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• 201.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), 18100 Granada, Spain.
High-Resolution Dynamical Downscaling of Re-Analysis Data over the Kerguelen Islands using the WRF Model2019In: Journal of Theoretical and Applied Climatology, ISSN 0177-798X, E-ISSN 1434-4483, Vol. 135, no 3-4, p. 1259-1277Article in journal (Refereed)

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

• 202.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
MARSWRF Prediction of Entry Descent Landing Profiles: Applications to Mars Exploration2019In: Earth and Space Science, E-ISSN 2333-5084, Vol. 6, no 8, p. 1440-1459Article in journal (Refereed)

In this paper we use the Mars implementation of the Planet Weather Research and Forecasting model, MarsWRF, to simulate the Entry, Descent and Landing (EDL) vertical profiles from six past missions: Pathfinder, Mars Exploration Rovers Opportunity and SpiritPhoenix, Mars Science Laboratory Curiosity rover and ExoMars 2016 (Schiaparelli), and compare the results with observed data. In order to investigate the sensitivity of the model predictions to the atmospheric dust distribution, MarsWRF is run with two prescribed dust scenarios. It is concluded that the MarsWRF EDL predictions can be used for guidance into the design and planning stage of future missions to the planet, as it generally captures the observed EDL profiles, although it has a tendency to underestimate the temperature and overestimate the density for heights above 15 km. This could be attributed to an incorrect representation of the observed dust loading. We have used the model to predict the EDL conditions that may be encountered by two future missions: ExoMars 2020 and Mars 2020. When run for Oxia Planum and Jezero Crater for the expected landing time, MarsWRF predicts a large sensitivity to the dust loading in particular for the horizontal wind speed above 10‐15 km with maximum differences of up to ±30 m s‐1 for the former and ±15 m s‐1 for the latter site. For both sites, the best time for EDL, i.e. when the wind speed is generally the weakest with smaller shifts in direction, is predicted to be in the late morning and early afternoon.

• 203.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Centro de Astrobiología (INTA-CSIC), Madrid, Spain. Centro de Astrobiología (INTA-CSIC), Madrid, Spain. Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de Chile, Santiago, Chile. Facultad de Ciencias, Universidad de Tarapacá, Iquique, Chile. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Instituto Andaluz de Ciencias de la Tierra (UGR-CSIC), Granada, Spain.
A surface temperature and moisture intercomparison study of the Weather Research and Forecasting model, in‐situ measurements and satellite observations over the Atacama Desert2019In: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 145, no 722, p. 2202-2220Article in journal (Refereed)

Good knowledge of the environmental conditions of deserts on Earth is relevant forclimate studies. The Atacama Desert is of particular interest as it is considered tobe the driest region on Earth. We have performed simulations using the WeatherResearch and Forecasting (WRF) model over the Atacama Desert for two week-longperiods in the austral winter season coincident with surface temperature and relativehumidity in-situ observations at three sites. We found that the WRF model generallyoverestimates the daytime surface temperature, with biases of up to 11◦C, despitegiving a good simulation of the relative humidity. In order to improve the agree-ment with observed measurements, we conducted sensitivity experiments in whichthe surface albedo, soil moisture content and five tuneable parameters in the NoahLand Surface Model (namely soil porosity, soil suction, saturated soil hydraulic con-ductivity, thebparameter used in hydraulic functions and the quartz fraction) areperturbed. We concluded that an accurate simulation is not possible, most likelybecause the Noah Land Surface Model does not have a groundwater table that maybe shallow in desert regions. The WRF-predicted land surface temperature is alsoevaluated against that estimated from the Moderate Resolution Imaging Spectrora-diometer (MODIS) instrument. While at night the satellite-derived and ground-basedmeasurements are generally in agreement, during the day MODIS estimates aretypically lower by as much as 17◦C. This is attributed to the large uncertainty inthe MODIS-estimated land surface temperatures in arid and semi-arid regions. Thefindings of this work highlight the need for ground-based observational networksin remote regions such as the Atacama Desert where satellite-derived and modelproducts may not be very accurate.

• 204.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Centro de Astrobiología (INTA-CSIC). Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR).
Planetary Boundary Layer and Circulation Dynamics at Gale Crater, Mars2018In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 302, p. 537-559Article in journal (Refereed)

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

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

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

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

• 205.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Providing Air Traffic Control Services for Small Unmanned Aircraft Through LTE2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
• 206.
Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland.
Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland. Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland. Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge. Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland. Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge. Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland. Laboratoire de Génie des Procédés et les Matériaux, Ecole Centrale Paris. Laboratoire Atmosphères, Milieux, Observations Spatiales, Univ. Pierre et Marie Curie, Univ. Versailles Saint-Quentin & CNRS, Paris. Jacobs Technology, NASA Johnson Space Center. Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland. Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor. Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland. Laboratoire Atmosphères, Milieux, Observations Spatiales, Univ. Pierre et Marie Curie, Univ. Versailles Saint-Quentin & CNRS, Paris. Laboratoire Interuniversitaire des Systèmes Atmosphériques, Université Paris-Est Créteil, Univ. Paris Diderot and CNRS. Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland. Exobiology Branch, NASA Ames Research Center, Moffett Field, Kalifornien. Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland. Department of Astronomy, Cornell University, Ithaca, New York. Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor. Division of Geological and Planetary Sciences, California Institute of Technology. Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland. Earth Sciences Department, Utrecht University. Department of Earth and Environmental Science and School of Science, Rensselaer Polytechnic Institute, Troy, New York. Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Centro de Astrobiologia, INTA-CSIC, Madrid.
Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars2015In: Journal of Geophysical Research - Planets, ISSN 2169-9097, E-ISSN 2169-9100, Vol. 120, no 3, p. 495-514Article in journal (Refereed)

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

• 207.
National Astronomy and Ionosphere Center, Arecibo Observatory.
National Astronomy and Ionosphere Center, Arecibo Observatory. National Astronomy and Ionosphere Center, Arecibo Observatory. Manufacturing and Mechanical Engineering Department, Miami University. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. University of Puerto Rico, Department of Chemistry.
Potassium Doppler-resonance lidar for the study of the mesosphere and lower thermosphere at the Arecibo Observatory2003In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 65, no 16-18, p. 1411-1424Article in journal (Refereed)

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

• 208.
NASA Goddard Space Flight Center, Greenbelt, MD, USA.
Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI, USA. University of Maryland, College Park, MD, USA. NASA Goddard Space Flight Center, Greenbelt, MD, USA. Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI, USA. Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC, USA. LATMOS, CNRS, Sorbonne Université, UVSQ, Paris, France. NASA Goddard Space Flight Center, Greenbelt, MD, USA. NASA Goddard Space Flight Center, Greenbelt, MD, USA. College of Arts and Sciences, Misericordia University, Dallas, PA, USA. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Instituto Andaluz de Ciencias de la Tierra (CSIC‐UGR), Granada, Spain. Lunar and Planetary Institute, Universities Space Research Association, Houston, TX, USA. Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI, USA. NASA Ames Research Center, Moffett Field, CA, USA. Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Ciudad de México, Mexico. Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI, USA. NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Centro de Astrobiología (INTA‐CSIC), Torrejón de Ardoz, Madrid, Spain.
Seasonal Variations in Atmospheric Composition as Measured in Gale Crater, Mars2019In: Journal of Geophysical Research - Planets, ISSN 2169-9097, E-ISSN 2169-9100, Vol. 124, no 11, p. 3000-3024Article in journal (Refereed)

The Sample Analysis at Mars (SAM) instrument onboard the Mars Science Laboratory Curiosity rover measures the chemical composition of major atmospheric species (CO2, N240Ar, O2, and CO) through a dedicated atmospheric inlet. We report here measurements of volume mixing ratios in Gale Crater using the SAM quadrupole mass spectrometer, obtained over a period of nearly 5 years (3 Mars years) from landing. The observation period spans the northern summer of MY 31 and solar longitude (LS) of 175° through spring of MY 34, LS = 12°. This work expands upon prior reports of the mixing ratios measured by SAM QMS in the first 105 sols of the mission. The SAM QMS atmospheric measurements were taken periodically, with a cumulative coverage of four or five experiments per season on Mars. Major observations include the seasonal cycle of CO2, N2, and Ar, which lags approximately 20–40° of LS behind the pressure cycle driven by CO2 condensation and sublimation from the winter poles. This seasonal cycle indicates that transport occurs on faster timescales than mixing. The mixing ratio of O2 shows significant seasonal and interannual variability, suggesting an unknown atmospheric or surface process at work. The O2 measurements are compared to several parameters, including dust optical depth and trace CH4 measurements by Curiosity. We derive annual mean volume mixing ratios for the atmosphere in Gale Crater: CO2 = 0.951 (±0.003), N2 = 0.0259 (±0.0006), 40Ar = 0.0194 (±0.0004), O2 = 1.61 (±0.09) x 103, and CO = 5.8 (±0.8) x 104.

• 209.
Centro de Astrobiología (CSIC-INTA), Madrid, Spain.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Centro de Astrobiología (CSIC-INTA), Madrid, Spain. Centro de Astrobiología (CSIC-INTA), Madrid, Spain.
Defects on a pyrite(100) surface produce chemical evolution of glycine under inert conditions: experimental and theoretical approaches2019In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, no 44, p. 24535-24542Article in journal (Refereed)

The presence of non-stoichiometric sites on the pyrite(100) surface makes it a suitable substrate for driving the chemical evolution of the amino acid glycine over time, even under inert conditions. Spectroscopic molecular fingerprints prove a transition process from a zwitterionic species to an anionic species over time on the monosulfide enriched surface. By combining experimental and theoretical approaches, we propose a surface mechanism where the interaction between the amino acid species and the surface will be driven by the quenching of the surface states at Fe sites and favoured by sulfur vacancies. This study demonstrates the potential capability of pyrite to act as a surface catalyst.

• 210.
Department of Automation, Shanghai Jiaotong University.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Department of Automation, Shanghai Jiaotong University.
Enhanced NEH method in solving permutation flow shop problem2007In: Shanghai Jiaotong University. Journal, ISSN 1007-1172, Vol. 12E, no 1, p. 47-52Article in journal (Refereed)

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

• 211.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Development of a Class D motor amplifier for a next-generation mechanism control electronics2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

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

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

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

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

• 212.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
UKF-SLAM Implementation for the Optical Navigation System of a Lunar Lander2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
• 213.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Autonomous Navigation System for High Altitude Balloons2019Doctoral thesis, comprehensive summary (Other academic)
• 214.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Balloon design for Mars, Venus, and Titan atmospheres2019In: Applied Sciences: APPS, ISSN 1454-5101, E-ISSN 1454-5101Article in journal (Refereed)

This paper studies the specications of balloons for the exploration of bodies with dierentatmospheric conditions. The development of a simulation tool is described, which is usedfor analyzing the behaviour of balloons on Mars, Venus, and Titan. The software is veriedthrough comparison of its output with recorded data from a set of ights at Esrange SpaceCenter. Based on the simulation results, recommendations are made for dierent balloonexploration missions.

• 215.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Wind Based Navigation for Zero-Pressure Stratospheric Balloons Using Reinforcement learning2019In: Acta Astronomica, ISSN 0001-5237Article in journal (Refereed)

The horizontal motion of the balloon is governed by the winds at the float altitude. In order to navigate, and change the direction of balloon flight, knowledge of the wind environment around the balloon is needed. The real time navigation and control of zero-pressure balloons is a challenging task as there are no sensors that can be used onboard the balloon to provide real knowledge of the wind environment. Further, their is no active actuation possible and the resources available for passive actuation are limited. These constraints makes the balloon flight difficult and inflexible. In this paper, a solution to this problem of balloon navigation, and its path planning is presented by using data from ECMWF in combination with reinforcement learning. Data from ECMWF gives an overview of almost real-time environment and a reinforcement learning algorithm help in optimizing the passive actuation resources.

• 216.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. kanika.garg@ltu.se .
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Aerobot design for planetary explorations2016In: AIAA Space and Astronautics Forum and Exposition, SPACE 2016, American Institute of Aeronautics and Astronautics, 2016Conference paper (Refereed)

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

• 217.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Balloon Ascent Prediction: Comparative Study of Analytical, Fuzzy and Regression Models2019In: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 64, no 1, p. 252-270Article in journal (Refereed)

The ascent prediction of high-altitude zero-pressure stratospheric balloons is an important aspect of targeted test flight. Prediction of the balloon ascent rate is the prerequisite for many of the flights as it helps in planning ballasting and valving manoeuvres. In this paper, a standard analytical model, a fuzzy model and a statistical regression model are developed and compared to predict the zero-pressure balloon ascent. The flight data is extracted from the Esrange balloon service system for zero-pressure balloons with different payload capability, and several potential explanatory variables are computed for every sampled climbed segment. For the fuzzy modelling approach, a fuzzy c-mean clustering algorithm is used for system identification and prediction. For the regression approach, a Gaussian process regression is used, and principal component analysis is applied for finding the significant inputs. The result shows that the data driven approaches are more efficient than the standard analytical model.

• 218.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Fuzzy Modelling of Zero-pressure Balloon Ascent2018In: 2018 Modeling and Simulation Technologies Conference, 2018Conference paper (Refereed)

Zero-pressure balloon ascent prediction is a critical issue for Swedish Space Corporation(SSC) as targeted test ights are important part of SSC activities. This paper introducesa data-driven approach for estimating the balloon ascent. An output-constrained fuzzylogic approach is applied to the zero-pressure balloon data set from the past 10 years fromEsrange Space Center and rules are formulated that can express the balloon ascent. Theserules are veried by performing a root mean square analysis of estimated ascent againstthe real ascent trajectory. The result shows that the proposed fuzzy model is reliable andis able to estimate the balloon ascent with an acceptable accuracy.

• 219.
Meteorologisches Institut, Ludwig-Maximilians-Universität.
Meteorologisches Institut, Ludwig-Maximilians-Universität. Meteorologisches Institut, Ludwig-Maximilians-Universität. Meteorologisches Institut, Ludwig-Maximilians-Universität. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Representative wavelengths absorption parameterization applied to satellite channels and spectral bands2014In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 148, p. 99-115Article in journal (Refereed)

• 220.
Universität Hamburg, Freie Universität Berlin.
Space Science Institute, Boulder, Colorado. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
In Situ Compositional Measurements of Rocks and Soils with the Alpha Particle X-ray Spectrometer on NASA's Mars Rovers2015In: Elements, ISSN 1811-5209, E-ISSN 1811-5217, Vol. 11, no 1, p. 39-44Article in journal (Refereed)

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

• 221.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Searching for Exoplanets in K2 Data2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

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

• 222.
Institute for Aerospace Studies, University of Toronto.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
A robust approach to robot team learning2016In: Autonomous Robots, ISSN 0929-5593, E-ISSN 1573-7527, Vol. 40, no 8, p. 1441-1457Article in journal (Refereed)

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

• 223.
Institute for Aerospace Studies, University of Toronto.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Concurrent Markov decision processes for robot team learning2015In: Engineering applications of artificial intelligence, ISSN 0952-1976, E-ISSN 1873-6769, Vol. 39, p. 223-234, article id 12Article in journal (Refereed)

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

• 224.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Optical Analysis of Plasma: Flame Emission in Cryogenic Rocket Engines2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

This thesis contains the results of optical flame emission measurements of the Vulcain 2.1engine and the plasma emission spectroscopy of the Lumen Project engine. The plume spectroscopyis analyzed, ordered and studied in detail to offer the best possible molecular composition.The main focus relied on the hydroxide radical, blue radiation and other moleculesanalysis of the intensities encountered during the tests. The plasma emission spectroscopy isfocused on the determination of the plasma temperature value in LIBS measurements. Thehydrogen plasma temperature determination of the local thermodynamic equilibrium, followedby the carbon and sequentially oxygen plasma is obtained. The quality of the LTE isto be determined to judge the truthworthness of the determined temperatures. Both the testsare analyzed thanks to the use of spectrographs, cameras and dedicated software for opticalapplications. The results related to the Vulcain 2.1 LOX/LH2 engine showed the evolutionof the plume in different ROF or pressure variations. Furthermore, the results of the LumenProject LOX/methane engine led to the determination of the plasma temperatures and a firstestimation of the LTE quality.

• 225.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Atmospheric Turbulence Study Utilizing a Five-Hole Probe on an Unmanned Aerial Vehicle (UAV)2020Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
• 226.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Department of Physics, University of Helsinki.
Department of Physics and Astronomy, University of Western Ontario.
Identification of meteorite source regions in the solar system2018In: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 311, p. 271-287Article in journal (Refereed)

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

• 227.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. ONERA.
Optimizing the architecture of the Salammbô-EnKF data assimilation tool for radiation belt modeling2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
• 228.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Development of a Star Camera Algorithm for Calculating thePosition on Earth and Mars (VaMEx DLR)2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

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

• 229.
California Institute of Technology, Pasadena, Division of Geological and Planetary Sciences, California Institute of Technology.
Indiana University, Jet Propulsion Laboratory, California Institute of Technology, Pasadena. Jet Propulsion Laboratory, California Institute of Technology, Pasadena. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Curiosity's Mission of Exploration at Gale Crater, Mars2015In: Elements, ISSN 1811-5209, E-ISSN 1811-5217, Vol. 11, no 1, p. 19-26Article in journal (Refereed)

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

• 230.
Technische Universität München.
The Pennsylvania State University. University of Colorado, Boulder. George Washington University. California Institute of Technology. School of Aerospace, Transport and Manufacturing, Cranfield University. Neptec Design Group, Atlas Building (R27), Harwell Campus Didcot, Fermi Avenue, Oxfordshire. Electrical and Electronics Faculty, Istanbul Technical University, Maslak. Thales Alenia Space Cannes, 5 Allée des Gabians, Cannes. Institute of Space Systems, University of Stuttgart. Universität Stuttgart. Institute of Space Systems, University of Stuttgart. Technical University Berlin. Universidad Simón Bolívar, Sartenejas, Caracas. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Massachusetts Institute of Technology.
Next - Exploration universal station (NEXUS)2016In: Proceedings of the International Astronautical Congress, IAC, 2016Conference paper (Refereed)

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

• 231.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Investigation of progressive damage mechanisms in aerospace grade composites2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
• 232.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Development of an FPGA based Trigger for Slow Moving Events for the EUSO-TA Telescope2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
• 233.
Cloud Physics and Severe Weather Research Section, Environment Canada.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. NOAA, NESDIS, Madison, WI. CIMSS, University of Wisconsin-Madison, Madison, WI. NOAA, NESDIS, Greenbelt, MD. NCAR, Boulder, Colorado. Cloud Physics and Severe Weather Research Section, Environment Canada. I.M. Systems Group, NOAA/NWS/NCEP, Camp Springs, MD. Radiometrics Corporation, CIRES, University of Colorado, Boulder, CO. I.M. Systems Group, NOAA/NWS/NCEP, Camp Springs, MD. RPN, CMC, Environment Canada. Leading Edge Atmospherics, Boulder, CO.
Ice fog in arctic during fram-ice fog project aviation and nowcasting applications2014In: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 95, no 2, p. 211-226Article in journal (Refereed)

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

• 234.
Cloud Physics and Severe Weather Research Section, Environment Canada.
I.M. Systems Group, NOAA/NWS/NCEP, Camp Springs, MD. RPN, CMC, Environment Canada. Meteorolooieches lnstitut, University of Bonn. Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing. National Center for Atmospheric Research, Boulder, Colorado. I.M. Systems Group, NOAA/NWS/NCEP, Camp Springs, MD. Radiometrics Corporation, CIRES, University of Colorado, Boulder, CO. NOAA, NESDIS, Madison, WI. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. NOAA, NESDIS, Greenbelt, MD. Cloud Physics and Severe Weather Research Section, Environment Canada. Ruhr-Universität Bochum, Department of Geography.
A review on ice fog measurements and modeling2015In: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895, Vol. 151, p. 2-19Article in journal (Refereed)

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

• 235.
NASA Goddard Spaceflight Center,Greenbelt, MD, USA.
Space Science Institute, College Station, TX, USA. Department of Earth and Space Science and Engineering, York University, Toronto, Ontario, Canada. College of Engineering, University of Michigan, Ann Arbor, MI, USA. College of Engineering, University of Michigan, Ann Arbor, MI, USA. Aeolis Research, Pasadena, CA, USA. Department of Earth and Planetary Science, The Johns Hopkins University, Baltimore, MD, USA. Department of Earth and Space Science and Engineering, York University, Toronto, Ontario, Canada. Department of Earth and Space Science and Engineering, York University, Toronto, Ontario, Canada. Centro de Astrobiología (INTA-CSIC), Madrid, Spain. Finnish Meteorological Institute, Helsinki, Finland. Southwest Research Institute, Boulder, CO, USA. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Instituto Andaluz de Ciencias de la Tierra (CSIC‐UGR), Armilla, Granada, Spain. Department of Astronomy, University of Maryland, College Park, MD, USA. Department of Earth and Space Science and Engineering, York University, Toronto, Ontario, Canada. Finnish Meteorological Institute, , Helsinki, Finland; School of Electrical Engineering, Aalto University, , Espoo, Finland. NASA Goddard Spaceflight Center, Greenbelt, MD, USA;CRESST II and Department of Astronomy, University of Maryland, College Park, MD, USA. Aeolis Research, Pasadena, CA, USA. NASA Goddard Spaceflight Center, Greenbelt, MD, USA. Cornell Center for Astrophysics and Planetary Science, Cornell University, Ithaca, NY, USA. Cornell Center for Astrophysics and Planetary Science, Cornell University, Ithaca, NY, USA. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA. Centro de Astrobiología (INTA-CSIC), Madrid, Spain. Leidos, Houston, TX, USA. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Mars Science Laboratory Observations of the 2018/Mars Year 34 Global Dust Storm2019In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 46, no 1, p. 71-79Article in journal (Refereed)

Mars Science Laboratory Curiosity rover observations of the 2018/Mars year 34 global/planet‐encircling dust storm represent the first in situ measurements of a global dust storm with dedicated meteorological sensors since the Viking Landers. The Mars Science Laboratory team planned and executed a science campaign lasting approximately 100 Martian sols to study the storm involving an enhanced cadence of environmental monitoring using the rover's meteorological sensors, cameras, and spectrometers. Mast Camera 880‐nm optical depth reached 8.5, and Rover Environmental Monitoring Station measurements indicated a 97% reduction in incident total ultraviolet solar radiation at the surface, 30K reduction in diurnal range of air temperature, and an increase in the semidiurnal pressure tide amplitude to 40 Pa. No active dust‐lifting sites were detected within Gale Crater, and global and local atmospheric dynamics were drastically altered during the storm. This work presents an overview of the mission's storm observations and initial results.

• 236.
Universities Space Research Association/NASA Goddard Space Flight Center.
Ashima Research Inc. Jet Propulsion Laboratory, California Institute of Technology, Pasadena. Texas A&M University, College Station, TX. Texas A&M University, College Station, TX. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Earth and Space Science and Engineering , York University. Earth and Space Science and Engineering , York University. Earth and Space Science and Engineering , York University. Uni-versity of Michigan, Ann Arbor. NASA Goddard Space Flight Center, Greenbelt.
The Mars Science Laboratory dust storm campaign2017Conference paper (Other academic)
• 237.
NASA Goddard Spaceflight Center, Greenbelt, MD.
Aeolis Research, Pasadena, CA. NASA Goddard Spaceflight Center, Greenbelt, MD. Department of Earth and Space Science and Engineering, York University, Toronto, ON, Canada. Department of Earth and Space Science and Engineering, York University, Toronto, ON, Canada. Department of Earth and Space Science and Engineering, York University, Toronto, ON, Canada. Aeolis Research, Pasadena, CA. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Granada, Spain. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Centro de Astrobiología (INTA-CSIC), Torrejón de Ardoz, Madrid, Spain. Department of Atmospheric Sciences, Texas A&M University, College Station, TX.
The Vertical Dust Profile over Gale Crater, Mars2017In: Journal of Geophysical Research - Planets, ISSN 2169-9097, E-ISSN 2169-9100, Vol. 122, no 12, p. 2779-2792Article in journal (Refereed)

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

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

• 238.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Galaxies, High Energy Astrophysics and Cosmology at Institut de Recherche en Astrophysique et Planétologie.
Investigating super-Eddington accretion flows in Ultraluminous X-ray sources2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

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

• 239.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Field-Site Prototype for HABIT (FSP-HABIT): Characterizing Martian Salts Prior to the ExoMars 2020 Mission2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

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

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

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

• 240.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
A Bluetooth based intra-satellite communication system2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

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

• 241.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Cooling Air Management For Hybrid Electric Vehicles Using Combined 3D Aerodynamic & Thermodynamic CFD: For External Automotive Aerodynamics2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

This is a master thesis report in vehicle aerodynamics and cooling air management. The thesis is carried out at China Euro Vehicle Technology (CEVT) AB and is part of the course P7010T, Master Thesis in Space Engineering at Luleå University of Technology (LTU). The thesis has been supervised by Mattias Olander at CEVT and Gunnar Hellström at LTU and was done over 20 weeks during the spring semester of 2019. As the vehicle industry moves from mostly using combustion engines to hybrid and electric power systems the importance of decreasing cooling air drag has increased. Cooling air drag can be around 5-15% of the total drag, and a lot of research has been done over the years on how to decrease it. Cooling drag is defined as the force acting in x-direction from the cooling air flowing through the engine bay. The air is let in through the grilles to cool down the engine and escapes through different outtakes usually below the vehicle and through the wheelhouse. The air loses a lot of energy inside the engine bay as well as it changes in temperature. In this study a method has been developed to include the energy equation in the aerodynamic computational fluid dynamics (CFD) simulation. Research has also been done on which design parameters that affect the cooling air drag and how air ducts could be designed to better transport the flow to and from the radiators without loosing to much in energy. In the first part of this study a method was developed to solve the vehicle aerodynamics with energy equation included. All method development and design parameter tests weredone on the Sport Utility Vehicle (SUV) A model, which is a CEVT concept car. The model was first implemented on a simple symmetric model and then on a full model. It was tested both with a normal steady state solution and a pseudo transient solutions. The pseudo transient solution proved to solve for a faster convergence, although both methods worked well. Therefore the design parameter testing was chosen to be done with the pseudo transient solver.The design parameter testing was done in two steps, first opening and closing different outlets and then trying to implement different cooling air ducts. The first study showed that air through the wheelhouses increases the drag as well as having air entering only inthe upper grille and travelling down through floor and wheelhouse. In the second study,the area between the grilles and cooling package was sealed and inlet ducts were created to control the flow from the grilles to the cooling package. When just adding inlet ducts, the mass flow through the grilles was decreased, but the mass flow through the cooling package was increased due to less separation of the air, which lead to a drag reduction of 0.2%. Other design implementations was to reshape the wheelhouse outlets, therefore a wheelhouse outlet duct was designed. The ducts purpose was to lead the air out of the wheelhouse and behind the tire and exit the vehicle parallel to the free stream flow. The wheelhouse duct is most effective and decreases the drag force by 0.7%. An air duct was also designed to lead the flow after the cooling package fan to the outlets. The ducts purpose was to prevent the air from loosing in energy when rising to the roof of the engine bay, the duct compresses the air and leads it efficiently over the engine with a drag force decrease on 0.3%. The inlet duct, wheelhouse duct and after fan duct was all put together to a thesis design. Due to the higher mass flow through the cooling package the upper grille could be sealed by 9.9% and still allow the same mass flow through the cooling package as for the SUV A. The thesis design for improved cooling air management allowed a decrease of drag force timesarea by 0.9%. In conclusion there is much that can be done to improve the cooling air drag. It is most favorable to have a sealed volume with inlet air ducts before the cooling package, have outtakes aligned with the free stream flow, minimize cooling air to escape through the wheelhouse outlets and to minimize the height of the engine bay as much as possible.

• 242.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Aalto University .
Estimation of phases for compliant motion: Auto-regressive HMM, multi-class logistic regression, Learning from Demonstration (LfD), Gradient descent optimization2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
• 243.
Institute for Aerospace Studies, University of Toronto.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Institute for Aerospace Studies, University of Toronto.
Concurrent attitude and orbit control for Deorbiter CubeSats2020In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 97, article id 105616Article in journal (Refereed)

This paper details a concurrent attitude and orbit control method for a debris-removing nanosatellite, called deobriter CubeSat, during the rendezvous and synchronization maneuver with an uncontrollable tumbling debris object. The CubeSat is designed based on the utilization of an eight-unit form factor and commercially-available components with substantial space heritage, and is intended for the removal of sizable debris objects in low-Earth orbit. In particular, a low-thrust propulsion system is used for orbit control, as well as three reaction wheels allowing for a three-axis attitude control. Since the thruster can only produce force in one direction in the body frame, the spacecraft is considered to be underactuated. The controller employs the reaction wheels and the thruster to simultaneously rendezvous and synchronize the attitude of the CubeSat with the tumbling debris object, allowing for a concurrent attitude and position tracking. Detailed derivation of the concurrent controller is discussed, the effects of high-order derivatives are analyzed, and the stability of the system is proved. Simulation scenarios are created for two different thruster operation modes, namely, unsaturated thrust force and continuously-saturated thrust force, in order to verify the performance of the controller, as well as its robustness against gravity gradient disturbance torque and gravitational perturbation force.

• 244.
Institute for Aerospace Studies, University of Toronto .
Institute for Aerospace Studies, University of Toronto. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Institute for Aerospace Studies, University of Toronto.
A Deorbiter CubeSat for Active Orbital Debris Removal2018In: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 61, no 9, p. 2377-2392Article in journal (Refereed)

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

• 245.
Institute for Aerospace Studies, University of Toronto, Toronto, Ontario, Canada.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Concurrent attitude and orbit control for deorbiter CubeSat2020In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 97, article id 105616Article in journal (Refereed)

This paper details a concurrent attitude and orbit control method for a debris-removing nanosatellite, called deobriter CubeSat, during the rendezvous and synchronization maneuver with an uncontrollable tumbling debris object. The CubeSat is designed based on the utilization of an eight-unit form factor and commercially-available components with substantial space heritage, and is intended for the removal of sizable debris objects in low-Earth orbit. In particular, a low-thrust propulsion system is used for orbit control, as well as three reaction wheels allowing for a three-axis attitude control. Since the thruster can only produce force in one direction in the body frame, the spacecraft is considered to be underactuated. The controller employs the reaction wheels and the thruster to simultaneously rendezvous and synchronize the attitude of the CubeSat with the tumbling debris object, allowing for a concurrent attitude and position tracking. Detailed derivation of the concurrent controller is discussed, the effects of high-order derivatives are analyzed, and the stability of the system is proved. Simulation scenarios are created for two different thruster operation modes, namely, unsaturated thrust force and continuously-saturated thrust force, in order to verify the performance of the controller, as well as its robustness against gravity gradient disturbance torque and gravitational perturbation force.

• 246.
University of Toronto Institute for Aerospace Studies, 4925 Dufferin Street, Toronto.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Institute for Aerospace Studies, University of Toronto.
Assessment of active methods for removal of LEO debris2018In: Acta Astronautica, ISSN 0094-5765, E-ISSN 1879-2030, Vol. 144, p. 225-243Article in journal (Refereed)

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

• 247.
University of Toronto Institute for Aerospace Studies, 4925 Dufferin Street, Toronto.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Debris detumbler: An alternative approach to active debris removal2016In: Proceedings of the International Astronautical Congress, IAC, 2016Conference paper (Refereed)

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

• 248.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
A statistical study of incoherent scatter plasma line enhancements during the International Polar Year ’07-’08 in Svalbard2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

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

• 249.
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
Design and Analysis of a Dynamic SpaceWire Routing Protocol for Reconﬁgurable and Distributed On-Board Computing Systems2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

Future spacecrafts will require more computational and processing power to keep up with the growing demand in requirements and complexity. ScOSA is the next generation on-board computer developed by the German Aerospace Centre (DLR). The main motivation behind ScOSA is to replace the conventional on-board computer with distributed and reconfigurable computing nodes which provides higher performance, reliability, availability and stability by using a combination of the COTS components and reliable computing processors that are space qualified. In the current ScOSA system reconfiguration and routing of data between nodes are based on a static decision graph. SpaceWire protocol is used to communicate between nodes to provide reliability. The focus of the thesis is to design and implement a dynamic routing protocol for ScOSA which can be used in future for not only communicating between the nodes but also for reconfiguration. SpaceWire IPC is a customized protocol developed by DLR to provide communication between the nodes in a distributed network and to support monitoring, management and reconfiguration services. The dynamic routing protocol proposed in this thesis is primarily derived from the monitoring mechanism used in the SpaceWire IPC. PULL type monitoring mechanism is modelled and simulated using OMNeT++. The results obtained provide a qualitative outlook of the dynamic routing protocol implemented.

• 250.
Department of Physics, University of Helsinki, Finland. Max-Planck-Institut für extraterrestrische Physik, Garching, Germany.
Finnish Geospatial Research Institute FGI, Masala, Finland. Long Baseline Observatory, Socorro, USA. Astrogeo Center, Falls Church, USA. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Department of Physics, University of Helsinki, Finland. Department of Physics, University of Helsinki, Finland. Finnish Geospatial Research Institute FGI, Masala, Finland. Max-Planck-Institut für Radioastronomie, Bonn, Germany. Finnish Geospatial Research Institute FGI, Masala, Finland.
Radio Interferometric Observation of an Asteroid Occultation2018In: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 156, no 4, p. 1-10, article id 155Article in journal (Refereed)

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

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