756 research outputs found

    An intelligent decision-making system for flood monitoring from space

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    This paper presents the results of a feasibility study on intelligent image processing and decision-making for flood monitoring on board satellites. The ability to detect temporal changes in images is one of the most important functions in intelligent image processing systems for hazard and disaster monitoring applications. An automatic change detection system is proposed, the purpose of which is to monitor particular areas on Earth and give warnings to the authorities if any flooding events are detected. A novel solution to flood detection based on combined use of optical multispectral imagery and GPS reflectometry data is introduced. A fuzzy inference engine is used in the decision-making process, which generates control signals to other subsystems on board the satellite

    Sensing Ocean, Ice and Land Reflected Signalsfrom Space: Results from the UK-DMC GPS Reflectometry Experiment

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    The use of Global Navigation Satellite System (GNSS) signals reflected from the Earth\u27s surface has progressed from its beginnings in the early 1990\u27s to a demonstrated practical linkage of measurements to geophysical characteristics of ocean, ice and land surfaces. A pioneering space-based experiment was carried on the UK-DMC satellite launched in September of 2003. The GPS receiver on the satellite was modified to accommodate a downward (nadir) pointing medium gain antenna and to send sampled IF data to a solid-state data recorder [1]. Since its launch it has been successfully used to target and detect specular reflections of GPS signals after scattering from the Earth\u27s oceans, ice sheetsand land surfaces. All data collections under a wide range of conditions have revealed reflected signals, including signals reflected off the ocean under reasonably rough ocean conditions. This demonstrates convincingly that GNSS Reflectometry (or GNSS Bistatic Radar) is a valid future technology for space based Earth remote sensing, even when using modest antenna gain configurations such as that deployed on the UK-DMC low Earth orbiting satellite. This paper presents a summary of the signals collected from over the ocean, and an examination of the signal relationship to the ocean wind and wave conditions is presented. The preliminary results from ice and land surfaces reflection analysis are also described. Reprinted with permission from The Institute of Navigation (http://ion.org/) and The Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation, (pp. 1679-1685). Fairfax, VA: The Institute of Navigation

    Monthly average wave power spectra for South Uist

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    Response time of mean square slope to wind forcing: An empirical investigation

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    We present an empirical study of the response time of surface wave mean square slope to local wind forcing using data collected over 11 years by 46 discus buoys moored at a wide variety of locations. The response time is defined as the time lag at which the time dependence of the waves exhibits the highest correlation with that of the local wind speed. The response time at each location is found to be fairly stable, with the time varying between 0.4 and 1.8 h depending on the location. Examination of long‐term statistics reveals response time dependencies on wind speed magnitude, fetch, atmospheric stability, and wavelength. With the increasing reliance on satellite microwave remote sensing as a source of wind data, these results provide useful insights and bounds for their use.Key Points:Mean squared slope measured by buoys responds to wind forcing in 0.4–1.8 hThe response time depends on wind speed, fetch, atmospheric stability, and wavelengthPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142436/1/jgrc21693_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142436/2/jgrc21693.pd

    A Nanosatellite to Demonstrate GPS Oceanography Reflectometry

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    This paper describes a proposal for a rapid, low cost, nanosatellite mission to demonstrate the concept of GPS ocean reflectometry and to investigate the feasibility of determining sea state for a future operational space-based storm warning systems. The aims of this mission are to prove the general feasibility of GPS ocean reflectometry, to demonstrate sea state determination and to enable the development of a practical GPS ocean reflectometry payload for future missions. The payloads on the satellite consist of a 24 channel C/A code SGR-10 space GPS receiver and a solid state data recorder. The GPS receiver has one standard RHCP zenith antenna, and one high gain LHCP nadir antenna for receiving the reflected signals. A dual approach is taken to measurement gathering. Initially, bursts of directly sampled IF data are stored and downloaded to permit processing of the data on the ground. Later in the mission, the GPS receiver software may be modified to permit the processing of signals on-board the satellite. The nanosatellite is based on SSTL’s SNAP design and has a projected total mass of around 12 kilograms; orbit average power of approximately 4.8 watts; 3-axis attitude control to 1-2 degrees; VHF uplink, S-band downlink at 500 kbps, and OBC based on the StrongARM SA1100. Using the SNAP design enables a fast manufacture at low cost: estimated at 9 months and around 2 million Euros, including launch. The proposed mission makes use of the Surrey Space Centre Mission Control ground-station in Guildford (UK) for control and data gathering. Surrey Satellite Technology Ltd (SSTL) is a world leader in both nanosatellite and GPS technology for small satellites. SSTL’s highly successful SNAP-1 nanosatellite launched in June 2000 demonstrated the potential of such small spacecraft, and this proposal involves the first ever use of a nanosatellite for a commercial application (GANDER) in collaboration with SOS Ltd (UK) a company specialising in oceanography from space

    Advanced Supported Liquid Membranes for Carbon Dioxide Control in Extravehicular Activity Applications

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    There is disclosed a portable life support system with a component for removal of at least one selected gas. In an embodiment, the system includes a supported liquid membrane having a first side and a second side in opposition to one another, the first side configured for disposition toward an astronaut and the second side configured for disposition toward a vacuum atmosphere. The system further includes an ionic liquid disposed between the first side and the second side of the supported liquid membrane, the ionic liquid configured for removal of at least one selected gas from a region housing the astronaut adjacent the first side of the supported liquid membrane to the vacuum atmosphere adjacent the second side of the supported liquid membrane. Other embodiments are also disclosed

    Interactive Video: A Report from the ACE Western Regional Workshop

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    The ACE workgroup involved communicators, educators and subject specialists from a number of states and Canada

    The Drought Monitor

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    There is a need for improved drought monitoring and assessment methods in the United States. Drought is the most costly natural disaster [Federal Emergency Management Agancy (FEMA 1995; Wilhite 2000)], but it is often neglected by developers of assessment and forecast products. Drought is more nebulous than other disasters and does not lend itself to traditional assessments or forecast methods. Its relatively slow onset and the complexity of its impacts are reasons for the new assessment methodology. Improvements in drought monitoring and forecasting techniques will allow for better preparation, lead to better management practices, and reduce the vulnerability of society to drought and its subsequent impacts. The Drought Monitor (additional information available online at http://drought.unl/edu/dm) was created with the goal of tracking and displaying the magnitude and spatial extent of drought and its impacts across the United States. The Drought Monitor is produced weekly and classifies drought severity into four major categories, with a fifth category threshold assigned to locations on a map are determined from a number of indicators, or tools, blended with subjective interpretation
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