| 1. |
- Muscheler, Raimund, et al.
(author)
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Long-term climate variations and solar effects
- 2003
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In: European Space Agency, (Special Publication) ESA SP. - 1609-042X .- 0379-6566. - 929092845X ; 535, s. 305-316
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Conference paper (peer-reviewed)abstract
- The cosmogenic radionuclides 14C, 10Be and 36Cl allow us to trace solar variability several tens of millennia back in time. Different methods of reconstructing past solar variability based on radionuclide concentrations measured in ice cores will be discussed. The similarity in the variability of measurements of solar magnetic activity and solar irradiance over the last 20 years makes cosmogenic radionuclides a promising tool for reconstructing the variability of solar irradiance in the past. The analysis of many well-dated, high-resolution climate records and comparison with radionuclide records clearly indicates that solar forcing plays an important role in climate change. However, the underlying mechanisms are still a matter of debate and the climate records do not yet show a conclusive picture.
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| 2. |
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| 3. |
- Dischler, Johann, et al.
(author)
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Predicted properties of eclipsing binaries observable by Gaia
- 2005
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In: European Space Agency, (Special Publication) ESA SP. - 1609-042X .- 0379-6566. ; 576, s. 569-572
-
Conference paper (peer-reviewed)abstract
- Using a population synthesis model we estimate the fraction of stars of different types that are likely to show eclipses, as a function of the period. The population model is based on the bse-code from Hurley et al. (2002) which is a rapid binary evolution code that include all common effects in close binaries such as mass transfer, tidal locking, wind etc. We use this to evolve millions of systems from original distributions in separation, mass and eccentricity, with ages between zero and 12 Gyr, to get a population of systems representative of our Galaxy. The binary data from our model are then analysed in order to, statistically, see how many eclipsing systems we should have. This is done with a simple model where we neglect limb-darkening and other complicating effects. Assuming a random distribution of the inclination angle the probability of an eclipse of a given depth, Am, can easily be calculated. Adding a reasonable fraction of true single stars, we can finally estimate the fraction of eclipsing binaries in limited areas of the HR-diagram, as a function of the period. A first comparison with observational data from the Hipparcos mission shows quite satisfying agreement, and extrapolation to Gaia should thus be a natural application. We find that Gaia will observe about 500 000 eclipsing binaries, this (surprisingly) small number arises from the fact that many eclipsing systems will not be detected by Gaia.
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| 4. |
- Dorch, S.B.F., et al.
(author)
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Dynamo action in M-dwarfs
- 2005
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In: ESA SP (Special Publication). - 1609-042X .- 0379-6566. ; 560, s. 515-517
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Conference paper (peer-reviewed)
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| 5. |
- Dravins, Dainis, et al.
(author)
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Wavelength shifts in solar-type spectra
- 2005
-
In: European Space Agency, (Special Publication) ESA SP. - 1609-042X .- 0379-6566. ; 560, s. 113-119
-
Conference paper (peer-reviewed)abstract
- Spectral-line displacements away from the wavelengths naively expected from the Doppler shift caused by stellar radial motion may originate as convective shifts (correlated velocity and brightness patterns in the photosphere), as gravitational redshifts, or perhaps be induced by wave motions. Absolute lineshifts, in the past studied only for the Sun, are now accessible also for other stars thanks to astrometric determination of stellar radial motion, and spectrometers with accurate wavelength calibration. Comparisons between spectroscopic apparent radial velocities and astrometrically determined radial motions reveal greater spectral blueshifts in F-type stars than in the Sun (as theoretically expected from their more vigorous convection), further increasing in A-type stars (possibly due to atmospheric shockwaves). Work is in progress to survey the spectra of the Sun and several solar-type stars for "unblended" photospheric lines of most atomic species with accurate laboratory wavelengths available. One aim is to understand the ultimate information content of stellar spectra, and in what detail it will be feasible to verify models of stellar atmospheric hydrodynamics. These may predict bisectors and shifts for widely different classes of lines, but there will not result any comparison with observations if such lines do not exist in real spectra, or are too blended for meaningful measurement. An important near-future development to enable a further analysis of stellar surface structure will be the study of wavelength variations across spatially resolved stellar disks, e.g., the center-to-limb wavelength changes along a stellar diameter, and their spatially resolved time variability.
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| 6. |
- Johansson, Anders J
(author)
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Performance measures of implant antennas
- 2006
-
In: European Space Agency, (Special Publication) ESA SP. - 1609-042X .- 0379-6566. ; 626 SP
-
Conference paper (peer-reviewed)abstract
- Modern electronic medical implants have reached a high degree of complexity. This has increased the demands on the communication link with the implant, both regarding the bandwidth and the communication distance. A medical communication system at RF frequencies has been standardised, the Medical Implant Communication System (MICS), which use a frequency allocation of 402 - 405 MHz. This frequency band is allocated for implant use both and the US and in the EU. The EIRP is limited to -16 dBm in order to reduce the interference to existing users of the same frequency band. This low EIRP makes it necessary to have reasonable effective antennas in the implants in order to get a benefit form the switch from the classical inductive link to RF. The normal performance measures of antennas have to be modified when applied to implant antennas. The reflection coefficient S11 and the VSWR are straightforward to use also in the implant case. But the gain definition is only valid in a lossless medium. This is not a problem for the implanted antenna, as it is placed in a finite body, i.e. the patient. The implant and the body carrying it will act as one larger antenna, and will have a measurable gain according to the classic definition. The drawback is that the gain will depend heavily on the size and shape of the body, which makes it hard to give a generic value for the gain from a certain antenna. The type of antenna and the amount of isolation around the antenna will influence the amount of nearfield losses, and thus the efficiency. There is a modification of the efficiency measure which solves the problem of the gain definition in an infinite lossy medium [the]. This efficiency measure is a candidate for a quality measure of implanted antennas. The efficiency of an antenna in an infinite lossy material is evaluated by calculating the integral of the Poynting vector over a closed surface in the far zone of the antenna.
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| 7. |
- Jørgensen, Bjarne Rosenkilde, et al.
(author)
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Determination of star formation histories from gaia-type photometric and astrometric survey data
- 2005
-
In: European Space Agency, (Special Publication) ESA SP. - 0379-6566 .- 1609-042X. ; 576, s. 171-173
-
Conference paper (peer-reviewed)abstract
- To understand the evolution of the Milky Way Galaxy requires detailed knowledge of the star formation history of various populations. The vast amounts of photometric and astrometric data provided by the Gaia mission give unprecedented opportunities in this area. The relationships between the observed data and the ages of stars are however complex and highly non-linear and great care must be taken in analyzing the data. We describe a Bayesian approach to calculate the star formation rate (SFR) from astrophysical data, using a genetic algorithm to solve the basic integral equation. We present simulations showing that the method is capable of resolving structures in the SFR that cannot be seen from a distribution of the individually estimated stellar ages.
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| 8. |
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| 9. |
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| 10. |
- Lindegren, Lennart
(author)
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The astrometric instrument of Gaia: Principles
- 2005
-
In: European Space Agency, (Special Publication) ESA SP. - 1609-042X .- 0379-6566. ; 576, s. 29-34
-
Conference paper (peer-reviewed)abstract
- Compared with Hipparcos, Gaia will give an enormous improvement in accuracy, completeness and number of stars: about two orders of magnitude in accuracy, four orders in number, and a completeness limit that is 12 magnitudes fainter. How is all this possible? The answer is: by a combination of many factors, the most important being bigger and more efficient detectors, and bigger optics. The method of astrometric measurements by Gaia is described from first principles, and the fundamental limitations explained in terms of physics (diffraction and photon noise), geometry, temporal sampling and reference frames. Although Gaia is basically a self-calibrating instrument, things have to be stable enough over time scales that are long enough for the calibrations to be carried out, and the corresponding requirements are outlined. To achieve microarcsecond accuracy is technically extremely demanding, but feasible with a clever and careful design of the instrument.
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| 11. |
- Ludwig, Hans-Günter, et al.
(author)
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Status and future of hydrodynamical model atmospheres
- 2005
-
In: European Space Agency, (Special Publication) ESA SP. - 1609-042X .- 0379-6566. ; 560, s. 319-325
-
Conference paper (peer-reviewed)abstract
- Since about 25 years ago work has been dedicated to the development of hydrodynamical model atmospheres for cool stars (of A to T spectral type). Despite their obviously sounder physical foundation in comparison with standard hydrostatic models, their general application has been rather limited. In order to understand why this is, and how to progress, we review the present status of hydrodynamical modelling of cool star atmospheres. The development efforts were and are motivated by the theoretical interest of understanding the dynamical processes operating in stellar atmospheres. To show the observational impact, we discuss examples in the fields of spectroscopy and stellar structure where hydrodynamical modelling provided results on a level qualitatively beyond standard models. We stress present modelling challenges, and highlight presently possible and future observations that would be particularly valuable in the interplay between model validation and interpretation of observables, to eventually widen the usage of hydrodynamical model atmospheres within the astronomical community.
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| 12. |
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| 13. |
- Plicanic, Vanja, et al.
(author)
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Antenna diversity evaluation for mobile terminals
- 2006
-
In: European Space Agency, (Special Publication) ESA SP. - 0379-6566 .- 1609-042X. ; 626 SP
-
Conference paper (peer-reviewed)abstract
- In this paper we are focusing on the practical, engineering way of evaluating and characterizing the multi-channel antenna solutions on the mobile terminal. Two methods of calculating the parameters, describing the diversity performance, are described and the practical use of the methods in simulations and measurements are presented and evaluated. The time saving aspect of using the scattering parameters is lifted forward but also its limitations. For comparison, a statistical method for calculating Diversity Gain is also presented. This evaluation is performed for two multi-channel antenna solutions with different characteristics for the purpose of characterizing different diversity performances.
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| 14. |
- Sjöberg, Daniel
(author)
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An integral equation method dealing with surface waves on large finite periodic structures
- 2006
-
In: European Space Agency, (Special Publication) ESA SP. - 0379-6566 .- 1609-042X. ; 626 SP
-
Conference paper (peer-reviewed)abstract
- We present a method for studying large finite periodic structures using software developed for infinite periodic structures. The method is based on the Floquet-Bloch transformation, which splits the spatial description into one microscopic spatial variable inside the unit cell, and one macroscopic wave vector describing the variations on a scale encompassing many unit cells. The resulting algorithm is iterative, and solves an infinite periodic problem in each step, where the sources have been filtered through a windowing function. The computational cost for the iterations is negligible compared to computing the impedance matrices for the infinite periodic problems, and it is shown that the algorithm converges if the periodic structure is large enough.
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| 15. |
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| 16. |
- Svensson, Fredrik, et al.
(author)
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Hydrodynamical simulations of convection-related stellar micro-variability
- 2005
-
In: European Space Agency, (Special Publication) ESA SP. - 1609-042X .- 0379-6566. ; 560, s. 979-984
-
Conference paper (peer-reviewed)abstract
- We used a series of CO5BOLD hydrodynamical model atmospheres covering stellar objects from white dwarfs to red giants to derive theoretical estimates of the photometric and photocentric stellar variability in wavelength-integrated light across the Hertzsprung-Russell diagram. We validated our models against solar measurements from the SoHO/VIRGO instrument. Within our set of models we find a systematic increase of the photometric as well as photocentric variability - which turn out to be closely connected - with decreasing surface gravity. The estimated absolute levels of the photocentric variability do not affect astrometric observations on a precision level expected to be achieved by the GAIA mission - with the exception of close-by giants. The case of supergiants remains to be investigated. In view of the ongoing debate about the photometric non-detection of p-modes in Procyon by the Canadian MOST satellite we remark that we obtain a factor of approximately equals 3 in amplitude between the granular background "noise" in the Sun and Procyon. This statement refers to a particular representation of temporal power spectra as discussed in Sect. 5.
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| 17. |
- Söderhjelm, Staffan
(author)
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Census of binaries - The big picture
- 2005
-
In: European Space Agency, (Special Publication) ESA SP. - 1609-042X .- 0379-6566. ; 576, s. 97-104
-
Conference paper (peer-reviewed)abstract
- Gaia will observe huge numbers of binaries with a large range of periods. The present contribution tries to present some estimates of the expected number of detections and/or orbit determinations, based on simplified but large-scale simulations. The simulations have to model both a Galaxy with binaries, the instrument and observations, and the reduction programs. As in previous studies, there are marked distance-effects, with the solar neighbourhood (within a few hundred pc) much more completely sampled than more typical (few kpc) Gaia distances. The large number of simulated solutions allows also a study of some systematic effects in the astrometry of undetected binaries.
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| 18. |
- Ulander, Lars, 1962, et al.
(author)
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Borealscat: A tower experiment for understanding temporal changes in P- and L-band backscattering from a Boreal forest
- 2016
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In: European Space Agency, (Special Publication) ESA SP. - 0379-6566. - 9789292213053 ; 740
-
Conference paper (peer-reviewed)abstract
- This paper describes the tower-based radar BorealScat, which is being developed for polarimetric, tomographic and Doppler measurements at the hemi-boreal forest test site in Remningstorp, Sweden. The facility consists of a 50-m high tower equipped with an antenna array at the top of the tower, a 20-port vector network analyser (VNA), 20 low-loss cables for interconnection, and a calibration loop with a switching network. The first version of BorealScat will perform the full set of measurements in the frequency range 0.4-1.4 GHz, i.e. P-band and L-band. The tower is currently under construction at a forest stand dominated by Norway spruce (Picea abies (L.) Karst.). The mature stand has an above-ground dry biomass of 300 tons/ha. Data collections are planned to commence in autumn 2016.
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| 19. |
- Wahlgren, Glenn, et al.
(author)
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Identifying M supergiants with Gaia
- 2005
-
In: European Space Agency, (Special Publication) ESA SP. - 1609-042X .- 0379-6566. ; 576, s. 619-622
-
Conference paper (peer-reviewed)abstract
- As a group of stars having high luminosity and thus being able to be detected to great distances, massive M supergiants are extremely helpful to the study of the kinematics of the Milky Way. They are also partly responsible for the creation of post iron-group elements through the weak s-process of nucleosynthesis. As there are relatively few classified M supergiants, owing to their rapid pace of evolution, the identification of additional such stars will serve to significantly increase the sample that can be studied, which offers the promise of a higher fidelity in charting the regions of recent star formation in our Galaxy as well as a fuller description of trends that may be detected amongst their chemical compositions. We discuss the identification of M supergiants using the instrumentation onboard the Gaia satellite, emphasizing the nature of the photometric system that will best serve to classify M stars.
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| 20. |
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| 21. |
- Volski, V., et al.
(author)
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Overview of the software integration activities within ACE
- 2006
-
In: First European Conference on Antennas and Propagation (EuCAP), 2006, Nice, France, 6 - 10 November 2006. - : IEEE. - 0379-6566. - 9789290929376 ; 626 SP
-
Conference paper (peer-reviewed)abstract
- The ACE project initiated the start of several integration activities between European institutions involved in electromagnetic modeling of antennas with planar or conformal topologies. The goal of the integration activities was / is not to create a global software package that integrates the software of all partners, but to initiate a long term process for antenna software integration activities within the European antenna community. During the first two years of ACE the integration activities were performed in several groups with a rather small number of partners in each group. The groups were formed by partners who wanted to integrate a specific approach developed by one partner into the software code of another partner. This allows increasing the capability and efficiency of a software code. In this paper a short overview of all integration activities is given.
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| 22. |
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| 23. |
- Berg, Anders, 1983, et al.
(author)
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Demonstration of X-Band SAR Interferometry over Baltic Fast Ice
- 2013
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In: Proceedings of Earth Observation and Cryosphere Science, 13 - 16 November 2012, Frascati, Italy. - 1609-042X. - 9789290922766 ; 2013
-
Conference paper (other academic/artistic)abstract
- This study utilizes X-band SAR images acquired by theCosmo-SkyMed satellite constellation to map fast icedeformation at high spatial resolution. Twointerferometric acquisitions were performed in themiddle of the ice season in 2012 and with a temporalbaseline of 24 hours. The first interferogram revealsdeformation of the fast ice which is being forced by theramming drift ice. The drift ice moved towards the fastice with up to 600 m based on phase correlationmeasurements. The second interferogram shows a ratherlow fringe rate over the fast ice with fringes beingaligned along the coastline. Emerging cracks are easilyidentified with the associated phase discontinuities. It isalso observed that the backscatter and coherence levelsare connected in certain regions.
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| 24. |
- Berg, Anders, 1983, et al.
(author)
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Evaluation of a sea ice algorithm for SAR data from the Bay of Bothnia
- 2010
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In: Proceedings of the Third International Workshop SeaSAR 2010, 25-29 January 2010, Frascati, Italy. - 1609-042X. - 9789292212438 ; ESA SP-679
-
Conference paper (other academic/artistic)abstract
- A sea ice drift algorithm published by M. Thomas et. al.(2008) has been implemented and evaluated. Input tothe algorithm is Synthetic Aperture Radar (SAR)images, which are processed using phase correlation ina multi-resolution processing system. The algorithm hasbeen tested with horizontally co-polarized (HH)ENVISAT ASAR Wide Swath images andRADARSAT-2 ScanSAR images. The possible benefitsof using cross-polarized (HV) RADARSAT-2 ScanSARdata are investigated, and initial testing of the algorithmfor L-band SAR data from ALOS PALSAR has beendone.The validity of the produced motion fields has beentested in three different ways. Most of the SAR imagesin this analysis were acquired over the Bay of Bothnia.Five meteorological stations located in this region havebeen collecting wind data with a temporal resolution ofthree hours. It is confirmed that the wind data correlateswith the derived sea ice motion. Another source ofvalidation data that has been used is the daily ice chartspublished by the Swedish Meteorological andHydrological Institute (SMHI). The third method usedfor validation is straightforward, visual tracking of seaice features.The algorithm is facing some difficulties when it comesto ice tracking close to the shoreline, in archipelagoesetc, since the motionless solution will be favoured. Itcan however be suppressed by filtering areas of land.This addition gives a more robust algorithm.
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| 25. |
- Blomberg, Erik, 1987, et al.
(author)
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Simulated biomass retrieval from the spaceborne tomographic Saocom-CS mission at L-band
- 2016
-
In: European Space Agency, (Special Publication) ESA SP. - 0379-6566. - 9789292213053 ; 740
-
Conference paper (peer-reviewed)abstract
- This paper presents an evaluation of above-ground biomass (ABG) retrieval in boreal forests using simulated tomographic synthetic-aperture radar (SAR) data corresponding to the future SAOCOM-CS (L-band 1.275 GHz) mission. Using forest and radar data from the BioSAR 2008 campaign at the Krycklan test site in northern Sweden the expected performance of SAOCOM-CS is evaluated and compared with the E-SAR airborne Lband SAR (1.300 GHz). It is found that SAOCOM-CS data produce retrievals on par with those obtained with E-SAR, with retrievals having a relative RMSE of 30% or less. This holds true even if the acquisitions are limited to a single polarization, with HH results shown as an example.
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| 26. |
- Carlsson, Jan, 1962
(author)
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Results and experiences from two years of benchmarking of measurements facilities for small antennas and terminals within ACE
- 2006
-
In: European Conference on Antennas and Propagation: EuCAP 2006; Nice; France; 6 November 2006 through 10 November 2006. - : IEEE. - 0379-6566. - 9789290929376 ; 626 SP
-
Conference paper (peer-reviewed)abstract
- This paper presents the test cases defined in ACE (European Antenna Centre of Excellence) for benchmarking of facilities for measuring small mobile terminals and antennas, as well as results and experiences of the round robin test. The emphasis is put on measurements in the most popular communication frequency bands. Several test cases for passive antennas as well as for active devices were defined and collected in a test kit that was sent to different test facilities around Europe in a round robin test. The measured parameters include radiation efficiency, total radiated power, diversity gain and receiver sensitivity. The test cases include different locations of the test devices relative to a lossy cylinder that has dielectric characteristics resembling that of a human head.
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| 27. |
- Cordoba-Jabonero, Carmen, et al.
(author)
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Assessments for possible habitability in Martian polar environments : Fundaments based in ice screening of UV radiation
- 2004
-
In: ESA SP. - 0379-6566 .- 1609-0438. ; 545, s. 187-188
-
Journal article (peer-reviewed)abstract
- We present a study of the solar UV radiation in Martian high latitude environments covered by ice, where the UV propagation through the polar cover depends on the ice radiative properties (layers of H2O or CO 2 ice). But also we will investigate the changes in the subsurface UV levels induced by the seasonal variations of solar UV flux on the surface, as well as by the seasonal freezing-thawing and related CO2 sublimation processes. The biological dose relative to DNA-damage will be also estimated for biological implication assessments. All these studies will be compared with the biological dose received in the Antarctic snow-ice covered environment which is seasonally exposed to high UV radiation levels (formation of "ozone hole"), where the environmental conditions could be similar to those present on Mars
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| 28. |
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| 29. |
- Diallo, A., et al.
(author)
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Reverberation chamber evaluation of multi-antenna handset having low mutual coupling and high efficiencies
- 2006
-
In: European Conference on Antennas and Propagation: EuCAP 2006; Nice; France; 6 November 2006 through 10 November 2006. - 0379-6566. - 9789290929376 ; 626 SP
-
Conference paper (peer-reviewed)abstract
- This paper presents the evaluation of the diversity performances of several multi-antenna structures in a reverberation chamber. Firstly, a two-antenna system having low isolation between the radiators is measured. Its performances are compared with a second structure which uses a neutralization technique to enhance the radiating element's isolation. Then the performances of a four-antenna system with and without the neutralization method are measured and presented. Particularly, the total antenna efficiencies, the envelope correlation coefficients and the diversity gain of these systems are presented and discussed. We especially focus on the advantages of the neutralization technique.
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| 30. |
- Eklundh, Lars, et al.
(author)
-
High resolution mapping of vegetation dynamics from Sentinel-2
- 2012
-
In: Proceedings of 1st Sentinel-2 Preparatory Symposium. - 0379-6566. - 9789290922711 ; 707 SP
-
Conference paper (peer-reviewed)abstract
- The aim of this work is to develop and test a method for generation of information on vegetation dynamics from high-spatial resolution data, such as Sentinel-2. In order to accomplish this, Sentinel-2 data were simulated from existing SPOT HRG and HRVIR scenes over Sweden. We used TIMESAT, a well-tested computer package for generating smooth seasonal profiles and generation of seasonality parameters, like start and end, length, amplitude, integrated values, seasonal maximum, derivatives, etc. The processing works on a pixel-by-pixel basis and is resistant to clouds and noise. Data gaps are handled, and quality information can be included to increase the fidelity of the fits. The pilot study demonstrated that TIMESAT was successful in fitting smooth model functions to the data, and generating seasonality parameters for the test area at 10 × 10 m resolution. We conclude that TIMESAT will be useful for generating vegetation dynamics data from high-spatial resolution data such as Sentinel-2. The smooth seasonal profiles will be extremely useful for driving high-resolution biophysical vegetation models, and the seasonality parameters will be excellent for change detection, and for studying trends in vegetation productivity and seasonality.
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| 31. |
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| 32. |
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| 33. |
- Escoubet, C. P., et al.
(author)
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Imaging the magnetosphere using ISEE-1 spacecraft potential
- 1996
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In: European Space Agency, (Special Publication) ESA SP. - 0379-6566. ; :392, s. 179-187
-
Journal article (peer-reviewed)abstract
- The potential of ISEE 1 spacecraft has been used to derived the plasma density in the magnetosphere and its environment. First we show that using the equilibrium of currents flowing in and out of a spacecraft, we could derive numerically a relation between the spacecraft potential and the density of the surrounding plasma. After verifying that this relation was in good agreement with the measurement of the density made by other instruments during selected periods of time, we apply this relation to the spacecraft potential measured continuously from 1977 to 1984 on ISEE-1. An image of the plasma density in the magnetosphere and its environment is obtained as a result. All principal magnetospheric regions are clearly identified, from the solar wind with a density around 5 cm-3 , the magnetosheath around 50 cm-3, the magnetosphere around 1 cm-3, the plasma sheet around 0.5 cm-3 and finally the more tenuous tail lobes below 0.1 cm-3. The plasma density was observed slightly higher on the dawnside than on the dusk side of the magnetosphere. In addition the magnetosheath was closer to the Earth on the dawnside than on the duskside. When the magnetic activity increased (recorded by the AE index), the dayside magnetosphere was compressed/eroded by about 1 to 2 RE while the plasmasphere/inner magnetosphere became quite irregular and expanded in the dawn-midnight and in the dusk-noon sectors. In addition, during high magnetic activity, the plasmasheet at Ygsm = 0 was thicker and denser than at low activity. On the other hand the flanks of the plasmasheet were thinner and less dense during high activity than during low activity.
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| 34. |
- Fecht, H. -J, et al.
(author)
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Thermophysical properties of liquids : Modelling and non-metallic materials
- 2005
-
In: ESA SP. - 0379-6566 .- 1609-0438. ; :1281, s. 24-35
-
Journal article (peer-reviewed)abstract
- The accurate knowledge and high-precision measurements of the thermophysical properties of liquids is necessary for the numerical modeling of industrial processes where the solid-liquid phase transformation plays a crucial role. The reduction of magnetic levitation forces in microgravity leads either to a significant improvement in accuracy or makes the measurement possible in the first place. High-precision measurements on chemically highly reactive melts require containerless processing using non-contact diagnostic tools. Scientific precursor experiments were conducted in the TEMPUS containerless processing facility during the Spacelab IML-2 and MSL-1 missions, also.
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| 35. |
- Feldstein, Yakov I., et al.
(author)
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To directly driven and loading-unloading processes during substorm
- 1996
-
In: European Space Agency, (Special Publication) ESA SP. - 0379-6566. ; :389, s. 69-74
-
Journal article (peer-reviewed)abstract
- Model calculations of the electric fields in the high-latitude ionosphere are compared to measurements made by the Viking satellite during August 3, 1986 pass. The model calculations are based on the IZMEM procedure, where the electric field and currents in the ionosphere are given as functions of the interplanetary magnetic field (IMF). The event chosen correspond to the growth phase of substorm. The correlation between the model results and the satellite data is high, which assumes directly driven of the magnetosphere by the solar wind. Similar high correlation exists between the electric field in the solar wind (V*Bs) and AL magnetic activity indices, if time delays between the V*Bs observations in space and magnetic activity above the Earth's ground are taken into account. It is concluded, that the directly driven response of the magnetosphere to highly variable solar wind electric field is the main feature of geomagnetic activity at high latitudes.
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| 36. |
- Feldt, Robert, et al.
(author)
-
Analyzing the cost of complying to the ECSS standards for software development
- 2010
-
In: European Space Agency, (Special Publication) ESA SP. Conference on DAta Systems in Aerospace, DASIA 2010; Budapest; 1-4 June 2010. - Budapest : European Space Agency. - 0379-6566. - 9789290922469 ; 682, s. 303-307
-
Conference paper (peer-reviewed)abstract
- Software for space applications has special requirements in terms of reliability and dependability. Standards are one of the primary mechanisms to ensure a sufficient quality level, with the European Cooperation on Space Standardization (ECSS) standards being the main ones. The use of standards is not only a benefit since they can incur considerable costs in terms of, for example, additional documentation and activities. For making the right decisions on which development and quality assurance activities to focus on it is important to know not only their added value but also their costs. Here we present a method for analyzing the cost of standard compliance (CoSC) in software development. It is based on a model which divides the costs into four different types based on their primary value: development, quality-adding, confidence-adding and adherence. The adherence costs are those costs that are incurred by or follows from the use of a standard but does not add any immediate value to either the functionality, quality or quality assurance of the software. Initial results from applying the method in an industrial company adhering to ECSS is presented.
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| 37. |
- Feldt, Robert, et al.
(author)
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Optimizing Verification and Validation Activities for Software in the Space Industry
- 2010
-
In: European Space Agency, (Special Publication) ESA SP. Conference on DAta Systems in Aerospace, DASIA 2010; Budapest; 1-4 June 2010. - Budapest : European Space Agency. - 0379-6566. - 9789290922469 ; , s. 309-313
-
Conference paper (peer-reviewed)abstract
- Software for space applications has special requirements in terms of reliability and dependability and the verification & validation activities (VAs) of these systems often account for more than 50% of the develop- ment effort. The industry is also faced with political and market pressure to deliver software faster and cheaper. Thus new ways are needed to optimize these activities so that high quality can be retained even with reduced costs and effort. Here we present a framework for the management and optimization of verification & validation activities (VAMOS). An initial evaluation of the framework based on historical data as well as data extracted with a new tool has been done and are described briefly.
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| 38. |
- Fransson, Johan E.S.
(author)
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Examples of thematic mapping with ERS-Envisat tandem cross-interferometry
- 2010
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In: ESA SP (CD-ROM). - 1609-042X.
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Conference paper (other academic/artistic)abstract
- This paper deals with some aspects of thematic mapping using ERS-Envisat Tandem (EET) cross-interferometry (CInSAR). The long baseline of EET CInSAR and the short temporal baseline are in theory suitable for establishing a certain sensitivity of coherence and InSAR phase upon vegetation parameters. Here we show signatures of coherence and InSAR phase for maize fields in Switzerland, and clear-cuts and forest stem volume in Sweden. Both coherence and InSAR phase show sensitivity to vegetation height. By means of the Interferometric Water Cloud Model (IWCM) it is possible to describe the measurements by assuming a weak attenuation and low temporal decorrelation. Clearcuts show higher coherence than mature forests, although strong spatial decorrelation occurs in case of sloped terrain, not correctly accounted for when applying the common-band filter in interferometric processing. Coherence presents a certain sensitivity to stem volume, but only for flat terrain. The IWCM could describe the trend in the measurements reasonably well.
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| 39. |
- Islam, Md. Tariqul, 1980
(author)
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RIVER CHANNEL MIGRATION: A REMOTE SENSING AND GIS ANALYSIS
- 2010
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In: Proceedings of ESA Living Planet Symposium. 28 June - 2 July 2010, Bergen, Norway / edited by H. Lacoste-Francis. - 1609-042X. - 9789292212506 ; :SP-686
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Conference paper (peer-reviewed)abstract
- Remote sensing and geographic information system provide tools for quantitative and qualitative river morphological analysis. Bangladesh is a riverine, flood prone country and, the Padma and the Jamuna are two of major three rivers in the country. The aim of this research is to monitor the channel migration of the Padma and the Jamuna rivers since 1977 to 2004 using remote sensing and GIS. Four scenes for dry season’s cloud free Landsat images were used in this study. Images were processed using PCI Geomatica and ArcGIS 9.3 was used for GIS analysis. The Landsat images were visualized and identified nine locations to investigate the channel migration. The images were classified into two broad categories, i.e. water and nonwater body. ArcGIS 9.3 was used to transfer these classified images into GIS layers. A standard measurement tool of ArcGIS was applied to measure the movement of river channel based on initial river channel in 1977. General trend of the Padma and the Jamuna river channel migration at locations A, B, C, D, F, G, H and I towards north, northeast and southwest eventually, north, northeast, east, east, west and west, respectively. The confluence point of the Padma and Jamuna (at location E) migrated toward southeast with high rate. During 1977-2004, it migrated about 9000m toward southeast. Trend of migration of the confluence point was faster than any other locations in the channel of the Padma river.
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| 40. |
- Karlsson, Kristian, 1973, et al.
(author)
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Analysis of Wires Inside a Reverberation Chamber Using the Method of Moments Combined with Spectral Domain Techniques and Asymptotic Extraction
- 2006
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In: European Conference on Antennas and Propagation: EuCAP 2006; Nice; France; 6 November 2006 through 10 November 2006. - : IEEE. - 0379-6566. - 9290929375 ; 626 SP
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Conference paper (peer-reviewed)abstract
- In this paper we will present a Method of Moments (MoM) code that can be used for analyzing PEC objects in a Reverberation Chamber (RC). The RC is treated as a rectangular cavity, and the Green's function of it is constructed by using planar wave spectral domain techniques and imaging combined with periodic boundary conditions. Several validation cases based on comparisons with other computer codes are also presented.
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| 41. |
- Khosravi, Maryam, 1975, et al.
(author)
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Climatologies of stratospheric short-lived species from Odin/SMR: Methodology for ClO
- 2013
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In: Proceedings ESA Living Planet Symposium, 9-13 September 2013, Edinburgh (UK). ESA-SP-722 : European Space Agency, Noordwijk, The Netherlands. - 1609-042X. - 9789292212865 ; , s. 1-6
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Conference paper (other academic/artistic)abstract
- The Sub-Millimetre Radiometer (SMR) on board theOdin satellite has been measuring short-lived strato-spheric species such as chlorine monoxide (ClO) sinceOdin’s launch in 2001. Odin/SMR at its sun-synchronousorbit measures at certain local times observations aroundsunrise and sunset at the equator. Due to the drift ofOdin’s orbit in local solar time and the fact that mea-surements are done at different local times, a correctionis required before a monthly zonal mean climatologycan be calculated and trends of ClO can be evaluated.To deal with this, scaling factors are calculated using aphoto-chemical box model for correction of the mixingratios respective to a reference time. The uncertaintiesand limitations of this method are estimated by checkingthe internal consistency of the results, so that comparingthe scaled a.m. ClO time-series to p.m. scaled time-series should give the same results. We found out thatscaling SMR ClO to the ascending time of MicrowaveLimb Sounder (MLS) as reference at about 1.30 a.m. atthe equator gives better result compared to the scalingClO to MLS descending node at about 1.30. p.m. Thetime series calculated for the morning SMR ClO scaled(to 1.30 a.m.) agrees with the evening ClO scaled.
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| 42. |
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| 43. |
- Lindblad, Bertil Anders, et al.
(author)
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Solar control of meteor radar rates
- 2003
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In: Solar variability as an input to the Earth's environment. International Solar Cycle Studies (ISCS) Symposium, 23 - 28 June 2003, Tatranská Lomnica, Slovak Republic.. - 929092845X ; ESA SP-535, s. 755-759
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Conference paper (peer-reviewed)abstract
- Meteor radar observations carried out in August-September 1953-84 at theOnsala Space Observatory in Sweden show long-term, as well as short termvariations in meteor radar rates. These rate variations are associatedwith position in the solar cycle, and with variations in the solar windsector structure. An inverse correlation is found between meteor radarrates and the solar cycle. The magnitude of this effect is quite large;about twice as many radar echoes are observed at solar minimum as atsolar maximum. We propose that this long-term inverse correlation withthe sunspot number is caused by a solar cycle controlled variation ofthe atmospheric density gradient at meteor ablation heights (90-110 km).Day-to-day variations in meteor radar rates, which correlate withshort-term geomagnetic activity have also been detected. A superposedepoch analysis based on solar wind sector boundaries as key dates showsthat a minimum in meteor radar rates occurs about 3 days after theEarth's passage of a solar wind sector boundary.
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| 44. |
- Marklund, Göran, et al.
(author)
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Astrid 2, A low-budget microsatellite mission for auroral research
- 1997
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In: European Space Agency, (Special Publication) ESA SP. - 0379-6566. ; :397, s. 387-394
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Journal article (peer-reviewed)abstract
- The next in the Astrid series of low-budget microsatellite missions will be devoted to classical auroral research. The challenge of this mission is to demonstrate the possibility to carry out comprehensive auroral investigations on a microsatellite platform having the size 0.45 × 0.45 × 0.3 m at a cost of about 2 MUSD. A successful mission will open up new less expensive ways carrying out auroral research in the future, ways which are complementary to the more ambitious programmes run within ESA and NASA. Of particular interest are multipoint measurements within the auroral acceleration region using clusters of microsatellites. New light-weight and compact instruments and deployment systems have been developed for the Astrid-2 mission. The payload will carry an integrated electric and magnetic field instrument, including a Langmuir probe, a lightweight ion and electron spectrometer, and two spin-scanning UV photometers for Lyman α and oxygen emissions in the aurora. The electric field probes will be deployed using a newly developed light-weight system for wire boom deployment. Other novel features to be used on Astrid-2 are data compression and data filtering. Astrid-2 is to be launched on a Kosmos vehicle from Plesetsk in 1997 into an 83° inclination circular orbit at 1000 km altitude. The mission will use a geographically distributed ground station network for high-speed S-band data reception, one station to be located at Solna, Sweden and another at the South African Antarctic base SANAE.
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| 45. |
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| 46. |
- Pathan, Risat, 1979, et al.
(author)
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Temporal Partitioning on Multicore Platform
- 2014
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In: European Space Agency, (Special Publication) ESA SP. - 0379-6566. - 9789292212896 ; SP 725
-
Conference paper (peer-reviewed)abstract
- This paper addresses the problem of ensuring temporal partitioning according to the ARINC-653 standard for integrating multiple applications on the same multicore platform. To employ temporal partitioning, we propose the design and analysis of a hierarchical scheduling framework (HSF) for multicore platform. In HSF, each application has a server task, which is mapped to one of the physical cores of the multicore platform. The HSF framework is based on scheduling at two-levels: (i) a system-level scheduler for each core schedules the server tasks that are mapped to that core, and (ii) a task-level scheduler for each application schedules the tasks of the application. This paper presents the design and analysis of this two-level HSF that can be used to ensure temporal partitioning and meeting all the deadlines of each application tasks. The effectiveness of our technique is demonstrated using real-world space applications provided by RUAG Space Sweden AB.
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| 47. |
- Perot, Kristell, 1985, et al.
(author)
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Odin/SMR Observations of a Particularly Strong Midwinter Stratospheric Sudden Warming in Early 2013
- 2013
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In: Proceedings of ESA Living Planet Symposium. - 1609-042X. - 9789292212865 ; SP-722
-
Conference paper (other academic/artistic)abstract
- The Sub-Millimetre Radiometer (SMR), on boardthe Odin satellite, observed a major stratospheric suddenwarming (SSW) in the northern hemisphere in earlyJanuary 2013. The provided measurements have beenused to identify and characterize this event which seemsto be the strongest of that kind in recent years. Thispaper is based on a comparison with the 2009 SSWwhich was so far considered as a record-breaking event.SSWs are an important manifestation of the couplingphenomena between the mesosphere / lowerthermosphere and the lower atmospheric layers and canstrongly affect the middle atmospheric composition. It iscrucial to study these events in order to get a betterunderstanding of the dynamical and chemicalmechanisms that control this part of the atmosphere.
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| 48. |
- Persson, Henrik, et al.
(author)
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Estimation of forest variables using radargrammetry on TerraSAR-X data in combination with a high resolution DEM
- 2013
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In: Esa Sp. - 0379-6566. ; 2013
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Conference paper (other academic/artistic)abstract
- This study uses the backscattered intensity information from SAR images acquired with TerraSAR-X to derive Digital Surface Models with radargrammetry. Then the known ground elevation (from airborne lidar) is subtracted to get Canopy Height Models that are analysed and linked through regression analysis to the forest variables above-ground biomass and tree height. It was found, that the used constellation of image pairs and prediction models produced biomass estimations at stand level with 25.9% and 33.8% relative RMSE, while the height estimations were 11.5% and 12.3%. The analyses were tested at the Swedish test sites Krycklan and Remningstorp.
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| 49. |
- Popielawska, B., et al.
(author)
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An imprint of the quiet plasma sheet structure at the orbit of viking : Magnetosphere without substorms
- 1996
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In: European Space Agency, (Special Publication) ESA SP. - 0379-6566. ; :389, s. 133-139
-
Journal article (peer-reviewed)abstract
- We present a study of the plasma sheet structure as seen on VIKING during prolonged periods of magnetic quiescence. The ion and electron spectrograms, the electric field data and field-aligned current signatures in the magnetic field data are examined. A special attention is paid to cases when the Low Latitude Boundary Layer-like plasma is seen deep in the nightside at latitudes which apparently map to close geocentric distances as it implies an exotic plasma circulation in the tail. An attempt has been made to infer from VIKING data how the quiet plasma sheet is formed, whether it originates mainly from the mantle source via the interaction with the distant tail current sheet or whether the lateral transport of the Low Latitude Boundary Layer (LLBL) from the tail flanks (with essentially adiabatic particle motion) takes place followed by the sunward convection in the central part of the near-Earth tail. The VIKING plasma and electric field data suggest that the last mechanism is decisive for plasma sheet structuring during prolonged periods of northward IMF.
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| 50. |
- Rothwell, P.L., et al.
(author)
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Inertial currents and substorm onsets
- 1996
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In: European Space Agency, (Special Publication) ESA SP-389. - 0379-6566. ; , s. 447-452
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Journal article (peer-reviewed)abstract
- When magnetic field lines are sufficiently stretched during the substorm growth phase, in the equatorial plane the earthward ExB ion drift velocity can become comparable to the ion gyration velocity. Under these conditions inertial currents can become quite important. Using a two-dimensional model we find that O+ ions injected from the ionosphere into the equatorial plane at high latitudes will drift eastward at radial distances less than -10 RE because the inertial drift dominates and westward at distances closer to the earth because the magnetic gradient drift dominates. The inertial eastward drift gives rise to a current which in terms of JxB is consistent with the convective deceleration of the earthward drift velocity due to higher values of B. Similarly, momentum balance requires that the convective acceleration of the westward drift velocity should be consistent with a tailward inertial current. Therefore, an equatorial current wedge system with eastward and tailward current components naturally arises from the ion dynamics. In a future paper a three-dimensional treatment will determine whether curvature drift masks the eastward inertial drift of the oxygen ions.
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