.
    Kikuchi, K.
    Japan Aerospace Exploration Agency (JAXA), Tsukuba.
    Sato, R.
    Japan Aerospace Exploration Agency (JAXA), Tsukuba.
    Takayanagi, M.
    Japan Aerospace Exploration Agency (JAXA), Tsukuba.
    Murayama, Y.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Shiotani, M.
    Research Institute for Sustainable Humanosphere, Kyoto University.
    Kasai, Y.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    The level 2 research product algorithms for the superconducting submillimeter-wave limb-emission sounder (SMILES)2011In: Atmospheric Measurement Techniques Discussions, E-ISSN 1867-8610, Vol. 4, no 3, p. 3593-3645Article in journal (Refereed)
    Abstract [en]

    This paper describes the algorithms of the level-2 research (L2r) processingchain developed for the Superconducting Submillimeter-Wave Limb-EmissionSounder (SMILES). The chain has been developed in parallel to the operationalchain for conducting researches on calibration and retrieval algorithms. L2rchain products are available to the scientific community. The objective ofversion 2 is the retrieval of the vertical distribution of trace gases in thealtitude range of 18-90 km. An theoretical error analysis is conducted toestimate the retrieval feasibility of key parameters of the processing:line-of-sight elevation tangent altitudes (or angles), temperature and O3 profiles. The line-of-sight tangent altitudes are retrievedbetween 20 and 50 km from the strong ozone (O3) line at 625.371 GHz,with low correlation with the O3 volume-mixing ratio and temperatureretrieved profiles. Neglecting the non-linearity of the radiometric gain inthe calibration procedure is the main systematic error. It is large for theretrieved temperature (between 5-10 K). Therefore, atmospheric pressure cannot be derived from the retrieved temperature, and, then, in the altituderange where the line-of-sight tangent altitudes are retrieved, the retrievedtrace gases profiles are found to be better represented on pressure levelsthan on altitude levels. The error analysis for the retrieved HOCl profiledemonstrates that best results for inverting weak lines can be obtained byusing narrow spectral windows. Future versions of the L2r algorithms willimprove the temperature/pressure retrievals and also provide information inthe upper tropospheric/lower stratospheric region (e.g., water vapor, icecontent, O3) and on stratospheric and mesospheric line-of-sight winds.

  • 47.
    Barquin Murguia, Alberto Isaac
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering. Airbus DS.
    SmallSat Payload Simulation for Onboard-Software Verification2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This work presents the advancements in the development of simulation models of spacecraft components as part of a testbench for verification of onboard flight software. The satellite and its mission are briefly described as to give an idea of the conditions where the simulation has to run. The simulation environment, SimTG, is also introduced and a description of the developed models is presented. The models required interaction between different simulation environments, real hardware and simulated hardware, and also some data processing was necessary in order to filter undesired information. Finally, the performance of the models was tested and verified and a sensible improvement of the state of the testbench on the simulation side was achieved, although a considerable amount of work still lies ahead before a complete onboard software verification tool is ready.

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  • 48.
    Baskar, Ajith Kumar
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Evaluation Methodology Of Lubricants For Space Exploration Robotics2020Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
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  • 49.
    Bazzocchi, Michael C. F.
    et al.
    University of Toronto, Institute for Aerospace Studies.
    Emami, Reza
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. University of Toronto.
    Asteroid detumbling for redirection missions2018In: 2018 IEEE Aerospace Conference, IEEE Computer Society, 2018Conference paper (Refereed)
    Abstract [en]

    In order to accomplish most asteroid redirection missions, rotational control of the asteroid body is required. Small near-Earth asteroids tend to exhibit a significant range of rotational and tumbling properties. This work provides an analysis of asteroid detumbling using a formation of spacecraft. Through an orbiter and three landed thruster spacecraft, a low-thrust detumbling maneuver is performed on two illustrative asteroids. The asteroid scenarios are designed such that they reflect the characteristics of possible redirection scenarios. In particular the geometries, densities, angular velocities, and masses of the asteroids are adjusted according to available asteroid data to provide two unique redirection scenarios. The asteroid and spacecraft specifications are outlined, as well as the formulations for the detumbling maneuver. The results of the maneuver are discussed along with the key detumbling parameters and timeframe required.

  • 50.
    Bazzocchi, Michael C. F.
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Emami, Reza
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. University of Toronto, Canada, 4925 Dufferin St., Toronto M3H 5T6.
    Concurrent Redirection and Attitude Control of an Asteroid2019In: 2019 IEEE Aerospace Conference, IEEE, 2019Conference paper (Refereed)
    Abstract [en]

    This paper demonstrates the applicability of two low-thrust spacecraft for the task of concurrently redirecting an asteroid and controlling its attitude. Through the use of available observational data, a synthetic near-Earth asteroid, with suitable characteristics for a resource utilization mission, is designed. The asteroid is given an initial orientation and angular velocity, such that it is in a tumbling state. The two spacecraft are attached to the asteroid surface, and employ low-thrust ion thrusters for the attitude control and redirection of the asteroid. The spacecraft first detumble the asteroid body using their torque-inducing thrusters, and then re-orient the asteroid such that the redirection thrusters are aligned with the redirection thrust vector. The spacecraft then ensure the asteroid's orientation is aligned with the redirection thrust vector throughout the entire trajectory transfer maneuver, while ensuring the angular velocity remains bounded around zero. The trajectory design is a low-thrust maneuver, based on Gauss' variational equations, which redirects the asteroid from its orbit about the Sun to rendezvous with Earth. A linear control law is employed for both the detumbling and redirection maneuver with attitude control. The overall performance of the system and the applicability of the approach are discussed.

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