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  • 301.
    Mihalikova, Maria
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Kirkwood, Sheila
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Tropopause fold occurrence rates over the Antarctic station Troll (72 degrees S, 2.5 degrees E)2013Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 31, nr 4, s. 591-598Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    One of the important mechanisms of stratosphere-troposphere exchange, which brings ozone-rich stratospheric air to low altitudes in extratropical regions, is transport related to tropopause folds. The climatology of folds has been studied at high latitudes of the Northern Hemisphere with the help of radars and global models. Global models supply information about fold occurrence rates at high latitudes of the Southern Hemisphere as well, but so far comparisons with direct measurements are rare. The Moveable Atmospheric Radar for Antarctica (MARA), a 54.5 MHz wind-profiler radar, has been operated at the Norwegian year-round station Troll, Antarctica (72 degrees S, 2.5 degrees E) since December 2011. Frequent tropopause fold signatures have been observed. In this study, based on MARA observations, an occurrence rate statistics of tropopause folds from December 2011 until November 2012 has been made, and radar data have been compared with the analysis from the European Center for Medium-Range Weather Forecasting (ECMWF). The fold occurrence rates exhibit an annual cycle with winter maximum and summer minimum and suggest significantly higher occurrence rates for the given location than those obtained previously by global model studies.

  • 302.
    Mihalikova, Maria
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Kirkwood, Sheila
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Vertical mixing in the lower troposphere by mountain waves over Arctic Scandinavia2011Ingår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 11, s. 31475-31493Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Measurements made by ozonesondes and by a 52 MHz wind-profiling radar during February and March 1997 are studied. The radar is located at Esrange, near Kiruna in Arctic Sweden, on the eastern flank of the Scandinavian mountains. Daily ozonesondes were launched from the same site. The radar vertical and horizontal wind measurements are used to identify times when mountain waves were present. Mean vertical gradients in ozone mixing ratio in the lower troposphere are determined in conditions with mountain waves present and when they were absent. Back-trajectories were calculated so that only air-masses with their origin to the west of the mountains were included in the final averages. The vertical gradient in ozone mixing ratio is found to be about twice as steep outside wave conditions as it is during mountain waves. This suggests a very high rate of vertical mixing, with an average eddy diffusivity of order 5000 m2 s−1. This is consistent with an earlier estimate of the occurrence rate of complete mixing by wave breaking over the mountain range.

  • 303.
    Mihalikova, Maria
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Kirkwood, Sheila
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Arnault, J.
    Polar Atmospheric Research, Swedish Institute of Space Physics, Box 812, 98128, Kiruna.
    Mikhaylova, D.
    Polar Atmospheric Research, Swedish Institute of Space Physics, Box 812, 98128, Kiruna.
    Observation of a tropopause fold by MARA VHF wind-profiler radar and ozonesonde at Wasa, Antarctica: Comparison with ECMWF analysis and a WRF model simulation2012Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 30, nr 9, s. 1411-1421Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tropopause folds are one of the mechanisms of stratosphere-troposphere exchange, which can bring ozone rich stratospheric air to low altitudes in the extra-tropical regions. They have been widely studied at northern mid-or high latitudes, but so far almost no studies have been made at mid-or high southern latitudes. The Moveable Atmospheric Radar for Antarctica (MARA), a 54.5 MHz wind-profiler radar, has operated at the Swedish summer station Wasa, Antarctica (73° S, 13.5° W) during austral summer seasons from 2007 to 2011 and has observed on several occasions signatures similar to those caused by tropopause folds at comparable Arctic latitudes. Here a case study is presented of one of these events when an ozonesonde successfully sampled the fold. Analysis from European Center for Medium Range Weather Forecasting (ECMWF) is used to study the circumstances surrounding the event, and as boundary co

  • 304.
    Mikael, Hedberg
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    CFD simulations of Luleälven: An examination of CFD as a tool forevaluating restoration possibilities of regulated dredgedrivers2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Dredged rivers remain from when lumber was floated downriver for processing and shipping purposes. This has left parts of some rivers in Sweden with shallow rocky beaches and deep central furrows. Restoration efforts of dredged unregulated rivers has shown positive results for fish populations. This report compares, by use of CFD two regulated parts of Luleälven, one dredged and one natural. The report looks at habitats where the Riverine Grayling prefers to lay its eggs and evaluates whether velocity and depth conditions could give an explanation for the lower population of the Riverine Grayling in the dredged river. For the water levels tested, usable areas exist for all cases, but the dredged river has substantially smaller areas suitable as a habitat. The river geometry seems to be the large issue for Mattisudden as its shallow wide riverbanks are not conducive to habitats for the Riverine Grayling. Surprisingly the "lower" test case for the dredged river showed a larger usable area than for the "higher" water level, for the same river and higher usable area than the natural river. For this case the water level is now so low that the shallow wide riverbanks are above the water level and only the central furrow is filled with water. This shows two avenues that can be used to improve the habitats for the Riverine Grayling, lower the water level, or raise the riverbanks.

  • 305.
    Millán, L.
    et al.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Read, W.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Kasai, Y.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Lambert, A.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Livesey, N.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Mendrok, Jana
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Sagawa, H.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Sano, T.
    Japanese Aerospace Exploration Agency, Cho-fu, Tokyo.
    Shiotani, M.
    Kyoto University.
    Wu, D.L.
    NASA Goddard Space Flight Center.
    SMILES ice cloud products2013Ingår i: Journal of Geophysical Research: Atmospheres, ISSN 2169-8996, Vol. 118, nr 12, s. 6468-6477Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Upper tropospheric water vapor and clouds play an important role in Earth's climate, but knowledge of them, in particular diurnal variation in deep convective clouds, is limited. An essential variable to understand them is cloud ice water content. The Japanese Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on board the International Space Station (ISS) samples the atmosphere at different local times allowing the study of diurnal variability of atmospheric parameters. We describe a new ice cloud data set consisting of partial Ice Water Path and Ice Water Content. Preliminary comparisons with EOS-MLS, CloudSat-CPR and CALIOP-CALIPSO are presented. Then, the diurnal variation over land and over open ocean for partial ice water path is reported. Over land, a pronounced diurnal variation peaking strongly in the afternoon/early evening was found. Over the open ocean, little temporal dependence was encountered. This data set is publicly available for download in HDF5 format.

  • 306.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Study on forest fire detection with satellite data2013Rapport (Övrigt vetenskapligt)
  • 307. Milz, Mathias
    et al.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    John, V.O.
    Met Office Hadley Centre, Exeter.
    Comparison of AIRS and AMSU-B monthly mean estimates of upper tropospheric humidity2009Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 36, nr L10804Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Satellite-borne measurements provide valuable information on the global distribution of upper tropospheric humidity (UTH), which represents the mean relative humidity in a layer approximately enclosed by the atmospheric pressure levels 500 and 200 hPa. Monthly mean distributions of microwave observations of UTH obtained from the Advanced Microwave Sounding Unit-B (AMSU-B) and the Humidity Sounder for Brazil (HSB) are compared to infrared observations of UTH from the Atmospheric Infrared Sounder (AIRS). All data sets for January 2003 show distributions as expected from climatologies. Data of AIRS and AMSU-B averaged on 1.5° × 1.5° lat-lon bins for January 2003 show good overall agreement. However, with 2.7%RH AIRS shows an unexpected wet mean bias, especially for regions where the influence of clouds is small or cloud affected measurements are excluded for both sensors. In regions where AIRS is sensitive to cloud affected measurements but not AMSU-B, the bias is reduced and partly negative.

  • 308.
    Milz, Mathias
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    John, V.O.
    Comparison of UTH Measurements from Satellite-Borne IR and MW Sensors2008Konferensbidrag (Övrigt vetenskapligt)
  • 309.
    Milz, Mathias
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Clarmann, T. von
    Forschungszentrum Karlsruhe.
    Bernath, P.
    University of York, Department of Chemistry.
    Boone, C.
    University of Waterloo, Deptment of Chemistry, Waterloo.
    Buehler, Stefan
    Chauhan, S.
    Forschungszentrum Karlsruhe.
    Deuber, B.
    University of Bern, Institute of Applied Physics, Atmospheric Research Group.
    Feist, D.G.
    Max-Planck-Institut für Biogeochemie, Jena.
    Funke, B.
    Instituto de Astrofísica de Andalucía CSIC, Granada.
    Glatthor, N.
    Forschungszentrum Karlsruhe.
    Grabowski, U.
    Forschungszentrum Karlsruhe.
    Griesfeller, A.
    CNRS, UVSQ, LATMOS, Verrieres Le Buisson.
    Haefele, A.
    University of Bern, Institute of Applied Physics, Atmospheric Research Group.
    Höpfner, M.
    Forschungszentrum Karlsruhe.
    Kämpfer, N.
    University of Bern, Institute of Applied Physics, Atmospheric Research Group.
    Kellmann, S.
    Forschungszentrum Karlsruhe.
    Linden, A.
    Forschungszentrum Karlsruhe.
    Müller, S.
    University of Bern, Institute of Applied Physics, Atmospheric Research Group.
    Nakajima, H.
    National Institute for Environmental Studies, Tsukuba.
    Oelhaf, H.
    Forschungszentrum Karlsruhe.
    Remsberg, E.
    NASA, Langley Research Centre, Scientific Directorate.
    Rohs, S.
    Forschungszentrum Julich.
    Russell, J.M.
    Hampton University, Department of Physics.
    Schiller, C.
    Forschungszentrum Julich.
    Sugita, T.
    National Institute for Environmental Studies, Tsukuba.
    Zhang, G.
    Forschungszentrum Karlsruhe.
    Validation of water vapour profiles (version 13) retrieved by the IMK/IAA scientific retrieval processor based on full resolution spectra measured by MIPAS on board Envisat2009Ingår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, nr 2, s. 379-399Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vertical profiles of stratospheric water vapour measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) with the full resolution mode between September 2002 and March 2004 and retrieved with the IMK/IAA scientific retrieval processor were compared to a number of independent measurements in order to estimate the bias and to validate the existing precision estimates of the MIPAS data. The estimated precision for MIPAS is 5 to 10% in the stratosphere, depending on altitude, latitude, and season. The independent instruments were: the Halogen Occultation Experiment (HALOE), the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS), the Improved Limb Atmospheric Spectrometer-II (ILAS-II), the Polar Ozone and Aerosol Measurement (POAM III) instrument, the Middle Atmospheric Water Vapour Radiometer (MIAWARA), the Michelson Interferometer for Passive Atmospheric Sounding, balloon-borne version (MIPAS-B), the Airborne Microwave Stratospheric Observing System(AMSOS), the Fluorescent Stratospheric Hygrometer for Balloon (FLASH-B), the NOAA frostpoint hygrometer, and the Fast In Situ Hygrometer (FISH). For the in-situ measurements and the ground based, air- and balloon borne remote sensing instruments, the measurements are restricted to central and northern Europe. The comparisons to satellite-borne instruments are predominantly at mid- to high latitudes on both hemispheres. In the stratosphere there is no clear indicationof a bias in MIPAS data, because the independent measurements in some cases are drier and in some cases are moister than the MIPAS measurements. Compared to the infrared measurements of MIPAS, measurements in the ultraviolet and visible have a tendency to be high, whereas microwave measurements have a tendency to be low. Theresults of chi2-based precision validation are somewhat controversial among the comparison estimates. However, for comparison instruments whose error budget also includes errors due to uncertainties in spectrally interfering species and where good coincidences were found, the chi2 values found are in the expected range or even below. This suggests that there is no evidence of systematically underestimated MIPAS random errors.

  • 310.
    Molina, Antonio
    et al.
    Centro de Astrobiología (INTA-CSIC), 28850 Torrejón de Ardoz, Madrid. Spain.
    López, Iván
    Universidad Rey Juan Carlos, 28933 Móstoles, Madrid. Spain.
    Prieto-Ballesteros, Olga
    Centro de Astrobiología (INTA-CSIC), 28850 Torrejón de Ardoz, Madrid. Spain.
    Fernández-Remolar, David
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. British Geological Survey, Nicker Hill, Keyworth NG12 5GG. United Kingdom.
    Ángel de Pablo, Miguel
    Universidad de Alcalá, 28871 Alcalá de Henares, Madrid. Spain.
    Gómez, Felipe
    Centro de Astrobiología (INTA-CSIC), 28850 Torrejón de Ardoz, Madrid.
    Coogoon Valles, western Arabia Terra: Hydrological evolution of a complex Martian channel system2017Ingår i: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 293, s. 27-44Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Coogoon Valles is an intricate fluvial system, and its main channel was formed during the Noachian period through the erosion of the clay-bearing basement of the Western Arabia Terra. This region is characterized by a thinner crust compared to the rest of the highlands and by the occurrence of massive phyllosilicate-bearing materials. The origin of this region is still under discussion. Its surface has been exposed to a large-scale volcanism, and several episodes of extensive denudation were primarily controlled by fluvial activity. In this regard, the study of the oldest channels in Arabia Terra is crucial for understanding the global geological evolution of early Mars. The reactivation of the hydrological system by sapping followed by aeolian erosion had reshaped the channel, as well as exposed ancient materials and landforms. The examination of the bed deposits suggests an old episode of detrital sedimentation covering the Noachian basement followed by an erosive event that formed the current Coogoon Valles configuration. A complex system of deltas and alluvial fans is situated at the termination of this channel, which has been proposed as a landing site for the upcoming ExoMars and Mars 2020 missions.

  • 311.
    Moore, Casey A.
    et al.
    Centre for Research in Earth and Space Sciences, York University, Earth and Space Sciences, Toronto.
    Moores, John E.
    York University, Toronto, Centre for Research in Earth and Space Sciences, York University, Earth and Space Sciences, Toronto.
    Lemmon, Mark T.
    Texas A&M University, College Station.
    Rafkin, Scot C.R.
    Southwest Research Institute, Boulder.
    Francis, Raymond
    University of Western Ontario, Centre for Planetary Science and Exploration, University of Western Ontario, London.
    Pla-Garcia, Jorge
    Centro de Astrobiologia, INTA-CSIC, Madrid.
    Haberle, Robert
    Ames Research Centre, NASA Ames Research Center, Moffett Field.
    Zorzano, María-Paz
    Centro de Astrobiologia, INTA-CSIC, Madrid , Instituto Nacional de Técnica Aeroespacial, Madrid, Centro de Astrobiologia, Madrid, Centro de Astrobiología (CSIC-INTA), Madrid.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Burton, John R.
    Centre for Research in Earth and Space Sciences, York University, Earth and Space Sciences, Toronto.
    A Full Martian Year of Line-of-Sight Extinction within Gale Crater, Mars as Acquired by the MSL Navcam through sol 9002016Ingår i: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 264, s. 102-108Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on line-of-sight extinction in northern Gale Crater, Mars as seen by the Mars Science Laboratory (MSL) rover, Curiosity from sol 100 to sol 900; a little more than an entire martian year. Navcam images oriented due north, which show the distant crater rim, the near ground and the sky allow the extinction due to dust within the crater to be determined. This line-of sight extinction is compared to a complementary dataset of column extinctions derived from Mastcam. The line-of-sight extinction within the crater is less than the column extinction for the majority of the martian year. This implies that the relatively low mixing ratio of dust within the crater as compared to the atmosphere above the crater rim persists through most of the year. This suggests relatively little mixing between the atmosphere above the crater and the atmosphere inside the crater and suggests that northern Gale Crater is a net sink of dust in the current era. The data does however show a yearly convergence of the line-of-sight extinction and the column-averaged extinction around Ls = 270° – 290°. This suggests that air above the crater mixes with air in the crater at this time, as predicted by mesoscale models. Matching line-of-sight and column extinction values are also seen around Ls ≈ 135°, a season that has only been observed once in this dataset, this is particularly interesting as the Rover Environmental Monitoring Station onboard Curiosity reports increased convective boundary layer heights in the same season.

  • 312.
    Moores, John E.
    et al.
    York University, Toronto.
    Lemmon, Mark T.
    Texas A&M University, College Station.
    Rafkin, Scot C R
    Southwest Research Institute, San Antonio, Texas.
    Francis, Raymond
    University of Western Ontario.
    Pla-Garcia, Jorge
    Centro de Astrobiologia, INTA-CSIC, Madrid.
    Juárez, Manuel De La Torre
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Bean, Keri
    Texas A&M University.
    Kass, David
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Haberle, Robert
    Ames Research Centre.
    Newman, Claire .E.
    Ashima Research, Pasadena.
    Mischna, Michael A.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Vasavada, Ashwin R.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Rennó, Nilton
    University of Michigan.
    Bell, Jim
    Arizona State University.
    III, Fred .J. Calef
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Cantor, Bruce
    Malin Space Science Systems.
    McConnochie, Timothy H.
    Department of Astronomy, University of Maryland, College Park.
    Harri, Ari-Matti
    Finnish Meteorological Institute.
    Genzer, Maria
    Finnish Meteorological Institute.
    Wong, Michael
    University of Michigan.
    Smith, Michael D.
    NASA Goddard Space Flight Center.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zorzano, María-Paz
    Centro de Astrobiologia, INTA-CSIC, Madrid , Instituto Nacional de Técnica Aeroespacial, Madrid.
    Kemppainen, Osku
    Finnish Meteorological Institute.
    McCullough, Emily
    University of Western Ontario.
    Atmospheric movies acquired at the Mars Science Laboratory landing site: Cloud Morphology, Frequency and Significance to the Gale Crater Water Cycle and Phoenix Mission Results2015Ingår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 55, nr 9, s. 2217-2238Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the first 360 sols (LS 150° to 5°), representing just over half a Martian year, of atmospheric monitoring movies acquired using the NavCam imager from the Mars Science Laboratory (MSL) Rover Curiosity. Such movies reveal faint clouds that are difficult to discern in single images. The data set acquired was divided into two different classifications depending upon the orientation and intent of the observation. Up to sol 360, 73 Zenith Movies and 79 Supra-Horizon Movies have been acquired and time-variable features could be discerned in 25 of each. The data set from MSL is compared to similar observations made by the Surface Stereo Imager (SSI) onboard the Phoenix Lander and suggests a much drier environment at Gale Crater (4.6°S) during this season than was observed in Green Valley (68.2°N) as would be expected based on latitude and the global water cycle. The optical depth of the variable component of clouds seen in images with features are up to 0.047 ± 0.009 with a granularity to the features observed which averages 3.8 degrees. MCS also observes clouds during the same period of comparable optical depth at 30 and 50 km that would suggest a cloud spacing of 2.0 to 3.3 km. Multiple motions visible in atmospheric movies support the presence of two distinct layers of clouds. At Gale Crater, these clouds are likely caused by atmospheric waves given the regular spacing of features observed in many Zenith movies and decreased spacing towards the horizon in sunset movies consistent with clouds forming at a constant elevation. Reanalysis of Phoenix data in the light of the NavCam equatorial dataset suggests that clouds may have been more frequent in the earlier portion of the Phoenix mission than was previously thought.

  • 313.
    Moradi, Isaac
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Quality control of global solar radiation using sunshine duration hours2009Ingår i: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 34, nr 1, s. 1-6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this study was to develop a new and automatic method for controlling the quality of daily global solar radiation, Gd, using sunshine duration hours. The new method has three levels of tests: first, Gd is compared against daily extraterrestrial radiation that is received on a horizontal surface (0.03×God≤Gdod); second, Gd should only exceed by a small amount of the daily clear sky irradiation that is observed under highly transparent clear skies (Gd<1.1Gcd); and third, the method uses a series of persistence checks that utilize the relation between daily global solar radiation and relative sunshine duration hours. The method is capable of identifying systematic and non-systematic errors and its ability has been shown in three different climates including semi-arid, coastal humid and very arid climates.

  • 314.
    Moradi, Isaac
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Alijani, Bohloul
    Department of Geography, Tarbiat Moalem University, Tehran.
    Muller, Richard
    German National Meteorological Service (DWD), Climate Monitoring Satellite Application Facility (CM-SAF), Offenbach.
    Kamali, Gholam Ali
    Atmospheric Sciences and Meteorological Research Center, Tehran.
    Evaluation of the Heliosat-II method using daily irradiation data for four stations in Iran2009Ingår i: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 83, nr 2, s. 150-156Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Efficient use of solar radiation needs detailed knowledge of its spatial and temporal variations. Such information can be achieved using interpolating measured irradiance by ground stations. But more reliable results can be obtained by processing geostationary satellite images. Heliosat is an algorithm which has been developed to estimate global horizontal irradiance at ground level from images taken in the visible band by the Meteosat satellites. The aim of this study was to evaluate the Heliosat-II model by using daily global solar irradiation data measured at the four radiometric stations in Iran as well as Meteosat-5 images which are recorded by a spacecraft over 63°E. Mean RMSD% and MBD% for all stations were 11.7% and 1.9%, respectively. The mean values of intercept, slope and correlation coefficient were 0.82 (kWhm-2), 1.05 and 0.93, respectively. Seasonally, the maximum RMSD occurs in autumn (22.1%) and the minimum is experienced in spring (8.4%). This accuracy is a great achievement for producing a high quality solar radiation atlas in a country such as Iran with very sparse radiometric network and frequently unreliable measured irradiation data.

  • 315.
    Moradi, Isaac
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    John, Viju
    Met Office Hadley Centre, Exeter.
    Eliasson, Salomon
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Comparing upper tropospheric humidity data from microwave satellite instruments and tropical radiosondes2010Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 115, nr 24, artikel-id D24310Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Atmospheric humidity plays an important role in the Earth's climate. Microwave satellite data provide valuable humidity observations in the upper troposphere with global coverage. In this study, we compare upper tropospheric humidity (UTH) retrieved from the Advanced Microwave Sounding Unit (AMSU-B) and the Microwave Humidity Sounder (MHS) against radiosonde data measured at four of the central facilities of the Atmospheric Radiation Measurement (ARM) program. The Atmospheric Radiative Transfer Simulator (ARTS) was used to simulate satellite brightness temperatures from the radiosonde profiles. Strong ice clouds were filtered out, as their influence on microwave measurements leads to incorrect UTH values. Day and night radiosonde profiles were analyzed separately, to take into account the radiosonde radiation bias. The comparison between radiosonde and satellite is most meaningful for data in cloud free, night time conditions, and with a time difference of less than 2 hours. We found good agreement between the two data sets. The satellite data are slightly moister than the radiosonde data, with a mean difference of 1-2.3 %RH, depending on the radiosonde site. Monthly gridded data were also compared, and showed slightly larger mean difference of up to 3.3 %RH, which can be explained by sampling issues.

  • 316. Moradi, Isaac
    et al.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    John, Viju O.
    Met Office Hadley Centre, Exeter.
    Comparing upper tropospheric humidity from microwave satellite instruments and IGRA radiosonde data2010Ingår i: 11th Specialist Meeting on Microwave Radiometry and Remote Sensing of the Environment, MicroRad, New York: IEEE Communications Society, 2010, s. 146-151Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this study, Advanced Microwave Sounding Unit (AMSU-B) and Microwave Humidity Sounder (MHS) observations are compared to radiosonde data from the Integrated Global Radiosonde Archive (IGRA) dataset. This comparison can be used to evaluate the overall quality of the radiosonde data. Microwave satellite data are influenced by thick ice clouds and radiosonde data show a day-time radiation dry bias. Therefore, we used night-time cloud-free data of the year 2009 for the comparison. Overall, radiosonde data from the former Soviet Union were up to 30 %RH moister than satellite data and the the rest of the world were up to 6 %RH drier than satellite data.

  • 317. Moradi, Isaac
    et al.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    John, V.O.
    Met Office Hadley Centre, Exeter.
    Reale, A.
    STAR, National Environmental Satellite, Data, and Information Service.
    Ferraro, R.R.
    STAR, National Environmental Satellite, Data, and Information Service.
    Evaluating instrumental inhomogeneities in global radiosonde upper tropospheric humidity data using microwave satellite data2013Ingår i: IEEE Transactions on Geoscience and Remote Sensing, ISSN 0196-2892, E-ISSN 1558-0644, Vol. 51, nr 6, s. 3615-3624Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, the overall quality of the water vapor profiles of global operational radiosonde data for the period 2000-2009 is investigated using upper tropospheric humidity (UTH) retrieved from microwave satellite data. Overall, the nighttime radiosonde data showed a dry bias (-5% to-15%) over Europe, Australia, and New Zealand and systematically moist bias (greater than 30%) over China and the former Soviet Union. The nighttime sonde data from the U.S. and Canada showed a bias between-10% and 20%. Most stations indicated a daytime radiation dry bias, except for a few stations from the U.S. and the former Soviet Union. A sensorwise comparison showed a large nighttime wet bias for the Russian (MRZ-3A and MARS) and Chinese GZZ-2 sensors, a relatively small nighttime wet bias for the U.S. Sippican and VIZ-B2 sensors, and a nighttime dry bias for the Chinese GTS1, Vaisala (RS80-A, RS80-H, RS90, RS92K, and RS92-SGP), and the U.S. VIZ-MKII sensors. All sensors had a daytime radiation dry bias, except for the Russian MRZ-3A sensor that had a daytime radiation wet bias that could be because of the daytime radiation bias correction. Because of the large differences between different radiosonde sensors, it is essential for UTH studies to only use the data measured using a single type of sensor at any given station.

  • 318.
    Moyano-Cambero, Carles E.
    et al.
    Institute of Space Sciences (IEEC-CSIC), Campus UAB, Carrer de Can Magrans.
    Trigo-Rodríguez, Josep M.
    Institute of Space Sciences (IEEC-CSIC), Campus UAB, Carrer de Can Magrans.
    Benito, M. Isabel
    Departamento de Estratigrafía-IGEO, Facultad de Ciencias Geológicas, Universidad Complutense de Madrid-CSIC.
    Alonso-Azcárate, Jacinto
    Fac. de Ciencias Ambientales y Bioquímica, Universidad de Castilla-La Mancha.
    Lee, Martin R.
    School of Geographical and Earth Sciences, University of Glasgow.
    Mestres, Narcís
    Institut de Cìencia de Materials de Barcelona (ICMAB-CSIC) .
    Martínez-Jiménez, Marina
    Institute of Space Sciences (IEEC-CSIC), Campus UAB, Carrer de Can Magrans.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Fraxedas, Jordi
    Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and the Barcelona Institute of Science and Technology, Campus UAB.
    Petrographic and geochemical evidence for multiphase formation of carbonates in the Martian orthopyroxenite Allan Hills 840012017Ingår i: Meteoritics and Planetary Science, ISSN 1086-9379, E-ISSN 1945-5100, Vol. 52, nr 6, s. 1030-1047Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Martian meteorites can provide valuable information about past environmental conditions on Mars. Allan Hills 84001 formed more than 4 Gyr ago, and owing to its age and long exposure to the Martian environment, and this meteorite has features that may record early processes. These features include a highly fractured texture, gases trapped during one or more impact events or during formation of the rock, and spherical Fe-Mg-Ca carbonates. In this study, we have concentrated on providing new insights into the context of these carbonates using a range of techniques to explore whether they record multiple precipitation and shock events. The petrographic features and compositional properties of these carbonates indicate that at least two pulses of Mg- and Fe-rich solutions saturated the rock. Those two generations of carbonates can be distinguished by a very sharp change in compositions, from being rich in Mg and poor in Fe and Mn, to being poor in Mg and rich in Fe and Mn. Between these two generations of carbonate is evidence for fracturing and local corrosion

  • 319.
    Muller, S.C.
    et al.
    University of Bern.
    Kämpfer, N.
    University of Bern.
    Feist, D.G.
    Max-Planck-Institut for Biogeochemistry, Jena.
    Haefele, A.
    University of Bern.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Sitnikov, N.
    Central Aerological Observatory, Moscow Region.
    Schiller, C.
    Forschungszentrum Jülich GmbH, Jülich.
    Kiemle, C.
    DLR-Institut für Physik der Atmosphäre, Oberpfaffenhofen.
    Urban, J.
    Chalmers University of Technology.
    Validation of stratospheric water vapour measurements from the airborne microwave radiometer AMSOS2008Ingår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 8, nr 12, s. 3169-3183Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the validation of a water vapour dataset obtained by the Airborne Microwave Stratospheric Observing System AMSOS, a passive microwave radiometer operating at 183 GHz. Vertical profiles are retrieved from spectra by an optimal estimation method. The useful vertical range lies in the upper troposphere up to the mesosphere with an altitude resolution of 8 to 16 km and a horizontal resolution of about 57 km. Flight campaigns were performed once a year from 1998 to 2006 measuring the latitudinal distribution of water vapour from the tropics to the polar regions. The obtained profiles show clearly the main features of stratospheric water vapour in all latitudinal regions. Data are validated against a set of instruments comprising satellite, ground-based, airborne remote sensing and in-situ instruments. It appears that AMSOS profiles have a dry bias of 0 to ĝ€"20%, when compared to satellite experiments. Also a comparison between AMSOS and in-situ hygrosondes FISH and FLASH have been performed. A matching in the short overlap region in the upper troposphere of the lidar measurements from the DIAL

  • 320.
    Muralidharan, Vijay
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Concurrent rendezvous control of underactuated spacecraft2017Ingår i: Acta Astronautica, ISSN 0094-5765, E-ISSN 1879-2030, Vol. 138, s. 28-42Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The concurrent control of spacecraft equipped with one-axis unilateral thruster and three-axis attitude actuator is considered in this paper. The proposed control law utilizes attitude control channels along with the single thrust force concurrently, for three-dimensional trajectory tracking and rendezvous with a target object. The concurrent controller also achieves orbital transfer to low Earth orbits with long range separation. To demonstrate the orbit transfer capabilities of the concurrent controller, a smooth elliptical orbit transfer trajectory for co-planar circular orbits is designed. The velocity change and energy consumption of the designed orbit transfer trajectory is observed to be equivalent to that of Hohmann transfer.

  • 321.
    Murjani, Monali
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Development of passivation valve for use in space2018Självständigt arbete på avancerad nivå (magisterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The normally closed valve which has a snap disk as an actuator will be used in space for passivation of propellant at the end of the mission. So currently it's been developed to match the requirements for operating in space. The current stage consists of design modifications and testing. Initially, a hermetically sealed one-shot valve was developed for the ExoMars Pasteur Payload. Later based on new requirements from ESA for the different objective of space mission the valve is modified with large tube diameters as inlet and outlet and whole valve body assembly made from stainless steel. The valve body is designed in a way so that 7 to 8 snap disk can be fitted as the number of a snap disk is obtained from certain test to determine the force value so that the spike can pierce the membrane and let the gas flow out. The force produced by the snap disk and force required to pierce the membrane was tested with certain test setups which were designed and manufactured. Thermal, stress and flow simulations are done in ANSYS and SolidWorks software.

  • 322.
    Navas-Guzmán, Francisco
    et al.
    Institute of Applied Physics, University of Bern.
    Kämpfer, Nklaus
    Institute of Applied Physics, University of Bern.
    Murk, Axel
    Institute of Applied Physics, University of Bern.
    Larsson, Richard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Meteorological Institute, Center for Earth System Research and Sustainability, University of Hamburg.
    Eriksson, Patrik
    Chalmers University of Technology, Chalmers University of Technology, Department of Earth and Space Sciences.
    Zeeman effect in atmospheric O2 measured by ground-based microwave radiometry2015Ingår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 8, nr 4, s. 1863-1874Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work we study the Zeeman effect on stratospheric O2 using ground-based microwave radiometer measurements. The interaction of the Earth magnetic field with the oxygen dipole leads to a splitting of O2 energy states, which polarizes the emission spectra. A special campaign was carried out in order to measure this effect in the oxygen emission line centered at 53.07 GHz. Both a fixed and a rotating mirror were incorporated into the TEMPERA (TEMPERature RAdiometer) in order to be able to measure under different observational angles. This new configuration allowed us to change the angle between the observational path and the Earth magnetic field direction. Moreover, a high-resolution spectrometer (1 kHz) was used in order to measure for the first time the polarization state of the radiation due to the Zeeman effect in the main isotopologue of oxygen from ground-based microwave measurements. The measured spectra showed a clear polarized signature when the observational angles were changed, evidencing the Zeeman effect in the oxygen molecule. In addition, simulations carried out with the Atmospheric Radiative Transfer Simulator (ARTS) allowed us to verify the microwave measurements showing a very good agreement between model and measurements. The results suggest some interesting new aspects for research of the upper atmosphere

  • 323.
    Nazarious, Miracle Israel
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Design, Development and Characterization of a Digital Sun Sensor prototype for Nano Satellite Applications2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Sun sensors serve as eyes of satellites. It is one of the basic components in satellites used for the purpose of determining the position of the sun in order to properly orient the solar arrays. The technological challenge involved in such sensors is to find the right balance between the field-of-view and the accuracy characteristics. For every sun sensor, there is a trade-off between these two performance parameters which has to be optimized for the expected performance requirements. Developing a low-weight, low-power sun sensorfor nano-satellite applications managing better performance in terms of field-of-view and accuracy is the challenge, this project has accepted to address.

    The true motivation behind this project was to develop an advanced solar-powered, bluetooth enabled digital sun sensor entitled as Multihead Autonomous Wireless Digital Sun Sensor (MAWDSS). To reach this ambitious goal, the footpath to be followed includes developing a prototype of a digital sun sensor and an autonomous wireless digitalsun sensor leading to the final product.

    This thesis work lays the first step and proposes a design of a digital sun sensor using low-cost commercial-off-the-shelf (COTS) components, develop a prototype and conduct performance characterization to compare with a commercial benchmarking sun sensor.The desired performance requirements were predefined prior to describing the detailed design aspects of the sun sensor. The problems encountered during experimental testing and the recommended suggestions to overcome them are presented.

    This thesis defines a complete product development life cycle involving skills from all three aspects of engineering: mechanical, electrical and programming. Each individual regime of the project are properly addressed with relevant figures and plots in separate chapters for the ease of following the report.

  • 324.
    Newsom, Horton E.
    et al.
    Institute of Meteoritics, Department of Earth and Planetary Sciences, Albuquerque, New Mexico.
    Mangold, Nicolas
    LPGN, CNRS, UMR 6112, Université Nantes.
    Kah, Linda C.
    Department of Earth and Planetary Sciences, University of Tennessee, Knoxville.
    Williams, Joshua M.
    Institute of Meteoritics, Department of Earth and Planetary Sciences, Albuquerque, New Mexico.
    Arvidson, Ray E.
    Washington University, St. Louis.
    Stein, Nathan
    Washington University, St. Louis.
    Ollila, Ann M.
    Institute of Meteoritics, Department of Earth and Planetary Sciences, Albuquerque, New Mexico.
    Bridges, John C.
    Space Research Centre, Department of Physics and Astronomy, University of Leicester.
    Schwenzer, Susanne P.
    Department of Physical Science, The Open University, Walton Hall, Milton Keynes.
    King, Penelope L.
    Research School of Earth Sciences, Australian National University, Canberra.
    Grant, John A.
    Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Washington.
    Pinet, Patrick
    Université Paul Sabatier, Institut de Recherche en Astrophysique et Planétologie (IRAP), Toulouse.
    Bridges, Nathan T.
    Applied Physics Laboratory, Laurel, Maryland.
    III, Fred Calef
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Wiens, Roger C.
    Los Alamos National Laboratory.
    Spray, John G.
    Planetary and Space Science Centre, University of New Brunswick, Fredericton.
    Vaniman, David T.
    Planetary Science Institute, Tucson.
    Elston, Wolf E.
    Institute of Meteoritics, Department of Earth and Planetary Sciences, Albuquerque, New Mexico.
    Berger, Jeff A.
    University of Western Ontario, London.
    Garvin, James B.
    NASA Goddard Space Flight Center, Greenbelt, Maryland.
    Palucis, Marisa C.
    Department of Earth and Planetary Science, University of California, Berkeley.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Gale crater and impact processes: Curiosity's first 364 Sols on Mars2015Ingår i: Icarus (New York, N.Y. 1962), ISSN 0019-1035, E-ISSN 1090-2643, Vol. 249, s. 108-128Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Impact processes at all scales have been involved in the formation and subsequent evolution of Gale crater. Small impact craters in the vicinity of the Curiosity MSL landing site and rover traverse during the 364 Sols after landing have been studied both from orbit and the surface. Evidence for the effect of impacts on basement outcrops may include loose blocks of sandstone and conglomerate, and disrupted (fractured) sedimentary layers, which are not obviously displaced by erosion. Impact ejecta blankets are likely to be present, but in the absence of distinct glass or impact melt phases are difficult to distinguish from sedimentary/volcaniclastic breccia and conglomerate deposits. The occurrence of individual blocks with diverse petrological characteristics, including igneous textures, have been identified across the surface of Bradbury Rise, and some of these blocks may represent distal ejecta from larger craters in the vicinity of Gale. Distal ejecta may also occur in the form of impact spherules identified in the sediments and drift material. Possible examples of impactites in the form of shatter cones, shocked rocks, and ropy textured fragments of materials that may have been molten have been observed, but cannot be uniquely confirmed. Modification by aeolian processes of craters smaller than 40 m in diameter observed in this study, are indicated by erosion of crater rims, and infill of craters with aeolian and airfall dust deposits. Estimates for resurfacing suggest that craters less than 15 m in diameter may represent steady state between production and destruction. The smallest candidate impact crater observed is ∼0.6 m in diameter. The observed crater record and other data are consistent with a resurfacing rate of the order of 10 mm/Myr; considerably greater than the rate from impact cratering alone, but remarkably lower than terrestrial erosion rates.

  • 325.
    Niles, P.B.
    et al.
    Astromaterials Research and Exploration Science, NASA Johnson Space Center, Houston.
    Archer, P.D.
    Jacobs Technology, NASA Johnson Space Center.
    Heil, E.
    HX5-Jacobs JETS Contract, NASA Johnson Space Center, Houston.
    Eigenbrode, J.
    NASA Goddard Space Flight Center.
    McAdam, A.
    NASA Goddard Space Flight Center.
    Sutter, B.
    Jacobs Technology, NASA Johnson Space Center.
    Franz, H.
    NASA Goddard Space Flight Center.
    Navarro-Gonzalez, R.
    Instituto Andaluz de Cienccias de la Tierra (CSIC-UGR), Grenada.
    Ming, D.
    Astromaterials Research and Exploration Science, NASA Johnson Space Center, Houston.
    Mahaffy, P.
    NASA Goddard Space Flight Center.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Instituto Andaluz de Cienccias de la Tierra (CSIC-UGR), Grenada.
    Zorzano, M.
    Centro de Astrobiologia, INTA-CSIC, Madrid.
    Investigating CO2 reservoirs at Gale Crater and evidence for a dense early atmosphere2015Konferensbidrag (Refereegranskat)
  • 326.
    Nilsson, Daniel
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Evaluation of Secure Long Distance Communication in Non-Urban Environments2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 327.
    Nilsson, H.
    et al.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Carlsson, Ella
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Gunell, H.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Futaana, Y.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Lundin, R.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Fedorov, A.
    Centre d’Etude Spatiale des Rayonnements, Toulouse.
    Soobiah, Y.
    Mullard Space Science Laboratory, Imperial College.
    Coates, A.
    Mullard Space Science Laboratory, Imperial College.
    Fränz, M.
    MPI für Sonnensystemforschung, Katlenberg-Lindau.
    Roussos, E.
    MPI für Sonnensystemforschung, Katlenberg-Lindau.
    Investigation of the influence of magnetic anomalies on ion distributions at Mars2006Ingår i: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 126, nr 1-4, s. 355-372Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using data from the Mars Express Ion Mass Analyzer (IMA) we investigate the distribution of ion beams of planetary origin and search for an influence from Mars crustal magnetic anomalies. We have concentrated on ion beams observed inside the induced magnetosphere boundary (magnetic pile-up boundary). Some north-south asymmetry is seen in the data, but no longitudinal structure resembling that of the crustal anomalies. Comparing the occurrence rate of ion beams with magnetic field strength at 400 km altitude below the spacecraft (using statistical Mars Global Surveyor results) shows a decrease of the occurrence rate for modest (< 40 nT) magnetic fields. Higher magnetic field regions (above 40 nT at 400 km) are sampled so seldom that the statistics are poor but the data is consistent with some ion outflow events being closely associated with the stronger anomalies. This ion flow does not significantly affect the overall distribution of ion beams around Mars.

  • 328.
    Nilsson, H.
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Swedish Institute of Space Physics .
    Gunell, H.
    Belgian Institute for Space Aeronomy.
    Karlsson, T.
    Department of Space and Plasma Physics, School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, Stockholm.
    Brenning, N.
    Department of Space and Plasma Physics, School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, Stockholm.
    Henri, P.
    Laboratoire de Physique et Chimie de l’Environnement et de l’Espace (LPC2E), UMR 7328 CNRS – Université d’Orléans.
    Goetz, C.
    Technische Universität Braunschweig, Institute for Geophysics and Extraterrestrial Physics.
    Eriksson, A.I.
    Swedish Institute of Space Physics, Ångström Laboratory.
    Behar, E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Swedish Institute of Space Physics.
    Stenberg-Wieser, G.
    Swedish Institute of Space Physics .
    Vallières, X.
    Laboratoire de Physique et Chimie de l’Environnement et de l’Espace (LPC2E), UMR 7328 CNRS – Université d’Orléans.
    Size of a plasma cloud matters The polarisation electric field of a small-scale comet ionosphere2018Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 616, artikel-id A50Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context. The cometary ionosphere is immersed in fast flowing solar wind. A polarisation electric field may arise for comets much smaller than the gyroradius of pickup ions because ions and electrons respond differently to the solar wind electric field. Aims. A situation similar to that found at a low activity comet has been modelled for barium releases in the Earth's ionosphere. We aim to use such a model and apply it to the case of comet 67P Churyumov-Gerasimenko, the target of the Rosetta mission. We aim to explain the significant tailward acceleration of cometary ions through the modelled electric field. Methods. We obtained analytical solutions for the polarisation electric field of the comet ionosphere using a simplified geometry. This geometry is applicable to the comet in the inner part of the coma as the plasma density integrated along the magnetic field line remains rather constant. We studied the range of parameters for which a significant tailward electric field is obtained and compare this with the parameter range observed. Results. Observations of the local plasma density and magnetic field strength show that the parameter range of the observations agree very well with a significant polarisation electric field shielding the inner part of the coma from the solar wind electric field. Conclusions. The same process gives rise to a tailward directed electric field with a strength of the order of 10% of the solar wind electric field. Using a simple cloud model we have shown that the polarisation electric field, which arises because of the small size of the comet ionosphere as compared to the pick up ion gyroradius, can explain the observed significant tailward acceleration of cometary ions and is consistent with the observed lack of influence of the solar wind electric field in the inner coma.

  • 329.
    Nilsson, Hans
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Barghouthi, Imad A.
    Department of Physics, Al-Quds University, Jerusalem.
    Slapak, Rikard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Eriksson, A.I
    Swedish Institute of Space Physics, Uppsala.
    André, M.
    Swedish Institute of Space Physics, Uppsala.
    Hot and cold ion outflow: Observations and implications for numerical models2013Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 118, nr 1, s. 105-117Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cluster observations of oxygen ion outflow and low-frequency waves at high altitude above the polar cap and cold ion outflow in the lobes are used to determine ion heating rates and low-altitude boundary conditions suitable for use in numerical models of ion outflow. Using our results, it is possible to simultaneously reproduce observations of high-energy O+ ions in the high-altitude cusp and mantle and cold H+ ions in the magnetotail lobes. To put the Cluster data in a broader context, we first compare the average observed oxygen temperatures and parallel velocities in the high-altitude polar cap with the idealized cases of auroral (cusp) and polar wind (polar cap) ion outflow obtained from a model based on other data sets. A cyclotron resonance model using average observed electric field spectral densities as input fairly well reproduces the observed velocities and perpendicular temperatures of both hot O+ and cold H+, if we allow the fraction of the observed waves, which is efficient in heating the ions to increase with altitude and decrease toward the nightside. Suitable values for this fraction are discussed based on the results of the cyclotron resonance model. Low-altitude boundary conditions, ion heating rates, and centrifugal acceleration are presented in a format suitable as input for models aiming to reproduce the observations

  • 330.
    Nilsson, Hans
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Hamrin, Maria
    Department of Physics, Umeå University.
    Pitkänen, Timo
    Department of Physics, Umeå University.
    Karlsson, Tomas
    Space and Plasma Physics, School of Electrical Engineering Royal Institute of Technology Stockholm.
    Slapak, Rikard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Andersson, Laila O.
    Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado.
    Gunell, Herbert
    Swedish Institute of Space Physics / Institutet för rymdfysik , Belgian Institute for Space Aeronomy, Brussels.
    Schillings, Audrey
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Vaivads, Andris
    Swedish Institute of Space Physics, Uppsala.
    Oxygen ion response to proton bursty bulk flows2016Ingår i: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 121, nr 8, s. 7535-7546Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 331.
    Nilsson, Hans
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Slapak, Rikard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Barghouthi, I.A.
    Department of Physics, Al-Quds University, Jerusalem.
    Eriksson, A.I.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    André, M.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Hot and cold ion outflow: Spatial distribution of ion heating2012Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 332.
    Nilsson, Hans
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Wieser, Gabriella Stenberg
    Swedish Institute of Space Physics.
    Behar, Etienne
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Wedlund, Cyril Simon
    Aalto University, School of Electrical Engineering, Department of Radio Science and Engineering.
    Gunell, Herbert
    Belgian Institute for Space Aeronomy, Brussels.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics.
    Lundin, Rickard
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Barabash, Stas
    Swedish Institute of Space Physics.
    Wieser, Martin
    Swedish Institute of Space Physics.
    Carr, Chris
    Imperial College London.
    Cupido, Emanuele
    Imperial College London.
    Burch, James L.
    Southwest Research Institute, 6220 Culebra Road, San Antonio.
    Fedorov, Andrei
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Savaud, Jean-André
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Koskinen, Hannu
    Department of Physics, University of Helsinki.
    Kallio, Esa
    Aalto University, School of Electrical Engineering, Department of Radio Science and Engineering.
    Lebreton, Jean-Pierre
    Laboratoire de Physique et Chimie de l’Environnement et de l’Espace (LPC2E).
    Eriksson, Anders
    Swedish Institute of Space Physics, Ångström Laboratory.
    Edberg, Niklas
    Swedish Institute of Space Physics, Ångström Laboratory.
    Goldstein, Raymond
    Belgian Institute for Space Aeronomy, Brussels.
    Henri, Pierre
    Laboratoire de Physique et Chimie de l’Environnement et de l’Espace (LPC2E).
    Coenders, Christoph
    Technische Universität–Braunschweig, Institute for Geophysics and Extraterrestrial Physics.
    Mokashi, Prachet
    Southwest Research Institute, 6220 Culebra Road, San Antonio.
    Nemeth, Zoltan
    Wigner Research Centre for Physics, 1121 Konkoly Thege Street 29-33, Budapest.
    Richter, Ingo
    Technische Universität–Braunschweig, Institute for Geophysics and Extraterrestrial Physics.
    Rubin, Martin
    Physikalisches Institut, University of Bern.
    Birth of a comet magnetosphere: A spring of water ions2015Ingår i: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 347, nr 6220, artikel-id aaa0571Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 333.
    Nilsson, Hans
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Wieser, Gabriella Stenberg
    Swedish Institute of Space Physics.
    Behar, Etienne
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Wedlund, Cyril Simon
    Aalto University, School of Electrical Engineering, Department of Radio Science and Engineering.
    Kallio, Esa
    Finnish Meteorological Institute, Aalto University, School of Electrical Engineering, Department of Radio Science and Engineering.
    Gunell, Herbert
    Swedish Institute of Space Physics / Institutet för rymdfysik , Belgian Institute for Space Aeronomy, Brussels.
    Edberg, N.J.T.
    Swedish Institute of Space Physics, Uppsala.
    Eriksson, Anders
    Swedish Institute of Space Physics, Ångström Laboratory.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics.
    Koenders, Christoph
    Institut für Geophysik und Extraterrestrische Physik, Technische Universität Braunschweig.
    Wieser, Martin
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Lundin, Rickard
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Barabash, Stas
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Mandt, Kathleen E.
    Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Burch, James L.
    Southwest Research Institute, 6220 Culebra Road, San Antonio.
    Goldstein, Raymond M.
    Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Mokashi, Prachet
    Southwest Research Institute, 6220 Culebra Road, San Antonio.
    Carr, Chris
    Imperial College London.
    Cupido, Emanuele
    Imperial College London.
    Fox, P.T.
    Imperial College London.
    Szego, Karoly
    Wigner Research Centre for Physics, 1121 Konkoly Thege Street 29-33, Budapest.
    Nemeth, Zoltan
    Wigner Research Centre for Physics, 1121 Konkoly Thege Street 29-33, Budapest.
    Fedorov, Andrei
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Sauvaud, J.A.
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Koskinen, Hannu
    Department of Physics, University of Helsinki.
    Geiger, B.
    Rosetta Science Ground Segment, Science and Robotic Exploration (SRE-OOR).
    Evolution of the ion environment of comet 67P/Churyumov-Gerasimenko2015Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 583, artikel-id A20Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 334.
    Nilsson, Max
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Performance Comparison of Localization Algorithms for UWB Measurements with Closely Spaced Anchors2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Tracking objects or people in an indoor environment has a wide variety of uses in many different areas, similarly to positioning systems outdoors. Indoor positioning systems operate in a very different environment however, having to deal with obstructions while also having high accuracy. A common solution for indoor positioning systems is to have three or more stationary anchor antennas spread out around the perimeter of the area that is to be monitored. The position of a tag antenna moving in range of the anchors can then be found using trilateration. One downside of such a setup is that the anchors must be setup in advance, meaning that rapid deployment to new areas of such a system may be impractical. This thesis aims to investigate the possibility of using a different setup, where three anchors are placed close together, so as to fit in a small hand-held device. This would allow the system to be used without any prior setup of anchors, making rapid deployment into new areas more feasible.

    The measurements done by the antennas for use in trilateration will always contain noise, and as such algorithms have had to be developed in order to obtain an approximation of the position of a tag in the presence of noise. These algorithms have been developed with the setup of three spaced out anchors in mind, and may not be sufficiently accurate when the anchors are spaced very closely together. To investigate the feasibility of such a setup, this thesis tested four different algorithms with the proposed setup, to see its impact on the performance of the algorithms. The algorithms tested are the Weighted Block Newton, Weighted Clipped Block Newton, Linear Least Squares and Non-Linear Least Squares algorithms. The Linear Least Squares algorithm was also run with measurements that were first run through a simple Kalman filter. Previous studies have used the algorithms to find an estimated position of the tag and compared their efficiency using the positional error of the estimate. This thesis will also use the positional estimates to determine the angular position of the estimate in relation to the anchors, and use that to compare the algorithms.

    Measurements were done using DWM1001 Ultra Wideband (UWB) antennas, and four different cases were tested. In case 1 the anchors and tag were 10 meters apart in line-of-sight, case two were the same as case 1 but with a person standing between the tag and the anchors. In case 3 the tag was moved behind a wall with an adjacent open door, and in case 4 the tag was in the same place as in case 3 but the door was closed.

    The Linear Least Squares algorithm using the filtered measurements was found to be the most effective in all cases, with a maximum angular error of less than 5$^\circ$ in the worst case. The worst case here was case 2, showing that the influence of a human body has a strong effect on the UWB signal, causing large errors in the estimates of the other algorithms. The presence of a wall in between the anchors and tag was found to have a minimal impact on the angular error, while having a larger effect on the spatial error.

    Further studies regarding the effects of the human body on UWB signals may be necessary to determine the feasibility of handheld applications, as well as the effect of the tag and/or the anchors moving on the efficiency of the algorithms.

  • 335.
    Nilsson, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Flow Separation Control Utilizing Plasma Actuators2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

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

  • 336. Noelle, A
    et al.
    Hartmann, G.K
    Fahr, A
    Larry, D
    Lee, Y.P
    Locht, R
    Limao-Vieira, P
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Orlando, J.J
    Salama, F
    Vandaele, A.C
    Wayne, R.P
    Wu, C.Y.R
    UV/Vis+ Spectra Data base2015Dataset (Refereegranskat)
  • 337. Norberg, O.
    et al.
    Puccio, W.
    Olsen, J.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Andersson, L.
    Winningham, J.D.
    Jonsson, U.
    Luleå tekniska universitet.
    Eriksson, Magnus
    Munin: a student nanosatellite for space weather information1999Ingår i: Microsatellites as research tools: Proceedings of COSPAR Colloquium on Microsatellites as Research Tools held in Tainan, Taiwan, 14-17 December 1997 / edited by Fei-Bin Hsiao., Elsevier, 1999Konferensbidrag (Refereegranskat)
  • 338.
    Nordström, T.
    et al.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Stenberg, G.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zhang, T.L.
    Austrian Academy of Sciences, Space Research Institute, Graz.
    Venus ion outflow estimates at solar minimum: Influence of reference frames and disturbed solar wind conditions2013Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 118, nr 6, s. 3592-3601Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 339.
    Nukala, Madhuri
    et al.
    Department of Natural Sciences, Engineering and Mathematics, Mid Sweden University, SE 851 70, Sundsvall, Sweden.
    Mendrok, Jana
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Analysis of light scattering by two-dimensional inhomogeneities in paper using general radiative transfer theory2014Ingår i: AIP Conference Proceedings, ISSN 0094-243X, E-ISSN 1551-7616, Vol. 1637, s. 750-758Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lateral light scattering simulations of printed dots are analyzed using general radiative transfer theory. We investigated the appearance of a printed paper in relation to the medium parameters like thickness of the paper sample, its optical properties, and the asymmetry factor. It was found that the appearance of a print greatly depends on these factors making it either brighter or darker. A thicker substrate with higher single scattering albedo backed with an absorbing surface makes the dots brighter due to increased number of scattering events. Additionally, it is shown that the optical effects of print also depend on illuminating and viewing angles along with the depth of ink penetration. A larger single scattering angle implies less intensity and the dots appear much blurred due to the shadowing effect prominent when viewed from sides. A fully penetrated dot of the same extinction coefficient as a partial penetrated one is darker due to increased absorption. These results can be used in applications dealing with lateral light scattering.

  • 340.
    Nyström, Max
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    GNSS Interference Localization Through PDOA-Methods2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

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

  • 341.
    Olsson, Patrik
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Martian Caves as Special Region Candidates: A simulation in ANSYS Fluent on how caves on Mars are, and what their conditions would be for being considered as special regions.2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    One of the most interesting questions about Mars is if life ever existed on it. One of the main requirements for life to exist as we know it is the presence of liquid water. It has been suggested by Martín-Torres et al. (2015a) that a daily-transient liquid water cycle takes place on the surface of Mars through deliquescence and efforescence (binding and releasing of water vapour) of perchloratic salts in the Martian soil. Given the right conditions regarding water activity and temperature, certain planetary areas have been defined as Special Regions where there is a chance of life-form reproduction to occur (Kminek et al. 2017). Sub-surface cavities and caves are defined as such and are still a relatively unexplored and not yet studied feature of the Martian surface. This report is an assessment of the environmental conditions in Martian subsurface cavities such as caves and how it can be considered as a Special Region. Based on observations of lava tubes made by Cushing and Titus (2010) with atmospheric and thermal data from REMS on board the Curiosity rover by Martín-Torres et al. (2015b), simulation models were set up in ANSYS Fluent to examine the behaviour of the temperature and relative humidity within these caves. Different properties of the studied models included size, shape, inclination, materials of the ground composition and air flow behaviour. The results showed that a cave roof with a thickness greater than 1-2 m prevents the ground temperature variation during the day to have any considerable impact on the air temperature in the cave which implies that the thermal waves are the main driving factor of the thermal environment in larger models. The average temperature and relative humidities throughout the entire models resulted in unfavourable conditions (relative humidity under 20% RH) to allow for any perchloratic salts to hydrate or form brines. The most interesting results were found in smaller models where different phenomena with higher relative humidity near the floor and in corners occurred for several hours during the same day. This happened at certain times during the day (LMST 7 and 17) when the inlet temperature surpassed the average temperature in the cave and resulted in relative humidities of up to 90% RH which potentially could allow perchloratic salts to stay in brine form, or at least in a hydrated state throughout the day. While the low temperatures in today's Martian caves may be too harsh for life forms to exist, a previous warmer climate might have allowed for extremophiles to thrive in highly saline solutions. This could be an implication that Martian caves should be defined as Special Regions and that further studies should be done on the subject.

  • 342.
    Pellinen-Wannberg, Asta
    et al.
    Umeå universitet, Swedish Institute of Space Physics.
    Murad, Edmond
    AFRL.
    Broasch, Noah
    The Wise Observatory and Tel Aviv University.
    Häggström, Ingemar
    EISCAT Scientific Association, Kiruna.
    Khayrov, Timur
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Julius Maximilians Universität Würzburg.
    The solar cycle effect on the atmosphere as a scintillator for meteor observations2009Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 343.
    Perez, Javier Roldán
    et al.
    Department of Physics, Systems Engineering and Signal Theory, University of Alicante.
    Pomares, J.
    Department of Physics, Systems Engineering and Signal Theory, University of Alicante.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Image-based control of satellite-mounted robot manipulators2016Ingår i: Proceedings of 2016 7th International Conference on Mechanical and Aerospace Engineering, ICMAE 2016: London, United Kingdom, 18-20 July 2016, Piscataway, NU: IEEE Communications Society, 2016, s. 346-351, artikel-id 7549564Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 344.
    Pietranera, Luca
    et al.
    University of Manchester, School of Physics and Astronomy.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Calisse, Paolo
    University of Cardiff, School of Physics and Astronomy.
    Emde, Claudia
    Deutsches Zentrum fuer Luft- und Raumfahrt (DLR) Institut fuer Physik der Atmosphaere, Oberpfaffenhofen.
    Hayton, Darren
    University of Cardiff, School of Physics and Astronomy.
    John, Viju Oommen
    University of Miami, Rosenstiel School of Marine and Atmospheric Sciences, Miami.
    Maffei, Bruno
    University of Manchester, School of Physics and Astronomy.
    Piccirillo, Lucio
    University of Manchester, School of Physics and Astronomy.
    Pisano, Giampaolo
    University of Manchester, School of Physics and Astronomy.
    Savini, Giorgio
    University of Cardiff, School of Physics and Astronomy.
    Sreerekha, T. R.
    Met Office Hadley Centre, Exeter.
    Observing cosmic microwave background polarisation through ice2007Ingår i: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 376, nr 2, s. 645-650Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 345.
    Pomares, Jorge
    et al.
    University of Alicante, Department of Physics, Systems Engineering and Theory of Signal, Sant Vicent del Raspeig.
    Felicetti, Leonard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Perez, Javier
    University of Alicante, Department of Physics, Systems Engineering and Theory of Signal, Sant Vicent del Raspeig.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Institute for Aerospace Studies, University of Toronto.
    Spacecraft visual servoing with adaptive zooming for non-cooperative rendezvous2018Ingår i: 2018 IEEE Aerospace Conference, IEEE Computer Society, 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    The utilization of zooming cameras during a non-cooperative rendezvous in space is investigated in this paper. An image-based controller, utilizing visual servoing techniques usually applied to ground-based robotic systems, is designed for the particular problem of far-to-close approach of a spacecraft to a non-cooperative object. The controller directly utilizes the visual features from image frames of the noncooperative target for computing both attitude and orbital maneuvers concurrently. The additional feature derived from the utilization of the zooming camera gives a greater versatility to the maneuvers if compared with the classic fixed optics approaches. The stability of the proposed controller is proven analytically in the invariant space, and its viability is explored through the application to a realistic space debris removal scenario

  • 346.
    Pomares, Jorge
    et al.
    University of Alicante.
    Felicetti, Leonard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Pérez, Javier
    University of Alicante.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Space Mechatronics group, University of Toronto, Institute for Aerospace Studies.
    Concurrent Image-based Visual Servoing with Adaptive Zooming for Non-cooperative Rendezvous Maneuvers2018Ingår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 61, nr 3, s. 862-878Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 347.
    Pontoni, Angèle
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Evolution of the signal induced by ChemCam on Mars as a function of focus2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

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

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

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

  • 348.
    Pope, Charles
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Calibration and Uncertainty Analysis of a Spacecraft Attitude Determination Test Stand2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

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

  • 349.
    Poppe, A.R.
    et al.
    Space Science Laboratory, University of California, Berkeley.
    Fatemi, Shahab
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Halekas, J.S.
    Space Science Laboratory, University of California, Berkeley.
    Holmström, Mats
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Delory, G.T.
    Space Science Laboratory, University of California, Berkeley.
    ARTEMIS observations of extreme diamagnetic fields in the lunar wake2014Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 41, nr 11, s. 3766-3773Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 350.
    Potrivitu, George-Cristian
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. University Toulouse III Paul Sabatier France.
    Low–voltage External Discharge Plasma Thruster and Hollow Cathodes Plasma Plume Diagnostics Utilising Electrostatic Probes and Retarding Potential Analyser2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

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

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

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

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

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

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

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

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