The Australian experiment with ETS-V

Land-mobile satellite propagation measurements were implemented at L Band (1.5 GHz) in South-Eastern Australia during an 11 day period in October 1988. Transmissions (CW) from both the Japanese ETS-5 and INMARSAT Pacific geostationary satellites were accessed. Previous measurements in this series were performed at both L Band (1.5 GHz) and UHF (870 MHz) in Central Maryland, North-Central Colorado, and the southern United States. The objectives of the Australian campaign were to expand the data base acquired in the U.S. to another continent, to validate a U.S. derived empirical model for estimating the fade distribution, to establish the effects of directive antennas, to assess the isolation between co- and cross-polarized transmissions, to derive estimates of fade as well as non-fade durations, and to evaluate diversity reception. All these objectives were met

Frequency addressable beams for land mobile communications

Satellites used for mobile communications need to serve large numbers of small, low cost terminals. The most important parameters affecting the capacity of such systems are the satellite equivalent isotropically radiated power (EIRP) and gain to noise temperature ratio (G/T) and available bandwidth. Satellites using frequency addressed beams provide high EIRP and G/T with high-gain antenna beams that also permit frequency reuse over the composite coverage area. Frequency addressing is easy to implement and compatible with low-cost terminals and offers higher capacity than alternative approaches

Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)

Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression

Prediction of Satellite Shadowing in Smart Cities with Application to IoT

The combination of satellite direct reception and terrestrial 5G infrastructure is essential to guarantee coverage in satellite based-Internet of Things, mainly in smart cities where buildings can cause high power losses. In this paper, we propose an accurate and fast graphical method for predicting the satellite coverage in urban areas and SatCom on-the-move scenarios. The aim is to provide information that could be useful in the IoT network planning process, e.g., in the decision of how many terrestrial repeaters are really needed and where they should be placed. Experiments show that the shadowed areas predicted by the method correspond almost perfectly with experimental data measured from an Eutelsat satellite in the urban area of Barcelona.Ministerio de Industria, Turismo y Comercio de España TSI-020301-2009-3

Southern Ocean warming: Increase in basal melting and grounded ice loss

We apply a global finite element sea ice/ice shelf/ocean model (FESOM) to the Antarctic marginal seas to analyze projections of ice shelf basal melting in a warmer climate. The model is forced with the atmospheric output from two climate models: (1) the Hadley Centre Climate Model (HadCM3) and (2) Max Planck Institute’s ECHAM5/MPI-OM. Results from their 20th-century simulations are used to evaluate the modeled present-day ocean state. Sea-ice coverage is largely realistic in both simulations. Modeled ice shelf basal melt rates compare well with observations in both cases, but are consistently smaller for ECHAM5/MPI-OM. Projections for future ice shelf basal melting are computed using atmospheric output for IPCC scenarios E1 and A1B. While trends in sea ice coverage, ocean heat content, and ice shelf basal melting are small in simulations forced with ECHAM5 data, a substantial shift towards a warmer regime is found in experiments forced with HadCM3 output. A strong sensitivity of basal melting to increased ocean temperatures is found for the ice shelves in the Amundsen Sea. For the cold-water ice shelves in the Ross and Weddell Seas,decreasing convection on the continental shelf in the HadCM3 scenarios leads to an erosion of the continental slope front and to warm water of open ocean origin entering the continental shelf. As this water reaches deep into the Filchner-Ronne Ice Shelf (FRIS) cavity, basal melting increases by a factor of three to six compared to the present value of about 100 Gt/yr. Highest melt rates at the deep FRIS grounding line causes a retreat of > 200km, equivalent to an land ice loss of 110 Gt/yr

The future of Earth observation in hydrology

In just the past 5 years, the field of Earth observation has progressed beyond the offerings of conventional space-agency-based platforms to include a plethora of sensing opportunities afforded by CubeSats, unmanned aerial vehicles (UAVs), and smartphone technologies that are being embraced by both for-profit companies and individual researchers. Over the previous decades, space agency efforts have brought forth well-known and immensely useful satellites such as the Landsat series and the Gravity Research and Climate Experiment (GRACE) system, with costs typically of the order of 1 billion dollars per satellite and with concept-to-launch timelines of the order of 2 decades (for new missions). More recently, the proliferation of smart-phones has helped to miniaturize sensors and energy requirements, facilitating advances in the use of CubeSats that can be launched by the dozens, while providing ultra-high (3-5 m) resolution sensing of the Earth on a daily basis. Start-up companies that did not exist a decade ago now operate more satellites in orbit than any space agency, and at costs that are a mere fraction of traditional satellite missions. With these advances come new space-borne measurements, such as real-time high-definition video for tracking air pollution, storm-cell development, flood propagation, precipitation monitoring, or even for constructing digital surfaces using structure-from-motion techniques. Closer to the surface, measurements from small unmanned drones and tethered balloons have mapped snow depths, floods, and estimated evaporation at sub-metre resolutions, pushing back on spatio-temporal constraints and delivering new process insights. At ground level, precipitation has been measured using signal attenuation between antennae mounted on cell phone towers, while the proliferation of mobile devices has enabled citizen scientists to catalogue photos of environmental conditions, estimate daily average temperatures from battery state, and sense other hydrologically important variables such as channel depths using commercially available wireless devices. Global internet access is being pursued via high-altitude balloons, solar planes, and hundreds of planned satellite launches, providing a means to exploit the "internet of things" as an entirely new measurement domain. Such global access will enable real-time collection of data from billions of smartphones or from remote research platforms. This future will produce petabytes of data that can only be accessed via cloud storage and will require new analytical approaches to interpret. The extent to which today's hydrologic models can usefully ingest such massive data volumes is unclear. Nor is it clear whether this deluge of data will be usefully exploited, either because the measurements are superfluous, inconsistent, not accurate enough, or simply because we lack the capacity to process and analyse them. What is apparent is that the tools and techniques afforded by this array of novel and game-changing sensing platforms present our community with a unique opportunity to develop new insights that advance fundamental aspects of the hydrological sciences. To accomplish this will require more than just an application of the technology: in some cases, it will demand a radical rethink on how we utilize and exploit these new observing systems

Extreme flood-driven fluvial bank erosion and sediment loads: direct process measurements using integrated Mobile Laser Scanning (MLS) and hydro-acoustic techniques: Direct measurement of flood-driven erosion using MLS and MBES

Copyright © 2016 John Wiley & Sons, Ltd. This methods paper details the first attempt at monitoring bank erosion, flow and suspended sediment at a site during flooding on the Mekong River induced by the passage of tropical cyclones. We deployed integrated mobile laser scanning (MLS) and multibeam echo sounding (MBES), alongside acoustic Doppler current profiling (aDcp), to directly measure changes in river bank and bed at high (~0.05 m) spatial resolution, in conjunction with measurements of flow and suspended sediment dynamics. We outline the methodological steps used to collect and process this complex point cloud data, and detail the procedures used to process and calibrate the aDcp flow and sediment flux data. A comparison with conventional remote sensing methods of estimating bank erosion, using aerial images and Landsat imagery, reveals that traditional techniques are error prone at the high temporal resolutions required to quantify the patterns and volumes of bank erosion induced by the passage of individual flood events. Our analysis reveals the importance of cyclone-driven flood events in causing high rates of erosion and suspended sediment transport, with a c. twofold increase in bank erosion volumes and a fourfold increase in suspended sediment volumes in the cyclone-affected wet season. Copyright © 2016 John Wiley & Sons, Ltd

Communications systems technology assessment study. Volume 2: Results

The cost and technology characteristics are examined for providing special satellite services at UHF, 2.5 GHz, and 14/12 GHz. Considered are primarily health, educational, informational and emergency disaster type services. The total cost of each configuration including space segment, earth station, installation operation and maintenance was optimized to reduce the user's total annual cost and establish preferred equipment performance parameters. Technology expected to be available between now and 1985 is identified and comparisons made between selected alternatives. A key element of the study is a survey of earth station equipment updating past work in the field, providing new insight into technology, and evaluating production and test methods that can reduce costs in large production runs. Various satellite configurations were examined. The cost impact of rain attenuation at Ku-band was evaluated. The factors affecting the ultimate capacity achievable with the available orbital arc and available bandwidth were analyzed

Flood dynamics, surface water retention and availability in the semiarid Cuvelai-Basin, southern Angola and northern Namibia

Located in the western part of the Cuvelai Basin, the Iishana system is a transboundary region covering parts of southern Angola and northern Namibia. Hydrologically, this region is characterized by a network of episodically water-bearing channels in which numerous pans are embedded. These pans, which fill up during the rainy season, form an important water resource for the rural population, especially for agricultural and domestic use. The Iishana system is one of the most densely populated areas in southwestern Africa, and this high population trend is increasing (NamStat 2013). To date, the majority of the population (80–90%) currently lives in rural areas. However, (small) cities are experiencing steady growth. The semi-arid climate in this area has distinct rainy and dry seasons and is characterized by high interannual variability, resulting both in intense droughts and in strong flood events. As a result, water is sometimes a scarce resource in this region. The strong population growth and the temperature increase predicted as a result of global climate change will put further pressure on available water resources. However, as this region is also subject to volatile rainfall dynamics, in addition to droughts, the Iishana system also experiences repeated, severe flood events. Most recently, flood events occurred in 2008 to 2011, 2013, and 2017, resulting in the loss of life, the loss of crop yields and consequent loss of livelihood for many people, and the destruction of key infrastructure elements. To date, there has been no complex 2D-hydrodynamic model for the Iishana system and no transferable modeling approach to identify potential locations for water storage and facilitate the planning and development of flood retention measures. In this study, various methods have been developed and applied to address these issues. This has allowed for the validation of existing findings as well as the discovery of new insights, which are briefly summarized below. First, an investigation was performed to test the influence of topography on hydrology, with a special emphasis on infrastructure elements. The focus here was on improving the raw DEM for subsequent calculations. For this purpose, filter corrections were performed on the TanDEM X raw data, and road dams, culverts, and bridges were recorded by means of kinematic surveys. As a result, the definition of the flow paths was improved. It became clear that northern roads, especially those running from east to west, have a strong influence on the runoff behavior in the study area due to their height and their orientation orthogonal to the water flow of the Iishana. Based on the corrected DEM and the application of a modified Blue Spot Analysis, further new findings emerged. Approximately 190,000 pans with a total storage volume of about 1.9 km³ and a total area of 4,021 km² were identified. The part of the study area located in Angola accounts for two thirds of the potential storage volume while only one third of the storage volume is in Namibia. Furthermore, about one third of all pans are located in the episodically water-bearing channels. Based on previous results in other regions, a calculation of the surface-volume relationship (SA/V rate) was performed for the first time for the Iishana system. This enabled the identification of about 2,000 pans that are primarily suitable for an expansion of storage volume. Using continuous and spatio-temporally varying TRMM precipitation data, a 2D-hydrodynamic modeling and reconstruction of the 2008/2009 flood event was performed using the FloodArea model. Although the results represent a snapshot, they nevertheless contribute to an improved understanding of the interconnected runoff system and highlight potential flood hazards. Depending on the weighting of evapotranspiration in the calculation of the model, the potential storage volume can be quantified between 0.116 km³ and 0.547 km³. The total inundation area was calculated at 1.860 km². In addition, three main runoff paths were identified, of which the central and the eastern runoff paths pose a particular threat to the regional capital of Oshakati. Furthermore, with the help of the model, for the first time it was possible to identify areas where, after the end of the rainy season, water availability is naturally shortest (Namibia) or longest (Angola). Based on these numerous, new results, scenario calculations for neighboring catchments as well as calculations for other precipitation periods can be performed in the future. Thus, the duration of water availability after the end of a rainy season can be determined and possible locations for retention measures can be identified for various locations