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Our space age technology enables global communication, navigation, and power distribution that has given rise to our 'smart', interconnected and spacefaring world. Much of the infrastructure modern society depends on, to live on Earth and to explore space, is susceptible to space weather storms originating from the Sun. The Second Edition of this introductory textbook is expanded to reflect our increased understanding from more than a dozen scientific missions over the past decade. Updates include discussions of the rapidly expanding commercial space sector, orbital debris and collision hazards, our understanding of solar-terrestrial connections to climate, and the renewed emphasis of human exploration of the Moon and Mars. It provides new learning features to help students understand the science and solve meaningful problems, including some based on real-world data. Each chapter includes learning objectives and supplements that provide descriptions of the science and learning strategies to help students and instructors alike.
From the earliest days of the nuclear age, the issue of verification has plagued efforts to restrain the development, testing, and deployment of nuclear weapons and to ensure their destruction. It continues to do so. Especially sensitive are on-site inspections, but they have proved their worth in disarmament treaties since the 1980s and the last years of the Cold War. This chapter looks at verification thematically, by reference to testing, non-proliferation, disarmament, and deployment of nuclear weapons.
This paper discusses the design steps and experimental characterization of a monolithic microwave integrated circuit (MMIC) power amplifier developed for the next generation of K-band 17.3–20.2 GHz very high throughput satellites. The technology used is a commercially available 100-nm gate length gallium nitride on silicon process. The chip was developed taking into account the demanding constraints of the spacecraft and, in particular, carefully considering the thermal constraints of such technology, in order to keep the junction temperature in all devices below 160°C in the worst-case condition (i.e., maximum environmental temperature of 85°C). The realized MMIC, based on a three-stage architecture, was first characterized on-wafer in pulsed regime and, subsequently, mounted in a test-jig and characterized under continuous wave operating conditions. In 17.3–20.2 GHz operating bandwidth, the built amplifier provides an output power >40 dBm with a power added efficiency close to 30% (peak >40%) and 22 dB of power gain.
During an era marked by suspicion, and recurrent failures of ‘humint’ (human intelligence gathering), Cold War decision-makers were increasingly captivated and guided by the prognostications and intimations of ‘sigint’ (signals intelligence), ‘comint’ (communications intelligence) and ‘elint’ (electronic intelligence): that is, intelligence gathering through the interception and interpretation of electronic or electromagnetic signals and communications. Decision- and policy-making under the rubric of international law engaged continually with the would-be, could-be or might-have-been moves of key protagonists, as those moves appeared in electronic data. International legal order came to be marked, during the Cold War, by the latent or virtual agency of these overlapping ‘data shadows’ in ways that leave an enduring legacy today. This is demonstrated here by brief discussion of two instances of international conflict, and associated legal analysis, in ‘the “hottest” theatre’ of the Cold War: Asia.
Recent technological advancements are facilitating the use of satellite remote-sensing techniques for the measurement of atmospheric concentrations of greenhouse gas emissions. This article evaluates the potential for these satellite-enabled measurements to contribute to transparency and answerability for state emissions, with a focus on international space law and policy, and the Paris Agreement to the United Nations Framework Convention on Climate Change. We show that in the context of the international space governance framework, the dissemination of integrated emissions data sets has the potential to enhance public answerability for the mitigation performance of states. Under the Paris Agreement, there is scope for space-based measurement techniques to provide an independent data source to support verification activities for national emissions inventories, and for aggregated data to be utilized as part of the global stocktake under Article 14. There are, however, a number of impediments to translating these transparency gains into enhanced answerability for states’ emissions reduction pledges.
This article raises awareness of how countries can leverage space and space technologies to achieve the Sustainable Development Goals (SDGs) through concrete examples. Space science, technology and applications can support a range of pro-developmental activities, such as agricultural planning, biodiversity protection, tele-health and disaster management. United Nations Office for Outer Space Affairs (UNOOSA) helps countries to use space technology in all of these areas, through capacity building and partnerships with government and private sector entities to expand access to space, especially for developing countries. This article also outlines the work of UNOOSA in promoting increased participation of women in the space sector and in STEM careers.
Europa is a prime target for astrobiology and has been prioritized as the next target for a National Aeronautics and Space Administration flagship mission. It is important, therefore, that we advance our understanding of Europa, its ocean and physical environment as much as possible. Here, we describe observations of Europa obtained during its orbital eclipse by Jupiter using the Hubble Space Telescope. We obtained Advanced Camera for Surveys Solar Blind Channel far ultraviolet low-resolution spectra that show oxygen line emission both in and out of eclipse. We also used the Wide-Field and Planetary Camera-2 and searched for broad-band optical emission from fluorescence of the surface material, arising from the very high level of incident energetic particle radiation on ices and potentially organic substances. The high-energy particle radiation at the surface of Europa is extremely intense and is responsible for the production of a tenuous oxygen atmosphere and associated FUV line emission. Approximately 50% of the oxygen emission lasts at least a few hours into the eclipse. We discuss the detection limits of the optical emission, which allow us to estimate the fraction of incident energy reradiated at optical wavelengths, through electron-excited emission, Cherenkov radiation in the ice and fluorescent processes.
Water is an abundant molecule in the Cosmos. It has exploitable and unique spectroscopic and physical properties and has been found to be ubiquitous in places that we would expect in the standard model of solar system formation and nebular condensation: beyond the snow line in outer solar system planets, moons, asteroids, and comets. However, water is also an important constituent of planetary bodies (dominating at least one of their surfaces) in the inner solar system, likely indicating significant mixing between inner and outer solar system reservoirs of water during planetary accretion and the early history of the solar system. Water has played a critical role in the differential evolution of the terrestrial planets Venus, Earth, and Mars, and the concept of the “habitable zone” where liquid water could be stable on an Earth-like planet provides a starting point for assessing the habitability of worlds in our solar system and beyond. Examples of potentially habitable environments outside this zone in our own solar system warn us that this concept should only be a guide, however-important exceptions will no doubt occur. Recent discoveries of past liquid water and abundant present subsurface ice on Mars, of water reservoirs in unexpected places like the poles of Mercury and the Moon and the subsurface of Enceladus, of water in circumstellar disks and in the atmospheres of extrasolar planets, and the expectation of the discovery of water on Earth-like worlds in the habitable zones around other stars make this an exciting time in the study of water on planets both in our own solar system, and beyond.
La qualification des satellites se fait entre
autres par des essais de type sinus balayé sur vibrateur, d'où
l'idée de profiter de ces essais pour identifier les modes propres, au
lieu de faire séparément une analyse modale classique, afin de
gagner en coûts et délais. Cela nécessite de considérer une
excitation du spécimen par sa base et non par force, et d'exploiter
très rapidement les données d'essai. Cet article propose une
solution générale basée sur le concept de paramètres modaux
effectifs. Le traitement, compatible avec une session interactive,
privilégie la simplicité d'utilisation et la robustesse,
éventuellement au détriment d'une certaine précision. La
méthodologie est présentée et illustrée par un exemple
industriel dans le contexte d'une étude pour l'Agence Spatiale
This paper presents the parametric analysis of ply properties on composite
cylinder design for satellites. The composite cylinder is modelled as a
sandwich construction type with honeycomb as a core and a multi-layer
laminate composed of CFRP (Carbon Fiber Reinforced Plastics) plies as a
skin. A design algorithm is developed with the help of C programs interfaced
with IDEAS EDS for finite element analysis. During simulation, the different
subsystems and panels are idealised as a mass load applied at their centre
of gravities. Different parameters such as aspect ratio, ply orientation and
number of plies have been analysed for arriving optimum design satisfying
the static and frequency constraints. This approach is well implemented in
the design and development of composite cylinder for different satellites
and their validation with tests are under development.
As is evident from Director Dan Green's detailed report below, the Central Bureau for Astronomical Telegrams (CBAT) continues to function in a very reliable and efficient way. The electronic telegrams (CBETs) introduced in 2002 have proved to be a great success; they allow for very rapid dissemination of more extensive information than there is room for on printed Circulars, and they are frequently cited in the astronomical literature. The workload on the Director seems to be forever increasing. It is therefore gratifying that an Assistant Director, Gareth Williams, has been appointed. Since he also serves as Associate Director of the Minor Planet Center (MPC) and performs many of the computations on which the CBETs and the Circulars are based, the ties and mutual benefits between the CBAT and the MPC have been made even stronger.
This report is a brief summary of some of the major achievements in studies of planets and satellites that have been accomplished during the years 2003–2005. Unlike previous years, we do not attempt to provide a detailed overview of the field but rather choose to highlight aspects which are of particular novelty.
Remote sensing provides the means to study features and processes that are not easily accessible or amenable to direct observations. The polar regions, and Antarctica in particular, offer a variety of examples where the ability to observe from afar is necessary or highly desirable. In particular, studies of ice shelf processes, changes in the sea-ice cover, and ice-ocean-atmosphere investigations must rely in large part on measurements from aircraft and satellites. The polar regions present a unique set of problems that complicate applications and limit the usefulness of certain sensors; new instruments planned for launch in the 1990s will help resolve many of these difficulties. Examples of remote sensing applications for the study of the continent, drifting ice, ocean, and atmosphere demonstrate ways that existing data as well as new observations can be used to aid polar research.
In Satellite-Based Augmentation Systems (SBAS), the correction messages are transmitted to the users' receivers via geostationary communication satellites (GEOS) at GPS L1 (1575·42 MHz) frequency. Severe scintillations in the equatorial zone disrupt geostationary satellite links even at L-band. Observations of scintillations at 1·5 GHz from Calcutta (22·58°N, 88·38°E geographic, 32°N magnetic dip), located near the crest of the equatorial anomaly in the Indian zone, show that scintillations occur in patches of duration varying from a few minutes to several hours. During the solar maximum years 1998–2000, severe scintillations (Scintillation Index [ges ]15 dB) were recorded for 48 hr 55 min (1·27%) out of the total observation time of 3868 hr 9 min in the local time interval 19 to 00 hrs. In order to have a fail-safe system, it is suggested that more than one geostationary satellite be used in SBAS so that, if one link is disrupted, the other can be used for transmission of correction messages to the GPS users. The minimum longitudinal separation between two GEOS required for reliable operation of SBAS has been estimated, from the cumulative distribution of scintillation patch duration, to be 57° in the Indian longitude zone.
Optical spectroscopy, including low and room temperature photoluminescence (PL), reflectance, PL measurements in high magnetic fields up to 12 T, and resonantly-enhanced electronic Raman scattering (RERS) in zero and high magnetic field, has been used to investigate exciton and impurity states and surface recombination in high quality heteroepitaxial GaN grown on sapphire and SiC. Theoretical finite-difference calculations of the donor states as a function of magnetic field have been carried out for comparison, including the effects of anisotropy in the effective mass and dielectric constant. Up to six residual donor species are observed in material grown by hydride vapor phase epitaxy (HVPE) and metalorganic chemical vapor deposition (MOCVD) from their n=2 and n=3 two-electron satellites observed in PL and by RERS. The donor-related nature of the relevant transitions is confirmed from their magnetic field dependence, and the spectral resolution is improved at high fields. The Si donor level is determined to have a binding energy of about 21 meV from observation of its two-electron satellite in lightly Si-doped HVPE material. The free exciton binding energy is shown to be about 26.4 meV, independent of strain, based on observations of the n=2 free exciton. The room temperature band-edge PL peak is confirmed to be free excitonic in nature, based on its linewidth and on comparison with simple reflectance measurements. Reflectance from the edge of a thick HVPE layer shows clear evidence of A, B, and C excitons obeying the relevant selection rules at both low and room temperature. Surface chemical treatments are shown to have substantial effects on room temperature PL efficiency. Passivation with ammonium or sodium sulfide solutions, in particular, yields increases in PL efficiency by a factor of five to seven over air-exposed surfaces. The passivation effect is stable in air, lasting at least one month.