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Article

Frans von der Dunk

International satellite law can best be described as that subset of international space law that addresses the operations of satellites in orbit around the Earth. Excluding, therefore, topics such as manned space flight, suborbital space operations, and any activities beyond Earth orbits, this means addressing the use of satellites for telecommunications purposes, for Earth observation and remote sensing, and for positioning, timing, and navigation. These three major sectors of space activities are, in addition to jointly being subject to the body of international space law, each subject to their specific dedicated legal regime—international satellite communications law, international satellite remote sensing law, and international satellite navigation law.

Article

Probing the interiors of the gaseous giant planets in our solar system is not an easy task. It requires a set of accurate measurements combined with theoretical models that are used to infer the planetary composition and its depth dependence. The masses of Jupiter and Saturn are 317.83 and 95.16 Earth masses (M ⊕ ), respectively, and since a few decades, it has been known that they mostly consist of hydrogen and helium. The mass of heavy elements (all elements heavier than helium) is not well determined, nor are their distribution within the planets. While the heavy elements are not the dominating materials inside Jupiter and Saturn, they are the key to understanding the planets’ formation and evolutionary histories. The planetary internal structure is inferred from theoretical models that fit the available observational constraints by using theoretical equations of states (EOSs) for hydrogen, helium, their mixtures, and heavier elements (typically rocks and/or ices). However, there is no unique solution for determining the planetary structure and the results depend on the used EOSs as well as the model assumptions imposed by the modeler. Major model assumptions that can affect the derived internal structure include the number of layers, the heat transport mechanism within the planet (and its entropy), the nature of the core (compact vs. diluted), and the location (pressure) of separation between the two envelopes. Alternative structure models assume a less distinct division between the layers and /or a non-homogenous distribution of the heavy elements. The fact that the behavior of hydrogen at high pressures and temperatures is not perfectly known and that helium may separate from hydrogen at the deep interior add sources of uncertainty to structure models. In the 21st century, with accurate measurements of the gravitational fields of Jupiter and Saturn from the Juno and Cassini missions, structure models can be further constrained. At the same time, these measurements introduce new challenges for planetary modelers.

Article

Elina Morozova and Yaroslav Vasyanin

International space law is a branch of international law that regulates the conduct of space activities. Its core instruments include five space-specific international treaties, which were adopted under the auspices of the United Nations. The first and the underlying one—the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies (Outer Space Treaty)—establishes that outer space is free for exploration and use by all states. Such fundamental freedom is exercised by a number of space applications that have become an integral part of modern human life and global economy. Among such applications, satellite telecommunications is the most widespread, essential, and advanced. Indeed, since 1957 when the Soviet Union launched Sputnik 1, the first artificial satellite merely capable of continuous beeping during its 21-day trip around the globe, space technologies have progressed in leaps and bounds. Cutting-edge satellite telecommunications methods ensure instant delivery of huge amounts of data, relay of real-time voice and video, broadcasting of radio and television, and Internet access worldwide. By transmitting signals over any distance telecommunications satellites connect locations everywhere on Earth. A telecommunications satellite’s lifetime, starting from the launch and ending at de-orbiting, is governed by international space law. The latter considers satellites as “space objects” and regulates liability, registration, jurisdiction and control, debris mitigation, and touches upon ownership. Therefore, the first large group of international law rules applicable to satellite telecommunications includes provisions of three out of five UN space treaties, specifically, the 1967 Outer Space Treaty, the 1972 Convention on International Liability for Damage Caused by Space Objects, and the 1976 Convention on Registration of Objects Launched into Outer Space, as well as several UN General Assembly resolutions. To carry out a communication function, satellites need to be placed in a certain orbit and to use radio-frequency spectrum, both limited natural resources. Access to these highly demanded resources, which are not subject to national appropriation and require rational, efficient, and economical uses in an interference-free environment, is managed by the International Telecommunication Union (ITU)—the UN specialized agency for information and communication technologies. The ITU’s core regulatory documents are its Constitution, Convention, and the Radio Regulations, which collectively make up another group of international law rules relevant to satellite telecommunications. Both groups of international law rules constitute the international legal regime of satellite telecommunications and face the challenge of keeping pace with technology advancement and market evolution, as well as with a growing number of states and non-state actors carrying on space activities. These tangible changes need to be addressed in the regulatory framework that cannot but serve as a driver for further development of satellite telecommunications.

Article

Climate data support a suite of scientific and socioeconomic activities that can reinforce development gains and improve the lives of those most vulnerable to climate variability and change. Historical and current weather and climate observations are essential for many activities, including operational meteorology, identifying extreme events and assessing associated risks, developing climate-informed early warning systems, planning, and research. Rainfall is the most widely available and used climate variable. Thus, measurement of rainfall is crucial to society’s well-being. In general, measurements from ground meteorological stations managed by National Meteorological Agencies are the principal sources of rainfall data. The main strength of the station observations is that they are assumed to give the “true” measurements of rainfall. However, the distribution of the meteorological observation network over Africa is significantly inadequate, with declining numbers of stations and poor data quality. This problem is compounded by the fact that the distribution of existing stations is uneven, with most weather stations located in cities and towns along major roads. As a result, coverage tends to be worse in rural areas, where livelihoods may be most vulnerable to climate variability and change. This has resulted in critical gaps in the provision of climate services where it is needed the most. Space-based measurements from satellites are being used as a complement to or in place of ground observations. Satellite-derived precipitation estimates offer good spatial coverage and improved temporal and spatial resolution, as well as near-real-time availability. Moreover, a range of satellite rainfall products are freely available from many sources, and a couple of these products are available only for Africa. However, satellite rainfall products also suffer from many shortcomings that include accuracy, particularly at higher temporal resolutions; coarse spatial resolution; short time series; and temporal inhomogeneity due to varying inputs. This limits the use of the use these products for certain applications. Understanding satellite rainfall estimation errors is critical for deciding which products might be used for specific applications and requires rigorous evaluation of these products using ground observations. The challenge in Africa is lack of availability, accessibility, and quality of rain-gauge observations that could be used for this purpose. Despite these challenges, there have been some validation efforts over different parts of the continent. However, different and inconsistent approaches of validation have created challenges to using these evaluation results. A comprehensive validation of the main operational satellite products at a continental level is needed to overcome these challenges and make the best use of satellite rainfall products in different applications.

Article

Athena Coustenis

Titan, Saturn’s largest satellite, is one of the most intriguing moons in our Solar System, in particular because of its dense and extended nitrogen-based and organic-laden atmosphere. Other unique features include a methanological cycle similar to the Earth’s hydrological one, surface features similar to terrestrial ones, and a probable under-surface liquid water ocean. Besides the dinitrogen main component, the gaseous content includes methane and hydrogen, which, through photochemistry and photolysis, produce a host of trace gases such as hydrocarbons and nitriles. This very advanced organic chemistry creates layers of orange-brown haze surrounding the satellite. The chemical compounds diffuse downward in the form of aerosols and condensates and are finally deposited on the surface. There is very little oxygen in the atmosphere, mainly in the form of H2O, CO, and CO2. The atmospheric chemical and thermal structure varies significantly with seasons, much like on Earth, albeit on much longer time scales. Extensive analysis of Titan data from ground, Earth-orbiting observatories, and space missions, like those returned by the 13-year operating Cassini-Huygens spacecraft, reveals a complex system with strong interactions among the atmosphere, the surface, and the interior. The processes operating in the atmosphere are informative of what occurs on Earth and give hints as to the origin and evolution of our outer Solar System.

Article

This article consists of three sections. The first discusses how we determine satellite internal structures and what we know about them. The primary probes of internal structure are measurements of magnetic induction, gravity, and topography, as well as rotation state and orientation. Enceladus, Europa, Ganymede, Callisto, Titan, and (perhaps) Pluto all have subsurface oceans; Callisto and Titan may be only incompletely differentiated. The second section describes dynamical processes that affect satellite interiors and surfaces: tidal and radioactive heating, flexure and relaxation, convection, cryovolcanism, true polar wander, non-synchronous rotation, orbital evolution, and impacts. The final section discusses how the satellites formed and evolved. Ancient tidal heating episodes and subsequent refreezing of a subsurface ocean are the likeliest explanation for the deformation observed at Ganymede, Tethys, Dione, Rhea, Miranda, Ariel, and Titania. The high heat output of Enceladus is a consequence of Saturn’s highly dissipative interior, but the dissipation rate is strongly frequency-dependent and does not necessarily imply that Saturn’s moons are young. Major remaining questions include the origins of Titan’s atmosphere and high eccentricity, the regular density progression in the Galilean satellites, and the orbital evolution of the Saturnian and Uranian moons.

Article

Irina Sokolik

There is scientific consensus that human activities have been altering the atmospheric composition and are a key driver of global climate and environmental changes since pre-industrial times (IPCC, 2013). It is a pressing priority to understand the Earth system response to atmospheric aerosol input from diverse sources, which so far remain one of the largest uncertainties in climate studies (Boucher et al., 2014; Forster et al., 2007). As the second most abundant component (in terms of mass) of atmospheric aerosols, mineral dust exerts tremendous impacts on Earth’s climate and environment through various interaction and feedback processes. Dust can also have beneficial effects where it deposits: Central and South American rain forests get most of their mineral nutrients from the Sahara; iron-poor ocean regions get iron; and dust in Hawaii increases plantain growth. In northern China as well as the midwestern United States, ancient dust storm deposits known as loess are highly fertile soils, but they are also a significant source of contemporary dust storms when soil-securing vegetation is disturbed. Accurate assessments of dust emission are of great importance to improvements in quantifying the diverse dust impacts.

Article

Guy J.-P. Schumann

For about 40 years, with a proliferation over the last two decades, remote sensing data, primarily in the form of satellite and airborne imagery and altimetry, have been used to study floods, floodplain inundation, and river hydrodynamics. The sensors and data processing techniques that exist to derive information about floods are numerous. Instruments that record flood events may operate in the visible, thermal, and microwave range of the electromagnetic spectrum. Due to the limitations posed by adverse weather conditions during flood events, radar (microwave range) sensors are invaluable for monitoring floods; however, if a visible image of flooding can be acquired, retrieving useful information from this is often more straightforward. During recent years, scientific contributions in the field of remote sensing of floods have increased considerably, and science has presented innovative research and methods for retrieving information content from multi-scale coverages of disastrous flood events all over the world. Progress has been transformative, and the information obtained from remote sensing of floods is becoming mature enough to not only be integrated with computer simulations of flooding to allow better prediction, but also to assist flood response agencies in their operations. Furthermore, this advancement has led to a number of recent and upcoming satellite missions that are already transforming current procedures and operations in flood modeling and monitoring, as well as our understanding of river and floodplain hydrodynamics globally. Global initiatives that utilize remote sensing data to strengthen support in managing and responding to flood disasters (e.g., The International Charter, The Dartmouth Flood Observatory, CEOS, NASA’s Servir and the European Space Agency’s Tiger-Net initiatives), primarily in developing nations, are becoming established and also recognized by many nations that are in need of assistance because traditional ground-based monitoring systems are sparse and in decline. The value remote sensing can offer is growing rapidly, and the challenge now lies in ensuring sustainable and interoperable use as well as optimized distribution of remote sensing products and services for science as well as operational assistance.

Article

Throughout the history of human activity in outer space, the role of private companies has steadily grown, and, in some cases, companies have even replaced government agencies as the primary actors in space. As private space activity has grown and diversified, the laws and regulations that govern private actors have been forced to evolve in reaction to the new realities of the industry. On the international level, the treaties concluded in the 1960s and 1970s continue to be in force today. However, these treaties only govern state activity in space. The rules regulating private industry are necessarily domestic in nature, and it is in these domestic laws that the evolution of space law can be most clearly seen. That said, new industries, such as asteroid mining, are testing the limits of international law and have forced the international community to examine whether changes to long-standing laws are needed.

Article

As we find ourselves bearing witness—even in our own backyards—to what is increasingly being referred to as the “drone revolution,” it might be a good time to turn our attention back in time and figure out how, exactly, we got here. The large-scale use of drones for national defense and law enforcement is a relatively recent development, but unmanned aerial surveillance draws from a doctrine that is as old as flight itself. Though the fundamental logic of aerial surveillance has remained the same—to put an eye in the sky so that one may look down upon one’s enemies—the technology has evolved dramatically over this period, driving shifts in aerial surveillance theory and practice. New technologies enable new techniques that, in turn, inspire new ways of thinking about how to spy from the sky, and produce new experiences for those being watched. Our present drone revolution, which has itself driven what is being called the “intelligence, surveillance, and reconnaissance (ISR) revolution,” is the result of this process played out over an entire century. The unmanned aerial spying efforts of the United States military and intelligence community have a particularly long and influential history, beginning with the Union Army’s manned observation balloon corps of the Civil War. Our story begins, in earnest, with fragile and failure-prone “aerial torpedos” in the First World War and an innovative and overlooked live video transmission system from the 1930s, through the CIA’s little-known—and radically forward-thinking—Samos spy satellite program of the late 1950s and a series of extraordinarily ambitious Cold War drone programs, up to the adoption of drones over Bosnia in the 1990s. Together, these episodes show how we got the drones of today and realized the core principles that define aerial spycraft (that is, how to find and watch “the bad guys”) in the 21st century: cover as much ground as possible; process and disseminate what you collect as quickly as possible, ideally, as close as you can get to real-time; and be as persistent as possible. The drones and high-resolution aerial cameras that are finding their way into the tool-kits of police departments will bring these principles along with them. Even if the growing number of law enforcement officers now using this technology aren’t fully aware of the long legacy of aerial surveillance that they are joining, the influence of this formative history of surveillance on their aerial crime-fighting operations is evident. Just as aerial surveillance transformed the battlefield, it will have a similarly profound effect on the experience and tactics of those operating the cameras, as well as, crucially, those individuals being watched by them. By grasping this history, we can better understand not only why and how drones are being used to fight crime, but also what to expect when every police department in the country owns an eye in the sky.

Article

Pascal Rosenblatt, Ryuki Hyodo, Francesco Pignatale, Antony Trinh, Sebastien Charnoz, Kevin Dunseath, Mariko Dunseath-Terao, and Hidenori Genda

The origin of the natural satellites or moons of the solar system is as challenging to unravel as the formation of the planets. Before the start of the space probe exploration era, this topic of planetary science was restricted to telescopic observations, which limited the possibility of testing different formation scenarios. This era has considerably boosted this topic of research, particularly after the Apollo missions returned samples from the Moon’s surface to Earth. Observations from subsequent deep space missions such as Viking 1 and 2 Orbiters, Voyager 1 and 2, Phobos-2, Galileo, Cassini-Huygens, and the most recent Mars orbiters such as Mars Express, as well as from the Hubble space telescope, have served to intensify research in this area. Each moon system has its own specificities, with different origins and histories. It is widely accepted that the Earth’s Moon formed after a giant collision between the proto-Earth and a body similar in size to Mars. The Galilean moons of Jupiter, on the other hand, appear to have formed by accretion in a circum-Jovian disk, while smaller, irregularly shaped satellites were probably captured by the giant planet. The small and medium-sized Saturnian moons may have formed from the rings encircling the planet. Among the terrestrial planets, Mercury and Venus have no moons, the Earth has a single large moon, and Mars has two very small satellites. This raises some challenging questions: What processes can lead to moon formation around terrestrial planets and what parameters determine the possible outcomes, such as the number and size of moons? The answer to such fundamental questions necessarily entails a thorough understanding of the formation of the Martian system and may have relevance to the possible existence of (exo)moons orbiting exoplanets. The formation of such exomoons is of great importance as they could influence conditions for habitability or for maintaining life over long periods of time on the surface of Earth-like exoplanets, for example by limiting the variations of the orientation of the planet’s rotation axis and thus preventing frequent changes of its climate. Our current knowledge concerning the origin of Phobos and Deimos has been acquired from observational data as well as theoretical work. Early observations led to the idea that the two satellites were captured asteroids but this created difficulties in reconciling the current orbits of Phobos and Deimos with those of captured bodies, hence suggesting the need for an alternative theory. A giant-impact scenario provides a description of how moons similar to Phobos and Deimos can be formed in orbits similar to those observed today. This scenario also restricts the range of possible composition of the two moons, providing a motivation for future missions that aim for the first time to bring material from the Martian system back to Earth.

Article

Forecasting severe convective weather remains one of the most challenging tasks facing operational meteorology today, especially in the mid-latitudes, where severe convective storms occur most frequently and with the greatest impact. The forecast difficulties reflect, in part, the many different atmospheric processes of which severe thunderstorms are a by-product. These processes occur over a wide range of spatial and temporal scales, some of which are poorly understood and/or are inadequately sampled by observational networks. Therefore, anticipating the development and evolution of severe thunderstorms will likely remain an integral part of national and local forecasting efforts well into the future. Modern severe weather forecasting began in the 1940s, primarily employing the pattern recognition approach throughout the 1950s and 1960s. Substantial changes in forecast approaches did not come until much later, however, beginning in the 1980s. By the start of the new millennium, significant advances in the understanding of the physical mechanisms responsible for severe weather enabled forecasts of greater spatial and temporal detail. At the same time, technological advances made available model thermodynamic and wind profiles that supported probabilistic forecasts of severe weather threats. This article provides an updated overview of operational severe local storm forecasting, with emphasis on present-day understanding of the mesoscale processes responsible for severe convective storms, and the application of recent technological developments that have revolutionized some aspects of severe weather forecasting. The presentation, nevertheless, notes that increased understanding and enhanced computer sophistication are not a substitute for careful diagnosis of the current meteorological environment and an ingredients-based approach to anticipating changes in that environment; these techniques remain foundational to successful forecasts of tornadoes, large hail, damaging wind, and flash flooding.

Article

The global water cycle concept has its roots in the ancient understanding of nature. Indeed, the Greeks and Hebrews documented some of the most some important hydrological processes. Furthermore, Africa, Sri Lanka, and China all have archaeological evidence to show the sophisticated nature of water management that took place thousands of years ago. During the 20th century, a broader perspective was taken and the hydrological cycle was used to describe the terrestrial and freshwater component of the global water cycle. Data analysis systems and modeling protocols were developed to provide the information needed to efficiently manage water resources. These advances were helpful in defining the water in the soil and the movement of water between stores of water over land surfaces. Atmospheric inputs to these balances were also monitored, but the measurements were much more reliable over countries with dense networks of precipitation gauges and radiosonde observations. By the 1960s, early satellites began to provide images that gave a new perception of Earth processes, including a more complete realization that water cycle components and processes were continuous in space and could not be fully understood through analyses partitioned by geopolitical or topographical boundaries. In the 1970s, satellites delivered quantitative radiometric measurements that allowed for the estimation of a number of variables such as precipitation and soil moisture. In the United States, by the late 1970s, plans were made to launch the Earth System Science program, led by the National Aeronautics and Space Agency (NASA). The water component of this program integrated terrestrial and atmospheric components and provided linkages with the oceanic component so that a truly global perspective of the water cycle could be developed. At the same time, the role of regional and local hydrological processes within the integrated “global water cycle” began to be understood. Benefits of this approach were immediate. The connections between the water and energy cycles gave rise to the Global Energy and Water Cycle Experiment (GEWEX)1 as part of the World Climate Research Programme (WCRP). This integrated approach has improved our understanding of the coupled global water/energy system, leading to improved prediction models and more accurate assessments of climate variability and change. The global water cycle has also provided incentives and a framework for further improvements in the measurement of variables such as soil moisture, evapotranspiration, and precipitation. In the past two decades, groundwater has been added to the suite of water cycle variables that can be measured from space. New studies are testing innovative space-based technologies for high-resolution surface water level measurements. While many benefits have followed from the application of the global water cycle concept, its potential is still being developed. Increasingly, the global water cycle is assisting in understanding broad linkages with other global biogeochemical cycles, such as the nitrogen and carbon cycles. Applications of this concept to emerging program priorities, including the Sustainable Development Goals (SDGs) and the Water-Energy-Food (W-E-F) Nexus, are also yielding societal benefits.

Article

Martin Hilpert

The term lexicalization describes the addition of new open-class elements to a repository of holistically processed linguistic units. At the basis of lexicalization are word-formation processes such as affixation, compounding, or borrowing, which are a necessary precondition for lexicalization. Still, lexicalization goes beyond word formation in important respects. First, lexicalization also involves multi-word expressions and set phrases; second, it includes a range of processes that follow the coinage of a new element. These processes conjointly lead to holistic processing, that is, the cognitive treatment of a linguistic element as a unified whole. Holistic processing contrasts with analytic processing, which is the cognitive treatment of a linguistic unit as a complex whole that is composed of several parts. Lexicalization is usefully contrasted with grammaticalization, that is, the emergence of new linguistic units that fulfill grammatical functions. Finally, lexicalization is also a concept that lends itself to the study of cross-linguistic differences in the types of meaning that are lexicalized in specific domains such as, for example, motion.

Article

Shortly after the launch of the first manmade satellite in 1957, the United Nations (UN) took the lead in formulating international rules governing space activities. The five international conventions (the 1967 Outer Space Treaty, the 1968 Rescue Agreement, the 1972 Liability Convention, the 1975 Registration Convention, and the 1979 Moon Agreement) within the UN framework constitute the nucleus of space law, which laid a solid legal foundation securing the smooth development of space activities in the next few decades. Outer space was soon found to be a place with abundant opportunities for commercialization. Telecommunications services proved to be the first successful space commercial application, to be followed by remote sensing and global navigation services. In the last decade, the rapid development of space technologies has brought space tourism and space mining to the forefront of space commercialization. With more and more commercial activities taking place on a daily basis from the 1980s, the existing space law faces severe challenges. The five conventions, enacted in a time when space was monopolized by two superpowers, failed to take into account the commercial aspect of space activities. While there is an urgent need for new rules to deal with the ongoing trend of space commercialization, international society faces difficulties in adopting new rules due to diversified concerns over national interests and adjusts the legislative strategies by enacting soft laws. In view of the difficulty in adopting legally binding rules at the international level, states are encouraged to enact their own national space legislation providing sufficient guidance for their domestic space commercial activities. In the foreseeable future, it is expected that the development of soft laws and national space legislation will be the mainstream regulatory activities in the space field, especially for commercial space activities.

Article

Current communications research takes up the political and ethical problems posed by new surveillance technologies in public space, ranging from biometric technologies adopted by state security apparatuses to self- and peer-monitoring applications for the consumer market. In addition to studies that examine new surveillance technologies, scholars are tracking intensive and extensive expansions of surveillance in the name of risk management. Much of the scholarship produced in the last 15 years looks at how the establishment and expansion of the Department of Homeland Security within the United States and its international counterparts have dramatically altered security, military, and legal practices and cultures. Within this context what were once science fiction dystopias have become funded research and development projects and institutionalized practices aimed at remote data collection and processing, including facial recognition technology and a variety of remote sensing devices. Private-public partnerships between companies like Google and Homeland Security fusion centers have made it possible to use GPS technology to network data that promises to help manage a variety of natural and man-made disasters.