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  • 201.
    Kindberg, Peter
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Development of a miniature Gridded ion thruster2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 202.
    Kirkwood, Sheila
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Belova, Evgenia G.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Dalin, Peter A.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Mihalikova, Maria
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Mikhaylova, Daria
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Murtagh, Donal P.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Satheesan, K.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Urban, Joachim B.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Wolf, Ingemar
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Response of polar mesosphere summer echoes to geomagnetic disturbances in the Southern and Northern Hemispheres: The importance of nitric oxide2013Inngår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 31, nr 2, s. 333-347Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The relationship between polar mesosphere summer echoes (PMSE) and geomagnetic disturbances (represented by magnetic I K indices) is examined. Calibrated PMSE reflectivities for the period May 2006-February 2012 are used from two 52.0/54.5 MHz radars located in Arctic Sweden (68 N, geomagnetic latitude 65 ) and at two different sites in Queen Maud Land, Antarctica (73/72 S, geomagnetic latitudes 62/63 ). In both the Northern Hemisphere (NH) and the Southern Hemisphere (SH) there is a strong increase in mean PMSE reflectivity between quiet and disturbed geomagnetic conditions. Mean volume reflectivities are slightly lower at the SH locations compared to the NH, but the position of the peak in the lognormal distribution of PMSE reflectivities is close to the same at both NH and SH locations, and varies only slightly with magnetic disturbance level. Differences between the sites, and between geomagnetic disturbance levels, are primarily due to differences in the high-reflectivity tail of the distribution. PMSE occurrence rates are essentially the same at both NH and SH locations during most of the PMSE season when a sufficiently low detection threshold is used so that the peak in the lognormal distribution is included. When the local-time dependence of the PMSE response to geomagnetic disturbance level is considered, the response in the NH is found to be immediate at most local times, but delayed by several hours in the afternoon sector and absent in the early evening. At the SH sites, at lower magnetic latitude, there is a delayed response (by several hours) at almost all local times. At the NH (auroral zone) site, the dependence on magnetic disturbance is highest during evening-to-morning hours. At the SH (sub-auroral) sites the response to magnetic disturbance is weaker but persists throughout the day. While the immediate response to magnetic activity can be qualitatively explained by changes in electron density resulting from energetic particle precipitation, the delayed response can largely be explained by changes in nitric oxide concentrations. Observations of nitric oxide concentration at PMSE heights by the Odin satellite support this hypothesis. Sensitivity to geomagnetic disturbances, including nitric oxide produced during these disturbances, can explain previously reported differences between sites in the auroral zone and those at higher or lower magnetic latitudes. The several-day lifetime of nitric oxide can also explain earlier reported discrepancies between high correlations for average conditions (year-by-year PMSE reflectivities and indices) and low correlations for minute-to-day timescales

  • 203.
    Kloos, Jacob L.
    et al.
    Centre for Research in Earth and Space Sciences, York University, Earth and Space Sciences, Toronto.
    Moores, John E.
    York University, Toronto.
    Lemmon, Mark
    Texas A&M University, College Station.
    Kass, David
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Francis, Raymond
    Jet Propulsion Laboratory/Caltech.
    Juarez, Manuel de la Torre
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Zorzano, María Paz
    Centro de Astrobiología (CSIC-INTA), Madrid.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    The First Martian Year of Cloud Activity from Mars Science Laboratory (Sol 0 - 800)2016Inngår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 57, nr 5, s. 1223-1240Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using images from the Navigation Cameras onboard the Mars Science Laboratory rover Curiosity, atmospheric movies were created to monitor the cloud activity over Gale Crater. Over the course of the first 800 sols of the mission, 133 Zenith Movies and 152 Supra-Horizon Movies were acquired which use a mean frame subtraction technique to observe tenuous cloud movement. Moores et al. (2015a) reported on the first 360 sols of observations, representing LS = 150° to 5°, and found that movies up to LS = 184° showed visible cloud features with good contrast while subsequent movies were relatively featureless. With the extension of the observations to a full Martian year, more pronounced seasonal changes were observed. Within the Zenith Movie data set, clouds are observed primarily during LS = 3° - 170°, when the solar flux is diminished and the aphelion cloud belt is present at equatorial latitudes. Clouds observed in the Supra-Horizon Movie data set also exhibit seasonality, with clouds predominantly observed during LS = 72° - 108°. The seasonal occurrence of clouds detected in the atmospheric movies is well correlated with orbital observations of water-ice clouds at similar times from the MCS and MARCI instruments on the MRO spacecraft. The observed clouds are tenuous and on average only make up a few-hundredths of an optical depth, although more opaque clouds are observed in some of the movies. Additionally, estimates of the phase function calculated using water-ice opacity retrievals from MCS are provided to show how Martian clouds scatter sunlight, and thus provide insight into the types of ice crystals that comprise the clouds.

  • 204.
    Kohlbacher, Anton
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Development of a Novel Relative Localization Sensor2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    By enabling coordinated task execution and movement, robotic swarms can achieve efficient exploration or disaster site management. When utilizing Ultra-wideband (UWB) radio technology for ranging, the proposed relative localization sensor can be made lightweight and relatively indifferent to the ambient environment. Infrastructure dependency is eliminated by making the whole sensor fit on a swarm agent, while allowing for a certain amount of positional error. In this thesis, a novel algorithm is implemented in to constrained hardware and compared to a more traditional trilateration approach. Both algorithms utilize Particle Swarm Optimization (PSO) to be more robust towards noise and achieves similar accuracy, but the proposed algorithm can run up to ten times faster. The antenna array which forms the localization sensor weighs only 56g, and achieves around 0.5m RMSE with a 10Hz update rate. Experiments show that the accuracy can be further improved if the rotational bias observed in the UWB devices are compensated for.

  • 205.
    Korablev, O.
    et al.
    Space Research Institute (IKI)MoscowRussia.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR)GranadaSpain.
    Zorzano, Maria-Paz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Centro de AstrobiologíaINTA-CSICMadridSpain.
    The Atmospheric Chemistry Suite (ACS) of Three Spectrometers for the ExoMars 2016 Trace Gas Orbiter2018Inngår i: Space Science Reviews, ISSN 0038-6308, E-ISSN 1572-9672, Vol. 247, nr 1, artikkel-id 7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [sv]

    The Atmospheric Chemistry Suite (ACS) package is an element of the Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission. ACS consists of three separate infrared spectrometers, sharing common mechanical, electrical, and thermal interfaces. This ensemble of spectrometers has been designed and developed in response to the Trace Gas Orbiter mission objectives that specifically address the requirement of high sensitivity instruments to enable the unambiguous detection of trace gases of potential geophysical or biological interest. For this reason, ACS embarks a set of instruments achieving simultaneously very high accuracy (ppt level), very high resolving power (>10,000) and large spectral coverage (0.7 to 17 μm—the visible to thermal infrared range). The near-infrared (NIR) channel is a versatile spectrometer covering the 0.7–1.6 μm spectral range with a resolving power of ∼20,000. NIR employs the combination of an echelle grating with an AOTF (Acousto-Optical Tunable Filter) as diffraction order selector. This channel will be mainly operated in solar occultation and nadir, and can also perform limb observations. The scientific goals of NIR are the measurements of water vapor, aerosols, and dayside or night side airglows. The mid-infrared (MIR) channel is a cross-dispersion echelle instrument dedicated to solar occultation measurements in the 2.2–4.4 μm range. MIR achieves a resolving power of >50,000. It has been designed to accomplish the most sensitive measurements ever of the trace gases present in the Martian atmosphere. The thermal-infrared channel (TIRVIM) is a 2-inch double pendulum Fourier-transform spectrometer encompassing the spectral range of 1.7–17 μm with apodized resolution varying from 0.2 to 1.3 cm−1. TIRVIM is primarily dedicated to profiling temperature from the surface up to ∼60 km and to monitor aerosol abundance in nadir. TIRVIM also has a limb and solar occultation capability. The technical concept of the instrument, its accommodation on the spacecraft, the optical designs as well as some of the calibrations, and the expected performances for its three channels are described.

  • 206.
    Korablev, Oleg I.
    et al.
    Space Research Institute IKI, Moscow.
    Dobrolensky, Yurii
    Space Research Institute IKI, Moscow.
    Evdokimova, Nadezhda
    Space Research Institute IKI, Moscow.
    Fedorova, Anna A.
    Space Research Institute IKI, Moscow.
    Kuzmin, Ruslan O.
    Space Research Institute IKI, Moscow.
    Mantsevich, Sergei N.
    Space Research Institute IKI, Moscow.
    Cloutis, Edward A.
    The University of Winnipeg.
    Carter, John
    Institut d'Astrophysique Spatiale IAS-CNRS/Université Paris Sud Orsay.
    Poulet, Francois
    Institut d'Astrophysique Spatiale IAS-CNRS/Université Paris Sud Orsay.
    Flahaut, Jessica
    Université Lyon 1, ENS-Lyon, CNRS.
    Griffiths, Andrew
    Mullard Space Science Laboratory, University College London, Dorking.
    Gunn, Matthew
    Department of Physics, Aberystwyth University.
    Schmitz, Nicole
    German Aerospace Center DLR, Köln.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zorzano Mier, Maria-Paz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Rodianov, Daniil S.
    Space Research Institute IKI, Moscow.
    Vago, Jorge L.
    ESA ESTEC, Noordwijk.
    Stepanov, Alexander V.
    Space Research Institute IKI, Moscow.
    Titov, Andrei Yu.
    Space Research Institute IKI, Moscow.
    Vyazovetsky, Nikita A.
    Space Research Institute IKI, Moscow.
    Trokhimovskiy, Alexander Yu.
    Space Research Institute IKI, Moscow.
    Sapgir, Alexander G.
    Space Research Institute IKI, Moscow.
    Kalinnikov, Yurii K.
    Space Research Institute IKI, Moscow.
    Ivanov, Yurii S.
    Main Astronomical Observatory MAO NASU, Kyiv.
    Shapkin, Alexei A.
    Space Research Institute IKI, Moscow.
    Ivanov, Andrei Yu.
    Space Research Institute IKI, Moscow.
    Infrared Spectrometer for ExoMars: A Mast-Mounted Instrument for the Rover2017Inngår i: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 17, nr 6-7, s. 542-564Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    ISEM (Infrared Spectrometer for ExoMars) is a pencil-beam infrared spectrometer that will measure reflected solar radiation in the near infrared range for context assessment of the surface mineralogy in the vicinity of the ExoMars rover. The instrument will be accommodated on the mast of the rover and will be operated together with the panoramic camera (PanCam), high-resolution camera (HRC). ISEM will study the mineralogical and petrographic composition of the martian surface in the vicinity of the rover, and in combination with the other remote sensing instruments, it will aid in the selection of potential targets for close-up investigations and drilling sites. Of particular scientific interest are water-bearing minerals, such as phyllosilicates, sulfates, carbonates, and minerals indicative of astrobiological potential, such as borates, nitrates, and ammonium-bearing minerals. The instrument has an ∼1° field of view and covers the spectral range between 1.15 and 3.30 μm with a spectral resolution varying from 3.3 nm at 1.15 μm to 28 nm at 3.30 μm. The ISEM optical head is mounted on the mast, and its electronics box is located inside the rover's body. The spectrometer uses an acousto-optic tunable filter and a Peltier-cooled InAs detector. The mass of ISEM is 1.74 kg, including the electronics and harness. The science objectives of the experiment, the instrument design, and operational scenarios are described.

  • 207.
    Kottayil, Ajil
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Representation and diurnal variation of upper tropospheric humidity in observations and models2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The role of water vapour is manifold in its climate regulation of the Earth system. Most important of all despite its low concentration, is the role it plays in the upper troposphere. It assumes an important role in its contribution to greenhouse warming by way of its positive feedback effect, amplifying the radiative forcing due to increasing CO2 concentrations. Understanding the variability and distribution is thus important from a climate point of view and critical because the challenges involved in it are far too many. This thesis consists of an introduction and three research articles focusing on the study of upper tropospheric humidity (UTH). The first two articles are on two important sources of UTH data, the radiosondes and satellite data, and the third is associated with climate models, important tools for simulating and reproducing global climate features. The summaries of these three articles are as follows:Radiosondes have been the primary sources for vertical profiles of various atmospheric parameters and are one of the crucial components in numerical weather predictions and satellite validations. However, they are known to have certain issues withmeasurements of humidity in the upper troposphere. The first article highlights the importance of radiosonde humidity corrections by using satellite measurements as the reference. The infrared and microwave measurements from NOAA-17 polar orbiting satellite were used as the reference in this study. Collocated radiosonde measurements from the Atmospheric Radiation Measurement (ARM) campaign were converted into satellite radiances using the ARTS radiative transfer model. The comparisons with satellite measurements were done separately for daytime and nighttime soundings of radiosonde under clear sky conditions. An empirical correction procedure meant to address the mean bias error and solar radiation error was applied to the radiosondes. The empirical correction was found to significantly reduce the dry bias of radiosondes in the upper troposphere. The impact of the correction is prominent over daytime radiosonde measurements on account of the bias removal associated with the solar radiation error.Long term time-series measurements of tropospheric humidity are available from polar orbiting satellites but the measurements from these satellites have been found to be affected by diurnal sampling bias, which is caused by a drift in the orbital height of the satellites, thus changing the local sampling time of the satellites over course of time. This therefore introduces a spurious trend into the time-series data obtained from these satellites. A methodology for the correction of orbital drift error applied on microwave humidity measurements from NOAA and MetOp-A satellites forms the subject of the second article included in this thesis. Climatological diurnal cycles of microwave humidity measurements were obtained from 5 different polar orbiting satellites to infer and thereby correct the diurnal sampling bias in microwave humiditymeasurements. The diurnal cycles were generated separately for the 5 microwave channels. A Monte Carlo error analysis also determines the significance of diurnal amplitudes. The impact of diurnal correction has been evaluated by analyzing the surface channel brightness temperature time-series of NOAA-16 and UTH channel time-series of NOAA-17 satellites. The impact of diurnal correction is greater for the surface channels when compared to the UTH channels due to the larger diurnal cycle amplitudes in the surface channels.Climate models are one of the main tools for the prediction of future climatechange. Most processes associated with water vapour appear in climate models as parameterizations since they are too small-scale or complex to be physically represented in models. Therefore, frequent validation of models against observations is needed to assure their reliability. The third article evaluates the performance of two climate models, in simulating the diurnal cycles of upper tropospheric humidity taking combined microwave humidity measurements from four different satellites as the reference. The comparisons were made over the convective land and oceanic regions over the tropics. The diurnal cycle differences between infrared and microwave observations and the reason for these differences are also analyzed. It is shown that the cloud sensitivity differences in infrared data can shift the diurnal phase relative to microwave data. The models exhibit considerable differences in the diurnal phase and amplitude of UTH as against microwave observations over both land and oceanic regions.

  • 208.
    Kottayil, Ajil
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Satellite and radiosonde measurements of atmospheric humidity2012Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This licentiate thesis is based on two papers which are related to the study ofatmospheric humidity. The first paper mainly focuses on a non linear method forretrieving atmospheric humidity from infrared sounder satellite measurements basedon fuzzy clustering which could potentially improve the retrieval accuracy. The mainaim of this study was to provide a better first guess humidity profile for physicalretrieval algorithms which can further improve retrieval accuracy. This method hasbeen compared against linear and non linear regression retrievals which are the gen-erally used methods to get the first guess profile. The results reveal that the retrievalaccuracy is better for the new method as compared to the conventional methods.Generally, the accuracy of the humidity measurements of radiosonde is poor in theupper troposphere (UT) and is worse for day time measurements due to solar heatingof the humidity sensor. Several methods have been developed to correct the humiditymeasurements of radiosondes in the UT. The second paper presents a detailed analysisof the implications of these corrections and depicts how important they are for satellitevalidation. The corrections have been applied separately for daytime and nighttimeradiosonde measurements and their effects have been quantified by comparing againstthe coinciding satellite measurements in the infrared and microwave spectral rangeused for humidity measurements.

  • 209.
    Kottayil, Ajil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    John, Viju
    Hadley Centre, UK MetOffice, Exeter, UK.
    Evaluating the diurnal cycle of upper tropospheric humidity in two different climate models using satellite observations2016Inngår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The diurnal cycle of upper tropospheric humidity (UTH) is known to be influenced by such processes as convection and the formation of clouds. These processes need to be parameterized in global climate models. In this study, we evaluate the performance of the climate models CAM-5 and GA-3 in simulating the diurnal cycle of UTH by taking combined microwave measurements from four different polar orbiting satellites as the reference. These comparisons were made over two convective land regions in South America and Africa, and over oceanic regions, in the Atlantic, Indian and West Pacific for the month of January, 2007. In addition to the comparison with microwave data, comparisons with the diurnal cycle generated from IR observations from METEOSAT were done for the African and Atlantic regions. We analyzed how the diurnal cycles from IR and microwave instruments differ, and the reason for these differences. The models exhibit considerable discrepancies in diurnal amplitude and phase relative to the microwave observations, and these discrepancies have different magnitudes over land and ocean. We also confirm that the cloud sensitivity difference is the main reason for the observed differences in the diurnal cycles of IR and microwave UTH.

  • 210.
    Kottayil, Ajil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    John, Viju O.
    UK Met Office, Exeter.
    Miloshevich, Larry M.
    Milo Scientific LLC, Lafayette, Colorado.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Holl, Gerrit
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    On the importance of Vaisala RS92 radiosonde humidity corrections for a better agreement between measured and modeled satellite radiances2012Inngår i: Journal of Atmospheric and Oceanic Technology, ISSN 0739-0572, E-ISSN 1520-0426, Vol. 29, nr 2, s. 248-259Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A study has been carried out to assess the importance of radiosonde corrections in improving the agreement between satellite and radiosonde measurements of upper-tropospheric humidity. Infrared [High Resolution Infrared Radiation Sounder (HIRS)-12] and microwave [Advanced Microwave Sounding Unit (AMSU)-18] measurements from the NOAA-17 satellite were used for this purpose. The agreement was assessed by comparing the satellite measurements against simulated measurements using collocated radiosonde profiles of the Atmospheric Radiation Measurement (ARM) Program undertaken at tropical and midlatitude sites. The Atmospheric Radiative Transfer Simulator (ARTS) was used to simulate the satellite radiances. The comparisons have been done under clear-sky conditions, separately for daytime and nighttime soundings. Only Vaisala RS92 radiosonde sensors were used and an empirical correction (EC) was applied to the radiosonde measurements. The EC includes correction for mean calibration bias and for solar radiation error, and it removes radiosonde bias relative to three instruments of known accuracy. For the nighttime dataset, the EC significantly reduces the bias from 0.63 to −0.10 K in AMSU-18 and from 1.26 to 0.35 K in HIRS-12. The EC has an even greater impact on the daytime dataset with a bias reduction from 2.38 to 0.28 K in AMSU-18 and from 2.51 to 0.59 K in HIRS-12. The present study promises a more accurate approach in future radiosonde-based studies in the upper troposphere.

  • 211.
    Kottayil, Ajil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    John, V.O.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Correcting diurnal cycle aliasing in satellite microwave humidity sounder measurements2013Inngår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 118, nr 1, s. 101-113Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Microwave humidity measurements from polar orbiting satellites are affected by diurnal sampling biases which are caused by changes in the local observation time of the satellites. The long term data records available from these satellites thus have spurious trends, which must be corrected. Diurnal cycles of the microwave measurements have been constructed by combining data over the period 2001--2010 from five different satellite platforms (NOAA-15, -16, -17, -18, and MetOpA). This climatological diurnal cycle has been used to deduce and correct the diurnal sampling bias in AMSU-B and MHS measurements. Diurnal amplitudes for channels which are sensitive to surface temperature variations show a sharp land-sea contrast with the amplitudes exceeding 10 K for land regions, but less than one Kelvin for oceanic regions. The humidity channels sensitive to the upper and middle troposphere exhibit a seasonal variation with large diurnal amplitudes over convective land regions (often above 3 K) in comparison to oceanic regions. The diurnal peak times of these channels over land occur in the early mornings. The diurnal sampling bias correction has a greater impact over land regions when compared to oceanic regions due to the large diurnal amplitudes over land. The diurnal cycle of humidity generated as a part of this study could be used to evaluate diurnal cycles in climate models.

  • 212.
    Kottayil, Ajil
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Thapliyal, Pradeep
    Space Applications Centre, ISRO, Ahmedabad.
    Shukla, Munn
    Space Applications Centre, ISRO, Ahmedabad.
    Pal, Pradip
    Space Applications Centre, ISRO, Ahmedabad.
    Joshi, Prakash
    Space Applications Centre, ISRO, Ahmedabad.
    Ranganath, Navalgund
    Space Applications Centre, ISRO, Ahmedabad.
    A new technique for temperature and humidity profile retrieval from infrared sounder observations using adaptive neuro-fuzzy inference system2010Inngår i: IEEE Transactions on Geoscience and Remote Sensing, ISSN 0196-2892, E-ISSN 1558-0644, Vol. 48, nr 4, s. 1650-1659Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Accuracy of the atmospheric profiles of temperature and humidity, retrieved from infrared sounder observations using physical retrieval algorithm, depend primarily on the quality of the first guess profiles. In the past, forecasts from the numerical weather prediction models were extensively used as the first guess. During past few years, the first guess for physical retrieval is being estimated using regression techniques from sounder observations. In the present study, a new non-linear technique has been described to improve the first guess using simulated infrared brightness temperatures for GOES-12 Sounder channels. The present technique uses fuzzy logic and data clustering to establish a relationship between simulated sounder observations and atmospheric profiles. This relationship is further strengthened using Adaptive Neuro-Fuzzy Inference System (ANFIS) by fine-tuning the existing fuzzy rule base. The results of ANFIS retrieval have been compared with the non-linear (polynomial) regression retrieval. It has been found that ANFIS is more robust and shows remarkable improvement as it reduces RMS error by 20% in humidity profiles retrieval compared to the non-linear regression technique. In addition, it has been shown that the ANFIS technique has an added advantage of its global application without any need for training data classification that is required in the regression techniques.

  • 213.
    Kudaravalli, Venkata Narayana Chowdary
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Design and fabrication of test-bed for testing attitude determination of spin stablilized spacecraft.2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

     Attitude determination for a spin stabilized satellite is calibrated. A mock spacecraft and a spin simulation test bed are designed and developed. Spin simulation testbed which provides position data is used to acquire true position data. The data from the simulator test bed is used as reference for the sensor data to estimate the error in position of sensor data. Two vector method attitude solutions are used here for attaining the estimated position. Two vectors used for attitude determination are magnetic field vector and sun sensor vector. Calibration of accuracy for sensors is main goal, which is attained by calculating error by comparing the estimated position with true position.

  • 214.
    Kuhn, Thomas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Damoah, R.
    Department of Earth and Environmental Sciences, University of Waterloo.
    Bacak, A.
    School of Earth, Atmospheric and Environmental Sciences, University of Manchester.
    Sloan, J.J.
    Department of Earth and Environmental Sciences, University of Waterloo.
    Characterising aerosol transport into the Canadian high Arctic using aerosol mass spectrometry and Lagrangian modelling2010Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 10, nr 21, s. 10489-10502Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report the analysis of measurements made using an aerosol mass spectrometer (AMS; Aerodyne Research Inc.) that was installed in the Polar Environment Atmospheric Research Laboratory (PEARL) in summer 2006. PEARL is located in the Canadian high Arctic at 610 m above sea level on Ellesmere Island (80° N 86° W). PEARL is unique for its remote location in the Arctic and because most of the time it is situated within the free troposphere. It is, therefore, well suited as a receptor site to study the long-range tropospheric transport of pollutants into the Arctic. Some information about the successful year-round operation of an AMS at a high Arctic site such as PEARL will be reported here, together with design considerations for reliable sampling under harsh low-temperature conditions. Computational fluid dynamics calculations were made to ensure that sample integrity was maintained while sampling air at temperatures that average 40 °C in the winter and can be as low as 55 °C. Selected AMS measurements of aerosol mass concentration, size and chemical composition recorded during the months of August, September and October 2006 will be reported. The air temperature was raised to about 20 deg;C during sampling, but the short residence time in the inlet system (∼25 s) ensured that less than 10% of semivolatiles such as ammonium nitrate were lost. During this period, sulfate was, at most times, the predominant aerosol component with on average 0.115 μg-3 (detection limit 0.003mg-3). The second most abundant component was undifferentiated organic aerosol, with on average 0.11 Î1/4g mg3 (detection limit 0.04 I1/4g mg3). The nitrate component, which averaged 0.007 mg-3, was above its detection limit (0.002 Î1/4g mg3), whereas the ammonium ion had an apparent average concentration of 0.02 g mg-3, which was approximately equal to its detection limit. A few episodes, having increased mass concentrations and lasting from several hours to several days, are apparent in the data. These were investigated further using a statistical analysis to determine their common characteristics. High correlations among some of the components arriving during the short-term episodes provide evidence for common sources. Lagrangian methods were also used to identify the source regions for some of the episodes. In all cases, these coincided with the arrival of air that had contacted the surface at latitudes below about 60° N. Most of these lower-latitude footprints were on land, but sulfate emissions from shipping in the Atlantic were also detected. The Lagrangian results demonstrate that there is direct transport of polluted air into the high Arctic (up to 80° N) from latitudes down to 40° N on a time scale of 2-3 weeks. The polluted air originates in a wide variety of industrial, resource extraction and petroleum-related activity as well as from large population centres

  • 215.
    Kuhn, Thomas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Earle, M.E.
    Department of Earth and Environmental Sciences, University of Waterloo.
    Khalizov, A.F.
    Department of Earth and Environmental Sciences, University of Waterloo.
    Sloan, J.J.
    Department of Earth and Environmental Sciences, University of Waterloo.
    Size dependence of volume and surface nucleation rates for homogeneous freezing of supercooled water droplets2011Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 11, nr 6, s. 2853-2861Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The relative roles of volume and surface nucleation were investigated for the homogeneous freezing of pure water droplets. Experiments were carried out in a cryogenic laminar aerosol flow tube using supercooled water aerosols with maximum volume densities at radii between 1 and 3 Î1/4m. Temperature-and size-dependent values of volume-and surface-based homogeneous nucleation rates between 234.8 and 236.2 K were derived using a microphysical model and aerosol phase compositions and size distributions determined from infrared extinction measurements in the flow tube. The results show that the contribution from nucleation at the droplet surface increases with decreasing droplet radius and dominates over nucleation in the bulk droplet volume for droplets with radii smaller than approximately 5 Î1/4m. This is interpreted in terms of a lowered free energy of ice germ formation in the surface-based process. The implications of surface nucleation for the parameterization of homogeneous ice nucleation in numerical models are considered

  • 216.
    Kuhn, Thomas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Grishin, Igor
    Department of Earth and Environmental Sciences, University of Waterloo.
    Sloan, James J.
    Department of Earth and Environmental Sciences, University of Waterloo.
    Improved imaging and image analysis system for application to measurement of small ice crystals2012Inngår i: Journal of Atmospheric and Oceanic Technology, ISSN 0739-0572, E-ISSN 1520-0426, Vol. 29, nr 12, s. 1811-1824Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Accurate knowledge of ice particle size and shape distribution is required for understanding of atmospheric microphysical processes. While larger ice particles are easily measured with a variety of sensors, the measurement of small ice particles with sizes down to a few micrometers remains challenging. Here the authors report the development of a system that measures the size and shape of small ice particles using a novel combination of high-resolution imaging and high-speed automated image classification. The optical system has a pixel resolution of 0.2 μm and a resolving power of approximately 1 μm. This imaging instrument is integrated into a cryogenic flow tube that allows precise control of experimental conditions.This study also describes an automated method for the high-speed analysis of high-resolution particle images. Each particle is located in the image using a Sobel edge detector, the border is vectorized, and a polygon representing the border is found. The vertices of this polygon are expressed in complex coordinates, and an analytic implementation of Fourier shape descriptors is used for piecewise integration along the edges of the polygon.The authors demonstrate the capabilities of this system in a study of the early-stage growth of ice particles, which are grown for approximately 1 min at fixed temperature and saturated water vapor concentrations in the cryogenic flowtube. Ice particle shapes and size distributions are reported and compared with habit diagrams found in the literature. The capability of the shape recognition system is verified by comparison with manual classification.

  • 217.
    Kuhn, Thomas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Gultepe, Ismail
    Cloud Physics and Severe Weather Research Section, Environment Canada.
    Ice Fog and Light Snow Measurements Using a High-Resolution Camera System2016Inngår i: Pure and Applied Geophysics, ISSN 0033-4553, E-ISSN 1420-9136, Vol. 173, nr 9, s. 3049-3064Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ice fog, diamond dust, and light snow usually form over extremely cold weather conditions, and they affect both visibility and Earth’s radiative energy budget. Prediction of these hydrometeors using models is difficult because of limited knowledge of the microphysical properties at the small size ranges due to measurement issues. These phenomena need to be better represented in forecast and climate models; therefore, in addition to remote sensing accurate measurements using ground-based instrumentation are required. An imaging instrument, aimed at measuring ice fog and light snow particles, has been built and is presented here. The ice crystal imaging (ICI) probe samples ice particles into a vertical, tapered inlet with an inlet flow rate of 11 L min−1. A laser beam across the vertical air flow containing the ice crystals allows for their detection by a photodetector collecting the scattered light. Detected particles are then imaged with high optical resolution. An illuminating LED flash and image capturing are triggered by the photodetector. In this work, ICI measurements collected during the fog remote sensing and modeling (FRAM) project, which took place during Winter of 2010–2011 in Yellowknife, NWT, Canada, are summarized and challenges related to measuring small ice particles are described. The majority of ice particles during the 2-month-long campaign had sizes between 300 and 800 μm. During ice fog events the size distribution measured had a lower mode diameter of 300 μm compared to the overall campaign average with mode at 500 μm.

  • 218.
    Kuhn, Thomas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Heymsfield, Andrew J.
    National Center for Atmospheric Research, Boulder, Colorado.
    In Situ Balloon-Borne Ice Particle Imaging in High-Latitude Cirrus2016Inngår i: Pure and Applied Geophysics, ISSN 0033-4553, E-ISSN 1420-9136, Vol. 173, nr 9, s. 3065-3084Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cirrus clouds reflect incoming solar radiation, creating a cooling effect. At the same time, these clouds absorb the infrared radiation from the Earth, creating a greenhouse effect. The net effect, crucial for radiative transfer, depends on the cirrus microphysical properties, such as particle size distributions and particle shapes. Knowledge of these cloud properties is also needed for calibrating and validating passive and active remote sensors. Ice particles of sizes below 100 µm are inherently difficult to measure with aircraft-mounted probes due to issues with resolution, sizing, and size-dependent sampling volume. Furthermore, artefacts are produced by shattering of particles on the leading surfaces of the aircraft probes when particles several hundred microns or larger are present. Here, we report on a series of balloon-borne in situ measurements that were carried out at a high-latitude location, Kiruna in northern Sweden (68N 21E). The method used here avoids these issues experienced with the aircraft probes. Furthermore, with a balloon-borne instrument, data are collected as vertical profiles, more useful for calibrating or evaluating remote sensing measurements than data collected along horizontal traverses. Particles are collected on an oil-coated film at a sampling speed given directly by the ascending rate of the balloon, 4 m s−1. The collecting film is advanced uniformly inside the instrument so that an always unused section of the film is exposed to ice particles, which are measured by imaging shortly after sampling. The high optical resolution of about 4 µm together with a pixel resolution of 1.65 µm allows particle detection at sizes of 10 µm and larger. For particles that are 20 µm (12 pixel) in size or larger, the shape can be recognized. The sampling volume, 130 cm3 s−1, is well defined and independent of particle size. With the encountered number concentrations of between 4 and 400 L−1, this required about 90- to 4-s sampling times to determine particle size distributions of cloud layers. Depending on how ice particles vary through the cloud, several layers per cloud with relatively uniform properties have been analysed. Preliminary results of the balloon campaign, targeting upper tropospheric, cold cirrus clouds, are presented here. Ice particles in these clouds were predominantly very small, with a median size of measured particles of around 50 µm and about 80 % of all particles below 100 µm in size. The properties of the particle size distributions at temperatures between −36 and −67 °C have been studied, as well as particle areas, extinction coefficients, and their shapes (area ratios). Gamma and log-normal distribution functions could be fitted to all measured particle size distributions achieving very good correlation with coefficients R of up to 0.95. Each distribution features one distinct mode. With decreasing temperature, the mode diameter decreases exponentially, whereas the total number concentration increases by two orders of magnitude with decreasing temperature in the same range. The high concentrations at cold temperatures also caused larger extinction coefficients, directly determined from cross-sectional areas of single ice particles, than at warmer temperatures. The mass of particles has been estimated from area and size. Ice water content (IWC) and effective diameters are then determined from the data. IWC did vary only between 1 × 10−3 and 5 × 10−3 g m−3 at temperatures below −40 °C and did not show a clear temperature trend. These measurements are part of an ongoing study.

  • 219.
    Kuhn, Thomas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Heymsfield, Andrew J.
    NCAR, Boulder, Colorado.
    Vertical distributions of small cirrus cloud particles from balloon-borne in-situ measurements: Oral presentation2014Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Thin and cold ice clouds are important for the radiative budget, yet they are difficult to measure. They are often high in the troposphere where they reflect incoming sunlight, creating a cooling effect. At the same time these clouds absorb longwave radiation from Earth, creating a greenhouse effect. Knowledge of the net effect is crucial and depends on the microphysical properties of the clouds, which at these altitudes and temperatures are often composed of small particles of 100 μm or less in size. Most of in-situ data reported in the literature have been sampled with aircraft probes, which have known issues with such small particles due to sizing and shattering prob- lems, in addition to having also a small and size-dependent sampling volume for these particles.A series of balloon-borne in-situ measurements, currently being carried out from a high-latitude location in north- ern Sweden (Kiruna, 68N 21E), combined with previous balloon-borne measurements from other locations, are used to study properties of small cloud ice particles at a variety of temperatures and altitudes. Among other prop- erties, size distributions and concentrations are analysed as a function of height within the cloud layer. Results are compared to literature data from aircraft probes to shed more light on the uncertainties related to the difficulties of these probes in measuring small particles.

  • 220.
    Kuhn, Thomas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Heymsfield, Andrew J.
    National Center for Atmospheric Research, Boulder, Colorado.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Balloon-Borne Measurements of Ice Particle Shape and Ice Water Content in the Upper Troposphere over Northern Sweden2013Inngår i: 21st ESA Symposium: ESA Symposium on European Rocket and Balloon Programmes and Related Research 2013, 9–13 June 2013, Noordwijk: European Space Agency, ESA , 2013, s. 93-97Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Ice clouds play an important role in the energy budget of the atmosphere. They are at high altitudes, absorb long-wave radiation from below and, as they are cold, emit little infrared radiation. This greenhouse effect warms the Earth-atmosphere system. On the other hand, ice clouds have a cooling effect by reflecting incoming solar short wave radiation. The net effect is crucial for the atmosphere, but will depend highly on the cloud’s horizontal extent, vertical position, ice water content (IWC), and ice particle microphysical properties such as size and shape. Targeting these upper-tropospheric, cold ice clouds, a series of in-situ balloon-borne experiments has been started at Kiruna, Sweden, which is located at 68°N. Fewer mea- surements exist at these high latitudes compared to mid- or tropical latitudes. Also temperatures in the upper troposphere can be around -60 °C, a temperature range under-represented in available in-situ data. Experiments are launched from Esrange Space Center. Ice particles are collected with a balloon-borne replicator and also imaged in-situ, and measurements are complemented by a radiosonde added to the instrument. Particle shape and size as well as IWC are determined from the replicas and images. The data are analysed to reveal relationships between IWC and other measurements such as temperature and volume extinction coefficient. Such relationships can be used for validation and improvement of satellite retrievals of IWC from, for example, thin cirrus measurements with satellite-borne lidar, such as on the future EarthCARE mission.

  • 221.
    Kuhn, Thomas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Heymsfield, Andrew J.
    National Center for Atmospheric Research, Boulder, Colorado.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    In-situ ice particle measurements over northern Sweden2012Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    ce clouds play an important role in the energy budget of the atmosphere. They are at high altitudes, absorb longwave radiation from below and, as they are cold, emit little infrared radiation. This greenhouse effect warms the Earth-atmosphere system. On the other hand, ice clouds have a cooling effect by reflecting incoming solar short wave radiation. The net effect is crucial for the atmosphere, but will depend highly on the cloud’s horizontal extent, vertical position, ice water content (IWC), and ice particle microphysical properties such as size and shape. A series of in-situ balloon measurements has been started at Kiruna, Sweden, which is located at 68°N. Fewer in- situ ice cloud measurements exist at these high latitudes compared to mid- or tropical latitudes. Also temperatures in the upper troposphere can be around -60 °C, a temperature range under-represented in available in-situ data. Ice particles are collected with a balloon-borne replicator launched from Esrange Space Center (near Kiruna, Sweden). Measurements are complemented by a radiosonde added to the instrument. The shape and size as well as IWC are determined from the replicas. The data are analyzed to reveal relationships between IWC and other measurements such as temperature and volume extinction coefficient. Such relationships can be used for validation and improvement of satellite retrievals of IWC from, for example, thin cirrus measurements with satellite-borne lidar.

  • 222.
    Kuhn, Thomas
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Wolf, Veronika
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Völger, Peter
    The Swedish Institute of Space Physics (IRF).
    Stanev, Marin
    Stockholm University, Department of Meteorology (MISU).
    Gumbel, Jörg
    Stockholm University, Department of Meteorology (MISU).
    Comparison of In-Situ Balloon-Borne and Lidar Measurement of Cirrus Clouds2017Inngår i: Proceedings of the 23rd ESA Symposium on European Rocket and Balloon Programmes and Related Research, Noordwijk, The Netherlands, 2017, artikkel-id A-091kuhnKonferansepaper (Annet vitenskapelig)
    Abstract [en]

    A series of in-situ balloon-borne experiments con- ducted at Kiruna, Sweden (68°N), is studying upper- tropospheric, cold ice clouds in arctic latitudes. Ex- periments are launched from Esrange Space Center and collect ice particles with an in-situ imaging instrument. One of the aims with these measurements is to improve satellite remote sensing of cold ice clouds. Such clouds can be observed by lidar. Therefore, when possible, concurrent ground-based lidar measurements have been carried out with two available lidar systems to accom- pany the balloon-borne measurements. The Esrange lidar is located at Esrange Space Center, approximately 500 m from the in-situ launch site on the balloon pad; the IRF lidar is located about 29 km to the west of Esrange Space Center (operated by the Swedish Institute of Space Physics, IRF). Here we present results from these lidar measurements and compare them to ice particle proper- ties determined during the in-situ measurements. 

  • 223.
    Kumar, Rajesh
    et al.
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Singh, Shaktiman
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Kumar, Ramesh
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Singh, Atar
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Bhardwaj, Anshuman
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Sam, Lydia
    Department of Environmental Science, Sharda University, Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Randhawa, Surjeet Singh
    State Council for Science, Technology. & Environment, Shimla.
    Gupta, Akhilesh
    Department of Science and Technology, Technology Bhavan, New Delhi.
    Development of a Glacio-hydrological Model for Discharge and Mass Balance Reconstruction2016Inngår i: Water resources management, ISSN 0920-4741, E-ISSN 1573-1650, Vol. 30, nr 10, s. 3475-3492Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The reconstruction of glacio-hydrological records for the data deficient Himalayan catchments is needed in order to study the past and future water availability. The study provides outcomes of a glacio-hydrological model based on the degree-day approach. The model simulates the discharge and mass balance for glacierised Shaune Garang catchment. The degree-day factors for different land covers, used in the model, were estimated using daily stake measurements on Shaune Garang glacier and they were found to be varying between 2.6 ± 0.4 and 9.3 ± 0.3 mm °C−1day−1. The model is validated using observed discharge during ablation season of 2014 with coefficient of determination (R2) 0.90 and root mean square error (RMSE) 1.05 m3 sec−1. The model is used to simulate discharge from 1985 to 2008 and mass balance from 2001 to 2008. The model results show significant contribution of seasonal snow and ice melt in total discharge of the catchment, especially during summer. We observe the maximum discharge in July having maximum contribution from snow and ice melt. The annual melt season discharge shows following a decreasing trend in the simulation period. The reconstructed mass balance shows mass loss of 0.89 m we per year between 2001 and 2008 with slight mass gain during 2000/01 and 2004/05 hydrological years.

  • 224.
    Kunicka, Beata Iwona
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Spacecraft dynamic analysis and correlation with test results: Shock environment analysis of LISA Pathfinder at VESTA test bed2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The particular study case in this thesis is the shock test performed on the LISA Pathfinder satellite conducted in a laboratory environment on a dedicated test bed: Vega Shock Test Apparatus (VESTA). This test is considered fully representative to study shock levels produced by fairing jettisoning event at Vega Launcher Vehicle, which induces high shock loads towards the satellite.

    In the frame of this thesis, some transient response analyses have been conducted in MSC Nastran, and a shock simulation tool for the VESTA test configuration has been developed. The simulation tool is based on Nastran Direct Transient Response Analysis solver (SOL 109), and is representative of the upper composite of Vega with the LISA Pathfinder coupled to it. Post-processing routines of transient response signals were conducted in Dynaworks which served to calculate Shock Response Spectra (SRS).

    The simulation tool is a model of forcing function parameters for transient analysis which adequately correlates with the shock real test data, in order to understand how the effect of shock generated by the launcher is seen in the satellite and its sub-systems. Since available computation resources are limited the parameters for analysis were optimised for computation time, file size, memory capacity,  and model complexity. The forcing function represents a release of the HSS clamp band which is responsible for fairing jettisoning, thus the parameters which were studied are mostly concerning the modelling of this event. Among many investigated, those which visibly improved SRS correlation are radial forcing function shape, implementation of axial impulse, clamp band loading geometry and refined loading scheme. Integration time step duration and analysis duration were also studied and found to improve correlation.  From each analysis, the qualifying shock environment was then derived by linear scaling in proportion of the applied preload, and considering a qualification margin of 3dB.

    Consecutive tracking of structural responses along shock propagation path exposed gradual changes in responses pattern and revealed an important property that a breathing mode (n = 0) at the base of a conical Adapter translates into an axial input to the spacecraft. The parametrisation itself was based on responses registered at interfaces located in near-field (where the clamp band is located and forcing function is applied) and medium-field with respect to the shock event location. Following shock propagation path, the final step was the analysis of shock responses inside the satellite located in a far-field region, which still revealed a very good correlation of results. Thus, it can be said that parametrisation process was adequate, and the developed shock simulation tool can be qualified. However, due to the nature of shock, the tool cannot fully replace VESTA laboratory test, but can support shock assessment process and preparation to such test.

    In the last part of the thesis, the implementation of some finite element model improvements is investigated. Majority of the panels in spacecraft interior exhibited shock over-prediction due to finite element model limitation. Equipment units modelled as lump masses rigidly attached with RBE2 elements to the panel surface are a source of such local over-predictions. Thus, some of the units were remodelled and transient responses were reinvestigated. It was found that remodelling with either solid elements, or lump mass connected to RBE3 element and reinforced by RBE2 element, can significantly improve local transient responses. This conclusion is in line with conclusions found in ECSS Shock Handbook.

  • 225.
    Lahoz, William A.
    et al.
    University of Reading, Data assimililation research centre.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Legras, Bernard
    Laboratoire de Météorologie Dynamique, Paris.
    The COST 723 Action2007Inngår i: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 133, nr S2, s. 99-108Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An overview is provided of the COST 723 Action, Data Exploitation and Modelling of the Upper Troposphere and Lower Stratosphere. The three working groups are introduced and a summary of Action activities within them is provided. The achievements of the Action are: three international workshops; the LAUTLOS humidity measurement campaign; dedicated meetings to discuss the quality of upper troposphere/lower stratosphere ozone and humidity measurements; two journal special issues; more than 90 papers in the peer-reviewed literature; one international summer school; and a successor COST Action which builds on COST 723. The recommendations made are: for COST to continue to support the short-term scientific missions instrument, as they are perceived to be value for money; to encourage the use of COST money to increase links between COST Actions and other scientific communities; and for the COST secretariat to recommend that Actions consider a summer school instead of a final workshop or meeting.

  • 226.
    Lanza, Nina L.
    et al.
    Los Alamos National Laboratory.
    Wiens, Roger C.
    Los Alamos National Laboratory, Space Remote Sensing, Los Alamos National Laboratory, Los Alamos, International Space and Response Division, Los Alamos National Laboratory.
    Arvidson, Ray E.
    Washington University, St. Louis.
    Clark, Benton C.
    Space Science Institute, Boulder, Colorado, Space Science Institute.
    Fischer, W.W.
    California Institute of Technology, Pasadena.
    Gellert, Ralf
    University of Guelph, Ontario, University of Guelph, Department of Physics, University of Guelph, Ontario.
    Grotzinger, John P.
    California Institute of Technology, Pasadena, Division of Geological and Planetary Sciences, California Institute of Technology, Caltech, Pasadena, Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Hurowitz, J.A.
    Department of Geosciences, Stony Brook University, Stony Brook University, NY, Department of Geosciences, State University of New York, Stony Brook.
    McLennan, S.M.
    Department of Geosciences, Stony Brook University, Stony Brook University, NY, Department of Geosciences, State University of New York, Stony Brook, The State University of New York, Stony Brook.
    Morris, R.V.
    NASA Johnson Space Center, NASA Johnson Space Center, Houston, Astromaterials Research and Exploration Science Directorate, NASA Johnson Space Center, Houston.
    Rice, M.S.
    California Institute of Technology, Pasadena, Division of Geological and Planetary Sciences, California Institute of Technology.
    III, J.F. Bell
    Arizona State University, School of Earth and Space Exploration, Arizona State University, School of Earth and Space Exploration, Arizona State University, Tempe.
    Berger, Jeff A.
    University of Western Ontario, London.
    Blaney, Diana L.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena, Jet Propulsion Laboratory, Pasadena, Kalifornien.
    Bridges, Nathan T.
    Johns Hopkins University Applied Physics Laboratory, Laurel, Applied Physics Laboratory, Laurel, Maryland.
    Calef, Fred
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena, Jet Propulsion Laboratory.
    Campbell, J.L.
    Department of Physics, University of Guelph, Ontario, University of Guelph, Ontario.
    Clegg, S.M.
    Los Alamos National Laboratory, Chemistry Division, Los Alamos National Laboratory.
    Cousin, A.
    Los Alamos National Laboratory, Chemistry Division, Los Alamos National Laboratory.
    Edgett, Kenneth S.
    Malin Space Science Systems, San Diego, Malin Space Science Systems.
    Fabre, Cécile
    Université de Lorraine, Nancy.
    Fisk, M.R.
    Oregon State University, Corvallis.
    Forni, Olivier
    IRAP/CNRS, Institut de Recherche en Astrophysique et Planetologie, Toulouse, Université de Toulouse, UPS-OMP, IRAP, Institut de Recherche en Astophysique et Planetologie (IRAP), Universite' Paul Sabatier, Toulouse, IRAP, CNRS/UPS, Toulouse.
    Frydenvang, J.
    Niels Bohr Institute, University of Copenhagen.
    Hardy, K.R.
    U.S. Naval Academy, Annapolis.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zorzano Mier, Maria-Paz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater, Mars2016Inngår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, nr 14, s. 7398-7407Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Curiosity rover observed high Mn abundances (>25wt % MnO) in fracture-filling materials that crosscut sandstones in the Kimberley region of Gale crater, Mars. The correlation between Mn and trace metal abundances plus the lack of correlation between Mn and elements such as S, Cl, and C, reveals that these deposits are Mn oxides rather than evaporites or other salts. On Earth, environments that concentrate Mn and deposit Mn minerals require water and highly oxidizing conditions; hence, these findings suggest that similar processes occurred on Mars. Based on the strong association between Mn-oxide deposition and evolving atmospheric dioxygen levels on Earth, the presence of these Mn phases on Mars suggests that there was more abundant molecular oxygen within the atmosphere and some groundwaters of ancient Mars than in the present day

  • 227.
    Lanza, N.L.
    et al.
    Los Alamos National Laboratory.
    Wiens, R.C.
    Los Alamos National Laboratory.
    Arvidson, R.E.
    Washington University, St. Louis.
    Clark, B.C.
    Space Science Institute, Boulder, Colorado.
    Fischer, W.W.
    California Institute of Technology, Pasadena.
    Gellert, R.
    University of Guelph, Ontario.
    Grotzinger, J.P.
    California Institute of Technology, Pasadena.
    Hurowitz, J.A.
    Stony Brook University, NY.
    McLennan, S.M.
    Stony Brook University, NY.
    Morris, R.V.
    NASA Johnson Space Center, Houston.
    Rice, M.S.
    Western Washington University, Bellingham.
    III, J.F. Bell
    Arizona State University.
    Berger, J.A.
    University of Western Ontario, London.
    Blaney, D.L.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Blank, J.G.
    NASA Ames, Blue Marble Space Institute of Science, Seattle.
    Bridges, N.T.
    Johns Hopkins University Applied Physics Laboratory, Laurel.
    III, F. Calef
    Jet Propulsion Laboratory.
    Campbell, J.L.
    University of Guelph, Ontario.
    Clegg, S.M.
    Los Alamos National Laboratory.
    Cousin, A.
    Los Alamos National Laboratory.
    Edgett, K.S.
    Malin Space Science Systems.
    Fabre, C.
    Université de Lorraine, Nancy.
    Fisk, M.R.
    Oregon State University, Corvallis.
    Forni, O.
    Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Frydenvang, J.
    Niels Bohr Institute, University of Copenhagen.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Instituto Andaluz de Cienccias de la Tierra (CSIC-UGR), Grenada.
    Zorzano, M.-P.
    Instituto Nacional de Técnica Aeroespacial, Madrid.
    Oxidation of manganese at Kimberley, Gale Crater: More free oxygen in Mars’ past?2015Konferansepaper (Fagfellevurdert)
  • 228.
    Larsson, Richard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A note on modelling of the oxygen spectral cross-section in the Atmospheric Radiative Transfer Simulator – Zeeman effect combined with line mixing in the Earth’s atmosphere2014Inngår i: International Journal of Remote Sensing, ISSN 0143-1161, E-ISSN 1366-5901, Vol. 35, nr 15, s. 5845-5853Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new module to the Atmospheric Radiative Transfer Simulator is presented that models the strong oxygen spectral band at 60 GHz. The module handles the line mixing effect and works with or without additionally calculating the Zeeman effect. It is shown how the module may be internally reduced to calculations of the Zeeman effect at higher altitudes, and to calculations of the line mixing effect at lower altitudes. The article ends with a short discussion on what is being done to validate the module, and what may be done to refine the theoretical description of line mixing in the simulator.

  • 229.
    Larsson, Richard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Modeling the Zeeman Effect in Planetary Atmospheric Radiative Transfer2014Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    There are special effects in spectroscopy that must be considered in order to fullyexplain how molecular oxygen interacts with radiation in planetary atmospheres.One of these, the Zeeman effect, is described in this thesis. The Zeeman effect is the theory by which energy levels of atoms and molecules are altered by magnetism, and it causes both polarization and line shape to change. The first publication attached to this thesis, Paper I, details the technical and practical implementation of the Zeeman effect in a radiative transfer model. One potential use of magnetically altered spectroscopy is to remotely measure magnetism. Paper II discuss a method for such measurements on weakly magnetized planets by measuring the polarization caused by the Zeeman effect. The article brings up Mars as one potential candidate to utilize the method. To introduce the articles properly, the thesis starts with a shortdescription of the underlying basic theory for radiative transfer and spectroscopy.After the theory chapter, a short description of input necessary to utilize the theory on operational and experimental platforms is presented.

  • 230.
    Larsson, Richard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Modeling the Zeeman Effect in Planetary Radiative Transfer and Applications2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Remote sensing is about retrieving distant physical properties from locally observed radiation. The first step to remote sensing is to describe, or model, the radiative transfer. Without locating the origin of the observed radiation, and without proper interpretation of what it represents, understanding and utilizing instrumental results are nearly impossible. The focus of my thesis is on how radiation interacts with a weakly magnetized medium by means of the Zeeman effect. One molecule of particular interest affected by the Zeeman effect is the oxygen molecule. The thesis work started by an implementation of a module for the Zeeman effect in an existingradiative transfer model. Later works has applied this module to Earth and Mars radiative transfer.The high relative concentration of the oxygen molecule in Earth’s atmosphere, and the fact that the molecule interacts with sub-millimeter radiation, has made it a prime target for temperature retrievals using both ground- and satellite-based radiometers. The Zeeman effect is important for molecular oxygen at mesospheric altitudes on Earth, where the geometry of the magnetic field and of the observation influence the polarized absorption of radiation. Simulations of ground-based measurements by a radiometer in Bern, Switzerland, have the Zeeman module reproduce the dependency on observational geometry for the local magnetic field, partly validating the module. Simulations of satellite measurements comparing the Zeeman module to a fast, parameterized, implementation of the Zeeman effect for numerical weather predictions also indicates that the module works. There are small discrepancies between the two models but both are close to the satellite measurements given the noise of these measurements. Work to move beyond simulation space and analyze these satellite measurements to find the atmospheric temperatures at high altitudes also show promising results.Besides Earth applications, the module has been used for Mars conditions, where only trace amounts of molecular oxygen is available. Mars does not have a global magnetic field but instead have several magnetic sources scattered throughout its crust. This gives a magnetic field that is significantly weaker than on Earth and with much more structures. It is possible to utilize the Zeeman effect on molecular oxygen to measure the magnetic field of Mars. The last part of this thesis work suggests a measurement scheme for a satellite capable of retrieving the horizontal components of the Martian crustal magnetic field. It shows the expected errors associated with such a measurement scheme.

  • 231.
    Larsson, Richard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Mendrok, Jana
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A treatment of the Zeeman effect using Stokes formalism and its implementation in the Atmospheric Radiative Transfer Simulator ARTS2014Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 133, s. 445-453Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article presents the practical theory that was used to implement the Zeeman effect using Stokes formalism in the Atmospheric Radiative Transfer Simulator ARTS. ARTS now treats the Zeeman effect in a general manner for several gas species for all polarizations and takes into account variations in both magnetic and atmospheric fields along a full 3D geometry. We present how Zeeman splitting affects polarization in radiative transfer simulations and find that the effect may be large in Earth settings for polarized receivers in limb observing geometry. We find that not taking a spatially varying magnetic field into account can result in absolute errors in the measurement vector of at least 10 K in Earth magnetic field settings. The article also presents qualitative tests for O2 lines against previous models (61.15 GHz line) and satellite data from Odin-SMR (487.25 GHz line), and the overall consistency between previous models, satellite data, and the new ARTS Zeeman module seems encouraging.

  • 232.
    Larsson, Richard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    McKay, Christopher
    NASA Ames Research Center.
    Timescale for oceans in the past of Titan2013Inngår i: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, s. 22-24Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We estimate the past extent of liquid on the surface of Titan as a function of time assuming the current rate of destruction of methane and no sources or subsurface sinks. As methane increases for increasing past time the polar lakes expand equatorward. We use a spherical harmonics model for the surface topography to compute the fraction of the surface covered as the methane inventory increases. We find that substantial parts of the equator would have been flooded by a polar ocean 300 million years ago and that the equator would have been connected to a global ocean 600 million years ago. This provides one possible explanation for the fluvial features seen at the equator on Titan.

  • 233.
    Larsson, Richard
    et al.
    National Institute of Information and Communications Technology, Tokyo, Japan.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. IRV.
    Eriksson, Patrick
    Chalmers University of Technology, Göteborg.
    Mendrok, Jana
    Chalmers University of Technology, Göteborg.
    Kasai, Yasuko
    National Institute of Information and Communications Technology, Tokyo, Japan.
    Buehler, Stefan A.
    University of Hamburg.
    Diéval, Catherine
    Lancaster University.
    Brain, David
    University of Colorado, Boulder.
    Hartogh, Paul
    Max planck Institute for Solar System Research, Göttingen, Germany .
    Martian magnetism with orbiting sub-millimeter sensor: simulated retrieval system2017Inngår i: Geoscientific Instrumentation, Methods and Data Systems, ISSN 2193-0856, E-ISSN 2193-0864, Vol. 6, nr 1, s. 27-37Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A Mars-orbiting sub-millimeter sensor can be used to retrieve the magnetic field at low altitudes over large areas of significant planetary crustal magnetism of the sur- face of Mars from measurements of circularly polarized radi- ation emitted by the 368 GHz ground-state molecular oxygen absorption line. We design a full retrieval system for one ex- ample orbit to show the expected accuracies on the magnetic field components that one realization of such a Mars satellite mission could achieve. For one set of measurements around a tangent profile, we find that the two horizontal components of the magnetic field can be measured at about 200 nT error with a vertical resolution of around 4 km from 6 up to 70 km in tangent altitude. The error is similar regardless of the true strength of the magnetic field, and it can be reduced by re- peated measurements over the same area. The method and some of its potential pitfalls are described and discussed. 

  • 234.
    Larsson, Richard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Rayer, P.
    UK Met Office, Exeter.
    Saunders, R.
    UK Met Office, Exeter.
    Bell, W.
    UK Met Office, Exeter.
    Booton, A.
    UK Met Office, Exeter.
    Buehler, S.A.
    Meteorological Institute, University of Hamburg, Hamburg.
    Eriksson, P.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    John, V.
    EUMETSAT, Darmstadt.
    Modeling the Zeeman effect in high altitude SSMIS channels for numerical weather prediction profiles: Comparing a fast model and a line-by-line model2015Inngår i: Atmospheric Measurement Techniques Discussions, ISSN 1867-8610, E-ISSN 1867-8610, Vol. 8, nr 10, s. 10179-10211Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a comparison of a reference and a fast radiative transfer model using numerical weather prediction profiles for the Zeeman-affected high altitude Special Sensor Microwave Imager/Sounder channels 19–22. We find that the models agree well for channels 21 and 22 compared to the channels' system noise temperatures (1.9 and 1.3 K, respectively) and the expected profile errors at the affected altitudes (estimated to be around 5 K). For channel 22 there is a 0.5 K average difference between the models, with a standard deviation of 0.24 K for the full set of atmospheric profiles. Same channel, there is 1.2 K in average between the fast model and the sensor measurement, with 1.4 K standard deviation. For channel 21 there is a 0.9 K average difference between the models, with a standard deviation of 0.56 K. Same channel, there is 1.3 K in average between the fast model and the sensor measurement, with 2.4 K standard deviation. We consider the relatively small model differences as a validation of the fast Zeeman effect scheme for these channels. Both channels 19 and 20 have smaller average differences between the models (at below 0.2 K) and smaller standard deviations (at below 0.4 K) when both models use a two-dimensional magnetic field profile. However, when the reference model is switched to using a full three-dimensional magnetic field profile, the standard deviation to the fast model is increased to almost 2 K due to viewing geometry dependencies causing up to ± 7 K differences near the equator. The average differences between the two models remain small despite changing magnetic field configurations. We are unable to compare channels 19 and 20 to sensor measurements due to limited altitude range of the numerical weather prediction profiles. We recommended that numerical weather prediction software using the fast model takes the available fast Zeeman scheme into account for data assimilation of the affected sensor channels to better constrain the upper atmospheric temperatures.

  • 235.
    Larsson, Richard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Rayer, Peter
    UK Met Office, Exeter.
    Saunders, Roger
    UK Met Office, Exeter.
    Bell, William
    UK Met Office, Exeter.
    Booton, Anna
    UK Met Office, Exeter.
    Buehler, Stephan A.
    Meteorological Institute, University of Hamburg, Hamburg.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Earth and Space Sciences.
    John, Viju E.
    EUMETSAT, Darmstadt.
    Modeling the Zeeman effect in high altitude SSMIS channels for numerical weather prediction profiles: Comparing a fast model and a line-by-line model2016Inngår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 9, nr 2, s. 841-857Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a comparison of a reference and a fast radiative transfer model using numerical weather prediction profiles for the Zeeman-affected high altitude Special Sensor Microwave Imager/Sounder channels 19–22. We find that the models agree well for channels 21 and 22 compared to the channels' system noise temperatures (1.9 and 1.3 K, respectively) and the expected profile errors at the affected altitudes (estimated to be around 5 K). For channel 22 there is a 0.5 K average difference between the models, with a standard deviation of 0.24 K for the full set of atmospheric profiles. Same channel, there is 1.2 K in average between the fast model and the sensor measurement, with 1.4 K standard deviation. For channel 21 there is a 0.9 K average difference between the models, with a standard deviation of 0.56 K. Same channel, there is 1.3 K in average between the fast model and the sensor measurement, with 2.4 K standard deviation. We consider the relatively small model differences as a validation of the fast Zeeman effect scheme for these channels. Both channels 19 and 20 have smaller average differences between the models (at below 0.2 K) and smaller standard deviations (at below 0.4 K) when both models use a two-dimensional magnetic field profile. However, when the reference model is switched to using a full three-dimensional magnetic field profile, the standard deviation to the fast model is increased to almost 2 K due to viewing geometry dependencies causing up to ± 7 K differences near the equator. The average differences between the two models remain small despite changing magnetic field configurations. We are unable to compare channels 19 and 20 to sensor measurements due to limited altitude range of the numerical weather prediction profiles. We recommended that numerical weather prediction software using the fast model takes the available fast Zeeman scheme into account for data assimilation of the affected sensor channels to better constrain the upper atmospheric temperatures.

  • 236.
    Larsson, Richard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Ramstad, Robin
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Mendrok, Jana
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Kasai, Yasuko
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    A method for remote sensing of weak planetary magnetic fields: Simulated application to Mars2013Inngår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 40, nr 19, s. 5014-5018Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a method for characterizing the magnetic anomalies from the crustal fields in the lower atmosphere of Mars that requires two perpendicular linear polarization measurements of the Zeeman effect. The maximum effect of the magnetic field on the signal is found at the Doppler broadening width at low pressures rather than at the magnetically induced line frequency shift, and the effect strongly increases with increasing magnetic field strength. Based on simulations of the Zeeman-affected spectral cross section of the 119 GHz O2 line in a model Martian atmosphere at various magnetic field strengths, we conclude that it should be possible to probe the strength of the magnetic anomalies remotely with presently available technology. We discuss limitations of the method, how these results could be relevant to the interpretation of residuals in Herschel/HIFI observations of Mars, as well as the application to detection of exoplanetary magnetic fields.

  • 237.
    Lasue, J.
    et al.
    IRAP-OMP, CNRS-UPS, Toulouse.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zorzano Mier, Maria-Paz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    What ChemCam’s first shots tell us about martian dust?2017Konferansepaper (Annet vitenskapelig)
  • 238.
    Li, Yuangui
    et al.
    Department of Automation, Shanghai Jiaotong University.
    Lin, Chen
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Huang, Jinjie
    Department of Automation, Shanghai Jiaotong University.
    Zhang, Weidong
    Department of Automation, Shanghai Jiaotong University.
    A new method to construct reduced vector sets for simplifying support vector machines2006Inngår i: IEEE International Conference on Engineering of Intelligent Systems, Piscataway, NJ: IEEE Communications Society, 2006Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Support vector machines (SVM) are well known to give good results on pattern recognition problems, but for large scale problems, they exhibit substantially slower classification speeds than neural networks. It has been proposed to speed the SVM classification by approximating the decision function of SVM with a reduced vector set. A new method to construct the reduced vector set is proposed in this paper, which is constructed by merging the closest support vectors in an iterative fashion. A minor modification on the proposed method also has been made in order to simplify the decision function of reduced support vector machines (RSVM). The proposed method was compared with previous study on several benchmark data sets, and the computational results indicated that our method could simplify SVMs and RSVMs effectively, which will speed the classification for large scale problems

  • 239.
    Li, Yuangui
    et al.
    Department of Automation, Shanghai Jiaotong University.
    Lin, Chen
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zhang, Weidong
    Department of Automation, Shanghai Jiaotong University.
    Improved sparse least-squares support vector machine classifiers2006Inngår i: Neurocomputing, ISSN 0925-2312, E-ISSN 1872-8286, Vol. 69, nr 13-15, s. 1655-1658Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The least-squares support vector machines (LS-SVM) can be obtained by solving a simpler optimization problem than that in standard support vector machines (SVM). Its shortcoming is the loss of sparseness and this usually results in slow testing speed. Several pruning methods have been proposed. It is found that these methods can be further improved for classification problems. In this paper a different reduced training set is selected to re-train LS-SVM. Then a new procedure is proposed to obtain the sparseness. The performance of the proposed method is compared with other typical ones and the results indicate that it is more effective.

  • 240.
    Lidström, Viktor
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mass Loading of Space Plasmas2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The solar wind interaction with an icy comet is studied through a model problem. A hybrid simulation is done of a box with evenly distributed water ions and protons, where initially the water ions are stationary, and protons move with the speed of the solar wind. The purpose of the thesis is to investigate the interaction between the two species through the convective electric field, and focus is on early acceleration of pick-up ions, and deflection of the solar wind. It is relevant to the cometary case, because it enables study of the physics of this interaction, without involving other mechanisms, such as bow shock, magnetic field pile-up and draping. The species are found to exchange kinetic energy similar to a damped oscillator, where the dampening is caused by kinetic energy being transferred to the magnetic field. At early times, i.e. times smaller than the gyration time for the water ions, the solar wind does not lose much speed when it is deflected. For comparable number densities, the solar wind can be deflected more than 90° at early times, and loses more speed, and water ions are picked up faster. The total kinetic energy of the system decreases when energy builds up in the magnetic field. The nature of the energy exchange is strongly dependent on the number density ratio between water ions and protons. A density instability with behaviour similar to a plasma beam instability forms as energy in the magnetic field increases, and limits the amount of time the simulation preserves total energy, for the particular hybrid solver used. There is a discussion on the structure of the density instability, and it is compared to cometary simulations.

  • 241.
    Lue, Charles
    et al.
    Luleå tekniska universitet.
    Futaana, Yoshifumi
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Wieser, Martin
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Holmström, Mats
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Bhardwaj, Anil
    Space Physics Laboratory, Vikram Sarabhai Space Center, Trivandrum.
    Dhanya, M.B.
    Space Physics Laboratory, Vikram Sarabhai Space Center, Trivandrum.
    Wurz, Peter
    Physikalisches Institut, University of Bern.
    Strong influence of lunar crustal fields on the solar wind flow2011Inngår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 38, nr 3Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We discuss the influence of lunar magnetic anomalies on the solar wind and on the lunar surface, based on maps of solar wind proton fluxes deflected by the magnetic anomalies. The maps are produced using data from the Solar WInd Monitor (SWIM) onboard the Chandrayaan-1 spacecraft. We find a high deflection efficiency (average ∼10%, locally ∼50%) over the large-scale (>1000 km) regions of magnetic anomalies. Deflections are also detected over weak (<3 nT at 30 km altitude) and small-scale (<100 km) magnetic anomalies, which might be explained by charge separation and the resulting electric potential. Strong deflection from a wide area implies that the magnetic anomalies act as a magnetosphere-like obstacle, affecting the upstream solar wind. It also reduces the implantation rate of the solar wind protons to the lunar surface, which may affect space weathering near the magnetic anomalies.

  • 242.
    Mahaffy, P.R.
    et al.
    Planetary Environments Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland, NASA Goddard Space Flight Center.
    Conrad, Pamela G.
    NASA Goddard Space Flight Center.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Volatile and Isotopic Imprints of Ancient Mars2015Inngår i: Elements, ISSN 1811-5209, E-ISSN 1811-5217, Vol. 11, nr 1, s. 51-56Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The science investigations enabled by Curiosity rover's instruments focus on identifying and exploring the habitability of the Martian environment. Measurements of noble gases, organic and inorganic compounds, and the isotopes of light elements permit the study of the physical and chemical processes that have transformed Mars throughout its history. Samples of the atmosphere, volatiles released from soils, and rocks from the floor of Gale Crater have provided a wealth of new data and a window into conditions on ancient Mars.

  • 243.
    Mahfouf, J.-F.
    et al.
    CNRM–GAME, Météo-France and CNRS.
    Birman, C.
    CNRM–GAME, Météo-France and CNRS.
    Aires, F.
    Estellus, Paris.
    Prigent, C.
    L'Observatoire de Paris-LERMA.
    Orlandi, E.
    University of Cologne.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Information content on temperature and water vapour from a hyper-spectral microwave sensor2015Inngår i: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 141, nr 693, s. 3268-3284Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study examines the information content on atmospheric temperature and humidity profiles that could be provided by a future spaceborne microwave sensor with a few hundred radiances in the millimetre and submillimetre spectral domains (ranging from 7–800 GHz). A channel selection method based on optimal estimation theory is undertaken, using a database of profiles with associated errors from the European Centre for Medium-Range Weather Forecasts (ECMWF) numerical weather prediction model and the radiative transfer model Atmospheric Radiative Transfer Simulator (ARTS) under clear-sky conditions. The main results indicate that, by increasing the number of channels within the oxygen absorption band around 60 GHz and within the water-vapour absorption band at 183 GHz, the accuracy of temperature and humidity retrievals in the troposphere and stratosphere (for temperature) would be noticeably improved compared with present and planned microwave radiometers. The channels located in the absorption lines at 118 GHz and above 200 GHz do not bring significant additional information regarding atmospheric profiles under clear-sky conditions, partly due to greater radiometric noise. With a set of 137 selected channels that contribute to 90% of the total information content (measured by the degree of freedom for signal), it is possible to achieve almost the same performance in terms of variance error reduction as with 276 candidate channels. Sensitivity studies of various prescribed quantities defining the channel selection have been undertaken, in order to check the robustness of the conclusions. They show that none of the choices modifies the above findings.

  • 244.
    Mannes, Quentin
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    ICE Cubes Mission: Design, Development and Documentation of the Cube-Zero System2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The International Space Station provides a high-quality of microgravity and extended exposure time which makes it a platform of choice for microgravity research. In order to increase accessibility of onboard experimentation, Space Applications Services will soon launch the ICE Cubes facility as part of its ICE Cubes Service. The facility is foreseen to host standardized plug-and-play payload cubes to reduce overall cost and procedure time required to install payloads on the station. To remotely support the facility it is decided to develop a utility cube named Cube-Zero that will be launched and installed with the facility on the station. This thesis work included the complete design, development and documentation of the cube.

    The thesis started by conducting a preliminary needs and market study from which two specific purposes were defined for the cube. In addition to its original function of support-utility, the cube is tasked to be a technical commercial demonstrator for the service. This led to the conceptual design of the cube as a multidisciplinary framework able to host two user-defined experiment modules. The preliminary concept was further refined in this paper and with support of prototypes, simulations and analyses led to a final functional design for the Cube-Zero.

    The work is concluded with the manufacturing of an engineering model of the cube. The model is fully operational, can support the test of the facility before launch and can demonstrate to users its versatility and ease of use in operating any kind of experiment module.

    Eventually, the information gathered in this thesis report will support future users into developing their own Cube-Zero payload module and guide Space Applications Services into manufacturing, testing and operating the Cube-Zero protoflight model.

  • 245.
    Martell, Angel Alfredo
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Benchmarking structure from motion algorithms with video footage taken from a drone against laser-scanner generated 3D models2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Structure from motion is a novel approach to generate 3D models of objects and structures. The dataset simply consists of a series of images of an object taken from different positions. The ease of the data acquisition and the wide array of available algorithms makes the technique easily accessible. The structure from motion method identifies features in all the images from the dataset, like edges with gradients in multiple directions, and tries to match these features between all the images and then computing the relative motion that the camera was subject to between any pair of images. It builds a 3D model with the correlated features. It then creates a 3D point cloud with colour information of the scanned object. There are different implementations of the structure from motion method that use different approaches to solve the feature-correlation problem between the images from the data set, different methods for detecting the features and different alternatives for sparse reconstruction and dense reconstruction as well. These differences influence variations in the final output across distinct algorithms.

    This thesis benchmarked these different algorithms in accuracy and processing time. For this purpose, a terrestrial 3D laser scanner was used to scan structures and buildings to generate a ground truth reference to which the structure from motion algorithms were compared. Then a video feed from a drone with a built-in camera was captured when flying around the structure or building to generate the input for the structure from motion algorithms. Different structures are considered taking into account how rich or poor in features they are, since this impacts the result of the structure from motion algorithms. The structure from motion algorithms generated 3D point clouds, which then are analysed with a tool like CloudCompare to benchmark how similar it is to the laser scanner generated data, and the runtime was recorded for comparing it across all algorithms. Subjective analysis has also been made, such as how easy to use the algorithm is and how complete the produced model looks in comparison to the others.

    In the comparison it was found that there is no absolute best algorithm, since every algorithm highlights in different aspects. There are algorithms that are able to generate a model very fast, managing to scale the execution time linearly in function of the size of their input, but at the expense of accuracy. There are also algorithms that take a long time for dense reconstruction, but generate almost complete models even in the presence of featureless surfaces, like COLMAP modified PatchMacht algorithm. The structure from motion methods are able to generate models with an accuracy of up to \unit[3]{cm} when scanning a simple building, where Visual Structure from Motion and Open Multi-View Environment ranked among the most accurate. It is worth highlighting that the error in accuracy grows as the complexity of the scene increases. Finally, it was found that the structure from motion method cannot reconstruct correctly structures with reflective surfaces, as well as repetitive patterns when the images are taken from mid to close range, as the produced errors can be as high as \unit[1]{m} on a large structure.

  • 246.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    The EChO science case2017Inngår i: EChO - Exoplanet Characterisation Observatory / [ed] Tinetti, Giovanna, Drossart, Pierre, Springer Netherlands, 2017Kapittel i bok, del av antologi (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    The discovery of almost two thousand exoplanets has revealed an unexpectedly diverse planet population.We see gas giants in few-day orbits, whole multi-planet systems within the orbit of Mercury, and newpopulations of planets with masses between that of the Earth and Neptune – all unknown in the SolarSystem. Observations to date have shown that our Solar System is certainly not representative of the generalpopulation of planets in our Milky Way. The key science questions that urgently need addressing aretherefore: What are exoplanets made of? Why are planets as they are? How do planetary systems work andwhat causes the exceptional diversity observed as compared to the Solar System? The EChO (ExoplanetCharacterisation Observatory) space mission was conceived to take up the challenge to explain this diversityin terms of formation, evolution, internal structure and planet and atmospheric composition. This requires indepthspectroscopic knowledge of the atmospheres of a large and well-defined planet sample for whichprecise physical, chemical and dynamical information can be obtained.In order to fulfil this ambitious scientific program, EChO was designed as a dedicated survey mission fortransit and eclipse spectroscopy capable of observing a large, diverse and well-defined planet sample withinits four-year mission lifetime. The transit and eclipse spectroscopy method, whereby the signal from the starand planet are differentiated using knowledge of the planetary ephemerides, allows us to measureatmospheric signals from the planet at levels of at least 10-4 relative to the star. This can only be achieved inconjunction with a carefully designed stable payload and satellite platform. It is also necessary to providebroad instantaneous wavelength coverage to detect as many molecular species as possible, to probe thethermal structure of the planetary atmospheres and to correct for the contaminating effects of the stellarphotosphere. This requires wavelength coverage of at least 0.55 to 11 μm with a goal of covering from 0.4to 16 μm. Only modest spectral resolving power is needed, with R~300 for wavelengths less than 5 μm andR~30 for wavelengths greater than this.The transit spectroscopy technique means that no spatial resolution is required. A telescope collecting area ofabout 1 m2 is sufficiently large to achieve the necessary spectro-photometric precision: for the Phase A studya 1.13 m2 telescope, diffraction limited at 3 μm has been adopted. Placing the satellite at L2 provides a coldand stable thermal environment as well as a large field of regard to allow efficient time-critical observationof targets randomly distributed over the sky. EChO has been conceived to achieve a single goal: exoplanetspectroscopy. The spectral coverage and signal-to-noise to be achieved by EChO, thanks to its high stabilityand dedicated design, would be a game changer by allowing atmospheric composition to be measured withunparalleled exactness: at least a factor 10 more precise and a factor 10 to 1000 more accurate than currentobservations. This would enable the detection of molecular abundances three orders of magnitude lower thancurrently possible and a fourfold increase from the handful of molecules detected to date. Combining thesedata with estimates of planetary bulk compositions from accurate measurements of their radii and masseswould allow degeneracies associated with planetary interior modelling to be broken, giving unique insightinto the interior structure and elemental abundances of these alien worlds.EChO would allow scientists to study exoplanets both as a population and as individuals. The mission cantarget super-Earths, Neptune-like, and Jupiter-like planets, in the very hot to temperate zones (planettemperatures of 300 K - 3000 K) of F to M-type host stars. The EChO core science would be delivered by athree-tier survey. The EChO Chemical Census: This is a broad survey of a few-hundred exoplanets, whichallows us to explore the spectroscopic and chemical diversity of the exoplanet population as a whole. TheEChO Origin: This is a deep survey of a subsample of tens of exoplanets for which significantly highersignal to noise and spectral resolution spectra can be obtained to explain the origin of the exoplanet diversity(such as formation mechanisms, chemical processes, atmospheric escape). The EChO Rosetta Stones: Thisis an ultra-high accuracy survey targeting a subsample of select exoplanets. These will be the bright"benchmark" cases for which a large number of measurements would be taken to explore temporalvariations, and to obtain two and three dimensional spatial information on the atmospheric conditionsthrough eclipse-mapping techniques.If EChO were launched today, the exoplanets currently observed are sufficient to provide a large and diversesample. The Chemical Census survey would consist of > 160 exoplanets with a range of planetary sizes,temperatures, orbital parameters and stellar host properties. Additionally, over the next ten years, severalnew ground- and space-based transit photometric surveys and missions will come on-line (e.g. NGTS,CHEOPS, TESS, PLATO), which will specifically focus on finding bright, nearby systems. The current5rapid rate of discovery would allow the target list to be further optimised in the years prior to EChO’s launch and enable the atmospheric characterisation of hundreds of planets.

  • 247.
    Martin-Torres, Javier
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mier, Maria-Paz Zorzano
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Vida Extraterrestre: Implicaciones2015Inngår i: Burgense, ISSN 0521-8195, Vol. 55, nr 1, s. 197-206Artikkel i tidsskrift (Fagfellevurdert)
  • 248.
    Martin-Torres, Javier
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zorzano, María-Paz
    Centro de Astrobiologia, INTA-CSIC, Madrid , Instituto Nacional de Técnica Aeroespacial, Madrid, Centro de Astrobiologia, Madrid.
    Valentin-Serrano, Patricia
    CSIC-UGR - Instituto Andaluz de Ciencias de la Tierra (IACT), Granada.
    Harri, Ari-Matti
    Earth Observation Research Division, Finnish Meteorological Institute, Helsinki.
    Genzer, Maria
    Finnish Meteorological Institute, Earth Observation Research Division, Finnish Meteorological Institute, Helsinki.
    Kemppainen, Osku
    Finnish Meteorological Institute, Earth Observation Research Division, Finnish Meteorological Institute, Helsinki.
    Rivera-Valentin, Edgard G.
    Arecibo Observatory, Universities Space Research Association, Arecibo, Puerto Rico.
    Jun, Insoo
    California Institute of Technology, Jet Propulsion Laboratory.
    Wray, James J.
    School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta.
    Madsen, Morten B.
    Niels Bohr Institute, University of Copenhagen.
    Goetz, Walter
    Max-Planck-Institut für Solar System Research.
    McEwen, Alfred S,
    Lunar and Planetary Lab, University of Arizona, Tucson.
    Hardgrove, Craig
    Arizona State University, Department of Earth & Planetary Sciences, University of Tennessee, Knoxville, Malin Space Science Systems.
    Renno, Nilton
    University of Michigan, College of Engineering, University of Michigan, Ann Arbor.
    Chevrier, Vincent F.
    Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville.
    Mischna, Michael A.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Navarro-Gonzalez, Rafael
    Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de Mexico, Ciudad Universitaria, Centro de Astrobiologia, INTA-CSIC, Madrid , Universidad Nacional Autónoma de México, Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Mexico D.F., Laboratorio de Química de Plasmas y Estudios Planetarios, Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México.
    Martínez-Frías, Jesús
    Centro de Astrobiologia, INTA-CSIC, Madrid , Instituto de Geociencias (CSIC-UCM), 28040 Madrid.
    Conrad, Pamela G.
    NASA Goddard Space Flight Center, Solar System Exploration Division, Goddard Space Flight Center, National Aeronautics and Space Administration, Greenbelt, Maryland.
    McConnochie, Timothy H.
    Department of Astronomy, University of Maryland, College Park.
    Cockell, Charles
    ESO, UK Centre for Astrobiology, School of Physics and Astronomy,.
    Berger, Gilles
    IRAP/CNRS, Institut de Recherche en Astrophysique et Planetologie, Toulouse, Université de Toulouse, UPS-OMP, IRAP.
    Vasavada, Ashwin
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Sumner, Dawn Y.
    Department of Earth and Planetary Sciences, University of California, Davis, Department of Geology, University of California, Davis.
    Vaniman, David T.
    Planetary Science Institute, Tucson.
    Transient liquid water and water activity at Gale crater on Mars2015Inngår i: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 8, nr 5, s. 357-361Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Water is a requirement for life as we know it1. Indirect evidence of transient liquid water has been observed from orbiter on equatorial Mars2, in contrast with expectations from large-scale climate models. The presence of perchlorate salts, which have been detected at Gale crater on equatorial Mars by the Curiosity rover3, 4, lowers the freezing temperature of water5. Moreover, perchlorates can form stable hydrated compounds and liquid solutions by absorbing atmospheric water vapour through deliquescence6, 7. Here we analyse relative humidity, air temperature and ground temperature data from the Curiosity rover at Gale crater and find that the observations support the formation of night-time transient liquid brines in the uppermost 5 cm of the subsurface that then evaporate after sunrise. We also find that changes in the hydration state of salts within the uppermost 15 cm of the subsurface, as measured by Curiosity, are consistent with an active exchange of water at the atmosphere–soil interface. However, the water activity and temperature are probably too low to support terrestrial organisms8. Perchlorates are widespread on the surface of Mars9 and we expect that liquid brines are abundant beyond equatorial regions where atmospheric humidity is higher and temperatures are lower.

  • 249.
    Martín-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A space rose by another name smells sweeter2017Inngår i: New scientist (1971), ISSN 0262-4079, Vol. 233, nr 3116, s. 52-54Artikkel i tidsskrift (Fagfellevurdert)
  • 250.
    Martín-Torres, Javier
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zorzano Mier, Maria-Paz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Should We Invest in Martian Brine Research to Reduce Mars Exploration Costs?2017Inngår i: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 17, nr 1, s. 3-7Artikkel i tidsskrift (Fagfellevurdert)
2345678 201 - 250 of 374
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