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  • 51.
    Birman, Camille
    et al.
    Météo-France-CNRS, Toulouse .
    Mahfouf, Jean-François
    Météo-France-CNRS, Toulouse.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. IRV.
    Mendrok, Jana
    Chalmers University of Technology, Gothenburg, Sweden.
    Buehler, Stefan A.
    University of Hamburg, Hamburg.
    Brath, Manfred
    University of Hamburg, Hamburg .
    Information content on hydrometeors from millimeter and sub-millimeter wavelengths2017Ingår i: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 69, nr 1, artikel-id 1271562Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study examines the information content on hydrometeors that could be provided by a future HYperspectralMicrowave Sensor (HYMS) with frequencies ranging from 6.9 to 874 GHz (millimeter and sub-millimeter regions). Through optimal estimation theory the information content is expressed quantitatively in terms of degrees of freedom for signal (DFS). For that purpose the Atmospheric Radiative Transfer Simulator (ARTS) and its Jacobians are used with a set of 25 cloudy and precipitating profiles and their associated errors from the European Centre for Medium-range Weather Forecasting (ECMWF) global numerical weather prediction model.

    In agreement with previous studies it is shown that frequencies between 10 and 40 GHz are the most informative ones for liquid and rain water contents. Similarly, the absorption band at 118 GHz contains significant information on liquid precipitation. A set of new window channels (15.37-, 40.25-, 101-GHz) could provide additional information on the liquid phase. The most informative channels on cloud icewater are the window channels at 664 and 874GHz and thewater vapour absorption bands at 325 and 448 GHz. Regarding snow water contents, the channels having the largest DFS values are located inwindow regions (150-, 251-, 157-, 101-GHz). However it is necessary to consider 90 channels in order to represent 90% of the DFS. The added value of HYMS has been assessed against current Special Sensor Microwave Imager/Sounder (SSMI/S) onboard the Defense Meteorological Satellite Program (DMSP) and future (Microwave Imager/Ice Cloud Imager (MWI/ICI) onboard European Polar orbiting Satellite – Second Generation (EPS-SG)) microwave sensors. It appears that with a set of 276 channels the information content on hydrometeors would be significantly enhanced: the DFS increases by 1.7 against MWI/ICI and by 3 against SSMI/S. A number of tests have been performed to examine the robustness of the above results. The most informative channels on solid hydrometeors remain the same over land and over ocean surfaces. On the other hand, the database is not large enough to produce robust results over land surfaces for liquid hydrometeors. The sensitivity of the results to the microphysical properties of frozen hydrometeors has been investigated. It appears that a change in size distribution and scattering properties can move the large information content of the channels at 664 and 874 GHz from cloud ice to solid precipitation.

  • 52.
    Blanco, Enrique
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    DESIGN OF A SCALABLE, ADAPTABLE AND RELIABLE DEORBITING MECHANISM2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 53.
    Bohra, Murtaza M.
    et al.
    Space Mechatronics Group, Institute for Aerospace Studies, University of Toronto.
    Xu, Linsen
    Space Mechatronics Group, Institute for Aerospace Studies, University of Toronto.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    CPG-based online trajectory generation for quadruped rovers2016Ingår i: 2015 IEEE International Conference on Robotics and Biomimetics (ROBIO): Zhuhai, 6-9 Dec. 2015, Piscataway, NJ: IEEE Communications Society, 2016, s. 1053-1058, artikel-id 7418911Konferensbidrag (Refereegranskat)
    Abstract [en]

    Legged rovers are often considered as viable solutions for traversing unknown terrain. A 2D sagittal plane rover model, based on a domestic cat, is considered in this paper, and an online model-free gait planning framework is implemented using Central Pattern Generators. The framework is used to generate joint trajectories for any arbitrarily varying speed profile, and regulate locomotion transition and speed modulation, both continuously and endogenously. For a continuously changing speed profile, the gait transition is continuous as well. For a discontinuously changing speed profile, a hopping motion is observed, because the rover's thrust speed cannot increase discontinuously

  • 54.
    Borovoi, Anatoli
    et al.
    Institute of Atmospheric Optics, Rus. Acad. Sci., Tomsk, Russia.
    Reichard, Jens
    Richard-Aβmann-Observatorium, DWD, Lindenberg, Germany.
    Görsdorf, Ulrich
    Richard-Aβmann-Observatorium, DWD, Lindenberg, Germany.
    Wolf, Veronika
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Richard-Aβmann-Observatorium, DWD, Lindenberg, Germany.
    Konoshonkin, Alexander
    Institute of Atmospheric Optics, Rus. Acad. Sci., Tomsk, Russia.
    Shishko, Victor
    Institute of Atmospheric Optics, Rus. Acad. Sci., Tomsk, Russia.
    Kustova, Natalia
    Institute of Atmospheric Optics, Rus. Acad. Sci., Tomsk, Russia.
    Retrieving microphysics of cirrus clouds from data measured with raman lidar ramses and a tilted ceilometer2018Ingår i: EPJ Web of Conferences, ISSN 2101-6275, E-ISSN 2100-014X, Vol. 176, artikel-id 08002Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To develop a microphysical model of cirrus clouds, data obtained by Raman lidar RAMSES and a tilted ceilometer are studied synergistically. The measurements are interpreted by use of a data archive containing the backscattering matrixes as well as the depolarization, color and lidar ratios of ice crystals of different shapes, sizes and spatial orientations calculated within the physical-optics approximation.

  • 55.
    Brett, Christopher
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Control System Design for an Orbital Inspection Vehicle and Servicing Satellite Using Thrust-Vectoring Cold-Gas Propulsion2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This Thesis presents the work leading to the design of a closed loop control system for a prototype six-degree-of-freedom orbital inspection vehicle named Cerberus. Each of Cerberus' three compressed Nitrogen gas thrusters can be rotated about their elevation and azimuth axes, providing a thrust-vectored control capability. In order to test this capability in a simulated space environment Cerberus is mounted on the DAWN six-degree-of-freedom air-bearing vehicle. The control schemes presented in this thesis allow joystick control, station-keeping at a set distance from a moving target and inspection fly-around manoeuvres to be conducted before a docking procedure is initiated with a non-cooperative client vehicle. The following Thesis describes the decision-making process used to select the appropriate control scheme for each control mode, with the purpose of providing accurate position control for the module.

  • 56.
    Brolies, Thomas W.
    et al.
    Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Burch, James L.
    Southwest Research Institute, 6220 Culebra Road, San Antonio, Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Clark, Grace A.
    Heliophysics Division, Goddard Space Flight Center.
    Koenders, Christoph
    Institut für Geophysik und Extraterrestrische Physik, Technische Universität Braunschweig.
    Behar, Etienne
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Goldstein, Raymond M.
    Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Fuselier, Stephen Anthony
    Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Mandt, Kathleen E.
    Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Mokashi, Prachet
    Southwest Research Institute, 6220 Culebra Road, San Antonio, Space Science and Engineering Division, Southwest Research Institute (SwRI).
    Samara, M.
    Heliophysics Division, Goddard Space Flight Center.
    Rosetta observations of solar wind interaction with the comet 67P/Churyumov-Gerasimenko2015Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 583, artikel-id A21Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context. The Rosetta spacecraft arrived at the comet 67P/Churyumov-Gerasimenko on August 6, 2014, which has made it possible to perform the first study of the solar wind interacting with the coma of a weakly outgassing comet. Aims. It is shown that the solar wind experiences large deflections (>45°) in the weak coma. The average ion velocity slows from the mass loading of newborn cometary ions, which also slows the interplanetary magnetic field (IMF) relative to the solar wind ions and subsequently creates a Lorentz force in the frame of the solar wind. The Lorentz force in the solar wind frame accelerates ions in the opposite direction of cometary pickup ion flow, and is necessary to conserve momentum. Methods. Data from the Ion and Electron Sensor are studied over several intervals of interest when significant solar wind deflection was observed. The deflections for protons and for He++ were compared with the flow of cometary pickup ions using the instrument's frame of reference. We then fit the data with a three-dimensional Maxwellian, and rotated the flow vectors into the Comet Sun Equatorial coordinate system, and compared the flow to the spacecraft's position and to the local IMF conditions. Results. Our observations show that the solar wind may be deflected in excess of 45° from the anti-sunward direction. Furthermore, the deflections change direction on a variable timescale. Solar wind protons are consistently more deflected than the He++. The deflections are not ordered by the spacecraft's position relative to the comet, but large changes in deflection are related to changes in the orthogonal IMF components

  • 57.
    Brown, A.G.A.
    et al.
    Leiden Observatory, Leiden University.
    Granvik, Mikael
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Department of Physics, University of Helsinki.
    Zwitter, T.
    University of Ljubljana, Faculty of Mathematics & Physics.
    Summary of the contents and survey properties2018Ingår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 16, nr A1Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context. We present the second Gaia data release, Gaia DR2, consisting of astrometry, photometry, radial velocities, and information on astrophysical parameters and variability, for sources brighter than magnitude 21. In addition epoch astrometry and photometry are provided for a modest sample of minor planets in the solar system. Aims. A summary of the contents of Gaia DR2 is presented, accompanied by a discussion on the differences with respect to Gaia DR1 and an overview of the main limitations which are still present in the survey. Recommendations are made on the responsible use of Gaia DR2 results. Methods. The raw data collected with the Gaia instruments during the first 22 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into this second data release, which represents a major advance with respect to Gaia DR1 in terms of completeness, performance, and richness of the data products. Results. Gaia DR2 contains celestial positions and the apparent brightness in G for approximately 1.7 billion sources. For 1.3 billion of those sources, parallaxes and proper motions are in addition available. The sample of sources for which variability information is provided is expanded to 0 : 5 million stars. This data release contains four new elements: broad-band colour information in the form of the apparent brightness in the G(BP) (330-680 nm) and G(RP) (630-1050 nm) bands is available for 1.4 billion sources; median radial velocities for some 7 million sources are presented; for between 77 and 161 million sources estimates are provided of the stellar effective temperature, extinction, reddening, and radius and luminosity; and for a pre-selected list of 14 000 minor planets in the solar system epoch astrometry and photometry are presented. Finally, Gaia DR2 also represents a new materialisation of the celestial reference frame in the optical, the Gaia-CRF2, which is the first optical reference frame based solely on extragalactic sources. There are notable changes in the photometric system and the catalogue source list with respect to Gaia DR1, and we stress the need to consider the two data releases as independent. Conclusions. Gaia DR2 represents a major achievement for the Gaia mission, delivering on the long standing promise to provide parallaxes and proper motions for over 1 billion stars, and representing a first step in the availability of complementary radial velocity and source astrophysical information for a sample of stars in the Gaia survey which covers a very substantial fraction of the volume of our galaxy.

  • 58.
    Browne Mwakyanjala, Moses
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Beek, Jaap van de
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Software-defined radio transceiver for QB50 CubeSat telemetry and telecommand2016Ingår i: Proceedings of the 34th AIAA International Communications Satellite Systems Conference (ICSSC 2016), American Institute of Aeronautics and Astronautics, 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents the development of a ground system based on software-defined radio for supporting both ground testing and space telemetry and telecommand of one of the nanosatellites in the QB50 mission. The QB50 project is an ongoing European Commission Seventh Framework initiative, which aims at launching a constellation of 50 CubeSats in the lower thermosphere to carry out in-situ scientific measurements. The paper discusses the implementation of amateur radio protocols and telecommunication modulation schemes on the ground system. The system setup, deployment and scheduling are also discussed using two separate ground stations. The use of different software for testing the system is detailed, the results show the operability of the developed ground system. © 2016, American Institute of Aeronautics and Astronautics Inc

  • 59.
    Browne Mwakyanjala, Moses
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Institute for Aerospace Studies, University of Toronto.
    Beek, Jaap van de
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Verification of phase and frequency modulation for software-defined radio baseband systems using field data2017Ingår i: 35th AIAA International Communications Satellite Systems Conference, ICSSC 2017, American Institute of Aeronautics and Astronautics, 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents the verification of phase and frequency modulation schemes for a software-defined radio baseband system that is being prototyped to support satellite telemetry, telecommand and ranging. It presents the theory behind the two modulation schemes, implementation and verification against emulated signals from a space-qualified hardware-based baseband system as well as from the Odin satellite.

  • 60.
    Browne Mwakyanjala, Moses
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    van de Beek, Jaap
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Verication of phase and frequency modulation for software-defined radio baseband systems using field data2017Konferensbidrag (Refereegranskat)
  • 61.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Atmospheric radiative-transfer simulator2006Ingår i: Thermal Microwave Radiation: Applications for Remote Sensing, London: Institution of Engineering and Technology, 2006, s. 54-56Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 62.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    UTH-MOS: Wasserdampf und Cirren in der oberen Troposphäre aus operationellen meteorologischen Satellitendaten2006Rapport (Övrigt vetenskapligt)
  • 63.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Courcoux, N.
    Universität Bremen, Institute of Environmental Physics.
    John, Viju Oommen
    University of Miami, Rosenstiel School of Marine and Atmospheric Sciences, Miami.
    Radiative transfer calculations for a passive microwave satellite sensor: comparing a fast model and a line-by-line model2006Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 111, nr 20, s. 20304-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    [1] A comparison between the fast radiative transfer model Radiative Transfer for the TIROS Operational Vertical Sounder (RTTOV-7) and the physical radiative transfer model Atmospheric Radiative Transfer Simulator ( ARTS) was carried out. Radiances were simulated for the sounding channels of the Advanced Microwave Sounding Unit B (AMSU-B) for the whole globe for a single time of a single day ( 1 January 2000, 0000 UT). Temperature, pressure, and specific humidity profiles from the reanalysis data set ERA-40 of the European Centre for Medium-Range Weather Forecasts (ECMWF) were used as input for both models; geopotential height profiles were also used but only as input for ARTS. The simulations were made for two different surface emissivities, 0.60 and 0.95. The low surface emissivity case exhibits the larger radiance differences. Although the global values of the mean difference and standard deviation are small ( for example, the global mean difference for channel 18 is 0.014 K and the standard deviation is 0.232 K), the examination of the geographical distribution of the differences shows that large positive or negative values are observed over dry regions of high northern and southern latitudes and over dry elevated regions. The origin of these differences was found to be due to errors introduced by the transmittance parametrization used in RTTOV.

  • 64.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Defer, E.
    CNRS, Laboratoire d'Etudes du Rayonnement et de la Matière en Astrophysique, Observatoire de Paris.
    Evans, F.
    Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder.
    Eliasson, Salomon
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mendrok, Jana
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Erikssson, P.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Lee, C.
    Met Office Hadley Centre, Exeter.
    Jimenez, C.
    CNRS, Laboratoire d'Etudes du Rayonnement et de la Matière en Astrophysique, Observatoire de Paris.
    Prigent, C.
    CNRS, Laboratoire d'Etudes du Rayonnement et de la Matière en Astrophysique, Observatoire de Paris.
    Crewell, S.
    Institute for Geophysics and Meteorology, University of Cologne.
    kasai, Y.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Bennartz, R.
    Atmospheric and Oceanic Sciences, University of Wisconsin.
    Gasiewski, A.J.
    NOAA-CU Center for Environmental Technology (CET), Department of Electrical and Computer Engineering, University of Colorado at Boulder.
    Observing ice clouds in the submillimeter spectral range: the CloudIce mission proposal for ESA's Earth Explorer 82012Ingår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 5, nr 7, s. 1529-1549Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Passive submillimeter-wave sensors are a way to obtain urgently needed global data on ice clouds, particularly on the so far poorly characterized 'essential climate variable' ice water path (IWP) and on ice particle size. CloudIce was a mission proposal to the European Space Agency ESA in response to the call for Earth Explorer 8 (EE8), which ran in 2009/2010. It proposed a passive submillimeter-wave sensor with channels ranging from 183 GHz to 664 GHz. The article describes the CloudIce mission proposal, with particular emphasis on describing the algorithms for the data-analysis of submillimeter-wave cloud ice data (retrieval algorithms) and demonstrating their maturity. It is shown that we have a robust understanding of the radiative properties of cloud ice in the millimeter/submillimeter spectral range, and that we have a proven toolbox of retrieval algorithms to work with these data. Although the mission was not selected for EE8, the concept will be useful as a reference for other future mission proposals.

  • 65.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Lemke, Oliver
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Absorption lookup tables in the radiative transfer model ARTS2011Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 112, nr 10, s. 1559-1567Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We describe the lookup table approach that is used to store pre-calculated absorption data in the radiative transfer model ARTS. The table stores absorption cross sections as a function of frequency, pressure, temperature, and the water vapor volume mixing ratio, where the last dimension is only included for those gas species that require it. The table is used together with an extraction strategy, which uses polynomial interpolation, with recommended interpolation orders between five and seven. We also derived recommended default settings for grid spacings and interpolation orders, and verified that the approach gives very accurate results with these default settings. The tested instrument setups were for AMSU-B, HIRS, and Odin, three well-known satellite remote sensing instruments covering a wide range of frequencies and viewing geometries. Errors introduced by the lookup table were found to be always below a few millikelvin, in terms of the simulated brightness temperature.

  • 66.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Jimenez, C.
    Evans, K. F.
    Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder.
    Eriksson, P.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Rydberg, B.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Heymsfield, A.
    NCAR, Boulder, Colorado.
    Stubenrauch, C.
    CNRS/IPSL - Laboratoire de Meteorologie Dynamique, Ecole Polytechnique, Palaiseau.
    Lohmann, U.
    ETH Zurich, Institute for Atmospheric and Climate Science.
    Emde, C.
    Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen.
    John, V. O.
    Met Office Hadley Centre, Exeter.
    Sreerekha, T. R.
    Met Office Hadley Centre, Exeter.
    Davis, C. P.
    School of Geosciences, University of Edinburgh.
    A concept for a satellite mission to measure cloud ice water path, ice particle size, and cloud altitude2007Ingår i: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 133, nr Suppl.2, s. 109-128Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A passive satellite radiometer operating at submillimetre wavelengths can measure cloud ice water path (IWP), ice particle size, and cloud altitude. The paper first discusses the scientific background for such measurements. Formal scientific mission requirements are derived, based on this background and earlier assessments. The paper then presents a comprehensive prototype instrument and mission concept, and demonstrates that it meets the requirements. The instrument is a conically scanning 12-channel radiometer with channels between 183 and 664 GHz, proposed to fly in tandem with one of the Metop satellites. It can measure IWP with a relative accuracy of approximately 20% and a detection threshold of approximately 2 g m-2. The median mass equivalent sphere diameter of the ice particles can be measured with an accuracy of approximately 30 µm, and the median IWP cloud altitude can be measured with an accuracy of approximately 300 m. All the above accuracies are median absolute error values; root mean square error values are approximately twice as high, due to rare outliers.

  • 67.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    John, V.O.
    Met Office Hadley Centre, Exeter.
    Kottayil, Ajil
    Milz, Mathias
    Eriksson, P.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Efficient radiative transfer simulations for a broadband infrared radiometer: combining a weighted mean of representative frequencies approach with frequency selection by simulated annealing2010Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 111, nr 4, s. 602-615Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a method to efficiently simulate the measurements of a broadband infrared instrument. The High Resolution Infrared Radiation Sounder (HIRS) instrument is used as example to illustrate the method. The method uses two basic ideas. Firstly, the channel radiance can be approximated by a weighted mean of the radiance at some representative frequencies, where the weights can be determined by linear regression. Secondly, a near-optimal set of representative frequencies can be found by simulated annealing.The paper does not only describe and analyze the method, it also describes how the method was used to derive optimized frequency grids for the HIRS instruments on the satellites TIROS N, NOAA 6-19, and Metop A. The grids and weights, as well as the optimization algorithm itself are openly available under a GNU public license.

  • 68.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Kuhn, Thomas
    Universität Bremen, Institute of Environmental Physics.
    Bauer, Agnes
    Institute of Environmental Physics, University of Bremen.
    Corrigendum to 'Water vapor continuum: Absorption measurements at 350 GHz and model calculations' [JQSRT 2002;74:545-62]2008Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 109, nr 9, s. 1743-1744Artikel i tidskrift (Övrigt vetenskapligt)
  • 69.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Kuvatov, M.
    Institut für Umweltphysik (Institute for Environmental Physics) (IUP), University of Bremen.
    John, V. O.
    Meteorology and Physical Oceanography, Rosenstiel School for Marine and Atmospheric Science (RSMAS), University of Miami.
    Milz, Mathias
    Soden, B.J.
    Meteorology and Physical Oceanography, Rosenstiel School for Marine and Atmospheric Science (RSMAS), University of Miami.
    Jackson, D.L.
    Cooperative Institute for Research in Environmental Science (CIRES), University of Colorado, NOAA Earth System Research Laboratory.
    Norholt, J.
    Institut für Umweltphysik (Institute for Environmental Physics) (IUP), University of Bremen.
    An upper tropospheric humidity data set from operational satellite microwave data2008Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 113, nr 14, s. D14110-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    183.31 GHz observations from the Advanced Microwave Sounding Unit B (AMSUB) instruments onboard the NOAA 15, 16, and 17 satellites were used to derive a new data set of Upper Tropospheric Humidity (UTH). The data set consist of monthly median and mean data on a 1.5 degrees latitude-longitude grid between 60 degrees S and 60 degrees N, and covers the time period of January 2000 to February 2007. The data from all three instruments are very consistent, with relative difference biases of less than 4% and relative difference standard deviations of 7%. Radiometric contributions by high ice clouds and by the Earth's surface affect the measurements in certain areas. The uncertainty due to clouds is estimated to be up to approximately 10%RH in areas with deep convection. The uncertainty associated with contamination from surface emission can exceed 10%RH in midlatitude winter, where the data therefore should be regarded with caution. Otherwise the surface influence appears negligible. The paper also discusses the UTH median climatology and seasonal cycle, which are found to be broadly consistent with UTH climatologies from other sensors. Finally, the paper presents an initial validation of the new data set against IR satellite data and radiosonde data. The observed biases of up to 9%RH (wet bias relative to HIRS) were found to be broadly consistent with expectations based on earlier studies. The observed standard deviations against all other data sets were below 6%RH. The UTH data are available to the scientific community on http://www.sat.ltu.se.

  • 70.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Kuvatov, Mashrab
    IUP, University of Bremen.
    Sreerekha, T. R.
    UK Met Office, Exeter.
    John, Viju Oommen
    RSMAS, University of Miami.
    Rydberg, Bengt
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Notholt, Justus
    IUP, University of Bremen.
    A cloud filtering method for microwave upper tropospheric humidity measurements2007Ingår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 7, nr 21, s. 5531-5542Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The paper presents a cloud filtering method for upper tropospheric humidity (UTH) measurements at 183.31±1.00 GHz. The method uses two criteria: a viewing angle dependent threshold on the brightness temperature at 183.31±1.00 GHz, and a threshold on the brightness temperature difference between another channel and 183.31±1.00 GHz. Two different alternatives, using 183.31±3.00 GHz or 183.31±7.00 GHz as the other channel, are studied. The robustness of this cloud filtering method is demonstrated by a mid-latitudes winter case study. The paper then studies different biases on UTH climatologies. Clouds are associated with high humidity, therefore the possible dry bias introduced by cloud filtering is discussed and compared to the wet biases introduced by the clouds radiative effect if no filtering is done. This is done by means of a case study, and by means of a stochastic cloud database with representative statistics for midlatitude conditions. Both studied filter alternatives perform nearly equally well, but the alternative using 183.31±3.00 GHz as other channel is preferable, because that channel is less likely to see the Earth's surface than the one at 183.31±7.00 GHz. The consistent result of all case studies and for both filter alternatives is that both cloud wet bias and cloud filtering dry bias are modest for microwave data. The recommended strategy is to use the cloud filtered data as an estimate for the true all-sky UTH value, but retain the unfiltered data to have an estimate of the cloud induced uncertainty. The focus of the paper is on midlatitude data, since atmospheric data to test the filter for that case were readily available. The filter is expected to be applicable also to subtropical and tropical data, but should be further validated with case studies similar to the one presented here for those cases.

  • 71.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Milz, Mathias
    Eliasson, Salomon
    Upper tropospheric humidity and cloud ice: comparing global climate models and satellite observations2008Ingår i: 2008 European Geosciences Union General Assembly, Austria Center Vienna, Vienna (Austria), 13-18 Apr 2008, European Geosciences Union (EGU), 2008Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Upper tropospheric humidity (UTH) and cloud ice (measured as ice water content IWC or vertically integrated ice water path IWP) are parameters of the climate system on which current global climate models do not agree well. This is illustrated by intercomparing the models in the IPCC AR4 archive. It is then discussed, to what extent different satellite measurements agree on these parameters. The focus is on passive observations from different infrared (HIRS, IASI) and microwave (AMSU-B, HSB) sensors.

  • 72.
    Buehler, Stefan
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Östman, S.
    Luleå tekniska universitet.
    Melsheimer, C.
    Institute of Environmental Physics, University of Bremen.
    Holl, Gerrit
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Eliasson, Salomon
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    John, V.O.
    Met Office Hadley Centre, Exeter.
    Blumenstock, T.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Hase, F.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Ekgered, G.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Raffalski, U.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Nasuno, T.
    Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, Yokohama.
    Satho, M.
    Atmosphere and Ocean Research Institute, University of Tokyo.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mendrok, Jana
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A multi-instrument comparison of integrated water vapour measurements at a high latitude site2012Ingår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 12, nr 22, s. 10925-10943Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We compare measurements of integrated water vapour (IWV) over a subarctic site (Kiruna, Northern Sweden) from five different sensors and retrieval methods: Radiosondes, Global Positioning System (GPS), ground-based Fourier-transform infrared (FTIR) spectrometer, ground-based microwave radiometer, and satellite-based microwave radiometer (AMSU-B). Additionally, we compare also to ERA-Interim model reanalysis data. GPS-based IWV data have the highest temporal coverage and resolution and are chosen as reference data set. All datasets agree reasonably well, but the ground-based microwave instrument only if the data are cloud-filtered. We also address two issues that are general for such intercomparison studies, the impact of different lower altitude limits for the IWV integration, and the impact of representativeness error. We develop methods for correcting for the former, and estimating the random error contribution of the latter. A literature survey reveals that reported systematic differences between different techniques are study-dependent and show no overall consistent pattern. Further improving the absolute accuracy of IWV measurements and providing climate-quality time series therefore remain challenging problems.

  • 73.
    Carlsson, Ella
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Cold Mars2006Konferensbidrag (Övrigt vetenskapligt)
  • 74. Carlsson, Ella
    et al.
    Brain, D.
    Space Science Laboratory, University of California, Berkeley.
    Luhmann, J.
    Space Science Laboratory, University of California, Berkeley.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Grigoriev, Alexander
    Nilsson, H.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Lundin, R.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Influence of IMF draping direction and crustal magnetic field location on Martian ion beams2008Ingår i: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 56, nr 6, s. 861-867Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Data from the Ion Mass Analyzer (IMA) sensor of the ASPERA-3 instrument suite onboard Mars Express and data from the Magnetometer/Electron Reflectometer (MAG/ER) on Mars Global Surveyor have been analyzed to determine whether ion beam events (IBEs) are correlated with the direction of the draped interplanetary magnetic field (IMF) or the proximity of strong crustal magnetic fields to the subsolar point. We examined 150 IBEs and found that they are organized by IMF draping direction. However, no clear dependence on the subsolar longitude of the strongest magnetic anomaly is evident, making it uncertain whether crustal magnetic fields have an effect on the formation of the beams. We also examined data from the IMA sensor of the ASPERA-4 instrument suite on Venus Express and found that IBEs are observed at Venus as well, which indicates the morphology of the Martian and Venusian magnetotails are similar.

  • 75. Carlsson, Ella
    et al.
    Fedorov, A.
    Budnik, E.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Fredriksson, Sverker
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    First results from ASPERA-3 Ion Mass Analyzer (IMA) on CO2+ escape2005Konferensbidrag (Övrigt vetenskapligt)
  • 76.
    Castro, Juan Francisco Buenestado
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mier, Maria-Paz Zorzano
    Centro de Astrobiologia, INTA-CSIC, Madrid.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Liquid water at crater Gale, Mars2015Ingår i: Journal of Astrobiology and Outreach, ISSN 2332-2519, Vol. 3, nr 3, artikel-id 131Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Suspicion that Mars could have transient liquid water on its surface through deliquescence of salts to form aqueous solutions or brines is an old proposal whose inquiry was boosted by Phoenix Lander observations. It provided some images of what were claimed to be brines, the presence of which at its landing site was compatible with the atmospheric parameters and the composition of the soil observed. On the other hand, the so called Recurrent Slope Lineae (RSL) often imaged by orbiters, were considered as another clue pointing to the occurrence of the phenomenon, since it was thought that they might be caused by it. Now, Curiosity rover has performed the first in-situ multi-instrumental study on Mars’ surface, having collected the most comprehensive environmental data set ever taken by means of their instruments Rover Environmental Monitoring Station (REMS), Dynamic Albedo of Neutrons (DAN), and Sample Analysis at Mars (SAM). REMS is providing continuous and accurate measurements of the relative humidity and surface and air temperatures among other parameters, and DAN and SAM provide the water content of the regolith and the atmosphere respectively. Analysis of these data has allowed to establish the existence of a present day active water cycle between the atmosphere and the regolith, that changes according to daily and seasonal cycles, and that is mediated by the presence of brines during certain periods of each and every day. Importantly, the study shows that the conditions for the occurrence of deliquescence are favourable even at equatorial latitudes where, at first, it was thought they were not due to the temperature and relative humidity conditions. This study provides new keys for the understanding of martian environment, and opens interesting lines of research and studies for future missions which may even have a bearing on extant microbial life.

  • 77.
    Castro, Juan Francisco Buenestado
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mier, Maria-Paz Zorzano
    Centro de Astrobiologia, INTA-CSIC, Madrid.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Planetary exploration; Mars on the scope2015Ingår i: Journal of Astrobiology and Outreach, ISSN 2332-2519, Vol. 3, nr 3, artikel-id 133Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This article summarizes a practical case of introduction to research and planetary exploration through the analysis of data from the Rover Environmental Monitoring Station (REMS), one of the ten scientific instruments on board the Curiosity rover of the Mars Science Laboratory (MSL), currently operating at the impact crater Gale, on Mars. It is the main aim of this work to show how the data that are publicly available at the Planetary Data System (PDS) can be used to introduce undergraduate students and the general public into the subject of surface exploration and the environment of Mars. In particular, the goal of this practice was to investigate and quantify the heat flux between the rover spacecraft and the Martian surface, the role of the atmosphere in this interaction, and its dependence with seasons, as well as to estimate the thermal contamination of the Martian ground produced by the rover. The ground temperature sensor (GTS) of the REMS instrument has measured in-situ, for the first time ever, the diurnal and seasonal variation of the temperature of the surface on Mars along the rover traverse. This novel study shows that the rover radiative heat flux varies between 10 and 22 W/m2 during the Martian year, which is more than 10% of the solar daily averaged insolation at the top of the atmosphere. In addition, it is shown that the radiative heat flux from the rover to the ground varies with the atmospheric dust load, being the mean annual amplitude of the diurnal variation of the surface temperature of 76 K, as a result of solar heating during the day and infrared cooling during the night. As a remarkable and unexpected outcome, it has been established that the thermal contamination produced by the rover alone induces, on average, a systematic shift of 7.5 K, which is indeed about 10% of the one produced by solar heating. This result may have implications for the design and operation of future surface exploration probes such as InSight.

  • 78.
    Charlton, J E
    et al.
    Sula systems.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Defer, E.
    L'Observatoire de Paris-LERMA.
    Prigent, C.
    L'Observatoire de Paris-LERMA.
    Moyna, B.
    Rutherford Appleton Laboratory.
    Lee, C.
    Met Office Hadley Centre, Exeter.
    Magt, P. De
    European Space Agency.
    Kangas, V.
    European Space Agency.
    A sub-millimetre wave airborne demonstrator for the observation of precipitation and ice clouds2010Ingår i: International Geoscience and Remote Sensing Symposium (IGARSS): Cape Town, South Africa, 12 - 17 July 2009, Piscataway, NJ: IEEE Communications Society, 2010, Vol. 3, s. 1023-1026Konferensbidrag (Refereegranskat)
    Abstract [en]

    Sub-millimetre remote sensing instruments can provide critical information on cirrus clouds and an alternative way of measuring precipitation with a much smaller antenna than those which microwave sensors currently use. Two satellite concepts CIWSIR and GOMAS were proposed as ESA Earth Explorer missions; these were not funded, however they were recommended for an aircraft demonstrator. ESA studies have been performed to identify the optimum instrument and platform to demonstrate these satellite concepts. This paper reports on one of these preparatory activities; the design of a sub-millimetre wave airborne demonstrator for both ice cloud and precipitation observations which will be able to prove the feasibility of the scientific principles of both satellite missions. The paper will describe the derivation of the demonstrator requirements, consideration of the available platform and instrument options, the design of the selected concept, performance prediction and the outline of a proof of concept flight campaign. It will present the outcome of the study which describes a demonstrator design based upon the new Met Office International Sub-Millimetre Airborne Radiometer (ISMAR).

  • 79.
    Chauhan, Swarup
    et al.
    Forschungszentrum Karlsruhe.
    Höpfner, M.
    Stiller, G.P.
    Clarmann, T. von
    Funke, B.
    Glatthor, N.
    Grabowski, U.
    Linden, A.
    Kellmann, S.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Steck, T.
    Fischer, H.
    Froidevaux, L.
    Lambert, A.
    Santee, M. L.
    Schwartz, M.
    Read, W.G.
    Livesey, N.
    MIPAS reduced spectral resolution UTLS-1 mode measurements of temperature, O3, HNO3, N2O, H2O and relative humidity over ice: retrievals and comparison to MLS2009Ingår i: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, nr 2, s. 337-353Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    During several periods since 2005 the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat has performed observations dedicated to the region of the upper troposphere/lower stratosphere (UTLS). For the duration of November/December 2005 global distributions of temperature and several trace gases from MIPAS UTLS-1 mode measurements have been retrieved using the IMK/IAA (Institut für Meteorologie und Klimaforschung/Instituto de Astrofísica de Andalucía) scientific processor. In the UTLS region a vertical resolution of 3 km for temperaure, 3 to 4 km for H2O, 2.5 to 3 km for O3, 3.5 km for HNO3 and 3.5 to 2.5 km for N2O has been achieved. The retrieved temperature, H2O, O3, HNO3, N2O, and relative humidity over ice are intercompared with the Microwave Limb Sounder (MLS/Aura) v2.2 data in the pressure range 316 to 0.68 hPa, 316 to 0.68 hPa, 215 to 0.68 hPa, 215 to 3.16 hPa, 100 to 1 hPa and 316 to 10 hPa, respectively. In general, MIPAS and MLS temperatures are biased within ±4 K over the whole pressure and latitude range. Systematic, latitude-independent differences of −2 to −4 K (MIPAS-MLS) at 121 hPa are explained by previously observed biases in the MLS v2.2 temperature retrievals. Temperature differences of −4 K up to 12 K above 10.0 hPa are present both in MIPAS and MLS with respect to ECMWF (European Centre for Medium-Range Weather Forecasts) and are likely due to deficiencies of the ECMWF analysis data. MIPAS and MLS stratospheric volume mixing ratios (vmr) of H2O are biased within ±1 ppmv, with indication of oscillations between 146 and 26 hPa in the MLS dataset. Tropical upper tropospheric values of relative humidity over ice measured by the two instruments differ by ±20% in the pressure range ~146 to 68 hPa. These differences are mainly caused by the MLS temperature biases. Ozone mixing ratios agree within 0.5 ppmv (10 to 20%) between 68 and 14 hPa. At pressures smaller than 10 hPa, MIPAS O3 vmr are higher than MLS by an average of 0.5 ppmv (10%). General agreement between MIPAS and MLS HNO3 is within the range of −1.0 (−10%) to 1.0 ppbv (20%). MIPAS HNO3 is 1.0 ppbv (10%) higher compared to MLS between 46 hPa and 10 hPa over the Northern Hemisphere. Over the tropics at 31.6 hPa MLS shows a low bias of more than 1 ppbv (>50%). In general, MIPAS and MLS N2O vmr agree within 20 to 40 ppbv (20 to 40%). Differences in the range between 100 to 21 hPa are attributed to a known 20% positive bias in MIPAS N2O data.

  • 80.
    Chen, Fengxiang
    et al.
    Department of Automation, Shanghai Jiaotong University.
    Chen, Lin
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zhang, Weidong
    Department of Automation, Shanghai Jiaotong University.
    Robust control of chaos in the Lorenz system with the variable structure control approach2008Ingår i: Physica scripta. T, ISSN 0281-1847, Vol. 77, nr 2Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    This paper is concerned with the robust control for a class of the uncertain Lorenz system subject to sector nonlinear input. Based on rigorous mathematical analysis, the proposed variable structure controller can drive the system state exactly to a class of a specific point or in the predictable neighborhood of an arbitrary desired point in the state space even with mismatch uncertainties. Moreover, the controller ensures that one of the error components can approach zero as time approaches infinity. Finally, numerical simulation results show the effectiveness of our work.

  • 81.
    Chen, Fengxiang
    et al.
    Department of Automation, Shanghai Jiaotong University.
    Chen, Lin
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zhang, Weidong
    Department of Automation, Shanghai Jiaotong University.
    Stabilization of parameters perturbation chaotic system via adaptive backstepping technique2008Ingår i: Applied Mathematics and Computation, ISSN 0096-3003, E-ISSN 1873-5649, Vol. 200, nr 1, s. 101-109Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The work of Yassen [M.T. Yassen, Chaos control of chaotic dynamical systems using backstepping design, Chaos Soliton Fract. 27 (2006) 537-548] which mainly investigated the stabilization problem for a class of chaotic systems without the parameters perturbation. This paper is concerned with stabilization problem for a class of parameters perturbation chaotic systems via both backstepping design method and adaptive technique. The proposed controllers can guarantee that the parameters perturbation systems will be stabilized at a fixed bounded point. Furthermore, the paper also proposes controllers to stabilize the uncertain chaotic system at equilibrium point with only backstepping design method. Finally, numerical simulations are given to illustrate the effectiveness of the proposed controllers

  • 82.
    Chen, Fengxiang
    et al.
    Shanghai Jiao Tong University.
    Wang, Wei
    Shanghai Jiao Tong University.
    Chen, Lin
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Zhang, Weidong
    Shanghai Jiao Tong University.
    Adaptive chaos synchronization based on LMI technique2007Ingår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 75, nr 3, s. 285-288Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The paper investigates the robust synchronization for two identical uncertain chaotic systems with different parameters perturbation and external disturbances. Based on Lyapunov stability theory, linear matrix inequality (LMI) techniques and adaptive techniques, a novel controller is proposed. With the resulting controller, global asymptotical synchronization between two identical uncertain chaotic systems is achieved. Finally, a Lorenz system is given as an example to verify the effectiveness of the proposed controller.

  • 83.
    Chhabra, Robin
    et al.
    Department of Mathematics and Statistics, University of Calgary.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A linguistic approach to concurrent design2015Ingår i: Journal of Intelligent & Fuzzy Systems, ISSN 1064-1246, E-ISSN 1875-8967, Vol. 28, nr 5, s. 1985-2001Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper outlines a concurrent design methodology for multidisciplinary systems, which employs tools of fuzzy theory for the tradeoff in the design space. This methodology enhances communication between designers from various disciplines through introducing the universal notion of satisfaction and expressing the behaviour of multidisciplinary systems using the notion of energy. It employs fuzzy rule-bases, membership functions and parametric connectives in fuzzy logic to formalize subjective aspects of design, resulting in a two-phase simplification of the multi-objective constrained optimization of a design process. The methodology attempts to find a pareto-optimal solution for the design problem. In the primary phase of the methodology, a fuzzy-logic model is utilized to identify a region in the design space that contains the pareto-optimal design state, and a proper initial state is suggested for the optimization in the secondary phase, where the pareto-optimal solution is found. Finally, the impact of the designer's subjective attitude on the design is adjusted based on a system performance by utilizing an energy-based model of multidisciplinary systems. As an application, it is shown that the design of a five-degree-of-freedom industrial robot manipulator can be enhanced by using the methodology.

  • 84.
    Chhabra, Robin
    et al.
    MacDonald, Dettwiler and Associates Ltd., Brampton.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    A Unified Approach to Input-output Linearization and Concurrent Control of Underactuated Open-chain Multi-body Systems with Holonomic and Nonholonomic Constraints2016Ingår i: Journal of dynamical and control systems, ISSN 1079-2724, E-ISSN 1573-8698, Vol. 22, nr 1, s. 129-168Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a unified geometric framework to input-output linearization of open-chain multi-body systems with symmetry in their reduced phase space. This leads us to an output tracking controller for a class of underactuated open-chain multi-body systems with holonomic and nonholonomic constraints. We consider the systems with multi-degree-of-freedom joints and possibly with non-zero constant total momentum (in the holonomic case). The examples of these systems are free-base space manipulators and mobile manipulators. We first formalize the control problem, and rigorously state an output tracking problem for such systems. Then, we introduce a geometrical definition of the end-effector pose and velocity error. The main contribution of this paper is reported in Section 5, where we solve for the input-output linearization of the highly nonlinear problem of coupled manipulator and base dynamics subject to holonomic and nonholonomic constraints. This enables us to design a coordinate-independent controller, similar to a proportional-derivative with feed-forward, for concurrently controlling a free-base, multi-body system. Finally, by defining a Lyapunov function, we prove in Theorem 3 that the closed-loop system is exponentially stable. A detailed case study concludes this paper.

  • 85.
    Chhabra, Robin
    et al.
    Institute for Aerospace Studies, University of Toronto, MacDonald, Dettwiler and Associates Ltd., Brampton.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Symplectic reduction of holonomic open-chain multi-body systems with constant momentum2015Ingår i: Journal of Geometry and Physics, ISSN 0393-0440, E-ISSN 1879-1662, Vol. 89, s. 82-110Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a two-step symplectic geometric approach to the reduction of Hamilton's equation for open-chain, multi-body systems with multi-degree-of-freedom holonomic joints and constant momentum. First, symplectic reduction theorem is revisited for Hamiltonian systems on cotangent bundles. Then, we recall the notion of displacement subgroups, which is the class of multi-degree-of-freedom joints considered in this paper. We briefly study the kinematics of open-chain multi-body systems consisting of such joints. And, we show that the relative configuration manifold corresponding to the first joint is indeed a symmetry group for an open-chain multi-body system with multi-degree-of-freedom holonomic joints. Subsequently using symplectic reduction theorem at a non-zero momentum, we express Hamilton's equation of such a system in the symplectic reduced manifold, which is identified by the cotangent bundle of a quotient manifold. The kinetic energy metric of multi-body systems is further studied, and some sufficient conditions are introduced, under which the kinetic energy metric is invariant under the action of a subgroup of the configuration manifold. As a result, the symplectic reduction procedure for open-chain, multi-body systems is extended to a two-step reduction process for the dynamical equations of such systems. Finally, we explicitly derive the reduced dynamical equations in the local coordinates for an example of a six-degree-of-freedom manipulator mounted on a spacecraft, to demonstrate the results of this paper. (C) 2014 Elsevier B.V. All rights reserved.

  • 86.
    Chhabra, Robin
    et al.
    MacDonald, Dettwiler and Ass. Ltd.
    Emami, Reza
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Karshon, Yael
    Department of Mathematics, University of Toronto.
    Reduction of Hamiltonian Mechanical Systems With Affine Constraints: A Geometric Unification2017Ingår i: Journal of Computational and Nonlinear Dynamics, ISSN 1555-1415, E-ISSN 1555-1423, Vol. 12, nr 2, artikel-id 021007Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a geometrical approach to the dynamical reduction of a class of constrained mechanical systems. The mechanical systems considered are with affine nonholonomic constraints plus a symmetry group. The dynamical equations are formulated in a Hamiltonian formalism using the Hamilton-d'Alembert equation, and constraint forces determine an affine distribution on the configuration manifold. The proposed reduction approach consists of three main steps: (1) restricting to the constrained submanifold of the phase space, (2) quotienting the constrained submanifold, and (3) identifying the quotient manifold with a cotangent bundle. Finally, as a case study, the dynamical reduction of a two-wheeled rover on a rotating disk is detailed. The symmetry group for this example is the relative configuration manifold of the rover with respect to the inertial space. The proposed approach in this paper unifies the existing reduction procedures for symmetric Hamiltonian systems with conserved momentum, and for Chaplygin systems, which are normally treated separately in the literature. Another characteristic of this approach is that although it tracks the structure of the equations in each reduction step, it does not insist on preserving the properties of the system. For example, the resulting dynamical equations may no longer correspond to a Hamiltonian system. As a result, the invariance condition of the Hamiltonian under a group action that lies at the heart of almost every reduction procedure is relaxed

  • 87.
    Clarmann, T. von
    et al.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Glatthor, N.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Koukouli, M.E.
    Laboratory of Atmospheric Physics, Physics Department, Aristotle University of Thessaloniki.
    Stiller, G.P.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Funcke, B.
    Instituto de Astrofísica de Andalucía CSIC, Granada.
    Grabowski, U.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Höpfner, M.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Kellmann, S.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Linden, A.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Steck, T.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Fischer, H.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    MIPAS measurements of upper tropospheric C2H6 and O3 during the southern hemispheric biomass burning season in 20032007Ingår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 7, nr 22, s. 5861-5872Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Under cloud free conditions, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) provides measurements of spectrally resolved limb radiances down to the upper troposphere. These are used to infer global distributions of mixing ratios of atmospheric constituents in the upper troposphere and the stratosphere. From 21 October to 12 November 2003, MIPAS observed enhanced amounts of upper tropospheric C2H6 (up to about 400 pptv) and ozone (up to about 80 ppbv). The absolute values of C2H6, however, may be systematically low by about 30% due to uncertainties of the spectroscopic data used. By means of trajectory calculations, the enhancements observed in the southern hemisphere are, at least partly, attributed to a biomass burning plume, which covers wide parts of the Southern hemisphere, from South America, the Atlantic Ocean, Africa, the Indian Ocean to Australia. The chemical composition of the part of the plume-like pollution belt associated with South American fires, where rainforest burning is predominant appears different from the part of the plume associated with southern African savanna burning. In particular, African savanna fires lead to a larger ozone enhancement than equatorial American fires. In this analysis, MIPAS observations of high ozone were disregarded where low CFC-11 (below 245 pptv) was observed, because this hints at a stratospheric component in the measured signal. Different type of vegetation burning (flaming versus smouldering combustion) has been identified as a candidate explanation for the different plume compositions

  • 88.
    Cockell, Charles S.
    et al.
    UK Centre for Astrobiology, SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh, Midlothian, UK.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. UK Centre for Astrobiology, SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh, Midlothian, UK; Instituto Andaluz de Ciencias de la Tierra (UGR-CSIC), Granada, Spain .
    Zorzano, Maria-Paz
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Centro de Astrobiología (CSIC-INTA), Torrejon de Ardoz, 28850 Madrid, Spain.
    Bhardwaj, Anshuman
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Soria-Salinas, Álvaro
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mathanla, Thasshwin
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Israel Nazarious, Miracle
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Vakkada Ramachandran, Abhilash
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Suckling, Barbara
    Boulby Underground Laboratory, Boulby, UK.
    Subsurface scientific exploration of extraterrestrial environments (MINAR 5):: analogue science, technology and education inthe Boulby Mine, UK2018Ingår i: International Journal of Astrobiology, ISSN 1473-5504, E-ISSN 1475-3006Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The deep subsurface of other planetary bodies is of special interest for robotic and human exploration. The subsurface provides access to planetary interior processes, thus yielding insights into planetary formation and evolution. On Mars, the subsurface might harbour the most habitable conditions. In the context of human exploration, the subsurface can provide refugia for habitation from extreme surface conditions. We describe the fifth Mine Analogue Research (MINAR 5) programme at 1 km depth in the Boulby Mine, UK in collaboration with Spaceward Bound NASA and the Kalam Centre, India, to test instruments and methods for the robotic and human exploration of deep environments on the Moon and Mars. The geological context in Permian evaporites provides an analogue to evaporitic materials on other planetary bodies such as Mars. A wide range of sample acquisition instruments (NASA drills, Small Planetary Impulse Tool (SPLIT) robotic hammer, universal sampling bags), analytical instruments (Raman spectroscopy, Close-Up Imager, Minion DNA sequencing technology, methane stable isotope analysis, biomolecule and metabolic life detection instruments) and environmental monitoring equipment (passive air particle sampler, particle detectors and environmental monitoring equipment) was deployed in an integrated campaign. Investigations included studying the geochemical signatures of chloride and sulphate evaporitic minerals, testing methods for life detection and planetary protection around human-tended operations, and investigations on the radiation environment of the deep subsurface. The MINAR analogue activity occurs in an active mine, showing how the development of space exploration technology can be used to contribute to addressing immediate Earth-based challenges. During the campaign, in collaboration with European Space Agency (ESA), MINAR was used for astronaut familiarization with future exploration tools and techniques. The campaign was used to develop primary and secondary school and primary to secondary transition curriculum materials on-site during the campaign which was focused on a classroom extra vehicular activity simulation.

  • 89.
    Cockell, C.S.
    et al.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Bush, T.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Bryce, C.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Direito, S.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Fox-Powell, M.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Harrison, J.P
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Lammer, H.
    Austrian Academy of Sciences, Space Research Institute, Graz.
    Landenmark, H.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Nicholson, N.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Noack, L.
    Department of Reference Systems and Planetology, Royal Observatory of Belgium, Brussels.
    O'Malley-James, J.
    School of Physics and Astronomy, University of St Andrews, St Andrews.
    Payler, S.J.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Rushby, A.
    Centre for Ocean and Atmospheric Science (COAS), School of Environmental Sciences, University of East Anglia, Norwich.
    Samuels, T.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Schwendner, P.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Wadsworth, J.
    UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh.
    Mier, Maria-Paz Zorzano
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Habitability: a review2016Ingår i: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 16, nr 1, s. 89-117Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Habitability is a widely used word in the geoscience, planetary science, and astrobiology literature, but what does it mean? In this review on habitability, we define it as the ability of an environment to support the activity of at least one known organism. We adopt a binary definition of “habitability” and a “habitable environment.” An environment either can or cannot sustain a given organism. However, environments such as entire planets might be capable of supporting more or less species diversity or biomass compared with that of Earth. A clarity in understanding habitability can be obtained by defining instantaneous habitability as the conditions at any given time in a given environment required to sustain the activity of at least one known organism, and continuous planetary habitability as the capacity of a planetary body to sustain habitable conditions on some areas of its surface or within its interior over geological timescales. We also distinguish between surface liquid water worlds (such as Earth) that can sustain liquid water on their surfaces and interior liquid water worlds, such as icy moons and terrestrial-type rocky planets with liquid water only in their interiors. This distinction is important since, while the former can potentially sustain habitable conditions for oxygenic photosynthesis that leads to the rise of atmospheric oxygen and potentially complex multicellularity and intelligence over geological timescales, the latter are unlikely to. Habitable environments do not need to contain life. Although the decoupling of habitability and the presence of life may be rare on Earth, it may be important for understanding the habitability of other planetary bodies

  • 90.
    Conte, Davide
    et al.
    The Pennsylvania State University.
    Budzyń, Dorota
    Wrocław Institute of Technology.
    Burgoyne, Hayden
    California Institute of Technology.
    Di Carlo, Marilena
    University of Strathclyde.
    Fries, Dan
    University of Strathclyde.
    Grulich, Maria
    Technische Universität München.
    Heizmann, Sören
    Universität Stuttgart.
    Jethani, Henna
    University of Colorado, Boulder.
    Lapôtre, Mathieu
    California Institute of Technology.
    Roos, Tobias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Serrano Castillo, Encarnación
    Università di Bologna.
    Sherrmann, Marcel
    Universität Stuttgart.
    Vieceli, Rhiannon
    The Pennsylvania State University.
    Wilson, Lee
    California Institute of Technology.
    Wynard, Christopher
    University of Illinois Urbana-Champaign.
    Dees, Stacy
    National Institute of Aerospace .
    Innovative mars global international exploration (IMaGInE) mission2016Ingår i: AIAA Space and Astronautics Forum and Exposition, SPACE 2016, American Institute of Aeronautics and Astronautics, 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents the conceptual design of the IMaGInE (Innovative Mars Global International Exploration) Mission whose mission objectives are to deliver a crew of four astronauts to the surface of Deimos and a robotic exploration mission to Phobos for approx-imately 343 days during the years 2031 and 2032, perform surface excursions, technology demonstrations, and In Situ Resource Utilization (ISRU) of the Martian moons as well as site reconnaissance for future human exploration of Mars. This is the winning mis-sion design of the 2016 Revolutionary Aerospace Systems Concepts-Academic Linkage (RASC-AL) competition, awarded with the "Best in Theme," "Best Overall," and "Pio-neering Exceptional Achievement Concept Honor (PEACH)" prizes. This competition was sponsored by NIA and NASA

  • 91.
    Conte, Davide
    et al.
    The Pennsylvania State University.
    Di Carlo, Marilena
    University of Strathclyde.
    Budzyń, Dorota
    ESA/EAC, Linder Höhe, Cologne.
    Burgoyne, Hayden
    Analytical Space, Inc., Boston.
    Fries, Dan
    Georgia Institute of Technology.
    Grulich, Maria
    ESA/ESTEC.
    Heizmann, Sören
    Universität Stuttgart.
    Jethani, Henna
    Blue Origin.
    Lapôtre, Mathieu
    California Institute of Technology.
    Roos, Tobias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Castillo, Encarnación Serrano
    Università di Bologna.
    Scherrmann, Marcel
    ESA/ESTEC.
    Vieceli, Rhiannon
    New Mexico Institute of Mining and Technology.
    Wilson, Lee
    California Institute of Technology.
    Wynard, Christopher
    NASA Johnson Space Center.
    Advanced concept for a crewed mission to the martian moons2017Ingår i: Acta Astronautica, ISSN 0094-5765, E-ISSN 1879-2030, Vol. 139, s. 545-563Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents the conceptual design of the IMaGInE (Innovative Mars Global International Exploration) Mission. The mission's objectives are to deliver a crew of four astronauts to the surface of Deimos and perform a robotic exploration mission to Phobos. Over the course of the 343 day mission during the years 2031 and 2032, the crew will perform surface excursions, technology demonstrations, In Situ Resource Utilization (ISRU) of the Martian moons, as well as site reconnaissance for future human exploration of Mars. This mission design makes use of an innovative hybrid propulsion concept (chemical and electric) to deliver a relatively low-mass reusable crewed spacecraft (approximately 100 mt) to cis-martian space. The crew makes use of torpor which minimizes launch payload mass. Green technologies are proposed as a stepping stone towards minimum environmental impact space access. The usage of beamed energy to power a grid of decentralized science stations is introduced, allowing for large scale characterization of the Martian environment. The low-thrust outbound and inbound trajectories are computed through the use of a direct method and a multiple shooting algorithm that considers various thrust and coast sequences to arrive at the final body with zero relative velocity. It is shown that the entire mission is rooted within the current NASA technology roadmap, ongoing scientific investments and feasible with an extrapolated NASA Budget. The presented mission won the 2016 Revolutionary Aerospace Systems Concepts - Academic Linkage (RASC-AL) competition.

  • 92.
    Davis, C. P.
    et al.
    University of Edinburgh, Institute of Atmospheric and Environmental Science.
    Evans, K. F.
    University of Colorado, Department of Atmosphere and Oceanic Sciences.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Wu, D. L.
    California Institute of Technology, Jet Propulsion Laboratory.
    Pumphrey, H. C.
    University of Edinburgh, Institute of Atmospheric and Environmental Science.
    3-D polarised simulations of space-borne passive mm/sub-mm midlatitude cirrus observations: a case study2006Ingår i: Atmospheric Chemistry and Physics Discussions, ISSN 1680-7367, E-ISSN 1680-7375, Vol. 6, s. 12701-12728Artikel i tidskrift (Övrigt vetenskapligt)
  • 93.
    Davis, Cory
    et al.
    University of Edinburgh, Institute of Atmospheric and Environmental Science.
    Evans, K. F.
    Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder.
    Buehler, Stefan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Wu, D. L.
    Jet Propulsion Laboratory, California Institute of Technology, Pasadena.
    Pumphrey, H. C.
    University of Edinburgh, Institute of Atmospheric and Environmental Science.
    3-D polarised simulations of space-borne passive mm/sub-mm midlatitude cirrus observations: a case study2007Ingår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 7, nr 15, s. 4149-4158Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Global observations of ice clouds are needed to improve our understanding of their impact on earth's radiation balance and the water-cycle. Passive mm/sub-mm has some advantages compared to other space-borne cloud-ice remote sensing techniques. The physics of scattering makes forward radiative transfer modelling for such instruments challenging. This paper demonstrates the ability of a recently developed RT code, ARTS-MC, to accurately simulate observations of this type for a variety of viewing geometries corresponding to operational (AMSU-B, EOS-MLS) and proposed (CIWSIR) instruments. ARTS-MC employs an adjoint Monte-Carlo method, makes proper account of polarisation, and uses 3-D spherical geometry. The actual field of view characteristics for each instrument are also accounted for. A 3-D midlatitude cirrus scenario is used, which is derived from Chilbolton cloud radar data and a stochastic method for generating 3-D ice water content fields. These demonstration simulations clearly demonstrate the beamfilling effect, significant polarisation effects for non-spherical particles, and also a beamfilling effect with regard to polarisation.

  • 94.
    Delgado-Bonal, A.
    et al.
    Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR).
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Human vision is determined based on information theory2016Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, artikel-id 36038Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is commonly accepted that the evolution of the human eye has been driven by the maximum intensity of the radiation emitted by the Sun. However, the interpretation of the surrounding environment is constrained not only by the amount of energy received but also by the information content of the radiation. Information is related to entropy rather than energy. The human brain follows Bayesian statistical inference for the interpretation of visual space. The maximization of information occurs in the process of maximizing the entropy. Here, we show that the photopic and scotopic vision absorption peaks in humans are determined not only by the intensity but also by the entropy of radiation. We suggest that through the course of evolution, the human eye has not adapted only to the maximum intensity or to the maximum information but to the optimal wavelength for obtaining information. On Earth, the optimal wavelengths for photopic and scotopic vision are 555 nm and 508 nm, respectively, as inferred experimentally. These optimal wavelengths are determined by the temperature of the star (in this case, the Sun) and by the atmospheric composition.

  • 95.
    Delgado-Bonal, Alfonso
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Evaluation of the Atmospheric Chemical Entropy Production of Mars2015Ingår i: Entropy, ISSN 1099-4300, E-ISSN 1099-4300, Vol. 17, nr 7, s. 5047-5062Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thermodynamic disequilibrium is a necessary situation in a system in which complex emergent structures are created and maintained. It is known that most of the chemical disequilibrium, a particular type of thermodynamic disequilibrium, in Earth's atmosphere is a consequence of life. We have developed a thermochemical model for the Martian atmosphere to analyze the disequilibrium by chemical reactions calculating the entropy production. It follows from the comparison with the Earth atmosphere that the magnitude of the entropy produced by the recombination reaction forming O 3 (O + O 2 + CO 2 O 3 + CO 2) in the atmosphere of the Earth is larger than the entropy produced by the dominant set of chemical reactions considered for Mars, as a consequence of the low density and the poor variety of species of the Martian atmosphere. If disequilibrium is needed to create and maintain self-organizing structures in a system, we conclude that the current Martian atmosphere is unable to support large physico-chemical structures, such as those created on Earth.

  • 96.
    Delgado-Bonal, Alfonso
    et al.
    Centro de Astrobiologia, INTA-CSIC, Madrid.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Solar cell temperature on Mars2015Ingår i: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 118, s. 74-79Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The operating temperature of a solar cell determines its efficiency and performance. This temperature depends on the materials used to build the cell but also on the environmental variables surrounding it (i.e., radiation, ambient temperature, wind speed and humidity). Several equations have been proposed to calculate this temperature, depending on these variables. Also, for Earth conditions, simplifiedequations have been developed, but are not valid for other planets, as Mars, where the environmental conditions are extremely different.In this paper, we develop a simplified equation to calculate the temperature of a solar cell under Mars environmental conditions and discuss the effect that altitude and wind on Mars might have on the solar cell temperature. The correct determination of the operating temperature of the cell will help to optimize the design of the next solar cell powered rovers for the exploration of Mars.

  • 97.
    Delgado-Bonal, Alfonso
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Martín, Sandra Vázquez
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mier, Maria-Paz Zorzano
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Solar and wind exergy potentials for Mars2016Ingår i: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 102, s. 550-558Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The energy requirements of the planetary exploration spacecrafts constrain the lifetime of the missions, their mobility and capabilities, and the number of instruments onboard. They are limiting factors in planetary exploration. Several missions to the surface of Mars have proven the feasibility and success of solar panels as energy source. The analysis of the exergy efficiency of the solar radiation has been carried out successfully on Earth, however, to date, there is not an extensive research regarding the thermodynamic exergy efficiency of in-situ renewable energy sources on Mars. In this paper, we analyse the obtainable energy (exergy) from solar radiation under Martian conditions. For this analysis we have used the surface environmental variables on Mars measured in-situ by the Rover Environmental Monitoring Station onboard the Curiosity rover and from satellite by the Thermal Emission Spectrometer instrument onboard the Mars Global Surveyor satellite mission. We evaluate the exergy efficiency from solar radiation on a global spatial scale using orbital data for a Martian year; and in a one single location in Mars (the Gale crater) but with an appreciable temporal resolution (1 h). Also, we analyse the wind energy as an alternative source of energy for Mars exploration and compare the results with those obtained on Earth. We study the viability of solar and wind energy station for the future exploration of Mars, showing that a small square solar cell of 0.30 m length could maintain a meteorological station on Mars. We conclude that the low density of the atmosphere of Mars is responsible of the low thermal exergy efficiency of solar panels. It also makes the use of wind energy uneffective. Finally, we provide insights for the development of new solar cells on Mars.

  • 98.
    Delgado-Bonal, Alfonso
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Martin-Torres, Javier
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Mier, Maria-Paz Zorzano
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Martian Top of the Atmosphere 10–420 nm spectral irradiance database and forecast for solar cycle 242016Ingår i: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 134, s. 228-235Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ultraviolet radiation from 10 to 420 nm reaching Mars Top of the Atmosphere (TOA) and surface is important in a wide variety of fields such as space exploration, climate modeling, and spacecraft design, as it has impact in the physics and chemistry of the atmosphere and soil. Despite the existence of databases for UV radiation reaching Earth TOA, based in space-borne instrumentation orbiting our planet, there is no similar information for Mars. Here we present a Mars TOA UV spectral irradiance database for solar cycle 24 (years 2008–2019), containing daily values from 10 to 420 nm. The values in this database have been computed using a model that is fed by the Earth-orbiting Solar Radiation and Climate Experiment (SORCE) data. As the radiation coming from the Sun is not completely isotropic, in order to eliminate the geometrically related features but being able to capture the general characteristics of the solar cycle stage, we provide 3-, 7- and 15-days averaged values at each wavelength. Our database is of interest for atmospheric modeling and spectrally dependent experiments on Mars, the analysis of current and upcoming surface missions (rovers and landers) and orbiters in Mars. Daily values for the TOA UV conditions at the rover Curiosity location, as well as for the NASA Insight mission in 2016, and ESA/Russia ExoMars mission in 2018 are provided.

  • 99.
    Dhanaya, M.B.
    et al.
    Space Physics Laboratory, Vikram Sarabhai Space Center, Trivandrum.
    Bhardwaj, A.
    Space Physics Laboratory, Vikram Sarabhai Space Center, Trivandrum.
    Futaana, Y.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Fatemi, Shahab
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Holmström, M.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Barabash, Stas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Wieser, M.
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Wurz, P.
    Physikalisches Institut, University of Bern.
    Thampi, R.S.
    Space Physics Laboratory, Vikram Sarabhai Space Center, Trivandrum.
    Proton entry into the near-lunar plasma wake for magnetic field aligned flow2013Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 40, nr 2, s. 2913-2917Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report the first observation of protons in the near-lunar (100–200 km from the surface) and deeper (near anti-subsolar point) plasma wake when the interplanetary magnetic field (IMF) and solar wind velocity (vsw) are parallel (aligned flow; angle between IMF and vsw≤10°). More than 98% of the observations during aligned flow condition showed the presence of protons in the wake. These observations are obtained by the Solar Wind Monitor sensor of the Sub-keV Atom Reflecting Analyser experiment on Chandrayaan-1. The observation cannot be explained by the conventional fluid models for aligned flow. Back tracing of the observed protons suggests that their source is the solar wind. The larger gyroradii of the wake protons compared to that of solar wind suggest that they were part of the tail of the solar wind velocity distribution function. Such protons could enter the wake due to their large gyroradii even when the flow is aligned to IMF. However, the wake boundary electric field may also play a role in the entry of the protons into the wake.

  • 100.
    Dieval, Catherine
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Solar wind ions inside the induced magnetosphere of Mars2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Ämnet för avhandlingen är analys och modellering av inflödet av solvindsjoner, H+ och He2+, genom Mars inducerade magnetosfär. Solvinden är ett flöde av laddade partiklar från Solen. Solvinden bär med sig ett magnetfält, det så kallade interplanetära magnetfältet (IMF). IMF packas ihop framför dagsidan av planeten innan det tar sig vidare mot nattsidan. Solvindsjoner kan vanligtvis inte passera denna magnetiska barriär som skapas då IMF packas ihop. Dock avslöjar in situ-observationer av rymdsonden Mars Express att nedåtflödande H+ och He2+ från solvinden ibland påträffas inuti Mars jonosfär, nedanför den magnetiska barriären. Gyroradierna hos solvindsjoner i shockregionen kan vara jämförbara med storleken av den magnetiska barriären over Mars dagsida och i vissa fall kan jonerna gyrera igenom barriären. Observationer från Mars Express används för att analysera H+ och He2+ som tar sig igenom den magnetiska barriären och ner i Mars jonosfär, vilken identifieras genom närvaron av jonosfäriska fotoelektroner. En fallstudie visar tecken på smalare energifördelningar av H+ (med energi ≥ solvindens energi), ju lägre rymdsonden tog sig. Från detta slutleder studien att den magnetiska barriären reflekterar H+ med lägre energi och förhindrar dem från att nå lägre altituder. Avhandlingen beskiver även en statistisk studie av inflödande H+, vilken indikerar att inflödet av H+ är sällsynt (observeras enbart under 3% av observationstiden över dagsidan) och bär i genomsnitt med sig 0.2% av partikelflödet som finns uppströms i solvinden. I en annan statistisk studie visar avhandlingen att inflödet av solvindsjonerna H+ och He2+ minskar ytterligare när Mars möter tryckpulser i solvinden. En möjlig förklaring är att den ökade masslastningen av magnetfältets av tunga planetära joner, då magnetfältet släpas genom jonosfären på lägre höjd, bromsar upp magnetfältet och orsakar ytterligare hoppackning av magnetfältet. Det gör den magnetiska barriären till ett mer effektivt hinder för inflödet av solvindsjoner. Vidare beskriver avhandlingen en modell för inflöde av H+ till Mars övre atmosfär genom att använda en hybridkod för Mars växelverkan med solvinden. Mönster i utbredningen av inflödet beror på energin hos H+, på källan till H+ (solvinden eller skapad från vätekoronan), och på altituden. Vissa egenskaper hos H+-fördelningarna återskapas av simuleringar, medan andra inte gör det, vilket tyder på en mer komplicerad fysik än i modellen. Avhandlingen beskriver också en modellstudie av transport av H+ , snabba H atomer, och He2+ genom atmosfären med en Direct Simulation Monte Carlo modell. Denna studie demonstrerar den avgörande roll som magnetfältet har i att bestämma energin som solvindsjoner avlämnar i den övre atmosfären. Till exempel reflekterade ett horisontellt magnetfält på 50 nT nästan allt H+, och förhindrade dessa partiklar från att avlämna sin energi på lägre altituder. Slutsatsen av avhandlingen är att även om vissa solvindsjoner tar sig igenom, så är den magnetiska barriären ett effektivt skydd av jonosfären mot infallande solvindsjoner.

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