Norwegian Space Center
Norwegian Space Center
Juzeniene A.,Norwegian Radium Hospital |
Brekke P.,Norwegian Space Center |
Dahlback A.,University of Oslo |
Andersson-Engels S.,Lund University |
And 6 more authors.
Reports on Progress in Physics | Year: 2011
The Sun has played a major role in the development of life on Earth. In Western culture, people are warned against Sun exposure because of its adverse effects: erythema, photoimmunosuppression, photoageing, photocarcinogenesis, cataracts and photokeratitis. However, Sun exposure is also beneficial, since moderate doses give beneficial physiological effects: vitamin D synthesis, reduction of blood pressure and mental health. Shortage of Sun exposure may be even more dangerous to human health than excessive exposure. Avoiding Sun exposure leads to vitamin D deficiency which is associated not only with rickets and osteomalacia, but also with increased risk of cardiovascular disease, multiple sclerosis, rheumatoid arthritis, diabetes, influenza, many types of cancer and adverse pregnancy outcomes. Solar radiation induces nitric oxide release in tissue and immediate pigment darkening which certainly play important roles, although these are still unknown. Action spectra relevant for health are described. We will also review what is known about spectral and intensity variations of terrestrial solar radiation as well as its penetration through the atmosphere and into human skin and tissue. © 2011 IOP Publishing Ltd.
De Pontieu B.,Lockheed Martin |
De Pontieu B.,University of Oslo |
Title A.M.,Lockheed Martin |
Lemen J.R.,Lockheed Martin |
And 89 more authors.
Solar Physics | Year: 2014
The Interface Region Imaging Spectrograph (IRIS) small explorer spacecraft provides simultaneous spectra and images of the photosphere, chromosphere, transition region, and corona with 0.33 - 0.4 arcsec spatial resolution, two-second temporal resolution, and 1 km s-1 velocity resolution over a field-of-view of up to 175 arcsec × 175 arcsec. IRIS was launched into a Sun-synchronous orbit on 27 June 2013 using a Pegasus-XL rocket and consists of a 19-cm UV telescope that feeds a slit-based dual-bandpass imaging spectrograph. IRIS obtains spectra in passbands from 1332 - 1358 Å, 1389 - 1407 Å, and 2783 - 2834 Å, including bright spectral lines formed in the chromosphere (Mg ii h 2803 Å and Mg ii k 2796 Å) and transition region (C ii 1334/1335 Å and Si iv 1394/1403 Å). Slit-jaw images in four different passbands (C ii 1330, Si iv 1400, Mg ii k 2796, and Mg ii wing 2830 Å) can be taken simultaneously with spectral rasters that sample regions up to 130 arcsec × 175 arcsec at a variety of spatial samplings (from 0.33 arcsec and up). IRIS is sensitive to emission from plasma at temperatures between 5000 K and 10 MK and will advance our understanding of the flow of mass and energy through an interface region, formed by the chromosphere and transition region, between the photosphere and corona. This highly structured and dynamic region not only acts as the conduit of all mass and energy feeding into the corona and solar wind, it also requires an order of magnitude more energy to heat than the corona and solar wind combined. The IRIS investigation includes a strong numerical modeling component based on advanced radiative-MHD codes to facilitate interpretation of observations of this complex region. Approximately eight Gbytes of data (after compression) are acquired by IRIS each day and made available for unrestricted use within a few days of the observation. © 2014 The Author(s).
Appourchaux T.,Institute dAstrophysique Spatiale |
Belkacem K.,University of Liège |
Broomhall A.-M.,University of Birmingham |
Chaplin W.J.,University of Birmingham |
And 18 more authors.
Astronomy and Astrophysics Review | Year: 2010
Solar gravity modes (or g modes)-oscillations of the solar interior on which buoyancy acts as the restoring force-have the potential to provide unprecedented inference on the structure and dynamics of the solar core, inference that is not possible with the well-observed acoustic modes (or p modes). The relative high amplitude of the g-mode eigenfunctions in the core and the evanesence of the modes in the convection zone make the modes particularly sensitive to the physical and dynamical conditions in the core. Owing to the existence of the convection zone, the g modes have very low amplitudes at photospheric levels, which makes the modes extremely hard to detect. In this article, we review the current state of play regarding attempts to detect g modes. We review the theory of g modes, including theoretical estimation of the g-mode frequencies, amplitudes and damping rates. Then we go on to discuss the techniques that have been used to try to detect g modes. We review results in the literature, and finish by looking to the future, and the potential advances that can be made-from both data and data-analysis perspectives-to give unambiguous detections of individual g modes. The review ends by concluding that, at the time of writing, there is indeed a consensus amongst the authors that there is currently no undisputed detection of solar g modes. © 2010 Springer-Verlag.
Sejourne A.,University Paris - Sud |
Sejourne A.,Polish Academy of Sciences |
Costard F.,University Paris - Sud |
Fedorov A.,North-Eastern Federal University |
And 5 more authors.
Geomorphology | Year: 2015
As observed in most regions in the Arctic, the thawing of ice-rich permafrost (thermokarst) has been developing in Central Yakutia. However, the relationship between thermokarst development and climate variations is not well understood in this region, in particular the development rate of thaw slumps. The objective of this paper is to understand the current development of thermokarst by studying the evolution of the banks of thermokarst lakes. We studied retrogressive thaw slumps and highly degraded ice-wedge polygons (baydjarakhs), indicative of thermokarst, using high resolution satellite images taken in 2011-2013 and conducting field studies. The retrogressive thaw slump activity results in the formation of thermocirque with a minimum and maximum average headwall retreat of 0.5 and 3.16m·yr-1 respectively. The thermocirques and the baydjarakhs are statistically more concentrated on the south- to southwest-facing banks of thermokarst lakes. Moreover, the rate of headwall retreat of the thermocirques is the most important on the south-facing banks of the lakes. These observations indicate a control of the current permafrost thaw on the banks of thermokarst lakes by insolation. In the context of recent air temperature increase in Central Yakutia, the rate of thermocirque development may increase in the future. © 2015 Elsevier B.V.
Baltuck M.,CSIRO |
Briggs S.,European Space Agency |
Loyche-Wilkie M.,FAO |
McGee A.,Khan Research Laboratories |
And 2 more authors.
Carbon Management | Year: 2013
Multilateral organization incentives and emerging carbon credit markets could benefit national governments, which can demonstrate reduction of emissions from deforestation and forest degradation. Such demonstration requires a credible national forest monitoring system. The Global Forest Observations Initiative was developed to foster the sustained availability of satellite Earth observations for national forest monitoring systems and assist countries to make the best use of these observations in multinational framework reporting or for improved management of their natural resources. © 2013 Future Science Ltd.
Loge L.,Norwegian University of Science and Technology |
Gangaas O.,Norwegian Space Center
AIAA SPACE Conference and Exposition 2011 | Year: 2011
This paper offers a roadmap and explores options toward new technology and system so- lutions, which provides both opportunities and challenges for the future of mobile satellite communications. Today global geostationary coverage on Ku-band is becoming a reality. Ka-band utilization represents the next step towards enhanced capacity. At present sev- eral satellite operators have implemented Ka-band capacity, and more operators have an- nounced that new Ka-band satellites will be launched in the near future. This development will have a significant impact on satellite services and applications in the years to come. The paper first provides a historical perspective of some crucial technologies and key at- tributes in a satellite communications network. The physical boundaries of attributes such as noise figure, spectrum effciency, coding and modulation are explored. Also discussed are the key technical requirements and considerations needed to turn the next generation satcom services into a commercial success. Secondly the paper looks at trends and future requirements in new systems, services and applications. The main focus is on the possi- bilities and hurdles that come with mobile satcom services offered at higher frequencies. The potential for smaller terminals, reduced cost and relevant system parameters when moving up in frequency are examined. The paper concludes by highlighting tradeoffs and identifying promising opportunities, that potentially can enhance the service offering and applications in alignment with identified market trends and requirements. © 2011 by Lars Loge and Odd Gangaas.
Sigernes F.,University Center in Svalbard |
Dyrland M.,University Center in Svalbard |
Brekke P.,Norwegian Space Center |
Gjengedal E.K.,Storm Weather Center |
And 4 more authors.
Optica Pura y Aplicada | Year: 2011
A method to forecast, up to one hour in the future, the size and location of the aurora oval is described. The work is based on a mathematical description of the aurora oval coupled to predicted values of the planetary K p index. As a result, a real time animation of the oval mapped onto the Earth's surface is created. The night- and dayside are visualized together with the location of the twilight zone as Earth rotates under the aurora oval. © Sociedad Española de Óptica.
Loge L.,Norwegian Space Center
32nd AIAA International Communications Satellite Systems Conference, ICSSC 2014 | Year: 2014
Highly elliptical orbits (HEO) are believed to be able to provide broadband communications to the Arctic in a cost efficient manner. Recent studies have proposed three HEO alternatives for this purpose where the main difference is the orbital period, 12 h, 16 h and 24 h orbits. One important reason behind the search for new and innovative HEO alternatives different from the well known critically inclined 12 h Molniya is the radiation environment. This paper presents results from analysis of three important effects the radiation environment in space inicts on satellites for three HEO alternatives and a geo-stationary reference. Those effects are solar cell degradation, total ionizing dose and single event upsets. The ESA developed SPENVIS tool has been used in the analysis with two separate, but related, models for radiation caused by trapped protons and electrons. The variations in the results for the three HEO alternatives and the geostationary reference are less profound than expected. Only in terms of solar cell degradation was there found to be any significant negative results for the 12 h alternative, but adequate countermeasures should be available. The results indicate that the 12 h alternative is the least attractive, but the variations between the HEO alternatives are not excessive. As an overall assessment it is therefore concluded that operation of HEO-satellites with a lifetime of 15 years should be feasible in all the three HEO alternatives.