WorldWideScience

Sample records for satellite communications general

  1. Satellite Communications

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Satellite Communications. Arthur C Clarke wrote a seminal paper in 1945 in wireless world. Use three satellites in geo-synchronous orbit to enable intercontinental communications. System could be realised in '50 to 100 years'

  2. Satellite Communications

    CERN Document Server

    Pelton, Joseph N

    2012-01-01

    The field of satellite communications represents the world's largest space industry. Those who are interested in space need to understand the fundamentals of satellite communications, its technology, operation, business, economic, and regulatory aspects. This book explains all this along with key insights into the field's future growth trends and current strategic challenges. Fundamentals of Satellite Communications is a concise book that gives all of the key facts and figures as well as a strategic view of where this dynamic industry is going. Author Joseph N. Pelton, PhD, former Dean of the International Space University and former Director of Strategic Policy at Intelstat, presents a r

  3. Trends in communications satellites

    CERN Document Server

    Curtin, Denis J

    1979-01-01

    Trends in Communications Satellites offers a comprehensive look at trends and advances in satellite communications, including experimental ones such as NASA satellites and those jointly developed by France and Germany. The economic aspects of communications satellites are also examined. This book consists of 16 chapters and begins with a discussion on the fundamentals of electrical communications and their application to space communications, including spacecraft, earth stations, and orbit and wavelength utilization. The next section demonstrates how successful commercial satellite communicati

  4. Satellite Communications for ATM

    Science.gov (United States)

    Shamma, Mohammed A.

    2003-01-01

    This presentation is an overview on Satellite Communication for the Aeronautical Telecommunication Management (ATM) research. Satellite Communications are being considered by the FAA and NASA as a possible alternative to the present and future ground systems supporting Air Traffic Communications. The international Civil Aviation Organization (ICAO) have in place Standards and Recommended Practices (SARPS) for the Aeronautical Mobile Satellite Services (AMSS) which is mainly derived from the pre-existing Inmarsat service that has been in service since the 1980s. The Working Group A of the Aeronautical Mobile Communication Panel of ICAO has also been investigating SARPS for what is called the Next Generation Satellite Service (NGSS) which conforms less to the Inmarsat based architecture and explores wider options in terms of satellite architectures. Several designs are being proposed by Firms such as Boeing, ESA, NASA that are geared toward full or secondary usage of satellite communications for ATM. Satellite communications for ATM can serve several purposes ranging from primary usage where ground services would play a minimal backup role, to an integrated solution where it will be used to cover services, or areas that are less likely to be supported by the proposed and existing ground infrastructure. Such Integrated roles can include usage of satellite communications for oceanic and remote land areas for example. It also can include relieving the capacity of the ground network by providing broadcast based services of Traffic Information Services messages (TIS-B), or Flight Information Services (FIS-B) which can take a significant portion of the ground system capacity. Additionally, satellite communication can play a backup role to support any needs for ground replacement, or additional needed capacity even after the new digital systems are in place. The additional bandwidth that can be provided via satellite communications can also open the door for many new

  5. ESA's satellite communications programme

    Science.gov (United States)

    Bartholome, P.

    1985-02-01

    The developmental history, current status, and future plans of the ESA satellite-communications programs are discussed in a general survey and illustrated with network diagrams and maps. Consideration is given to the parallel development of national and European direct-broadcast systems and telecommunications networks, the position of the European space and electronics industries in the growing world market, the impact of technological improvements (both in satellite systems and in ground-based networks), and the technological and commercial advantages of integrated space-terrestrial networks. The needs for a European definition of the precise national and international roles of satellite communications, for maximum speed in implementing such decisions (before the technology becomes obsolete), and for increased cooperation and standardization to assure European equipment manufacturers a reasonable share of the market are stressed.

  6. Communication satellite applications

    Science.gov (United States)

    Pelton, Joseph N.

    The status and future of the technologies, numbers and services provided by communications satellites worldwide are explored. The evolution of Intelsat satellites and the associated earth terminals toward high-rate all-digital telephony, data, facsimile, videophone, videoconferencing and DBS capabilities are described. The capabilities, services and usage of the Intersputnik, Eutelsat, Arabsat and Palapa systems are also outlined. Domestic satellite communications by means of the Molniya, ANIK, Olympus, Intelsat and Palapa spacecraft are outlined, noting the fast growth of the market and the growing number of different satellite manufacturers. The technical, economic and service definition issues surrounding DBS systems are discussed, along with presently operating and planned maritime and aeronautical communications and positioning systems. Features of search and rescue and tracking, data, and relay satellite systems are summarized, and services offered or which will be offered by every existing or planned communication satellite worldwide are tabulated.

  7. Domestic Communication Satellites

    Science.gov (United States)

    Horowitz, Andrew

    1974-01-01

    A discussion of the Federal Communications Commission's new policy on domestic satellites in light of our 1) military and economic history; 2) corporate interests; 3) citizen surveillance; and 4) media control. (HB)

  8. Living antennas on communication satellites

    DEFF Research Database (Denmark)

    Lumholt, Michael

    2003-01-01

    Crises change the global pattern of communication. The communications problems occur because the satellites are optimized to cover specific geographic areas, and these areas cannot be altered once the satellites are in Earth orbit. An effective solution to the problem is to equip communication sa...... satellites with "living" antennas that can adjust their radiation coverage areas according to the new demands. The development of living antennas is, therefore, among the focus areas identified and supported by the European Space Agency, ESA....

  9. Encryption protection for communication satellites

    Science.gov (United States)

    Sood, D. R.; Hoernig, O. W., Jr.

    In connection with the growing importance of the commercial communication satellite systems and the introduction of new technological developments, users and operators of these systems become increasingly concerned with aspects of security. The user community is concerned with maintaining confidentiality and integrity of the information being transmitted over the satellite links, while the satellite operators are concerned about the safety of their assets in space. In response to these concerns, the commercial satellite operators are now taking steps to protect the communication information and the satellites. Thus, communication information is being protected by end-to-end encryption of the customer communication traffic. Attention is given to the selection of the NBS DES algorithm, the command protection systems, and the communication protection systems.

  10. Satellite communications principles and applications

    CERN Document Server

    Calcutt, David

    1994-01-01

    Satellites are increasingly used for global communications, as well as for radio and television transmissions. With the growth of mobile communications, and of digital technology, the use of satellite systems is set to expand substantially and already all students of electronics or communications engineering must study the subject.This book steers a middle path between offering a basic understanding of the process of communication by satellite and the methodology used; and the extensive mathematical analysis normally adopted in similar texts. It presents the basic concepts, using as mu

  11. Trends in mobile satellite communication

    Science.gov (United States)

    Johannsen, Klaus G.; Bowles, Mike W.; Milliken, Samuel; Cherrette, Alan R.; Busche, Gregory C.

    1993-01-01

    Ever since the U.S. Federal Communication Commission opened the discussion on spectrum usage for personal handheld communication, the community of satellite manufacturers has been searching for an economically viable and technically feasible satellite mobile communication system. Hughes Aircraft Company and others have joined in providing proposals for such systems, ranging from low to medium to geosynchronous orbits. These proposals make it clear that the trend in mobile satellite communication is toward more sophisticated satellites with a large number of spot beams and onboard processing, providing worldwide interconnectivity. Recent Hughes studies indicate that from a cost standpoint the geosynchronous satellite (GEOS) is most economical, followed by the medium earth orbit satellite (MEOS) and then by the low earth orbit satellite (LEOS). From a system performance standpoint, this evaluation may be in reverse order, depending on how the public will react to speech delay and collision. This paper discusses the trends and various mobile satellite constellations in satellite communication under investigation. It considers the effect of orbital altitude and modulation/multiple access on the link and spacecraft design.

  12. Satellite Communications Industry

    Science.gov (United States)

    1993-04-01

    Ariane $loom SAJAC 1 Hughes Satellite Japan 06/94 $150m SAJAC 2 Hughes Satellite Japan -- (spare) $150m SatcomHl GE GE Americom /95 $50m SOLIDARIDAD ...1 Hughes SCT (Mexico) 11/93 Ariane $loom SOLIDARIDAD 2 Hughes SCT (Mexico) /94 $loom Superbird Al Loral Space Com Gp (Jap) 11/92 Ariane $175m

  13. Satellite Communications Using Commercial Protocols

    Science.gov (United States)

    Ivancic, William D.; Griner, James H.; Dimond, Robert; Frantz, Brian D.; Kachmar, Brian; Shell, Dan

    2000-01-01

    NASA Glenn Research Center has been working with industry, academia, and other government agencies in assessing commercial communications protocols for satellite and space-based applications. In addition, NASA Glenn has been developing and advocating new satellite-friendly modifications to existing communications protocol standards. This paper summarizes recent research into the applicability of various commercial standard protocols for use over satellite and space- based communications networks as well as expectations for future protocol development. It serves as a reference point from which the detailed work can be readily accessed. Areas that will be addressed include asynchronous-transfer-mode quality of service; completed and ongoing work of the Internet Engineering Task Force; data-link-layer protocol development for unidirectional link routing; and protocols for aeronautical applications, including mobile Internet protocol routing for wireless/mobile hosts and the aeronautical telecommunications network protocol.

  14. SDR Implementation for Satellite Communication

    OpenAIRE

    Jakobsson, Carin; Sjödin, Olof

    2017-01-01

    SDR (Software Defined Radio) is a radio communicationsystem that has been of great interest and developmentover the last 20 years. It decreases communication costs significantlyas it replaces expensive analogue system components withcheap and flexible digital ones. In this article we describe anSDR implementation for communication with the SEAM (SmallExplorer for Advances Missions) satellite, a CubeSat satellitethat will perform high quality magnetic measurements in theEarth orbit. The projec...

  15. Next generation satellite communications networks

    Science.gov (United States)

    Garland, P. J.; Osborne, F. J.; Streibl, I.

    The paper introduces two potential uses for new space hardware to permit enhanced levels of signal handling and switching in satellite communication service for Canada. One application involves increased private-sector services in the Ku band; the second supports new personal/mobile services by employing higher levels of handling and switching in the Ka band. First-generation satellite regeneration and switching experiments involving the NASA/ACTS spacecraft are described, where the Ka band and switching satellite network problems are emphasized. Second-generation satellite development is outlined based on demand trends for more packet-based switching, low-cost earth stations, and closed user groups. A demonstration mission for new Ka- and Ku-band technologies is proposed, including the payload configuration. The half ANIK E payload is shown to meet the demonstration objectives, and projected to maintain a fully operational payload for at least 10 years.

  16. Clock Management Data Analysis for Satellite Communications

    National Research Council Canada - National Science Library

    Gross, Rachel; Melkers, Raimond

    2005-01-01

    The U.S. Naval Research Laboratory has installed GPS-based timing systems in several Defense Satellite Communication System "DSCS-III" satellite communication facilities to support the Single Channel Transponder "SCT" program...

  17. Satellite communications: possibilities and problems

    International Nuclear Information System (INIS)

    Hine, M.

    1986-01-01

    Communication links via satellites are becoming available in Europe, both as part of the development of the telephone system and as special services aimed at data traffic. They offer the possibility of speeds between 50 kb/s and 2 Mb/s, without the problems and long term commitments of long distance land lines. Such links are provided by the PTT's as circuits which can be booked for variable periods, and have error rates which can be very low and well controlled. Problems in networking can arise from the satellite delay, particularly if errors occur in the local connections, and from the leased circuit and tariff philosophies of the PTT's. (Auth.)

  18. Hybrid Maritime Satellite Communication Antenna

    DEFF Research Database (Denmark)

    Smith, Thomas Gunst

    Hybrid antennas for a maritime satellite communication terminal with simultaneous operation at L- and Ka-band have been investigated. The frequency bands of interest are 1; 525:0 1; 660:5 MHz (RX+TX, RHCP), 19:7 20:2 (RX, LHCP) and 29:5 30:0 GHz (TX, RHCP), which are all part of the Inmarsat BGAN...

  19. Leveraging the NPS Femto Satellite for Alternative Satellite Communication Networks

    Science.gov (United States)

    2017-09-01

    programmed for eventual integration with the Iridium Network , which is then tested. C. THESIS ORGANIZATION The thesis addresses these questions...NPS FEMTO SATELLITE FOR ALTERNATIVE SATELLITE COMMUNICATION NETWORKS by Faisal S. Alshaya September 2017 Co-Advisors: Steven J. Iatrou...TYPE AND DATES COVERED Master’s thesis 4. TITLE AND SUBTITLE LEVERAGING THE NPS FEMTO SATELLITE FOR ALTERNATIVE SATELLITE COMMUNICATION NETWORKS 5

  20. Experiment In Aeronautical-Mobile/Satellite Communication

    Science.gov (United States)

    Jedrey, Thomas C.; Lay, Norman E.; Dessouky, Khaled

    1992-01-01

    Report describes study of performance of digital mobile/satellite communication terminals of advanced design intended for use in ground stations and airplanes in aeronautical-mobile service. Study was collaboration of NASA, Federal Aviation Administration (FAA), Communications Satellite Corp. (COMSAT), and International Maritime Satellite System (INMARSAT).

  1. Mobile satellite service communications tests using a NASA satellite

    Science.gov (United States)

    Chambers, Katherine H.; Koschmeder, Louis A.; Hollansworth, James E.; ONeill, Jack; Jones, Robert E.; Gibbons, Richard C.

    1995-01-01

    Emerging applications of commercial mobile satellite communications include satellite delivery of compact disc (CD) quality radio to car drivers who can select their favorite programming as they drive any distance; transmission of current air traffic data to aircraft; and handheld communication of data and images from any remote corner of the world. Experiments with the enabling technologies and tests and demonstrations of these concepts are being conducted before the first satellite is launched by utilizing an existing NASA spacecraft.

  2. Antennas for mobile satellite communications

    Science.gov (United States)

    Huang, John

    1991-12-01

    A NASA sponsored program, called the Mobile Satellite (MSAT) system, has prompted the development of several innovative antennas at L-band frequencies. In the space segment of the MSAT system, an efficient, light weight, circularly polarized microstrip array that uses linearly polarized elements was developed as a multiple beam reflector feed system. In the ground segment, a low-cost, low-profile, and very efficient microstrip Yagi array was developed as a medium-gain mechanically steered vehicle antenna. Circularly shaped microstrip patches excited at higher-order modes were also developed as low-gain vehicle antennas. A more recent effort called for the development of a 20/30 GHz mobile terminal antenna for future-generation mobile satellite communications. To combat the high insertion loss encountered at 20/30 GHz, series-fed Monolithic Microwave Integrated Circuit (MMIC) microstrip array antennas are currently being developed. These MMIC arrays may lead to the development of several small but high-gain Ka-band antennas for the Personal Access Satellite Service planned for the 2000s.

  3. Integration of Commercial Mobile Satellite Services into Naval Communications

    National Research Council Canada - National Science Library

    Stone, Cary

    1997-01-01

    Mobile Satellite Services (MSS) need to be integrated into Naval Communications. DoD SATCOM military owned systems fall well short of meeting DoD SATCOM requirements in general and mobile SATCOM specifically...

  4. A Survey of Satellite Communications System Vulnerabilities

    National Research Council Canada - National Science Library

    Steinberger, Jessica A

    2008-01-01

    The U.S. military's increasing reliance on commercial and military communications satellites to enable widely-dispersed, mobile forces to communicate makes these space assets increasingly vulnerable to attack by adversaries...

  5. Satellite Communication and Long Distance Education

    OpenAIRE

    Hafied Cangara

    2016-01-01

    Since Indonesia introduced communication satellite for telecommunication network, the satellite has brought a number of advantages for national development in various areas, such as telephone network, mass media development, business, education, politics, security and national defence as well as regional and International cooperation. In education, satellite communication could be used for long-distance learning as implemented by 13 state universities in eastern parts of Indonesia. It is also...

  6. Estimating Rain Attenuation In Satellite Communication Links

    Science.gov (United States)

    Manning, R. M.

    1991-01-01

    Attenuation computed with help of statistical model and meteorological data. NASA Lewis Research Center Satellite Link Attenuation Model (SLAM) program QuickBASIC computer program evaluating static and dynamic statistical assessment of impact of rain attenuation on communication link established between Earth terminal and geosynchronous satellite. Application in specification, design, and assessment of satellite communication links for any terminal location in continental United States. Written in Microsoft QuickBASIC.

  7. Computer-Aided Communication Satellite System Analysis and Optimization.

    Science.gov (United States)

    Stagl, Thomas W.; And Others

    Various published computer programs for fixed/broadcast communication satellite system synthesis and optimization are discussed. The rationale for selecting General Dynamics/Convair's Satellite Telecommunication Analysis and Modeling Program (STAMP) in modified form to aid in the system costing and sensitivity analysis work in the Program on…

  8. High power communication satellites power systems study

    International Nuclear Information System (INIS)

    Josloff, A.T.; Peterson, J.R.

    1994-01-01

    This paper discusses a DOE-funded study to evaluate the commercial attractiveness of high power communication satellites and assesses the attributes of both conventional photovoltaic and reactor power systems. This study brings together a preeminent US Industry/Russian team to cooperate on the role of high power communication satellites in the rapidly expanding communications revolution. These high power satellites play a vital role in assuring availability of universally accessible, wide bandwidth communications, for high definition TV, super computer networks and other services. Satellites are ideally suited to provide the wide bandwidths and data rates required and are unique in the ability to provide services directly to the users. As new or relocated markets arise, satellites offer a flexibility that conventional distribution services cannot match, and it is no longer necessary to be near population centers to take advantage of the telecommunication revolution. The geopolitical implications of these substantially enhanced communications capabilities will be significant

  9. Economics of satellite communications systems

    Science.gov (United States)

    Pritchard, Wilbur L.

    This paper is partly a tutorial, telling systematically how one goes about calculating the total annual costs of a satellite communications system, and partly the expression of some original ideas on the choice of parameters so as to minimize these costs. The calculation of costs can be divided into two broad categories. The first is technical and is concerned with estimating what particular equipment will cost and what will be the annual expense to maintain and operate it. One starts in the estimation of any new system by listing the principal items of equipment, such as satellites, earth stations of various sizes and functions, telemetry and tracking equipment and terrestrial interfaces, and then estimating how much each item will cost. Methods are presented for generating such estimates, based on a knowledge of the gross parameters, such as antenna size, coverage area, transmitter power and information rate. These parameters determine the system performance and it is usually possible, knowing them, to estimate the costs of the equipment rather well. Some formulae based on regression analyses are presented. Methods are then given for estimating closely related expenses, such as maintenance and operation, and then an approximate method is developed for estimating terrestrial interconnection costs. It is pointed out that in specific cases when tariff and geographical information are available, it is usually better to work with specific data, but nonetheless it is often desirable, especially in global system estimating, to approximate these interconnect costs without recourse to individual tariffs. The procedure results in a set of costs for the purchase of equipment and its maintenance, and a schedule of payments. Some payments will be incurred during the manufacture of the satellite and before any systems operation, but many will not be incurred until the system is no longer in use, e.g. incentives. In any case, with the methods presented in the first section, one

  10. Space industrialization - Education. [via communication satellites

    Science.gov (United States)

    Joels, K. M.

    1978-01-01

    The components of an educational system based on, and perhaps enhanced by, space industrialization communications technology are considered. Satellite technology has introduced a synoptic distribution system for various transmittable educational media. The cost of communications satellite distribution for educational programming has been high. It has, therefore, been proposed to utilize Space Shuttle related technology and Large Space Structures (LSS) to construct a system with a quantum advancement in communication capability and a quantum reduction in user cost. LSS for communications purposes have three basic advantages for both developed and emerging nations, including the ability to distribute signals over wide geographic areas, the reduced cost of satellite communications systems versus installation of land based systems, and the ability of a communication satellite system to create instant educational networks.

  11. Activities of Canadian Satellite Communications, Inc.

    Science.gov (United States)

    1992-12-01

    Canadian Satellite Communications (Cancom) has as its core business the provision of television and radio signals to cable systems in Canada, with the objective of making affordable broadcast signals available to remote and/or small communities. Cancom also provides direct-to-home services to backyard receiving dishes, as well as satellite digital data business communications services, satellite business television, and satellite network services. Its business communication services range from satellite links for big-city businesses with small branch operations located far from major centers, to a mobile messaging and tracking system for the trucking industry. Revenues in 1992 totalled $48,212,000 and net income was just over $7 million. Cancom bought 10 percent interest in Leosat Corp. of Washington, DC, who are seeking approval to operate a position locator network from low-orbit satellites. Cancom has also become a partner in SovCan Star Satellite Communications Inc., which will build an international satellite system in partnership with Russia. The first satellite in this east-west business network will be placed in a Russian orbital slot over the Atlantic by 1996, and a second satellite will follow for the Pacific region. This annual report of Cancom's activities for 1992 includes financial statements and a six year financial review.

  12. Satellite communications network design and analysis

    CERN Document Server

    Jo, Kenneth Y

    2011-01-01

    This authoritative book provides a thorough understanding of the fundamental concepts of satellite communications (SATCOM) network design and performance assessments. You find discussions on a wide class of SATCOM networks using satellites as core components, as well as coverage key applications in the field. This in-depth resource presents a broad range of critical topics, from geosynchronous Earth orbiting (GEO) satellites and direct broadcast satellite systems, to low Earth orbiting (LEO) satellites, radio standards and protocols.This invaluable reference explains the many specific uses of

  13. Digital, Satellite-Based Aeronautical Communication

    Science.gov (United States)

    Davarian, F.

    1989-01-01

    Satellite system relays communication between aircraft and stations on ground. System offers better coverage with direct communication between air and ground, costs less and makes possible new communication services. Carries both voice and data. Because many data exchanged between aircraft and ground contain safety-related information, probability of bit errors essential.

  14. Reusable Communication Infrastructure for Small Satellites

    Data.gov (United States)

    National Aeronautics and Space Administration — The research goal of this project is to develop a comprehensive communications reference architecture that is applicable to a wide variety of small satellite...

  15. Satellite Communication and Development: A Reassessment.

    Science.gov (United States)

    Hudson, Heather E.

    The potential benefits of satellite communications development have been recognized since the notion of a geostationary "space platform" was proposed by Arthur C. Clarke in 1945. Although there have been examples of developmental applications of satellite technology, the promise has been slow in being fulfilled. The history of the…

  16. Protected transitional solution to transformational satellite communications

    Science.gov (United States)

    Brand, Jerry C.

    2005-06-01

    As the Warfighter progresses into the next generation battlefield, transformational communications become evident as an enabling technology. Satellite communications become even more vital as the battles range over greater non-contiguous spaces. While current satellite communications provide suitable beyond line-of-sight communications and the Transformational Communications Architecture (TCA) sets the stage for sound information exchange, a realizable transition must occur to ensure successful succession to this higher level. This paper addresses the need for a planned escalation to the next generation satellite communications architecture and offers near-term alternatives. Commercial satellite systems continue to enable the Warfighter to reach back to needed information resources, providing a large majority of available bandwidth. Four areas of concentration for transition include encrypted Telemetry, Tracking and Control (or Command) (TT&C), encrypted and covered data, satellite attack detection and protection, and operational mobility. Solution methodologies include directly embedding COMSEC devices in the satellites and terminals, and supplementing existing terminals with suitable equipment and software. Future satellites planned for near-term launches can be adapted to include commercial grade and higher-level secure equipment. Alternately, the expected use of programmable modems (Software Defined Radios (SDR)) enables incorporation of powerful cipher methods approaching military standards as well as waveforms suitable for on-the-move operation. Minimal equipment and software additions on the satellites can provide reasonable attack detection and protection methods in concert with the planned satellite usage. Network management suite modifications enable cohesive incorporation of these protection schemes. Such transitional ideas offer a smooth and planned transition as the TCA takes life.

  17. Satellite Communication and Long Distance Education

    Directory of Open Access Journals (Sweden)

    Hafied Cangara

    2016-02-01

    Full Text Available Since Indonesia introduced communication satellite for telecommunication network, the satellite has brought a number of advantages for national development in various areas, such as telephone network, mass media development, business, education, politics, security and national defence as well as regional and international cooperation. In education, satellite communication could be used for long-distance learning as implemented by 13 state universities in eastern parts of Indonesia. It is also possible to develop the Open University System in teaching and learning process, particularly since the internet technology has been intensively used

  18. Soviet satellite communications science and technology

    Energy Technology Data Exchange (ETDEWEB)

    Birch, J.N.; Campanella, S.J.; Gordon, G.D.; McElroy, D.R.; Pritchard, W.L.; Stamminger, R.

    1991-08-01

    This is a report by six US scientists and engineers concerning the current state of the art and projections of future Soviet satellite communications technologies. The panel members are experts in satellite stabilization, spacecraft environments, space power generation, launch systems, spacecraft communications sciences and technologies, onboard processing, ground stations, and other technologies that impact communications. The panel assessed the Soviet ability to support high-data-rate space missions at 128 Mbps by evaluating current and projected Soviet satellite communications technologies. A variety of space missions were considered, including Earth-to-Earth communications via satellites in geostationary or highly elliptical orbits, those missions that require space-to-Earth communications via a direct path and those missions that require space-to-Earth communications via a relay satellite. Soviet satellite communications capability, in most cases, is 10 years behind that of the United States and other industrialized nations. However, based upon an analysis of communications links needed to support these missions using current Soviet capabilities, it is well within the current Soviet technology to support certain space missions outlined above at rates of 128 Mbps or higher, although published literature clearly shows that the Soviet Union has not exceeded 60 Mbps in its current space system. These analyses are necessary but not sufficient to determine mission data rates, and other technologies such as onboard processing and storage could limit the mission data rate well below that which could actually be supported via the communications links. Presently, the Soviet Union appears to be content with data rates in the low-Earth-orbit relay via geostationary mode of 12 Mbps. This limit is a direct result of power amplifier limits, spacecraft antenna size, and the utilization of K{sub u}-band frequencies. 91 refs., 16 figs., 15 tabs.

  19. Gigabit Satellite Network for NASA's Advanced Communication Technology Satellite (ACTS)

    Science.gov (United States)

    Hoder, Douglas; Bergamo, Marcos

    1996-01-01

    The advanced communication technology satellite (ACTS) gigabit satellite network provides long-haul point-to-point and point-to-multipoint full-duplex SONET services over NASA's ACTS. at rates up to 622 Mbit/s (SONET OC-12), with signal quality comparable to that obtained with terrestrial fiber networks. Data multiplexing over the satellite is accomplished using time-division multiple access (TDMA) techniques coordinated with the switching and beam hopping facilities provided by ACTS. Transmissions through the satellite are protected with Reed-Solomon encoding. providing virtually error-free transmission under most weather conditions. Unique to the system are a TDMA frame structure and satellite synchronization mechanism that allow: (a) very efficient utilization of the satellite capacity: (b) over-the-satellite dosed-loop synchronization of the network in configurations with up to 64 ground stations: and (c) ground station initial acquisition without collisions with existing signalling or data traffic. The user interfaces are compatible with SONET standards, performing the function of conventional SONET multiplexers and. as such. can be: readily integrated with standard SONET fiber-based terrestrial networks. Management of the network is based upon the simple network management protocol (SNMP). and includes an over-the-satellite signalling network and backup terrestrial internet (IP-based) connectivity. A description of the ground stations is also included.

  20. High power communication satellites power systems study

    Science.gov (United States)

    Josloff, Allan T.; Peterson, Jerry R.

    1995-01-01

    This paper discusses a planned study to evaluate the commercial attractiveness of high power communication satellites and assesses the attributes of both conventional photovoltaic and reactor power systems. These high power satellites can play a vital role in assuring availability of universally accessible, wide bandwidth communications, for high definition TV, super computer networks and other services. Satellites are ideally suited to provide the wide bandwidths and data rates required and are unique in the ability to provide services directly to the users. As new or relocated markets arise, satellites offer a flexibility that conventional distribution services cannot match, and it is no longer necessary to be near population centers to take advantage of the telecommunication revolution. The geopolitical implications of these substantially enhanced communications capabilities can be significant.

  1. The Emerging Trends in Satellite and Wireless Communications ...

    Indian Academy of Sciences (India)

    Table of contents. The Emerging Trends in Satellite and Wireless Communications Technologies · Satellite Communications · Communications Satellites for Global Coverage · Satellite Transponders · The Four Generations Of Commercial Communication Geo-Sat · PowerPoint Presentation · An Indian Scenario INSAT ...

  2. Satellite communications - Intelsat and global patterns

    Science.gov (United States)

    Astrain, S.

    1983-10-01

    The global pattern of mankind's population growth is examined, taking into account the exponential increase in population which began only in the 17th century. As world population has grown, trade has increased, and transportation and communications have become vitally important. A revolution in global communications was initiated when Intelsat launched the first international communications satellite, 'Early Bird', in April 1965. Since April 1965, a tremendous development in global communications by means of satellites has taken place. The Intelsat VI satellite will have a capacity of 36,000 telephone circuits plus 2 TV channels, while the capacity of Early Bird was only 240 telephone circuits. Today, Intelsat is truly an international organization which includes 108 member countries. Attention is given to the particular importance of the Intelsat services to the developing countries, the exploration of new technologies and system concepts, and the extension of services to those portions of the global village which have remained electronically isolated.

  3. Deep space optical communication via relay satellite

    Science.gov (United States)

    Dolinar, S.; Vilnrotter, V.; Gagliardi, R.

    1981-01-01

    The application of optical communications for a deep space link via an earth-orbiting relay satellite is discussed. The system uses optical frequencies for the free-space channel and RF links for atmospheric transmission. The relay satellite is in geostationary orbit and contains the optics necessary for data processing and formatting. It returns the data to earth through the RF terrestrial link and also transmits an optical beacon to the satellite for spacecraft return pointing and for the alignment of the transmitting optics. Future work will turn to modulation and coding, pointing and tracking, and optical-RF interfacing.

  4. New Channel Coding Methods for Satellite Communication

    Directory of Open Access Journals (Sweden)

    J. Sebesta

    2010-04-01

    Full Text Available This paper deals with the new progressive channel coding methods for short message transmission via satellite transponder using predetermined length of frame. The key benefits of this contribution are modification and implementation of a new turbo code and utilization of unique features with applications of methods for bit error rate estimation and algorithm for output message reconstruction. The mentioned methods allow an error free communication with very low Eb/N0 ratio and they have been adopted for satellite communication, however they can be applied for other systems working with very low Eb/N0 ratio.

  5. Odyssey, an optimized personal communications satellite system

    Science.gov (United States)

    Rusch, Roger J.

    Personal communications places severe demands on service providers and transmission facilities. Customers are not satisfied with the current levels of service and want improvements. Among the characteristics that users seek are: lower service rates, hand held convenience, acceptable time delays, ubiquitous service, high availability, reliability, and high quality. The space industry is developing commercial space systems for providing mobile communications to personal telephones. Provision of land mobile satellite service is fundamentally different from the fixed satellite service provided by geostationary satellites. In fixed service, the earth based antennas can depend on a clear path from user to satellite. Mobile users in a terrestrial environment commonly encounter blockage due to vegetation, terrain or buildings. Consequently, high elevation angles are of premium value. TRW studied the issues and concluded that a Medium Earth Orbit constellation is the best solution for Personal Communications Satellite Service. TRW has developed Odyssey, which uses twelve satellites in medium altitude orbit to provide personal communications satellite service. The Odyssey communications system projects a multibeam antenna pattern to the Earth. The attitude control system orients the satellites to ensure constant coverage of land mass and coastal areas. Pointing can be reprogrammed by ground control to ensure optimized coverage of the desired service areas. The payload architecture features non-processing, "bent pipe" transponders and matrix amplifiers to ensure dynamic power delivery to high demand areas. Circuit capacity is 3000 circuits per satellite. Each satellite weighs 1917 kg (4226 pounds) at launch and the solar arrays provide 3126 Watts of power. Satellites are launched in pairs on Ariane, Atlas, or other vehicles. Each satellite is placed in a circular orbit at an altitude of 10,354 km. There are three orbit planes inclined at 55° to the equatorial plane

  6. The Advanced Communications Technology Satellite (ACTS) capabilities for serving science

    Science.gov (United States)

    Meyer, Thomas R.

    1990-01-01

    Results of research on potential science applications of the NASA Advanced Communications Technology Satellite (ACTS) are presented. Discussed here are: (1) general research on communications related issues; (2) a survey of science-related activities and programs in the local area; (3) interviews of selected scientists and associated telecommunications support personnel whose projects have communications requirements; (4) analysis of linkages between ACTS functionality and science user communications activities and modes of operation; and (5) an analysis of survey results and the projection of conclusions to a national scale.

  7. Development of Mission and Spacecraft Dynamics Analysis System for Geostationary Communication Satellite

    Directory of Open Access Journals (Sweden)

    Hyeon Cheol Gong

    1998-06-01

    Full Text Available We consider the motion of the subsystems as separate bodies as well as the entire satellite for the attitude and orbit control of a communication satellite by multi-body modeling technique. Thus, the system can be applied to a general communication satellite as well as a specific communication satellite, i.e. Koreasat I, II. The simulation results can be viewed by two-dimensional graphics and three-dimensional animation. The graphical user interface (GUI makes its usage much simpler. We have simulated a couple of scenarios for Koreasat I, II which are being operated as geostationary communication satellites to verify the system performance.

  8. Satellite communication from user to user

    Science.gov (United States)

    Gern, Manfred

    Satellite communication systems which allow a multitude of user-to-user, point-to-point, and multipoint connections, are presented. The bit rates are 64 kbit/sec and multiples, up to 1.92 Mbit/sec. If required, the ground-stations are installed at the customer's site or at suitable locations in order to serve several customers. However, technical requirements for station location have also to be fulfulled, in order to avoid interference with terrestrial radio services. The increasing number of participants to Satellite Multi Service and INTELSAT Business Services imposes the solution of the problem of communication using cheap techniques. The changes of the German Federal Post Office also permit the economic use of satellite radio techniques for short distances.

  9. Effect of Ionosphere on Geostationary Communication Satellite Signals

    Science.gov (United States)

    Erdem, Esra; Arikan, Feza; Gulgonul, Senol

    2016-07-01

    ionosphere using IRI-Plas-G software. One of the outstanding features of IONOLAB-RAY is the opportunity of Global Ionospheric Map-Total Electron Content (GIM-TEC) assimilation. This feature enables more realistic representation of ionosphere, especially for the times when ionosphere deviates from the generalized models, such as during geomagnetic storms. This feature is critical to examine the effect of ionosphere on satellite signals under ionospheric storm conditions. In this study TURKSAT satellite data is used to compare the results of IONOLAB-RAY and evaluate the effect of ionosphere. TURKSAT is one of the world's leading companies providing all sorts of satellite communications through the satellites of TURKSAT as well as the other satellites. Providing services for voice, data, internet, TV, and radio broadcasting through the satellites across a wide area extending from Europe to Asia. The latest satellite of TURKSAT, namely Turksat 4B was launched on October 2015, before that various versions of TURKSAT satellites are launched since 1994. In the future enlargement of broadcasting area towards equatorial region is aimed, where the ionospheric anomalies and storms are highly expected. In the future this study can be applied to the satellite signals in equatorial regions and effects of ionosphere especially under storm conditions can be discussed. This study is supported by TUBITAK 114E541, 115E915 and Joint TUBITAK 114E092 and AS CR 14/001 projects.

  10. Investigation of multipactor breakdown in communication satellite

    Indian Academy of Sciences (India)

    Multipactor breakdown or multipactor discharge is a form of high frequency discharge that may occur in microwave components operating at very low pressures. Some RF components of multi-channel communication satellites have co-axial geometry and handle high RF power under near-vacuum conditions.

  11. Inductive, Analogical, and Communicative Generalization

    Directory of Open Access Journals (Sweden)

    Adri Smaling

    2003-03-01

    Full Text Available Three forms of inductive generalization - statistical generalization, variation-based generalization and theory-carried generalization - are insufficient concerning case-to-case generalization, which is a form of analogical generalization. The quality of case-to-case generalization needs to be reinforced by setting up explicit analogical argumentation. To evaluate analogical argumentation six criteria are discussed. Good analogical reasoning is an indispensable support to forms of communicative generalization - receptive and responsive (participative generalization — as well as exemplary generalization.

  12. Ground test of satellite constellation based quantum communication

    OpenAIRE

    Liao, Sheng-Kai; Yong, Hai-Lin; Liu, Chang; Shentu, Guo-Liang; Li, Dong-Dong; Lin, Jin; Dai, Hui; Zhao, Shuang-Qiang; Li, Bo; Guan, Jian-Yu; Chen, Wei; Gong, Yun-Hong; Li, Yang; Lin, Ze-Hong; Pan, Ge-Sheng

    2016-01-01

    Satellite based quantum communication has been proven as a feasible way to achieve global scale quantum communication network. Very recently, a low-Earth-orbit (LEO) satellite has been launched for this purpose. However, with a single satellite, it takes an inefficient 3-day period to provide the worldwide connectivity. On the other hand, similar to how the Iridium system functions in classic communication, satellite constellation (SC) composed of many quantum satellites, could provide global...

  13. Potential markets for advanced satellite communications

    Science.gov (United States)

    Adamson, Steven; Roberts, David; Schubert, Leroy; Smith, Brian; Sogegian, Robert; Walters, Daniel

    1993-09-01

    This report identifies trends in the volume and type of traffic offered to the U.S. domestic communications infrastructure and extrapolates these trends through the year 2011. To describe how telecommunications service providers are adapting to the identified trends, this report assesses the status, plans, and capacity of the domestic communications infrastructure. Cable, satellite, and radio components of the infrastructure are examined separately. The report also assesses the following major applications making use of the infrastructure: (1) Broadband services, including Broadband Integrated Services Digital Network (BISDN), Switched Multimegabit Data Service (SMDS), and frame relay; (2) mobile services, including voice, location, and paging; (3) Very Small Aperture Terminals (VSAT), including mesh VSAT; and (4) Direct Broadcast Satellite (DBS) for audio and video. The report associates satellite implementation of specific applications with market segments appropriate to their features and capabilities. The volume and dollar value of these market segments are estimated. For the satellite applications able to address the needs of significant market segments, the report also examines the potential of each satellite-based application to capture business from alternative technologies.

  14. Potential markets for advanced satellite communications

    Science.gov (United States)

    Adamson, Steven; Roberts, David; Schubert, Leroy; Smith, Brian; Sogegian, Robert; Walters, Daniel

    1993-01-01

    This report identifies trends in the volume and type of traffic offered to the U.S. domestic communications infrastructure and extrapolates these trends through the year 2011. To describe how telecommunications service providers are adapting to the identified trends, this report assesses the status, plans, and capacity of the domestic communications infrastructure. Cable, satellite, and radio components of the infrastructure are examined separately. The report also assesses the following major applications making use of the infrastructure: (1) Broadband services, including Broadband Integrated Services Digital Network (BISDN), Switched Multimegabit Data Service (SMDS), and frame relay; (2) mobile services, including voice, location, and paging; (3) Very Small Aperture Terminals (VSAT), including mesh VSAT; and (4) Direct Broadcast Satellite (DBS) for audio and video. The report associates satellite implementation of specific applications with market segments appropriate to their features and capabilities. The volume and dollar value of these market segments are estimated. For the satellite applications able to address the needs of significant market segments, the report also examines the potential of each satellite-based application to capture business from alternative technologies.

  15. Satellite switched FDMA advanced communication technology satellite program

    Science.gov (United States)

    Atwood, S.; Higton, G. H.; Wood, K.; Kline, A.; Furiga, A.; Rausch, M.; Jan, Y.

    1982-01-01

    The satellite switched frequency division multiple access system provided a detailed system architecture that supports a point to point communication system for long haul voice, video and data traffic between small Earth terminals at Ka band frequencies at 30/20 GHz. A detailed system design is presented for the space segment, small terminal/trunking segment at network control segment for domestic traffic model A or B, each totaling 3.8 Gb/s of small terminal traffic and 6.2 Gb/s trunk traffic. The small terminal traffic (3.8 Gb/s) is emphasized, for the satellite router portion of the system design, which is a composite of thousands of Earth stations with digital traffic ranging from a single 32 Kb/s CVSD voice channel to thousands of channels containing voice, video and data with a data rate as high as 33 Mb/s. The system design concept presented, effectively optimizes a unique frequency and channelization plan for both traffic models A and B with minimum reorganization of the satellite payload transponder subsystem hardware design. The unique zoning concept allows multiple beam antennas while maximizing multiple carrier frequency reuse. Detailed hardware design estimates for an FDMA router (part of the satellite transponder subsystem) indicate a weight and dc power budget of 353 lbs, 195 watts for traffic model A and 498 lbs, 244 watts for traffic model B.

  16. Advanced domestic digital satellite communications systems experiments

    Science.gov (United States)

    Iso, A.; Izumisawa, T.; Ishida, N.

    1984-02-01

    The characteristics of advanced digital transmission systems were measured, using newly developed small earth stations and a K-band and C-band communication satellite. Satellite link performance for data, facsimile, video and packet switching information transmission at bit rates ranging from 6.4 kbit/s to 6.3 Mbit/s have been confirmed, using a small K-band earth station and a demand-assignment time division multiple access system. A low-capacity omni-use C-band terminal experiment has verified a telephone channel transmission performance by spread-spectrum multiple access. Single point to multipoint transmission characteristics of the 64 kbit/s data signals from the computer center were tested, using a receive-only 4 GHz earth terminal. Basic satellite link performance was confirmed under clear-sky conditions. Precise satellite orbit and attitude keeping experiments were carried out to obtain precise satellite antenna pointing accuracy for development of K-band earth stations that do not require satellite tracking equipment. Precise station keeping accuracy of 0.02 degrees was obtained.

  17. Cockpit weather graphics using mobile satellite communications

    Science.gov (United States)

    Seth, Shashi

    1993-01-01

    Many new companies are pushing state-of-the-art technology to bring a revolution in the cockpits of General Aviation (GA) aircraft. The vision, according to Dr. Bruce Holmes - the Assistant Director for Aeronautics at National Aeronautics and Space Administration's (NASA) Langley Research Center, is to provide such an advanced flight control system that the motor and cognitive skills you use to drive a car would be very similar to the ones you would use to fly an airplane. We at ViGYAN, Inc., are currently developing a system called the Pilot Weather Advisor (PWxA), which would be a part of such an advanced technology flight management system. The PWxA provides graphical depictions of weather information in the cockpit of aircraft in near real-time, through the use of broadcast satellite communications. The purpose of this system is to improve the safety and utility of GA aircraft operations. Considerable effort is being extended for research in the design of graphical weather systems, notably the works of Scanlon and Dash. The concept of providing pilots with graphical depictions of weather conditions, overlaid on geographical and navigational maps, is extremely powerful.

  18. Some design considerations for planetary relay communications satellites.

    Science.gov (United States)

    Barber, T. A.; Bourke, R. D.

    1966-01-01

    Items affecting information transmitted from payload landed on remote planet to Earth via communications satellite including orbit, transmission policy and orbit injection error effect on communication capability

  19. Application of adaptive antenna techniques to future commercial satellite communication

    Science.gov (United States)

    Ersoy, L.; Lee, E. A.; Matthews, E. W.

    1987-01-01

    The purpose of this contract was to identify the application of adaptive antenna technique in future operational commercial satellite communication systems and to quantify potential benefits. The contract consisted of two major subtasks. Task 1, Assessment of Future Commercial Satellite System Requirements, was generally referred to as the Adaptive section. Task 2 dealt with Pointing Error Compensation Study for a Multiple Scanning/Fixed Spot Beam Reflector Antenna System and was referred to as the reconfigurable system. Each of these tasks was further sub-divided into smaller subtasks. It should also be noted that the reconfigurable system is usually defined as an open-loop system while the adaptive system is a closed-loop system. The differences between the open- and closed-loop systems were defined. Both the adaptive and reconfigurable systems were explained and the potential applications of such systems were presented in the context of commercial communication satellite systems.

  20. Modular approach for satellite communication ground terminals

    Science.gov (United States)

    Gould, G. R.

    1984-01-01

    The trend in satellite communications is toward completely digital, time division multiple access (TDMA) systems with uplink and downlink data rates dictated by the type of service offered. Trunking terminals will operate in the 550 MBPS (megabit per second) region uplink and downlink, whereas customer premise service (CPS) terminals will operate in the 25 to 10 MBPS region uplink and in the 200 MBPS region downlink. Additional criteria for the ground terminals will be to maintain clock sychronization with the system and burst time integrity to within a matter of nanoseconds, to process required order-fire information, to provide adaptive data scrambing, and to compensate for variations in the user input output data rates, and for changes in range in the satellite communications links resulting from satellite perturbations in orbit. To achieve the required adaptability of a ground terminal to the above mentioned variables, programmable building blocks can be developed that will meet all of these requirements. To maintain system synchronization, i.e., all bursted data arriving at the satellite within assigned TDMA windows, ground terminal transmit data rates and burst timing must be maintained within tight tolerances. With a programmable synchronizer as the heart of the terminal timing generation, variable data rates and burst timing tolerances are achievable. In essence, the unit inputs microprocessor generated timing words and outputs discrete timing pulses.

  1. Intersatellite link application to commercial communications satellites

    Science.gov (United States)

    Lee, Young S.; Atia, Ali E.; Ponchak, Denise S.

    1988-01-01

    The fundamental characteristics of intersatellite link (ISL) systems, and their application to domestic, regional, and global satellite communications, are described. The quantitative advantages of using ISLs to improve orbit utilization, spectrum occupancy, transmission delay (compared to multi-hop links), coverage, and connectivity, and to reduce the number of earth station antennas, are also presented. Cost-effectiveness and other systems benefits of using ISLs are identified, and the technical and systems planning aspects of ISL systems implementation are addressed.

  2. Servicing communication satellites in geostationary orbit

    Science.gov (United States)

    Russell, Paul K.; Price, Kent M.

    1990-01-01

    The econmic benefits of a LEO space station are quantified by identifying alternative operating scenarios utilizing the space station's transportation facilities and assembly and repair facilities. Particular consideration is given to the analysis of the impact of on-orbit assembly and servicing on a typical communications satellite is analyzed. The results of this study show that on-orbit servicing can increase the internal rate of return by as much as 30 percent.

  3. Vibration noise control in laser satellite communication

    Science.gov (United States)

    Saksonov, Avigdor; Shlomi, Arnon; Kopeika, Norman S.

    2001-08-01

    Laser satellite communication has become especially attractive in recent years. Because the laser beam width is narrow than in the RF or microwave range, the transmitted optical power may be significantly reduced. This leads to development of miniature communication systems with extremely low power consumption. On the other hand, the laser communication channel is very sensitive to vibrations of the optical platform. These vibrations cause angular noise in laser beam pointing, comparable to the laser beam width. As result, as significant portion of the optical power between transmitter and receiver is lost and the bit error rate is increased. Consequently, vibration noise control is a critical problem in laser satellite communication. The direction of the laser beam is corrected with a fast steering mirror (FSM). In this paper are presented two approaches for the FSM control. One is the feedback control that uses an LQG algorithm. The second is the direct feed- forward control when vibration noise is measured by three orthogonal accelerometers and drives directly the F SM. The performances of each approach are evaluated using MATLAB simulations.

  4. A New Era Begins: Satellite Communications and Development.

    Science.gov (United States)

    Pelton, Joseph N.

    This overview of changes in the field of telecommunications development produced by satellite communications over the last 15 years focuses on applications of satellite systems for educational and health purposes in developing countries. Satellite communications development from 1974 to 1986 is identified as the first stage of telecommunications…

  5. A new antenna concept for satellite communications

    Science.gov (United States)

    Skahill, G.; Ciccolella, D.

    1982-01-01

    A novel antenna configuration of two reflecting surfaces and a phased array is examined for application to satellite communications and shown to be superior in every respect to earlier designs for service to the continental United States from synchronous orbit. The vignetting that afflicts other two reflector optical systems is eliminated by use of a reflecting field element. The remaining aberrations, predominantly coma, are isolated in the time delay distribution at the surface of the array and can be compensated by ordinary array techniques. The optics exhibits infinite bandwidth and the frequency range is limited only by the design of the array.

  6. A general theory for the Uranian satellites

    Science.gov (United States)

    Laskar, J.

    1986-01-01

    A general analytical theory of the five main satellites of Uranus, including the secular and short period terms hereafter denoted by GUST, is presented. A comparison is made with an internal numerical integration with nominal masses of Veillet (1983). The precision of the theory goes from about 10 km for Miranda to 100 km for Oberon. The short period terms in the motions of Titania and Oberon are larger than 500 km. They should make possible the determination of the masses of the outer satellites through the optical data of Voyager encounter.

  7. Apple - Indian experimental geostationary communication satellite

    Science.gov (United States)

    Rao, U. R.; Vasagam, R. M.

    Developmental steps, responsibilities, design goals, performance characteristics, and support systems for the ISRO Ariane Passenger Payload Experiment (APPLE) experimental GEO communication satellite are described. The spacecraft underwent structural, thermal, engineering, prototype, and flight qualification tests in India before being shipped to Guyana for launch on the third Ariane test flight. APPLE carries a redundant C-band communication transponder fed by a 900 mm diam parabolic reflector. A 6 GHz uplink and 4 GHz downlink are processed through a diplexer, with the receiver employing a low noise GaAs FET amplifier. In-orbit telemetry is provided by a 4095 MHz beacon with a data rate of 64 bits/sec. Two solar panels supply 210 W of power, while an on-board Ni-Cd storage battery stores 240 Wh for the ascent and during eclipse. Teleconferencing has been successfully performed using the spacecraft link.

  8. Implementation of Multiple Access Techniques Applicable for Maritime Satellite Communications

    OpenAIRE

    Stojce Dimov Ilcev

    2013-01-01

    In this paper are introduced fundamentals, characteristics, advantages and disadvantages of Multiple Access (MA) employed as transmission techniques in the Maritime Mobile Satellite Communications (MMSC) between ships and Coast Earth Station (CES) via Geostationary Earth Orbit (GEO) or Not-GEO satellite constellations. In fixed satellite communication, as a rule, especially in MMSC many users are active at the same time. The problem of simultaneous communications between many single or multip...

  9. The Future of Satellite Communications Technology.

    Science.gov (United States)

    Nowland, Wayne

    1985-01-01

    Discusses technical advances in satellite technology since the 1960s, and the International Telecommunications Satellite Organization's role in these developments; describes how AUSSAT, Australia's domestic satellite system, exemplifies the latest developments in satellite technology; and reviews satellite system features, possible future…

  10. Mass and power modeling of communication satellites

    Science.gov (United States)

    Price, Kent M.; Pidgeon, David; Tsao, Alex

    1991-01-01

    Analytic estimating relationships for the mass and power requirements for major satellite subsystems are described. The model for each subsystem is keyed to the performance drivers and system requirements that influence their selection and use. Guidelines are also given for choosing among alternative technologies which accounts for other significant variables such as cost, risk, schedule, operations, heritage, and life requirements. These models are intended for application to first order systems analyses, where resources do not warrant detailed development of a communications system scenario. Given this ground rule, the models are simplified to 'smoothed' representation of reality. Therefore, the user is cautioned that cost, schedule, and risk may be significantly impacted where interpolations are sufficiently different from existing hardware as to warrant development of new devices.

  11. SAW based systems for mobile communications satellites

    Science.gov (United States)

    Peach, R. C.; Miller, N.; Lee, M.

    1993-01-01

    Modern mobile communications satellites, such as INMARSAT 3, EMS, and ARTEMIS, use advanced onboard processing to make efficient use of the available L-band spectrum. In all of these cases, high performance surface acoustic wave (SAW) devices are used. SAW filters can provide high selectivity (100-200 kHz transition widths), combined with flat amplitude and linear phase characteristics; their simple construction and radiation hardness also makes them especially suitable for space applications. An overview of the architectures used in the above systems, describing the technologies employed, and the use of bandwidth switchable SAW filtering (BSSF) is given. The tradeoffs to be considered when specifying a SAW based system are analyzed, using both theoretical and experimental data. Empirical rules for estimating SAW filter performance are given. Achievable performance is illustrated using data from the INMARSAT 3 engineering model (EM) processors.

  12. The Advanced Communication Technology Satellite and ISDN

    Science.gov (United States)

    Lowry, Peter A.

    1996-01-01

    This paper depicts the Advanced Communication Technology Satellite (ACTS) system as a global central office switch. The ground portion of the system is the collection of earth stations or T1-VSAT's (T1 very small aperture terminals). The control software for the T1-VSAT's resides in a single CPU. The software consists of two modules, the modem manager and the call manager. The modem manager (MM) controls the RF modem portion of the T1-VSAT. It processes the orderwires from the satellite or from signaling generated by the call manager (CM). The CM controls the Recom Laboratories MSPs by receiving signaling messages from the stacked MSP shelves ro units and sending appropriate setup commands to them. There are two methods used to setup and process calls in the CM; first by dialing up a circuit using a standard telephone handset or, secondly by using an external processor connected to the CPU's second COM port, by sending and receiving signaling orderwires. It is the use of the external processor which permits the ISDN (Integrated Services Digital Network) Signaling Processor to implement ISDN calls. In August 1993, the initial testing of the ISDN Signaling Processor was carried out at ACTS System Test at Lockheed Marietta, Princeton, NJ using the spacecraft in its test configuration on the ground.

  13. Technical comparison of several global mobile satellite communications systems

    Science.gov (United States)

    Comparetto, Gary M.

    The era of satellite-based mobile satellite communications (MSC) systems started with the first MARISAT satellite which was launched into a geostationary orbit over the Pacific Ocean in 1976 to provide communications between ships and shore stations. The combination of high cost and unacceptably large equipment has kept the space-based MSC systems from appealing to the wider market of personal mobile communications. The progress made over the last ten years, however, in digital voice processing, satellite technology, and component miniaturization has resulted in the viability of satellite-based mobile satellite communications systems to meet the growing market in personal mobile communications using handsets similar to those currently in use with land-based cellular systems. Three of the more mature LEO/MEO satellite systems are addressed in this paper including GLOBALSTAR, Iridium, and Odyssey. The system architectures of each system are presented along with a description of the satellite and user handset designs and the multiaccess techniques employed. It will be shown that, although a number of similarities exist among the system addressed, each system is unique in a variety of significant design areas. It is concluded that the technical feasibility of satellite-based mobile satellite communications systems seems to be secure. It will be challenging, however, for the vendors to actually develop and deploy these systems in a cost effective, timely, and reliable way that meets a continually evolving set of requirements based upon a rapidly changing technology base.

  14. Nutrition communication in general practice

    NARCIS (Netherlands)

    Dillen, van S.M.E.; Hiddink, G.J.; Koelen, M.A.; Graaf, de C.; Woerkum, van C.M.J.

    2006-01-01

    General practitioners (GPs) are frequently confronted with patients who suffer from obesity or other nutrition-related diseases, such as diabetes and coronary heart disease. There is increasing evidence that nutrition communication is effective in changing nutrition behaviour. Moreover, it is widely

  15. Communication Satellite: Nigeria's Efforts at Bridging Digital Divide ...

    African Journals Online (AJOL)

    Communication Satellite in the wireless age has the potentials of bridging the digital gulf that exists between civilized and developing nation. If well used, communication Satellite is a potent infrastructure of addressing technology convergence for holistic national development. This paper examines Nigeria's technological ...

  16. Personal communications via ACTS satellite HBR transponders

    Science.gov (United States)

    Fang, Russell J. F.

    1991-01-01

    The concept of a fully meshed network of briefcase-sized terminals is presented for personal communications over Ka-band satellite transponders. In this concept, undesirable double-hop delays are avoided for voice communications. The bandwidth and power resources of the transponder are efficiently shared by users in a simple demand-assigned manner via code-division multiple access (CDMA). Voice, data, and facsimile are statistically multiplexed at each terminal. In order to minimize terminal costs, frequency-precorrected, and level-preadjusted continuous-wave tones are sent from the central network control station in each beam so that the terminals in each down-link beam can use these pilots as references for antenna acquisition and tracking, as reliable frequency sources, and as indicators of signal fade for up-link power control (ULPC). The potential CDMA 'near-far' problem due to up-link fades is mitigated by using ULPC. Quasi-burst mode transmission is employed to minimize the potential clock and pseudorandom number code synchronization.

  17. Advanced mobile satellite communications using COMETS satellite in MM-wave and Ka-band

    Science.gov (United States)

    Ohmori, Shingo; Isobe, Shunkichi; Takeuchi, Makoto; Naito, Hideyuki

    1993-01-01

    Early in the 21st century, the demand for personal communications using mobile, hand-held, and VSAT terminals will rapidly increase. In a future system, many different types of services should be provided with one-hop connection. The Communications Research Laboratory (CRL) has studied a future advanced mobile satellite communications system using millimeter wave and Ka band. In 1990, CRL started the Communications and Broadcasting Engineering Test Satellite (COMETS) project. The satellite has been developed in conjunction with NASDA and will be launched in 1997. This paper describes the COMETS payload configuration and the experimental system for the advanced mobile communications mission.

  18. A demand assignment control in international business satellite communications network

    Science.gov (United States)

    Nohara, Mitsuo; Takeuchi, Yoshio; Takahata, Fumio; Hirata, Yasuo

    An experimental system is being developed for use in an international business satellite (IBS) communications network based on demand-assignment (DA) and TDMA techniques. This paper discusses its system design, in particular from the viewpoints of a network configuration, a DA control, and a satellite channel-assignment algorithm. A satellite channel configuration is also presented along with a tradeoff study on transmission rate, HPA output power, satellite resource efficiency, service quality, and so on.

  19. Research of the key technology in satellite communication networks

    Science.gov (United States)

    Zeng, Yuan

    2018-02-01

    According to the prediction, in the next 10 years the wireless data traffic will be increased by 500-1000 times. Not only the wireless data traffic will be increased exponentially, and the demand for diversified traffic will be increased. Higher requirements for future mobile wireless communication system had brought huge market space for satellite communication system. At the same time, the space information networks had been greatly developed with the depth of human exploration of space activities, the development of space application, the expansion of military and civilian application. The core of spatial information networks is the satellite communication. The dissertation presented the communication system architecture, the communication protocol, the routing strategy, switch scheduling algorithm and the handoff strategy based on the satellite communication system. We built the simulation platform of the LEO satellites networks and simulated the key technology using OPNET.

  20. A digital simulation of message traffic for natural disaster warning communications satellite

    Science.gov (United States)

    Hein, G. F.; Stevenson, S. M.

    1972-01-01

    Various types of weather communications are required to alert industries and the general public about the impending occurrence of tornados, hurricanes, snowstorms, floods, etc. A natural disaster warning satellite system has been proposed for meeting the communications requirements of the National Oceanic and Atmospheric Administration. Message traffic for a communications satellite was simulated with a digital computer in order to determine the number of communications channels to meet system requirements. Poisson inputs are used for arrivals and an exponential distribution is used for service.

  1. A Hybrid Satellite-Terrestrial Approach to Aeronautical Communication Networks

    Science.gov (United States)

    Kerczewski, Robert J.; Chomos, Gerald J.; Griner, James H.; Mainger, Steven W.; Martzaklis, Konstantinos S.; Kachmar, Brian A.

    2000-01-01

    Rapid growth in air travel has been projected to continue for the foreseeable future. To maintain a safe and efficient national and global aviation system, significant advances in communications systems supporting aviation are required. Satellites will increasingly play a critical role in the aeronautical communications network. At the same time, current ground-based communications links, primarily very high frequency (VHF), will continue to be employed due to cost advantages and legacy issues. Hence a hybrid satellite-terrestrial network, or group of networks, will emerge. The increased complexity of future aeronautical communications networks dictates that system-level modeling be employed to obtain an optimal system fulfilling a majority of user needs. The NASA Glenn Research Center is investigating the current and potential future state of aeronautical communications, and is developing a simulation and modeling program to research future communications architectures for national and global aeronautical needs. This paper describes the primary requirements, the current infrastructure, and emerging trends of aeronautical communications, including a growing role for satellite communications. The need for a hybrid communications system architecture approach including both satellite and ground-based communications links is explained. Future aeronautical communication network topologies and key issues in simulation and modeling of future aeronautical communications systems are described.

  2. Live Satellite Communications... An Exciting Teaching Aid

    Science.gov (United States)

    Journal of Aerospace Education, 1976

    1976-01-01

    Describes ways that orbiting satellites carrying amateur radios can be used in the classroom at various grade levels to supplement physics, mathematics, electronics, and social science curricula. (MLH)

  3. Communication satellites to enter a new age of flexibility

    Science.gov (United States)

    Balty, Cédric; Gayrard, Jean-Didier; Agnieray, Patrick

    2009-07-01

    To cope with the economical and technical evolutions of the communication market and to better compete with or complement terrestrial networks, satellite operators are requiring more flexible satellites. It allows a better fleet planning potential and back-up policy, a more standardized and efficient procurement process, mission adaptation to market evolution and the possibility of early entry in new markets. New technologies that are developed either for terrestrial networks or for space defense applications would become soon available to satellite and equipment manufacturers. A skilful mix of these new technologies with the older and more mature ones should boost satellite performances and bring flexibility to the new generation of communication satellites. This paper reviews the economical and technical environment of the space communication business for the next decade. It identifies the needs and levels of flexibility that are required by the market but also allowed by technologies, in both a top-down and bottom-up approach.

  4. Integration of Satellite and Terrestrial Systems in Future Multimedia Communications

    OpenAIRE

    Evans, Barry; Werner, Markus; Lutz, Erich; Bousquet, Michel; Corazza, Giovanni E; Maral, Gerard; Rumeau, Robert; Ferro, Erina

    2005-01-01

    In this article we examine the role of satellite communications in future telecommunication networks and service provision. Lessons from the past indicate that satellites are successful as a result of their wide area coverage or speed to market for new services. Niche areas such as coverage of air and sea will persist, but for land masses convergence of fixed, mobile, and broadcasting will dictate that the only way forward for satellites is in an integrated format with terrestrial systems. We...

  5. LEOPACK The integrated services communications system based on LEO satellites

    Science.gov (United States)

    Negoda, A.; Bunin, S.; Bushuev, E.; Dranovsky, V.

    LEOPACK is yet another LEO satellite project which provides global integrated services for 'business' communications. It utilizes packet rather then circuit switching in both terrestrial and satellite chains as well as cellular approach for frequencies use. Original multiple access protocols and decentralized network control make it possible to organize regionally or logically independent and world-wide networks. Relatively small number of satellites (28) provides virtually global network coverage.

  6. An Analysis of Military Use of Commercial Satellite Communications

    National Research Council Canada - National Science Library

    Forest, Benjamin D

    2008-01-01

    Since the Gulf War of 1991, United States military satellite communication (SATCOM) bandwidth demand has increased dramatically, as evidenced by recent usage rates in Operation Enduring Freedom and Operation Iraqi Freedom...

  7. Military Dependence on Commercial Satellite Communications Systems - Strength or Vulnerability

    National Research Council Canada - National Science Library

    Hook, Jack

    1999-01-01

    The military's growing dependence on commercial satellite communications systems will become a strength or vulnerability based on how well the right balance is achieved between commercial and military systems...

  8. Estimating Effects Of Rain On Ground/Satellite Communication

    Science.gov (United States)

    Manning, R. M.

    1992-01-01

    LeRC-SLAM provides static and dynamic statistical assessment of impact of attenuation by rain on communication link established between Earth terminal and geosynchronous satellite. Program designed for use in specification, design, and assessment of satellite link for any terminal location in continental United States. IBM PC version written in Microsoft QuickBASIC, and Macintosh version written in Microsoft Basic.

  9. Mobile satellite communications in the 1990's

    Science.gov (United States)

    Singh, Jai

    1992-07-01

    The evolution of Inmarsat global services from a single market and single service of the 1980's to all of the key mobile markets and a wide range of new terminals and services in the 1990's is described. An overview of existing mobile satellite services, as well as new services under implementation for introduction in the near and longer term, including a handheld satellite phone (Inmarsat-P), is provided. The initiative taken by Inmarsat in the integration of its global mobile satellite services with global navigation capability derived from GPS (Global Positioning System) and the GLONASS (Russian GPS) navigation satellite systems and the provision of an international civil overlay for GPS/GLONASS integrity and augmentation is highlighted. To complete the overview of the development of mobile satellite services in the 1990's, the known national and regional mobile satellite system plans and the various recent proposals for both orbiting and geostationary satellite systems for proving handheld satellite phone and/or data messaging services are described.

  10. Use of Advanced Solar Cells for Commercial Communication Satellites

    Science.gov (United States)

    Bailey, Sheila G.; Landis, Geoffrey A.

    1995-01-01

    The current generation of communications satellites are located primarily in geosynchronous Earth orbit (GEO). Over the next decade, however, a new generation of communications satellites will be built and launched, designed to provide a world-wide interconnection of portable telephones. For this mission, the satellites must be positioned in lower polar and near-polar orbits. To provide complete coverage, large numbers of satellites will be required. Because the required number of satellites decreases as the orbital altitude is increased, fewer satellites would be required if the orbit chosen were raised from low to intermediate orbit. However, in intermediate orbits, satellites encounter significant radiation due to trapped electrons and protons. Radiation tolerant solar cells may be necessary to make such satellites feasible. We analyze the amount of radiation encountered in low and intermediate polar orbits at altitudes of interest to next-generation communication satellites, calculate the expected degradation for silicon, GaAs, and InP solar cells, and show that the lifetimes can be significantly increased by use of advanced solar cells.

  11. Anti-jamming Technology in Small Satellite Communication

    Science.gov (United States)

    Jia, Zixiang

    2018-01-01

    Small satellite communication has an increasingly important position among the wireless communications due to the advantages of low cost and high technology. However, in view of the case that its relay station stays outside the earth, its uplink may face interference from malicious signal frequently. Here this paper classified enumerates existing interferences, and proposes channel signals as main interference by comparison. Based on a basic digital communication process, then this paper discusses the possible anti - jamming techniques that commonly be realized at all stages in diverse processes, and comes to the conclusion that regarding the spread spectrum technology and antenna anti-jamming technology as fundamental direction of future development. This work provides possible thought for the design of new small satellite communication system with the coexistence of multi - technologies. This basic popular science can be consulted for people interested in small satellite communication.

  12. Uses of communication satellites in water utility operations

    Science.gov (United States)

    Tighe, W. S.

    This paper proposes a system to serve the communications needs of the operating side of a water utility and estimates the requirements and capabilities of the equipment needed. The system requires the shared use of a satellite transponder with 100% backup. Messages consist of data packets containing data and control information, plus voice transmission. Satellite communication may have a price advantage in some instances over wire line or VHF radio and have greater survivability in case of a natural disaster. Water and other utilities represent a significant market for low cost mass produced satellite earth terminals.

  13. Advanced Communications Technology Satellite (ACTS): Four-Year System Performance

    Science.gov (United States)

    Acosta, Roberto J.; Bauer, Robert; Krawczyk, Richard J.; Reinhart, Richard C.; Zernic, Michael J.; Gargione, Frank

    1999-01-01

    The Advanced Communications Technology Satellite (ACTS) was conceived at the National Aeronautics and Space Administration (NASA) in the late 1970's as a follow-on program to ATS and CTS to continue NASA's long history of satellite communications projects. The ACTS project set the stage for the C-band satellites that started the industry, and later the ACTS project established the use of Ku-band for video distribution and direct-to-home broadcasting. ACTS, launched in September 1993 from the space shuttle, created a revolution in satellite system architecture by using digital communications techniques employing key technologies such as a fast hopping multibeam antenna, an on-board baseband processor, a wide-band microwave switch matrix, adaptive rain fade compensation, and the use of 900 MHz transponders operating at Ka-band frequencies. This paper describes the lessons learned in each of the key ACTS technology areas, as well as in the propagation investigations.

  14. COMMUNICATION SATELLITES FOR EDUCATION, SCIENCE AND CULTURE. REPORTS AND PAPERS ON MASS COMMUNICATION, NO. 53.

    Science.gov (United States)

    SCHRAMM, WILBUR

    THE TECHNOLOGY OF COMMUNICATION SATELLITES IS SUFFICIENTLY ADVANCED THAT CONCERNED AGENCIES, SUCH AS UNESCO, SHOULD BEGIN TO PLAN FOR THEIR USE IN EXCHANGE OF DATA, NEWS TRANSMISSION, CULTURAL EXCHANGE, AND EDUCATION. GROUNDWORK IN TECHNOLOGY, IN THE DESIGN OF A SATELLITE COMMUNICATION SYSTEM, IN VALUE JUDGMENTS, IN AGREEMENTS OF COOPERATION AND…

  15. Recent Korean R&D in Satellite Communications

    Science.gov (United States)

    Lee, Ho-Jin; Kim, Jae Moung; Lee, Byung-Seub; Lee, Han; Ryoo, Jang-Soo

    The R&D in satellite communications in Korea has been driven mainly by KCC (Korea Communications Commission) but in a small scale compared to Korea space development program organized by MEST (Ministry of Education, Science and Technology). Public and civilian satcom sector R&D has been led mainly by ETRI with small/medium companies contrary to rare investment in private sector while military sector R&D has been orchestrated by ADD with defense industry. By the COMS (Communication, Ocean and Meteorological Satellite) experimental Ka-band payload, Korea pursues a space qualification of own technology for national infrastructure evolution as well as industrialization of space R&D results. Once COMS launched and space qualified in 2009, subsequent application experiments and new technology R&D like UHDTV will entail service and industry promotion. The payload technology is expected for the next Korean commercial satellites or for new OBP satellites. The COMS ground control system and GNSS ground station technologies are under development for COMS operation and enhanced GNSS services along with advent of Galileo respectively. Satellite broadband mobile VSAT based on DVB-S2/RCS (+M) and low profile tracking antennas have been developed for trains, ships, and planes. While APSI is developing GMR-1 based Thuraya handset functions, ETRI is designing IMT-Advanced satellite radio interface for satellite and terrestrial dual-mode handheld communication system like Japanese STICS, with universities' satellite OFDM researches. A 21GHz Ka-band higher-availability scalable HD broadcasting technology and SkyLife's hybrid satellite IPTV technology are being developed. In near term Korea will extend R&D programs to upgrade the space communication infrastructure for universal access to digital opportunity and safer daily life from disaster, and to promote space green IT industrialization, national security, and space resources sovereign. Japanese stakeholders are invited to establish

  16. Satellite communications for the next generation telecommunication services and networks

    Science.gov (United States)

    Chitre, D. M.

    1991-01-01

    Satellite communications can play an important role in provisioning the next-generation telecommunication services and networks, provided the protocols specifying these services and networks are satellite-compatible and the satellite subnetworks, consisting of earth stations interconnected by the processor and the switch on board the satellite, interwork effectively with the terrestrial networks. The specific parameters and procedures of frame relay and broadband integrated services digital network (B-ISDN) protocols which are impacted by a satellite delay. Congestion and resource management functions for frame relay and B-ISDN are discussed in detail, describing the division of these functions between earth stations and on board the satellite. Specific onboard and ground functions are identified as potential candidates for their implementation via neural network technology.

  17. Multiquantum well beam-steering device for laser satellite communication

    Science.gov (United States)

    Lahat, Roee; Levy, Itamar; Shlomi, Arnon

    2002-01-01

    With the increasing interest in laser satellite communications, new methods are sought to solve the existing problems of accurate and rapid laser beam deflection. Current solutions in the form of galvanometers or piezo fast steering mirrors with one or two degrees of freedom are bulky, power-consuming and slow. The Multi-Quantum Well (MQW) is a semiconductor device with unique potential to steer laser beams without any moving parts. We have conducted a preliminary evaluation of the potential application of the MQW as a laser beam-steering device for laser satellite communication, examining the performance of critical parameters for this type of communications.

  18. Satellite communication transponders and their reliability; Eisei tosai tsushin kiki oyobi shinraisei ni tsuite

    Energy Technology Data Exchange (ETDEWEB)

    Ogawa, H [NTT Wireless System Laboratories, Kanagawa (Japan)

    1994-11-01

    The Engineering Test Satellite-VI is a large composite test satellite weighing two tons to perform different communication experiments. Adoption of the multi-beam satellite communication system has made possible to increase the transmission capacity, reduce the sizes of earth stations, and utilize frequencies more effectively. This paper describes the configuration of the relaying devices mounted thereon, the newly developed circuit technologies, and their reliability. The multi-beam satellite communication system mounts a number of transponders, with the frequency bands used divided into the 2.6/2.5 GHz band between the moving body and the satellite, the 6/4 GHz band for the channels between the earth stations and the satellite, and the 30/20 GHz band for the fixed communications. These arrangements were intended to achieve large size reduction as a result of applying the integrated circuit technology. The transmitters and the receivers corresponding to each beam are connected by using the satellite switches (16 inputs {times} 12 outputs). The parts used were general purpose ones rather than those specified in the MIL standards because of their number having reached so huge. Their reliability was ensured by long-term burn-in operations. 5 refs., 6 figs., 1 tab.

  19. Taking the Politics Out of Satellite and Space-Based Communications Protocols

    Science.gov (United States)

    Ivancic, William D.

    2006-01-01

    After many years of studies, experimentation, and deployment, large amounts of misinformation and misconceptions remain regarding applicability of various communications protocols for use in satellite and space-based networks. This paper attempts to remove much of the politics, misconceptions, and misinformation that have plagued spacebased communications protocol development and deployment. This paper provides a common vocabulary for communications; a general discussion of the requirements for various communication environments; an evaluation of tradeoffs between circuit and packet-switching technologies, and the pros and cons of various link, network, transport, application, and security protocols. Included is the applicability of protocol enhancing proxies to NASA, Department of Defense (DOD), and commercial space communication systems.

  20. Advances in MMIC technology for communications satellites

    Science.gov (United States)

    Leonard, Regis F.

    1992-01-01

    This paper discusses NASA Lewis Research Center's program for development of monolithic microwave integrated circuits (MMIC) for application in space communications. Emphasis will be on the improved performance in power amplifiers and low noise receivers which has been made possible by the development of new semiconductor materials and devices. Possible applications of high temperature superconductivity for space communications will also be presented.

  1. Spread spectrum mobile communication experiment using ETS-V satellite

    Science.gov (United States)

    Ikegami, Tetsushi; Suzuki, Ryutaro; Kadowaki, Naoto; Taira, Shinichi; Sato, Nobuyasu

    1990-01-01

    The spread spectrum technique is attractive for application to mobile satellite communications, because of its random access capability, immunity to inter-system interference, and robustness to overloading. A novel direct sequence spread spectrum communication equipment is developed for land mobile satellite applications. The equipment is developed based on a matched filter technique to improve the initial acquisition performance. The data rate is 2.4 kilobits per sec. and the PN clock rate is 2.4552 mega-Hz. This equipment also has a function of measuring the multipath delay profile of land mobile satellite channel, making use of a correlation property of a PN code. This paper gives an outline of the equipment and the field test results with ETS-V satellite.

  2. Advanced Communications Technology Satellite (ACTS) and potential system applications

    Science.gov (United States)

    Wright, David L.; Balombin, Joseph R.; Sohn, Philip Y.

    1990-01-01

    A description of the advanced communications technology satellite (ACTS) system is given with special emphasis on the communication characteristics. Potential satellite communications scenarios, including future operational ACTS-like satellite systems, are discussed. The description of the ACTS system updates previously published ACTS system references. Detailed information on items such as experimental ground stations is presented. The potential services can be generically described as voice, video, and data services. The implementation of these services on future operational ACTS-like systems can lead to unique quality, flexibility, and capacity characteristics at lower service costs. The specific service applications that could be supported range from low to high data rates and include both domestic and international applications.

  3. Denying Access to Commercial Communications Satellites

    National Research Council Canada - National Science Library

    Washington, Tania

    1999-01-01

    .... Commercial systems such as Orion, Panamsat, Iridium and Globalstar will provide the U.S. military and its potential adversaries with a relatively inexpensive and highly effective means to increase the command, control and communications (C3...

  4. Medical image transmission via communication satellite. Evaluation of bone scintigraphy

    International Nuclear Information System (INIS)

    Suzuki, Hideki; Inoue, Tomio; Endo, Keigo; Shimamoto, Shigeru.

    1995-01-01

    As compared with terrestrial circuits, the communication satellite possesses superior characteristics such as wide area coverage, broadcasting, high capacity, and robustness to disasters. Utilizing the narrow band channel (64 kbps) of the geostationary satellite JCSAT 1 located at the altitude of 36,000 km above the equator, the authors investigated satellite-relayed medical imagings by video signals, with bone scintigraphy as a model. Each bone scintigraphy was taken by a handy-video camera, digitalized and transmitted from faculty of technology located at 25 kilometers apart from our department. Clear bone scintigraphy was obtained via satellite, as seen on the view box. Eight nuclear physicians evaluated 20 cases of bone scintigraphy. ROC (Receiver Operating Characteristic) analysis was performed between the scintigraphies on view box and via satellite by the rating method. The area under the ROC curve was 91.6±2.6% via satellite, and 93.2±2.4% on the view box and there was no significant difference between them. These results suggest that the satellite communication is very useful and effective system to send nuclear imagings to distant institutes. (author)

  5. [Medical image transmission via communication satellite: evaluation of bone scintigraphy].

    Science.gov (United States)

    Suzuki, H; Inoue, T; Endo, K; Shimamoto, S

    1995-10-01

    As compared with terrestrial circuits, the communication satellite possesses superior characteristics such as wide area coverage, broadcasting, high capacity, and robustness to disasters. Utilizing the narrow band channel (64 kbps) of the geostationary satellite JCSAT1 located at the altitude of 36,000 km above the equator, the authors investigated satellite-relayed medical images by video signals, with bone scintigraphy as a model. Each bone scintigraphy was taken by a handy-video camera, digitalized and transmitted from faculty of technology located at 25 kilometers apart from our department. Clear bone scintigraphy was obtained via satellite, as seen on the view box. Eight nuclear physicians evaluated 20 cases of bone scintigraphy. ROC (Receiver Operating Characteristic) analysis was performed between the scintigraphies on view box and via satellite by the rating method. The area under the ROC curve was 91.6 +/- 2.6% via satellite, and 93.2 +/- 2.4% on the view box and there was no significant difference between them. These results suggest that the satellite communication is very useful and effective system to send nuclear imagings to distant institutes.

  6. College curriculum-sharing via CTS. [Communications Technology Satellite

    Science.gov (United States)

    Hudson, H. E.; Guild, P. D.; Coll, D. C.; Lumb, D. R.

    1975-01-01

    Domestic communication satellites and video compression techniques will increase communication channel capacity and reduce cost of video transmission. NASA Ames Research Center, Stanford University and Carleton University are participants in an experiment to develop, demonstrate, and evaluate college course sharing techniques via satellite using video compression. The universities will exchange televised seminar and lecture courses via CTS. The experiment features real-time video compression with channel coding and quadra-phase modulation for reducing transmission bandwidth and power requirements. Evaluation plans and preliminary results of Carleton surveys on student attitudes to televised teaching are presented. Policy implications for the U.S. and Canada are outlined.

  7. Application of Vision Metrology to In-Orbit Measurement of Large Reflector Onboard Communication Satellite for Next Generation Mobile Satellite Communication

    Science.gov (United States)

    Akioka, M.; Orikasa, T.; Satoh, M.; Miura, A.; Tsuji, H.; Toyoshima, M.; Fujino, Y.

    2016-06-01

    Satellite for next generation mobile satellite communication service with small personal terminal requires onboard antenna with very large aperture reflector larger than twenty meters diameter because small personal terminal with lower power consumption in ground base requires the large onboard reflector with high antenna gain. But, large deployable antenna will deform in orbit because the antenna is not a solid dish but the flexible structure with fine cable and mesh supported by truss. Deformation of reflector shape deteriorate the antenna performance and quality and stability of communication service. However, in case of digital beam forming antenna with phased array can modify the antenna beam performance due to adjustment of excitation amplitude and excitation phase. If we can measure the reflector shape precisely in orbit, beam pattern and antenna performance can be compensated with the updated excitation amplitude and excitation phase parameters optimized for the reflector shape measured every moment. Softbank Corporation and National Institute of Information and Communications Technology has started the project "R&D on dynamic beam control technique for next generation mobile communication satellite" as a contracted research project sponsored by Ministry of Internal Affairs and Communication of Japan. In this topic, one of the problem in vision metrology application is a strong constraints on geometry for camera arrangement on satellite bus with very limited space. On satellite in orbit, we cannot take many images from many different directions as ordinary vision metrology measurement and the available area for camera positioning is quite limited. Feasibility of vision metrology application and general methodology to apply to future mobile satellite communication satellite is to be found. Our approach is as follows: 1) Development of prototyping simulator to evaluate the expected precision for network design in zero order and first order 2) Trial

  8. DS-CDMA satellite diversity reception for personal satellite communication: Downlink performance analysis

    Science.gov (United States)

    DeGaudenzi, Riccardo; Giannetti, Filippo

    1995-01-01

    The downlink of a satellite-mobile personal communication system employing power-controlled Direct Sequence Code Division Multiple Access (DS-CDMA) and exploiting satellite-diversity is analyzed and its performance compared with a more traditional communication system utilizing single satellite reception. The analytical model developed has been thoroughly validated by means of extensive Monte Carlo computer simulations. It is shown how the capacity gain provided by diversity reception shrinks considerably in the presence of increasing traffic or in the case of light shadowing conditions. Moreover, the quantitative results tend to indicate that to combat system capacity reduction due to intra-system interference, no more than two satellites shall be active over the same region. To achieve higher system capacity, differently from terrestrial cellular systems, Multi-User Detection (MUD) techniques are likely to be required in the mobile user terminal, thus considerably increasing its complexity.

  9. NASA to launch second business communications satellite

    Science.gov (United States)

    1981-01-01

    The two stage Delta 3910 launch vehicle was chosen to place the second small business satellite (SBS-B) into a transfer orbit with an apogee of 36,619 kilometers and a perigee of 167 km, at an inclination of 27.7 degrees to Earth's equator. The firing and separation sequence and the inertial guidance system are described as well as the payload assist module. Facilities and services for tracking and control by NASA, COMSAT, Intelsat, and SBS are outlined and prelaunch operations are summarized.

  10. Payload system tradeoffs for mobile communications satellites

    Science.gov (United States)

    Moody, H. J.

    1990-01-01

    System level trade-offs carried out during Mobile Satellite (M-SAT) design activities are described. These trade-offs relate to the use of low level beam forming, flexible power and spectrum distribution, and selection of the number of beams to cover the service area. It is shown that antenna performance can be improved by sharing horns between beams using a low level beam forming network (BFN). Additionally, greatly increased power utilization is possible using a hybrid matrix concept to share power between beams.

  11. Advanced Communication Technology Satellite (ACTS) multibeam antenna technology verification experiments

    Science.gov (United States)

    Acosta, Roberto J.; Larko, Jeffrey M.; Lagin, Alan R.

    1992-01-01

    The Advanced Communication Technology Satellite (ACTS) is a key to reaching NASA's goal of developing high-risk, advanced communications technology using multiple frequency bands to support the nation's future communication needs. Using the multiple, dynamic hopping spot beams, and advanced on board switching and processing systems, ACTS will open a new era in communications satellite technology. One of the key technologies to be validated as part of the ACTS program is the multibeam antenna with rapidly reconfigurable hopping and fixed spot beam to serve users equipped with small-aperature terminals within the coverage areas. The proposed antenna technology experiments are designed to evaluate in-orbit ACTS multibeam antenna performance (radiation pattern, gain, cross pol levels, etc.).

  12. Modulation/demodulation techniques for satellite communications. Part 1: Background

    Science.gov (United States)

    Omura, J. K.; Simon, M. K.

    1981-01-01

    Basic characteristics of digital data transmission systems described include the physical communication links, the notion of bandwidth, FCC regulations, and performance measurements such as bit rates, bit error probabilities, throughputs, and delays. The error probability performance and spectral characteristics of various modulation/demodulation techniques commonly used or proposed for use in radio and satellite communication links are summarized. Forward error correction with block or convolutional codes is also discussed along with the important coding parameter, channel cutoff rate.

  13. Worldwide satellite communications for the energy utility industry. Final report

    International Nuclear Information System (INIS)

    Skelton, R.L.

    1998-07-01

    Recent and future generations of low earth orbiting (LEO) satellites are promising new possibilities for using space communications to achieve operational improvements and business expansion in energy supply and delivery industries. The ability to reach remote locations with relatively inexpensive devices and infrastructure is a unique property of satellites. Applications include remote monitoring and control of distributed resources and emergency and personal communication. Satellite systems are emerging as a significant opportunity for investment minded utilities. Over a dozen groups are planning to launch a total of 1200 LEOs in the period from 1996 to 2006, at a probable cost of over $20 Billion. This large number of systems can provide a worldwide mix of narrow band and wideband services including data, voice, video and Internet access. This paper examines the two primary factors which have limited applications in the energy industry: cost and propagation delay. The former has so far limited the technology to fixed communications with a few important sites such as remote substations. The latter has rendered the technology unsuitable for applications where critical protection mechanisms are involved. These constraints are effectively countered by the emerging LEO systems. Big LEOs will be used for voice service, little LEOs will be the systems of choice for most utility data applications. The author concludes that there are good technical and business reasons to reconsider future satellite communications as an option for meeting certain strategic business objectives in power system management and customer oriented information services

  14. Evaluation of spacecraft technology programs (effects on communication satellite business ventures), volume 1

    Science.gov (United States)

    Greenburg, J. S.; Gaelick, C.; Kaplan, M.; Fishman, J.; Hopkins, C.

    1985-01-01

    Commercial organizations as well as government agencies invest in spacecraft (S/C) technology programs that are aimed at increasing the performance of communications satellites. The value of these programs must be measured in terms of their impacts on the financial performane of the business ventures that may ultimately utilize the communications satellites. An economic evaluation and planning capability was developed and used to assess the impact of NASA on-orbit propulsion and space power programs on typical fixed satellite service (FSS) and direct broadcast service (DBS) communications satellite business ventures. Typical FSS and DBS spin and three-axis stabilized spacecraft were configured in the absence of NASA technology programs. These spacecraft were reconfigured taking into account the anticipated results of NASA specified on-orbit propulsion and space power programs. In general, the NASA technology programs resulted in spacecraft with increased capability. The developed methodology for assessing the value of spacecraft technology programs in terms of their impact on the financial performance of communication satellite business ventures is described. Results of the assessment of NASA specified on-orbit propulsion and space power technology programs are presented for typical FSS and DBS business ventures.

  15. Texas Telecommunication Satellite Demonstration Project. Planning Effort for Application of Communication Satellites in Education.

    Science.gov (United States)

    Education Service Center Region 4, Houston, TX.

    The primary goal of the Texas Telecommunication Satellite Demonstration consortium is to install, operate, and evaluate a comprehensive communication service delivery system which would provide the citizens of Texas with greater opportunity for equal access to education and information. The four major objectives of the demonstration are (1) to…

  16. Research of remote control for Chinese Antarctica Telescope based on iridium satellite communication

    Science.gov (United States)

    Xu, Lingzhe; Yang, Shihai

    2010-07-01

    Astronomers are ever dreaming of sites with best seeing on the Earth surface for celestial observation, and the Antarctica is one of a few such sites only left owing to the global air pollution. However, Antarctica region is largely unaccessible for human being due to lacking of fundamental living conditions, travel facilities and effective ways of communication. Worst of all, the popular internet source as a general way of communication scarcely exists there. Facing such a dilemma and as a solution remote control and data transmission for telescopes through iridium satellite communication has been put forward for the Chinese network Antarctic Schmidt Telescopes 3 (AST3), which is currently under all round research and development. This paper presents iridium satellite-based remote control application adapted to telescope control. The pioneer work in China involves hardware and software configuration utilizing techniques for reliable and secure communication, which is outlined in the paper too.

  17. DOA estimation for attitude determination on communication satellites

    Directory of Open Access Journals (Sweden)

    Yang Bin

    2014-06-01

    Full Text Available In order to determine an appropriate attitude of three-axis stabilized communication satellites, this paper describes a novel attitude determination method using direction of arrival (DOA estimation of a ground signal source. It differs from optical measurement, magnetic field measurement, inertial measurement, and global positioning system (GPS attitude determination. The proposed method is characterized by taking the ground signal source as the attitude reference and acquiring attitude information from DOA estimation. Firstly, an attitude measurement equation with DOA estimation is derived in detail. Then, the error of the measurement equation is analyzed. Finally, an attitude determination algorithm is presented using a dynamic model, the attitude measurement equation, and measurement errors. A developing low Earth orbit (LEO satellite which tests mobile communication technology with smart antennas can be stabilized in three axes by corporately using a magnetometer, reaction wheels, and three-axis magnetorquer rods. Based on the communication satellite, simulation results demonstrate the effectiveness of the method. The method could be a backup of attitude determination to prevent a system failure on the satellite. Its precision depends on the number of snapshots and the input signal-to-noise ratio (SNR with DOA estimation.

  18. Implementation of Multiple Access Techniques Applicable for Maritime Satellite Communications

    Directory of Open Access Journals (Sweden)

    Stojce Dimov Ilcev

    2013-12-01

    Full Text Available In this paper are introduced fundamentals, characteristics, advantages and disadvantages of Multiple Access (MA employed as transmission techniques in the Maritime Mobile Satellite Communications (MMSC between ships and Coast Earth Station (CES via Geostationary Earth Orbit (GEO or Not-GEO satellite constellations. In fixed satellite communication, as a rule, especially in MMSC many users are active at the same time. The problem of simultaneous communications between many single or multipoint mobile satellite users can be solved by using MA technique, such as Frequency Division Multiple Access (FDMA, Time Division Multiple Access (TDMA, Code Division Multiple Access (CDMA, Space Division Multiple Access (SDMA and Random (Packet Division Multiple Access (RDMA. Since the resources of the systems such as the transmitting power and the bandwidth are limited, it is advisable to use the channels with complete charge and to create a different MA to the channel. This generates a problem of summation and separation of signals in the transmission and reception parts, respectively. Deciding this problem consists in the development of orthogonal channels of transmission in order to divide signals from various users unambiguously on the reception part.

  19. Rural applications of Advanced Traveler Information Systems : evaluation of satellite communications systems for mayday applications

    Science.gov (United States)

    This report documents the results of an evaluation of satellite communication systems for mayday applications conducted as part of the Rural Applications of Advanced Traveler Information Systems (ATIS) study. It focuses on satellite communications sy...

  20. A network architecture for International Business Satellite communications

    Science.gov (United States)

    Takahata, Fumio; Nohara, Mitsuo; Takeuchi, Yoshio

    Demand Assignment (DA) control is expected to be introduced in the International Business Satellte communications (IBS) network in order to cope with a growing international business traffic. The paper discusses the DA/IBS network from the viewpoints of network configuration, satellite channel configuration and DA control. The network configuration proposed here consists of one Central Station with network management function and several Network Coordination Stations with user management function. A satellite channel configuration is also presented along with a tradeoff study on transmission bit rate, high power amplifier output power requirement, and service quality. The DA control flow and protocol based on CCITT Signalling System No. 7 are also proposed.

  1. Communication Media and Educational Technology: An Overview and Assessment with Reference to Communication Satellites.

    Science.gov (United States)

    Ohlman, Herbert

    In this survey and analysis of the present state and future trends of communication media and educational technology, particular emphasis is placed on the potential uses of communication satellites and the substitution of electronic transmission for physical distribution of educational materials. The author analyzes in detail the characteristics…

  2. 22 CFR 123.27 - Special licensing regime for export to U.S. allies of commercial communications satellite...

    Science.gov (United States)

    2010-04-01

    .... allies of commercial communications satellite components, systems, parts, accessories, attachments and... export to U.S. allies of commercial communications satellite components, systems, parts, accessories... associated technical data for commercial communications satellites, and who are so registered with the...

  3. Advanced mobile satellite communications system using Ka and MM-wave bands in Japan's R and D satellite project

    Science.gov (United States)

    Isobe, Shunkichi; Ohmori, Shingo; Hamamoto, Naokazu; Yamamoto, Minoru

    1991-01-01

    Communications Research Laboratory (CRL) studied an advanced mobile satellite communications system using Ka and millimeter-wave bands in the R&D Satellite project. The project started in 1990 and the satellite will be launched in 1997. On-board multi-beam interconnecting is one of basic functions to realize one-hop connection among Very Small Aperture Terminals (VSATs), mobile, and hand-held terminals in future mobile satellite communications system. An Intermediate Frequency (IF) filter bank and regenerative transponder are suitable for this function. The transponder configuration of an advanced mobile communications mission of the R&D Satellite for experiment is shown. High power transmitters of Ka and millimeter-wave bands, a 3x3 IF filter band and Single Channel Per Carrier/Time Division Multiplexing (SCPC/TDM) regenerative MODEMS, which will be boarded on the R&D Satellite, are being developed for the purpose of studying the feasibility of advanced mobile communications system.

  4. 78 FR 31576 - Enforcement Proceeding; Certain Two-Way Global Satellite Communication Devices, System and...

    Science.gov (United States)

    2013-05-24

    ...-Way Global Satellite Communication Devices, System and Components Thereof; Notice of Institution of... importation of certain two-way global satellite communication devices, system and components thereof by reason... importation any two-way global satellite communication devices, system, and components thereof that infringe...

  5. Emerging markets for satellite data communications in the public service

    Science.gov (United States)

    Potter, J. G.

    1978-01-01

    The paper discusses some of the current and potential markets for satellite data communications as projected by the Public Service Satellite Consortium (PSSC). Organizations in the public service sector are divided into three categories, depending on their expected benefits and organizational changes due to increased satellite telecommunications use: A - modest institutional adjustments are necessary and significant productivity gains are likely; B - institutional requirements picture is promising, but more information is needed to assess benefits and risk; and C - major institutional adjustments are needed, risks are high but possible benefits are high. These criteria are applied to the U.S. health care system, continuing education, equipment maintenance, libraries, environmental monitoring, and other potential markets. The potential revenues are seen to be significant, but what is needed is a cooperative effort by common carriers and major public service institutions to aggregate the market.

  6. First satellite mobile communication trials using BLQS-CDMA

    Science.gov (United States)

    Luzdemateo, Maria; Johns, Simon; Dothey, Michel; Vanhimbeeck, Carl; Deman, Ivan; Wery, Bruno

    1993-01-01

    In this paper, technical results obtained in the first MSBN Land mobile technical trial are reported. MSBN (Mobile Satellite Business Network) is a new program undertaken by the European Space Agency (ESA) to promote mobile satellite communication in Europe, in particular voice capability. The first phase of the MSBN system implementation plan is an experimental phase. Its purpose is to evaluate through field experiments the performance of the MSBN system prior to finalization of its specifications. Particularly, the objective is to verify in the field and possibly improve the performance of the novel satellite access technique BLQS-CDMA (Band Limited Quasi-Synchronous-Code Division Multiple Access), which is proposed as baseline for the MSBN.

  7. The 30/20 GHz communications satellite trunking network study

    Science.gov (United States)

    Kolb, W.

    1981-01-01

    Alternative transmission media for a CONUS-wide trunking network in the years 1990 and 2000 are examined. The alternative technologies comprised fiber optic cable, conventional C- and Ku-band satellites, and 30/20 GHz satellites. Three levels of implementation were considered - a 10-city network, a 20-city network, and a 40-city network. The cities selected were the major metropolitan areas with the greatest communications demand. All intercity voice, data, and video traffic carried more than 40 miles was included in the analysis. In the optimized network, traffic transmitted less than 500 miles was found to be better served by fiber optic cable in 1990. By the year 2000, the crossover point would be down to 200 miles, assuming availability of 30/20 GHz satellites.

  8. Institute for Communication, General Services, Administration

    International Nuclear Information System (INIS)

    Legrain, C.

    2007-01-01

    The article describes the key activities of the Institute for Communication, General Services and Administration (CSA) of the Belgian Nuclear Research Centre SCK-CEN. CSA deals with communication and knowledge management and co-ordinates courses on the fundamentals and applications of nuclear research. CSA also comprises the administrative, financial, logistic and central technical services, as well as human resources and ICT

  9. Effects of electronic communication in general practice

    NARCIS (Netherlands)

    van der Kam, WJ; Moorman, PW; Koppejan-Mulder, MJ

    2000-01-01

    Objective: To obtain insight into the effects of electronic communication on GPs by studying those publications in literature describing the effects of structured electronic clinical communication in general practice. Methods: We retrieved all publications in the English language indexed in MEDLINE

  10. DOD Use of Commercial Wideband Satellite Communications Systems: How Much is Needed, and How Do We Get It?

    National Research Council Canada - National Science Library

    Hutchens, Robert

    2001-01-01

    ..., A key enabler to this end is sufficient wideband satellite communications connectivity DoD's organic wideband satellite communications capabilities are inadequate, so commercial services must be used...

  11. Integration of an ion engine on the Communications Technology Satellite.

    Science.gov (United States)

    Payne, W. F.; Finke, R. C.

    1972-01-01

    An ion engine subsystem intended for satellite stationkeeping tasks is described. Ion thrusters are chosen to perform the task because the specific impulse is at least an order of magnitude higher than the commonly used reaction control jets. The higher the value of specific impulse, the greater the total impulse that can be attained for a given weight of propellant, hence cost benefits result. The integration, subsystem testing, and the operating plans for the ion engine experiment to be flown in 1975 on the Canadian Communications Technology Satellite (CTS) are described. The subsystem is designed to demonstrate north-south stationkeeping, attitude control by means of thrust vectoring, long-term space storage and restart capability, and compatibility with a high powered communications transponder.

  12. Medical image transmission via communication satellite: evaluation of ultrasonographic images.

    Science.gov (United States)

    Suzuki, H; Horikoshi, H; Shiba, H; Shimamoto, S

    1996-01-01

    As compared with terrestrial circuits, communication satellites possess superior characteristics such as wide area coverage, broadcasting functions, high capacity, and resistance to disasters. Utilizing the narrow band channel (64 kbps) of the stationary communication satellite JCSAT1 located at an altitude of 36,000 km above the equator, we investigated satelliterelayed dynamic medical images transmitted by video signals, using hepatic ultrasonography as a model. We conclude that the "variable playing speed transmission scheme" proposed by us is effective for the transmission of dynamic images in the narrow band channel. This promises to permit diverse utilization and applications for purposes such as the transmission of other types of ultrasonic images as well as remotely directed medical diagnosis and treatment.

  13. Spectrum and power allocation in cognitive multi-beam satellite communications with flexible satellite payloads

    Science.gov (United States)

    Liu, Zhihui; Wang, Haitao; Dong, Tao; Yin, Jie; Zhang, Tingting; Guo, Hui; Li, Dequan

    2018-02-01

    In this paper, the cognitive multi-beam satellite system, i.e., two satellite networks coexist through underlay spectrum sharing, is studied, and the power and spectrum allocation method is employed for interference control and throughput maximization. Specifically, the multi-beam satellite with flexible payload reuses the authorized spectrum of the primary satellite, adjusting its transmission band as well as power for each beam to limit its interference on the primary satellite below the prescribed threshold and maximize its own achievable rate. This power and spectrum allocation problem is formulated as a mixed nonconvex programming. For effective solving, we first introduce the concept of signal to leakage plus noise ratio (SLNR) to decouple multiple transmit power variables in the both objective and constraint, and then propose a heuristic algorithm to assign spectrum sub-bands. After that, a stepwise plus slice-wise algorithm is proposed to implement the discrete power allocation. Finally, simulation results show that adopting cognitive technology can improve spectrum efficiency of the satellite communication.

  14. Mechanical Design of Military Communication Satellite X-band PCM

    Directory of Open Access Journals (Sweden)

    Hyung Je Woo

    1998-12-01

    Full Text Available Before an actual military communications satellite is designed and constructed, a feasibility study should take place. The basic functions of such system can be observed and demonstrated in an X-Band payload simulator. For this purpose a Payload Concept Model (PCM for X-Band payload subsystem has been developed to simulate the workings of an actual military communications payload. This paper explains and illustrates the mechanical design, manufacture, and integration of the PCM. Basic RF tests also have been performed in order to verify the design requirement of the system. The results demonstrate successful development of the PCM and operation without RF losses.

  15. Attitude Control Subsystem for the Advanced Communications Technology Satellite

    Science.gov (United States)

    Hewston, Alan W.; Mitchell, Kent A.; Sawicki, Jerzy T.

    1996-01-01

    This paper provides an overview of the on-orbit operation of the Attitude Control Subsystem (ACS) for the Advanced Communications Technology Satellite (ACTS). The three ACTS control axes are defined, including the means for sensing attitude and determining the pointing errors. The desired pointing requirements for various modes of control as well as the disturbance torques that oppose the control are identified. Finally, the hardware actuators and control loops utilized to reduce the attitude error are described.

  16. Trellis-coded CPM for satellite-based mobile communications

    Science.gov (United States)

    Abrishamkar, Farrokh; Biglieri, Ezio

    1988-01-01

    Digital transmission for satellite-based land mobile communications is discussed. To satisfy the power and bandwidth limitations imposed on such systems, a combination of trellis coding and continuous-phase modulated signals are considered. Some schemes based on this idea are presented, and their performance is analyzed by computer simulation. The results obtained show that a scheme based on directional detection and Viterbi decoding appears promising for practical applications.

  17. ACTS TDMA network control. [Advanced Communication Technology Satellite

    Science.gov (United States)

    Inukai, T.; Campanella, S. J.

    1984-01-01

    This paper presents basic network control concepts for the Advanced Communications Technology Satellite (ACTS) System. Two experimental systems, called the low-burst-rate and high-burst-rate systems, along with ACTS ground system features, are described. The network control issues addressed include frame structures, acquisition and synchronization procedures, coordinated station burst-time plan and satellite-time plan changes, on-board clock control based on ground drift measurements, rain fade control by means of adaptive forward-error-correction (FEC) coding and transmit power augmentation, and reassignment of channel capacities on demand. The NASA ground system, which includes a primary station, diversity station, and master control station, is also described.

  18. Crosstalk cancellation on linearly and circularly polarized communications satellite links

    Science.gov (United States)

    Overstreet, W. P.; Bostian, C. W.

    1979-01-01

    The paper discusses the cancellation network approach for reducing crosstalk caused by depolarization on a dual-polarized communications satellite link. If the characteristics of rain depolarization are sufficiently well known, the cancellation network can be designed in a way that reduces system complexity, the most important parameter being the phase of the cross-polarized signal. Relevant theoretical calculations and experimental data are presented. The simplicity of the cancellation system proposed makes it ideal for use with small domestic or private earth terminals.

  19. Optical intersatellite links - Application to commercial satellite communications

    Science.gov (United States)

    Paul, D.; Faris, F.; Garlow, R.; Inukai, T.; Pontano, B.; Razdan, R.; Ganz, Aura; Caudill, L.

    1992-01-01

    Application of optical intersatellite links for commercial satellite communications services is addressed in this paper. The feasibility of commercialization centers around basic issues such as the need and derived benefits, implementation complexity and overall cost. In this paper, commercialization of optical ISLs is assessed in terms of the services provided, systems requirements and feasibility of appropriate technology. Both long- and short-range ISLs for GEO-GEO, GEO-LEO and LEO applications are considered. Impact of systems requirements on the payload design and use of advanced technology in reducing its mass, power, and volume requirements are discussed.

  20. The 30/20 GHz experimental communications satellite system

    Science.gov (United States)

    Sivo, J. N.

    NASA is continuing to pursue an agressive satellite communications technology development program focused on the 30/20 GHz frequency band. A review of the program progress to date is presented. Included is a discussion of the technology program status as well as a description of the experimental system concept under study. Expected system performance characteristics together with spacecraft and payload configuration details including weight and power budget is presented. Overall program schedules of both the technology development and the flight system development are included.

  1. More About Lens Antenna For Mobile/Satellite Communication

    Science.gov (United States)

    Rahmat-Samii, Y.; Bodnar, D. G.; Rainer, B. K.

    1990-01-01

    Report presents additional details of design of proposed phased-array antenna described in "Lens Antenna for Mobile/Satellite Communication" (NPO-16948). Intended to be compact and to lie flat on top of vehicle on ground. Transmits and receives circularly polarized radiation in frequency ranges of 821 to 825 MHz and 860 to 870 MHz. Transmitting and receiving beams electronically steerable to any of 48 evenly spaced directions to provide complete azimuth coverage, and would be fixed, but wide, in elevation, to provide coverage at elevation angles from 20 degrees to 60 degrees.

  2. Why is CDMA the solution for mobile satellite communication

    Science.gov (United States)

    Gilhousen, Klein S.; Jacobs, Irwin M.; Padovani, Roberto; Weaver, Lindsay A.

    1989-01-01

    It is demonstrated that spread spectrum Code Division Multiple Access (CDMA) systems provide an economically superior solution to satellite mobile communications by increasing the system maximum capacity with respect to single channel per carrier Frequency Division Multiple Access (FDMA) systems. Following the comparative analysis of CDMA and FDMA systems, the design of a model that was developed to test the feasibility of the approach and the performance of a spread spectrum system in a mobile environment. Results of extensive computer simulations as well as laboratory and field tests results are presented.

  3. Effect of digital scrambling on satellite communication links

    Science.gov (United States)

    Dessouky, K.

    1985-01-01

    Digital data scrambling has been considered for communication systems using NRZ symbol formats. The purpose is to increase the number of transitions in the data to improve the performance of the symbol synchronizer. This is accomplished without expanding the bandwidth but at the expense of increasing the data bit error rate (BER). Models for the scramblers/descramblers of practical interest are presented together with the appropriate link model. The effects of scrambling on the performance of coded and uncoded links are studied. The results are illustrated by application to the Tracking and Data Relay Satellite System (TDRSS) links. Conclusions regarding the usefulness of scrambling are also given.

  4. Estimation of the demand for public services communications. [market research and economic analysis for a communications satellite system

    Science.gov (United States)

    1976-01-01

    Market analyses and economic studies are presented to support NASA planning for a communications satellite system to provide public services in health, education, mobile communications, data transfer, and teleconferencing.

  5. The ACTS Flight System - Cost-Effective Advanced Communications Technology. [Advanced Communication Technology Satellite

    Science.gov (United States)

    Holmes, W. M., Jr.; Beck, G. A.

    1984-01-01

    The multibeam communications package (MCP) for the Advanced Communications Technology Satellite (ACTS) to be STS-launched by NASA in 1988 for experimental demonstration of satellite-switched TDMA (at 220 Mbit/sec) and baseband-processor signal routing (at 110 or 27.5 Mbit/sec) is characterized. The developmental history of the ACTS, the program definition, and the spacecraft-bus and MCP parameters are reviewed and illustrated with drawings, block diagrams, and maps of the coverage plan. Advanced features of the MPC include 4.5-dB-noise-figure 30-GHz FET amplifiers and 20-GHz TWTA transmitters which provide either 40-W or 8-W RF output, depending on rain conditions. The technologies being tested in ACTS can give frequency-reuse factors as high as 20, thus greatly expanding the orbit/spectrum resources available for U.S. communications use.

  6. 77 FR 58579 - Certain Two-Way Global Satellite Communication Devices, System and Components Thereof...

    Science.gov (United States)

    2012-09-21

    ... Communication Devices, System and Components Thereof; Institution of Investigation Pursuant to 19 U.S.C. 1337... certain two-way global satellite communication devices, system and components thereof that infringe one or... within the United States after importation of certain two-way global satellite communication devices...

  7. Optimizing communication satellites payload configuration with exact approaches

    Science.gov (United States)

    Stathakis, Apostolos; Danoy, Grégoire; Bouvry, Pascal; Talbi, El-Ghazali; Morelli, Gianluigi

    2015-12-01

    The satellite communications market is competitive and rapidly evolving. The payload, which is in charge of applying frequency conversion and amplification to the signals received from Earth before their retransmission, is made of various components. These include reconfigurable switches that permit the re-routing of signals based on market demand or because of some hardware failure. In order to meet modern requirements, the size and the complexity of current communication payloads are increasing significantly. Consequently, the optimal payload configuration, which was previously done manually by the engineers with the use of computerized schematics, is now becoming a difficult and time consuming task. Efficient optimization techniques are therefore required to find the optimal set(s) of switch positions to optimize some operational objective(s). In order to tackle this challenging problem for the satellite industry, this work proposes two Integer Linear Programming (ILP) models. The first one is single-objective and focuses on the minimization of the length of the longest channel path, while the second one is bi-objective and additionally aims at minimizing the number of switch changes in the payload switch matrix. Experiments are conducted on a large set of instances of realistic payload sizes using the CPLEX® solver and two well-known exact multi-objective algorithms. Numerical results demonstrate the efficiency and limitations of the ILP approach on this real-world problem.

  8. Evaluation of spacecraft technology programs (effects on communication satellite business ventures), volume 2

    Science.gov (United States)

    Greenburg, J. S.; Kaplan, M.; Fishman, J.; Hopkins, C.

    1985-01-01

    The computational procedures used in the evaluation of spacecraft technology programs that impact upon commercial communication satellite operations are discussed. Computer programs and data bases are described.

  9. Scheduling algorithm for data relay satellite optical communication based on artificial intelligent optimization

    Science.gov (United States)

    Zhao, Wei-hu; Zhao, Jing; Zhao, Shang-hong; Li, Yong-jun; Wang, Xiang; Dong, Yi; Dong, Chen

    2013-08-01

    Optical satellite communication with the advantages of broadband, large capacity and low power consuming broke the bottleneck of the traditional microwave satellite communication. The formation of the Space-based Information System with the technology of high performance optical inter-satellite communication and the realization of global seamless coverage and mobile terminal accessing are the necessary trend of the development of optical satellite communication. Considering the resources, missions and restraints of Data Relay Satellite Optical Communication System, a model of optical communication resources scheduling is established and a scheduling algorithm based on artificial intelligent optimization is put forwarded. According to the multi-relay-satellite, multi-user-satellite, multi-optical-antenna and multi-mission with several priority weights, the resources are scheduled reasonable by the operation: "Ascertain Current Mission Scheduling Time" and "Refresh Latter Mission Time-Window". The priority weight is considered as the parameter of the fitness function and the scheduling project is optimized by the Genetic Algorithm. The simulation scenarios including 3 relay satellites with 6 optical antennas, 12 user satellites and 30 missions, the simulation result reveals that the algorithm obtain satisfactory results in both efficiency and performance and resources scheduling model and the optimization algorithm are suitable in multi-relay-satellite, multi-user-satellite, and multi-optical-antenna recourses scheduling problem.

  10. Potential markets for a satellite-based mobile communications system

    Science.gov (United States)

    Jamieson, W. M.; Peet, C. S.; Bengston, R. J.

    1976-01-01

    The objective of the study was to define the market needs for improved land mobile communications systems. Within the context of this objective, the following goals were set: (1) characterize the present mobile communications industry; (2) determine the market for an improved system for mobile communications; and (3) define the system requirements as seen from the potential customer's viewpoint. The scope of the study was defined by the following parameters: (1) markets were confined to U.S. and Canada; (2) range of operation generally exceeded 20 miles, but this was not restrictive; (3) the classes of potential users considered included all private sector users, and non-military public sector users; (4) the time span examined was 1975 to 1985; and (5) highly localized users were generally excluded - e.g., taxicabs, and local paging.

  11. High Data Rate Satellite Communications for Environmental Remote Sensing

    Science.gov (United States)

    Jackson, J. M.; Munger, J.; Emch, P. G.; Sen, B.; Gu, D.

    2014-12-01

    Satellite to ground communication bandwidth limitations place constraints on current earth remote sensing instruments which limit the spatial and spectral resolution of data transmitted to the ground for processing. Instruments such as VIIRS, CrIS and OMPS on the Soumi-NPP spacecraft must aggregate data both spatially and spectrally in order to fit inside current data rate constraints limiting the optimal use of the as-built sensors. Future planned missions such as HyspIRI, SLI, PACE, and NISAR will have to trade spatial and spectral resolution if increased communication band width is not made available. A number of high-impact, environmental remote sensing disciplines such as hurricane observation, mega-city air quality, wild fire detection and monitoring, and monitoring of coastal oceans would benefit dramatically from enabling the downlinking of sensor data at higher spatial and spectral resolutions. The enabling technologies of multi-Gbps Ka-Band communication, flexible high speed on-board processing, and multi-Terabit SSRs are currently available with high technological maturity enabling high data volume mission requirements to be met with minimal mission constraints while utilizing a limited set of ground sites from NASA's Near Earth Network (NEN) or TDRSS. These enabling technologies will be described in detail with emphasis on benefits to future remote sensing missions currently under consideration by government agencies.

  12. NASA satellite communications application research. Phase 2: Efficient high power, solid state amplifier for EFH communications

    Science.gov (United States)

    Benet, James

    1993-01-01

    The final report describes the work performed from 9 Jun. 1992 to 31 Jul. 1993 on the NASA Satellite Communications Application Research (SCAR) Phase 2 program, Efficient High Power, Solid State Amplifier for EHF Communications. The purpose of the program was to demonstrate the feasibility of high-efficiency, high-power, EHF solid state amplifiers that are smaller, lighter, more efficient, and less costly than existing traveling wave tube (TWT) amplifiers by combining the output power from up to several hundred solid state amplifiers using a unique orthomode spatial power combiner (OSPC).

  13. A Mobile Communications Space Link Between the Space Shuttle Orbiter and the Advanced Communications Technology Satellite

    Science.gov (United States)

    Fink, Patrick; Arndt, G. D.; Bondyopadhyay, P.; Shaw, Roland

    1994-01-01

    A communications experiment is described as a link between the Space Shuttle Orbiter (SSO) and the Advanced Communications Technology Satellite (ACTS). Breadboarding for this experiment has led to two items with potential for commercial application: a 1-Watt Ka-band amplifier and a Ka-band, circularly polarized microstrip antenna. Results of the hybrid Ka-band amplifier show gain at 30 dB and a saturated output power of 28.5 dBm. A second version comprised of MMIC amplifiers is discussed. Test results of the microstrip antenna subarray show a gain of approximately 13 dB and excellent circular polarization.

  14. Equalization and detection for digital communication over nonlinear bandlimited satellite communication channels. Ph.D. Thesis

    Science.gov (United States)

    Gutierrez, Alberto, Jr.

    1995-01-01

    This dissertation evaluates receiver-based methods for mitigating the effects due to nonlinear bandlimited signal distortion present in high data rate satellite channels. The effects of the nonlinear bandlimited distortion is illustrated for digitally modulated signals. A lucid development of the low-pass Volterra discrete time model for a nonlinear communication channel is presented. In addition, finite-state machine models are explicitly developed for a nonlinear bandlimited satellite channel. A nonlinear fixed equalizer based on Volterra series has previously been studied for compensation of noiseless signal distortion due to a nonlinear satellite channel. This dissertation studies adaptive Volterra equalizers on a downlink-limited nonlinear bandlimited satellite channel. We employ as figure of merits performance in the mean-square error and probability of error senses. In addition, a receiver consisting of a fractionally-spaced equalizer (FSE) followed by a Volterra equalizer (FSE-Volterra) is found to give improvement beyond that gained by the Volterra equalizer. Significant probability of error performance improvement is found for multilevel modulation schemes. Also, it is found that probability of error improvement is more significant for modulation schemes, constant amplitude and multilevel, which require higher signal to noise ratios (i.e., higher modulation orders) for reliable operation. The maximum likelihood sequence detection (MLSD) receiver for a nonlinear satellite channel, a bank of matched filters followed by a Viterbi detector, serves as a probability of error lower bound for the Volterra and FSE-Volterra equalizers. However, this receiver has not been evaluated for a specific satellite channel. In this work, an MLSD receiver is evaluated for a specific downlink-limited satellite channel. Because of the bank of matched filters, the MLSD receiver may be high in complexity. Consequently, the probability of error performance of a more practical

  15. Spacecraft design project: Low Earth orbit communications satellite

    Science.gov (United States)

    Moroney, Dave; Lashbrook, Dave; Mckibben, Barry; Gardener, Nigel; Rivers, Thane; Nottingham, Greg; Golden, Bill; Barfield, Bill; Bruening, Joe; Wood, Dave

    1991-01-01

    This is the final product of the spacecraft design project completed to fulfill the academic requirements of the Spacecraft Design and Integration 2 course (AE-4871) taught at the U.S. Naval Postgraduate School. The Spacecraft Design and Integration 2 course is intended to provide students detailed design experience in selection and design of both satellite system and subsystem components, and their location and integration into a final spacecraft configuration. The design team pursued a design to support a Low Earth Orbiting (LEO) communications system (GLOBALSTAR) currently under development by the Loral Cellular Systems Corporation. Each of the 14 team members was assigned both primary and secondary duties in program management or system design. Hardware selection, spacecraft component design, analysis, and integration were accomplished within the constraints imposed by the 11 week academic schedule and the available design facilities.

  16. Considerations of digital phase modulation for narrowband satellite mobile communication

    Science.gov (United States)

    Grythe, Knut

    1990-01-01

    The Inmarsat-M system for mobile satellite communication is specified as a frequency division multiple access (FDMA) system, applying Offset Quadrature Phase Shift Keying (QPSK) for transmitting 8 kbit/sec in 10 kHz user channel bandwidth. We consider Digital Phase Modulation (DPM) as an alternative modulation format for INMARSAT-M. DPM is similar to Continuous Phase Modulation (CPM) except that DPM has a finite memory in the premodular filter with a continuous varying modulation index. It is shown that DPM with 64 states in the VA obtains a lower bit error rate (BER). Results for a 5 kHz system, with the same 8 kbit/sec transmitted bitstream, is also presented.

  17. Testing General Relativistic Predictions with the LAGEOS Satellites

    International Nuclear Information System (INIS)

    Peron, Roberto

    2014-01-01

    The spacetime around Earth is a good environment in order to perform tests of gravitational theories. According to Einstein’s view of gravitational phenomena, the Earth mass-energy content curves the surrounding spacetime in a peculiar way. This (relatively) quiet dynamical environment enables a good reconstruction of geodetic satellites (test masses) orbit, provided that high-quality tracking data are available. This is the case of the LAGEOS satellites, built and launched mainly for geodetic and geodynamical purposes, but equally good for fundamental physics studies. A review of these studies is presented, focusing on data, models, and analysis strategies. Some recent and less recent results are presented. All of them indicate general relativity theory as a very good description of gravitational phenomena, at least in the studied environment.

  18. Particle Filtering Equalization Method for a Satellite Communication Channel

    Directory of Open Access Journals (Sweden)

    Amblard Pierre-Olivier

    2004-01-01

    Full Text Available We propose the use of particle filtering techniques and Monte Carlo methods to tackle the in-line and blind equalization of a satellite communication channel. The main difficulties encountered are the nonlinear distortions caused by the amplifier stage in the satellite. Several processing methods manage to take into account these nonlinearities but they require the knowledge of a training input sequence for updating the equalizer parameters. Blind equalization methods also exist but they require a Volterra modelization of the system which is not suited for equalization purpose for the present model. The aim of the method proposed in the paper is also to blindly restore the emitted message. To reach this goal, a Bayesian point of view is adopted. Prior knowledge of the emitted symbols and of the nonlinear amplification model, as well as the information available from the received signal, is jointly used by considering the posterior distribution of the input sequence. Such a probability distribution is very difficult to study and thus motivates the implementation of Monte Carlo simulation methods. The presentation of the equalization method is cut into two parts. The first part solves the problem for a simplified model, focusing on the nonlinearities of the model. The second part deals with the complete model, using sampling approaches previously developed. The algorithms are illustrated and their performance is evaluated using bit error rate versus signal-to-noise ratio curves.

  19. Advanced Communication Technology Satellite (ACTS) multibeam antenna analysis and experiment

    Science.gov (United States)

    Acosta, Roberto J.; Lagin, Alan R.; Larko, Jeffrey M.; Narvaez, Adabelle

    1992-01-01

    One of the most important aspects of a satellite communication system design is the accurate estimation of antenna performance degradation. Pointing error, end coverage gain, peak gain degradation, etc. are the main concerns. The thermal or dynamic distortions of a reflector antenna structural system can affect the far-field antenna power distribution in a least four ways. (1) The antenna gain is reduced; (2) the main lobe of the antenna can be mispointed thus shifting the destination of the delivered power away from the desired locations; (3) the main lobe of the antenna pattern can be broadened, thus spreading the RF power over a larger area than desired; and (4) the antenna pattern sidelobes can increase, thus increasing the chances of interference among adjacent beams of multiple beam antenna system or with antenna beams of other satellites. The in-house developed NASA Lewis Research Center thermal/structural/RF analysis program was designed to accurately simulate the ACTS in-orbit thermal environment and predict the RF antenna performance. The program combines well establish computer programs (TRASYS, SINDA and NASTAN) with a dual reflector-physical optics RF analysis program. The ACTS multibeam antenna configuration is analyzed and several thermal cases are presented and compared with measurements (pre-flight).

  20. Cybersecurity threats to satellite communications: Towards a typology of state actor responses

    Science.gov (United States)

    Housen-Couriel, Deborah

    2016-11-01

    Cybersecurity threats to satellite communications are a relatively new phenomenon, yet have quickly come to the forefront of concern for the sustainability of satellite systems due to the vulnerabilities that such threats may exploit and negatively impact. These vulnerabilities are mission-critical: they include launch systems, communications, telemetry, tracking and command, and mission completion. They and other aspects of satellite communications depend heavily on secure and resilient cyber capabilities for all stages of the satellite's lifespan. Because of the inherently global nature of both satellite and cyberspace activities, these capabilities rely significantly on international cooperation for setting a baseline of agreed legal norms that protect satellites and satellite communications. This critical cooperation is relevant during all mission phases, from planning to final wrap-up. Under optimal circumstances, the norms and standards protecting satellites and satellite transmissions are developed and enforced by those nation-state actors that are committed to system operability and overall mission sustainability for those satellites launched under their aegis and responsibility. However, when breaches of international law do occur in the form of hostile cyber events that cause damage to satellite communications, a range of measures should be available to the victim state, provided by the appropriate legal regime or regimes. This article proposes that a comprehensive and integrative multi-stakeholder review be undertaken in the near future of the measures available under international law for responding to hostile acts directed at satellite systems and communications, in a manner that takes into account both existing regimes of international law reviewed herein, as well as considerations of cybersecurity. These measures will depend upon the characterization of hostile interference with satellite transmissions in accordance with a proposed typology of

  1. Using satellite communications for a mobile computer network

    Science.gov (United States)

    Wyman, Douglas J.

    1993-01-01

    The topics discussed include the following: patrol car automation, mobile computer network, network requirements, network design overview, MCN mobile network software, MCN hub operation, mobile satellite software, hub satellite software, the benefits of patrol car automation, the benefits of satellite mobile computing, and national law enforcement satellite.

  2. Network design consideration of a satellite-based mobile communications system

    Science.gov (United States)

    Yan, T.-Y.

    1986-01-01

    Technical considerations for the Mobile Satellite Experiment (MSAT-X), the ground segment testbed for the low-cost spectral efficient satellite-based mobile communications technologies being developed for the 1990's, are discussed. The Network Management Center contains a flexible resource sharing algorithm, the Demand Assigned Multiple Access scheme, which partitions the satellite transponder bandwidth among voice, data, and request channels. Satellite use of multiple UHF beams permits frequency reuse. The backhaul communications and the Telemetry, Tracking and Control traffic are provided through a single full-coverage SHF beam. Mobile Terminals communicate with the satellite using UHF. All communications including SHF-SHF between Base Stations and/or Gateways, are routed through the satellite. Because MSAT-X is an experimental network, higher level network protocols (which are service-specific) will be developed only to test the operation of the lowest three levels, the physical, data link, and network layers.

  3. An up-link power control for demand assignment International Business Satellite Communications Network

    Science.gov (United States)

    Nohara, Mitsuo; Takeuchi, Yoshio; Takahata, Fumio

    Up-link power control (UPC) is one of the essential technologies to provide efficient satellite communication systems operated at frequency bands above 10 GHz. A simple and cost-effective UPC scheme applicable to a demand assignment international business satellite communications system has been developed. This paper presents the UPC scheme, including the hardware implementation and its performance.

  4. GUST86 - An analytical ephemeris of the Uranian satellites. [General Uranus Satellite Theory

    Science.gov (United States)

    Laskar, J.; Jacobson, R. A.

    1987-01-01

    The General Uranus Satellite Theory GUST (Laskar, 1986) is used for the construction of an analytical ephemeris for the Uranian satellites. The theory is fitted against earth-based observations from 1911 to 1986, and all radio and optical data obtained during Voyager encounter with Uranus. Earth-based observations alone allow the determination of masses which are within 15 percent of the values determined by the Uranus flyby. The analysis of all the observations confirm the values of the masses obtained during the encounter (Stone and Miner, 1986) and give a complete set of dynamical parameters for the analytical theory. An analytical ephemeris, GUST86, with an estimated precision of about 100 km with respect to Uranus is obtained.

  5. Economic benefits of the Space Station to commercial communication satellite operators

    Science.gov (United States)

    Price, Kent M.; Dixson, John E.; Weyandt, Charles J.

    1987-01-01

    The economic and financial aspects of newly defined space-based activities, procedures, and operations (APOs) and associated satellite system designs are presented that have the potential to improve economic performance of future geostationary communications satellites. Launch insurance, launch costs, and the economics of APOs are examined. Retrieval missions and various Space Station scenarios are addressed. The potential benefits of the new APOs to the commercial communications satellite system operator are quantified.

  6. CHI: A General Agent Communication Framework

    Energy Technology Data Exchange (ETDEWEB)

    Goldsmith, S.Y.; Phillips, L.R.; Spires, S.V.

    1998-12-17

    We have completed and exercised a communication framework called CHI (CLOS to HTML Interface) by which agents can communicate with humans. CHI follows HTTP (HyperText Transfer Protocol) and produces HTML (HyperText Markup Language) for use by WWW (World-Wide Web) browsers. CHI enables the rapid and dynamic construction of interface mechanisms. The essence of CHI is automatic registration of dynamically generated interface elements to named objects in the agent's internal environment. The agent can access information in these objects at will. State is preserved, so an agent can pursue branching interaction sequences, activate failure recovery behaviors, and otherwise act opportunistically to maintain a conversation. The CHI mechanism remains transparent in multi-agent, multi-user environments because of automatically generated unique identifiers built into the CHI mechanism. In this paper we discuss design, language, implementation, and extension issues, and, by way of illustration, examine the use of the general CHI/HCHI mechanism in a specific international electronic commerce system. We conclude that the CHI mechanism is an effective, efficient, and extensible means of the agent/human communication.

  7. Development of a demand assignment/TDMA system for international business satellite communications

    Science.gov (United States)

    Nohara, Mitsuo; Takeuchi, Yoshio; Takahata, Fumio; Hirata, Yasuo; Yamazaki, Yoshiharu

    An experimental IBS (international business satellite) communications system based on a demand assignment and TDMA (time-division multiple-access) operation has been developed. The system utilizes a limited satellite resource efficiently and provides various kinds of ISDN services totally. A discussion is presented of the IBS network configurations suitable to international communications and describes the developed communications system from the viewpoint of the hardware and software implementation. The performance in terms of the transmission quality and call processing is also demonstrated.

  8. Communications Satellite Systems Conference, 9th, San Diego, CA, March 7-11, 1982, Collection of Technical Papers

    Science.gov (United States)

    The Shuttle-to-Geostationary Orbital Transfer by mid-level thrust is considered along with multibeam antenna concepts for global communications, the antenna pointing systems for large communication satellites, the connection phase of multidestination protocols for broadcast satellites, and an experiment in high-speed international packet switching. Attention is given to a dynamic switch matrix for the TDMA satellite switching system, the characterization of 16 bit microprocessors for space use, in-orbit operation and test of Intelsat V satellites, the first operational communications system via satellite in Europe, the Arab satellite communications systems, second generation business satellite systems for Europe, and a high performance Ku-band satellite for the 1980's. Other topics investigated are related to Ku-band terminal design tradeoffs, progress in the definition of the Italian satellite for domestic telecommunications, future global satellite systems for Intelsat, and satellite refuelling in orbit.

  9. A Study on Fuel Estimation Algorithms for a Geostationary Communication & Broadcasting Satellite

    Directory of Open Access Journals (Sweden)

    Jong Won Eun

    2000-12-01

    Full Text Available It has been developed to calculate fuel budget for a geostationary communication and broadcasting satellite. It is quite essential that the pre-launch fuel budget estimation must account for the deterministic transfer and drift orbit maneuver requirements. After on-station, the calculation of satellite lifetime should be based on the estimation of remaining fuel and assessment of actual performance. These estimations step from the proper algorithms to produce the prediction of satellite lifetime. This paper concentrates on the fuel estimation method that was studied for calculation of the propellant budget by using the given algorithms. Applications of this method are discussed for a communication and broadcasting satellite.

  10. OPTIS - A satellite test of Special and General Relativity

    Science.gov (United States)

    Dittus, H.; Lämmerzahl, C.; Peters, A.; Schiller, S.

    OPTIS has been proposed as a small satellite platform in a high elliptical orbit (apogee 40,000 km, perigee 10,000 km) and is designed for high precision tests of foundations of Special and General Relativity. The experimental set-up consists of two ultrastable Nd:YAG lasers, two crossed optical resonators (monolithic cavities), an atomic clock, and an optical comb generator. OPTIS enables (1) a Michelson- Morley experiment to test the isotropy of light propagation (constancy of light speed, dc/c) with an accuracy of 1 part in 101 8 , (2) a Kennedey-Thorndike experiment to measure the independence of the light speed from the velocity of the laboratory in the order of 1 part in 101 6 , and (3) a test of the gravitational red shift by comparing the atomic clock and an optical clock on a precision level of 1 part in 104 . To avoid any influence from atmospheric drag, solar radiation, or earth albedo, the satellite needs drag free control, to depress the residual acceleration down to 10-14 m/s 2 in the frequency range between 100 to 1,000 Hz, and thermal control to stabilize the cavity temperature variation, dT/T, to 1 part in 107 during 100 s and to 1 part in 105 during 1 orbit.

  11. In-Space Internet-Based Communications for Space Science Platforms Using Commercial Satellite Networks

    Science.gov (United States)

    Kerczewski, Robert J.; Bhasin, Kul B.; Fabian, Theodore P.; Griner, James H.; Kachmar, Brian A.; Richard, Alan M.

    1999-01-01

    The continuing technological advances in satellite communications and global networking have resulted in commercial systems that now can potentially provide capabilities for communications with space-based science platforms. This reduces the need for expensive government owned communications infrastructures to support space science missions while simultaneously making available better service to the end users. An interactive, high data rate Internet type connection through commercial space communications networks would enable authorized researchers anywhere to control space-based experiments in near real time and obtain experimental results immediately. A space based communications network architecture consisting of satellite constellations connecting orbiting space science platforms to ground users can be developed to provide this service. The unresolved technical issues presented by this scenario are the subject of research at NASA's Glenn Research Center in Cleveland, Ohio. Assessment of network architectures, identification of required new or improved technologies, and investigation of data communications protocols are being performed through testbed and satellite experiments and laboratory simulations.

  12. INVESTIGATION OF ADS-B MESSAGES TRAFFIC VIA SATELLITE COMMUNICATION CHANNEL

    OpenAIRE

    Volodymyr Kharchenko; Wang Bo; Andrii Grekhov; Marina Kovalenko

    2014-01-01

    For modelling of ADS-B messages transmition with the help of low-orbit satellite complex Іrіdіumdifferent models of communication channel "Aircraft-to-Satellites-to-Ground Stations" were built using NetCrackerProfessіonal 4.1 software. Influence of aircraft and satellites amount on average link utilization and message travellingtime was studied for telecommunication channels with intersatellite link and bent-pipe architecture. The effect ofcommunication channel "saturation" during simultaneou...

  13. A Study on Fuel Estimation Algorithms for a Geostationary Communication & Broadcasting Satellite

    OpenAIRE

    Jong Won Eun

    2000-01-01

    It has been developed to calculate fuel budget for a geostationary communication and broadcasting satellite. It is quite essential that the pre-launch fuel budget estimation must account for the deterministic transfer and drift orbit maneuver requirements. After on-station, the calculation of satellite lifetime should be based on the estimation of remaining fuel and assessment of actual performance. These estimations step from the proper algorithms to produce the prediction of satellite lifet...

  14. Next-Generation NASA Earth-Orbiting Relay Satellites: Fusing Optical and Microwave Communications

    Science.gov (United States)

    Israel, David J.; Shaw, Harry

    2018-01-01

    NASA is currently considering architectures and concepts for the generation of relay satellites that will replace the Tracking and Data Relay Satellite (TDRS) constellation, which has been flying since 1983. TDRS-M, the last of the second TDRS generation, launched in August 2017, extending the life of the TDRS constellation beyond 2030. However, opportunities exist to re-engineer the concepts of geosynchronous Earth relay satellites. The needs of the relay satellite customers have changed dramatically over the last 34 years since the first TDRS launch. There is a demand for greater bandwidth as the availability of the traditional RF spectrum for space communications diminishes and the demand for ground station access grows. The next generation of NASA relay satellites will provide for operations that have factored in these new constraints. In this paper, we describe a heterogeneous constellation of geosynchronous relay satellites employing optical and RF communications. The new constellation will enable new optical communications services formed by user-to-space relay, space relay-to-space relay and space relay-to-ground links. It will build upon the experience from the Lunar Laser Communications Demonstration from 2013 and the Laser Communications Relay Demonstration to be launched in 2019.Simultaneous to establishment of the optical communications space segment, spacecraft in the TDRS constellation will be replaced with RF relay satellites with targeted subsets of the TDRS capabilities. This disaggregation of the TDRS service model will allow for flexibility in replenishing the needs of legacy users as well as addition of new capabilities for future users. It will also permit the U.S. government access to launch capabilities such as rideshare and to hosted payloads that were not previously available.In this paper, we also explore how the next generation of Earth relay satellites provides a significant boost in the opportunities for commercial providers to the

  15. Next-Generation NASA Earth-Orbiting Relay Satellites: Fusing Microwave and Optical Communications

    Science.gov (United States)

    Israel, David J.

    2018-01-01

    NASA is currently considering architectures and concepts for the generation of relay satellites that will replace the Tracking and Data Relay Satellite (TDRS) constellation, which has been flying since 1983. TDRS-M, the last of the second TDRS generation, launched in August 2017, extending the life of the TDRS constellation beyond 2030. However, opportunities exist to re-engineer the concepts of geosynchronous Earth relay satellites. The needs of the relay satellite customers have changed dramatically over the last 34 years since the first TDRS launch. There is a demand for greater bandwidth as the availability of the traditional RF spectrum for space communications diminishes and the demand for ground station access grows. The next generation of NASA relay satellites will provide for operations that have factored in these new constraints. In this paper, we describe a heterogeneous constellation of geosynchronous relay satellites employing optical and RF communications. The new constellation will enable new optical communications services formed by user-to-space relay, space relay-to-space relay and space relay-to-ground links. It will build upon the experience from the Lunar Laser Communications Demonstration from 2013 and the Laser Communications Relay Demonstration to be launched in 2019.Simultaneous to establishment of the optical communications space segment, spacecraft in the TDRS constellation will be replaced with RF relay satellites with targeted subsets of the TDRS capabilities. This disaggregation of the TDRS service model will allow for flexibility in replenishing the needs of legacy users as well as addition of new capabilities for future users. It will also permit the U.S. government access to launch capabilities such as rideshare and to hosted payloads that were not previously available. In this paper, we also explore how the next generation of Earth relay satellites provides a significant boost in the opportunities for commercial providers to the

  16. The Future of Satellite Communications. Resource Management and the Needs of Nations.

    Science.gov (United States)

    Hinchman, Walter R.; Dunn, D. A.

    Recent events suggest that Intelsat (the 68-nation International Telecommunications Satellite Consortium) will coordinate a number of domestic and regional systems that provide satellite communications services, some of which will be maintained by Intelsat and some of which will be independent. This report addresses the problems of conflict in…

  17. Communication schemes for olfar's inter-satellite links

    NARCIS (Netherlands)

    Budianu, A.; Willink-Castro, T.J.; Meijerink, Arjan; Bentum, Marinus Jan

    2012-01-01

    The Orbiting Low Frequency Array for Radio astronomy(OLFAR) project is aimed at developing a radio telescope in space sensitive for the 0.3–30 MHz range by using a swarm of more than 50 identical nano-satellites. The satellites will form a very large aperture, capable of capturing very weak

  18. Communications Satellite Receiver Systems for Public Schools: A Technical Primer.

    Science.gov (United States)

    Texas Education Agency, Austin.

    Designed to aid school districts contemplating use of some of the telecommunications services now available by satellite, this document contains information on home satellite receiving dishes (Television Receive-Only--TVROs), which can receive radio signals carrying television, sound, and data. This information includes: some factors involved in…

  19. IMT-2000 Satellite Standards with Applications to Mobile Air Traffic Communications Networks

    Science.gov (United States)

    Shamma, Mohammed A.

    2004-01-01

    The International Mobile Telecommunications - 2000 (IMT-2000) standard and more specifically the Satellite component of it, is investigated as a potential alternative for communications to aircraft mobile users en-route and in terminal area. Its application to Air Traffic Management (ATM) communication needs is considered. A summary of the specifications of IMT-2000 satellite standards are outlined. It is shown via a system research analysis that it is possible to support most air traffic communication needs via an IMT-2000 infrastructure. This technology can compliment existing, or future digital aeronautical communications technologies such as VDL2, VDL3, Mode S, and UAT.

  20. Do future commercial broadband communication satellites really need laser-communication intersatellite links (ISLs)?

    Science.gov (United States)

    Freidell, James E.

    1997-04-01

    Large commercial satellite programs requiring ISLs are growing in number and maturing. An important segment of the commercial satellite market, and its ISL needs, is discussed in the paper. ISL value will increase as long-haul terrestrial backbones become increasingly congested. Providing interregional and intercontinental connectivity via ISL presents far lower cost and fewer problems than relying on terrestrial fiber-optic networks. To demonstrate this, a new metric is proposed which allows 'apples-to- apples' cost/performance comparisons between laser communications in GEO, LEO, and terrestrial fiber-optics. ISL requirements in to the next decade are predicted >= 50-100 Gb/s full duplex. Many attitudinal changes must be embraced among those who choose to focus on this new commercial business. Foremost among these is a preponderance to delivering fully acceptable hardware fast and at low cost, as opposed to merely designing such. Considerable attention must be given business considerations foreign to professionals who have spent time in the government or government contracting sectors. Successful ISL customers will come to recognize that ISLs are not commodity products. Failure to embrace these attitudes will nonetheless constitute decision to which the commercial market, and particularly the financial market, will appropriately respond.

  1. Key issues of multiple access technique for LEO satellite communication systems

    Institute of Scientific and Technical Information of China (English)

    温萍萍; 顾学迈

    2004-01-01

    The large carrier frequency shift caused by the high-speed movement of satellite (Doppler effects) and the propagation delay on the up-down link are very critical issues in an LEO satellite communication system, which affects both the selection and the implementation of a suitable access method. A Doppler based multiple access technique is used here to control the flow and an MPRMA-HS protocol is proposed for the application in LEO satellite communication systems. The extended simulation trials prove that the proposed scheme seems to be a very promising access method.

  2. Application of communications satellites to educational development. [technology utilization/information systems - bibliographies

    Science.gov (United States)

    Morgan, R. P.

    1975-01-01

    A summary of research is presented. The broad objectives of this interdisciplinary research effort were: (1) to assess the role of satellite communications as a means of improving education in the United States, as well as in less-developed areas of the world; (2) to generate basic knowledge which will aid in making rational decisions about satellite application in the field of education in the years ahead; (3) to devise systems and strategies for improving education; and (4) to educate individuals who will be knowledgeable about aspects of satellite communications policy which transcend any single discipline.

  3. Study to forecast and determine characteristics of world satellite communications market

    Science.gov (United States)

    Filep, R. T.; Schnapf, A.; Fordyce, S. W.

    1983-01-01

    The world commercial communications satellite market during the spring and summer of 1983 was examined and characteristics and forecasts of the market extending to the year 2000 were developed. Past, present and planned satellites were documented in relation to frequencies, procurement and launch dates, costs, transponders, and prime contractor. Characteristics of the market are outlined for the periods 1965 - 1985, 1986 - 1989, and 1990 - 2000. Market share forecasts, discussions of potential competitors in various world markets, and profiles of major communication satellite manufacturing and user countries are documented.

  4. INVESTIGATION OF ADS-B MESSAGES TRAFFIC VIA SATELLITE COMMUNICATION CHANNEL

    Directory of Open Access Journals (Sweden)

    Volodymyr Kharchenko

    2014-12-01

    Full Text Available For modelling of ADS-B messages transmition with the help of low-orbit satellite complex Іrіdіumdifferent models of communication channel "Aircraft-to-Satellites-to-Ground Stations" were built using NetCrackerProfessіonal 4.1 software. Influence of aircraft and satellites amount on average link utilization and message travellingtime was studied for telecommunication channels with intersatellite link and bent-pipe architecture. The effect ofcommunication channel "saturation" during simultaneous data transmission through a satellite communicationchannel from many planes was investigated.

  5. Dual Fine Tracking Control of a Satellite Laser Communication Uplink

    National Research Council Canada - National Science Library

    Noble, Louis A

    2006-01-01

    A dual fine tracking control system (FTCS) is developed for a single aperture optical communication receiver to compensate for high frequency disturbances affecting tracking of two incident laser communication beams...

  6. ESA personal communications and digital audio broadcasting systems based on non-geostationary satellites

    Science.gov (United States)

    Logalbo, P.; Benedicto, J.; Viola, R.

    1993-01-01

    Personal Communications and Digital Audio Broadcasting are two new services that the European Space Agency (ESA) is investigating for future European and Global Mobile Satellite systems. ESA is active in promoting these services in their various mission options including non-geostationary and geostationary satellite systems. A Medium Altitude Global Satellite System (MAGSS) for global personal communications at L and S-band, and a Multiregional Highly inclined Elliptical Orbit (M-HEO) system for multiregional digital audio broadcasting at L-band are described. Both systems are being investigated by ESA in the context of future programs, such as Archimedes, which are intended to demonstrate the new services and to develop the technology for future non-geostationary mobile communication and broadcasting satellites.

  7. Modeling and Performance Analysis of 10 Gbps Inter-satellite Optical Wireless Communication Link

    Science.gov (United States)

    Singh, Mehtab

    2017-12-01

    Free-space optical (FSO) communication has the advantages of two of the most predominant data transmission technologies - optical fiber communication and wireless communication. Most of the technical aspects of FSO are similar to that of optical fiber communication, with major difference in the information signal propagation medium which is free space in case of FSO rather than silica glass in optical fiber communication. One of the most important applications of FSO is inter-satellite optical wireless communication (IsOWC) links which will be deployed in the future in space. The IsOWC links have many advantages over the previously existing microwave satellite communication technologies such as higher bandwidth, lower power consumption, low cost of implementation, light size, and weight. In this paper, modeling and performance analysis of a 10-Gbps inter-satellite communication link with two satellites separated at a distance of 1,200 km has been done using OPTISYSTEM simulation software. Performance has been analyzed on the basis of quality factor, signal to noise ratio (SNR), and total power of the received signal.

  8. Australia's Domestic Communication Satellite and Education: Has Education Missed the Boat?

    Science.gov (United States)

    White, Peter B.

    Educators have been critized for being unable to develop any firm plans for the use of Australia's Domestic Communications Satellite (AUSSAT). However, conferences, talks, and papers have resulted in some significant achievements. First, it is now possible to raise issues of communications and telecommunications planning at the very highest…

  9. Forecast of space shuttle flight requirements for launch of commercial communications satellites

    Science.gov (United States)

    1977-01-01

    The number of communication satellites required over the next 25 years to support domestic and regional communication systems for telephony, telegraphy and other low speed data; video teleconferencing, new data services, direct TV broadcasting; INTELSAT; and maritime and aeronautical services was estimated to determine the number of space shuttle flights necessary for orbital launching.

  10. 78 FR 19172 - Earth Stations Aboard Aircraft Communicating with Fixed-Satellite Service Geostationary-Orbit...

    Science.gov (United States)

    2013-03-29

    ... FEDERAL COMMUNICATIONS COMMISSION 47 CFR Parts 2 and 25 [IB Docket No. 12-376; FCC 12-161] Earth Stations Aboard Aircraft Communicating with Fixed-Satellite Service Geostationary-Orbit Space Stations... the Federal Register of March 8, 2013. The document proposed rules for Earth Stations Aboard Aircraft...

  11. Mission studies on constellation of LEO satellites with remote-sensing and communication payloads

    Science.gov (United States)

    Chen, Chia-Ray; Hwang, Feng-Tai; Hsueh, Chuang-Wei

    2017-09-01

    Revisiting time and global coverage are two major requirements for most of the remote sensing satellites. Constellation of satellites can get the benefit of short revisit time and global coverage. Typically, remote sensing satellites prefer to choose Sun Synchronous Orbit (SSO) because of fixed revisiting time and Sun beta angle. The system design and mission operation will be simple and straightforward. However, if we focus on providing remote sensing and store-and-forward communication services for low latitude countries, Sun Synchronous Orbit will not be the best choice because we need more satellites to cover the communication service gap in low latitude region. Sometimes the design drivers for remote sensing payloads are conflicted with the communication payloads. For example, lower orbit altitude is better for remote sensing payload performance, but the communication service zone will be smaller and we need more satellites to provide all time communication service. The current studies focus on how to provide remote sensing and communication services for low latitude countries. A cost effective approach for the mission, i.e. constellation of microsatellites, will be evaluated in this paper.

  12. Satellites

    International Nuclear Information System (INIS)

    Burns, J.A.; Matthews, M.S.

    1986-01-01

    The present work is based on a conference: Natural Satellites, Colloquium 77 of the IAU, held at Cornell University from July 5 to 9, 1983. Attention is given to the background and origins of satellites, protosatellite swarms, the tectonics of icy satellites, the physical characteristics of satellite surfaces, and the interactions of planetary magnetospheres with icy satellite surfaces. Other topics include the surface composition of natural satellites, the cratering of planetary satellites, the moon, Io, and Europa. Consideration is also given to Ganymede and Callisto, the satellites of Saturn, small satellites, satellites of Uranus and Neptune, and the Pluto-Charon system

  13. PLANCK, the Satellite: a New Experimental Test of General Relativity

    Directory of Open Access Journals (Sweden)

    Rabounski D.

    2008-04-01

    Full Text Available If the origin of a microwave background (EMB is the Earth, what would be its density and associated dipole anisotropy measured at different altitudes from the surface of the Earth? The mathematical methods of the General Theory of Relativity are applied herein to answer these questions. The density of the EMB is answered by means of Einstein's equations for the electromagnetic field of the Earth. The dipole anisotropy, which is due to the rapid motion of the source (the Earth in the weak intergalactic field, is analysed by using the geodesic equations for light-like particles (photons, which are mediators for electromagnetic radiation. It is shown that the EMB decreases with altitude so that the density of its energy at the altitude of the COBE orbit (900km is 0.68 times less than that at the altitude of a U2 aeroplane (25km. Furthermore, the density at the 2nd Lagrange point (1.5 million km, the position of the WMAP and PLANCK satellites should be only 10$^{-7}$ of the value detected by a U2 aeroplane or at the COBE orbit. The dipole anisotropy of the EMB doesn't depend on altitude from the surface of the Earth, it should be the same irrespective of the altitude at which measurements are taken. This result is in support to the experimental and observational analysis conducted by P.-M.Robitaille, according to which the 2.7K microwave background, first observed by Penzias and Wilson, is not of cosmic origin, but of the Earth, and is generated by the oceans. WMAP indicated the same anisotropy of the microwave background at the 2nd Lagrange point that near the Earth. Therefore when PLANCK, which is planned on July, 2008, will manifest the 2.7K monopole microwave signal deceased at the 2nd Langrange point, it will be a new experimental verification of Einstein's theory.

  14. PLANCK, the Satellite: a New Experimental Test of General Relativity

    Directory of Open Access Journals (Sweden)

    Borissova L.

    2008-04-01

    Full Text Available If the origin of a microwave background (EMB is the Earth, what would be its density and associated dipole anisotropy measured at different altitudes from the surface of the Earth? The mathematical methods of the General Theory of Relativity are applied herein to answer these questions. The density of the EMB is answered by means of Einstein’s equations for the electromagnetic field of the Earth. The dipole anisotropy, which is due to the rapid motion of the source (the Earth in the weak intergalactic field, is analysed by using the geodesic equations for light-like particles (photons, which are mediators for electromagnetic radiation. It is shown that the EMB decreases with altitude so that the density of its energy at the altitude of the COBE orbit (900km is 0.68 times less than that at the altitude of a U2 aeroplane (25 km. Furthermore, the density at the 2nd Lagrange point (1.5 million km, the position of the WMAP and PLANCK satellites should be only 1E-7 of the value detected by a U2 aeroplane or at the COBE orbit. The dipole anisotropy of the EMB doesn’t depend on altitude from the surface of the Earth, it should be the same irrespective of the altitude at which measurements are taken. This result is in support to the experimental and observational analysis conducted by P.-M. Robitaille, according to which the 2.7 K microwave background, first observed by Penzias and Wilson, is not of cosmic origin, but of the Earth, and is generated by the oceans. WMAP indicated the same anisotropy of the microwave background at the 2nd Lagrange point that near the Earth. Therefore when PLANCK, which is planned on July, 2008, will manifest the 2.7 K monopole microwave signal deceased at the 2nd Langrange point, it will be a new experimental verification of Einstein’s theory.

  15. Development of Communication Technologies in Turkey: A General Overview

    Directory of Open Access Journals (Sweden)

    Dilek Penpece

    2011-01-01

    Full Text Available Communication is a system that senders have possibility to send message to receiver in general meaning. It is considered that as a modern Turkish economy should use communication systems largely. It is critically important to show Turkey’s usage of communication technologies as a country that keeps up with new developments in the world. Communication tools that examined in this study are postal services, newspaper and magazines, fixed-line telephone and mobile phone, internet. According to examined period it is resulted that the usage of communication tools increased. It is observed that some communication tools usage decreased caused by different factors in some terms.

  16. An approach to effective UHF (S/L band) data communications for satellite Personal Communication Service (PCS)

    Science.gov (United States)

    Hayase, Joshua Y.

    1995-01-01

    Reliable signaling information transfer is fundamental in supporting the needs of data communication PCS via LMS (Land Mobile Service) SSs (satellite systems). The needs of the system designer can be satisfied only through the collection of media information that can be brought to bear on the pertinent design issues. We at ISI hope to continue our dialogue with fading media experts to address the unique data communications needs of PCS via LMS SSs.

  17. New media in political communication: general approaches

    Directory of Open Access Journals (Sweden)

    Chekunova Marina A.

    2016-01-01

    Full Text Available Nowadays, in transformation of the realm of political communication, a more important part is given to the so-called «new social media». Previously, political communication was seen as a process of production, dissemination and perception of political information for the purpose of achieving a consent regarding one or another political action. Additionally, communication appeared as a mechanism of one-way information exchange. Under new conditions, political communication becomes a tool of ensuring the process of preparation, making and implementing political decisions. In a modern understanding, an informational message is built by means of specific cooperation between communicants. In this regard, information sources appear as a specific base for state actions. This paper deals with old (traditional and new social media and lists several characteristics that help distinguish these media. It also shows how authorities and representatives of political opposition can use social media to achieve their political purposes. This article analyses not only benefits but also drawbacks in the application of new information technologies in politics, considering a problem of manipulation as a main disadvantage. It also compares the use of social networks by authorities in Russia and abroad. Because of differences in political culture, social networks are not popular with Russian authorities. However, the number of social networking users among Russian politicians is increasing year by year. Moreover, the most popular network with them is Twitter. A conclusion can be drawn that new media play an important role in creating a system of rules of conduct on the Internet and in establishing a specific culture of electronic communication between representatives of authority and society.

  18. Analysis of synchronous digital-modulation schemes for satellite communication

    Science.gov (United States)

    Takhar, G. S.; Gupta, S. C.

    1975-01-01

    The multipath communication channel for space communications is modeled as a multiplicative channel. This paper discusses the effects of multiplicative channel processes on the symbol error rate for quadrature modulation (QM) digital modulation schemes. An expression for the upper bound on the probability of error is derived and numerically evaluated. The results are compared with those obtained for additive channels.

  19. Global mobile satellite communications theory for maritime, land and aeronautical applications

    CERN Document Server

    Ilčev, Stojče Dimov

    2017-01-01

    This book discusses current theory regarding global mobile satellite communications (GMSC) for maritime, land (road and rail), and aeronautical applications. It covers how these can enable connections between moving objects such as ships, road and rail vehicles and aircrafts on one hand, and on the other ground telecommunications subscribers through the medium of communications satellites, ground earth stations, Terrestrial Telecommunication Networks (TTN), Internet Service Providers (ISP) and other wireless and landline telecommunications providers. This new edition covers new developments and initiatives that have resulted in land and aeronautical applications and the introduction of new satellite constellations in non-geostationary orbits and projects of new hybrid satellite constellations. The book presents current GMSC trends, mobile system concepts and network architecture using a simple mode of style with understandable technical information, characteristics, graphics, illustrations and mathematics equ...

  20. Accurate beacon positioning method for satellite-to-ground optical communication.

    Science.gov (United States)

    Wang, Qiang; Tong, Ling; Yu, Siyuan; Tan, Liying; Ma, Jing

    2017-12-11

    In satellite laser communication systems, accurate positioning of the beacon is essential for establishing a steady laser communication link. For satellite-to-ground optical communication, the main influencing factors on the acquisition of the beacon are background noise and atmospheric turbulence. In this paper, we consider the influence of background noise and atmospheric turbulence on the beacon in satellite-to-ground optical communication, and propose a new locating algorithm for the beacon, which takes the correlation coefficient obtained by curve fitting for image data as weights. By performing a long distance laser communication experiment (11.16 km), we verified the feasibility of this method. Both simulation and experiment showed that the new algorithm can accurately obtain the position of the centroid of beacon. Furthermore, for the distortion of the light spot through atmospheric turbulence, the locating accuracy of the new algorithm was 50% higher than that of the conventional gray centroid algorithm. This new approach will be beneficial for the design of satellite-to ground optical communication systems.

  1. Technology programs and related policies - Impacts on communications satellite business ventures

    Science.gov (United States)

    Greenberg, J. S.

    1985-01-01

    The DOMSAT II stochastic communication satellite business venture financial planning simulation model is described. The specification of business scenarios and the results of several analyses are presented. In particular, the impacts of NASA on-orbit propulsion and power technology programs are described. The effects of insurance rates and self-insurance and of the use of the Space Shuttle and Ariane transportation systems on a typical fixed satellite service business venture are discussed.

  2. Comparison of TCeMA and TDMA for Inter-Satellite Communications using OPNET Simulation

    Science.gov (United States)

    Hain, Regina Rosales; Ramanathan, Ram; Bergamo, Marcos; Wallett, Thomas M.

    2003-01-01

    A robust data link protocol, enabling unique physical and MAC layer technologies and sub-network level protocols, is needed in order to take advantage of the full potential of using both TDMA and CDMA in a satellite communication network. A novel MAC layer protocol, TDMA with CDMA-encoding multiple access (TCeMA) integrated with null-steered digital beam-forming spatial multiplexing, is investigated to support flexible spacecraft communications. Abstract models of the TCeMA and TDMA processes are developed in OPNFiT and a comparison of the performances of TCeMA and TDMA in a satellite network simulation are made. TCeMA provides the better connectivity and capacity with respect to TDMA for satellite communication traffic.

  3. A description of QUALCOMM Automatic Satellite Position Reporting (QASPR(R)) for mobile communications

    Science.gov (United States)

    Ames, William G.

    1990-01-01

    Two satellite position reporting has been introduced into the OmniTRACS mobile satellite communication system. This system significantly improves position reporting reliability and accuracy while simplifying the terminal's hardware. The positioning technique uses the original OmniTRACS TDMA timing signal formats in the forward and return link directions plus an auxiliary, low power forward link signal through a second satellite to derive distance values. The distances are then converted into the mobile terminal's latitude and longitude in real time. A minor augmentation of the spread spectrum profile of the return link allowed the resolution of periodic ambiguities. The system also locates the two satellites in real time with fixed platforms in known locations using identical mobile terminal hardware. Initial accuracies of 1/4 mile have been realized uniformly throughout the USA using a satellite separation of 22 degrees and there are no dead zones, skywaves, or cycle slips as found in terrestrial systems like LORAN-C.

  4. Intelligent Media Access Protocol for SDR-Based Satellite Communications

    Data.gov (United States)

    National Aeronautics and Space Administration — In a communications channel, the space environment between a spacecraft and an Earth ground station can potentially cause the loss of a data link or at least degrade...

  5. Improved Coast Guard Communications Using Commercial Satellites and WWW Technology

    Science.gov (United States)

    1997-06-18

    Information collection and distribution are essential components of most Coast Guard missions. However, information needs have typically outpaced the ability of the installed communications systems to meet those needs. This mismatch leads to reduced ...

  6. Wideband autonomous cognitive radios for networked satellites communications, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — There is growing recognition that success in a variety of space mission types can be greatly enhanced by making current communication transceivers and networks...

  7. Communications satellite business ventures - Measuring the impact of technology programmes and related policies

    Science.gov (United States)

    Greenberg, J. S.

    1986-01-01

    An economic evaluation and planning procedure which assesses the effects of various policies on fixed satellite business ventures is described. The procedure is based on a stochastic financial simulation model, the Domsat II, which evaluates spacecraft reliability, market performance, and cost uncertainties. The application of the Domsat II model to the assessment of NASA's ion thrusters for on-orbit propulsion and GaAs solar cell technology is discussed. The effects of insurance rates and the self-insurance option on the financial performance of communication satellite business ventures are investigated. The selection of a transportation system for placing the satellites into GEO is analyzed.

  8. Positional stabilization of communications satellites - The RITA ion propulsion system is ready for commercial use

    Science.gov (United States)

    The radiofrequency ion thruster assembly (RITA) intended for service aboard the new Artemis communications satellite will operate for three hours twice a day, in order to furnish orbital position adjustments that keep antennas accurately pointed toward the earth. These engines are, despite such frequent and sustained use, projected to eject no more than 30 kG of Xe over the course of a decade. RITA operation is also extremely reliable and, due to its very low propellant consumption, is the basis of a long satellite service life. RITA will be among the 15 experiments that are to be performed by ESA's Eureca research satellite.

  9. Satellite communication system for emergency monitoring within the Chernobyl exclusion zone

    International Nuclear Information System (INIS)

    Franchini, C.; Mensa, M.; Kanevsky, V.A.

    1997-01-01

    A Satellite Emergency Monitoring system of the Chernobyl Exclusive Zone (SEM CEZ) was designed to provide the Ukraine authorities and the neighbouring countries with updated information when an emergency situation occurs in the Exclusion Zone. This is of particular importance when environment contamination has transboundary effect. SEM system consists of mobile and fixed sensors reporting data via a dedicated satellite communications link. Mobile sensors are fitted with Global Positioning System (GPS) receivers that determine current coordinates of the sensor. Sensors data are transmitted to the Emergency Monitoring Centre equipped with PC and a satellite terminal. Both sensors data and the current position are visualized on digital maps

  10. Prediction of Communication Outage Period between Satellite and Earth station Due to Sun Interference

    Directory of Open Access Journals (Sweden)

    Yongjun Song

    2010-03-01

    Full Text Available We developed a computer program to predict solar interference period. To calculate Sun‘s position, we used DE406 ephemerides and Earth ellipsoid model. The Sun‘s position error is smaller than 10arcsec. For the verification of the calculation, we used TU media ground station on Seongsu-dong, and MBSAT geostationary communication satellite. We analysis errors, due to satellite perturbation and antenna align. The time error due to antenna align has -35 to +16 seconds at 0.1 degree, and -27 to +41 seconds at 0.25 degree. The time errors derived by satellite perturbation has 30 to 60 seconds.

  11. Fiber optical sensing on-board communication satellites

    Science.gov (United States)

    Hurni, A.; Lemke, N. M. K.; Roner, M.; Obermaier, J.; Putzer, P.; Kuhenuri Chami, N.

    2017-11-01

    Striving constantly to reduce mass, AIT effort and overall cost of the classical point-to-point wired temperature sensor harness on-board telecommunication satellites, OHB System (formerly Kayser-Threde) has introduced the Hybrid Sensor Bus (HSB) system. As a future spacecraft platform element, HSB relies on electrical remote sensor units as well as fiber-optical sensors, both of which can serially be connected in a bus architecture. HSB is a modular measurement system with many applications, also thanks to the opportunities posed by the digital I²C bus. The emphasis, however, is on the introduction of fiber optics and especially fiber-Bragg grating (FBG) temperature sensors as disruptive innovation for the company's satellite platforms. The light weight FBG sensors are directly inscribed in mechanically robust and radiation tolerant fibers, reducing the need for optical fiber connectors and splices to a minimum. Wherever an FBG sensor shall be used, the fiber is glued together with a corresponding temperature transducer to the satellites structure or to a subsystem. The transducer is necessary to provide decoupling of mechanical stress, but simultaneously ensure a high thermal conductivity. HSB has been developed in the frame of an ESA-ARTES program with European and German co-funding and will be verified as flight demonstrator on-board the German Heinrich Hertz satellite (H2Sat). In this paper the Engineering Model development of HSB is presented and a Fiber-optical Sensor Multiplexer for a more flexible sensor bus architecture is introduced. The HSB system aims at telecommunication satellite platforms with an operational life time beyond 15 years in geostationary orbit. It claims a high compatibility in terms of performance and interfaces with existing platforms while it was designed with future applications with increased radiation exposure already in mind. In its basic configuration HSB consists of four modules which are the Power Supply Unit, the HSB

  12. The C3PO project: a laser communication system concept for small satellites

    Science.gov (United States)

    d'Humières, Benoît; Esmiller, Bruno; Gouy, Yann; Steck, Emilie; Quintana, Crisanto; Faulkner, Graham; O'Brien, Dominic; Sproll, Fabian; Wagner, Paul; Hampf, Daniel; Riede, Wolfgang; Salter, Michael; Wang, Qin; Platt, Duncan; Jakonis, Darius; Piao, Xiaoyu; Karlsson, Mikael; Oberg, Olof; Petermann, Ingemar; Michalkiewicz, Aneta; Krezel, Jerzy; Debowska, Anna; Thueux, Yoann

    2017-02-01

    The satellite market is shifting towards smaller (micro and nanosatellites), lowered mass and increased performance platforms. Nanosatellites and picosatellites have been used for a number of new, innovative and unique payloads and missions. This trend requires new concepts for a reduced size, a better performance/weight ratio and a reduction of onboard power consumption. In this context, disruptive technologies, such as laser-optical communication systems, are opening new possibilities. This paper presents the C3PO1 system, "advanced Concept for laser uplink/ downlink CommuniCation with sPace Objects", and the first results of the development of its key technologies. This project targets the design of a communications system that uses a ground-based laser to illuminate a satellite, and a Modulating Retro-Reflector (MRR) to return a beam of light modulated by data to the ground. This enables a downlink, without a laser source on the satellite. This architecture suits well to small satellite applications so as high data rates are potentially provided with very low board mass. C3PO project aims to achieve data rates of 1Gbit/s between LEO satellites and Earth with a communication payload mass of less than 1kilogram. In this paper, results of the initial experiments and demonstration of the key technologies will be shown.

  13. R and D limited partnerships (possible applications in advanced communications satellite technology experiment program)

    Science.gov (United States)

    1985-01-01

    Typical R&D limited partnership arrangements, advantages and disadvantages of R&D limited partnership (RDLPs) and antitrust and tax implications are described. A number of typical forms of RDLPs are described that may be applicable for use in stimulating R&D and experimental programs using the advanced communications technology satellite. The ultimate goal is to increase the rate of market penetration of goods and/or services based upon advanced satellite communications technology. The conditions necessary for these RDLP forms to be advantageous are outlined.

  14. Intersatellite Link (ISL) application to commercial communications satellites. Volume 1: Executive summary

    Science.gov (United States)

    Young, S. Lee

    1987-01-01

    Based on a comprehensive evaluation of the fundamental Intersatellite Link (ISL) systems characteristics, potential applications of ISLs to domestic, regional, and global commercial satellite communications were identified, and their cost-effectiveness and other systems benefits quantified wherever possible. Implementation scenarios for the cost-effective communications satellite systems employing ISLs were developed for the first launch in 1993 to 1994 and widespread use of ISLs in the early 2000's. Critical technology requirements for both the microwave (60 GHz) and optical (0.85 micron) ISL implementations were identified, and their technology development programs, including schedule and cost estimates, were derived.

  15. Leo Satellite Communication through a LEO Constellation using TCP/IP Over ATM

    Science.gov (United States)

    Foore, Lawrence R.; Konangi, Vijay K.; Wallett, Thomas M.

    1999-01-01

    The simulated performance characteristics for communication between a terrestrial client and a Low Earth Orbit (LEO) satellite server are presented. The client and server nodes consist of a Transmission Control Protocol /Internet Protocol (TCP/IP) over ATM configuration. The ATM cells from the client or the server are transmitted to a gateway, packaged with some header information and transferred to a commercial LEO satellite constellation. These cells are then routed through the constellation to a gateway on the globe that allows the client/server communication to take place. Unspecified Bit Rate (UBR) is specified as the quality of service (QoS). Various data rates are considered.

  16. Europe at the crossroads: The future of its satellite communications industry

    Science.gov (United States)

    Bartholome, Pierre; Battrick, B.

    1993-11-01

    Ways of adapting the European Space Agency's role to the new industrial environment of satellite communications, which is characterized by the disappearance of traditional monopolies and the introduction of competition, are presented. As far as ESA is concerned, it is found that a general consensus exists to recommend that the agency should take a much wider view of its role as a research and development (R&D) organization. It should no longer restrict its field of activity to space technology only, but should take a more global approach. More emphasis should be placed on the development of complete communications systems and of commercial applications. European industry indeed feels very strongly that it is not getting from ESA the support it needs to match the performance of its foreign competitors on the world markets. It can only succeed commercially in the fierce competition with the U.S. and Japan if a substantial R&D program is defined and funded at European level, as required by the magnitude of the financial effort necessary. It is concluded that anything the agency untertakes in the future to redress the situation would produce much greater dividends if it were part of a coherent plan where all the European partners play their role in a cooperative spirit. It is recommended that the European Commission should, as a matter of urgency, take steps to institute a concertation mechanism involving all major players with a view to defining and developing a coherent strategy for Europe.

  17. Causal relationships between solar proton events and single event upsets for communication satellites

    Science.gov (United States)

    Lohmeyer, W. Q.; Cahoy, K.; Liu, Shiyang

    In this work, we analyze a historical archive of single event upsets (SEUs) maintained by Inmarsat, one of the world's leading providers of global mobile satellite communications services. Inmarsat has operated its geostationary communication satellites and collected extensive satellite anomaly and telemetry data since 1990. Over the course of the past twenty years, the satellites have experienced more than 226 single event upsets (SEUs), a catch-all term for anomalies that occur in a satellite's electronics such as bit-flips, trips in power supplies, and memory changes in attitude control systems. While SEUs are seemingly random and difficult to predict, we correlate their occurrences to space weather phenomena, and specifically show correlations between SEUs and solar proton events (SPEs). SPEs are highly energetic protons that originate from solar coronal mass ejections (CMEs). It is thought that when these particles impact geostationary (GEO) satellites they can cause SEUs as well as solar array degradation. We calculate the associated statistical correlations that each SEU occurs within one day, one week, two weeks, and one month of 10 MeV SPEs between 10 - 10,000 particle flux units (pfu). However, we find that SPEs are most prevalent at solar maximum and that the SEUs on Inmarsat's satellites occur out of phase with the solar maximum. Ultimately, this suggests that SPEs are not the primary cause of the Inmarsat SEUs. A better understanding of the causal relationship between SPEs and SEUs will help the satellite communications industry develop component and operational space weather mitigation techniques as well as help the space weather community to refine radiation models.

  18. NASA/DARPA advanced communications technology satellite project for evaluation of telemedicine outreach using next-generation communications satellite technology: Mayo Foundation participation.

    Science.gov (United States)

    Gilbert, B K; Mitchell, M P; Bengali, A R; Khandheria, B K

    1999-08-01

    To describe the development of telemedicine capabilities-application of remote consultation and diagnostic techniques-and to evaluate the feasibility and practicality of such clinical outreach to rural and underserved communities with limited telecommunications infrastructures. In 1992, Mayo Foundation (Rochester, Minn, Jacksonville, Fla, and Scottsdale, Ariz), the National Aeronautics and Space Administration, and the Defense Advanced Research Projects Agency collaborated to create a complex network of fiberoptic landlines, video recording systems, satellite terminals, and specially developed data translators linking Mayo sites with other locations in the continental United States on an on-demand basis. The purpose was to transmit data via the asynchronous transfer mode (ATM) digital communications protocol over the Advanced Communications Technology Satellite. The links were intended to provide a conduit for transmission of data for patient-specific consultations between physicians, evaluation of medical imagery, and medical education for clinical staffs at remote sites. Low-data-rate (LDR) experiments went live late in 1993. Mayo Clinic Rochester successfully provided medical consultation and services to 2 small regional medical facilities. High-data-rate (HDR) experiments included studies of remote digital echocardiography, store-and-forward telemedicine, cardiac catheterization, and teleconsultation for congenital heart disease. These studies combined landline data transmission with use of the satellite. The complexity of the routing paths and network components, immaturity of available software, and inexperience with existing telecommunications caused significant study delays. These experiments demonstrated that next-generation satellite technology can provide batch and real-time imagery for telemedicine. The first-generation of the ATM and satellite network technology used in these experiments created several technical problems and inconveniences that should

  19. Defense Science Board Task Force on Military Satellite Communication and Tactical Networking. Executive Summary

    Science.gov (United States)

    2017-03-01

    Interface Processor BCT Brigade Combat Team BFT Blue Force Tracking BLOS Beyond Line-of-Sight C2 Command And Control C2E Communications in...Satellite Communications and Tactical Networking Appendix D-2 GIG Global Information Grid GMR Ground Mobile Radio GPS Global Positioning System...System SIPRNet Secret Internet Protocol Router Network SITREPS Situational Reports SMART -T Secure Mobile Anti-Jam Reliable Tactical Terminal SMC Space

  20. A communication protocol for mobile satellite systems affected by rain attenuation

    Science.gov (United States)

    Lay, Norman; Dessouky, Khaled

    1992-01-01

    A communication protocol is described that has been developed as part of a K/Ka-band mobile terminal breadboard system to be demonstrated through NASA's Advanced Communications Technology Satellite (ACTS) in 1993. The protocol is aimed at providing the means for enhancing link availability and continuity by supporting real-time data rate selection and changes during rain events. Particular attention is given to the system architecture; types of links, connections, and packets; the protocol procedures; and design rationales.

  1. Air traffic management system design using satellite based geo-positioning and communications assets

    Science.gov (United States)

    Horkin, Phil

    1995-01-01

    The current FAA and ICAO FANS vision of Air Traffic Management will transition the functions of Communications, Navigation, and Surveillance to satellite based assets in the 21st century. Fundamental to widespread acceptance of this vision is a geo-positioning system that can provide worldwide access with best case differential GPS performance, but without the associated problems. A robust communications capability linking-up aircraft and towers to meet the voice and data requirements is also essential. The current GPS constellation does not provide continuous global coverage with a sufficient number of satellites to meet the precision landing requirements as set by the world community. Periodic loss of the minimum number of satellites in view creates an integrity problem, which prevents GPS from becoming the primary system for navigation. Furthermore, there is reluctance on the part of many countries to depend on assets like GPS and GLONASS which are controlled by military communities. This paper addresses these concerns and provides a system solving the key issues associated with navigation, automatic dependent surveillance, and flexible communications. It contains an independent GPS-like navigation system with 27 satellites providing global coverage with a minimum of six in view at all times. Robust communications is provided by a network of TDMA/FDMA communications payloads contained on these satellites. This network can support simultaneous communications for up to 30,000 links, nearly enough to simultaneously support three times the current global fleet of jumbo air passenger aircraft. All of the required hardware is directly traceable to existing designs.

  2. Optimization of Power Allocation for Multiusers in Multi-Spot-Beam Satellite Communication Systems

    Directory of Open Access Journals (Sweden)

    Heng Wang

    2014-01-01

    Full Text Available In recent years, multi-spot-beam satellite communication systems have played a key role in global seamless communication. However, satellite power resources are scarce and expensive, due to the limitations of satellite platform. Therefore, this paper proposes optimizing the power allocation of each user in order to improve the power utilization efficiency. Initially the capacity allocated to each user is calculated according to the satellite link budget equations, which can be achieved in the practical satellite communication systems. The problem of power allocation is then formulated as a convex optimization, taking account of a trade-off between the maximization of the total system capacity and the fairness of power allocation amongst the users. Finally, an iterative algorithm based on the duality theory is proposed to obtain the optimal solution to the optimization. Compared with the traditional uniform resource allocation or proportional resource allocation algorithms, the proposed optimal power allocation algorithm improves the fairness of power allocation amongst the users. Moreover, the computational complexity of the proposed algorithm is linear with both the numbers of the spot beams and users. As a result, the proposed power allocation algorithm is easy to be implemented in practice.

  3. Precoded generalized space shift keying for indoor visible light communications

    KAUST Repository

    Kadampot, Ishaque Ashar; Park, Kihong; Alouini, Mohamed-Slim

    2014-01-01

    We consider a visible light communication system with 2 transmit light emitting diodes (LED) and nr receive photodiodes. An optical generalized space shift keying modulation scheme is considered for the transmission of bits where each LED can

  4. Improving the satellite communication efficiency of the accumulative acknowledgement strategies

    Science.gov (United States)

    Duarte, Otto Carlos M. B.; de Lima, Heliomar Medeiros

    The performances of two finite buffer error recovery strategies are analyzed. In both strategies the retransmission request decision between selective repeat and continuous retransmission is based on an imminent buffer overflow condition. These are accumulative acknowledgment schemes, but in the second strategy the selective-repeat control frame is uniquely an individual negative acknowledgment. The two strategies take advantage of the availability of a greater buffer capacity, making the most of the selective repeat, postponing the sending of a continuous retransmission request. Numerical results show a better performance very close to the ideal, but it does not integrally conform to the high-level data link control (HDLC) procedures. It is shown that these strategies are well suited for high-speed data transfer in the high-error-rate satellite environment.

  5. 77 FR 51045 - Certain Two-Way Global Satellite Communication Devices, System and Components Thereof; Notice of...

    Science.gov (United States)

    2012-08-23

    ... Certain Two-Way Global Satellite Communication Devices, System and Components Thereof, DN 2907; the... INTERNATIONAL TRADE COMMISSION [Docket No. 2907] Certain Two-Way Global Satellite Communication Devices, System and Components Thereof; Notice of Receipt of Complaint; Solicitation of Comments Relating...

  6. The design of a linear L-band high power amplifier for mobile communication satellites

    Science.gov (United States)

    Whittaker, N.; Brassard, G.; Li, E.; Goux, P.

    1990-01-01

    A linear L-band solid state high power amplifier designed for the space segment of the Mobile Satellite (MSAT) mobile communication system is described. The amplifier is capable of producing 35 watts of RF power with multitone signal at an efficiency of 25 percent and with intermodulation products better than 16 dB below carrier.

  7. Study on networking issues of medium earth orbit satellite communications systems

    Science.gov (United States)

    Araki, Noriyuki; Shinonaga, Hideyuki; Ito, Yasuhiko

    1993-01-01

    Two networking issues of communications systems with medium earth orbit (MEO) satellites, namely network architectures and location determination and registration methods for hand-held terminals, are investigated in this paper. For network architecture, five candidate architectures are considered and evaluated in terms of signaling traffic. For location determination and registration, two methods are discussed and evaluated.

  8. Communication and Control in the Canadian North: The Role of Interactive Satellites.

    Science.gov (United States)

    Valaskakis, Gail G.

    In 1972 the Canadian government launched its first domestic communications satellite, Anik A, which relays direct broadcast television and telephone messages to northern communities. The impact of television on Inuit life has raised issues and concerns pertaining to native language broadcasting, media access and control, and cultural identity…

  9. Summary of the CTS Transient Event Counter data after one year of operation. [Communication Technology Satellite

    Science.gov (United States)

    Stevens, N. J.; Klinect, V. W.; Gore, J. V.

    1977-01-01

    The environmental charging of satellite surfaces during geomagnetic substorms is the apparent cause of a significant number of anomalous events occurring on geosynchronous satellites since the early 1970's. Electromagnetic pulses produced in connection with the differential charging of insulators can couple into the spacecraft harness and cause electronic switching anomalies. An investigation conducted to determine the response of the spacecraft surfaces to substorm particle fluxes makes use of a harness transient detector. The harness transient detector, called the Transient Event Counter (TEC) was built and integrated into the Canadian-American Communications Technology Satellite (CTS). A description of the TEC and its operational characteristics is given and the obtained data are discussed. The data show that the satellite surfaces appear to be charged to the point that discharges occur and that the discharge-induced transients couple into the wire harnesses.

  10. Study of LEO-SAT microwave link for broad-band mobile satellite communication system

    Science.gov (United States)

    Fujise, Masayuki; Chujo, Wataru; Chiba, Isamu; Furuhama, Yoji; Kawabata, Kazuaki; Konishi, Yoshihiko

    1993-01-01

    In the field of mobile satellite communications, a system based on low-earth-orbit satellites (LEO-SAT's) such as the Iridium system has been proposed. The LEO-SAT system is able to offer mobile telecommunication services in high-latitude areas. Rain degradation, fading and shadowing are also expected to be decreased when the system is operated at a high elevation angle. Furthermore, the propagation delay generated in the LEO-SAT system is less pronounced than that in the geostationary orbit satellite (GEO-SAT) system and, in voice services, the effect of the delay is almost negligible. We proposed a concept of a broad-band mobile satellite communication system with LEO-SAT's and Optical ISL. In that system, a fixed L-band (1.6/1.5 GHz) multibeam is used to offer narrow band service to the mobile terminals in the entire area covered by a LEO-SAT and steerable Ka-band (30/20 GHz) spot beams are used for the wide band service. In this paper, we present results of a study of LEO-SAT microwave link between a satellite and a mobile terminal for a broad-band mobile satellite communication system. First, the results of link budget calculations are presented and the antennas mounted on satellites are shown. For a future mobile antenna technology, we also show digital beamforming (DBF) techniques. DBF, together with modulation and/or demodulation, is becoming a key technique for mobile antennas with advanced functions such as antenna pattern calibration, correction, and radio interference suppression. In this paper, efficient DBF techniques for transmitting and receiving are presented. Furthermore, an adaptive array antenna system suitable for this LEO-SAT is presented.

  11. Software defined radio (SDR) architecture for concurrent multi-satellite communications

    Science.gov (United States)

    Maheshwarappa, Mamatha R.

    SDRs have emerged as a viable approach for space communications over the last decade by delivering low-cost hardware and flexible software solutions. The flexibility introduced by the SDR concept not only allows the realisation of concurrent multiple standards on one platform, but also promises to ease the implementation of one communication standard on differing SDR platforms by signal porting. This technology would facilitate implementing reconfigurable nodes for parallel satellite reception in Mobile/Deployable Ground Segments and Distributed Satellite Systems (DSS) for amateur radio/university satellite operations. This work outlines the recent advances in embedded technologies that can enable new communication architectures for concurrent multi-satellite or satellite-to-ground missions where multi-link challenges are associated. This research proposes a novel concept to run advanced parallelised SDR back-end technologies in a Commercial-Off-The-Shelf (COTS) embedded system that can support multi-signal processing for multi-satellite scenarios simultaneously. The initial SDR implementation could support only one receiver chain due to system saturation. However, the design was optimised to facilitate multiple signals within the limited resources available on an embedded system at any given time. This was achieved by providing a VHDL solution to the existing Python and C/C++ programming languages along with parallelisation so as to accelerate performance whilst maintaining the flexibility. The improvement in the performance was validated at every stage through profiling. Various cases of concurrent multiple signals with different standards such as frequency (with Doppler effect) and symbol rates were simulated in order to validate the novel architecture proposed in this research. Also, the architecture allows the system to be reconfigurable by providing the opportunity to change the communication standards in soft real-time. The chosen COTS solution provides a

  12. Electromagnetic Modeling of the Propagation Characteristics of Satellite Communications Through Composite Precipitation Layers, Part1: Mathematical Formulation

    Directory of Open Access Journals (Sweden)

    H.M. Al-Rizzo

    2000-12-01

    Full Text Available A systematic and general formulation of a Propagation Simulation Program (PSP is developed for the coherent field of microwave and millimeter wave carrier signals traversing intermediate layered precipitation media, taking into account the random behavior of particle size, orientation, shape and concentration distributions.  Based on a rigorous solution of the volumetric multiple-scattering integral equations, the formalism offers the capability of treating the potential transmission impairments on satellite-earth links and radar remote sensing generated by composite atmospheric layers of precipitation in conjunction with the finite polarization isolation of dual-polarized transmitting and receiving antennas. A multi-layered formulation is employed which encompasses an ensemble of discrete particles comprising an arbitrary mixture of ice crystals, melting snow and raindrops that may exist simultaneously along satellite-earth communication paths.

  13. NASA satellite communications application research, phase 2 addendum. Efficient high power, solid state amplifier for EHF communications

    Science.gov (United States)

    Benet, James

    1994-01-01

    This document is an addendum to the NASA Satellite Communications Application Research (SCAR) Phase 2 Final Report, 'Efficient High Power, Solid State Amplifier for EHF Communications.' This report describes the work performed from 1 August 1993 to 11 March 1994, under contract number NASW-4513. During this reporting period an array of transistor amplifiers was repaired by replacing all MMIC amplifier chips. The amplifier array was then tested using three different feedhorn configurations. Descriptions, procedures, and results of this testing are presented in this report, and conclusions are drawn based on the test results obtained.

  14. Deep Charging Evaluation of Satellite Power and Communication System Components

    Science.gov (United States)

    Schneider, T. A.; Vaughn, J. A.; Chu, B.; Wong, F.; Gardiner, G.; Wright, K. H.; Phillips, B.

    2016-01-01

    Deep charging, in contrast to surface charging, focuses on electron penetration deep into insulating materials applied over conductors. A classic example of this scenario is an insulated wire. Deep charging can pose a threat to material integrity, and to sensitive electronics, when it gives rise to an electrostatic discharge or arc. With the advent of Electric Orbit Raising, which requires spiraling through Earth's radiation belts, satellites are subjected to high energy electron environments which they normally would not encounter. Beyond Earth orbit, missions to Jupiter and Saturn face deep charging concerns due to the high energy radiation environments. While predictions can be made about charging in insulating materials, it is difficult to extend those predictions to complicated geometries, such as the case of an insulating coating around a small wire, or a non-uniform silicone grouting on a bus bar. Therefore, to conclusively determine the susceptibility of a system to arcs from deep charging, experimental investigations must be carried out. This paper will describe the evaluation carried out by NASA's Marshall Space Flight Center on subscale flight-like samples developed by Space Systems/Loral, LLC. Specifically, deep charging evaluations of solar array wire coupons, a photovoltaic cell coupon, and a coaxial microwave transmission cable, will be discussed. The results of each evaluation will be benchmarked against control sample tests, as well as typical power system levels, to show no significant deep charging threat existed for this set of samples under the conditions tested.

  15. Rain Fade Compensation for Ka-Band Communications Satellites

    Science.gov (United States)

    Mitchell, W. Carl; Nguyen, Lan; Dissanayake, Asoka; Markey, Brian; Le, Anh

    1997-01-01

    This report provides a review and evaluation of rain fade measurement and compensation techniques for Ka-band satellite systems. This report includes a description of and cost estimates for performing three rain fade measurement and compensation experiments. The first experiment deals with rain fade measurement techniques while the second one covers the rain fade compensation techniques. The third experiment addresses a feedback flow control technique for the ABR service (for ATM-based traffic). The following conclusions were observed in this report; a sufficient system signal margin should be allocated for all carriers in a network, that is a fixed clear-sky margin should be typically in the range of 4-5 dB and should be more like 15 dB in the up link for moderate and heavy rain zones; to obtain a higher system margin it is desirable to combine the uplink power control technique with the technique that implements the source information rate and FEC code rate changes resulting in a 4-5 dB increase in the dynamic part of the system margin. The experiments would assess the feasibility of the fade measurements and compensation techniques, and ABR feedback control technique.

  16. Utilization of photovoltaic for broadband satellite communications in rural area of Thailand

    Science.gov (United States)

    Jinayim, Theerawut; Mungkung, Narong; Kasayapanand, Nat

    2013-06-01

    Electricity, Information and Communication Technologies (ICTs) are very important not only in urban areas but also in rural areas. To provide ICTs service in rural areas, sources of electricity and communication infrastructures must be implemented. Electricity is a major condition due to the fact that all electronic devices needed it in order to power on, so that it is impossible to operate any forms of ICTs in areas where the main national grid line is unavailable. Almost rural areas of Thailand where the main national grid line is unavailable have very good sunlight intensity. Photovoltaic is the most effective renewable energy technologies in those areas for meeting electricity needed in areas that are not connected to the main national grid line. In this paper, the efficiency utilization of photovoltaic as source of electricity for broadband satellite communication systems as well as social and economic impact and quality of life of people in rural areas of Thailand are presented. The results show that most rural communities would be able to universally access to the basic telecommunications services such as internet access and public telephone via satellite communication systems. However, in some field case study, broadband internet access via satellite communication may be unnecessary for some rural communities and the most exactly rural communities needed are electricity for household usage and battery charger.

  17. Networks systems and operations. [wideband communication techniques for data links with satellites

    Science.gov (United States)

    1975-01-01

    The application of wideband communication techniques for data links with satellites is discussed. A diagram of the demand assigned voice communications system is provided. The development of prototype integrated spacecraft paramps at S- and C-bands is described and the performance of space-qualified paramps is tabulated. The characteristics of a dual parabolic cylinder monopulse zoom antenna for use with the tracking and data relay satellite system (TDRSS) are analyzed. The development of a universally applicable transponder at S-band is reported. A block diagram of the major subassemblies of the S-band transponder is included. The technology aspects of network timing and synchronization of communication systems are to show the use of the Omega navigation system. The telemetry data compression system used during the Skylab program is evaluated.

  18. Communications satellites in the national and global health care information infrastructure: their role, impact, and issues

    Science.gov (United States)

    Zuzek, J. E.; Bhasin, K. B.

    1996-01-01

    Health care services delivered from a distance, known collectively as telemedicine, are being increasingly demonstrated on various transmission media. Telemedicine activities have included diagnosis by a doctor at a remote location, emergency and disaster medical assistance, medical education, and medical informatics. The ability of communications satellites to offer communication channels and bandwidth on demand, connectivity to mobile, remote and under served regions, and global access will afford them a critical role for telemedicine applications within the National and Global Information Infrastructure (NII/GII). The importance that communications satellites will have in telemedicine applications within the NII/GII the differences in requirements for NII vs. GII, the major issues such as interoperability, confidentiality, quality, availability, and costs, and preliminary conclusions for future usability based on the review of several recent trails at national and global levels are presented.

  19. Broadband and scalable mobile satellite communication system for future access networks

    Science.gov (United States)

    Ohata, Kohei; Kobayashi, Kiyoshi; Nakahira, Katsuya; Ueba, Masazumi

    2005-07-01

    Due to the recent market trends, NTT has begun research into next generation satellite communication systems, such as broadband and scalable mobile communication systems. One service application objective is to provide broadband Internet access for transportation systems, temporal broadband access networks and telemetries to remote areas. While these are niche markets the total amount of capacity should be significant. We set a 1-Gb/s total transmission capacity as our goal. Our key concern is the system cost, which means that the system should be unified system with diversified services and not tailored for each application. As satellites account for a large portion of the total system cost, we set the target satellite size as a small, one-ton class dry mass with a 2-kW class payload power. In addition to the payload power and weight, the mobile satellite's frequency band is extremely limited. Therefore, we need to develop innovative technologies that will reduce the weight and maximize spectrum and power efficiency. Another challenge is the need for the system to handle up to 50 dB and a wide data rate range of other applications. This paper describes the key communication system technologies; the frequency reuse strategy, multiplexing scheme, resource allocation scheme, and QoS management algorithm to ensure excellent spectrum efficiency and support a variety of services and quality requirements in the mobile environment.

  20. Satellite-based quantum communication terminal employing state-of-the-art technology

    Science.gov (United States)

    Pfennigbauer, Martin; Aspelmeyer, Markus; Leeb, Walter R.; Baister, Guy; Dreischer, Thomas; Jennewein, Thomas; Neckamm, Gregor; Perdigues, Josep M.; Weinfurter, Harald; Zeilinger, Anton

    2005-09-01

    Feature Issue on Optical Wireless Communications (OWC) We investigate the design and the accommodation of a quantum communication transceiver in an existing classical optical communication terminal on board a satellite. Operation from a low earth orbit (LEO) platform (e.g., the International Space Station) would allow transmission of single photons and pairs of entangled photons to ground stations and hence permit quantum communication applications such as quantum cryptography on a global scale. Integration of a source generating entangled photon pairs and single-photon detection into existing optical terminal designs is feasible. Even more, major subunits of the classical terminals such as those for pointing, acquisition, and tracking as well as those providing the required electronic, thermal, and structural backbone can be adapted so as to meet the quantum communication terminal needs.

  1. Defining a Communications Satellite Policy System for the 21st Century: A Model for a International Legal Framework and A New _Code of Conduct_

    Science.gov (United States)

    Pelton, Joseph N.

    1996-02-01

    This paper addresses the changing international communications environment and explores the key elements of a new policy framework for the 21st Century. It addresses the issues related to changing markets, trade considerations, standards, regulatory changes and international institutions and law. The most important aspects will related to new international policy and regulatory frameworks and in particular to a new international code of ethics and behavior in the field of satellite communications. A new communications satellite policy framework requires systematically addressing the following points: • Multi-lateral agreements at the nation state and the operating entity level • Systematic means to access both private and public capital • Meshing ITU regulations with regional and national policy guidelines including • landing rights" and national allocation procedures. • Systematic approach to local partnerships • Resolving the issue of the relative standing of various satellite systems (i.e. GEO, MEO, and LEO systems) • Resolving the rights, duties, and priorities of satellite facility providers versus types of service prviders. Beyond this policy framework and generalized legal infrastructure there is also another need. This is a need that arises from both increased globalism and competitive international markets. This is what might quite simply be called a "code of reasonable conduct:" To provide global and international communications services effectively and well in the 21st Century will require more than meeting minimum international legal requirements. A new "code of conduct" for global satellite communications will thus likely need to address: • Privacy and surveillance • Ethics of transborder data flow • Censorship and moral values • Cultural and linguistic sensitivity • Freedom of the press and respect for journalistic standards As expanding global information and telecommunications systems grow and impact every aspect of modern

  2. Integrating small satellite communication in an autonomous vehicle network: A case for oceanography

    Science.gov (United States)

    Guerra, André G. C.; Ferreira, António Sérgio; Costa, Maria; Nodar-López, Diego; Aguado Agelet, Fernando

    2018-04-01

    Small satellites and autonomous vehicles have greatly evolved in the last few decades. Hundreds of small satellites have been launched with increasing functionalities, in the last few years. Likewise, numerous autonomous vehicles have been built, with decreasing costs and form-factor payloads. Here we focus on combining these two multifaceted assets in an incremental way, with an ultimate goal of alleviating the logistical expenses in remote oceanographic operations. The first goal is to create a highly reliable and constantly available communication link for a network of autonomous vehicles, taking advantage of the small satellite lower cost, with respect to conventional spacecraft, and its higher flexibility. We have developed a test platform as a proving ground for this network, by integrating a satellite software defined radio on an unmanned air vehicle, creating a system of systems, and several tests have been run successfully, over land. As soon as the satellite is fully operational, we will start to move towards a cooperative network of autonomous vehicles and small satellites, with application in maritime operations, both in-situ and remote sensing.

  3. Deviations in CBERS-4 Satellite Direction Components From The Electromagnetic Disturbance of Communication Antennas

    Science.gov (United States)

    Heilmann, A.; Fernandes, C.

    2017-10-01

    The CBERS-4 is a low Earth orbit satellite, with a set of antennas S-band/UHF for communication almost omni-direcional. For the electromagnetic radiation from transmission antennas, was developed a model of electromagnetic disturbance considering the antennas theory and the laws of the conservation energy-momentum. Was propagated the orbit of the CBERS-4 satellite considering your state vector from the March 14, 2016, at 11h 14m 15.23s using the equation of motion in the form of cartesian components. From the state vector of the CBERS-4 satellite was possible to propagate the orbit for different periods, without disturbance (considering just the problem of two bodies) and with a disturbance of electromagnetic origin. The model of reaction of electromagnetic acceleration on the satellite depends on only the type of antenna. Quadrifilar and parabolic propeller antennas were considered in this paper. Using the equation of motion of the satellite based on the method of Runge-Kutta of fourth and fifth degree, the effect disturber this modeling was applied on the CBERS-4 considering the mass of satellite, characteristics of antenna, power irradiated and gain maximum of antenna. The final analysis discusses the values of components in the direction (radial, cross and normal) and the coordinates X-Y-Z considering the case disturbed to both antennas.

  4. TWT design requirements for 30/20 GHz digital communications' satellite

    Science.gov (United States)

    Stankiewicz, N.; Anzic, G.

    1979-01-01

    The rapid growth of communication traffic (voice, data, and video) requires the development of additional frequency bands before the 1990's. The frequencies currently in use for satellite communications at 6/4 GHz are crowded and demands for 14/12 GHz systems are increasing. Projections are that these bands will be filled to capacity by the late 1980's. The next higher frequency band allocated for satellite communications is at 30/20 GHz. For interrelated reasons of efficiency, power level, and system reliability criteria, a candidate for the downlink amplifier in a 30/20 GHz communications' satellite is a dual mode traveling wave tube (TWT) equipped with a highly efficient depressed collector. A summary is given of the analyses which determine the TWT design requirements. The overall efficiency of such a tube is then inferred from a parametric study and from experimental data on multistaged depressed collectors. The expected TWT efficiency at 4 dB below output saturation is 24 percent in the high mode and 22 percent in the low mode.

  5. Optimization of communication network topology for navigation sharing among distributed satellites

    Science.gov (United States)

    Dang, Zhaohui; Zhang, Yulin

    2013-01-01

    Navigation sharing among distributed satellites is quite important for coordinated motion and collision avoidance. This paper proposes optimization methods of the communication network topology to achieve navigation sharing. The whole communication network constructing by inter-satellite links are considered as a topology graph. The aim of this paper is to find the communication network topology with minimum communication connections' number (MCCN) in different conditions. It has found that the communication capacity and the number of channels are two key parameters affecting the results. The model of MCCN topology for navigation sharing is established and corresponding method is designed. Two main scenarios, viz., homogeneous case and heterogeneous case, are considered. For the homogeneous case where each member has the same communication capacity, it designs a construction method (Algorithm 1) to find the MCCN topology. For the heterogeneous case, it introduces a modified genetic algorithm (Algorithm 2) to find the MCCN topology. When considering the fact that the number of channels is limited, the Algorithm 2 is further modified by adding a penalized term in the fitness function. The effectiveness of these algorithms is all proved in theoretical. Three examples are further tested to illustrate the methods developed in this paper.

  6. Intuitive Tools for the Design and Analysis of Communication Payloads for Satellites

    Science.gov (United States)

    Culver, Michael R.; Soong, Christine; Warner, Joseph D.

    2014-01-01

    In an effort to make future communications satellite payload design more efficient and accessible, two tools were created with intuitive graphical user interfaces (GUIs). The first tool allows payload designers to graphically design their payload by using simple drag and drop of payload components onto a design area within the program. Information about each picked component is pulled from a database of common space-qualified communication components sold by commerical companies. Once a design is completed, various reports can be generated, such as the Master Equipment List. The second tool is a link budget calculator designed specifically for ease of use. Other features of this tool include being able to access a database of NASA ground based apertures for near Earth and Deep Space communication, the Tracking and Data Relay Satellite System (TDRSS) base apertures, and information about the solar system relevant to link budget calculations. The link budget tool allows for over 50 different combinations of user inputs, eliminating the need for multiple spreadsheets and the user errors associated with using them. Both of the aforementioned tools increase the productivity of space communication systems designers, and have the colloquial latitude to allow non-communication experts to design preliminary communication payloads.

  7. Multiple access chaotic digital communication based on generalized synchronization

    International Nuclear Information System (INIS)

    Lu Junguo

    2005-01-01

    A novel method for multiple access chaotic digital communication based on the concept of chaos generalized synchronization and the on-line least square method is proposed. This method can be used for transmitting multiple digital information signals concurrently. We illustrate the method using a Lorenz system driving a Chua's circuit and then examine the robustness of the proposed method with respect to noise in communication channel

  8. Multiple wavelength spectral system simulating background light noise environment in satellite laser communications

    Science.gov (United States)

    Lu, Wei; Sun, Jianfeng; Hou, Peipei; Xu, Qian; Xi, Yueli; Zhou, Yu; Zhu, Funan; Liu, Liren

    2017-08-01

    Performance of satellite laser communications between GEO and LEO satellites can be influenced by background light noise appeared in the field of view due to sunlight or planets and some comets. Such influences should be studied on the ground testing platform before the space application. In this paper, we introduce a simulator that can simulate the real case of background light noise in space environment during the data talking via laser beam between two lonely satellites. This simulator can not only simulate the effect of multi-wavelength spectrum, but also the effects of adjustable angles of field-of-view, large range of adjustable optical power and adjustable deflection speeds of light noise in space environment. We integrate these functions into a device with small and compact size for easily mobile use. Software control function is also achieved via personal computer to adjust these functions arbitrarily. Keywords:

  9. Millimeter wave propagation modeling of inhomogeneous rain media for satellite communications systems

    Science.gov (United States)

    Persinger, R. R.; Stutzman, W. L.

    1978-01-01

    A theoretical propagation model that represents the scattering properties of an inhomogeneous rain often found on a satellite communications link is presented. The model includes the scattering effects of an arbitrary distribution of particle type (rain or ice), particle shape, particle size, and particle orientation within a given rain cell. An associated rain propagation prediction program predicts attenuation, isolation and phase shift as a function of ground rain rate. A frequency independent synthetic storm algorithm is presented that models nonuniform rain rates present on a satellite link. Antenna effects are included along with a discussion of rain reciprocity. The model is verified using the latest available multiple frequency data from the CTS and COMSTAR satellites. The data covers a wide range of frequencies, elevation angles, and ground site locations.

  10. Exploring the boundaries of quantum mechanics: advances in satellite quantum communications.

    Science.gov (United States)

    Agnesi, Costantino; Vedovato, Francesco; Schiavon, Matteo; Dequal, Daniele; Calderaro, Luca; Tomasin, Marco; Marangon, Davide G; Stanco, Andrea; Luceri, Vincenza; Bianco, Giuseppe; Vallone, Giuseppe; Villoresi, Paolo

    2018-07-13

    Recent interest in quantum communications has stimulated great technological progress in satellite quantum technologies. These advances have rendered the aforesaid technologies mature enough to support the realization of experiments that test the foundations of quantum theory at unprecedented scales and in the unexplored space environment. Such experiments, in fact, could explore the boundaries of quantum theory and may provide new insights to investigate phenomena where gravity affects quantum objects. Here, we review recent results in satellite quantum communications and discuss possible phenomena that could be observable with current technologies. Furthermore, stressing the fact that space represents an incredible resource to realize new experiments aimed at highlighting some physical effects, we challenge the community to propose new experiments that unveil the interplay between quantum mechanics and gravity that could be realizable in the near future.This article is part of a discussion meeting issue 'Foundations of quantum mechanics and their impact on contemporary society'. © 2018 The Author(s).

  11. Intersatellite Link (ISL) application to commercial communications satellites. Volume 2: Technical final report

    Science.gov (United States)

    Young, S. Lee

    1987-01-01

    Intersatellite Link (ISL) applications can improve and expand communication satellite services in a number of ways. As the demand for orbital slots within prime regions of the geostationary arc increases, attention is being focused on ISLs as a method to utilize this resource more efficiently and circumvent saturation. Various GEO-to-GEO applications were determined that provide potential benefits over existing communication systems. A set of criteria was developed to assess the potential applications. Intersatellite link models, network system architectures, and payload configurations were developed. For each of the chosen ISL applications, ISL versus non-ISL satellite systems architectures were derived. Both microwave and optical ISL implementation approaches were evaluated for payload sizing and cost analysis. The technological availability for ISL implementations was assessed. Critical subsystems technology areas were identified, and an estamate of the schedule and cost to advance the technology to the requiered state of readiness was made.

  12. Issues for the integration of satellite and terrestrial cellular networks for mobile communications

    Science.gov (United States)

    Delre, Enrico; Mistretta, Ignazio; Dellipriscoli, Francesco; Settimo, Franco

    1991-01-01

    Satellite and terrestrial cellular systems naturally complement each other for land mobile communications, even though present systems have been developed independently. The main advantages of the integrated system are a faster wide area coverage, a better management of overloading traffic conditions, an extension to geographical areas not covered by the terrestrial network and, in perspective, the provision of only one integrated system for all mobile communications (land, aeronautical, and maritime). To achieve these goals, as far as possible the same protocols of the terrestrial network should be used also for the satellite network. Discussed here are the main issues arising from the requirements of the main integrated system. Some results are illustrated, and possible future improvements due to technical solutions are presented.

  13. Design of an anti-Rician-fading modem for mobile satellite communication systems

    Science.gov (United States)

    Kojima, Toshiharu; Ishizu, Fumio; Miyake, Makoto; Murakami, Keishi; Fujino, Tadashi

    1995-01-01

    To design a demodulator applicable to mobile satellite communication systems using differential phase shift keying modulation, we have developed key technologies including an anti-Rician-fading demodulation scheme, an initial acquisition scheme, automatic gain control (AGC), automatic frequency control (AFC), and bit timing recovery (BTR). Using these technologies, we have developed one-chip digital signal processor (DSP) modem for mobile terminal, which is compact, of light weight, and of low power consumption. Results of performance test show that the developed DSP modem achieves good performance in terms of bit error ratio in mobile satellite communication environment, i.e., Rician fading channel. It is also shown that the initial acquisition scheme acquires received signal rapidly even if the carrier-to-noise power ratio (CNR) of the received signal is considerably low.

  14. The impact of customer-contractor interactions on spacecraft innovation: Insights from communication satellite history

    Science.gov (United States)

    Szajnfarber, Zoe; Stringfellow, Margaret V.; Weigel, Annalisa L.

    2010-11-01

    This paper captures a first detailed attempt to quantitatively analyze the innovation history of the space sector. Building on a communication satellite innovation metric and a spacecraft innovation framework developed as part of an ongoing project, this paper presents a preliminary model of global communication satellite innovation. In addition to innovation being a function of the rate of performance normalized by price, innovation was found to be strongly influenced by characteristics of the customer-contractor contractual relationship. Specifically, Department of Defense contracts tend to result in a lower level of innovation on average as compared to other customers. Also, particular customer-contractor pairs perform differently and exhibit a second order relationship in time.

  15. R&D of a Next Generation LEO System for Global Multimedia Mobile Satellite Communications

    Science.gov (United States)

    Morikawa, E.; Motoyoshi, S.; Koyama, Y.; Suzuki, R.; Yasuda, Y.

    2002-01-01

    Next-generation LEO System Research Center (NeLS) was formed in the end of 1997 as a research group under the Telecommunications Advancement Organization of Japan, in cooperation with the telecommunications operators, manufacturers, universities and governmental research organization. The aim of this project is to develop new technology for global multimedia mobile satellite communications services with a user data rate around 2Mbps for handy terminals. component of the IMT-2000, and the second generation of the big-LEO systems. In prosecuting this project, two-phase approach, phase 1 and phase 2, is considered. Phase 1 is the system definition and development of key technologies. In Phase 2, we plan to verify the developed technology in Phase 1 on space. From this year we shifted the stage to Phase 2, and are now developing the prototype of on-board communication systems for flight tests, which will be planed at around 2006. The satellite altitude is assumed to be 1200 km in order to reduce the number of satellites, to avoid the Van Allen radiation belts and to increase the minimum elevation angle. Ten of the circular orbits with 55 degree of inclination are selected to cover the earth surface from -70 to 70 degree in latitude. 12 satellites are positioned at regular intervals in each orbit. In this case, the minimum elevation angle from the user terminal can be keep more than 20 degree for the visibility of the satellite, and 15 degree for simultaneous visibility of two satellites. Then, NeLS Research Center was focusing on the development of key technologies as the phase 1 project. Four kinds of key technologies; DBF satellite antenna, optical inter-satellite link system, satellite network technology with on-board ATM switch and variable rate modulation were selected. Satellite Antenna Technology: Development of on-board direct radiating active phased array antenna with digital beam forming technology would be one of the most important breakthroughs for the

  16. Data manage and communication of lunar orbital X-ray imaging analyzer in CE-1 satellite

    International Nuclear Information System (INIS)

    Wang Jinzhou; Wang Huanyu; Zhang Chengmo; Liang Xiaohua; Gao Min; CaoXuelei; Zhang Jiayu; Peng Wenxi; Cui Xingzhu; Xu Yupeng; Zhang Yongjie

    2006-01-01

    We present the software design for data management and communication software designed for the Lunar Orbital X-ray Imaging Analyzer in CE-1 Satellite. The software uses the appropriate format to assemble science data package and appropriate command respond mode, realizes the data transferring tasks through the 1553B bus on time, event though the channel bandwidth is under the limited. Also, the memory distribution and management of LOXIA (remote terminal) that fitted the communication with BC(Bus Controller) was introduced. Furthermore, for the spatial application, the security and reliability of software are emphasized. (authors)

  17. Advanced architectures and the required technologies for next-generation communications satellite systems

    Science.gov (United States)

    Arnold, Ray; Naderi, F. Michael

    1988-01-01

    The hardware requirements for multibeam operation and onboard data processing and switching on future communication satellites are reviewed. Topics addressed include multiple-beam antennas, frequency-addressable beams, baseband vs IF switching, FDM/TDMA systems, and bulk demodulators. The proposed use of these technologies in the NASA ACTS, Italsat, and the Japanese ETS-VI is discussed in detail and illustrated with extensive diagrams, maps, drawings, and tables of projected performance data.

  18. Critical Comments on the General Model of Instructional Communication

    Science.gov (United States)

    Walton, Justin D.

    2014-01-01

    This essay presents a critical commentary on McCroskey et al.'s (2004) general model of instructional communication. In particular, five points are examined which make explicit and problematize the meta-theoretical assumptions of the model. Comments call attention to the limitations of the model and argue for a broader approach to…

  19. Communicating fatigue in general practice and the role of gender

    NARCIS (Netherlands)

    Meeuwesen, L.; Bensing, J.; Brink-Muinen, A. van den

    2002-01-01

    The aim of this study has been to obtain more insight into the health condition of fatigued patients, their expectations when visiting the general practitioner (GP), the way they communicate, and possible gender differences. Data consisted of 579 patient questionnaires and 440 video-observations of

  20. A Strategic Analysis of Commercial Satellite communications Enterprises and their Role for the Warfighter of the Future

    National Research Council Canada - National Science Library

    Gonder, Richard

    1998-01-01

    .... After initially setting the baseline, the paper will discuss the ability of the exploding commercial satellite communications market to meet some, if not most of the uniquely military requirements (the pros...

  1. Optimization of Joint Power and Bandwidth Allocation in Multi-Spot-Beam Satellite Communication Systems

    Directory of Open Access Journals (Sweden)

    Heng Wang

    2014-01-01

    Full Text Available Multi-spot-beam technique has been widely applied in modern satellite communication systems. However, the satellite power and bandwidth resources in a multi-spot-beam satellite communication system are scarce and expensive; it is urgent to utilize the resources efficiently. To this end, dynamically allocating the power and bandwidth is an available way. This paper initially formulates the problem of resource joint allocation as a convex optimization problem, taking into account a compromise between the maximum total system capacity and the fairness among the spot beams. A joint bandwidth and power allocation iterative algorithm based on duality theory is then proposed to obtain the optimal solution of this optimization problem. Compared with the existing separate bandwidth or power optimal allocation algorithms, it is shown that the joint allocation algorithm improves both the total system capacity and the fairness among spot beams. Moreover, it is easy to be implemented in practice, as the computational complexity of the proposed algorithm is linear with the number of spot beams.

  2. Quantum communication for satellite-to-ground networks with partially entangled states

    International Nuclear Information System (INIS)

    Chen Na; Quan Dong-Xiao; Pei Chang-Xing; Yang-Hong

    2015-01-01

    To realize practical wide-area quantum communication, a satellite-to-ground network with partially entangled states is developed in this paper. For efficiency and security reasons, the existing method of quantum communication in distributed wireless quantum networks with partially entangled states cannot be applied directly to the proposed quantum network. Based on this point, an efficient and secure quantum communication scheme with partially entangled states is presented. In our scheme, the source node performs teleportation only after an end-to-end entangled state has been established by entanglement swapping with partially entangled states. Thus, the security of quantum communication is guaranteed. The destination node recovers the transmitted quantum bit with the help of an auxiliary quantum bit and specially defined unitary matrices. Detailed calculations and simulation analyses show that the probability of successfully transferring a quantum bit in the presented scheme is high. In addition, the auxiliary quantum bit provides a heralded mechanism for successful communication. Based on the critical components that are presented in this article an efficient, secure, and practical wide-area quantum communication can be achieved. (paper)

  3. Risk communication between general practitioners and patients with hypercholesterolemia

    DEFF Research Database (Denmark)

    Hansen, Bo; Kirkegaard, Pia; Lauritzen, Torsten

      Purpose: It is important that the general practitioners (GPs) are able to intervene to reduce risk of disease. One of the key points in doing so is effective risk communication that decreases uncertainty about choice of treatment and gives the patients a greater understanding of benefits......, and psychological well-being.    Methods: 40 GPs receive training in risk communication. Each GP selects 7 patients with elevated cholesterol. These patients are informed about the opportunity to receive preventive pharmacological treatment. Another 280 patients receive the same opportunity from 40 GPs without...... their psychological well-being.   Conclusion: This randomised intervention study will produce new knowledge about the effect of training GPs in risk communication....

  4. On Scott-Phillips' General Account of Communication.

    Science.gov (United States)

    Planer, Ronald J

    2017-12-01

    The purpose of this paper is to critically engage with a recent attempt by Thom Scott-Phillips to offer a general account of communication. As a general account, it is intended to apply equally well to both non-human and human interactions which are prima facie communicative in character. However, so far, Scott-Phillips has provided little detail regarding how his account is supposed to apply to the latter set of cases. After presenting what I take to be the most plausible way of filling in those details, I argue that his account would appear to be too narrow: it (minimally) fails to capture a range of human interactions which strike us as instances of communication. To wit, these are cases in which some but not all of the information an act is designed to convey to a reactor actually reaches that reactor. An alternative account incorporating Scott-Phillips' main insights is then sketched, and it is suggested that this account, or something like it, would accommodate the full range of non-human and human interactions that are intuitively communicative.

  5. Design and Evaluation of 10-Gbps Inter-satellite Optical Wireless Communication Link for Improved Performance

    Science.gov (United States)

    Gupta, Amit; Nagpal, Shaina

    2017-05-01

    Inter-satellite optical wireless communication (IsOWC) systems can be chosen over existing microwave satellite systems for deploying in space in the future due to their high bandwidth, small size, light weight, low power and low cost. However, the IsOWC system suffers from various attenuations due to weather conditions, turbulence or scintillations which limit its performance and decreases its availability. So, in order to improve the performance, IsOWC system using directly modulated laser source is proposed in this work. The system is designed and evaluated to be suitable for high data rate transmissions up to 10 Gbps. The performance of the system is investigated in order to reduce the cost and complexity of link and improving the quality of information signal. Further the proposed IsOWC system is analysed using BER analyser, power meter and oscilloscope Visualizer.

  6. Description and Simulation of a Fast Packet Switch Architecture for Communication Satellites

    Science.gov (United States)

    Quintana, Jorge A.; Lizanich, Paul J.

    1995-01-01

    The NASA Lewis Research Center has been developing the architecture for a multichannel communications signal processing satellite (MCSPS) as part of a flexible, low-cost meshed-VSAT (very small aperture terminal) network. The MCSPS architecture is based on a multifrequency, time-division-multiple-access (MF-TDMA) uplink and a time-division multiplex (TDM) downlink. There are eight uplink MF-TDMA beams, and eight downlink TDM beams, with eight downlink dwells per beam. The information-switching processor, which decodes, stores, and transmits each packet of user data to the appropriate downlink dwell onboard the satellite, has been fully described by using VHSIC (Very High Speed Integrated-Circuit) Hardware Description Language (VHDL). This VHDL code, which was developed in-house to simulate the information switching processor, showed that the architecture is both feasible and viable. This paper describes a shared-memory-per-beam architecture, its VHDL implementation, and the simulation efforts.

  7. Mitigating Aviation Communication and Satellite Orbit Operations Surprises from Adverse Space Weather

    Science.gov (United States)

    Tobiska, W. Kent

    2008-01-01

    Adverse space weather affects operational activities in aviation and satellite systems. For example, large solar flares create highly variable enhanced neutral atmosphere and ionosphere electron density regions. These regions impact aviation communication frequencies as well as precision orbit determination. The natural space environment, with its dynamic space weather variability, is additionally changed by human activity. The increase in orbital debris in low Earth orbit (LEO), combined with lower atmosphere CO2 that rises into the lower thermosphere and causes increased cooling that results in increased debris lifetime, adds to the environmental hazards of navigating in near-Earth space. This is at a time when commercial space endeavors are posed to begin more missions to LEO during the rise of the solar activity cycle toward the next maximum (2012). For satellite and aviation operators, adverse space weather results in greater expenses for orbit management, more communication outages or aviation and ground-based high frequency radio used, and an inability to effectively plan missions or service customers with space-based communication, imagery, and data transferal during time-critical activities. Examples of some revenue-impacting conditions and solutions for mitigating adverse space weather are offered.

  8. Proportional fair scheduling algorithm based on traffic in satellite communication system

    Science.gov (United States)

    Pan, Cheng-Sheng; Sui, Shi-Long; Liu, Chun-ling; Shi, Yu-Xin

    2018-02-01

    In the satellite communication network system, in order to solve the problem of low system capacity and user fairness in multi-user access to satellite communication network in the downlink, combined with the characteristics of user data service, an algorithm study on throughput capacity and user fairness scheduling is proposed - Proportional Fairness Algorithm Based on Traffic(B-PF). The algorithm is improved on the basis of the proportional fairness algorithm in the wireless communication system, taking into account the user channel condition and caching traffic information. The user outgoing traffic is considered as the adjustment factor of the scheduling priority and presents the concept of traffic satisfaction. Firstly,the algorithm calculates the priority of the user according to the scheduling algorithm and dispatches the users with the highest priority. Secondly, when a scheduled user is the business satisfied user, the system dispatches the next priority user. The simulation results show that compared with the PF algorithm, B-PF can improve the system throughput, the business satisfaction and fairness.

  9. Link establishment criterion and topology optimization for hybrid GPS satellite communications with laser crosslinks

    Science.gov (United States)

    Li, Lun; Wei, Sixiao; Tian, Xin; Hsieh, Li-Tse; Chen, Zhijiang; Pham, Khanh; Lyke, James; Chen, Genshe

    2018-05-01

    In the current global positioning system (GPS), the reliability of information transmissions can be enhanced with the aid of inter-satellite links (ISLs) or crosslinks between satellites. Instead of only using conventional radio frequency (RF) crosslinks, the laser crosslinks provide an option to significantly increase the data throughput. The connectivity and robustness of ISL are needed for analysis, especially for GPS constellations with laser crosslinks. In this paper, we first propose a hybrid GPS communication architecture in which uplinks and downlinks are established via RF signals and crosslinks are established via laser links. Then, we design an optical crosslink assignment criteria considering the practical optical communication factors such as optical line- of-sight (LOS) range, link distance, and angular velocity, etc. After that, to further improve the rationality of establishing crosslinks, a topology control algorithm is formulated to optimize GPS crosslink networks at both physical and network layers. The RF transmission features for uplink and downlink and optical transmission features for crosslinks are taken into account as constraints for the optimization problem. Finally, the proposed link establishment criteria are implemented for GPS communication with optical crosslinks. The designs of this paper provide a potential crosslink establishment and topology control algorithm for the next generation GPS.

  10. MATLAB implementation of satellite positioning error overbounding by generalized Pareto distribution

    Science.gov (United States)

    Ahmad, Khairol Amali; Ahmad, Shahril; Hashim, Fakroul Ridzuan

    2018-02-01

    In the satellite navigation community, error overbound has been implemented in the process of integrity monitoring. In this work, MATLAB programming is used to implement the overbounding of satellite positioning error CDF. Using a trajectory of reference, the horizontal position errors (HPE) are computed and its non-parametric distribution function is given by the empirical Cumulative Distribution Function (ECDF). According to the results, these errors have a heavy-tailed distribution. Sınce the ECDF of the HPE in urban environment is not Gaussian distributed, the ECDF is overbound with the CDF of the generalized Pareto distribution (GPD).

  11. An assessment of the status and trends in satellite communications 1986-2000: An information document prepared for the Communications Subcommittee of the Space Applications Advisory Committee

    Science.gov (United States)

    Poley, W. A.; Stevens, G. H.; Stevenson, S. M.; Lekan, J.; Arth, C. H.; Hollansworth, J. E.; Miller, E. F.

    1986-01-01

    This is a response to a Space Applications Advisory Committee (SAAC) request for information about the status and trends in satellite communications, to be used to support efforts to conceive and recommend long range goals for NASA communications activities. Included in this document are assessments of: (1) the outlook for satellite communications, including current applications, potential future applications, and impact of the changing environment such as optical fiber networks, the Integrated Services Digital Network (ISDN) standard, and the rapidly growing market for Very Small Aperture Terminals (VSAT); (2) the restrictions imposed by our limited spectrum resource; and (3) technology needs indicated by future trends. Potential future systems discussed include: large powerful satellites for providing personal communications; VSAT compatible satellites with onboard switching and having voice capability; large satellites which offer a pervasive T1 network service (primarily for video-phone); and large geostationary communications facilities which support common use by several carriers. Also, discussion is included of NASA particular needs and possible future systems. Based on the mentioned system concepts, specific technology recommendations are provided for the time frames of now - 1993, 1994 - 2000, and 2000 - 2010.

  12. Trellis coding with Continuous Phase Modulation (CPM) for satellite-based land-mobile communications

    Science.gov (United States)

    1989-01-01

    This volume of the final report summarizes the results of our studies on the satellite-based mobile communications project. It includes: a detailed analysis, design, and simulations of trellis coded, full/partial response CPM signals with/without interleaving over various Rician fading channels; analysis and simulation of computational cutoff rates for coherent, noncoherent, and differential detection of CPM signals; optimization of the complete transmission system; analysis and simulation of power spectrum of the CPM signals; design and development of a class of Doppler frequency shift estimators; design and development of a symbol timing recovery circuit; and breadboard implementation of the transmission system. Studies prove the suitability of the CPM system for mobile communications.

  13. Practices in communicating technical issues to the general public

    International Nuclear Information System (INIS)

    Drabova, D.; Storey, P.

    2006-01-01

    The conclusions and recommendations of this session can be summarized this way. - Basic goal for the regulator is to protect the public and communication is a must to fully achieve this goal. - Regulator should become the prime source of information to the public and the media, regulator should base its actions upon values of competence, independence, transparency and stringency. - Set up of a Information and Communication Policy will help for consistency and efficiency. Policy will include setting goals, strategies, organisational aspects, procedures, and tools. Practices should be developed in accordance with local culture. - Challenges will consider transparency, public involvement and consultation with the stakeholders. - Practices will include in general: - Interactions with the media like press releases, news conferences, media workshops. Printed materials from plant periodical status reports, to periodical and annual reports and specific reports. Audio-visual materials. Use of radio and TV. Web site and electronic mail. - Method chosen depends on the targeted audience and the relevance of the topic. - Messages should be clearly understandable. Do not dehumanize the message by making it technically unintelligible. - Two excellent examples presented. How local culture and social characteristics were taken into account in designing and implementing plans is key for success. - Municipalities are to be considered as front line stakeholders. - Communicators role is relevant to meet regulatory needs. Good collaboration between communicators and technical staff produces benefits for the nuclear regulator and the public. (authors)

  14. Bandwidth-Efficient Communication through 225 MHz Ka-band Relay Satellite Channel

    Science.gov (United States)

    Downey, Joseph; Downey, James; Reinhart, Richard C.; Evans, Michael Alan; Mortensen, Dale John

    2016-01-01

    The communications and navigation space infrastructure of the National Aeronautics and Space Administration (NASA) consists of a constellation of relay satellites (called Tracking and Data Relay Satellites (TDRS)) and a global set of ground stations to receive and deliver data to researchers around the world from mission spacecraft throughout the solar system. Planning is underway to enhance and transform the infrastructure over the coming decade. Key to the upgrade will be the simultaneous and efficient use of relay transponders to minimize cost and operations while supporting science and exploration spacecraft. Efficient use of transponders necessitates bandwidth efficient communications to best use and maximize data throughput within the allocated spectrum. Experiments conducted with NASA's Space Communication and Navigation (SCaN) Testbed on the International Space Station provides a unique opportunity to evaluate advanced communication techniques, such as bandwidth-efficient modulations, in an operational flight system. Demonstrations of these new techniques in realistic flight conditions provides critical experience and reduces the risk of using these techniques in future missions. Efficient use of spectrum is enabled by using high-order modulations coupled with efficient forward error correction codes. This paper presents a high-rate, bandwidth-efficient waveform operating over the 225 MHz Ka-band service of the TDRS System (TDRSS). The testing explores the application of Gaussian Minimum Shift Keying (GMSK), 248-phase shift keying (PSK) and 1632- amplitude PSK (APSK) providing over three bits-per-second-per-Hertz (3 bsHz) modulation combined with various LDPC encoding rates to maximize throughput. With a symbol rate of 200 Mbaud, coded data rates of 1000 Mbps were tested in the laboratory and up to 800 Mbps over the TDRS 225 MHz channel. This paper will present on the high-rate waveform design, channel characteristics, performance results, compensation

  15. Bandwidth-Efficient Communication through 225 MHz Ka-band Relay Satellite Channel

    Science.gov (United States)

    Downey, Joseph A.; Downey, James M.; Reinhart, Richard C.; Evans, Michael A.; Mortensen, Dale J.

    2016-01-01

    The communications and navigation space infrastructure of the National Aeronautics and Space Administration (NASA) consists of a constellation of relay satellites (called Tracking and Data Relay Satellites (TDRS)) and a global set of ground stations to receive and deliver data to researchers around the world from mission spacecraft throughout the solar system. Planning is underway to enhance and transform the infrastructure over the coming decade. Key to the upgrade will be the simultaneous and efficient use of relay transponders to minimize cost and operations while supporting science and exploration spacecraft. Efficient use of transponders necessitates bandwidth efficient communications to best use and maximize data throughput within the allocated spectrum. Experiments conducted with NASA's Space Communication and Navigation (SCaN) Testbed on the International Space Station provides a unique opportunity to evaluate advanced communication techniques, such as bandwidth-efficient modulations, in an operational flight system. Demonstrations of these new techniques in realistic flight conditions provides critical experience and reduces the risk of using these techniques in future missions. Efficient use of spectrum is enabled by using high-order modulations coupled with efficient forward error correction codes. This paper presents a high-rate, bandwidth-efficient waveform operating over the 225 MHz Ka-band service of the TDRS System (TDRSS). The testing explores the application of Gaussian Minimum Shift Keying (GMSK), 2/4/8-phase shift keying (PSK) and 16/32- amplitude PSK (APSK) providing over three bits-per-second-per-Hertz (3 b/s/Hz) modulation combined with various LDPC encoding rates to maximize through- put. With a symbol rate of 200 M-band, coded data rates of 1000 Mbps were tested in the laboratory and up to 800 Mbps over the TDRS 225 MHz channel. This paper will present on the high-rate waveform design, channel characteristics, performance results

  16. Prediction of the Sun-Glint Locations for the Communication, Ocean and Meteorological Satellite

    Directory of Open Access Journals (Sweden)

    Jae-Ik Park

    2005-09-01

    Full Text Available For the Communication, Ocean and Meteorological Satellite (COMS which will be launched in 2008, an algorithm for finding the precise location of the sun-glint point on the ocean surface is studied. The precise locations of the sun-glint are estimated by considering azimuth and elevation angles of Sun-satellite-Earth geometric position and the law of reflection. The obtained nonlinear equations are solved by using the Newton-Raphson method. As a result, when COMS is located at 116.2°E or 128.2°E longitude, the sun-glint covers region of ±10° (N-S latitude and 80-150° (E-W longitude. The diurnal path of the sun-glint in the southern hemisphere is curved towards the North Pole, and the path in the northern hemisphere is forwards the south pole. The algorithm presented in this paper can be applied to predict the precise location of sun-glint region in any other geostationary satellites.

  17. Power attenuation characteristics as switch-over criterion in personal satellite mobile communications

    Science.gov (United States)

    Castro, Jonathan P.

    1993-01-01

    A third generation mobile system intends to support communications in all environments (i.e., outdoors, indoors at home or office and when moving). This system will integrate services that are now available in architectures such as cellular, cordless, mobile data networks, paging, including satellite services to rural areas. One way through which service integration will be made possible is by supporting a hierarchical cellular structure based on umbrella cells, macro cells, micro and pico cells. In this type of structure, satellites are part of the giant umbrella cells allowing continuous global coverage, the other cells belong to cities, neighborhoods, and buildings respectively. This does not necessarily imply that network operation of terrestrial and satellite segments interconnect to enable roaming and spectrum sharing. However, the cell concept does imply hand-off between different cell types, which may involve change of frequency. Within this propsective, the present work uses power attenuation characteristics to determine a dynamic criterion that allows smooth transition from space to terrestrial networks. The analysis includes a hybrid channel that combines Rician, Raleigh and Log Normal fading characteristics.

  18. Aerosol indirect effects -- general circulation model intercomparison and evaluation with satellite data

    Energy Technology Data Exchange (ETDEWEB)

    Quaas, Johannes; Ming, Yi; Menon, Surabi; Takemura, Toshihiko; Wang, Minghuai; Penner, Joyce E.; Gettelman, Andrew; Lohmann, Ulrike; Bellouin, Nicolas; Boucher, Olivier; Sayer, Andrew M.; Thomas, Gareth E.; McComiskey, Allison; Feingold, Graham; Hoose, Corinna; Kristjansson, Jon Egill; Liu, Xiaohong; Balkanski, Yves; Donner, Leo J.; Ginoux, Paul A.; Stier, Philip; Feichter, Johann; Sednev, Igor; Bauer, Susanne E.; Koch, Dorothy; Grainger, Roy G.; Kirkevag, Alf; Iversen, Trond; Seland, Oyvind; Easter, Richard; Ghan, Steven J.; Rasch, Philip J.; Morrison, Hugh; Lamarque, Jean-Francois; Iacono, Michael J.; Kinne, Stefan; Schulz, Michael

    2009-04-10

    Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterizes aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth (Ta) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. It is found that the model-simulated influence of aerosols on cloud droplet number concentration (Nd) compares relatively well to the satellite data at least over the ocean. The relationship between Ta and liquid water path is simulated much too strongly by the models. It is shown that this is partly related to the representation of the second aerosol indirect effect in terms of autoconversion. A positive relationship between total cloud fraction (fcld) and Ta as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strong fcld - Ta relationship, our results indicate that none can be identified as unique explanation. Relationships similar to the ones found in satellite data between Ta and cloud top temperature or outgoing long-wave radiation (OLR) are simulated by only a few GCMs. The GCMs that simulate a negative OLR - Ta relationship show a strong positive correlation between Ta and fcld The short-wave total aerosol radiative forcing as simulated by the GCMs is strongly influenced by the simulated anthropogenic fraction of Ta, and parameterisation assumptions such as a lower bound on Nd

  19. Measuring general surgery residents' communication skills from the patient's perspective using the Communication Assessment Tool (CAT).

    Science.gov (United States)

    Stausmire, Julie M; Cashen, Constance P; Myerholtz, Linda; Buderer, Nancy

    2015-01-01

    The Communication Assessment Tool (CAT) has been used and validated to assess Family and Emergency Medicine resident communication skills from the patient's perspective. However, it has not been previously reported as an outcome measure for general surgery residents. The purpose of this study is to establish initial benchmarking data for the use of the CAT as an evaluation tool in an osteopathic general surgery residency program. Results are analyzed quarterly and used by the program director to provide meaningful feedback and targeted goal setting for residents to demonstrate progressive achievement of interpersonal and communication skills with patients. The 14-item paper version of the CAT (developed by Makoul et al. for residency programs) asks patients to anonymously rate surgery residents on discrete communication skills using a 5-point rating scale immediately after the clinical encounter. Results are reported as the percentage of items rated as "excellent" (5) by the patient. The setting is a hospital-affiliated ambulatory urban surgery office staffed by the residency program. Participants are representative of adult patients of both sexes across all ages with diverse ethnic backgrounds. They include preoperative and postoperative patients, as well as those needing diagnostic testing and follow-up. Data have been collected on 17 general surgery residents from a single residency program representing 5 postgraduate year levels and 448 patient encounters since March 2012. The reliability (Cronbach α) of the tool for surgery residents was 0.98. The overall mean percentage of items rated as excellent was 70% (standard deviations = 42%), with a median of 100%. The CAT is a useful tool for measuring 1 facet of resident communication skills-the patient's perception of the physician-patient encounter. The tool provides a unique and personalized outcome measure for identifying communication strengths and improvement opportunities, allowing residents to receive

  20. Modulation Classification of Satellite Communication Signals Using Cumulants and Neural Networks

    Science.gov (United States)

    Smith, Aaron; Evans, Michael; Downey, Joseph

    2017-01-01

    National Aeronautics and Space Administration (NASA)'s future communication architecture is evaluating cognitive technologies and increased system intelligence. These technologies are expected to reduce the operational complexity of the network, increase science data return, and reduce interference to self and others. In order to increase situational awareness, signal classification algorithms could be applied to identify users and distinguish sources of interference. A significant amount of previous work has been done in the area of automatic signal classification for military and commercial applications. As a preliminary step, we seek to develop a system with the ability to discern signals typically encountered in satellite communication. Proposed is an automatic modulation classifier which utilizes higher order statistics (cumulants) and an estimate of the signal-to-noise ratio. These features are extracted from baseband symbols and then processed by a neural network for classification. The modulation types considered are phase-shift keying (PSK), amplitude and phase-shift keying (APSK),and quadrature amplitude modulation (QAM). Physical layer properties specific to the Digital Video Broadcasting - Satellite- Second Generation (DVB-S2) standard, such as pilots and variable ring ratios, are also considered. This paper will provide simulation results of a candidate modulation classifier, and performance will be evaluated over a range of signal-to-noise ratios, frequency offsets, and nonlinear amplifier distortions.

  1. Virtual target tracking (VTT) as applied to mobile satellite communication networks

    Science.gov (United States)

    Amoozegar, Farid

    1999-08-01

    Traditionally, target tracking has been used for aerospace applications, such as, tracking highly maneuvering targets in a cluttered environment for missile-to-target intercept scenarios. Although the speed and maneuvering capability of current aerospace targets demand more efficient algorithms, many complex techniques have already been proposed in the literature, which primarily cover the defense applications of tracking methods. On the other hand, the rapid growth of Global Communication Systems, Global Information Systems (GIS), and Global Positioning Systems (GPS) is creating new and more diverse challenges for multi-target tracking applications. Mobile communication and computing can very well appreciate a huge market for Cellular Communication and Tracking Devices (CCTD), which will be tracking networked devices at the cellular level. The objective of this paper is to introduce a new concept, i.e., Virtual Target Tracking (VTT) for commercial applications of multi-target tracking algorithms and techniques as applied to mobile satellite communication networks. It would be discussed how Virtual Target Tracking would bring more diversity to target tracking research.

  2. Advanced Communication Technology Satellite (ACTS) Very Small Aperture Terminal (VSAT) Network Control Performance

    Science.gov (United States)

    Coney, T. A.

    1996-01-01

    This paper discusses the performance of the network control function for the Advanced Communications Technology Satellite (ACTS) very small aperture terminal (VSAT) full mesh network. This includes control of all operational activities such as acquisition, synchronization, timing and rain fade compensation as well as control of all communications activities such as on-demand integrated services (voice, video, and date) connects and disconnects Operations control is provided by an in-band orderwire carried in the baseboard processor (BBP) control burst, the orderwire burst, the reference burst, and the uplink traffic burst. Communication services are provided by demand assigned multiple access (DAMA) protocols. The ACTS implementation of DAMA protocols ensures both on-demand and integrated voice, video and data services. Communications services control is also provided by the in-band orderwire but uses only the reference burst and the uplink traffic burst. The performance of the ACTS network control functions have been successfully tested during on-orbit checkout and in various VSAT networks in day to day operations. This paper discusses the network operations and services control performance.

  3. Assimilation of tourism satellite accounts and applied general equilibrium models to inform tourism policy analysis

    OpenAIRE

    Rossouw, Riaan; Saayman, Melville

    2011-01-01

    Historically, tourism policy analysis in South Africa has posed challenges to accurate measurement. The primary reason for this is that tourism is not designated as an 'industry' in standard economic accounts. This paper therefore demonstrates the relevance and need for applied general equilibrium (AGE) models to be completed and extended through an integration with tourism satellite accounts (TSAs) as a tool for policy makers (especially tourism policy makers) in South Africa. The paper sets...

  4. A systems approach to the commercialization of space communications technology - The NASA/JPL Mobile Satellite Program

    Science.gov (United States)

    Weber, William J., III; Gray, Valerie W.; Jackson, Byron; Steele, Laura C.

    1991-10-01

    This paper discusss the systems approach taken by NASA and the Jet Propulsion Laboratory in the commercialization of land-mobile satellite services (LMSS) in the United States. As the lead center for NASA's Mobile Satellite Program, JPL was involved in identifying and addressing many of the key barriers to commercialization of mobile satellite communications, including technical, economic, regulatory and institutional risks, or uncertainties. The systems engineering approach described here was used to mitigate these risks. The result was the development and implementation of the JPL Mobile Satellite Experiment Project. This Project included not only technology development, but also studies to support NASA in the definition of the regulatory, market, and investment environments within which LMSS would evolve and eventually operate, as well as initiatives to mitigate their associated commercialization risks. The end result of these government-led endeavors was the acceleration of the introduction of commercial mobile satellite services, both nationally and internationally.

  5. The Educational Satellite in Perspective

    Science.gov (United States)

    Fraser, D. O.

    1975-01-01

    A discussion which contends that there is merit in not gearing satellite systems solely to educational broadcasting and that they should be designed for general communication, including telephony and television entertainment. (Author/HB)

  6. The Use of a Satellite Communications System for Command and Control of the National Aeronautics and Space Administration Surrogate Unmanned Aerial System Research Aircraft

    Science.gov (United States)

    Howell, Charles T.; Jones, Frank; Hutchinson, Brian; Joyce, Claude; Nelson, Skip; Melum, Mike

    2017-01-01

    The NASA Langley Research Center has transformed a Cirrus Design SR22 general aviation (GA) aircraft into an Unmanned Aerial Systems (UAS) Surrogate research aircraft which has served for several years as a platform for unmanned systems research and development. The aircraft is manned with a Safety Pilot and a Research Systems Operator (RSO) that allows for flight operations almost any-where in the national airspace system (NAS) without the need for a Federal Aviation Administration (FAA) Certificate of Authorization (COA). The UAS Surrogate can be remotely controlled from a modular, transportable ground control station (GCS) like a true UAS. Ground control of the aircraft is accomplished by the use of data links that allow the two-way passage of the required data to control the aircraft and provide the GCS with situational awareness. The original UAS Surrogate data-link system was composed of redundant very high frequency (VHF) data radio modems with a maximum range of approximately 40 nautical miles. A new requirement was developed to extend this range beyond visual range (BVR). This new requirement led to the development of a satellite communications system that provided the means to command and control the UAS Surrogate at ranges beyond the limits of the VHF data links. The system makes use of the Globalstar low earth orbit (LEO) satellite communications system. This paper will provide details of the development, implementation, and flight testing of the satellite data communications system on the UAS Surrogate research aircraft.

  7. General Systems Theory: Application To The Design Of Speech Communication Courses

    Science.gov (United States)

    Tucker, Raymond K.

    1971-01-01

    General systems theory can be applied to problems in the teaching of speech communication courses. The author describes general systems theory as it is applied to the designing, conducting and evaluation of speech communication courses. (Author/MS)

  8. Design and Operation of an IR-CAGE For Thermal Vacuum Testing of a Communication Satellite

    Science.gov (United States)

    Wuersching, C.

    2004-08-01

    A specific infrared radiation device was designed and manufactured for infrared simulation on a communication satellite. For the thermal vacuum test of this satellite, radiation fields with different sizes, shapes and radiation intensities were required to deliver additional heating power onto the space- craft panels. Five of the six sides of the cube- shaped satellite had to be equipped with flat IR- frames so that a cage surrounding the S/C had to be designed. The following features of the IR-cage were re- quired: A lightweight, but still rigid construction of the frame with space-proofed materials; using of standard components for cost reasons; radiation intensities of 400 to 1100 W/m2; a computer-based system for individual control of the heating circuits; a user friendly and safe handling of the operation panel and the recording of all operational parame- ter. The mechanical construction was realised by using aluminium profiles. The standard components al- lowed completing the mechanical set-up within a short time. After some investigation concerning the heating devices it was decided to use heating strips for the radiation fields of low intensity and com- mercial IR-quartz radiators for fields with higher intensity. A special suspension for the heating strips was designed to keep them under defined tension. The power supplies for the heating circuits were computer-controlled. The software allowed the individual power setting of each heater. Addition- ally an automatic mode for controlling the heaters by a reference thermocouple was foreseen. Beside design features of the cage, this paper will also describe the heater concept and the control system, and it will have a look at QA relevant mat- ters.

  9. A Multibeam Dual-Band Orthogonal Linearly Polarized Antenna Array for Satellite Communication on the Move

    Directory of Open Access Journals (Sweden)

    Yi Liu

    2015-01-01

    Full Text Available The design and simulation of a 10 × 8 multibeam dual-band orthogonal linearly polarized antenna array operating at Ku-band are presented for transmit-receive applications. By using patches with different coupling methods as elements, both perpendicular polarization in 12.25–12.75 GHz band and horizontal polarization in 14.0–14.5 GHz band are realized in a shared antenna aperture. A microstrip Rotman lens is employed as the beamforming network with 7 input ports, which can generate a corresponding number of beams to cover −30°–30° with 5 dB beamwidth along one dimension. This type of multibeam orthogonal linearly polarized planar antenna is a good candidate for satellite communication (SatCom.

  10. Performance Analysis of an Enhanced PRMA-HS Protocol for LEO Satellite Communication

    Institute of Scientific and Technical Information of China (English)

    ZHUO Yong-ning; YAN Shao-hu; WU Shi-qi

    2005-01-01

    The packet reservation multiple access with hindering state (PRMA-HS) is a protocol suitable for LEO satellite mobile communication. Although working well with light system payload (amount of user terminals), the protocol imposes high channel congestion on system with heavy payload, thus degrades the system's quality of service. To controlling the channel congestion, a scheme of enhanced PRMA-HS protocol is proposed, which aims to reduce the collision of voice packets by adopting a mechanism of access control. Through theoretic analysis, the system's mathematic model is presented and the packet drop probability of the scheme is deduced. To testify the performance of the scheme, a simulation is performed and the results support our analysis.

  11. Development and Analysis of Image Registration Program for the Communication, Ocean, Meteorological Satellite (COMS

    Directory of Open Access Journals (Sweden)

    Un-Seob Lee

    2007-09-01

    Full Text Available We developed a software for simulations and analyses of the Image Navigation and Registration (INR system, and compares the characteristics of Image Motion Compensation (IMC algorithms for the INR system. According to the orbit errors and attitude errors, the capabilities of the image distortions are analyzed. The distortions of images can be compensated by GOES IMC algorithm and Modified IMC (MIMC algorithm. The capabilities of each IMC algorithm are confirmed based on compensated images. The MIMC yields better results than GOES IMC although both the algorithms well compensate distorted images. The results of this research can be used as valuable asset to design of INR system for the Communication, Ocean, Meteorological Satellite (COMS.

  12. The design and networking of dynamic satellite constellations for global mobile communication systems

    Science.gov (United States)

    Cullen, Cionaith J.; Benedicto, Xavier; Tafazolli, Rahim; Evans, Barry

    1993-01-01

    Various design factors for mobile satellite systems, whose aim is to provide worldwide voice and data communications to users with hand-held terminals, are examined. Two network segments are identified - the ground segment (GS) and the space segment (SS) - and are seen to be highly dependent on each other. The overall architecture must therefore be adapted to both of these segments, rather than each being optimized according to its own criteria. Terrestrial networks are grouped and called the terrestrial segment (TS). In the SS, of fundamental importance is the constellation altitude. The effect of the altitude on decisions such as constellation design choice and on network aspects like call handover statistics are fundamental. Orbit resonance is introduced and referred to throughout. It is specifically examined for its useful properties relating to GS/SS connectivities.

  13. Precoded generalized space shift keying for indoor visible light communications

    KAUST Repository

    Kadampot, Ishaque Ashar

    2014-09-01

    We consider a visible light communication system with 2 transmit light emitting diodes (LED) and nr receive photodiodes. An optical generalized space shift keying modulation scheme is considered for the transmission of bits where each LED can be either in ON state or OFF state at a given time. With this set-up, we design in this paper a precoder for this modulation scheme given the channel state information to improve the bit error rate performance of the system. As conventional precoding techniques for radio frequency at the transmitter cannot be applied to the optical intensity channel, we formulate an optimization problem with constraints for this specific channel. An analytical solution for the precoder is derived and the system performance is compared with and without precoder.

  14. Geostationary Communications Satellites as Sensors for the Space Weather Environment: Telemetry Event Identification Algorithms

    Science.gov (United States)

    Carlton, A.; Cahoy, K.

    2015-12-01

    Reliability of geostationary communication satellites (GEO ComSats) is critical to many industries worldwide. The space radiation environment poses a significant threat and manufacturers and operators expend considerable effort to maintain reliability for users. Knowledge of the space radiation environment at the orbital location of a satellite is of critical importance for diagnosing and resolving issues resulting from space weather, for optimizing cost and reliability, and for space situational awareness. For decades, operators and manufacturers have collected large amounts of telemetry from geostationary (GEO) communications satellites to monitor system health and performance, yet this data is rarely mined for scientific purposes. The goal of this work is to acquire and analyze archived data from commercial operators using new algorithms that can detect when a space weather (or non-space weather) event of interest has occurred or is in progress. We have developed algorithms, collectively called SEER (System Event Evaluation Routine), to statistically analyze power amplifier current and temperature telemetry by identifying deviations from nominal operations or other events and trends of interest. This paper focuses on our work in progress, which currently includes methods for detection of jumps ("spikes", outliers) and step changes (changes in the local mean) in the telemetry. We then examine available space weather data from the NOAA GOES and the NOAA-computed Kp index and sunspot numbers to see what role, if any, it might have played. By combining the results of the algorithm for many components, the spacecraft can be used as a "sensor" for the space radiation environment. Similar events occurring at one time across many component telemetry streams may be indicative of a space radiation event or system-wide health and safety concern. Using SEER on representative datasets of telemetry from Inmarsat and Intelsat, we find events that occur across all or many of

  15. Application of the advanced communications technology satellite for teleradiology and telemedicine

    Science.gov (United States)

    Stewart, Brent K.; Carter, Stephen J.; Rowberg, Alan H.

    1995-05-01

    The authors have an in-kind grant from NASA to investigate the application of the Advanced Communications Technology Satellite (ACTS) to teleradiology and telemedicine using the JPL developed ACTS Mobile Terminal (AMT) uplink. This experiment involves the transmission of medical imagery (CT, MR, CR, US and digitized radiographs including mammograms), between the ACTS/AMT and the University of Washington. This is accomplished by locating the AMT experiment van in various locations throughout Washington state, Idaho, Montana, Oregon and Hawaii. The medical images are transmitted from the ACTS to the downlink at the NASA Lewis Research Center (LeRC) in Cleveland, Ohio, consisting of AMT equipment and the high burst rate-link evaluation terminal (HBR-LET). These images are then routed from LeRC to the University of Washington School of Medicine (UWSoM) through the Internet and public switched Integrated Serviced Digital Network (ISDN). Once images arrive in the UW Radiology Department, they are reviewed using both video monitor softcopy and laser-printed hardcopy. Compressed video teleconferencing and transmission of real-time ultrasound video between the AMT van and the UWSoM are also tested. Image quality comparisons are made using both subjective diagnostic criteria and quantitative engineering analysis. Evaluation is performed during various weather conditions (including rain to assess rain fade compensation algorithms). Compression techniques also are tested to evaluate their effects on image quality, allowing further evaluation of portable teleradiology/telemedicine at lower data rates and providing useful information for additional applications (e.g., smaller remote units, shipboard, emergency disaster, etc.). The medical images received at the UWSoM over the ACTS are directly evaluated against the original digital images. The project demonstrates that a portable satellite-land connection can provide subspecialty consultation and education for rural and remote

  16. Aerosol indirect effects ? general circulation model intercomparison and evaluation with satellite data

    Energy Technology Data Exchange (ETDEWEB)

    Quaas, Johannes; Ming, Yi; Menon, Surabi; Takemura, Toshihiko; Wang, Minghuai; Penner, Joyce E.; Gettelman, Andrew; Lohmann, Ulrike; Bellouin, Nicolas; Boucher, Olivier; Sayer, Andrew M.; Thomas, Gareth E.; McComiskey, Allison; Feingold, Graham; Hoose, Corinna; Kristansson, Jon Egill; Liu, Xiaohong; Balkanski, Yves; Donner, Leo J.; Ginoux, Paul A.; Stier, Philip; Grandey, Benjamin; Feichter, Johann; Sednev, Igor; Bauer, Susanne E.; Koch, Dorothy; Grainger, Roy G.; Kirkevag, Alf; Iversen, Trond; Seland, Oyvind; Easter, Richard; Ghan, Steven J.; Rasch, Philip J.; Morrison, Hugh; Lamarque, Jean-Francois; Iacono, Michael J.; Kinne, Stefan; Schulz, Michael

    2010-03-12

    Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterises aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth ({tau}{sub a}) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. It is found that the model-simulated influence of aerosols on cloud droplet number concentration (N{sub d}) compares relatively well to the satellite data at least over the ocean. The relationship between {tau}{sub a} and liquid water path is simulated much too strongly by the models. This suggests that the implementation of the second aerosol indirect effect mainly in terms of an autoconversion parameterisation has to be revisited in the GCMs. A positive relationship between total cloud fraction (f{sub cld}) and {tau}{sub a} as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strong f{sub cld} - {tau}{sub a} relationship, our results indicate that none can be identified as a unique explanation. Relationships similar to the ones found in satellite data between {tau}{sub a} and cloud top temperature or outgoing long-wave radiation (OLR) are simulated by only a few GCMs. The GCMs that simulate a negative OLR - {tau}{sub a} relationship show a strong positive correlation between {tau}{sub a} and f{sub cld} The short-wave total aerosol radiative forcing as simulated by the GCMs is

  17. Using Satellite Technology to Increase Professional Communications Among Teachers: a Report of Experiments Conducted by the National Education Association.

    Science.gov (United States)

    National Education Association, Washington, DC. Div. of Instruction and Professional Development.

    The National Education Association (NEA) in conjunction with the National Aeronautics and Space Administration, the National Library of Medicine, The Alaska Broadcasting Commission, and the Pacific PEACESAT Network, conducted four satellite experiments designed to improve professional communication among teachers. These programs were the Satellite…

  18. Generalized Encoding CRDSA: Maximizing Throughput in Enhanced Random Access Schemes for Satellite

    Directory of Open Access Journals (Sweden)

    Manlio Bacco

    2014-12-01

    Full Text Available This work starts from the analysis of the literature about the Random Access protocols with contention resolution, such as Contention Resolution Diversity Slotted Aloha (CRDSA, and introduces a possible enhancement, named Generalized Encoding Contention Resolution Diversity Slotted Aloha (GE-CRDSA. The GE-CRDSA aims at improving the aggregated throughput when the system load is less than 50%, playing on the opportunity of transmitting an optimal combination of information and parity packets frame by frame. This paper shows the improvement in terms of throughput, by performing traffic estimation and adaptive choice of information and parity rates, when a satellite network undergoes a variable traffic load profile.

  19. Radiogenic health effects: communicating risks to the general public

    International Nuclear Information System (INIS)

    Strzelczyk, Jadwiga

    1999-01-01

    Harmful effects of prolonged radiation exposures were recognized early on following the discovery of X-rays by W.C. Roentgen in 1895. The type and severity of radiogenic effects are functions of a number of factors, radiation quality and quantity, chemical toxicity, and radiosensitivity of irradiated tissues being the most significant ones. Currently, there are several human registries for radiogenic cancers. Atomic bomb and nuclear test survivors, and populations exposed to medical irradiation constitute the largest study cohorts. Two general types of radiogenic effects have emerged from these registries: prompt and delayed. While the effects of acute exposures are very well documented, investigations of the effects of low-level exposures require the use of mathematical models. Communicating the risks of lower-level chronic radiation exposures to the general public remains a challenging task. The most effective approaches include clear interpretation and placing radiation risks in perspective: risks versus benefits, and comparisons with risks carried by common activities in which we all engage. (author)

  20. Dialing long distance : communications to northern operations like the MGP require sophisticated satellite networks for voice, data

    Energy Technology Data Exchange (ETDEWEB)

    Cook, D.

    2006-04-15

    Telecommunications will play a major role in the construction of the Mackenzie Gas Project due to the remoteness of its location and the volume of communication data required to support the number of people involved and the amount of construction activity. While suppliers for communications tools have not yet been identified, initial telecommunications plans call for the installation of communication equipment at all camps, major facility sites and construction locations. Equipment will be housed in self-contained, climate-controlled buildings called telecommunication service modules (TSMs), which will be connected to each other as well as to existing public communications networks. The infrastructure will support telephone and fax systems; Internet and electronic mail services; multiple channel very high frequency radios; air-to-ground communication at airstrips and helipads; ship-to-shore at barge landings; closed circuit television; satellite community antenna television; CBC radio broadcast; public address systems; security systems; and supervisory control and data acquisition (SCADA) systems. An Internet Protocol (IP) network with a voice telephone system will be implemented along with a geostationary orbit satellite network. Satellite servers and real-time data services will be used. Car kits that allow call and battery-operated self-contained telemetry devices designed to communicate via a satellite system have been commissioned for the project that are capable of providing cost-efficient and reliable asset tracking and fleet management in remote regions and assisting in deployment requirements. It was concluded that many of today's mega-projects are the driving factors behind new telecommunications solutions in remote areas. 1 fig.

  1. Evolving earth-based and in-situ satellite network architectures for Mars communications and navigation support

    Science.gov (United States)

    Hastrup, Rolf; Weinberg, Aaron; McOmber, Robert

    1991-09-01

    Results of on-going studies to develop navigation/telecommunications network concepts to support future robotic and human missions to Mars are presented. The performance and connectivity improvements provided by the relay network will permit use of simpler, lower performance, and less costly telecom subsystems for the in-situ mission exploration elements. Orbiting relay satellites can serve as effective navigation aids by supporting earth-based tracking as well as providing Mars-centered radiometric data for mission elements approaching, in orbit, or on the surface of Mars. The relay satellite orbits may be selected to optimize navigation aid support and communication coverage for specific mission sets.

  2. Advanced Communication Technology Satellite (ACTS) Multibeam Antenna On-Orbit Performance

    Science.gov (United States)

    1995-01-01

    The NASA Lewis Research Center's Advanced Communication Technology Satellite (ACTS) was launched in September 1993. ACTS introduced several new technologies, including a multibeam antenna (MBA) operating at extremely short wavelengths never before used in communications. This antenna, which has both fixed and rapidly reconfigurable high-energy spot beams (150 miles in diameter), serves users equipped with small antenna terminals. Extensive structural and thermal analyses have been performed for simulating the ACTS MBA on-orbit performance. The results show that the reflector surfaces (mainly the front subreflector), antenna support assembly, and metallic surfaces on the spacecraft body will be distorted because of the thermal effects of varying solar heating, which degrade the ACTS MBA performance. Since ACTS was launched, a number of evaluations have been performed to assess MBA performance in the space environment. For example, the on-orbit performance measurements found systematic environmental disturbances to the MBA beam pointing. These disturbances were found to be imposed by the attitude control system, antenna and spacecraft mechanical alignments, and on-orbit thermal effects. As a result, the MBA may not always exactly cover the intended service area. In addition, the on-orbit measurements showed that antenna pointing accuracy is the performance parameter most sensitive to thermal distortions on the front subreflector surface and antenna support assemblies. Several compensation approaches were tested and evaluated to restore on-orbit pointing stability. A combination of autotrack (75 percent of the time) and Earth sensor control (25 percent of the time) was found to be the best way to compensate for antenna pointing error during orbit. This approach greatly minimizes the effects of thermal distortions on antenna beam pointing.

  3. Generalization of a pictorial alternative communication system across instructors and distance.

    Science.gov (United States)

    Ganz, Jennifer B; Sigafoos, Jeff; Simpson, Richard L; Cook, Katherine E

    2008-01-01

    Nonverbal individuals with autism spectrum disorders (ASD) often require the use of picture-based, aided augmentative and alternative communication (AAC) systems. Such systems are used widely, but little research has investigated the generalization of these devices to a variety of communicative partners and under a variety of conditions. We investigated use of a modified Picture Exchange Communication System (PECS) protocol to teach AAC-supported functional communication skills to a 12-year-old boy with autism. Results indicate that the participant was able to generalize his communication skills across a variety of instructors and to use functional non-verbal strategies to respond to communication obstacles.

  4. Investigation of multipactor breakdown in communication satellite microwave co-axial systems

    Science.gov (United States)

    Nagesh, S. K.; Revannasiddiah, D.; Shastry, S. V. K.

    2005-01-01

    Multipactor breakdown or multipactor discharge is a form of high frequency discharge that may occur in microwave components operating at very low pressures. Some RF components of multi-channel communication satellites have co-axial geometry and handle high RF power under near-vacuum conditions. The breakdown occurs due to secondary electron resonance, wherein electrons move back and forth in synchronism with the RF voltage across the gap between the inner and outer conductors of the co-axial structure. If the yield of secondary electrons from the walls of the co-axial structure is greater than unity, then the electron density increases with time and eventually leads to the breakdown. In this paper, the current due to the oscillating electrons in the co-axial geometry has been treated as a radially oriented Hertzian dipole. The electric field, due to this dipole, at any point in the coaxial structure, may then be determined by employing the dyadic Green's function technique. This field has been compared with the field that would exist in the absence of multipactor.

  5. Simulative Analysis of Inter-Satellite Optical Wireless Communication (IsOWC) Link with EDFA

    Science.gov (United States)

    Singh, Mehtab; Singh, Navpreet

    2018-04-01

    In this paper, simulative analysis and performance comparison of different EDFA (Erbium-doped fiber amplifier) configurations in a 10 Gbps inter-satellite optical wireless communication (IsOWC) link have been reported for a 5,000 km long link and 1,550 nm operating wavelength. The results show that system in which both pre-amplifier and booster amplifier stages are implemented simultaneously outperforms systems with only pre-amplifier and booster amplifier stage. From the results, it can be seen that by deploying a transmission power level of 15 dBm, a link distance of 9,600 km can be achieved with a quality factor of 6.01 dB and BER (Bit error rate) of 1.07×10-9. Also, in this paper, the performance of an 8×7 Gbps WDM-IsOWC link has been reported. The results show that by using both EDFA pre-amplifier and booster amplifier stages, a link distance of 8,000 km for each channel is achievable with desired performance levels (Q≥6 and BER≤10-9). Also, the effect of channel spacing on the performance of WDM-IsOWC link is investigated. The results show that the received signal has acceptable performance levels when the channel spacing is 100 GHz but when the channel spacing is reduced to 80 GHz, the quality of the received signal degrades and link distance decreases.

  6. K-Band Phased Array Developed for Low- Earth-Orbit Satellite Communications

    Science.gov (United States)

    Anzic, Godfrey

    1999-01-01

    Future rapid deployment of low- and medium-Earth-orbit satellite constellations that will offer various narrow- to wide-band wireless communications services will require phased-array antennas that feature wide-angle and superagile electronic steering of one or more antenna beams. Antennas, which employ monolithic microwave integrated circuits (MMIC), are perfectly suited for this application. Under a cooperative agreement, an MMIC-based, K-band phased-array antenna is being developed with 50/50 cost sharing by the NASA Lewis Research Center and Raytheon Systems Company. The transmitting array, which will operate at 19 gigahertz (GHz), is a state-of-the-art design that features dual, independent, electronically steerable beam operation ( 42 ), a stand-alone thermal management, and a high-density tile architecture. This array can transmit 622 megabits per second (Mbps) in each beam from Earth orbit to small Earth terminals. The weight of the total array package is expected to be less than 8 lb. The tile integration technology (flip chip MMIC tile) chosen for this project represents a major advancement in phased-array engineering and holds much promise for reducing manufacturing costs.

  7. Performance characteristics of the 12 GHz, 200 watt Transmitter Experiment Package for CTS. [Communication Technology Satellite

    Science.gov (United States)

    Miller, E. F.; Fiala, J. L.; Hansen, I. G.

    1975-01-01

    Measured performance characteristics from ground test of the Transmitter Experiment Package (TEP) for the Communications Technology Satellite are presented. The experiment package consists of a 200 W Output Stage Tube (OST) powered by a Power Processing System (PPS). Descriptions of both the PPS and OST are given. The PPS provides the necessary voltages with a measured dc/dc conversion efficiency of 89 per cent. The OST, a traveling wave tube with multiple collectors, has a saturated rf output power of 224 W and operates at an overall efficiency exceeding 40 per cent over an 85 MHz bandwidth at 12 GHz. OST performance given includes frequency response, saturation characteristics, group delay, AM to PM conversion, intermodulation distortion, and two channel gain suppression. Single and dual channel FM video performance is presented. It was determined that for 12 MHz peak to peak frequency deviation on each channel, dual channel FM television signals can be transmitted through the TEP at 60 W, each channel, with 40 MHz channel spacing (center to center).

  8. On board processing for future satellite communications systems: Comparison of FDM, TDM and hybrid accessing schemes

    Science.gov (United States)

    Berk, G.; Jean, P. N.; Rotholz, E.

    1982-01-01

    Several satellite uplink and downlink accessing schemes for customer premises service are compared. Four conceptual system designs are presented: satellite-routed frequency division multiple access (FDMA), satellite-switched time division multiple access (TDMA), processor-routed TDMA, and frequency-routed TDMA, operating in the 30/20 GHz band. The designs are compared on the basis of estimated satellite weight, system capacity, power consumption, and cost. The systems are analyzed for fixed multibeam coverage of the continental United States. Analysis shows that the system capacity is limited by the available satellite resources and by the terminal size and cost.

  9. Mutual understanding: a communication model for general practice.

    Science.gov (United States)

    Hantho, Arne; Jensen, Lena; Malterud, Kirsti

    2002-12-01

    To present our pursuits towards development of a simple model for clinical communication intended for application by the practitioner as a tool for enhancing mutual understanding. Inspired by theories about patient-centredness and interactive modes of understanding, and supported by the perspectives of the Danish philosopher Niels Thomassen, we reviewed audiotapes from our own consultations. Recognising four dimensions assumed to be essential for mutual understanding in the transcripts, we explored these dimensions further. We present a communication model consisting of the following dimensions: The Framework, within which the communication takes place; The Subject, about which the communication takes place; The Persons, between whom the communication takes place; and The Action, verbally and non-verbally, through which communication takes place. We describe these dimensions in detail. The nature of the dimensions indicates that there is an interrelationship between them, implying that the character of the communication may change if one of the factors is changed. Analysis of an ongoing or recent consultation completed in accordance with these four dimensions allows the doctor to refocus the communication, thus leading to a more extensive mutual understanding and perhaps enhanced freedom of action.

  10. GAUSS Market Analysis for Integrated Satellite Communication and Navigation Location Based services

    Science.gov (United States)

    Di Fazio, Antonella; Dricot, Fabienne; Tata, Francesco

    2003-07-01

    The demand for mobile information services coupled with positioning technologies for delivering value- added services that depend on a user's location has rapidly increased during last years. In particular, services and applications related with improved mobility safety and transport efficiency look very attractive.Solutions for location services vary in respect of positioning accuracy and the technical infrastructure required, and the associated investment in terminals and networks. From the analysis of the state-of-the art, it comes that various technologies are currently available on the European market, while mobile industry is gearing up to launch a wide variety of location services like tracking, alarming and locating.Nevertheless, when addressing safety of life as well as security applications, severe hurdles have to be posed in the light of existing technologies. Existing navigation (e.g. GPS) and communication systems are not able to completely satisfy the needs and requirements of safety-of-life-critical applications. As a matter of fact, the GPS system's main weaknesses today is its lack of integrity, which means its inability to warn users of a malfunction in a reasonable time, while the other positioning techniques do not provide satisfactory accuracy as well, and terrestrial communication networks are not capable to cope with stringent requirement in terms of service reliability and coverage.In this context, GAUSS proposes an innovative satellite-based solution using novel technology and effective tools for addressing mobility challenges in a cost efficient manner, improving safety and effectiveness.GAUSS (Galileo And UMTS Synergetic System) is a Research and Technological Development project co- funded by European Commission, within the frame of the 5th IST Programme. The project lasted two years, and it was successfully completed in November 2002. GAUSS key concept is the integration of Satellite Navigation GNSS and UMTS communication technology, to

  11. Design of an Image Motion Compenstaion (IMC Algorithm for Image Registration of the Communication, Ocean, Meteorolotical Satellite (COMS-1

    Directory of Open Access Journals (Sweden)

    Taek Seo Jung

    2006-03-01

    Full Text Available This paper presents an Image Motion Compensation (IMC algorithm for the Korea's Communication, Ocean, and Meteorological Satellite (COMS-1. An IMC algorithm is a priority component of image registration in Image Navigation and Registration (INR system to locate and register radiometric image data. Due to various perturbations, a satellite has orbit and attitude errors with respect to a reference motion. These errors cause depointing of the imager aiming direction, and in consequence cause image distortions. To correct the depointing of the imager aiming direction, a compensation algorithm is designed by adapting different equations from those used for the GOES satellites. The capability of the algorithm is compared with that of existing algorithm applied to the GOES's INR system. The algorithm developed in this paper improves pointing accuracy by 40%, and efficiently compensates the depointings of the imager aiming direction.

  12. Robust general N user authentication scheme in a centralized quantum communication network via generalized GHZ states

    Science.gov (United States)

    Farouk, Ahmed; Batle, J.; Elhoseny, M.; Naseri, Mosayeb; Lone, Muzaffar; Fedorov, Alex; Alkhambashi, Majid; Ahmed, Syed Hassan; Abdel-Aty, M.

    2018-04-01

    Quantum communication provides an enormous advantage over its classical counterpart: security of communications based on the very principles of quantum mechanics. Researchers have proposed several approaches for user identity authentication via entanglement. Unfortunately, these protocols fail because an attacker can capture some of the particles in a transmitted sequence and send what is left to the receiver through a quantum channel. Subsequently, the attacker can restore some of the confidential messages, giving rise to the possibility of information leakage. Here we present a new robust General N user authentication protocol based on N-particle Greenberger-Horne-Zeilinger (GHZ) states, which makes eavesdropping detection more effective and secure, as compared to some current authentication protocols. The security analysis of our protocol for various kinds of attacks verifies that it is unconditionally secure, and that an attacker will not obtain any information about the transmitted key. Moreover, as the number of transferred key bits N becomes larger, while the number of users for transmitting the information is increased, the probability of effectively obtaining the transmitted authentication keys is reduced to zero.

  13. A design proposal of a certain missile tactical command system based on Beidou satellite communication and GPS positioning techniques

    Science.gov (United States)

    Ma, Jian; Hao, Yongsheng; Miao, Jian; Zhang, Jianmao

    2007-11-01

    This paper introduced a design proposal of tactical command system that applied to a kind of anti-tank missile carriers. The tactical command system was made up of embedded computer system based on PC104 bus, Linux operating system, digital military map, Beidou satellite communication equipments and GPS positioning equipments. The geographic coordinates was measured by the GPS receiver, the positioning data, commands and information were transmitted real-time between tactical command systems, tactical command systems and command center, by the Beidou satellite communication systems. The Beidou satellite communication equipments and GPS positioning equipments were integrated to an independent module, exchanging data with embedded computer through RS232 serial ports and USB ports. The decision support system software based on information fusion, calculates positioning data, geography information and battle field information synthetically, shows the position of allies and the position of enemy on the military map, and assesses the various threats of different enemy objects, educes a situation assessment and threat assessment.

  14. Development of U.S. Government General Technical Requirements for UAS Flight Safety Systems Utilizing the Iridium Satellite Constellation

    Science.gov (United States)

    Murray, Jennifer; Birr, Richard

    2010-01-01

    This slide presentation reviews the development of technical requirements for Unmanned Aircraft Systems (UAS) utilization of the Iridium Satellite Constellation to provide flight safety. The Federal Aviation Authority (FAA) required an over-the-horizon communication standard to guarantee flight safety before permitting widespread UAS flights in the National Air Space (NAS). This is important to ensure reliable control of UASs during loss-link and over-the-horizon scenarios. The core requirement was to utilize a satellite system to send GPS tracking data and other telemetry from a flight vehicle down to the ground. Iridium was chosen as the system because it is one of the only true satellite systems that has world wide coverage, and the service has a highly reliable link margin. The Iridium system, the flight modems, and the test flight are described.

  15. Perceived barriers and facilitators for general practitioner-patient communication in palliative care: a systematic review

    NARCIS (Netherlands)

    Slort, W.; Schweitzer, B.P.M.; Blankenstein, A.H.; Abarshi, E.A.; Riphagen, I.I.; Echteld, M.A.; Aaronson, N.K.; van der Horst, H.E.; Deliens, L.

    2011-01-01

    While effective general practitioner (GP)-patient communication is required for the provision of good palliative care, barriers and facilitators for this communication are largely unknown. We aimed to identify barriers and facilitators for GP-patient communication in palliative care. In a systematic

  16. Perceived barriers and facilitators for general practitioner-patient communication in palliative care: A systematic review

    NARCIS (Netherlands)

    Slort, W.; Schweitzer, B.P.M.; Blankenstein, A.H.; Abarshi-Fatiregun, E.A.B.; Riphagen, I.; Echteld, M.A.; Aaronson, N.K.; van der Horst, H.E.; Deliens, L.

    2011-01-01

    While effective general practitioner (GP)-patient communication is required for the provision of good palliative care, barriers and facilitators for this communication are largely unknown. We aimed to identify barriers and facilitators for GP-patient communication in palliative care. In a systematic

  17. Development of the EMAP tool facilitating existential communication between general practitioners and cancer patients

    DEFF Research Database (Denmark)

    Assing Hvidt, Elisabeth; Hansen, Dorte Gilså; Ammentorp, Jette

    2017-01-01

    BACKGROUND: General practice recognizes the existential dimension as an integral part of multidimensional patient care alongside the physical, psychological and social dimensions. However, general practitioners (GPs) report substantial barriers related to communication with patients about existen...

  18. Izviđanje satelitskih komunikacija u funkciji savremenih operacija / Reconnaissance of satellite communications in contemporary operations

    Directory of Open Access Journals (Sweden)

    Slaviša Đukanović

    2004-05-01

    Full Text Available Raspoloživi vojni resursi u bilo kojoj kategoriji nisu kritični u mirnodopskom periodu, jer se dimenzionišu za ratno naprezanje određenog nivoa. Međutim, u uslovima izvođenja borbenih dejstava postoje ekstremi u zahtevima za angažovanjem, koje sistemi ne mogu da izdrže. Takav slučaj je kod satelitskih komunikacija. U radu su prezentovane taktičko-tehničke i dinamičke osobine komercijalnih (INMARSAT, INTELSAT, IRIDIJUM.. i vojnih (DSCS, FLEET-SATCOM, NATO, SKYNET.. satelitskih sistema, koje su bitne za uspešno vođenje elektronskog rata. Takođe, dat je pregled raspoloživih korisničkih servisa savremenih satelitskih sistema (Internet provajding video-konferencije, prenos multimedija uživo, fax, e-mail, voice. Nova generacija širokopojasnih satelita, koja se pušta u rad tokom ove godine omogućiće globalni roming navedenih servisa INMARSAT satelitskom sistemu koji se sve češće koristi u vojne svrhe. U perspektivi je da se usluge koje pružaju satelitski sistemi (komunikacioni, navigacioni, izviđački meteorološki.. stave na raspolaganje nižim taktičkim jedinicama vazduhoplovima, pa čak i svakom vojniku ponaosob. Poznavanje satelitskih sistema potencijalnog agresora pruža mogućnost da se odrede ranjive tačke samog sistema sa aspekta izviđanja i ometanja. / Available military resources in any category are not critical in peace since they are tailored for military use under extreme conditions. However, some systems such as satellite communications, cannot meet extreme requirements during combat actions. The paper presents tactical and technical specifications and dynamic characteristics of commercial (INMARSAT. INTELSAT, IRIDIJUM,.. and military (DSCS, FLEET-SATCOM, NATO, SKYNET,.. satellite systems which are important for electronic warfare. The paper also gives available user services of contemporary satellite systems (Internet providing, videoconferences, live multi-media, fax, e-mail, voice. A new generation of

  19. Communicating airport noise emission data to the general public.

    Science.gov (United States)

    Gasco, Luis; Asensio, Cesar; de Arcas, Guillermo

    2017-05-15

    Despite the efforts that the aviation industry has undertaken during the last few decades, noise annoyance remains high, partly because of the continuous transport demands of modern societies and partly because of changes in citizen expectations and their growing environmental concerns. Although modern aircraft are considerably quieter than their predecessors, the number of complaints has not decreased as much as expected. Therefore, the aeronautical sector has tried more sociological and/or psychological strategies to gain acceptance through awareness and community engagement. In this regard, noise communication to the public is crucial for managers and policy makers. Noise information is a difficult technical topic for non-experts, which is an issue that must first be addressed to take advantage of the new possibilities that have recently been opened by the internet and information and communication technologies. In this review paper, we have compiled the literature that shows the increasing importance of communicating noise information from aircraft and the variety of indicators used to communicate with the public. We also examined the methods of representing noise data, using visualization strategies, and new tools airports are currently using to address this communication problem. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Program on application of communications satellites to educational development: Design of a 12 channel FM microwave receiver. [color television from communication satellites

    Science.gov (United States)

    Risch, C. O.; Rosenbaum, F. J.; Gregory, R. O.

    1974-01-01

    The design, fabrication, and performance of elements of a low cost FM microwave satellite ground station receiver is described. It is capable of accepting 12 contiguous color television equivalent bandwidth channels in the 11.72 to 12.2 GHz band. Each channel is 40 MHz wide and incorporates a 4 MHz guard band. The modulation format is wideband FM and the channels are frequency division multiplexed. Twelve independent CATV compatible baseband outputs are provided. The overall system specifications are first discussed, then consideration is given to the receiver subsystems and the signal branching network.

  1. Study of Education Satellite Communication Demonstration. Third Quarterly Progress Report. Report of Activities and Accomplishments January 11, 1975 to April 10, 1975.

    Science.gov (United States)

    Syracuse Univ. Research Corp., NY. Educational Policy Research Center.

    A report on the Education Satellite Communication Demonstration (ESCD) describes activities of the evaluators during the first quarter of 1975, including staff trips and site visits and activities of various staff members. A calendar of future events in satellites, telecommunications, and education is included, with revision on dates and new…

  2. Radiation-hard mid-power booster optical fiber amplifiers for high-speed digital and analogue satellite laser communication links

    Science.gov (United States)

    Stampoulidis, L.; Kehayas, E.; Stevens, G.; Henwood-Moroney, L.; Hosking, P.; Robertson, A.

    2017-11-01

    Optical laser communications (OLC) has been identified as the technology to enable high-data rate, secure links between and within satellites, as well as between satellites and ground stations with decreased mass, size, and electrical power compared to traditional RF technology.

  3. Proceedings of the Twentieth NASA Propagation Experimenters Meeting (NAPEX XX) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop

    Science.gov (United States)

    Golshan, Nassar (Editor)

    1996-01-01

    The NASA Propagation Experimenters (NAPEX) Meeting and associated Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop convene yearly to discuss studies supported by the NASA Propagation Program. Representatives from the satellite communications (satcom)industry, academia, and government with an interest in space-ground radio wave propagation have peer discussion of work in progress, disseminate propagation results, and interact with the satcom industry. NAPEX XX, in Fairbanks, Alaska, June 4-5, 1996, had three sessions: (1) "ACTS Propagation Study: Background, Objectives, and Outcomes," covered results from thirteen station-years of Ka-band experiments; (2) "Propagation Studies for Mobile and Personal Satellite Applications," provided the latest developments in measurement, modeling, and dissemination of propagation phenomena of interest to the mobile, personal, and aeronautical satcom industry; and (3)"Propagation Research Topics," covered a range of topics including space/ground optical propagation experiments, propagation databases, the NASA Propagation Web Site, and revision plans for the NASA propagation effects handbooks. The ACTS Miniworkshop, June 6, 1996, covered ACTS status, engineering support for ACTS propagation terminals, and the ACTS Propagation Data Center. A plenary session made specific recommendations for the future direction of the program.

  4. [Mobile hospital -real time mobile telehealthcare system with ultrasound and CT van using high-speed satellite communication-].

    Science.gov (United States)

    Takizawa, Masaomi; Miyashita, Toyohisa; Murase, Sumio; Kanda, Hirohito; Karaki, Yoshiaki; Yagi, Kazuo; Ohue, Toru

    2003-01-01

    A real-time telescreening system is developed to detect early diseases for rural area residents using two types of mobile vans with a portable satellite station. The system consists of a satellite communication system with 1.5Mbps of the JCSAT-1B satellite, a spiral CT van, an ultrasound imaging van with two video conference system, a DICOM server and a multicast communication unit. The video image and examination image data are transmitted from the van to hospitals and the university simultaneously. Physician in the hospital observes and interprets exam images from the van and watches the video images of the position of ultrasound transducer on screenee in the van. After the observation images, physician explains a results of the examination by the video conference system. Seventy lung CT screening and 203 ultrasound screening were done from March to June 2002. The trial of this real time screening suggested that rural residents are given better healthcare without visit to the hospital. And it will open the gateway to reduce the medical cost and medical divide between city area and rural area.

  5. Integration between terrestrial-based and satellite-based land mobile communications systems

    Science.gov (United States)

    Arcidiancono, Antonio

    1990-01-01

    A survey is given of several approaches to improving the performance and marketability of mobile satellite systems (MSS). The provision of voice/data services in the future regional European Land Mobile Satellite System (LMSS), network integration between the Digital Cellular Mobile System (GSM) and LMSS, the identification of critical areas for the implementation of integrated GSM/LMSS areas, space segment scenarios, LMSS for digital trunked private mobile radio (PMR) services, and code division multiple access (CDMA) techniques for a terrestrial/satellite system are covered.

  6. A proposed architecture for a satellite-based mobile communications network - The lowest three layers

    Science.gov (United States)

    Yan, T. Y.; Naderi, F. M.

    1986-01-01

    Architecture for a commercial mobile satellite network is proposed. The mobile satellite system (MSS) is composed of a network management center, mobile terminals, base stations, and gateways; the functions of each component are described. The satellite is a 'bent pipe' that performs frequency translations, and it has multiple UHF beams. The development of the MSS design based on the seven-layer open system interconnection model is examined. Consideration is given to the functions of the physical, data link, and network layers and the integrated adaptive mobile access protocol.

  7. Evaluation of water vapor distribution in general circulation models using satellite observations

    Science.gov (United States)

    Soden, Brian J.; Bretherton, Francis P.

    1994-01-01

    This paper presents a comparison of the water vapor distribution obtained from two general circulation models, the European Centre for Medium-Range Weather Forecasts (ECMWF) model and the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM), with satellite observations of total precipitable water (TPW) from Special Sensor Microwave/Imager (SSM/I) and upper tropospheric relative humidity (UTH) from GOES. Overall, both models are successful in capturing the primary features of the observed water vapor distribution and its seasonal variation. For the ECMWF model, however, a systematic moist bias in TPW is noted over well-known stratocumulus regions in the eastern subtropical oceans. Comparison with radiosonde profiles suggests that this problem is attributable to difficulties in modeling the shallowness of the boundary layer and large vertical water vapor gradients which characterize these regions. In comparison, the CCM is more successful in capturing the low values of TPW in the stratocumulus regions, although it tends to exhibit a dry bias over the eastern half of the subtropical oceans and a corresponding moist bias in the western half. The CCM also significantly overestimates the daily variability of the moisture fields in convective regions, suggesting a problem in simulating the temporal nature of moisture transport by deep convection. Comparison of the monthly mean UTH distribution indicates generally larger discrepancies than were noted for TPW owing to the greater influence of large-scale dynamical processes in determining the distribution of UTH. In particular, the ECMWF model exhibits a distinct dry bias along the Intertropical Convergence Zone (ITCZ) and a moist bias over the subtropical descending branches of the Hadley cell, suggesting an underprediction in the strength of the Hadley circulation. The CCM, on the other hand, demonstrates greater discrepancies in UTH than are observed for the ECMWF model, but none that are as

  8. Lightning-generated whistler waves observed by probes on the Communication/Navigation Outage Forecast System satellite at low latitudes

    Science.gov (United States)

    Holzworth, R. H.; McCarthy, M. P.; Pfaff, R. F.; Jacobson, A. R.; Willcockson, W. L.; Rowland, D. E.

    2011-06-01

    Direct evidence is presented for a causal relationship between lightning and strong electric field transients inside equatorial ionospheric density depletions. In fact, these whistler mode plasma waves may be the dominant electric field signal within such depletions. Optical lightning data from the Communication/Navigation Outage Forecast System (C/NOFS) satellite and global lightning location information from the World Wide Lightning Location Network are presented as independent verification that these electric field transients are caused by lightning. The electric field instrument on C/NOFS routinely measures lightning-related electric field wave packets or sferics, associated with simultaneous measurements of optical flashes at all altitudes encountered by the satellite (401-867 km). Lightning-generated whistler waves have abundant access to the topside ionosphere, even close to the magnetic equator.

  9. Improving Pilot/ATC Voice Communication in General Aviation

    National Research Council Canada - National Science Library

    Morrow, Daniel

    1999-01-01

    ...) Basic General Aviation Research Simulator (BGARS). Prior to flying the simulator each pilot was provided with familiarization training, listened to and read back ATC messages spoken in either grouped or sequential format...

  10. Proceedings of the Twentieth NASA Propagation Experimenters Meeting (NAPEX 20) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop

    Science.gov (United States)

    Golshan, Nasser (Editor)

    1996-01-01

    The NASA Propagation Experimenters (NAPEX) Meeting is convened each year to discuss studies supported by the NASA Propagation Program. Representatives from the satellite communications (satcom) industry, academia, and government who have an interest in space-ground radio wave propagation are invited to NAPEX meetings for discussions and exchange of information. The reports delivered at these meetings by program managers and investigators present recent activities and future plans. This forum provides an opportunity for peer discussion of work in progress, timely dissemination of propagation results, and close interaction with the satcom industry.

  11. Satellite orbits perturbed by direct solar radiation pressure: general expansion of the disturbing function

    International Nuclear Information System (INIS)

    Hughes, S.

    1977-01-01

    An expression is derived for the solar radiation pressure disturbing function on an Earth satellite orbit which takes into account the variation of the solar radiation flux with distance from the Sun's centre and the absorption of radiation by the satellite. This expression is then expanded in terms of the Keplerian elements of the satellite and solar orbits using Kaula's method (Astr. J.; 67:300 (1962)). The Kaula inclination functions are replaced by an equivalent set of modified Allan (Proc. R. Soc. A.; 288:60 (1965)) inclination functions. The resulting expression reduces to the form commonly used in solar radiation pressure perturbation studies (e.g. Aksnes, Cel. Mech.; 13:89 (1976)), when certain terms are neglected. If, as happens quite often in practice, a satellite's orbit is in near-resonance with certain of these neglected terms, these near-resonant terms can cause changes in the satellite's orbital elements comparable to those produced by the largest term in Aksnes's expression. A new expression for the solar radiation pressure disturbing function expansion is suggested for use in future studies of satellite orbits perturbed by solar radiation pressure. (author)

  12. General Education Oral Communication Assessment and Student Preferences for Learning: E-Textbook versus Paper Textbook

    Science.gov (United States)

    Dwyer, Karen Kangas; Davidson, Marlina M.

    2013-01-01

    As part of a yearly university mandated assessment of a large basic communication course that fulfills the oral communication general education requirement, this study examined student preferences for textbooks, reading, and learning. Specifically, basic course students ("N"=321) at a large state university in the Midwest were asked to…

  13. The Transformative Power of Communication: Democratizing Practices for the General Education Classroom

    Science.gov (United States)

    Haynal, Kaitlyn

    2016-01-01

    This article examines the common communication practices of deliberation, discussion, delivery, and debate, for their democratizing potential through their greater inclusion in all general education classrooms. It argues that these tools are underutilized outside of communication classrooms but offer numerous benefits to teachers and students…

  14. Disaster Managers’ Perception of Effective Visual Risk Communication for General Public

    NARCIS (Netherlands)

    Charriere, M.K.M.; Bogaard, T.A.; Mostert, E.

    2012-01-01

    Risk communication is one of the measures that should be implemented to increase the awareness and preparedness of the general public in order to attain disaster risk reduction. Among the various forms that can be used in communication campaigns, visualizations are appropriate to disseminate

  15. Accelerated life tests of specimen heat pipe from Communication Technology Satellite (CTS) project

    Science.gov (United States)

    Tower, L. K.; Kaufman, W. B.

    1977-01-01

    A gas-loaded variable conductance heat pipe of stainless steel with methanol working fluid identical to one now on the CTS satellite was life tested in the laboratory at accelerated conditions for 14 200 hours, equivalent to about 70 000 hours at flight conditions. The noncondensible gas inventory increased about 20 percent over the original charge. The observed gas increase is estimated to increase operating temperature by about 2.2 C, insufficient to harm the electronic gear cooled by the heat pipes in the satellite. Tests of maximum heat input against evaporator elevation agree well with the manufacturer's predictions.

  16. Satellite and Ground Communication Systems: Space and Electronic Warfare Threats to the United States Army

    Science.gov (United States)

    2017-02-01

    as if SATCOM is guaranteed. This complacency is accompanied by the procurement of high-data communication and mission command systems that deny...threat. To overcome these significant vulnerabilities, the US Army must procure communications systems that maintain the information high ground, but...precious gift of our freedom.”1 A key element of remaining strong on the ground is maintaining the capability to effectively communicate on the ground. If

  17. General consumer communication tools for improved image management and communication in medicine

    Science.gov (United States)

    Ratib, Osman M.; Rosset, Antoine; McCoy, J. Michael

    2005-04-01

    We elected to explore emerging consumer technologies that can be adopted to improve and facilitate image and data communication in medical and clinical environment. The wide adoption of new communication paradigm such as instant messaging, chatting and direct emailing can be integrated in specific applications. The increasing capacity of portable and hand held devices such as iPod music players offer an attractive alternative for data storage that exceeds the capabilities of traditional offline storage media such as CD or even DVD. We adapted medical image display and manipulation software called OSIRIX to integrate different innovative technologies facilitating the communication and data transfer between remote users. We integrated email and instant messaging features to the program allowing users to instantaneously email an image or a set of images that are displayed on the screen. Using iChat instant messaging application from Apple a user can share the content of his screen with a remote correspondent and communicate in real time using voice and video. To provide convenient mechanism for exchange of large data sets the program can store the data in DICOM format on CD or DVD, but was also extended to use the large storage capacity of iPod hard disks as well as Apple"s online storage service "dot Mac" that users can subscribe to benefit from scalable secure storage that accessible from anywhere on the internet. The adoption of these innovative technologies is likely to change the architecture of traditional picture archiving and communication systems and provide more flexible and efficient means of communication.

  18. Communication about euthanasia in general practice: opinions and experiences of patients and their general practitioners.

    Science.gov (United States)

    Borgsteede, Sander D; Deliens, Luc; Graafland-Riedstra, Corrie; Francke, Anneke L; van der Wal, Gerrit; Willems, Dick L

    2007-05-01

    Public opinion and professional organisations dominate the euthanasia debate, and there is a need to understand the opinions of people confronted with euthanasia. The aim of this study was to investigate whether patients and their GPs talk about euthanasia, and if so, how they communicate about this. Qualitative, semi-structured interviews were held with 20 GPs and 30 of their patients in primary care in the Netherlands, where euthanasia is legalised. The patients had a life expectancy of less than 6 months, and cancer, heart failure or chronic obstructive pulmonary disease as underlying disease. Many patients did not communicate about euthanasia with their GP. Neither the patient nor the GP were clear in formulating their expectations concerning future decision making. The initial patient-GP communication consisted of an exchange of opinions about situations in which euthanasia would be desirable. GPs had different opinions about who should initiate communication, and found it difficult to judge the right moment to talk. It is essential to pay attention to education in communication about dying and euthanasia and to train the GPs to gain insight in the patient's end-of-life preferences, and to direct care at the best possible quality of life.

  19. Multi-Satellite MIMO Communications at Ku-Band and Above: Investigations on Spatial Multiplexing for Capacity Improvement and Selection Diversity for Interference Mitigation

    Directory of Open Access Journals (Sweden)

    Liolis Konstantinos P

    2007-01-01

    Full Text Available This paper investigates the applicability of multiple-input multiple-output (MIMO technology to satellite communications at the Ku-band and above. After introducing the possible diversity sources to form a MIMO matrix channel in a satellite environment, particular emphasis is put on satellite diversity. Two specific different topics from the field of MIMO technology applications to satellite communications at these frequencies are further analyzed: (i capacity improvement achieved by MIMO spatial multiplexing systems and (ii interference mitigation achieved by MIMO diversity systems employing receive antenna selection. In the first case, a single-user capacity analysis of a satellite MIMO spatial multiplexing system is presented and a useful analytical closed form expression is derived for the outage capacity achieved. In the second case, a satellite MIMO diversity system with receive antenna selection is considered, adjacent satellite cochannel interference on its forward link is studied and an analytical model predicting the interference mitigation achieved is presented. In both cases, an appropriate physical MIMO channel model is assumed which takes into account the propagation phenomena related to the frequencies of interest, such as clear line-of-sight operation, high antenna directivity, the effect of rain fading, and the slant path lengths difference. Useful numerical results obtained through the analytical expressions derived are presented to compare the performance of multi-satellite MIMO systems to relevant single-input single-output (SISO ones.

  20. A Comparison Study of Communication Skills between General Surgery and General Practice Residents on First-time Patient Visits

    Directory of Open Access Journals (Sweden)

    Ahmed Al Ansari

    2012-04-01

    Full Text Available Background: There is little published research about differences in doctor-patient communication of different specialties. Accordingly, we compared doctor-patient communication skills in two different specialties, general surgery (GS and general practice (GP. Methods: Twenty residents training at the Bahrain Defence Force Hospital (10 men and 10 women; mean age 28 years; 10 GS and 10 GP participated in 200 patient first visit consultations. The consultations were video-recorded and analysed by four trained observers using the MAAS Global scale. Results: 1 Internal consistency reliability of the MAAS Global (> 0.91 and Ep2 = 0.84 for raters was high, 2 GP residents spent more time (12 minutes than GS residents (7 minutes, in the visits, 3 There were several differences on the MAAS Global items between GP and GS residents (GS > GP, p GS, p < 0.05 on information giving, and 4 The present participants performed well compared to normative samples as well as to criterion-referenced cut-off scores. The general level of communication skills in both specialties, however, was ‘unsatisfactory’ and ‘doubtful’, as it is for normative samples. Conclusion: Excellent doctor-patient communication is essential but does not appear to receive the amount of attention that it deserves in practice settings. There are some differences between specialties as well as unsatisfactory communication skills for both specialties, since residents from both programs spent less time than recommended on each consultation. Our findings emphasize the need to improve the communication skills of physicians in general and for surgeons in particular.

  1. An Analysis of Marine Corps Beyond Line of Sight Wideband Satellite Communications Requirements

    Science.gov (United States)

    2010-09-01

    Tactical SHF Satellite Terminal UFO ... what made it bearable. Stephen Musick: Thanks are due to my family and friends for their support and encouragement. I want to especially thank... what beyond LOS WB SATCOM capabilities the USMC requires in order to prepare for the future. A clear understanding of desired capabilities allows for

  2. 78 FR 14920 - Earth Stations Aboard Aircraft Communicating With Fixed-Satellite Service Geostationary-Orbit...

    Science.gov (United States)

    2013-03-08

    ... Consumer and Governmental Affairs Bureau, Reference Information Center shall send a copy of this Report and... ground, ESAAs shall not be authorized for transmission at angles less than 5[deg] measured from the plane..., in the plane of the geostationary satellite orbit (GSO) as it appears at the particular earth station...

  3. Improved Coast Guard Communications Using Commercial Satellites and WWW Technology: Slide Presentation

    Science.gov (United States)

    1997-06-18

    The slides in this file amplify a paper that was presented at International Mobile Satellite Conference, (IMSC-97), Pasadena CA on 18 June 1997. The text of that presentation can be found at http://www.bts.gov/NTL/data/imsc.pdf.

  4. The performance evaluation of a new neural network based traffic management scheme for a satellite communication network

    Science.gov (United States)

    Ansari, Nirwan; Liu, Dequan

    1991-01-01

    A neural-network-based traffic management scheme for a satellite communication network is described. The scheme consists of two levels of management. The front end of the scheme is a derivation of Kohonen's self-organization model to configure maps for the satellite communication network dynamically. The model consists of three stages. The first stage is the pattern recognition task, in which an exemplar map that best meets the current network requirements is selected. The second stage is the analysis of the discrepancy between the chosen exemplar map and the state of the network, and the adaptive modification of the chosen exemplar map to conform closely to the network requirement (input data pattern) by means of Kohonen's self-organization. On the basis of certain performance criteria, whether a new map is generated to replace the original chosen map is decided in the third stage. A state-dependent routing algorithm, which arranges the incoming call to some proper path, is used to make the network more efficient and to lower the call block rate. Simulation results demonstrate that the scheme, which combines self-organization and the state-dependent routing mechanism, provides better performance in terms of call block rate than schemes that only have either the self-organization mechanism or the routing mechanism.

  5. Prediction Method for Rain Rate and Rain Propagation Attenuation for K-Band Satellite Communications Links in Tropical Areas

    Directory of Open Access Journals (Sweden)

    Baso Maruddani

    2015-01-01

    Full Text Available This paper deals with the prediction method using hidden Markov model (HMM for rain rate and rain propagation attenuation for K-band satellite communication link at tropical area. As is well known, the K-band frequency is susceptible of being affected by atmospheric condition, especially in rainy condition. The wavelength of K-band frequency which approaches to the size of rain droplet causes the signal strength is easily attenuated and absorbed by the rain droplet. In order to keep the quality of system performance for K-band satellite communication link, therefore a special attention has to be paid for rain rate and rain propagation attenuation. Thus, a prediction method for rain rate and rain propagation attenuation based on HMM is developed to process the measurement data. The measured and predicted data are then compared with the ITU-R recommendation. From the result, it is shown that the measured and predicted data show similarity with the model of ITU-R P.837-5 recommendation for rain rate and the model of ITU-R P.618-10 recommendation for rain propagation attenuation. Meanwhile, statistical data for measured and predicted data such as fade duration and interfade duration have insignificant discrepancy with the model of ITU-R P.1623-1 recommendation.

  6. A Novel Location-Awareness Method Using CubeSats for Locating the Spot Beam Emitters of Geostationary Communications Satellites

    Directory of Open Access Journals (Sweden)

    Weicai Yang

    2018-01-01

    Full Text Available As more spacecraft are launched into the Geostationary Earth Orbit (GEO belt, the possibility of fatal collisions or unnecessary interference between spacecraft increases. In this paper, a new location-awareness method that uses CubeSats is proposed to assist with radiofrequency (RF domain verification by means of awareness and identification of the positions of the spot beam emitters of communications satellites in geostationary orbit. By flying a CubeSat (or a constellation of CubeSats through the coverage area of a spot beam, the spot beam emitter’s position is identified and the spot beam’s pattern knowledge is characterized. The geometry, the equations of motion of the spacecraft, the measurement process, and the filtering equations in a location system are addressed with respect to the location methods investigated in this study. A realistic scenario in which a CubeSat receives signals from GEO communications satellites is simulated using the Systems Tool Kit (STK. The results of the simulation and the analysis presented in this study provide a thorough verification of the performance of the location-awareness method.

  7. An Optimizing Space Data-Communications Scheduling Method and Algorithm with Interference Mitigation, Generalized for a Broad Class of Optimization Problems

    Science.gov (United States)

    Rash, James

    2014-01-01

    NASA's space data-communications infrastructure-the Space Network and the Ground Network-provide scheduled (as well as some limited types of unscheduled) data-communications services to user spacecraft. The Space Network operates several orbiting geostationary platforms (the Tracking and Data Relay Satellite System (TDRSS)), each with its own servicedelivery antennas onboard. The Ground Network operates service-delivery antennas at ground stations located around the world. Together, these networks enable data transfer between user spacecraft and their mission control centers on Earth. Scheduling data-communications events for spacecraft that use the NASA communications infrastructure-the relay satellites and the ground stations-can be accomplished today with software having an operational heritage dating from the 1980s or earlier. An implementation of the scheduling methods and algorithms disclosed and formally specified herein will produce globally optimized schedules with not only optimized service delivery by the space data-communications infrastructure but also optimized satisfaction of all user requirements and prescribed constraints, including radio frequency interference (RFI) constraints. Evolutionary algorithms, a class of probabilistic strategies for searching large solution spaces, is the essential technology invoked and exploited in this disclosure. Also disclosed are secondary methods and algorithms for optimizing the execution efficiency of the schedule-generation algorithms themselves. The scheduling methods and algorithms as presented are adaptable to accommodate the complexity of scheduling the civilian and/or military data-communications infrastructure within the expected range of future users and space- or ground-based service-delivery assets. Finally, the problem itself, and the methods and algorithms, are generalized and specified formally. The generalized methods and algorithms are applicable to a very broad class of combinatorial

  8. Communication about euthanasia in general practice: opinions and experiences of patients and their general practitioners

    NARCIS (Netherlands)

    Borgsteede, Sander D.; Deliens, Luc; Graafland-Riedstra, Corrie; Francke, Anneke L.; van der Wal, Gerrit; Willems, Dick L.

    2007-01-01

    OBJECTIVE: Public opinion and professional organisations dominate the euthanasia debate, and there is a need to understand the opinions of people confronted with euthanasia. The aim of this study was to investigate whether patients and their GPs talk about euthanasia, and if so, how they communicate

  9. Communication about euthanasia in general practice: opinions and experiences of patients and their general practitioners.

    NARCIS (Netherlands)

    Borgsteede, S.D.; Deliens, L.; Graafland-Riedstra, C.; Francke, A.L.; Wal, G. van der; Willems, D.L.

    2007-01-01

    Public opinion and professional organisations dominate the euthanasia debate, and there is a need to understand the opinions of people confronted with euthanasia. The aim of this study was to investigate whether patients and their GPs talk about euthanasia, and if so, how they communicate about

  10. UHF coplanar-slot antenna for aircraft-to-satellite data communications

    Science.gov (United States)

    Myhre, R. W.

    1979-01-01

    The initiative for starting the Aircraft-to-Satellite Data Relay (ASDAR) Program came from a recognition that much of the world's weather originates in the data sparse area of the tropics which are primarily ocean. The ASDAR system consists of (1) a data acquisition and control unit to acquire, store and format these data; (2) a clock to time the data sampling and transmission periods; and (3) a transmitter and low-profile upper hemisphere coverage antenna to relay the formatted data via satellite to the National Weather Service ground stations, as shown schematically. The low-profile antenna is a conformal antenna based on the coplanar-slot approach. The antenna is circular polarized and has an on-axis gain of nearly 2.5 dB and a HPBW greater than 90 deg. The discussion covers antenna design, radiation characteristics, flight testing, and system performance.

  11. Evolution of the Orbital Elements for Geosynchronous Orbit of Communications Satellite, II

    Directory of Open Access Journals (Sweden)

    Kyu-Hong Choi

    1987-06-01

    Full Text Available For a geostationary satellite north-south station keeping maneuver must control the inclination elements. The effects on the orbit plane of maneuvers and natural perturbations may be represented by a plane plot of Wc versus Ws, since these inclination elements represent the projection of the unit orbit normal onto the equatorial plane. The evolution of the semi-major axis and the inclination elements are obtained.

  12. RAPID COMMUNICATION: Improving prediction accuracy of GPS satellite clocks with periodic variation behaviour

    Science.gov (United States)

    Heo, Youn Jeong; Cho, Jeongho; Heo, Moon Beom

    2010-07-01

    The broadcast ephemeris and IGS ultra-rapid predicted (IGU-P) products are primarily available for use in real-time GPS applications. The IGU orbit precision has been remarkably improved since late 2007, but its clock products have not shown acceptably high-quality prediction performance. One reason for this fact is that satellite atomic clocks in space can be easily influenced by various factors such as temperature and environment and this leads to complicated aspects like periodic variations, which are not sufficiently described by conventional models. A more reliable prediction model is thus proposed in this paper in order to be utilized particularly in describing the periodic variation behaviour satisfactorily. The proposed prediction model for satellite clocks adds cyclic terms to overcome the periodic effects and adopts delay coordinate embedding, which offers the possibility of accessing linear or nonlinear coupling characteristics like satellite behaviour. The simulation results have shown that the proposed prediction model outperforms the IGU-P solutions at least on a daily basis.

  13. Possible experiment with two counter-orbiting drag-free satellites to obtain a new test of Einstein's general theory of relativity and improved measurements in geodesy

    International Nuclear Information System (INIS)

    Van Patten, R.A.; Everitt, C.W.F.

    1976-01-01

    In 1918, Lense and Thirring calculated that a moon orbiting a rotating planet would experience a nodal dragging effect due to general relativity. We describe an experiment to measure this effect to 1% with two counter-orbiting drag-free satellites in polar earth orbit. In addition to tracking data from existing ground stations, satellite-to-satellite Doppler ranging data are taken near the poles. New geophysical information is inherent in the polar data

  14. Communication about euthanasia in general practice: opinions and experiences of patients and their general practitioners.

    OpenAIRE

    Borgsteede, S.D.; Deliens, L.; Graafland-Riedstra, C.; Francke, A.L.; Wal, G. van der; Willems, D.L.

    2007-01-01

    Public opinion and professional organisations dominate the euthanasia debate, and there is a need to understand the opinions of people confronted with euthanasia. The aim of this study was to investigate whether patients and their GPs talk about euthanasia, and if so, how they communicate about this. METHODS: Qualitative, semi-structured interviews were held with 20 GPs and 30 of their patients in primary care in the Netherlands, where euthanasia is legalised. The patients had a life expectan...

  15. Experimental teaching reforms of optical fiber communication based on general education

    Science.gov (United States)

    Lan, L.; Liu, S.; Zhou, J. H.; Peng, Z. M.

    2017-08-01

    It's necessary that higher education experimental teaching reforms on the basis of general education. This paper put forward the experimental teaching reform mode of optical fiber communication in the context of general education. With some reform measures such as improving the experimental content, enriching the experimental style, modifying the experimental teaching method, and adjusting the evaluation method of experimental teaching, the concept of general education is put throughout the experimental teaching of optical fiber communication. In this way, it facilitates the development of students and improvement of experimental teaching quality.

  16. Proceedings of the Twenty-First NASA Propagation Experimenters Meeting (NAPEX XXI) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop

    Science.gov (United States)

    Golshan, Nasser (Editor)

    1997-01-01

    The NASA Propagation Experimenters (NAPEX) meeting is convened each year to discuss studies supported by the NASA Propagation Program. Representatives from the satellite communications industry, academia and government who have an interest in space-ground radio wave propagation are invited to NAPEX meetings for discussions and exchange of information. The reports delivered at this meeting by program managers and investigators present recent activities and future plans. This forum provides an opportunity for peer discussion of work in progress, timely dissemination of propagation results, and close interaction with the satellite communications industry.

  17. Rigorous Line-Based Transformation Model Using the Generalized Point Strategy for the Rectification of High Resolution Satellite Imagery

    Directory of Open Access Journals (Sweden)

    Kun Hu

    2016-09-01

    Full Text Available High precision geometric rectification of High Resolution Satellite Imagery (HRSI is the basis of digital mapping and Three-Dimensional (3D modeling. Taking advantage of line features as basic geometric control conditions instead of control points, the Line-Based Transformation Model (LBTM provides a practical and efficient way of image rectification. It is competent to build the mathematical relationship between image space and the corresponding object space accurately, while it reduces the workloads of ground control and feature recognition dramatically. Based on generalization and the analysis of existing LBTMs, a novel rigorous LBTM is proposed in this paper, which can further eliminate the geometric deformation caused by sensor inclination and terrain variation. This improved nonlinear LBTM is constructed based on a generalized point strategy and resolved by least squares overall adjustment. Geo-positioning accuracy experiments with IKONOS, GeoEye-1 and ZiYuan-3 satellite imagery are performed to compare rigorous LBTM with other relevant line-based and point-based transformation models. Both theoretic analysis and experimental results demonstrate that the rigorous LBTM is more accurate and reliable without adding extra ground control. The geo-positioning accuracy of satellite imagery rectified by rigorous LBTM can reach about one pixel with eight control lines and can be further improved by optimizing the horizontal and vertical distribution of control lines.

  18. Design challenges of a tunable laser interrogator for geo-stationary communication satellites

    Science.gov (United States)

    Ibrahim, Selwan K.; Honniball, Arthur; McCue, Raymond; Todd, Michael; O'Dowd, John A.; Sheils, David; Voudouris, Liberis; Farnan, Martin; Hurni, Andreas; Putzer, Philipp; Lemke, Norbert; Roner, Markus

    2017-09-01

    Recently optical sensing solutions based on fiber Bragg grating (FBG) technology have been proposed for temperature monitoring in telecommunication satellite platforms with an operational life time beyond 15 years in geo-stationary orbit. Developing radiation hardened optical interrogators designed to be used with FBG sensors inscribed in radiation tolerant fibers offer the capabilities of multiplexing multiple sensors on the same fiber and reducing the overall weight by removing the copper wiring harnesses associated with electrical sensors. Here we propose the use of a tunable laser based optical interrogator that uses a semiconductor MG-Y type laser that has no moving parts and sweeps across the C-band wavelength range providing optical power to FBG sensors and optical wavelength references such as athermal Etalons and Gas Cells to guarantee stable operation of the interrogator over its targeted life time in radiation exposed environments. The MG-Y laser was calibrated so it remains in a stable operation mode which ensures that no mode hops occur due to aging of the laser, and/or thermal or radiation effects. The key optical components including tunable laser, references and FBGs were tested for radiation tolerances by emulating the conditions on a geo-stationary satellite including a Total Ionizing Dose (TID) radiation level of up to 100 krad for interrogator components and 25 Mrad for FBGs. Different tunable laser control, and signal processing algorithms have been designed and developed to fit within specific available radiation hardened FPGAs to guarantee operation of a single interrogator module providing at least 1 sample per second measurement capability across engineering model system developed in the frame of an ESA-ARTES program and is planned to be deployed as a flight demonstrator on-board the German Heinrich Hertz geo-stationary satellite.

  19. A Novel Efficient Cluster-Based MLSE Equalizer for Satellite Communication Channels with -QAM Signaling

    Directory of Open Access Journals (Sweden)

    Dalakas Vassilis

    2006-01-01

    Full Text Available In satellites, nonlinear amplifiers used near saturation severely distort the transmitted signal and cause difficulties in its reception. Nevertheless, the nonlinearities introduced by memoryless bandpass amplifiers preserve the symmetries of the -ary quadrature amplitude modulation ( -QAM constellation. In this paper, a cluster-based sequence equalizer (CBSE that takes advantage of these symmetries is presented. The proposed equalizer exhibits enhanced performance compared to other techniques, including the conventional linear transversal equalizer, Volterra equalizers, and RBF network equalizers. Moreover, this gain in performance is obtained at a substantially lower computational cost.

  20. On possible a-priori "imprinting" of General Relativity itself on the performed Lense-Thirring tests with LAGEOS satellites

    Science.gov (United States)

    Iorio, Lorenzo

    2010-02-01

    The impact of possible a-priori "imprinting" effects of general relativity itself on recent attempts to measure the general relativistic Lense-Thirring effect with the LAGEOS satellites orbiting the Earth and the terrestrial geopotential models from the dedicated mission GRACE is investigated. It is analytically shown that general relativity, not explicitly solved for in the GRACE-based models, may "imprint" their even zonal harmonic coefficients of low degrees J_l at a non-negligible level, given the present-day accuracy in recovering them. This translates into a bias of the LAGEOS-based relativistic tests as large as the Lense-Thirring effect itself. Further analyses should include general relativity itself in the GRACE data processing by explicitly solving for it.

  1. Via generalized function projective synchronization in nonlinear Schrödinger equation for secure communication

    Science.gov (United States)

    Zhao, L. W.; Du, J. G.; Yin, J. L.

    2018-05-01

    This paper proposes a novel secured communication scheme in a chaotic system by applying generalized function projective synchronization of the nonlinear Schrödinger equation. This phenomenal approach guarantees a secured and convenient communication. Our study applied the Melnikov theorem with an active control strategy to suppress chaos in the system. The transmitted information signal is modulated into the parameter of the nonlinear Schrödinger equation in the transmitter and it is assumed that the parameter of the receiver system is unknown. Based on the Lyapunov stability theory and the adaptive control technique, the controllers are designed to make two identical nonlinear Schrödinger equation with the unknown parameter asymptotically synchronized. The numerical simulation results of our study confirmed the validity, effectiveness and the feasibility of the proposed novel synchronization method and error estimate for a secure communication. The Chaos masking signals of the information communication scheme, further guaranteed a safer and secured information communicated via this approach.

  2. Distress detection, location, and communications using advanced space technology. [satellite-borne synthetic aperture radar

    Science.gov (United States)

    Sivertson, W. E., Jr.

    1977-01-01

    This paper briefly introduces a concept for low-cost, global, day-night, all-weather disaster warning and assistance. Evolving, advanced space technology with passive radio frequency reflectors in conjunction with an imaging synthetic aperture radar is employed to detect, identify, locate, and provide passive communication with earth users in distress. This concept evolved from a broad NASA research on new global search and rescue techniques. Appropriate airborne radar test results from this research are reviewed and related to potential disaster applications. The analysis indicates the approach has promise for disaster communications relative to floods, droughts, earthquakes, volcanic eruptions, and severe storms.

  3. Communication Collocations of the Lexeme Geld in General and Business German

    Directory of Open Access Journals (Sweden)

    Mirna Hocenski-Dreiseidl

    2010-07-01

    Full Text Available The authors aim to analyse and compare the lexeme Geld and its collocations on the grammatical and semantic levels in general and in business German. A special emphasis will be put on the importance of the communicative function that this lexeme and its collocations have in the language of banking. The paper also has a practical purpose. Its applicability in teaching is envisaged to improve the communicative competence of students of economics.

  4. Communication and general concern criterion prior to activation of the rapid response team: a grounded theory.

    Science.gov (United States)

    Martland, Jarrad; Chamberlain, Diane; Hutton, Alison; Smigielski, Michael

    2016-11-01

    Objective Patients commonly show signs and symptoms of deterioration for hours or days before cardiorespiratory arrest. Rapid response teams (RRT) were created to improve recognition and response to patient deterioration in these situations. Activation criteria include vital signs or 'general concern' by a clinician or family member. The general concern criterion for RRT activation accounts for nearly one-third of all RRT activity, and although it is well established that communication deficits between staff can contribute to poorer outcomes for patients, there is little evidence pertaining to communication and its effects on the general concern RRT activation. Thus, the aim of the present study was to develop a substantive grounded theory related to the communication process between clinicians that preceded the activation of an RRT when general concern criterion was used. Methods Qualitative grounded theory involved collection of three types of data details namely personal notes from participants in focus groups with white board notes from discussions and audio recordings of the focus groups sessions. Focus groups were conducted with participants exploring issues associated with clinician communication and how it related to the activation of an RRT using the general concern criterion. Results The three main phases of coding (i.e. open, axial and selective coding) analysis identified 322 separate open codes. The strongest theme contributed to a theory of ineffective communication and decreased psychological safety, namely that 'In the absence of effective communication there is a subsequent increase in anxiety, fear or concern that can be directly attributed to the activation of an RRT using the 'general concern' criterion'. The RRT filled cultural and process deficiencies in the compliance with an escalation protocol. Issues such as 'not for resuscitation documentation' and 'inability to establish communication with and between medical or nursing personnel' rated

  5. Burst Format Design for Optimum Joint Estimation of Doppler-Shift and Doppler-Rate in Packet Satellite Communications

    Directory of Open Access Journals (Sweden)

    Luca Giugno

    2007-05-01

    Full Text Available This paper considers the problem of optimizing the burst format of packet transmission to perform enhanced-accuracy estimation of Doppler-shift and Doppler-rate of the carrier of the received signal, due to relative motion between the transmitter and the receiver. Two novel burst formats that minimize the Doppler-shift and the Doppler-rate Cramér-Rao bounds (CRBs for the joint estimation of carrier phase/Doppler-shift and of the Doppler-rate are derived, and a data-aided (DA estimation algorithm suitable for each optimal burst format is presented. Performance of the newly derived estimators is evaluated by analysis and by simulation, showing that such algorithms attain their relevant CRBs with very low complexity, so that they can be directly embedded into new-generation digital modems for satellite communications at low SNR.

  6. Cross-polarisation discrimination-induced interference in dual-polarised high-capacity satellite communication systems

    Directory of Open Access Journals (Sweden)

    Abdulkareem Sarki Karasuwa

    2016-05-01

    Full Text Available The design of spectrally-efficient, high-throughput satellite (HTS systems with capacity approaching one terabit per second requires operating at Ka-band frequencies and above, where there are several gigahertz of allocated radio spectrum, using multiple spot beams with dual orthogonal polarisation mode. At these high frequencies, rain attenuation poses a major obstacle to the design of high-availability satellite links which are needed for the realisation of ubiquitous broadband multimedia communication services including high-speed Internet access at rural and remote locations. Furthermore, depolarisation-induced interference in such systems could have a performance-limiting impact if a co-channel cross-polar signal combines with system noise to drive the carrier-to-noise-plus-interference ratio (CNIR below an acceptable threshold. This paper employs real measurement data to investigate the impact of depolarisation-induced interference on dual-polarised HTS systems for temperate and tropical climatic regions. Scenarios that cause significant system performance degradation are analysed, including the effects of signal frequency, antenna size, and regional rainfall rate. The impact of depolarisation on system performance is quantified by the reductions in the CNIR and link availability of a dual-polarised system when compared with those of a similarly-dimensioned single-polarised system.

  7. Communication Skills in Dental Students: New Data Regarding Retention and Generalization of Training Effects.

    Science.gov (United States)

    Broder, Hillary L; Janal, Malvin; Mitnick, Danielle M; Rodriguez, Jasmine Y; Sischo, Lacey

    2015-08-01

    Previous studies have shown that a communications program using patient instructors (PIs) facilitates data-gathering and interpersonal skills of third-year dental students. The aim of this study was to address the question of whether those skills are retained into the students' fourth year and generalized from the classroom to the clinic. In the formative training phase, three cohorts of D3 students (N=1,038) at one dental school received instruction regarding effective patient-doctor communication; interviewed three PIs and received PI feedback; and participated in a reflective seminar with a behavioral science instructor. In the follow-up competency phase, fourth-year students performed two new patient interviews in the clinic that were observed and evaluated by clinical dental faculty members trained in communications. Mean scores on a standardized communications rating scale and data-gathering assessment were compared over training and follow-up sessions and between cohorts with a linear mixed model. The analysis showed that the third-year students' mean communication and data-gathering scores increased with each additional encounter with a PI (pcommunication scores were not only maintained but increased during the fourth-year follow-up competency evaluations (pcommunications curriculum, prior instruction facilitated the students' clinical communication performance at baseline (pCommunications program improved students' data-gathering and interpersonal skills. Those skills were maintained and generalized through completion of the D4 students' summative competency performance in a clinical setting.

  8. The HSBQ Algorithm with Triple-play Services for Broadband Hybrid Satellite Constellation Communication System

    Directory of Open Access Journals (Sweden)

    Anupon Boriboon

    2016-07-01

    Full Text Available The HSBQ algorithm is the one of active queue management algorithms, which orders to avoid high packet loss rates and control stable stream queue. That is the problem of calculation of the drop probability for both queue length stability and bandwidth fairness. This paper proposes the HSBQ, which drop the packets before the queues overflow at the gateways, so that the end nodes can respond to the congestion before queue overflow. This algorithm uses the change of the average queue length to adjust the amount by which the mark (or drop probability is changed. Moreover it adjusts the queue weight, which is used to estimate the average queue length, based on the rate. The results show that HSBQ algorithm could maintain control stable stream queue better than group of congestion metric without flow information algorithm as the rate of hybrid satellite network changing dramatically, as well as the presented empiric evidences demonstrate that the use of HSBQ algorithm offers a better quality of service than the traditionally queue control mechanisms used in hybrid satellite network.

  9. Evidence that communication impairment in schizophrenia is associated with generalized poor task performance.

    Science.gov (United States)

    Merrill, Anne M; Karcher, Nicole R; Cicero, David C; Becker, Theresa M; Docherty, Anna R; Kerns, John G

    2017-03-01

    People with schizophrenia exhibit wide-ranging cognitive deficits, including slower processing speed and decreased cognitive control. Disorganized speech symptoms, such as communication impairment, have been associated with poor cognitive control task performance (e.g., goal maintenance and working memory). Whether communication impairment is associated with poorer performance on a broader range of non-cognitive control measures is unclear. In the current study, people with schizophrenia (n =51) and non-psychiatric controls (n =26) completed speech interviews allowing for reliable quantitative assessment of communication impairment. Participants also completed multiple goal maintenance and working memory tasks. In addition, we also examined (a) simple measures of processing speed involving highly automatic prepotent responses and (b) a non-cognitive control measure of general task performance. Schizophrenia communication impairment was significantly associated with poor performance in all cognitive domains, with the largest association found with processing speed (r s =-0.52). Further, communication impairment was also associated with the non-cognitive control measure of poor general task performance (r s =-0.43). In contrast, alogia, a negative speech symptom, and positive symptoms were less if at all related to cognitive task performance. Overall, this study suggests that communication impairment in schizophrenia may be associated with relatively generalized poor cognitive task performance. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

  10. Improving information dissemination in sparse vehicular networks by adding satellite communication

    NARCIS (Netherlands)

    Kloiber, Bernhard; Strang, Thomas; Spijker, Hanno; Heijenk, Geert

    Information dissemination in pure Vehicular Ad Hoc NETworks (VANETs) such as ITS-G5 becomes problematic when the network is sparse. In situations where the number of vehicles, that can act as a communication node, is insufficiently low, e.g. in rural areas, during night-time or because of a low

  11. DAS photonics developments for analogue and digital photonic links for intra-satellite communications

    Science.gov (United States)

    Blasco, Julián.; Rico, Eloy; Genovard, Pablo; Sáez, Cristina; Navasquillo, Olga; Martí, Javier

    2017-11-01

    During past years, special efforts have been invested to develop optical links, both digital and analogue, for space applications, such as reference signal distribution or digital communication cables. The aim of this paper is to present the current DAS developments for these applications as well as future work to increase TRL levels and flight opportunities.

  12. 78 FR 14952 - Earth Stations Aboard Aircraft Communicating with Fixed-Satellite Service Geostationary-Orbit...

    Science.gov (United States)

    2013-03-08

    ... FEDERAL COMMUNICATIONS COMMISSION 47 CFR Part 2 [IB Docket No. 12-376; FCC 12-161] Earth Stations... (NPRM) seeks comment on a proposal to elevate the allocation status of Earth Stations Aboard Aircraft... with GSO space stations of the FSS on a primary basis in the 11.7-12.2 GHz band (space-to-Earth), on an...

  13. TYCHO: Demonstrator and operational satellite mission to Earth-Moon-Libration point EML-4 for communication relay provision as a service

    Science.gov (United States)

    Hornig, Andreas; Homeister, Maren

    2015-03-01

    In the current wake of mission plans to the Moon and to Earth-Moon Libration points (EML) by several agencies and organizations, TYCHO identifies the key role of telecommunication provision for the future path of lunar exploration. It demonstrates an interesting extension to existing communication methods to the Moon and beyond by combining innovative technology with a next frontier location and the commercial space communication sector. It is evident that all communication systems will rely on direct communication to Earth ground stations. In case of EML-2 missions around HALO orbits or bases on the far side of the Moon, it has to be extended by communication links via relay stations. The innovative approach is that TYCHO provides this relay communication to those out-of-sight lunar missions as a service. TYCHO will establish a new infrastructure for future missions and even create a new market for add-on relay services. The TMA-0 satellite is TYCHO's first phase and a proposed demonstrator mission to the Earth-Moon Libration point EML-4. It demonstrates relay services needed for automated exploratory and manned missions (Moon bases) on the rim (>90°E and >90°W) and far side surface, to lunar orbits and even to EML-2 halo orbits (satellites and space stations). Its main advantage is the permanent availability of communication coverage. This will provide full access to scientific and telemetry data and furthermore to crucial medical monitoring and safety. The communication subsystem is a platform for conventional communication but also a test-bed for optical communication with high data-rate LASER links to serve the future needs of manned bases and periodic burst data-transfer from lunar poles. The operational TMA-1 satellite is a stand-alone mission integrated into existing space communication networks to provide open communication service to external lunar missions. Therefore the long-time stable libration points EML-4 and -5 are selected to guarantee an

  14. Experiments on the quick-relief medical communications via the Japan's domestic communication satellite CS-2 for the case of disasters and emergencies.

    Science.gov (United States)

    Otsu, Y; Choh, T; Yamazaki, I; Kosaka, K; Iguchi, M; Nakajima, I

    1986-01-01

    Experiments on the quick-relief medical communications via the CS-2 satellite were carried out by using two types of 30/20 GHz small transportable earth stations whose antenna diameters are 1 and 2 m. As the terminal equipments, FM-SCPC systems with a one-telephone-equivalent channel were prepared for the transmission of voice, color freezed picture (9.6 kbps), supersonic echo signal and heart sound from a electrocardiograph. Signals from various medical equipments were transmitted by an FM-SCPC system from Simizu harbour (1 m station) to Tokyo transportable station (2 m), assuming that a person was injured in the ship and the ship came alongside the pier. Transmitted materials are mainly various kinds of pictures of affected parts, X-ray films and electrocardiograph with breathing sounds. It was found possible to send various medical information mentioned above via CS-2 by the 30/20 GHz simple communication systems with one-telephone-equivalent channel. Doctors suggested it would be possible to judge very well about the patients' emergency conditions and to give quick consult with inevitable treatment procedures for them. However, a few problems were found in the Hi-Fi reproduction of original colors and in the transmission of heart sounds in the very low frequency band less than 300 Hz.

  15. Retrieving the polarization information for satellite-to-ground light communication

    International Nuclear Information System (INIS)

    Tao, Qiangqiang; Guo, Zhongyi; Xu, Qiang; Gao, Jun; Jiao, Weiyan; Wang, Xinshun; Qu, Shiliang

    2015-01-01

    In this paper, we have investigated the reconstruction of the polarization states (degree of polarization (DoP) and angle of polarization (AoP)) of the incident light which passed through a 10 km atmospheric medium between the satellite and the Earth. Here, we proposed a more practical atmospheric model in which the 10 km atmospheric medium is divided into ten layers to be appropriate for the Monte Carlo simulation algorithm. Based on this model, the polarization retrieve (PR) method can be used for reconstructing the initial polarization information effectively, and the simulated results demonstrate that the mean errors of the retrieved DoP and AoP are very close to zero. Moreover, the results also show that although the atmospheric medium system is fixed, the Mueller matrices for the downlink and uplink are completely different, which shows that the light transmissions in the two links are irreversible in the layered atmospheric medium system. (paper)

  16. System capacity and economic modeling computer tool for satellite mobile communications systems

    Science.gov (United States)

    Wiedeman, Robert A.; Wen, Doong; Mccracken, Albert G.

    1988-01-01

    A unique computer modeling tool that combines an engineering tool with a financial analysis program is described. The resulting combination yields a flexible economic model that can predict the cost effectiveness of various mobile systems. Cost modeling is necessary in order to ascertain if a given system with a finite satellite resource is capable of supporting itself financially and to determine what services can be supported. Personal computer techniques using Lotus 123 are used for the model in order to provide as universal an application as possible such that the model can be used and modified to fit many situations and conditions. The output of the engineering portion of the model consists of a channel capacity analysis and link calculations for several qualities of service using up to 16 types of earth terminal configurations. The outputs of the financial model are a revenue analysis, an income statement, and a cost model validation section.

  17. Assessing written communication during interhospital transfers of emergency general surgery patients.

    Science.gov (United States)

    Harl, Felicity N R; Saucke, Megan C; Greenberg, Caprice C; Ingraham, Angela M

    2017-06-15

    Poor communication causes fragmented care. Studies of transitions of care within a hospital and on discharge suggest significant communication deficits. Communication during transfers between hospitals has not been well studied. We assessed the written communication provided during interhospital transfers of emergency general surgery patients. We hypothesized that patients are transferred with incomplete documentation from referring facilities. We performed a retrospective review of written communication provided during interhospital transfers to our emergency department (ED) from referring EDs for emergency general surgical evaluation between January 1, 2014 and January 1, 2016. Elements of written communication were abstracted from referring facility documents scanned into the medical record using a standardized abstraction protocol. Descriptive statistics summarized the information communicated. A total of 129 patients met inclusion criteria. 87.6% (n = 113) of charts contained referring hospital documents. 42.5% (n = 48) were missing history and physicals. Diagnoses were missing in 9.7% (n = 11). Ninety-one computed tomography scans were performed; among 70 with reads, final reads were absent for 70.0% (n = 49). 45 ultrasounds and x-rays were performed; among 27 with reads, final reads were missing for 80.0% (n = 36). Reasons for transfer were missing in 18.6% (n = 21). Referring hospital physicians outside the ED were consulted in 32.7% (n = 37); consultants' notes were absent in 89.2% (n = 33). In 12.4% (n = 14), referring documents arrived after the patient's ED arrival and were not part of the original documentation provided. This study documents that information important to patient care is often missing in the written communication provided during interhospital transfers. This gap affords a foundation for standardizing provider communication during interhospital transfers. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. Method of Performance-Aware Security of Unicast Communication in Hybrid Satellite Networks

    Science.gov (United States)

    Roy-Chowdhury, Ayan (Inventor); Baras, John S. (Inventor)

    2014-01-01

    A method and apparatus utilizes Layered IPSEC (LES) protocol as an alternative to IPSEC for network-layer security including a modification to the Internet Key Exchange protocol. For application-level security of web browsing with acceptable end-to-end delay, the Dual-mode SSL protocol (DSSL) is used instead of SSL. The LES and DSSL protocols achieve desired end-to-end communication security while allowing the TCP and HTTP proxy servers to function correctly.

  19. Next Generation Satellite Communications: Automated Doppler Shift Compensation of PSK-31 Via Software-Defined Radio

    Science.gov (United States)

    2014-05-09

    of wireless communications. One such development was the superheterodyne principle, which was discovered by amateur radio operator Edwin Armstrong in...synchronous: the same number of samples that enter the block will leave the block. Examples include filters, math operators and phase- locked loops...phase- locked loop (PLL) was used to determine the subcarrier frequency. The PLL tracks the error between the incoming frequency and the output

  20. Communicating cardiovascular disease risk: an interview study of General Practitioners' use of absolute risk within tailored communication strategies.

    Science.gov (United States)

    Bonner, Carissa; Jansen, Jesse; McKinn, Shannon; Irwig, Les; Doust, Jenny; Glasziou, Paul; McCaffery, Kirsten

    2014-05-29

    Cardiovascular disease (CVD) prevention guidelines encourage assessment of absolute CVD risk - the probability of a CVD event within a fixed time period, based on the most predictive risk factors. However, few General Practitioners (GPs) use absolute CVD risk consistently, and communication difficulties have been identified as a barrier to changing practice. This study aimed to explore GPs' descriptions of their CVD risk communication strategies, including the role of absolute risk. Semi-structured interviews were conducted with a purposive sample of 25 GPs in New South Wales, Australia. Transcribed audio-recordings were thematically coded, using the Framework Analysis method to ensure rigour. GPs used absolute CVD risk within three different communication strategies: 'positive', 'scare tactic', and 'indirect'. A 'positive' strategy, which aimed to reassure and motivate, was used for patients with low risk, determination to change lifestyle, and some concern about CVD risk. Absolute risk was used to show how they could reduce risk. A 'scare tactic' strategy was used for patients with high risk, lack of motivation, and a dismissive attitude. Absolute risk was used to 'scare' them into taking action. An 'indirect' strategy, where CVD risk was not the main focus, was used for patients with low risk but some lifestyle risk factors, high anxiety, high resistance to change, or difficulty understanding probabilities. Non-quantitative absolute risk formats were found to be helpful in these situations. This study demonstrated how GPs use three different communication strategies to address the issue of CVD risk, depending on their perception of patient risk, motivation and anxiety. Absolute risk played a different role within each strategy. Providing GPs with alternative ways of explaining absolute risk, in order to achieve different communication aims, may improve their use of absolute CVD risk assessment in practice.

  1. Perceived barriers and facilitators for general practitioner-patient communication in palliative care: a systematic review.

    Science.gov (United States)

    Slort, W; Schweitzer, B P M; Blankenstein, A H; Abarshi, E A; Riphagen, I I; Echteld, M A; Aaronson, N K; van der Horst, He; Deliens, L

    2011-09-01

    While effective general practitioner (GP)-patient communication is required for the provision of good palliative care, barriers and facilitators for this communication are largely unknown. We aimed to identify barriers and facilitators for GP-patient communication in palliative care. In a systematic review seven computerized databases were searched to find empirical studies on GP-patient communication in palliative care. Fifteen qualitative studies and seven quantitative questionnaire studies were included. The main perceived barriers were GPs' lack of availability, and patients' and GPs' ambivalence to discuss 'bad prognosis'. Main perceived facilitators were GPs being available, initiating discussion about several end-of-life issues and anticipating various scenarios. Lack of availability and failure to discuss former mistakes appear to be blind spots of GPs. GPs should be more forthcoming to initiate discussions with palliative care patients about prognosis and end-of-life issues. Empirical studies are needed to investigate the effectiveness of the perceived barriers and facilitators.

  2. Communication between general practitioners and the emergency medical dispatch centre in urgent cases

    DEFF Research Database (Denmark)

    Mieritz, Hanne Beck; Rønnow, Camilla; Jørgensen, Gitte

    2018-01-01

    , and we found that these calls were more likely to contain problematic communication (odds ratio = 5.1). In 18% (n = 236) of the cases, there was not sufficient information to assess if the physician-manned mobile emergency care unit (MECU) should have been dispatched along with the ambulance......INTRODUCTION: When general practitioners (GPs) order an ambulance, their calls are handled by staff at the emergency medical dispatch centre (EMDC) who then select an appropriate response. There are currently no data evaluating this mode of communication between the GPs and the staff at the EMDC....... 
RESULTS: We found problematic communication in less than 2% (n = 25) of the evaluated calls. In 68% of the 25 problematic cases transactional analysis showed that the staff at the EMDC initiated the problematic communication. In 4% (n = 51) of the calls, the GP delegated the call to a secretary or nurse...

  3. Vocational trainees' views and experiences regarding the learning and teaching of communication skills in general practice.

    Science.gov (United States)

    Van Nuland, Marc; Thijs, Gabie; Van Royen, Paul; Van den Noortgate, Wim; Goedhuys, Jo

    2010-01-01

    To explore the views and experiences of general practice (GP) vocational trainees regarding communication skills (CS) and the teaching and learning of these skills. A purposive sample of second and third (final) year GP trainees took part in six focus group (FG) discussions. Transcripts were coded and analysed in accordance with a grounded theory approach by two investigators using Alas-ti software. Finally results were triangulated by means of semi-structured telephone interviews. The analysis led to three thematic clusters: (1) trainees acknowledge the essential importance of communication skills and identified contextual factors influencing the learning and application of these skills; (2) trainees identified preferences for learning and receiving feedback on their communication skills; and (3) trainees perceived that the assessment of communication skills is subjective. These themes are organised into a framework for a better understanding of trainees' communication skills as part of their vocational training. The framework helps in leading to a better understanding of the way in which trainees learn and apply communication skills. The unique context of vocational training should be taken into account when trainees' communication skills are assessed. The teaching and learning should be guided by a learner-centred approach. The framework is valuable for informing curricular reform and future research.

  4. Global-scale Observations of the Limb and Disk (GOLD) Mission: Science from Geostationary Orbit on-board a Commercial Communications Satellite

    Science.gov (United States)

    Eastes, R.; Deaver, T.; Krywonos, A.; Lankton, M. R.; McClintock, W. E.; Pang, R.

    2011-12-01

    Geostationary orbits are ideal for many science investigations of the Earth system on global scales. These orbits allow continuous observations of the same geographic region, enabling spatial and temporal changes to be distinguished and eliminating the ambiguity inherent to observations from low Earth orbit (LEO). Just as observations from geostationary orbit have revolutionized our understanding of changes in the troposphere, they will dramatically improve our understanding of the space environment at higher altitudes. However, geostationary orbits are infrequently used for science missions because of high costs. Geostationary satellites are large, typically weighing tons. Consequently, devoting an entire satellite to a science mission requires a large financial commitment, both for the spacecraft itself and for sufficient science instrumentation to justify a dedicated spacecraft. Furthermore, the small number of geostationary satellites produced for scientific missions increases the costs of each satellite. For these reasons, it is attractive to consider flying scientific instruments on satellites operated by commercial companies, some of whom have fleets of ~40 satellites. However, scientists' lack of understanding of the capabilities of commercial spacecraft as well as commercial companies' concerns about risks to their primary mission have impeded the cooperation necessary for the shared use of a spacecraft. Working with a commercial partner, the GOLD mission has successfully overcome these issues. Our experience indicates that there are numerous benefits to flying on commercial communications satellites (e.g., it is possible to downlink large amounts of data) and the costs are low if the experimental requirements adequately match the capabilities and available resources of the host spacecraft. Consequently, affordable access to geostationary orbit aboard a communications satellite now appears possible for science payloads.

  5. The Relations between Parents' Smoking, General Parenting, Parental Smoking Communication, and Adolescents' Smoking

    Science.gov (United States)

    Harakeh, Zeena; Scholte, Ron H. J.; Vermulst, Ad A.; de Vries, Hein; Engels, Rutger C. M. E.

    2010-01-01

    The present study examined whether the associations between general parenting practices (i.e., support, behavioral control, and psychological control) and parental smoking on the one hand and older and younger siblings' smoking on the other were mediated by parental smoking communication (i.e., frequency and quality of parent-adolescent…

  6. Chaos and Crisis: Propositions for a General Theory of Crisis Communication.

    Science.gov (United States)

    Seeger, Matthew W.

    2002-01-01

    Presents key concepts of chaos theory (CT) as a general framework for describing organizational crisis and crisis communication. Discusses principles of predictability, sensitive dependence on initial conditions, bifurcation as system breakdown, emergent self-organization, and fractals and strange attractors as principles of organization. Explores…

  7. Breaking projective chaos synchronization secure communication using filtering and generalized synchronization

    International Nuclear Information System (INIS)

    Alvarez, G.; Li Shujun; Montoya, F.; Pastor, G.; Romera, M.

    2005-01-01

    This paper describes the security weaknesses of a recently proposed secure communication method based on chaotic masking using projective synchronization of two chaotic systems. We show that the system is insecure and how to break it in two different ways, by high-pass filtering and by generalized synchronization

  8. A Small Ku-Band Polarization Tracking Active Phased Array for Mobile Satellite Communications

    Directory of Open Access Journals (Sweden)

    Wei Shi

    2013-01-01

    Full Text Available A compact polarization tracking active phased array for Ku-band mobile satellite signal reception is presented. In contrast with conventional mechanically tracking antennas, the approach presented here meets the requirements of beam tracking and polarization tracking simultaneously without any servo components. The two-layer stacked square patch fed by two probes is used as antenna element. The impedance bandwidth of 16% for the element covers the operating frequency range from 12.25 GHz to 12.75 GHz. In the presence of mutual coupling, the dimensional parameters for each element of the small 7 × 7 array are optimized during beam scanning and polarization tracking. The compact polarization tracking modules based on the low-temperature cofired ceramic (LTCC system-in-package (SiP technology are proposed. A small active phased array prototype with the size of 120 mm (length × 120 mm (width × 55 mm (height is developed. The measured polarization tracking patterns of the prototype are given. The polarization tracking beam can be steered in the elevation up to 50°. The gain of no less than 16.0 dBi and the aperture efficiency of more than 50% are obtained. The measured and simulated polarization tracking patterns agreed well.

  9. Design and implementation of the next generation Landsat satellite communications system

    Science.gov (United States)

    Mah, Grant R.; O'Brien, Michael; Garon, Howard; Mott, Claire; Ames, Alan; Dearth, Ken

    2012-01-01

    The next generation Landsat satellite, Landsat 8 (L8), also known as the Landsat Data Continuity Mission (LDCM), uses a highly spectrally efficient modulation and data formatting approach to provide large amounts of downlink (D/L) bandwidth in a limited X-Band spectrum allocation. In addition to purely data throughput and bandwidth considerations, there were a number of additional constraints based on operational considerations for prevention of interference with the NASA Deep-Space Network (DSN) band just above the L8 D/L band, minimization of jitter contributions to prevent impacts to instrument performance, and the need to provide an interface to the Landsat International Cooperator (IC) community. A series of trade studies were conducted to consider either X- or Ka-Band, modulation type, and antenna coverage type, prior to the release of the request for proposal (RFP) for the spacecraft. Through use of the spectrally efficient rate-7/8 Low-Density Parity-Check error-correction coding and novel filtering, an XBand frequency plan was developed that balances all the constraints and considerations, while providing world-class link performance, fitting 384 Mbits/sec of data into the 375 MHz X-Band allocation with bit-error rates better than 10-12 using an earth-coverage antenna.

  10. Satellite interference analysis and simulation using personal computers

    Science.gov (United States)

    Kantak, Anil

    1988-03-01

    This report presents the complete analysis and formulas necessary to quantify the interference experienced by a generic satellite communications receiving station due to an interfering satellite. Both satellites, the desired as well as the interfering satellite, are considered to be in elliptical orbits. Formulas are developed for the satellite look angles and the satellite transmit angles generally related to the land mask of the receiving station site for both satellites. Formulas for considering Doppler effect due to the satellite motion as well as the Earth's rotation are developed. The effect of the interfering-satellite signal modulation and the Doppler effect on the power received are considered. The statistical formulation of the interference effect is presented in the form of a histogram of the interference to the desired signal power ratio. Finally, a computer program suitable for microcomputers such as IBM AT is provided with the flowchart, a sample run, results of the run, and the program code.

  11. Study of LiTiMg-ferrite radome for the application of satellite communication

    International Nuclear Information System (INIS)

    Saxena, Naveen Kumar; Kumar, Nitendar; Pourush, P.K.S.

    2010-01-01

    In this paper the characteristics of LiTiMg-ferrite radome are presented. A thin layer of LiTiMg-ferrite is used as superstrate or radome, which controls the radiation, reception, and scattering from a printed antenna or array by applying a dc magnetic bias field in the plane of the ferrite, orthogonal to the RF magnetic field. In this analysis absorbing and transmission power coefficients are calculated to obtain the power loss and transmitted power through the radome layer respectively. The absorbing power coefficient verifies the switching behavior of radome for certain range of applied external magnetic field (Ho), which depends on the resonance width parameter (ΔH) of ferrite material. By properly choosing the bias field, electromagnetic wave propagation in the ferrite layer can be made zero or negligible over a certain frequency range, resulting in switching behavior of the ferrite layer. In this communication we also show precise preparation of radome layer and present its electric and magnetic properties along with its Curie temperature, which shows the working efficiency of layer under extreme situation. This radome layer can be very useful for the sensitive and smart communication systems.

  12. Detection of Convective Initiation Using Meteorological Imager Onboard Communication, Ocean, and Meteorological Satellite Based on Machine Learning Approaches

    Directory of Open Access Journals (Sweden)

    Hyangsun Han

    2015-07-01

    Full Text Available As convective clouds in Northeast Asia are accompanied by various hazards related with heavy rainfall and thunderstorms, it is very important to detect convective initiation (CI in the region in order to mitigate damage by such hazards. In this study, a novel approach for CI detection using images from Meteorological Imager (MI, a payload of the Communication, Ocean, and Meteorological Satellite (COMS, was developed by improving the criteria of the interest fields of Rapidly Developing Cumulus Areas (RDCA derivation algorithm, an official CI detection algorithm for Multi-functional Transport SATellite-2 (MTSAT-2, based on three machine learning approaches—decision trees (DT, random forest (RF, and support vector machines (SVM. CI was defined as clouds within a 16 × 16 km window with the first detection of lightning occurrence at the center. A total of nine interest fields derived from visible, water vapor, and two thermal infrared images of MI obtained 15–75 min before the lightning occurrence were used as input variables for CI detection. RF produced slightly higher performance (probability of detection (POD of 75.5% and false alarm rate (FAR of 46.2% than DT (POD of 70.7% and FAR of 46.6% for detection of CI caused by migrating frontal cyclones and unstable atmosphere. SVM resulted in relatively poor performance with very high FAR ~83.3%. The averaged lead times of CI detection based on the DT and RF models were 36.8 and 37.7 min, respectively. This implies that CI over Northeast Asia can be forecasted ~30–45 min in advance using COMS MI data.

  13. Implementation of a light-route TDMA communications satellite system for advanced business networks

    Science.gov (United States)

    Hanson, B.; Smalley, A.; Zuliani, M.

    The application of Light Route TDMA systems to various business communication requirements is discussed. It is noted that full development of this technology for use in advanced business networks will be guided by considerations of flexibility, reliability, security, and cost. The implementation of the TDMA system for demonstrating these advantages to a wide range of public and private organizations is described in detail. Among the advantages offered by this system are point-to-point and point-to-multipoint (broadcast) capability; the ability to vary the mix and quantity of services between destinations in a fully connected mesh network on an almost instantaneous basis through software control; and enhanced reliability with centralized monitor, alarm and control functions by virtue of an overhead channel.

  14. Interprofessional communication with hospitalist and consultant physicians in general internal medicine: a qualitative study

    Directory of Open Access Journals (Sweden)

    Gotlib Conn Lesley

    2012-11-01

    Full Text Available Abstract Background Studies in General Internal Medicine [GIM] settings have shown that optimizing interprofessional communication is important, yet complex and challenging. While the physician is integral to interprofessional work in GIM there are often communication barriers in place that impact perceptions and experiences with the quality and quantity of their communication with other team members. This study aims to understand how team members’ perceptions and experiences with the communication styles and strategies of either hospitalist or consultant physicians in their units influence the quality and effectiveness of interprofessional relations and work. Methods A multiple case study methodology was used. Thirty-one semi-structured interviews were conducted with physicians, nurses and other health care providers [e.g. physiotherapist, social worker, etc.] working across 5 interprofessional GIM programs. Questions explored participants’ experiences with communication with all other health care providers in their units, probing for barriers and enablers to effective interprofessional work, as well as the use of communication tools or strategies. Observations in GIM wards were also conducted. Results Three main themes emerged from the data: [1] availability for interprofessional communication, [2] relationship-building for effective communication, and [3] physician vs. team-based approaches. Findings suggest a significant contrast in participants’ experiences with the quantity and quality of interprofessional relationships and work when comparing the communication styles and strategies of hospitalist and consultant physicians. Hospitalist staffed GIM units were believed to have more frequent and higher caliber interprofessional communication and collaboration, resulting in more positive experiences among all health care providers in a given unit. Conclusions This study helps to improve our understanding of the collaborative environment

  15. Interfacility Transfers to General Pediatric Floors: A Qualitative Study Exploring the Role of Communication.

    Science.gov (United States)

    Rosenthal, Jennifer L; Okumura, Megumi J; Hernandez, Lenore; Li, Su-Ting T; Rehm, Roberta S

    2016-01-01

    Children with special health care needs often require health services that are only provided at subspecialty centers. Such children who present to nonspecialty hospitals might require a hospital-to-hospital transfer. When transitioning between medical settings, communication is an integral aspect that can affect the quality of patient care. The objectives of the study were to identify barriers and facilitators to effective interfacility pediatric transfer communication to general pediatric floors from the perspectives of referring and accepting physicians, and then develop a conceptual model for effective interfacility transfer communication. This was a single-center qualitative study using grounded theory methodology. Referring and accepting physicians of children with special health care needs were interviewed. Four researchers coded the data using ATLAS.ti (version 7, Scientific Software Development GMBH, Berlin, Germany), using a 2-step process of open coding, followed by focused coding until no new codes emerged. The research team reached consensus on the final major categories and subsequently developed a conceptual model. Eight referring and 9 accepting physicians were interviewed. Theoretical coding resulted in 3 major categories: streamlined transfer process, quality handoff and 2-way communication, and positive relationships between physicians across facilities. The conceptual model unites these categories and shows how these categories contribute to effective interfacility transfer communication. Proposed interventions involved standardizing the communication process and incorporating technology such as telemedicine during transfers. Communication is perceived to be an integral component of interfacility transfers. We recommend that transfer systems be re-engineered to make the process more streamlined, to improve the quality of the handoff and 2-way communication, and to facilitate positive relationships between physicians across facilities. Copyright

  16. A Generalized Visual Aid System for Teleoperation Applied to Satellite Servicing

    Directory of Open Access Journals (Sweden)

    Guoliang Zhang

    2014-02-01

    Full Text Available This paper presents the latest results of a newly developed visual aid system for direct teleoperation. This method is extended to visual control to make an efficient teleoperation system by combining direct teleoperation and automatic control. On the one hand, an operator can conduct direct teleoperation with 3D graphic prediction simulation established by the VR technique. In order to remove inconsistencies between the virtual and real environments, a practical model-matching method is investigated. On the other hand, to realize real-time visual servoing control, a particular object recognition and pose estimation algorithm based on polygonal approximation is investigated to ensure a low computational cost for image processing. To avoid undesired forces involved in contact operation, 3D visual servoing incorporating a compliant control based on impedance control is developed. Finally, in a representative laboratory environment, a typical satellite servicing experiment is carried out based on this combined system. Experimental results demonstrate the feasibility and the effectiveness of the proposed method.

  17. A General Approach to Enhance Short Wave Satellite Imagery by Removing Background Atmospheric Effects

    Directory of Open Access Journals (Sweden)

    Ronald Scheirer

    2018-04-01

    Full Text Available Atmospheric interaction distorts the surface signal received by a space-borne instrument. Images derived from visible channels appear often too bright and with reduced contrast. This hampers the use of RGB imagery otherwise useful in ocean color applications and in forecasting or operational disaster monitoring, for example forest fires. In order to correct for the dominant source of atmospheric noise, a simple, fast and flexible algorithm has been developed. The algorithm is implemented in Python and freely available in PySpectral which is part of the PyTroll family of open source packages, allowing easy access to powerful real-time image-processing tools. Pre-calculated look-up tables of top of atmosphere reflectance are derived by off-line calculations with RTM DISORT as part of the LibRadtran package. The approach is independent of platform and sensor bands, and allows it to be applied to any band in the visible spectral range. Due to the use of standard atmospheric profiles and standard aerosol loads, it is possible just to reduce the background disturbance. Thus signals from excess aerosols become more discernible. Examples of uncorrected and corrected satellite images demonstrate that this flexible real-time algorithm is a useful tool for atmospheric correction.

  18. Comparative study of FDMA, TDMA and hybrid 30/20 GHz satellite communications systems for small users

    Science.gov (United States)

    Berk, G.; Jean, P. N.; Rotholz, E.

    1982-01-01

    This study compares several satellite uplink and downlink accessing schemes for a Customer Premises Service. Four conceptual system designs are presented: Satellite-Routed FDMA, Frequency-Routed TDMA, Satellite-Switched TDMA, and Processor-Routed TDMA, operating in the 30/20 GHz band. The designs are compared on the basis of estimated satellite weight, power consumption, and cost. The system capacities are analyzed for a fixed multibeam coverage of CONUS. Analysis shows that the system capacity is limited by the available satellite resources and by the terminal size and cost.

  19. Mutual perceptions between nuclear plant employees and general public on nuclear policy communication applying the Co-orientation analysis model

    International Nuclear Information System (INIS)

    Kim, Bong Chul; Kim, Ji Hyun; Chung, Woon Kwan

    2015-01-01

    This study examines mutual perceptions between general public and nuclear plant employees on understanding nuclear policy communication applying the co-orientation model. The total of 414 responses were analyzed including 211 of the general public and 203 of plant employees. Results indicate that agreement between general public and plant employees is relatively high, in that general public tends to have negative evaluation to nuclear policy communication, but plant employees tends to have positive one. In terms of congruence, general public perceive that plant employees might have more positive evaluation than themselves, and nuclear plant employees perceive that general public might have more negative evaluation than themselves. Finally, in terms of accuracy, general public accurately estimate how nuclear plant employees perceive on policy communication, whereas nuclear plant employees unaccurately estimate how general public perceive on policy communication

  20. Mutual perceptions between nuclear plant employees and general public on nuclear policy communication applying the Co-orientation analysis model

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Bong Chul; Kim, Ji Hyun; Chung, Woon Kwan [Chosun University, Gwangju (Korea, Republic of)

    2015-02-15

    This study examines mutual perceptions between general public and nuclear plant employees on understanding nuclear policy communication applying the co-orientation model. The total of 414 responses were analyzed including 211 of the general public and 203 of plant employees. Results indicate that agreement between general public and plant employees is relatively high, in that general public tends to have negative evaluation to nuclear policy communication, but plant employees tends to have positive one. In terms of congruence, general public perceive that plant employees might have more positive evaluation than themselves, and nuclear plant employees perceive that general public might have more negative evaluation than themselves. Finally, in terms of accuracy, general public accurately estimate how nuclear plant employees perceive on policy communication, whereas nuclear plant employees unaccurately estimate how general public perceive on policy communication.

  1. Use of hyperlinks in electronic test result communication: a survey study in general practice

    Directory of Open Access Journals (Sweden)

    Mukai Thomas

    2012-10-01

    Full Text Available Abstract Background Information is essential in healthcare. Recording, handling and sharing healthcare information is important in order to ensure high quality of delivered healthcare. Information and communication technology (ICT may be a valuable tool for handling these challenges. One way of enhancing the exchange of information could be to establish a link between patient-specific and general information sent to the general practitioner (GP. The aim of the present paper is to study GPs' use of a hyperlink inserted into electronic test result communication. Methods We inserted a hyperlink into the electronic test result communication sent to the patients’ GPs who participated in a regional, systematic breast cancer screening program. The hyperlink target was a web-site with information on the breast cancer screening program and breast cancer in general. Different strategies were used to increase the GPs’ use of this hyperlink. The outcome measure was the GPs’ self-reported use of the link. Data were collected by means of a one-page paper-based questionnaire. Results The response rate was 73% (n=242. In total, 108 (45% of the GPs reported to have used the link. In all, 22% (n=53 of the GPs used the web-address from a paper letter and 37% (n=89 used the hyperlink in the electronic test result communication (Δ = 15%[95%confidence  int erval(CI = 8 − 22%P  Conclusions The results suggest that hyperlinks in electronic test result communication could be a feasible strategy for combining and sharing different types of healthcare information.

  2. Generalized projective synchronization via the state observer and its application in secure communication

    International Nuclear Information System (INIS)

    Wu Di; Li Juan-Juan

    2010-01-01

    Based on the improved state observer and the pole placement technique, by adding a constant which extends the scope of use of the original system, a new design method of generalized projective synchronization is proposed. With this method, by changing the projective synchronization scale factor, one can achieve not only complete synchronization, but also anti-synchronization, as well as arbitrary percentage of projective synchronization, so that the system may attain arbitrary synchronization in a relatively short period of time, which makes this study more meaningful. By numerical simulation, and choosing appropriate scale factor, the results of repeated experiments verify that this method is highly effective and satisfactory. Finally, based on this method and the relevant feedback concept, a novel secure communication project is designed. Numerical simulation verifies that this secure communication project is very valid, and moreover, the experimental result has been greatly improved in decryption time. (general)

  3. Vocational trainees’ views and experiences regarding the learning and teaching of communication skills in general practice

    OpenAIRE

    Van Nuland, Marc; Thijs, Gaby; Van Royen, Paul; Van Den Noortgate, Wim; Goedhuys, Jo

    2010-01-01

    Objective: To explore the views and experiences of general practice (GP) vocational trainees regarding communication skills (CS) and the teaching and learning of these skills. METHODS: A purposive sample of second and third (final) year GP trainees took part in six focus group (FG) discussions. Transcripts were coded and analysed in accordance with a grounded theory approach by two investigators using Alas-ti software. Finally results were triangulated by means of semi-structured telephone in...

  4. A Reinforcement Model of the Relationships of Supervisors' General Communication Styles and Conflict Management Styles to Task Attraction.

    Science.gov (United States)

    Wheeless, Lawrence R.; Reichel, Lisa S.

    1990-01-01

    Investigates the relationship between general styles of communicating and more situation-specific conflict management styles. Finds substantial relationships between general communication styles and conflict management styles, as well as very substantial relationships between the style constructs and task attraction of supervisors. (SR)

  5. Risk factor for preterm labor in Haji Adam Malik General Hospital, Pirngadi General hospital and satellite hospitals in Medan from January 2014 to December 2016

    Science.gov (United States)

    Sukatendel, K.; Hasibuan, C. L.; Pasaribu, H. P.; Sihite, H.; Ardyansah, E.; Situmorang, M. F.

    2018-03-01

    In 2010, Indonesia was ranked fifth in the world for the number of premature birth. Prematurity is a multifactorial problem. Preterm Labor (PTL) can occur spontaneously without a clear cause. Preventing PTL, its associated risk factors must be recognized first. To analyze risk factors associated with the incidence of PTL. It is a cross sectional study using secondary data obtained from medical records in Haji Adam Malik general hospital, Pirngadi general hospital and satellite hospitals in Medan from January 2014 to December 2016. Data were analyzed using chi-square method and logistic regression test. 148 cases for each group of preterm labor and obtained term laborin this study. Using the logistic regression test, three factors with astrong association to the incidence of identifiedpreterm labor. Antenatal Care frequency (OR 2,326; CI 95%), leucorrhea (OR 6,291; 95%), and premature rupture of membrane (OR 9,755; CI 95%). In conclusion, antenatal care frequency, leucorrhea, and history of premature rupture of themembrane may increase the incidence of Preterm Labor (PTL).

  6. A possible experiment with two counter-orbiting drag-free satellites to obtain a new test of Einstein's general theory of relativity and improved measurements in geodesy

    Science.gov (United States)

    Van Patten, R. A.; Everitt, C. W. F.

    1976-01-01

    In 1918, Lense and Thirring calculated that a moon in orbit around a massive rotating planet would experience a nodal dragging effect due to general relativity. We describe an experiment to measure this effect by means of two counter-orbiting drag-free satellites in polar orbit about the earth. For a 2-1/2 year experiment, the measurement should approach an accuracy of 1%. An independent measurement of the geodetic precession of the orbit plane due to the motion about the sun may also be possible to about 10% accuracy. In addition to precision tracking data from existing ground stations, satellite-to-satellite Doppler data are taken at points of passing near the poles to yield an accurate measurement of the separation distance between the two satellites. New geophysical information on both earth harmonics and tidal effects is inherent in this polar ranging data.

  7. A generalized architecture of quantum secure direct communication for N disjointed users with authentication

    Science.gov (United States)

    Farouk, Ahmed; Zakaria, Magdy; Megahed, Adel; Omara, Fatma A.

    2015-11-01

    In this paper, we generalize a secured direct communication process between N users with partial and full cooperation of quantum server. So, N - 1 disjointed users u1, u2, …, uN-1 can transmit a secret message of classical bits to a remote user uN by utilizing the property of dense coding and Pauli unitary transformations. The authentication process between the quantum server and the users are validated by EPR entangled pair and CNOT gate. Afterwards, the remained EPR will generate shared GHZ states which are used for directly transmitting the secret message. The partial cooperation process indicates that N - 1 users can transmit a secret message directly to a remote user uN through a quantum channel. Furthermore, N - 1 users and a remote user uN can communicate without an established quantum channel among them by a full cooperation process. The security analysis of authentication and communication processes against many types of attacks proved that the attacker cannot gain any information during intercepting either authentication or communication processes. Hence, the security of transmitted message among N users is ensured as the attacker introduces an error probability irrespective of the sequence of measurement.

  8. Danish Citizens and General Practitioners' Use of ICT for their Mutual Communication.

    Science.gov (United States)

    Bertelsen, Pernille; Stub Petersen, Lone

    2015-01-01

    This paper reports on selected findings from a Danish national survey of citizens' perception and use of information and communication technology (ICT) for their health care [1]. Focus is on citizens' use of ICT and on communication with their General Practitioner (GP). It also focuses on citizens' experience of their GPs' ICT use and no use during medical consultations. The responsibility for medical service in Denmark is to a large extent handed over to the primary sector where the GP is the gatekeeper. Our data display that 65% of the adult citizens or their relatives have been using ICT to communicate with their GP. Twenty-two percent have experienced their GP use a computer screen to actively show them something while they have a consultation. Further, our data supports the assumption that the higher the education people have, the more likely they are to use ICT for their health care. The understanding of the use of ICT in communication with the GP is central to monitoring and developing an ICT that supports all citizens and considers new ways in which to enhance quality of care.

  9. A Non-symmetric Digital Image Secure Communication Scheme Based on Generalized Chaos Synchronization System

    International Nuclear Information System (INIS)

    Zhang Xiaohong; Min Lequan

    2005-01-01

    Based on a generalized chaos synchronization system and a discrete Sinai map, a non-symmetric true color (RGB) digital image secure communication scheme is proposed. The scheme first changes an ordinary RGB digital image with 8 bits into unrecognizable disorder codes and then transforms the disorder codes into an RGB digital image with 16 bits for transmitting. A receiver uses a non-symmetric key to verify the authentication of the received data origin, and decrypts the ciphertext. The scheme can encrypt and decrypt most formatted digital RGB images recognized by computers, and recover the plaintext almost without any errors. The scheme is suitable to be applied in network image communications. The analysis of the key space, sensitivity of key parameters, and correlation of encrypted images imply that this scheme has sound security.

  10. Identifying context factors explaining physician's low performance in communication assessment: an explorative study in general practice.

    NARCIS (Netherlands)

    Essers, G.; Dulmen, S. van; Weel, C. van; Vleuten, C. van der; Kramer, A.

    2011-01-01

    BACKGROUND: Communication is a key competence for health care professionals. Analysis of registrar and GP communication performance in daily practice, however, suggests a suboptimal application of communication skills. The influence of context factors could reveal why communication performance

  11. Identifying context factors explaining physician's low performance in communication assessment: an explorative study in general practice.

    NARCIS (Netherlands)

    Essers, G.T.J.M.; Dulmen, A.M. van; Weel, C. van; Vleuten, C.P.M. van der; Kramer, A.W.

    2011-01-01

    ABSTRACT: BACKGROUND: Communication is a key competence for health care professionals. Analysis of registrar and GP communication performance in daily practice, however, suggests a suboptimal application of communication skills. The influence of context factors could reveal why communication

  12. [General principles of effective communication between physician and patient with selected mental disorders].

    Science.gov (United States)

    Błaszczyk, Justyna; Bobińska, Kinga; Filip, Maria; Gałecki, Piotr

    2015-04-01

    Faced with the growing frequency of mental disorders occurrence and considering the necessity of improving the patient care, it is particularly important that physicians of different specialties knew the general principles of effective communication with patients who are mentally ill. Equally important is to spread the knowledge of the symptomatology of various mental illnesses. Studies published by the Institute of Psychiatry and Neurology involving persons between 18 and 64 years old, show that 8 millions Poles suffers or suffered from mental disorders. This represents almost 25% of Polish society. The above data confirm, that basic knowledge of criteria for diagnosing mental disorders and their treatment by primary care physicians, determines the success of the entire health care system. It must be taken into consideration that frequently patients seeing general practitioner (GP) are suffering from more than one mental illness or it is accompanied by somatic disease. Adequate communication determines effective treatment. Simple yet exact message, ability to adapt it to patient and problems reported by him, is a valuable means in daily medical practice. It reduces the risk of iatrogenic disorder, encourages the efficiency of the entire therapeutic process. Good cooperation with the patient is also determined by patience, empathy, understanding, and competence. The aim of this study is to present the principles of effective communication between doctor and patient suffering from selected mental disorders. The article defines the concept of communication. It shows symptomatology of primary psychiatric disorders. Moreover, the most common difficulties in relationship between the doctor and the patient had been pointed. © 2015 MEDPRESS.

  13. Satellite communication on pipeline supervision using TCP-IP Protocol; Comunicacao via satelite na supervisao de dutos usando o protocolo TCP-IP

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Agliberto Pessoa da [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil); Brunette, Sergio Henrique de Moraes

    2003-07-01

    Bit transparent type or X-25 protocols have been used in VSAT satellite communication by PETROBRAS pipeline Supervisory Control and Data Acquisition System (SCADA) as access protocol. Both solutions have inconveniences. By the first one, difficulties exist for analysis and diagnosis of connection flaws, and therefore, for a ready identification by the system management stations of abnormality location. On the other hand, the usage of the X-25 brings an additional over-head in the communication since this is not an available option in most of the equipment that compose the SCADA. The access to VSAT through Ethernet, in the opposite, makes available all networks management tools of the TCP/IP platform and it allows a direct connection to the field devices, since the main models of the several makers of Programmable Controllers and Remote Terminal Units have Ethernet port. An additional earnings is the possibility of standardization that this solution allows. This paper describes a series of communication tests between two Programmable Controllers communicating through the satellite, using a protocol over Ethernet/TCP/IP. (author)

  14. Advances in satellite communications

    CERN Document Server

    Minoli, Daniel

    2015-01-01

    Discussing advances in modulation techniques and HTS spotbeam technologiesSurveying emerging high speed aeronautical mobility services and maritime and other terrestrial mobility servicesAssessing M2M (machine-to-machine) applications, emerging Ultra HD video technologies and new space technology

  15. Introduction to Satellite Communications.

    Science.gov (United States)

    1974-04-15

    center of the earth) the attr o, f B1 - ,ri 1he center of the earth and the repulsion of A’ from the cerier uf ci- ear- .suihs in a torque being applied...April 1974 CCP 105-5 Table 8- 1. L f and v/f frequency and time standards Station WWVB WWVL NBA GBR MSF Location Boulder, Sunset, Summit, R ugby, Rugby

  16. In situ occupational and general public exposure to VHF/UHF transmission for air traffic communication.

    Science.gov (United States)

    Joseph, Wout; Goeminne, Francis; Verloock, Leen; Vermeeren, Günter; Martens, Luc

    2012-09-01

    Occupational and general public exposure due to very high frequency (VHF)/ultra high frequency (UHF) transmission centres for verbal communication for air traffic control is investigated in situ for the first time. These systems are used for communication with aircraft, resulting in different human exposure from that of classical broadcasting. Measurement methods are proposed for the exposure assessment, and a measurement campaign is executed in three transmission centres. By investigating the temporal behaviour of the VHF signals for 6 d, a realistic worst-case duty cycle of 29 % is determined. Periods of high exposures corresponding with high aircraft traffic are from 7 a.m. to 1 p.m. and in the evening. All measured electric-field values satisfy the International Commission on Non-ionizing Radiation Protection guidelines. Fields vary from 0.2 to 21.1 V m(-1) for occupational exposure and from 0.007 to 8.0 V m(-1) for general public exposure. The average fields equal 5.2 V m(-1) for workers, and 0.7 V m(-1) for general public.

  17. In situ occupational and general public exposure to VHF/UHF transmission for air traffic communication

    International Nuclear Information System (INIS)

    Joseph, W.; Goeminne, F.; Verloock, L.; Vermeeren, G.; Martens, L.

    2012-01-01

    Occupational and general public exposure due to very high frequency (VHF)/ultra high frequency (UHF) transmission centres for verbal communication for air traffic control is investigated in situ for the first time. These systems are used for communication with aircraft, resulting in different human exposure from that of classical broadcasting. Measurement methods are proposed for the exposure assessment, and a measurement campaign is executed in three transmission centres. By investigating the temporal behaviour of the VHF signals for 6 d, a realistic worst-case duty cycle of 29 % is determined. Periods of high exposures corresponding with high aircraft traffic are from 7 a.m. to 1 p.m. and in the evening. All measured electric field values satisfy the International Commission on Non-ionizing Radiation Protection guidelines. Fields vary from 0.2 to 21.1 V m -1 for occupational exposure and from 0.007 to 8.0 V m -1 for general public exposure. The average fields equal 5.2 V m -1 for workers, and 0.7 V m -1 for general public. (authors)

  18. A design of 30/20 GHz flight communications experiment for NASA. [satellite and earth segments for high data rate commercial service

    Science.gov (United States)

    Kawamoto, Y.

    1982-01-01

    The objective of the 30/20 GHz Flight Experiment System is to develop the required technology and to experiment with the communication technique for an operational communication satellite system. The system uses polarization, spatial, and frequency isolations to maximize the spectrum utilization. The key spacecraft technologies required for the concept are the scan beam antenna, the baseband processor, the IF switch matrix, TWTA, SSPA, and LNA. The spacecraft communication payload information will be telemetered and monitored closely so that these technologies and performances can be verified. Two types of services, a trunk service and a customer premise service, are demonstrated in the system. Many experiments associated with these services, such as synchronization, demand assignment, link control, and network control will be performed to provide important information on the operational aspect of the system.

  19. A statistical rain attenuation prediction model with application to the advanced communication technology satellite project. 3: A stochastic rain fade control algorithm for satellite link power via non linear Markow filtering theory

    Science.gov (United States)

    Manning, Robert M.

    1991-01-01

    The dynamic and composite nature of propagation impairments that are incurred on Earth-space communications links at frequencies in and above 30/20 GHz Ka band, i.e., rain attenuation, cloud and/or clear air scintillation, etc., combined with the need to counter such degradations after the small link margins have been exceeded, necessitate the use of dynamic statistical identification and prediction processing of the fading signal in order to optimally estimate and predict the levels of each of the deleterious attenuation components. Such requirements are being met in NASA's Advanced Communications Technology Satellite (ACTS) Project by the implementation of optimal processing schemes derived through the use of the Rain Attenuation Prediction Model and nonlinear Markov filtering theory.

  20. Communication and mental health in general practice: physicians' self-perceived learning needs and self-efficacy

    OpenAIRE

    Stensrud, Tonje L; Mjaaland, Trond A; Finset, Arnstein

    2012-01-01

    Background General practitioners (GPs) often see patients presenting with mental health problems, but their training regarding mental health treatment varies. GPs' communication skills are of particular importance in these consultations, and communication skills training of GPs has been found to improve patients' mental health. To tailor a communication skills training by basing it on GPs' learning needs and self-efficacy, thereby maximising learning, we conducted a questionnaire study.

  1. A secure communication scheme based generalized function projective synchronization of a new 5D hyperchaotic system

    International Nuclear Information System (INIS)

    Wu, Xiangjun; Fu, Zhengye; Kurths, Jürgen

    2015-01-01

    In this paper, a new five-dimensional hyperchaotic system is proposed based on the Lü hyperchaotic system. Some of its basic dynamical properties, such as equilibria, Lyapunov exponents, bifurcations and various attractors are investigated. Furthermore, a new secure communication scheme based on generalized function projective synchronization (GFPS) of this hyperchaotic system with an uncertain parameter is presented. The communication scheme is composed of the modulation, the chaotic receiver, the chaotic transmitter and the demodulation. The modulation mechanism is to modulate the message signal into the system parameter. Then the chaotic signals are sent to the receiver via a public channel. In the receiver end, by designing the controllers and the parameter update rule, GFPS between the transmitter and receiver systems is achieved and the unknown parameter is estimated simultaneously. The message signal can be finally recovered by the identified parameter and the corresponding demodulation method. There is no any limitation on the message size. Numerical simulations are performed to show the validity and feasibility of the presented secure communication scheme. (paper)

  2. Communicating and dealing with uncertainty in general practice: the association with neuroticism.

    Directory of Open Access Journals (Sweden)

    Antonius Schneider

    Full Text Available Diagnostic reasoning in primary care setting where presented problems and patients are mostly unselected appears as a complex process. The aim was to develop a questionnaire to describe how general practitioners (GPs deal with uncertainty to gain more insight into the decisional process. The association of personality traits with medical decision making was investigated additionally.Raw items were identified by literature research and focus group. Items were improved by interviewing ten GPs with thinking-aloud-method. A personal case vignette related to a complex and uncertainty situation was introduced. The final questionnaire was administered to 228 GPs in Germany. Factorial validity was calculated with explorative and confirmatory factor analysis. The results of the Communicating and Dealing with Uncertainty (CoDU-questionnaire were compared with the scales of the 'Physician Reaction to Uncertainty' (PRU questionnaire and with the personality traits which were determined with the Big Five Inventory (BFI-K.The items could be assigned to four scales with varying internal consistency, namely 'communicating uncertainty' (Cronbach alpha 0.79, 'diagnostic action' (0.60, 'intuition' (0.39 and 'extended social anamnesis' (0.69. Neuroticism was positively associated with all PRU scales 'anxiety due to uncertainty' (Pearson correlation 0.487, 'concerns about bad outcomes' (0.488, 'reluctance to disclose uncertainty to patients' (0.287, 'reluctance to disclose mistakes to physicians' (0.212 and negatively associated with the CoDU scale 'communicating uncertainty' (-0.242 (p<0.01 for all. 'Extraversion' (0.146; p<0.05, 'agreeableness' (0.145, p<0.05, 'conscientiousness' (0.168, p<0.05 and 'openness to experience' (0.186, p<0.01 were significantly positively associated with 'communicating uncertainty'. 'Extraversion' (0.162, 'consciousness' (0.158 and 'openness to experience' (0.155 were associated with 'extended social anamnesis' (p<0.05.The

  3. Woodland expansion in South African grassy biomes based on satellite observations (1990-2013): general patterns and potential drivers.

    Science.gov (United States)

    Skowno, Andrew L; Thompson, Mark W; Hiestermann, Jens; Ripley, Brad; West, Adam G; Bond, William J

    2017-06-01

    Increases in woody plant cover in savanna grassland environments have been reported on globally for over 50 years and are generally perceived as a threat to rangeland productivity and biodiversity. Despite this, few attempts have been made to estimate the extent of woodland increase at a national scale, principally due to technical constraints such as availability of appropriate remote sensing products. In this study, we aimed to measure the extent to which woodlands have replaced grasslands in South Africa's grassy biomes. We use multiseason Landsat data in conjunction with satellite L-band radar backscatter data to estimate the extent of woodlands and grasslands in 1990 and 2013. The method employed allows for a unique, nationwide measurement of transitions between grassland and woodland classes in recent decades. We estimate that during the 23-year study period, woodlands have replaced grasslands over ~57 000 km 2 and conversely that grasslands have replaced woodlands over ~30 000 km 2 , a net increase in the extent of woodland of ~27 000 km 2 and an annual increase of 0.22%. The changes varied markedly across the country; areas receiving over 500 mm mean annual precipitation showed higher rates of woodland expansion than regions receiving 0.19% yr -1 ). The woodland change map presented here provides a unique opportunity to test the numerous models of woody plant encroachment at a national/regional scale. © 2016 John Wiley & Sons Ltd.

  4. How can a research library support the communication of science to the general public?

    Science.gov (United States)

    Brunetti, F.; Gasperini, A.

    2008-06-01

    How can an observatory library support the communication of science to the general public? We will describe how a highly specialised astronomical library can also play a key role in disseminating astronomical knowledge, making scientific results available across a wide range of levels, from professional to public to educational. This outreach activity requires several steps, ranging from the preliminary identification and scrutiny of sources to the production of new information material (e.g. maps, brochures, and DVDs). In particular, we will describe some recent experiences in the dissemination of astronomical information to the general public, especially teachers and children, analysing some results of this activity, such as a bibliography of Italian Astronomical Books for Children, a review of scientific books and other multimedia products.

  5. Starting from Scratch and Getting Somewhere: Assessment of Oral Communication Proficiency in General Education across Lower and Upper Division Courses

    Science.gov (United States)

    Avanzino, Susan

    2010-01-01

    Communication departments are expected to conduct program level assessment, as well as assessment of communication in general education. Although the expectation for data-driven student learning assessment is growing, relatively few examples exist for doing so effectively. This article serves as a model to help faculty conduct effective assessment…

  6. Low-cost approach for a software-defined radio based ground station receiver for CCSDS standard compliant S-band satellite communications

    Science.gov (United States)

    Boettcher, M. A.; Butt, B. M.; Klinkner, S.

    2016-10-01

    A major concern of a university satellite mission is to download the payload and the telemetry data from a satellite. While the ground station antennas are in general easy and with limited afford to procure, the receiving unit is most certainly not. The flexible and low-cost software-defined radio (SDR) transceiver "BladeRF" is used to receive the QPSK modulated and CCSDS compliant coded data of a satellite in the HAM radio S-band. The control software is based on the Open Source program GNU Radio, which also is used to perform CCSDS post processing of the binary bit stream. The test results show a good performance of the receiving system.

  7. Dissatisfaction of Compact Picard Condition (CPC) with GRACE satellite data and its treatment by Generalized Tikhonov in Sobolev subspace

    Science.gov (United States)

    AllahTavakoli, Y.; Bagheri, H.; Safari, A.; Sharifi, M.

    2012-04-01

    This paper is mainly aiming to prove that the stripy noises in the map of earth's surface mass-density changes derived from GRACE Satellites gravimetry, is due to a dissatisfaction of Compact Picard Condition (CPC) with the GRACE data in the inversion of the Newton Integral Equation over the thin layer of earth; and hence the paper proposes the regularization strategies as efficient tools to treat the Ill-posedness and consequently to de-strip the data. First of all, we preferred to slightly modify the mathematical model of earth's surface mass-density changes developed creatively first by J. Wahr and et.al (1998), according to the all their previous assumptions plus taking into consideration the effect of the earth topography. By the modification we expect that some uncertainties in the prior model have been reduced to some extent. Then we analyzed the CPC on the model and we demonstrated how to perform Generalized Tikhonov regularization in Sobolev subspace for overcoming the instability of the problem. Then we applied the strategy in some simulations and case studies to validate our ideas. The simulations confirm that the stripy noises in the GRACE-derived map of the mass-density changes are due to the CPC dissatisfaction and furthermore the case studies show that Generalized Tikhonov regularization in Sobolev subspace is an influential filtering tool to de-strip the noisy data. Also, the case studies interestingly show that the effect of the topography is comparable to the effect of the load Love numbers on the Wahr's model; hence it may be taken into consideration when the load Love numbers have been taken into account.

  8. A general framework of TOPSIS method for integration of airborne geophysics, satellite imagery, geochemical and geological data

    Science.gov (United States)

    Abedi, Maysam; Norouzi, Gholam-Hossain

    2016-04-01

    This work presents the promising application of three variants of TOPSIS method (namely the conventional, adjusted and modified versions) as a straightforward knowledge-driven technique in multi criteria decision making processes for data fusion of a broad exploratory geo-dataset in mineral potential/prospectivity mapping. The method is implemented to airborne geophysical data (e.g. potassium radiometry, aeromagnetic and frequency domain electromagnetic data), surface geological layers (fault and host rock zones), extracted alteration layers from remote sensing satellite imagery data, and five evidential attributes from stream sediment geochemical data. The central Iranian volcanic-sedimentary belt in Kerman province at the SE of Iran that is embedded in the Urumieh-Dokhtar Magmatic Assemblage arc (UDMA) is chosen to integrate broad evidential layers in the region of prospect. The studied area has high potential of ore mineral occurrences especially porphyry copper/molybdenum and the generated mineral potential maps aim to outline new prospect zones for further investigation in future. Two evidential layers of the downward continued aeromagnetic data and its analytic signal filter are prepared to be incorporated in fusion process as geophysical plausible footprints of the porphyry type mineralization. The low values of the apparent resistivity layer calculated from the airborne frequency domain electromagnetic data are also used as an electrical criterion in this investigation. Four remote sensing evidential layers of argillic, phyllic, propylitic and hydroxyl alterations were extracted from ASTER images in order to map the altered areas associated with porphyry type deposits, whilst the ETM+ satellite imagery data were used as well to map iron oxide layer. Since potassium alteration is generally the mainstay of porphyry ore mineralization, the airborne potassium radiometry data was used. The geochemical layers of Cu/B/Pb/Zn elements and the first component of PCA

  9. A series on optimizing satellite systems. I - Restoring interruptions of communications sattelite service: Logistical and cost comparisons of mature and newly operational systems

    Science.gov (United States)

    Snow, Marcellus S.

    1989-09-01

    A mathematical model is presented of costs and operational factors involved in provision for service interruptions of both a mature and typically large incumbent satellite system and of a smaller, more recently operational system. The equation expresses the required launch frequency for the new system as a function of the launch spacing of the mature system; the time disparity between the inauguration of the two systems; and the rate of capacity depreciation. In addition, a technique is presented to compare the relative extent to which the discounted costs of the new system exceed those of the mature system in furnishing the same effective capacity in orbit, and thus the same service liability, at a given point in time. It is determined that a mature incumbent communications satellite system, having more capacity in orbit, will on balance have a lower probability of service interruption than a newer, smaller system.

  10. COMMUNICATIONS

    CERN Multimedia

    A. Petrilli

    2013-01-01

    The organisation of the Open Days at the end of September was the single biggest effort of the CMS Communications Group this year. We would like to thank all volunteers for their hard work to show our Point 5 facilities and explain science and technology to the general public. During two days more than 5,000 people visited the CMS detector underground and profited from the surface activities, which included an exhibition on CMS, a workshop on superconductivity, and an activity for our younger visitors involving wooden Kapla blocks. The Communications Group took advantage of the preparations to produce new CMS posters that can be reused at other venues. Event display images have been produced not just for this occasion but also for other exhibits, education purposes, publications etc. During the Open Days, Gilles Jobin, 2012 winner of CERN Collide@CERN prize, performed his Quantum show in Point 5, with the light installation of German artist Julius von Bismarck. Image 3: CERN Open Days at CMS wel...

  11. Proceedings of the Twenty-First NASA Propagation Experiments Meeting (NAPEX XXI) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop

    Science.gov (United States)

    Golshan, Nasser (Editor)

    1997-01-01

    The NASA Propagation Experimenters (NAPEX) meeting is convened each year to discuss studies supported by the NASA Propagation Program. Representatives from the satellite communications industry, academia and government who have an interest in space-ground radio wave propagation are invited to NAPEX meetings for discussions and exchange of information. The reports delivered at this meeting by program managers and investigators present recent activities and future plans. This forum provides an opportunity for peer discussion of work in progress, timely dissemination of propagation results, and close interaction with the satellite communications industry. NAPEX XXI took place in El Segundo, California on June 11-12, 1997 and consisted of three sessions. Session 1, entitled "ACTS Propagation Study Results & Outcome " covered the results of 20 station-years of Ka-band radio-wave propagation experiments. Session 11, 'Ka-band Propagation Studies and Models,' provided the latest developments in modeling, and analysis of experimental results about radio wave propagation phenomena for design of Ka-band satellite communications systems. Session 111, 'Propagation Research Topics,' covered a diverse range of propagation topics of interest to the space community, including overviews of handbooks and databases on radio wave propagation. The ACTS Propagation Studies miniworkshop was held on June 13, 1997 and consisted of a technical session in the morning and a plenary session in the afternoon. The morning session covered updates on the status of the ACTS Project & Propagation Program, engineering support for ACTS Propagation Terminals, and the Data Center. The plenary session made specific recommendations for the future direction of the program.

  12. LEOcom: communication system for low earth orbit satellites for voice, data and facsimile; LEOcom - sistema de comunicacao por satelites de orbita terrestre baixa para voz, dados e facsimile

    Energy Technology Data Exchange (ETDEWEB)

    Giacaglia, G.E.O.; Lamas, W.Q. [Universidade de Taubate (UNITAU), SP (Brazil). Programa de Pos-graduacao em Engenharia Mecanica], E-mail: giorgio@unitau.br; Ceballos, D.C. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil); Pereira, J.J. [Comando-Geral de Tecnologia Aeroespacial (CTA), Sao Jose dos Campos, SP (Brazil)

    2009-07-01

    This paper provides a basic description of a Communication System for Low Earth Orbit Satellites that can provide voice, data and facsimile to hundreds of countries located in equatorial land between + and - 20 deg latitude, reaching higher latitudes, depending on the location of the onshore terminal. As a point high, it emphasizes its opportunity to support the control of networks transmission of electricity, in any area, and plants generation, located in remote areas, and support any type of operation in these regions. It is the aim of this work to reactivate a good project for Brazil and the tropical world.

  13. Simultaneous Laser Ranging and Communication from an Earth-Based Satellite Laser Ranging Station to the Lunar Reconnaissance Orbiter in Lunar Orbit

    Science.gov (United States)

    Sun, Xiaoli; Skillman, David R.; Hoffman, Evan D.; Mao, Dandan; McGarry, Jan F.; Neumann, Gregory A.; McIntire, Leva; Zellar, Ronald S.; Davidson, Frederic M.; Fong, Wai H.; hide

    2013-01-01

    We report a free space laser communication experiment from the satellite laser ranging (SLR) station at NASA Goddard Space Flight Center (GSFC) to the Lunar Reconnaissance Orbiter (LRO) in lunar orbit through the on board one-way Laser Ranging (LR) receiver. Pseudo random data and sample image files were transmitted to LRO using a 4096-ary pulse position modulation (PPM) signal format. Reed-Solomon forward error correction codes were used to achieve error free data transmission at a moderate coding overhead rate. The signal fading due to the atmosphere effect was measured and the coding gain could be estimated.

  14. The American Satellite Company (ASC) satellite deployed from payload bay

    Science.gov (United States)

    1985-01-01

    The American Satellite Company (ASC) communications satellite is deployed from the payload bay of the Shuttle Discovery. A portion of the cloudy surface of the earth can be seen to the left of the frame.

  15. Detection of Coccolithophore Blooms in Ocean Color Satellite Imagery: a Generalized Approach for Use with Multiple Sensors

    Science.gov (United States)

    Moore, Timothy; Dowell, Mark; Franz, Bryan A.

    2012-01-01

    A generalized coccolithophore bloom classifier has been developed for use with ocean color imagery. The bloom classifier was developed using extracted satellite reflectance data from SeaWiFS images screened by the default bloom detection mask. In the current application, we extend the optical water type (OWT) classification scheme by adding a new coccolithophore bloom class formed from these extracted reflectances. Based on an in situ coccolithophore data set from the North Atlantic, the detection levels with the new scheme were between 1,500 and 1,800 coccolithophore cellsmL and 43,000 and 78,000 lithsmL. The detected bloom area using the OWT method was an average of 1.75 times greater than the default bloom detector based on a collection of SeaWiFS 1 km imagery. The versatility of the scheme is shown with SeaWiFS, MODIS Aqua, CZCS and MERIS imagery at the 1 km scale. The OWT scheme was applied to the daily global SeaWiFS imagery mission data set (years 19972010). Based on our results, average annual coccolithophore bloom area was more than two times greater in the southern hemisphere compared to the northern hemi- sphere with values of 2.00 106 km2 and 0.75 106 km2, respectively. The new algorithm detects larger bloom areas in the Southern Ocean compared to the default algorithm, and our revised global annual average of 2.75106 km2 is dominated by contributions from the Southern Ocean.

  16. Patients' willingness to pay for electronic communication with their general practitioner.

    Science.gov (United States)

    Bergmo, Trine Strand; Wangberg, Silje Camilla

    2007-06-01

    Despite the common use of electronic communication in other aspects of everyday life, its use between patients and health care providers has been slow to diffuse. Possible explanations are security issues and lack of payment mechanisms. This study investigated how patients value secure electronic access to their general practitioner (GP). One hundred and ninety-nine patients were asked an open-ended willingness-to-pay (WTP) question as part of a randomised controlled trial. We compared the WTP values between two groups of respondents; one group had had the opportunity to communicate electronically with their GP for a year and the other group had not. Fifty-two percent of the total sample was willing to pay for electronic GP contact. The group of patients with access revealed a significantly lower WTP than the group without such access. Possible explanations are that the system had fewer benefits than expected, a presence of hypothetical bias or simply a preference for face-to-face encounters.

  17. Satellite outreach in Asia and the Pacific.

    Science.gov (United States)

    1977-01-01

    Communication by satellite is rapidly changing information exchange in Asia, especially for rural areas. The integrated education planned for satellite networks includes family planning as part of general development. A series of conferences has already been held successfully via satellite for family planning associations who are members of the East and Southeast Asia and Oceania Region of the International Planned Parenthood Federation. These included a conference on nursing training. In India the Satellite Instructional Television Experiment (SITE) made history during its 1-year trial. By 1981 the entire nation is to be linked by satellite. The question is whether the television education will truly change rural life or whether it will become merely a diversion. In Indonesia, satellites were chosen as the fastest way to obtain interisland communication. The Domsat system links the entire 13,000-island archipelago and is already being used for emergency communications. The system, which was developed in 1 1/2 years by the Hughes Aircraft Corporation will be used for teaching basic health, hygiene, and family planning. It will be several years before Domsat is fully operational, but it bears watching.

  18. A General Algorithm for Robot Formations Using Local Sensing and Minimal Communication

    DEFF Research Database (Denmark)

    Fredslund, Jakob; Matarić, Maja J

    2002-01-01

    the friend in the sensor's field of view. We also present a general analytical measure for evaluating formations and apply it to the position data from both simulation and physical robot experiments. We used two lasers to track the physical robots to obtain ground truth validation data....... simulation exper- iments, and 40+ experiments with four physical robots, showing the viability of our approach. The key idea is that each robot keeps a single friend at a desired angle , using some appropriate sensor. By panning the sensor by degrees, the goal for all formations be- comes simply to center......We study the problem of achieving global behavior in a group of distributed robots using only local sensing and minimal communication, in the context of formations. The goal is to have mobile robots establish and maintain some predetermined geo- metric shape. We report results from extensive...

  19. Satellite transmission of oceanographic data

    Digital Repository Service at National Institute of Oceanography (India)

    Desa, E.S.; Desai, R.G.P.; DeSa, E.J.

    Oceanographic data collected on a research vessel has been transmitted to a shore laboratory using the INMARSAT maritime satellite The system configuration used, consisted of Satellite Communication Terminals interfaced to desk top computers...

  20. Boomerang Satellites

    Science.gov (United States)

    Hesselbrock, Andrew; Minton, David A.

    2017-10-01

    We recently reported that the orbital architecture of the Martian environment allows for material in orbit around the planet to ``cycle'' between orbiting the planet as a ring, or as coherent satellites. Here we generalize our previous analysis to examine several factors that determine whether satellites accreting at the edge of planetary rings will cycle. In order for the orbiting material to cycle, tidal evolution must decrease the semi-major axis of any accreting satellites. In some systems, the density of the ring/satellite material, the surface mass density of the ring, the tidal parameters of the system, and the rotation rate of the primary body contribute to a competition between resonant ring torques and tidal dissipation that prevent this from occurring, either permanently or temporarily. Analyzing these criteria, we examine various bodies in our solar system (such as Saturn, Uranus, and Eris) to identify systems where cycling may occur. We find that a ring-satellite cycle may give rise to the current Uranian ring-satellite system, and suggest that Miranda may have formed from an early, more massive Uranian ring.

  1. Annual view (1999) - aeronautic relation/space relation. Space relation - communication/broadcasting/engineering test satellite; Nenkan tenbo (1999) koku kankei uchu kankei. Tsushin, hoso, gijutsu shiken eisei kanren

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-03-05

    To cope with the increasing communication demand, the R and D of engineering test satellite V III are being conducted being aimed at developing a technology of the world's largest class geostationary satellite. As to the large developing rectenna, a model for development was manufactured and is now in test. In August and September 1999, the system combustion test of complete two-liquid chemical propulsion system was carried out at Ishikawajima-Harima Heavy Industries. The R and D of the data relay technology satellite are being conducted for the purpose of conducting orbital demonstrative tests to improve the data relay functional performance of satellite and to spread the data relay range. The engineering test satellite VII was developed to study the space rendezvous/docking technology and the basic technology of space use robot. It was launched in November 1997 and got a lot of valuable data. The operation of satellite has been continued for the acquisition of data such as secular changes of satellite equipment. About the communication broadcasting satellite, experiments and functional tests were finished, and the operation was stopped in August 1999. (NEDO)

  2. Satellite fixed communications service: A forecast of potential domestic demand through the year 2000. Volume 3: Appendices

    Science.gov (United States)

    Kratochvil, D.; Bowyer, J.; Bhushan, C.; Steinnagel, K.; Kaushal, D.; Al-Kinani, G.

    1983-09-01

    Voice applications, data applications, video applications, impacted baseline forecasts, market distribution model, net long haul forecasts, trunking earth station definition and costs, trunking space segment cost, trunking entrance/exit links, trunking network costs and crossover distances with terrestrial tariffs, net addressable forecasts, capacity requirements, improving spectrum utilization, satellite system market development, and the 30/20 net accessible market are considered.

  3. The Voice/Data Communications system in the Health, Education, Telecommunications Experiments. Satellite Technology Demonstration, Technical Report No. 0417.

    Science.gov (United States)

    Janky, James M.; And Others

    The diligent use of two-way voice links via satellites substantially improves the quality and the availability of health care and educational services in remote areas. This improvement was demonstrated in several experiments that were sponsored by the Department of Health, Education, and Welfare and the National Aeronautics and Space…

  4. Quadriphase DS-CDMA wireless communication systems employing the generalized detector

    Science.gov (United States)

    Tuzlukov, Vyacheslav

    2012-05-01

    Probability of bit-error Per performance of asynchronous direct-sequence code-division multiple-access (DS-CDMA) wireless communication systems employing the generalized detector (GD) constructed based on the generalized approach to signal processing in noise is analyzed. The effects of pulse shaping, quadriphase or direct sequence quadriphase shift keying (DS-QPSK) spreading, aperiodic spreading sequences are considered in DS-CDMA based on GD and compared with the coherent Neyman-Pearson receiver. An exact Per expression and several approximations: one using the characterristic function method, a simplified expression for the improved Gaussian approximation (IGA) and the simplified improved Gaussian approximation are derived. Under conditions typically satisfied in practice and even with a small number of interferers, the standard Gaussian approximation (SGA) for the multiple-access interference component of the GD statistic and Per performance is shown to be accurate. Moreover, the IGA is shown to reduce to the SGA for pulses with zero excess bandwidth. Second, the GD Per performance of quadriphase DS-CDMA is shown to be superior to that of bi-phase DS-CDMA. Numerical examples by Monte Carlo simulation are presented to illustrate the GD Per performance for square-root raised-cosine pulses and spreading factors of moderate to large values. Also, a superiority of GD employment in CDMA systems over the Neyman-Pearson receiver is demonstrated

  5. Communication problems between dementia carers and general practitioners: effect on access to community support services.

    Science.gov (United States)

    Bruce, David G; Paley, Glenys A; Underwood, Peter J; Roberts, David; Steed, Duncan

    2002-08-19

    To investigate the circumstances that led general practitioners to refer dementia sufferers and their carers to community support services. Qualitative study using semi-structured interviews, carried out between 1 September 1999 and 30 April 2000. 21 live-in carers of patients with dementia referred for the first time to a Western Australian metropolitan Aged Care Assessment Team, and 19 of their referring general practitioners. Most referrals occurred after the carers had been experiencing carer stress, and were precipitated by crisis situations. Carers failed to discuss their difficulties with the referring GP for a variety of reasons, including the belief that they should cope because it was their duty. The doctors found it difficult to know how the carers were coping or when to intervene, and some carers tended to resist their attempts to help. Time constraints were a significant problem for both groups. Attitudinal barriers in both carers of patients with dementia and GPs, combined with time constraints, often lead to inadequate assessment of carer problems. While it is important that strategies to improve communication between carers and GPs are developed, it would be sensible for GPs to assume that dementia carers are at risk of carer stress and should be encouraged to use community care services.

  6. Knowledge Management Systems as an Interdisciplinary Communication and Personalized General-Purpose Technology

    Directory of Open Access Journals (Sweden)

    Ulrich Schmitt

    2015-10-01

    Full Text Available As drivers of human civilization, Knowledge Management (KM processes have co-evolved in line with General-Purpose-Technologies (GPT, such as writing, printing, and information and communication systems. As evidenced by the recent shift from information scarcity to abundance, GPTs are capable of drastically altering societies due to their game-changing impact on our spheres of work and personal development. This paper looks at the prospect of whether a novel Personal Knowledge Management (PKM concept supported by a prototype system has got what it takes to grow into a transformative General-Purpose-Technology. Following up on a series of papers, the KM scenario of a decentralizing revolution where individuals and self-organized groups yield more power and autonomy is examined according to a GPT's essential characteristics, including a wide scope for improvement and elaboration (in people's private, professional and societal life, applicability across a broad range of uses in a wide variety of products and processes (in multi-disciplinary educational and work contexts, and strong complementarities with existing or potential new technologies (like organizational KM Systems and a proposed World Heritage of Memes Repository. The result portrays the PKM concept as a strong candidate due to its personal, autonomous, bottom-up, collaborative, interdisciplinary, and creativity-supporting approach destined to advance the availability, quantity, and quality of the world extelligence and to allow for a wider sharing and faster diffusion of ideas across current disciplinary and opportunity divides.

  7. Resource effects of training general practitioners in risk communication skills and shared decision making competences.

    Science.gov (United States)

    Cohen, David; Longo, M F; Hood, Kerenza; Edwards, Adrian; Elwyn, Glyn

    2004-08-01

    Involving patients more in decisions about their own care requires doctors to be trained in effective ways of communicating information and in developing competences to negotiate levels of patient involvement which are most appropriate for each case. The aim of this study was to determine the cost of such training and identify which service resource variables are subsequently affected. An explanatory cluster randomized crossover trial was carried out which involved training general practitioners (GPs) in the use of risk communication (RC) tools, shared decision making (SDM) competences or both. Continuing care by GPs of patients with one of four chronic conditions (menopausal symptoms, menorrhagia, atrial fibrillation, prostatism) was reviewed before and after training. Cost of training was assessed by prospective monitoring of resources used. Data on prescribing, referrals and investigations were collected via questionnaires to participating practitioners. Data on follow-up GP consultations were extracted from medical records. Three two-level logistic models were performed to investigate the probability of training having an effect on prescribing, referrals and investigations ordered at the review consultation. Training cost pound 1218 per practitioner which increased the cost of a consultation by pound 2.89. Training in SDM or combined with RC significantly affected the probability of a prescription being issued to women with menopausal symptoms and menorrhagia (although RC on its own had no effect) but did not significantly affect prescribing for patients with prostatism or atrial fibrillation. It did not significantly affect the probability of investigations, referrals or follow-up GP visits for any of the conditions. Unless training has a major influence on consultation length, it is unlikely to have any major impacts on cost.

  8. Digital communication between clinician and patient and the impact on marginalised groups: a realist review in general practice.

    Science.gov (United States)

    Huxley, Caroline J; Atherton, Helen; Watkins, Jocelyn Anstey; Griffiths, Frances

    2015-12-01

    Increasingly, the NHS is embracing the use of digital communication technology for communication between clinicians and patients. Policymakers deem digital clinical communication as presenting a solution to the capacity issues currently faced by general practice. There is some concern that these technologies may exacerbate existing inequalities in accessing health care. It is not known what impact they may have on groups who are already marginalised in their ability to access general practice. To assess the potential impact of the availability of digital clinician-patient communication on marginalised groups' access to general practice in the UK. Realist review in general practice. A four-step realist review process was used: to define the scope of the review; to search for and scrutinise evidence; to extract and synthesise evidence; and to develop a narrative, including hypotheses. Digital communication has the potential to overcome the following barriers for marginalised groups: practical access issues, previous negative experiences with healthcare service/staff, and stigmatising reactions from staff and other patients. It may reduce patient-related barriers by offering anonymity and offers advantages to patients who require an interpreter. It does not impact on inability to communicate with healthcare professionals or on a lack of candidacy. It is likely to work best in the context of a pre-existing clinician-patient relationship. Digital communication technology offers increased opportunities for marginalised groups to access health care. However, it cannot remove all barriers to care for these groups. It is likely that they will remain disadvantaged relative to other population groups after their introduction. © British Journal of General Practice 2015.

  9. "What do you think I should do?": Understanding intercultural medical communication in general practice

    NARCIS (Netherlands)

    Schinkel, S.

    2015-01-01

    Adequate communication between doctors and patients is a crucial aspect of good quality health care. Research has shown that medical communication between doctors and patients from different ethnic and cultural backgrounds is less effective than medical communication between doctors and patients

  10. Identifying context factors explaining physician's low performance in communication assessment: an explorative study in general practice.

    Science.gov (United States)

    Essers, Geurt; van Dulmen, Sandra; van Weel, Chris; van der Vleuten, Cees; Kramer, Anneke

    2011-12-13

    Communication is a key competence for health care professionals. Analysis of registrar and GP communication performance in daily practice, however, suggests a suboptimal application of communication skills. The influence of context factors could reveal why communication performance levels, on average, do not appear adequate. The context of daily practice may require different skills or specific ways of handling these skills, whereas communication skills are mostly treated as generic. So far no empirical analysis of the context has been made. Our aim was to identify context factors that could be related to GP communication. A purposive sample of real-life videotaped GP consultations was analyzed (N = 17). As a frame of reference we chose the MAAS-Global, a widely used assessment instrument for medical communication. By inductive reasoning, we analyzed the GP behaviour in the consultation leading to poor item scores on the MAAS-Global. In these cases we looked for the presence of an intervening context factor, and how this might explain the actual GP communication behaviour. We reached saturation after having viewed 17 consultations. We identified 19 context factors that could potentially explain the deviation from generic recommendations on communication skills. These context factors can be categorized into doctor-related, patient-related, and consultation-related factors. Several context factors seem to influence doctor-patient communication, requiring the GP to apply communication skills differently from recommendations on communication. From this study we conclude that there is a need to explicitly account for context factors in the assessment of GP (and GP registrar) communication performance. The next step is to validate our findings.

  11. Context factors in general practitioner - patient encounters and their impact on assessing communication skills - an exploratory study

    Science.gov (United States)

    2013-01-01

    Background Assessment of medical communication performance usually focuses on rating generically applicable, well-defined communication skills. However, in daily practice, communication is determined by (specific) context factors, such as acquaintance with the patient, or the presented problem. Merely valuing the presence of generic skills may not do justice to the doctor’s proficiency. Our aim was to perform an exploratory study on how assessment of general practitioner (GP) communication performance changes if context factors are explicitly taken into account. Methods We used a mixed method design to explore how ratings would change. A random sample of 40 everyday GP consultations was used to see if previously identified context factors could be observed again. The sample was rated twice using a widely used assessment instrument (the MAAS-Global), first in the standard way and secondly after context factors were explicitly taken into account, by using a context-specific rating protocol to assess communication performance in the workplace. In between first and second rating, the presence of context factors was established. Item score differences were calculated using paired sample t-tests. Results In 38 out of 40 consultations, context factors prompted application of the context-specific rating protocol. Mean overall score on the 7-point MAAS-Global scale increased from 2.98 in standard to 3.66 in the context-specific rating (p communication was set at 3.17. Conclusions Applying the protocol, the mean overall score rose above the level set in an earlier study for the MAAS-Global scores to represent ‘adequate GP communication behaviour’. Our findings indicate that incorporating context factors in communication assessment thus makes a meaningful difference and shows that context factors should be considered as ‘signal’ instead of ‘noise’ in GP communication assessment. Explicating context factors leads to a more deliberate and transparent rating of

  12. A smartphone-enabled communication system to improve hospital communication: usage and perceptions of medical trainees and nurses on general internal medicine wards.

    Science.gov (United States)

    Wu, Robert; Lo, Vivian; Morra, Dante; Appel, Eva; Arany, Teri; Curiale, Beth; Ryan, Joanne; Quan, Sherman

    2015-02-01

    There is increasing interest in the use of information and communication technologies to improve how clinicians communicate in hospital settings. We implemented a communication system with support for physician handover and secure messaging on 2 general internal medicine wards. We measured usage and surveyed physicians and nurses on perceptions of the system's effects on communication. Between May 2011 and August 2012, a clinical teaching team received, on average, 14.8 messages per day through the system. Messages were typically sent as urgent (69.1%) and requested a text reply (76.5%). For messages requesting a text reply, 8.6% did not receive a reply. For those messages that did receive a reply, the median response time was 2.3 minutes, and 84.5% of messages received a reply within 15 minutes. Of those who completed the survey, 95.3% were medical residents (82 of 86) and 81.7% were nurses (83 of 116). Medical trainees (82.8%) and nursing staff (78.3%) agreed or strongly agreed that the system helped to speed up their daily work tasks. Overall, 67.1% of the trainees and 73.2% of nurses agreed or strongly agreed that the system made them more accountable in their clinical roles. Only 35.8% of physicians and 26.3% of nurses agreed or strongly agreed that the system was useful for communicating complex issues. In summary, with a system designed to improve communication, we found that there was high uptake and that users perceived that the system improved efficiency and accountability but was not appropriate for communicating complex issues. © 2014 Society of Hospital Medicine.

  13. Languages, communication potential and generalized trust in Sub-Saharan Africa: evidence based on the Afrobarometer Survey.

    Science.gov (United States)

    Buzasi, Katalin

    2015-01-01

    The goal of this study is to investigate whether speaking other than home languages in Sub-Saharan Africa promotes generalized trust. Based on various psychological and economic theories, a simple model is provided to illustrate how languages might shape trust through various channels. Relying on data from the Afrobarometer Project, which provides information on home and additional languages, the Index of Communication Potential (ICP) is introduced to capture the linguistic situation in the 20 sample countries. The ICP, which can be computed at any desired level of aggregation, refers to the probability that an individual can communicate with a randomly selected person in the society based on common languages. The estimated two-level hierarchical models show that, however, individual level communication potential does not seem to impact trust formation, but living in an area with higher average communication potential increases the chance of exhibiting higher trust toward unknown people. Copyright © 2014 Elsevier Inc. All rights reserved.

  14. Identification of influencing factors and strategies to improve communication between general practitioners and community nurses: a qualitative focus group study.

    Science.gov (United States)

    Nieuwboer, Minke S; Perry, Marieke; van der Sande, Rob; Maassen, Irma T H M; Olde Rikkert, Marcel G M; van der Marck, Marjolein A

    2018-02-26

    As the number of patients with complex healthcare needs grows, inter-professional collaboration between primary care professionals must be constantly optimized. General practitioners (GPs) and community nurses (CNs) are key professions in primary care; however, poor GP-CN communication is common, and research into the factors influencing its quality is limited. To explore patient-related GP-CN communication and facilitating and hindering factors, and to identify strategies to enhance this communication. A qualitative focus group design was used to identify the facilitating and hindering factors and strategies for improvement. In a Dutch primary care setting, 6 mono-professional focus group interviews (3 meetings of 13 GPs; 3 meetings of 18 CNs) were organized between June 2015 and April 2016, recorded and transcribed verbatim. Two independent researchers performed the coding of these interviews, identifying their categories and themes. Results show that, despite the regular contact between GPs and CNs, communication was generally perceived as poor in effectiveness and efficiency by both professions. Mutual trust was considered the most important facilitating factor for effective communication. Profession-specific factors (e.g. differences in responsibility and profession-specific language) and organizational factors (e.g. lack of shared care plans, no in-person communication, lack of time) may be of influence on communication. Participants' suggestions for improvement included organizing well-structured and reimbursed team meetings and facilitating face-to-face contact. GP-CN patient-related communication benefits most from trusting inter-personal relationships. Inter-professional training programmes should address both professional and organizational factors and should be evaluated for their effect on quality of care.

  15. Context factors in general practitioner-patient encounters and their impact on assessing communication skills--an exploratory study.

    Science.gov (United States)

    Essers, Geurt; Kramer, Anneke; Andriesse, Boukje; van Weel, Chris; van der Vleuten, Cees; van Dulmen, Sandra

    2013-05-22

    Assessment of medical communication performance usually focuses on rating generically applicable, well-defined communication skills. However, in daily practice, communication is determined by (specific) context factors, such as acquaintance with the patient, or the presented problem. Merely valuing the presence of generic skills may not do justice to the doctor's proficiency.Our aim was to perform an exploratory study on how assessment of general practitioner (GP) communication performance changes if context factors are explicitly taken into account. We used a mixed method design to explore how ratings would change. A random sample of 40 everyday GP consultations was used to see if previously identified context factors could be observed again. The sample was rated twice using a widely used assessment instrument (the MAAS-Global), first in the standard way and secondly after context factors were explicitly taken into account, by using a context-specific rating protocol to assess communication performance in the workplace. In between first and second rating, the presence of context factors was established. Item score differences were calculated using paired sample t-tests. In 38 out of 40 consultations, context factors prompted application of the context-specific rating protocol. Mean overall score on the 7-point MAAS-Global scale increased from 2.98 in standard to 3.66 in the context-specific rating (pcommunication was set at 3.17. Applying the protocol, the mean overall score rose above the level set in an earlier study for the MAAS-Global scores to represent 'adequate GP communication behaviour'. Our findings indicate that incorporating context factors in communication assessment thus makes a meaningful difference and shows that context factors should be considered as 'signal' instead of 'noise' in GP communication assessment. Explicating context factors leads to a more deliberate and transparent rating of GP communication performance.

  16. Interim Service ISDN Satellite (ISIS) network model for advanced satellite designs and experiments

    Science.gov (United States)

    Pepin, Gerard R.; Hager, E. Paul

    1991-01-01

    The Interim Service Integrated Services Digital Network (ISDN) Satellite (ISIS) Network Model for Advanced Satellite Designs and Experiments describes a model suitable for discrete event simulations. A top-down model design uses the Advanced Communications Technology Satellite (ACTS) as its basis. The ISDN modeling abstractions are added to permit the determination and performance for the NASA Satellite Communications Research (SCAR) Program.

  17. Development of Communicative Tolerance among Teachers of Primary and Senior Level of the General Education School

    Science.gov (United States)

    Povarenkov, Yury P.; Baranova, Nataly A.; Sidorova, Anna D.; Mitiukov, Nicholas W.

    2018-01-01

    The article is devoted to the study of the influence of the level of development of communicative tolerance on the effectiveness of the teaching and educational activity of primary and senior schoolteachers. In the article the concepts of psychophysiological and communicative tolerance are separated. The psychological content of communicative…

  18. 11 CFR 100.26 - Public communication (2 U.S.C. 431(22)).

    Science.gov (United States)

    2010-01-01

    ... communication by means of any broadcast, cable, or satellite communication, newspaper, magazine, outdoor advertising facility, mass mailing, or telephone bank to the general public, or any other form of general public political advertising. The term general public political advertising shall not include...

  19. Telelibrary: Library Services via Satellite.

    Science.gov (United States)

    Liu, Rosa

    1979-01-01

    Investigates the provision of library services via satellite, explains briefly the operation and advantages of communication satellites, and discusses the various telecommunications equipment and services which, when coupled with satellite transmission, will enhance library activities. Demand trend projections for telecommunications services…

  20. Examination of aerosol distributions and radiative effects over the Bay of Bengal and the Arabian Sea region during ICARB using satellite data and a general circulation model

    Directory of Open Access Journals (Sweden)

    R. Cherian

    2012-02-01

    Full Text Available In this paper we analyse aerosol loading and its direct radiative effects over the Bay of Bengal (BoB and Arabian Sea (AS regions for the Integrated Campaign on Aerosols, gases and Radiation Budget (ICARB undertaken during 2006, using satellite data from the MODerate Resolution Imaging Spectroradiometer (MODIS on board the Terra and Aqua satellites, the Aerosol Index from the Ozone Monitoring Instrument (OMI on board the Aura satellite, and the European-Community Hamburg (ECHAM5.5 general circulation model extended by Hamburg Aerosol Module (HAM. By statistically comparing with large-scale satellite data sets, we firstly show that the aerosol properties measured during the ship-based ICARB campaign and simulated by the model are representative for the BoB and AS regions and the pre-monsoon season. In a second step, the modelled aerosol distributions were evaluated by a comparison with the measurements from the ship-based sunphotometer, and the satellite retrievals during ICARB. It is found that the model broadly reproduces the observed spatial and temporal variability in aerosol optical depth (AOD over BoB and AS regions. However, AOD was systematically underestimated during high-pollution episodes, especially in the BoB leg. We show that this underprediction of AOD is mostly because of the deficiencies in the coarse mode, where the model shows that dust is the dominant component. The analysis of dust AOD along with the OMI Aerosol Index indicate that missing dust transport that results from too low dust emission fluxes over the Thar Desert region in the model caused this deficiency. Thirdly, we analysed the spatio-temporal variability of AOD comparing the ship-based observations to the large-scale satellite observations and simulations. It was found that most of the variability along the track was from geographical patterns, with a minor influence by single events. Aerosol fields were homogeneous enough to yield a good statistical agreement

  1. A test of general relativity using the LARES and LAGEOS satellites and a GRACE Earth gravity model. Measurement of Earth's dragging of inertial frames

    Energy Technology Data Exchange (ETDEWEB)

    Ciufolini, Ignazio [Universita del Salento, Dipartimento Ingegneria dell' Innovazione, Lecce (Italy); Sapienza Universita di Roma, Scuola di Ingegneria Aerospaziale, Rome (Italy); Paolozzi, Antonio; Paris, Claudio [Sapienza Universita di Roma, Scuola di Ingegneria Aerospaziale, Rome (Italy); Museo della Fisica e Centro Studi e Ricerche Enrico Fermi, Rome (Italy); Pavlis, Erricos C. [University of Maryland, Joint Center for Earth Systems Technology (JCET), Baltimore County (United States); Koenig, Rolf [GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Potsdam (Germany); Ries, John [University of Texas at Austin, Center for Space Research, Austin (United States); Gurzadyan, Vahe; Khachatryan, Harutyun; Mirzoyan, Sergey [Alikhanian National Laboratory and Yerevan State University, Center for Cosmology and Astrophysics, Yerevan (Armenia); Matzner, Richard [University of Texas at Austin, Theory Center, Austin (United States); Penrose, Roger [University of Oxford, Mathematical Institute, Oxford (United Kingdom); Sindoni, Giampiero [Sapienza Universita di Roma, DIAEE, Rome (Italy)

    2016-03-15

    We present a test of general relativity, the measurement of the Earth's dragging of inertial frames. Our result is obtained using about 3.5 years of laser-ranged observations of the LARES, LAGEOS, and LAGEOS 2 laser-ranged satellites together with the Earth gravity field model GGM05S produced by the space geodesy mission GRACE. We measure μ = (0.994 ± 0.002) ± 0.05, where μ is the Earth's dragging of inertial frames normalized to its general relativity value, 0.002 is the 1-sigma formal error and 0.05 is our preliminary estimate of systematic error mainly due to the uncertainties in the Earth gravity model GGM05S. Our result is in agreement with the prediction of general relativity. (orig.)

  2. A test of general relativity using the LARES and LAGEOS satellites and a GRACE Earth gravity model: Measurement of Earth's dragging of inertial frames.

    Science.gov (United States)

    Ciufolini, Ignazio; Paolozzi, Antonio; Pavlis, Erricos C; Koenig, Rolf; Ries, John; Gurzadyan, Vahe; Matzner, Richard; Penrose, Roger; Sindoni, Giampiero; Paris, Claudio; Khachatryan, Harutyun; Mirzoyan, Sergey

    2016-01-01

    We present a test of general relativity, the measurement of the Earth's dragging of inertial frames. Our result is obtained using about 3.5 years of laser-ranged observations of the LARES, LAGEOS, and LAGEOS 2 laser-ranged satellites together with the Earth gravity field model GGM05S produced by the space geodesy mission GRACE. We measure [Formula: see text], where [Formula: see text] is the Earth's dragging of inertial frames normalized to its general relativity value, 0.002 is the 1-sigma formal error and 0.05 is our preliminary estimate of systematic error mainly due to the uncertainties in the Earth gravity model GGM05S. Our result is in agreement with the prediction of general relativity.

  3. A satellite mobile communication system based on Band-Limited Quasi-Synchronous Code Division Multiple Access (BLQS-CDMA)

    Science.gov (United States)

    Degaudenzi, R.; Elia, C.; Viola, R.

    1990-01-01

    Discussed here is a new approach to code division multiple access applied to a mobile system for voice (and data) services based on Band Limited Quasi Synchronous Code Division Multiple Access (BLQS-CDMA). The system requires users to be chip synchronized to reduce the contribution of self-interference and to make use of voice activation in order to increase the satellite power efficiency. In order to achieve spectral efficiency, Nyquist chip pulse shaping is used with no detection performance impairment. The synchronization problems are solved in the forward link by distributing a master code, whereas carrier forced activation and closed loop control techniques have been adopted in the return link. System performance sensitivity to nonlinear amplification and timing/frequency synchronization errors are analyzed.

  4. Communicating polar science to the general public: sharing the social media experience of @OceanSeaIceNPI

    Science.gov (United States)

    Rösel, Anja; Pavlov, Alexey K.; Granskog, Mats A.; Gerland, Sebastian; Meyer, Amelie; Hudson, Stephen R.; King, Jennifer; Itkin, Polona; Cohen, Lana; Dodd, Paul; de Steur, Laura

    2016-04-01

    The findings of climate science need to be communicated to the general public. Researchers are encouraged to do so by journalists, policy-makers and funding agencies and many of us want to become better science communicators. But how can we do this at the lab or small research group level without specifically allocated resources in terms of funds and communication officers? And how do we sustain communication on a regular basis and not just during the limited lifetime of a specific project? One of the solutions is to use the emerging platform of social media, which has become a powerful and inexpensive tool for communicating science to different target audiences. Many research institutions and individual researchers are already advanced users of social media, but small research groups and labs remain underrepresented. The group of oceanographers, sea ice and atmospheric scientists at the Norwegian Polar Institute (@OceanSeaIceNPI( will share our experiences developing and maintaining researcher-driven outreach for over a year through Instagram, Twitter and Facebook. We will present our solutions to some of the practical considerations such as identifying key target groups, defining the framework for sharing responsibilities and interactions within the research group, and choosing an up-to-date and appropriate social medium. By sharing this information, we aim to inspire and assist other research groups and labs in conducting their own effective science communication.

  5. Address on the Occasion of the Meeting of the Second Committee of Governmental Experts on Problems in the Field of Copyright and of the Protection of Performers, Producers of Phonograms and Broadcasting Organizations Raised by Transmission via Space Satellites.

    Science.gov (United States)

    Maheu, Rene

    These opening remarks by the Director General of Unesco briefly discuss that organization's activities in the area of copyright within the field of satellite communication. They were addressed to members of a committee whose purpose is to determine whether the protection of signals transmitted by communications satellites does or does not require…

  6. Communication and Consultation with Interested Parties by the Regulatory Body. General Safety Guide

    International Nuclear Information System (INIS)

    2017-01-01

    This Safety Guide provides recommendations on meeting the safety requirements concerning communication and consultation with the public and other interested parties by the regulatory body about the possible radiation risks associated with facilities and activities, and about processes and decisions of the regulatory body. The Safety Guide can be used by authorized parties in circumstances where there are regulatory requirements placed on them for communication and consultation. It may also be used by other organizations or individuals considering their responsibilities for communication and consultation with interested parties.

  7. [Patient-centered care. Improvement of communication between university medical centers and general practitioners for patients in neuro-oncology].

    Science.gov (United States)

    Renovanz, M; Keric, N; Richter, C; Gutenberg, A; Giese, A

    2015-12-01

    Communication between university medical centers and general practitioners (GP) is becoming increasingly more important in supportive patient care. A survey among GPs was performed with the primary objective to assess their opinion on current workflow and communication between GPs and the university medical center. The GPs were asked to score (grades 1-6) their opinion on the current interdisciplinary workflow in the care of patients with brain tumors, thereby rating communication between a university medical center in general and the neuro-oncology outpatient center in particular. Questionnaires were sent to1000 GPs and the response rate was 15 %. The mean scored evaluation of the university medical center in general was 2.62 and of the neuro-oncological outpatient clinic 2.28 (range 1-6). The most often mentioned issues to be improved were easier/early telephone information (44 %) and a constantly available contact person (49 %). Interestingly, > 60 % of the GPs indicated they would support web-based tumor boards for interdisciplinary and palliative neuro-oncological care. As interdisciplinary care for neuro-oncology patients is an essential part of therapy, improvement of communication between GPs and university medical centers is indispensable. Integrating currently available electronic platforms under data protection aspects into neuro-oncological palliative care could be an interesting tool in order to establish healthcare networks and could find acceptance with GPs.

  8. 47 CFR 25.279 - Inter-satellite service.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Inter-satellite service. 25.279 Section 25.279 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Operations § 25.279 Inter-satellite service. (a) Any satellite communicating with other space...

  9. A Global System of in situ Sensors, Communication Satellites and in situ Actuators Dedicated to the Nearly-Real-Time Detection and Mitigation of Natural Disasters

    Science.gov (United States)

    Bevis, M.

    2009-05-01

    Most of the ~ 230,000 lives lost in the Indian Ocean Tsunami of December 2004 could have been saved if the victims had had 5 - 15 minutes notice of the tsunami's arrival, provided that the local authorities had had some evacuation plan in place, e.g. running up hill when a klaxon sounded, or retreating to low cost shelters constructed to provide a vertical escape from inundation. Similar structures, equipped with supplies of drinking water, food, blankets, etc., could save countless thousands of people from drowning in flood-prone locations such as Bangladesh or the delta region of Burma, or dying in the aftermath of such events. Given sufficiently rapid communications, a disaster nowcasting system could also order the closing of gas mains, or the powering down of electricity networks, as well as the sounding of klaxons, only tens of seconds before an earthquake wave strikes a major city such as Los Angeles. The central and critical requirement for mitigating natural disasters is two-way communication. Imagine a globally accessible internet collecting event-triggered messages from arrays of sensors (that detect inundation, for example) so they can be analyzed by centralized computer systems in nearly real-time, which then send instructions to alarm systems and actuators in the areas at risk. (Of course, local authorities would have to be involved in planning the local responses to alarms, in constructing rescue facilities, and in educating their populations accordingly). Only a constellation of satellites could provide a communications system with global accessibility and the required robustness. Such an infrastructure would allow the international community to exploit the many common elements in the detection, assessment and response to unfolding disasters. I shall describe some of the elements of such a system, for which I propose the working name CELERITY.

  10. Are managers' and the general public's perceptions of risk communication needs in line? A French alpine valley case study

    Science.gov (United States)

    Charrière, Marie; Sprague, Teresa; Bogaard, Thom; Greiving, Stefan; Malet, Jean-Philippe; Mostert, Erik

    2013-04-01

    Risk communication is a crucial element of risk management. It contributes to social capacity building by influencing the knowledge, attitude, behavior, psychology, as well as social and organizational aspects1,2. It is globally recognized that effective risk communication should address needs and requirements of targeted audiences, especially those of the public. This study compares needs and requirements related to risk communication as seen by the risk managers, with the needs and requirements as expressed by the general public. Two surveys were conducted in a mountainous region facing multi-hazards, the Ubaye valley (France). The first survey, conducted within the context of the Marie Curie Research and Training Network 'Mountain Risk', was addressed to the local community. It aimed at gathering perceptions, needs and requirements of the general public (344 respondents) on risk communication3. The second survey, conducted in the context of the Marie Curie Initial Training Network 'CHANGES', targeted risk managers (16 stakeholders of the authorities, technical services and emergency units) at both the local and the regional scale to evaluate their perceptions regarding risk communication with the general public. The needs and requirements were analyzed with respect to several dimensions: 1) the information provided to the public, 2) the legal requirements for communication, 3) the level of trust the population has in risk managers, 4) insights on awareness and preparedness, and 5) information on the media used in past communication efforts. Results of the analysis concerning the last dimension reveal that, while the general public mentioned press, official reports and technical reports as the top three media by which they received information, the risk managers cited the press but in contrast also selected radio and television. Other results indicate that a potential mismatch exists as more than 80% of the respondents of the population find all listed topics

  11. Using information and communication technologies to consult with patients in Victorian primary care: the views of general practitioners.

    Science.gov (United States)

    Hanna, Lisa; Fairhurst, Karen

    2013-01-01

    Information and communication technologies such as email, text messaging and video messaging are commonly used by the general population. However, international research has shown that they are not used routinely by GPs to communicate or consult with patients. Investigating Victorian GPs' perceptions of doing so is timely given Australia's new National Broadband Network, which may facilitate web-based modes of doctor-patient interaction. This study therefore aimed to explore Victorian GPs' experiences of, and attitudes toward, using information and communication technologies to consult with patients. Qualitative telephone interviews were carried out with a maximum variation sample of 36GPs from across Victoria. GPs reported a range of perspectives on using new consultation technologies within their practice. Common concerns included medico-legal and remuneration issues and perceived patient information technology literacy. Policy makers should incorporate GPs' perspectives into primary care service delivery planning to promote the effective use of information and communication technologies in improving accessibility and quality of general practice care.

  12. A novel unified expression for the capacity and bit error probability of wireless communication systems over generalized fading channels

    KAUST Repository

    Yilmaz, Ferkan

    2012-07-01

    Analysis of the average binary error probabilities (ABEP) and average capacity (AC) of wireless communications systems over generalized fading channels have been considered separately in past years. This paper introduces a novel moment generating function (MGF)-based unified expression for the ABEP and AC of single and multiple link communications with maximal ratio combining. In addition, this paper proposes the hyper-Fox\\'s H fading model as a unified fading distribution of a majority of the well-known generalized fading environments. As such, the authors offer a generic unified performance expression that can be easily calculated, and that is applicable to a wide variety of fading scenarios. The mathematical formulism is illustrated with some selected numerical examples that validate the correctness of the authors\\' newly derived results. © 1972-2012 IEEE.

  13. Resource effects of training general practitioners in risk communication skills and shared decision making competences.

    NARCIS (Netherlands)

    Cohen, D.; Longo, M.F.; Hood, K.; Edwards, A.; Elwyn, G.

    2004-01-01

    RATIONALE, AIMS AND OBJECTIVES: Involving patients more in decisions about their own care requires doctors to be trained in effective ways of communicating information and in developing competences to negotiate levels of patient involvement which are most appropriate for each case. The aim of this

  14. Unraveling the Administrative Tangles in JMU's Speech Communication and General Education Programs.

    Science.gov (United States)

    Emmert, Philip; Smilowitz, Michael

    What has transpired at James Madison University provides a model for the successful implementation of a basic communication education program required of all first-year students. This paper provides an accounting of the efforts that made possible the commitment to the development of the program. The paper is first divided into two columns. One…

  15. Developing a General Outcome Measure of Growth in the Expressive Communication of Infants and Toddlers.

    Science.gov (United States)

    Luze, Gayle J.; Linebarger, Deborah L.; Greenwood, Charles R.; Carta, Judith J.; Walker, Dale; Leitschuh, Carol; Atwater, Jane B.

    2001-01-01

    Describes the development of an experimental measure for assessing growth in expressive communication in children from birth to 3 years of age Results from a sample of 50 infants and toddlers assessed monthly for 9 months in indicated that the measure displayed adequate psychometric properties of reliability and validity and was sensitive to…

  16. Patient anxiety in the medical encounter: a study of verbal and nonverbal communication in general practice.

    NARCIS (Netherlands)

    Bensing, J.M.; Verheul, W.; Dulmen, A.M. van

    2008-01-01

    Purpose: Many patients feel anxious when entering the consultation room, but seldom verbalize their emotions explicitly in the medical encounter. The authors designed a study to analyse the visibility of patient pre-consultation (state) anxiety in their communication during the consultation. In an

  17. Performances des applications IP dans les systèmes de communications par satellite : cas du DVB-RCS et du DVB-S2

    OpenAIRE

    Jegham , Nizar

    2008-01-01

    Despite of a number of IP satellite networks developed and deployed, only a limited number of studies and feedbacks about the performance is available. IP over satellite systems raises several constraints. One of the main reasons is the lack of adaptation of IP protocol, initially designed for terrestrial wired networks, to the large bandwidth delay product of the satellite media. Another reason is a lack of coordination between the IP protocol stack upper layer and the satellite MAC and phys...

  18. The European project Hippo high-power photonics for satellite laser communications and on-board optical processing

    Science.gov (United States)

    Kehayas, E.; Stampoulidis, L.; Henderson, P.; Robertson, Andrew; Van Dijk, F.; Achouche, M.; Le Kernec, A.; Sotom, M.; Schuberts, F.; Brabant, T.

    2017-11-01

    Photonics is progressively transforming from a highly- focused technology applicable to digital communication networks into a pervasive "enabling" technology with diverse non-telecom applications. However, the centre of mass on the R&D level is still mostly driven by, and invested in, by stakeholders active in the telecoms domain. This is due to the high level of investments necessary that in turn require a large and established market for reaching break-even and generation of revenues. Photonics technology and more specifically, fibre-optic technology is moving into non-telecom business areas with great success in terms of markets captured and penetration rates. One example that cannot be overlooked is the application of fibre-optics to industrial applications, where double-digit growth rates are recorded with fibre lasers and amplifiers constantly gaining momentum. In this example, several years of R&D efforts in creating high-power amplification solutions and fibre-laser sources by the telecom sector, were piggy-backed into industrial applications and laser cutting/welding equipment that is now a strong R&D sector on its own and commercially now displacing some conventional free space laser cutting/welding.

  19. Advanced communications technology satellite high burst rate link evaluation terminal power control and rain fade software test plan, version 1.0

    Science.gov (United States)

    Reinhart, Richard C.

    1993-01-01

    The Power Control and Rain Fade Software was developed at the NASA Lewis Research Center to support the Advanced Communications Technology Satellite High Burst Rate Link Evaluation Terminal (ACTS HBR-LET). The HBR-LET is an experimenters terminal to communicate with the ACTS for various experiments by government, university, and industry agencies. The Power Control and Rain Fade Software is one segment of the Control and Performance Monitor (C&PM) Software system of the HBR-LET. The Power Control and Rain Fade Software automatically controls the LET uplink power to compensate for signal fades. Besides power augmentation, the C&PM Software system is also responsible for instrument control during HBR-LET experiments, control of the Intermediate Frequency Switch Matrix on board the ACTS to yield a desired path through the spacecraft payload, and data display. The Power Control and Rain Fade Software User's Guide, Version 1.0 outlines the commands and procedures to install and operate the Power Control and Rain Fade Software. The Power Control and Rain Fade Software Maintenance Manual, Version 1.0 is a programmer's guide to the Power Control and Rain Fade Software. This manual details the current implementation of the software from a technical perspective. Included is an overview of the Power Control and Rain Fade Software, computer algorithms, format representations, and computer hardware configuration. The Power Control and Rain Fade Test Plan provides a step-by-step procedure to verify the operation of the software using a predetermined signal fade event. The Test Plan also provides a means to demonstrate the capability of the software.

  20. COMMUNICATIONS

    CERN Multimedia

    L. Taylor and D. Barney

    2010-01-01

    CMS Centres, Outreach and the 7 TeV Media Event The new CMS Communications group is now established and is addressing three areas that are critical to CMS as it enters the physics operations phase: - Communications Infrastructure, including almost 50 CMS Centres Worldwide, videoconferencing systems, and CERN meeting rooms - Information systems, including the internal and external Web sites as well as the document preparation and management systems - Outreach and Education activities, including working with print, radio and TV media, visits to CMS, and exhibitions. The group has been active in many areas, with the highest priority being accorded to needs of CMS operations and preparations for the major media event planned for 7 TeV collisions. Unfortunately the CMS Centre@CERN suffered a major setback when, on 21st December, a cooling water pipe froze and burst on the floor above the CMS Centre main room. Water poured through the ceiling, flooding the floor and soaking some of the consoles, before e...

  1. Legal Organizations: Communicative Actions the Attorney General of the State of Tamaulipas, Mexico

    Directory of Open Access Journals (Sweden)

    Mercedes Cancelo Sanmartin

    2012-11-01

    Full Text Available This text provides a descriptive study of the communicative exercise of the main legal body in Mexico, specifically in the State of Tamaulipas. Tamaulipas is a State located in the North of the country on border with United States of America. By its geographical location it is a territory with a special legal situation, specifically with regard to safety aspects refers. Faced with this reality the social bodies, and specifically the people have a certain perception of public institutions operating in the field of safety and the prevention of crime, with special attention to the State Attorney. The aforementioned body is charged with managing all complaints and actions involving the citizen. Its effective communication, and their careful image, will depend on the credibility in the development of its public action and therefore its social legitimacy.

  2. Improving communication in general practice when mental health issues appear: piloting a set of six evidence-based skills.

    Science.gov (United States)

    Stensrud, Tonje Lauritzen; Gulbrandsen, Pål; Mjaaland, Trond Arne; Skretting, Sidsel; Finset, Arnstein

    2014-04-01

    To test a communication skills training program teaching general practitioners (GPs) a set of six evidence-based mental health related skills. A training program was developed and tested in a pilot test-retest study with 21 GPs. Consultations were videotaped and actors used as patients. A coding scheme was created to assess the effect of training on GP behavior. Relevant utterances were categorized as examples of each of the six specified skills. The GPs' self-perceived learning needs and self-efficacy were measured with questionnaires. The mean number of GP utterances related to the six skills increased from 13.3 (SD 6.2) utterances before to 23.6 (SD 7.2) utterances after training; an increase of 77.4% (PSkills exploring emotions, cognitions and resources, and the skill Promote coping, increased significantly. Self-perceived learning needs and self-efficacy did not change significantly. The results from this pilot test are encouraging. GPs enhanced their use on four out of six mental health related communication skills significantly, and the effects were medium to large. This training approach appears to be an efficacious approach to mental health related communication skills training in general practice. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  3. Satellite Antenna Pointing Procedure Driven by the Ground Service Quality

    Science.gov (United States)

    Yasui, Yoshitsugu

    A satellite antenna alignment technique is proposed to ensure terrestrial service quality for users. The antenna bore sight orientation is calculated directly from measured data acquired from general ground receivers, which intercept the communication radio waves from any position on the earth's surface. The method coordinates the satellite pointing parameters with signal strength at the receivers while considering location-specific geographical and antenna radiation characteristics and control accuracy. The theoretical development and its validity are examined in the course of equation derivation. Actual measured data of an existing satellite at the maneuver was applied to the method, and the capability was demonstrated and verified. With the wide diversity of satellite usage, such as for mobile communications, temporary network deployment or post-launch positioning accommodations, the proposed method provides a direct evaluation of satellite communication performance at the service level, in conjunction with using high frequency spot beam antennas, which are highly susceptible to pointing gain. This can facilitate swift and flexible satellite service planning and deployment for operators.

  4. Gender and communication style in general practice: differences between women's health care and regular health care.

    NARCIS (Netherlands)

    Brink-Muinen, A. van den; Bensing, J.M.; Kerssens, J.J.

    1998-01-01

    Objectives: differences were investigated between general practitioners providing women's health care (4 women) and general practitioners providing regular health care (8 women and 8 men). Expectations were formulated on the basis of the principles of women's health care and literature about gender

  5. Randomised controlled trial of a brief intervention targeting predominantly non-verbal communication in general practice consultations.

    Science.gov (United States)

    Little, Paul; White, Peter; Kelly, Joanne; Everitt, Hazel; Mercer, Stewart

    2015-06-01

    The impact of changing non-verbal consultation behaviours is unknown. To assess brief physician training on improving predominantly non-verbal communication. Cluster randomised parallel group trial among adults aged ≥16 years attending general practices close to the study coordinating centres in Southampton. Sixteen GPs were randomised to no training, or training consisting of a brief presentation of behaviours identified from a prior study (acronym KEPe Warm: demonstrating Knowledge of the patient; Encouraging [back-channelling by saying 'hmm', for example]; Physically engaging [touch, gestures, slight lean]; Warm-up: cool/professional initially, warming up, avoiding distancing or non-verbal cut-offs at the end of the consultation); and encouragement to reflect on videos of their consultation. Outcomes were the Medical Interview Satisfaction Scale (MISS) mean item score (1-7) and patients' perceptions of other domains of communication. Intervention participants scored higher MISS overall (0.23, 95% confidence interval [CI] = 0.06 to 0.41), with the largest changes in the distress-relief and perceived relationship subscales. Significant improvement occurred in perceived communication/partnership (0.29, 95% CI = 0.09 to 0.49) and health promotion (0.26, 95% CI = 0.05 to 0.46). Non-significant improvements occurred in perceptions of a personal relationship, a positive approach, and understanding the effects of the illness on life. Brief training of GPs in predominantly non-verbal communication in the consultation and reflection on consultation videotapes improves patients' perceptions of satisfaction, distress, a partnership approach, and health promotion. © British Journal of General Practice 2015.

  6. Emotions in communication skills training - experiences from general practice to Porsche maintenance.

    Science.gov (United States)

    Lundeby, Tonje; Jacobsen, Henrik Børsting; Lundeby, Paul Andreas; Loge, Jon Håvard

    2017-11-01

    The emphasis on skills in communication training of physicians has gained momentum over the last 30 years. Furthermore, a specific focus on skills to address emotions has been suggested and more recently supported by empirical studies. In this paper we use the Expanded Four Habits Model to illustrate how a structured consultation model supplemented with specific skills to address emotions is considered useful in medical and non-medical settings. The primacy of emotions in different types of professional encounters is discussed in relation to education and practice. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Internet and Social Media For Health-Related Information and Communication in Health Care: Preferences of the Dutch General Population

    Science.gov (United States)

    Engelen, Lucien JLPG; Berben, Sivera AA; Teerenstra, Steven; Samsom, Melvin; Schoonhoven, Lisette

    2013-01-01

    Background Health care is increasingly featured by the use of Web 2.0 communication and collaborative technologies that are reshaping the way patients and professionals interact. These technologies or tools can be used for a variety of purposes: to instantly debate issues, discover news, analyze research, network with peers, crowd-source information, seek support, and provide advice. Not all tools are implemented successfully; in many cases, the nonusage attrition rates are high. Little is known about the preferences of the Dutch general population regarding the use of the Internet and social media in health care. Objective To determine the preferences of the general population in the Netherlands regarding the use of the Internet and social media in health care. Methods A cross-sectional survey was disseminated via a popular Dutch online social network. Respondents were asked where they searched for health-related information, how they qualified the value of different sources, and their preferences regarding online communication with health care providers. Results were weighed for the Dutch population based on gender, age, and level of education using official statistics. Numbers and percentages or means and standard deviations were presented for different subgroups. One-way ANOVA was used to test for statistical differences. Results The survey was completed by 635 respondents. The Internet was found to be the number one source for health-related information (82.7%), closely followed by information provided by health care professionals (71.1%). Approximately one-third (32.3%) of the Dutch population search for ratings of health care providers. The most popular information topics were side effects of medication (62.5%) and symptoms (59.7%). Approximately one-quarter of the Dutch population prefer to communicate with a health care provider via social media (25.4%), and 21.2% would like to communicate via a webcam. Conclusions The Internet is the main source of health

  8. Internet and social media for health-related information and communication in health care: preferences of the Dutch general population.

    Science.gov (United States)

    Van de Belt, Tom H; Engelen, Lucien J L P G; Berben, Sivera A A; Teerenstra, Steven; Samsom, Melvin; Schoonhoven, Lisette

    2013-10-02

    Health care is increasingly featured by the use of Web 2.0 communication and collaborative technologies that are reshaping the way patients and professionals interact. These technologies or tools can be used for a variety of purposes: to instantly debate issues, discover news, analyze research, network with peers, crowd-source information, seek support, and provide advice. Not all tools are implemented successfully; in many cases, the nonusage attrition rates are high. Little is known about the preferences of the Dutch general population regarding the use of the Internet and social media in health care. To determine the preferences of the general population in the Netherlands regarding the use of the Internet and social media in health care. A cross-sectional survey was disseminated via a popular Dutch online social network. Respondents were asked where they searched for health-related information, how they qualified the value of different sources, and their preferences regarding online communication with health care providers. Results were weighed for the Dutch population based on gender, age, and level of education using official statistics. Numbers and percentages or means and standard deviations were presented for different subgroups. One-way ANOVA was used to test for statistical differences. The survey was completed by 635 respondents. The Internet was found to be the number one source for health-related information (82.7%), closely followed by information provided by health care professionals (71.1%). Approximately one-third (32.3%) of the Dutch population search for ratings of health care providers. The most popular information topics were side effects of medication (62.5%) and symptoms (59.7%). Approximately one-quarter of the Dutch population prefer to communicate with a health care provider via social media (25.4%), and 21.2% would like to communicate via a webcam. The Internet is the main source of health-related information for the Dutch population

  9. 47 CFR 25.272 - General inter-system coordination procedures.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false General inter-system coordination procedures. 25.272 Section 25.272 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Operations § 25.272 General inter-system coordination...

  10. A new laser-ranged satellite for General Relativity and space geodesy: I. An introduction to the LARES2 space experiment

    Science.gov (United States)

    Ciufolini, Ignazio; Paolozzi, Antonio; Pavlis, Erricos C.; Sindoni, Giampiero; Koenig, Rolf; Ries, John C.; Matzner, Richard; Gurzadyan, Vahe; Penrose, Roger; Rubincam, David; Paris, Claudio

    2017-08-01

    We introduce the LARES 2 space experiment recently approved by the Italian Space Agency (ASI). The LARES 2 satellite is planned for launch in 2019 with the new VEGA C launch vehicle of ASI, ESA and ELV. The orbital analysis of LARES 2 experiment will be carried out by our international science team of experts in General Relativity, theoretical physics, space geodesy and aerospace engineering. The main objectives of the LARES 2 experiment are gravitational and fundamental physics, including accurate measurements of General Relativity, in particular a test of frame-dragging aimed at achieving an accuracy of a few parts in a thousand, i.e., aimed at improving by about an order of magnitude the present state-of-the-art and forthcoming tests of this general relativistic phenomenon. LARES 2 will also achieve determinations in space geodesy. LARES 2 is an improved version of the LAGEOS 3 experiment, proposed in 1984 to measure frame-dragging and analyzed in 1989 by a joint ASI and NASA study.

  11. Interim Service ISDN Satellite (ISIS) simulator development for advanced satellite designs and experiments

    Science.gov (United States)

    Pepin, Gerard R.

    1992-01-01

    The simulation development associated with the network models of both the Interim Service Integrated Services Digital Network (ISDN) Satellite (ISIS) and the Full Service ISDN Satellite (FSIS) architectures is documented. The ISIS Network Model design represents satellite systems like the Advanced Communications Technology Satellite (ACTS) orbiting switch. The FSIS architecture, the ultimate aim of this element of the Satellite Communications Applications Research (SCAR) Program, moves all control and switching functions on-board the next generation ISDN communications satellite. The technical and operational parameters for the advanced ISDN communications satellite design will be obtained from the simulation of ISIS and FSIS engineering software models for their major subsystems. Discrete event simulation experiments will be performed with these models using various traffic scenarios, design parameters, and operational procedures. The data from these simulations will be used to determine the engineering parameters for the advanced ISDN communications satellite.

  12. cMsg - A general purpose, publish-subscribe, interprocess communication implementation and framework

    International Nuclear Information System (INIS)

    Timmer, C; Abbott, D; Gyurjyan, V; Heyes, G; Jastrzembski, E; Wolin, E

    2008-01-01

    cMsg is software used to send and receive messages in the Jefferson Lab online and runcontrol systems. It was created to replace the several IPC software packages in use with a single API. cMsg is asynchronous in nature, running a callback for each message received. However, it also includes synchronous routines for convenience. On the framework level, cMsg is a thin API layer in Java, C, or C++ that can be used to wrap most message-based interprocess communication protocols. The top layer of cMsg uses this same API and multiplexes user calls to one of many such wrapped protocols (or domains) based on a URL-like string which we call a Uniform Domain Locator or UDL. One such domain is a complete implementation of a publish-subscribe messaging system using network communications and written in Java (user APIs in C and C++ too). This domain is built in a way which allows it to be used as a proxy server to other domains (protocols). Performance is excellent allowing the system not only to be used for messaging but also as a data distribution system

  13. Cooperative and cognitive satellite systems

    CERN Document Server

    Chatzinotas, Symeon; De Gaudenzi, Riccardo

    2015-01-01

    Cooperative and Cognitive Satellite Systems provides a solid overview of the current research in the field of cooperative and cognitive satellite systems, helping users understand how to incorporate state-of-the-art communication techniques in innovative satellite network architectures to enable the next generation of satellite systems. The book is edited and written by top researchers and practitioners in the field, providing a comprehensive explanation of current research that allows users to discover future technologies and their applications, integrate satellite and terrestrial systems

  14. A statistical rain attenuation prediction model with application to the advanced communication technology satellite project. 1: Theoretical development and application to yearly predictions for selected cities in the United States

    Science.gov (United States)

    Manning, Robert M.

    1986-01-01

    A rain attenuation prediction model is described for use in calculating satellite communication link availability for any specific location in the world that is characterized by an extended record of rainfall. Such a formalism is necessary for the accurate assessment of such availability predictions in the case of the small user-terminal concept of the Advanced Communication Technology Satellite (ACTS) Project. The model employs the theory of extreme value statistics to generate the necessary statistical rainrate parameters from rain data in the form compiled by the National Weather Service. These location dependent rain statistics are then applied to a rain attenuation model to obtain a yearly prediction of the occurrence of attenuation on any satellite link at that location. The predictions of this model are compared to those of the Crane Two-Component Rain Model and some empirical data and found to be very good. The model is then used to calculate rain attenuation statistics at 59 locations in the United States (including Alaska and Hawaii) for the 20 GHz downlinks and 30 GHz uplinks of the proposed ACTS system. The flexibility of this modeling formalism is such that it allows a complete and unified treatment of the temporal aspects of rain attenuation that leads to the design of an optimum stochastic power control algorithm, the purpose of which is to efficiently counter such rain fades on a satellite link.

  15. An evaluation of the generalization and maintenance of functional communication and self-control skills with preschoolers.

    Science.gov (United States)

    Luczynski, Kevin C; Hanley, Gregory P; Rodriguez, Nicole M

    2014-01-01

    The preschool life skills (PLS) program (Hanley, Heal, Tiger, & Ingvarsson, 2007; Luczynski & Hanley, 2013) involves teaching social skills as a means of decreasing and preventing problem behavior. However, achieving durable outcomes as children transition across educational settings depend on the generalization and long-term maintenance of those skills. The purpose of this study was to evaluate procedures for promoting generalization and long-term maintenance of functional communication and self-control skills for 6 preschool children. When the children's social skills decreased across repeated observations during a generalization assessment, we incorporated modifications to the teaching procedures. However, the effects of the modifications were variable across skills and children. Satisfactory generalization was observed only after the teacher was informed of the target skills and teaching strategies. Maintenance of most social skills was observed 3 months after teaching was discontinued. We discuss the importance of improving child and teacher behavior to promote generalization and maintenance of important social skills. © Society for the Experimental Analysis of Behavior.

  16. Performance evaluation of generalized M-modeled atmospheric optical communications links

    DEFF Research Database (Denmark)

    Lopez-Gonzalez, Francisco J.; Garrido-Balsellss, José María; Jurado-Navas, Antonio

    2016-01-01

    , the behavior of the atmospheric optical channel is treated as a superposition of a finite number of Generalized-K distributed sub-channels, controlled by a discrete Negative-Binomial distribution dependent on the turbulence parameters. Unlike other studies, here, the closed-form mathematical expressions...

  17. Communicating the science of the 11-year sunspot cycle to the general public

    Science.gov (United States)

    Choudhuri, A. R.

    2015-03-01

    Astrophysics is one branch of science which excites the imagination of the general public. Pioneer science popularizers like George Gamow and Fred Hoyle wrote on different aspects of astrophysics. However, of late, we see a trend which I find disturbing. While it has become extremely fashionable to write popular science books on cosmology, other areas of astrophysics are grossly neglected.

  18. IBM Demonstrates a General-Purpose, High-Performance, High-Availability Cloud-Hosted Data Distribution System With Live GOES-16 Weather Satellite Data

    Science.gov (United States)

    Snyder, P. L.; Brown, V. W.

    2017-12-01

    IBM has created a general purpose, data-agnostic solution that provides high performance, low data latency, high availability, scalability, and persistent access to the captured data, regardless of source or type. This capability is hosted on commercially available cloud environments and uses much faster, more efficient, reliable, and secure data transfer protocols than the more typically used FTP. The design incorporates completely redundant data paths at every level, including at the cloud data center level, in order to provide the highest assurance of data availability to the data consumers. IBM has been successful in building and testing a Proof of Concept instance on our IBM Cloud platform to receive and disseminate actual GOES-16 data as it is being downlinked. This solution leverages the inherent benefits of a cloud infrastructure configured and tuned for continuous, stable, high-speed data dissemination to data consumers worldwide at the downlink rate. It also is designed to ingest data from multiple simultaneous sources and disseminate data to multiple consumers. Nearly linear scalability is achieved by adding servers and storage.The IBM Proof of Concept system has been tested with our partners to achieve in excess of 5 Gigabits/second over public internet infrastructure. In tests with live GOES-16 data, the system routinely achieved 2.5 Gigabits/second pass-through to The Weather Company from the University of Wisconsin-Madison SSEC. Simulated data was also transferred from the Cooperative Institute for Climate and Satellites — North Carolina to The Weather Company, as well. The storage node allocated to our Proof of Concept system as tested was sized at 480 Terabytes of RAID protected disk as a worst case sizing to accommodate the data from four GOES-16 class satellites for 30 days in a circular buffer. This shows that an abundance of performance and capacity headroom exists in the IBM design that can be applied to additional missions.

  19. Linguistic analysis of communication in therapist-assisted internet-delivered cognitive behavior therapy for generalized anxiety disorder.

    Science.gov (United States)

    Dirkse, Dale; Hadjistavropoulos, Heather D; Hesser, Hugo; Barak, Azy

    2015-01-01

    Therapist-assisted Internet-delivered cognitive behavior therapy (ICBT) involves elements of expressive writing through secure messaging with a therapist. Expressive writing has been associated with psychological and physical health benefits in past research; furthermore, certain linguistic dimensions in expressive writing have been identified as particularly beneficial to health, such as less frequent use of negative emotion words and greater use of positive emotion words. No research, to date, has analyzed linguistic dimensions in client communication over the course of therapist-assisted ICBT for individuals with symptoms of generalized anxiety. This naturalistic study examined messages sent to therapists during the course of ICBT using linguistic analysis, and explored covariation of word use with symptom improvement. Data were obtained from patients with symptoms of generalized anxiety (N = 59) who completed 12 modules of therapist-assisted ICBT and rated symptoms of anxiety, depression, and panic at the beginning of each module. Linguistic analysis categorized text submitted to therapists into different word categories. Results found that patients' use of negative emotion, anxiety, causation, and insight words reduced over the course of treatment, while past tense words increased. Furthermore, negative emotion words significantly covaried with symptom ratings over the course of treatment. While causal statements cannot be made, findings improve our understanding of patient communication in ICBT and suggest that the further study of linguistic dimensions as psychological indicators and the potential utility of expressive writing strategies in therapist-assisted ICBT may be worthwhile.

  20. INMARSAT - The International Maritime Satellite Organization: Origins and structure

    Science.gov (United States)

    Doyle, S. E.

    1977-01-01

    The third session of the International Conference on the Establishment of an International Maritime Satellite System established the International Maritime Satellite Organization (INMARSAT) in 1976. Its main functions are to improve maritime communications via satellite, thereby facilitating more efficient emergency communications, ship management, and maritime public correspondence services. INMARSAT's aims are similar to those of the Intergovernmental Maritime Consultative Organization (IMCO), the main United Nations organization dealing with maritime affairs. The specific functions of INMARSAT have been established by an Intersessional Working Group (IWG) which met three times between general conference meetings. Initial investment shares for the creation of INMARSAT were shared by the United States (17%), the United Kingdom (12%), the U.S.S.R. (11%), Norway (9.50%), Japan (8.45%), Italy (4.37%), and France (3.50%).