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At least 559 records · Page 31

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NASA NTRS1995

More About Beam-Steering Subsystem For Laser Communication

Two reports present additional information about developmental beam-steering subsystem of laser-communication system. Aspects of this subsystem described previously in "Beam-Steering Subsystem for Laser Communication" (NPO-19069) and "Digital Controller for Laser-Beam-Steering Subsystem" (NPO-19193). Reports reiterate basic principles of operation of beam-steering subsystem and of laser-communication system as whole. Also presents some of details of optical and mechanical design of prototype of subsystem, called Optical Communication Demonstrator.

Page, Norman A.↗

NASA NTRS1994

Dynamic Environment Communications Analysis Testbed (DECAT) and Its Applications to Dual Use Space Technology

The Communication System Simulation Laboratory (CSSL) at the National Aeronautics and Space Administration (NASA)/Johnson Space Center (JSC) provides a facility for analyzing simulating space communication systems. The CSSL has simulation tools that model NASA communication systems and the environment in which they operate. One of these tools is a radio frequency coverage analysis tool called the Dynamic Environment Communications Analysis Testbed (DECAT). This paper focuses on DECAT and its applications to the Space Station and Space Shuttle programs.

Adkins, Antha A.↗

NASA NTRS1994

Software-Implemented Fault Tolerance in Communications Systems

Software-implemented fault tolerance (SIFT) is used in many computer-based command, control, and communications (C(3)) systems to provide the nearly continuous availability that they require. In the communications subsystem of Space Station Alpha, SIFT algorithms are used to detect and recover from failures in the data and command link between the Station and its ground support. The paper presents a review of these algorithms and discusses how such techniques can be applied to similar systems found in applications such as manufacturing control, military communications, and programmable devices such as pacemakers. With support from the Tracking and Communication Division of NASA's Johnson Space Center, researchers at the University of Wyoming are developing a testbed for evaluating the effectiveness of these algorithms prior to their deployment. This testbed will be capable of simulating a variety of C(3) system failures and recording the response of the Space Station SIFT algorithms to these failures. The design of this testbed and the applicability of the approach in other environments is described.

Gantenbein, Rex E.↗

NASA NTRS1995

A Low Earth Orbit satellite marine communication system demonstration

An application of Low Earth Orbit (LEO) satellite communications technology was investigated during a joint Canadian/American scientific expedition to the north pole in the summer of 1994. The Canadian ice breaker involved, was equipped with a store-and-forward LEO satellite terminal which was linked to a ground station in St. John's, Newfoundland, via the near-polar-orbiting satellite, HealthSat-l. The objective was to evaluate the performance of such a system while providing an alternate means of communications in the far north. The system performed well, given its inherent limitations. All 151 attempts to send data files to the ship were successful. Only two (2) of the 35 attempts to send files from the ship were unsuccessful. The files ranged in size from 0.1 to 60 Kbytes. In the high arctic, above 80 deg north, this system often provided the only practical means of data communications. This experiment demonstrated the potential of such a system for not-real-time communications with remote and/or mobile stations, and highlighted the many issues involved. This paper describes the project objectives, system configuration and experimental procedure used, related technical issues, trial results, future work, and conclusions.

Elms, T. Keith↗

NASA NTRS1995

Satellite communications provisions on NASA Ames instrumented aircraft platforms for Earth science research/applications

Earth science activities at NASA Ames are research in atmospheric and ecosystem science, development of remote sensing and in situ sampling instruments, and their integration into scientific research platform aircraft. The use of satellite communications can greatly extend the capability of these agency research platform aircraft. Current projects and plans involve satellite links on the Perseus UAV and the ER-2 via TDRSS and a proposed experiment on the NASA Advanced Communications Technology Satellite. Provisions for data links on the Perseus research platform, via TDRSS S-band multiple access service, have been developed and are being tested. Test flights at Dryden are planned to demonstrate successful end-to-end data transfer. A Unisys Corp. airborne satcom STARLink system is being integrated into an Ames ER-2 aircraft. This equipment will support multiple data rates up to 43 Mb/s each via the TDRS S Ku-band single access service. The first flight mission for this high-rate link is planned for August 1995. Ames and JPL have proposed an ACTS experiment to use real-time satellite communications to improve wildfire research campaigns. Researchers and fire management teams making use of instrumented aircraft platforms at a prescribed burn site will be able to communicate with experts at Ames, the U.S. Forest Service, and emergency response agencies.

Shameson, L.↗

NASA NTRS1996

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

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.

Coney, T. A.↗

NASA NTRS1998

Communication by Fire (and Smoke) Signals in the Kingdom of Judah

This paper examines the use of ancient fire and smoke signals for communication in the Kingdom of Judah. Historical and biblical references are cited that discuss this communication system. The current physical and political landscape of Israel precludes testing of hypotheses using traditional techniques. The use of a GIS is enlisted to overcome these obstacles and predict line-of-sight patterns that are conducive for a fire signal communication system. Final demonstration of this predictive model will incorporate state-of-the-art technology and in-field data acquisition to provide the sufficient accuracy that is required for proof-of-concept. This research will provide insight into the technical capability of the ancient Israelites for communication across a mountainous, desert environment.

Borowski, Oded↗

NASA NTRS1999

Advanced Communications Technology Satellite (ACTS) Fade Compensation Protocol Impact on Very Small-Aperture Terminal Bit Error Rate Performance

The Advanced Communications Technology Satellite (ACTS) communications system operates at Ka band. ACTS uses an adaptive rain fade compensation protocol to reduce the impact of signal attenuation resulting from propagation effects. The purpose of this paper is to present the results of an analysis characterizing the improvement in VSAT performance provided by this protocol. The metric for performance is VSAT bit error rate (BER) availability. The acceptable availability defined by communication system design specifications is 99.5% for a BER of 5E-7 or better. VSAT BER availabilities with and without rain fade compensation are presented. A comparison shows the improvement in BER availability realized with rain fade compensation. Results are presented for an eight-month period and for 24 months spread over a three-year period. The two time periods represent two different configurations of the fade compensation protocol. Index Terms-Adaptive coding, attenuation, propagation, rain, satellite communication, satellites.

Cox, Christina B.↗

NASA NTRS1999

Current Trend Towards Using Soft Computing Approaches to Phase Synchronization in Communication Systems

This paper surveys recent advances in communications that utilize soft computing approaches to phase synchronization. Soft computing, as opposed to hard computing, is a collection of complementary methodologies that act in producing the most desirable control, decision, or estimation strategies. Recently, the communications area has explored the use of the principal constituents of soft computing, namely, fuzzy logic, neural networks, and genetic algorithms, for modeling, control, and most recently for the estimation of phase in phase-coherent communications. If the receiver in a digital communications system is phase-coherent, as is often the case, phase synchronization is required. Synchronization thus requires estimation and/or control at the receiver of an unknown or random phase offset.

Drake, Jeffrey T.↗

NASA NTRS1998

Extended Range Communications Support for the X-33

Communications support for the X-33 requires addressing several interesting challenges to meet program and range safety requirements. In addition, the heavily cost driven program has provided concessions to the communications support to reduce the cost of networking the extended range. Cost trade-offs showed that by lowering the telemetry data rate from 2 Megabits per second to 1440 Megabits per second that significant cost avoidance could be realized. Also, by adopting standard telecommunications data rate for the uplink data stream, an efficient and integrated solution for the extended range communications could be supported. Meeting the program requirements as well as range safety requirements for this effort are critical to the success of the program. This paper describes some of the important requirements driving the design of the extended range communications support and the design of the system to meet those requirements.

Eslinger, Brian↗

NASA NTRS2000

Lessons from Communicating Space Science Over the Web

The Science Directorate at NASA's Marshall Space Flight Center uses the web in an aggressive manner to expand communications beyond the traditional "public affairs" or "media relations" routines. The key to success has been developing a balanced process that A) involves laboratory personnel and the NASA center community through a weekly Science Communications Roundtable, B) vests ownership and development of the product (i.e., the story) in the scientist a writer resident in the laboratory, and C) seeks taps the talents of the outside communications community through the Research/Roadmap Communications activity. The process is flexible and responsive, allowing Science@NASA to provide daily coverage for events, such as two materials science missions managed by NASA/Marshall. In addition to developing materials for the web, Science@NASA has conducted extensive research to determine what subjects people seek on the web, and the best methods to position stories so they will be found and read.

Dooling, David, Jr.↗

NASA NTRS1999

Face to Face Communications in Space

It has been reported that human face-to-face communications in space are compromised by facial edema, variations in the orientations of speakers and listeners, and background noises that are encountered in the shuttle and in space stations. To date, nearly all reports have been anecdotal or subjective, in the form of post-flight interviews or questionnaires; objective and quantitative data are generally lacking. Although it is acknowledged that efficient face-to-face communications are essential for astronauts to work safely and effectively, specific ways in which the space environment interferes with non-linguistic communication cues are poorly documented. Because we have only a partial understanding of how non-linguistic communication cues may change with mission duration, it is critically important to obtain objective data, and to evaluate these cues under well-controlled experimental conditions.

Cohen, Malcolm M.↗

NASA NTRS2000

Aviation Weather Information Communications Study (AWIN)

This two part study examines the communication requirements to provide weather information in the cockpit as well as public and private communication systems available to address the requirements. Ongoing research projects combined with user needs for weather related information are used to identify and describe potential weather products that address decision support in three time frames: Far-Term Strategic, Near-Term Strategic and Tactical. Data requirements of these future products are identified and quantified. Communications systems and technologies available in the public as well as private sector are analyzed to identify potential solutions. Recommendations for further research identify cost, performance, and safety benefits to justify the investment. The study concludes that not all weather information has the same level of urgency to safety-of-flight and some information is more critical to one category of flight than another. Specific weather products need to be matched with communication systems with appropriate levels of reliability to support the criticality of the information. Available bandwidth for highly critical information should be preserved and dedicated to safety. Meanwhile, systems designed for in-flight-entertainment and other passenger/crew services could be used to support less critical information that is used only for planning and economic decision support.

Ball, J. W.↗

NASA NTRS2000

Renewable Energy SCADA/Training Using NASA's Advanced Technology Communication Satellite

The lack of electrical energy in the rural communities of developing countries is well known, as is the economic unfeasibility of providing much needed energy to these regions via electric grids. Renewable energy (RE) can provide an economic advantage over conventional forms in meeting some of these energy needs. The use of a Supervisory Control and Data Acquisition (SCADA) arrangement via satellite could enable experts at remote locations to provide technical assistance to local trainees while they acquire a measure of proficiency with a newly installed RE system through hands-on training programs using the same communications link. Upon full mastery of the technologies, indigenous personnel could also employ similar SCADA arrangements to remotely monitor and control their constellation of RE systems. Two separate ACTS technology verification experiments (TVEs) have demonstrated that the portability of the Ultra Small Aperture Terminal (USAT) and the versatility of NASA's Advanced Communications Technology Satellite (ACTS), as well as the advantages of Ka band satellites, can be invaluable in providing energy training via distance education (DE), and for implementing renewable energy system SCADA. What has not been tested is the capabilities of these technologies for a simultaneous implementation of renewable energy DE and SCADA. Such concurrent implementations will be useful for preparing trainees in developing countries for their eventual SCADA operations. The project described in this correspondence is the first effort, to our knowledge, in this specific TVE. The setup for this experiment consists of a one-Watt USAT located at Florida Solar Energy Center (FSEC) connected to two satellite modems tuned to different frequencies to establish two duplex ACTS Ka-band communication channels. A short training program on operation and maintenance of the system will be delivered while simultaneously monitoring and controlling the hybrid using the same satellite communications link. The trainees will include faculty and students from Savannah State University, and staff from FSEC. An interactive internet link will be used to allow faculty from the University of West Indies to participate in the training session.

Kalu, A.↗

NASA NTRS2000

Mars Communication Protocols

Over the next decade, international plans and commitments are underway to develop an infrastructure at Mars to support future exploration of the red planet. The purpose of this infrastructure is to provide reliable global communication and navigation coverage for on-approach, landed, roving, and in-flight assets at Mars. The claim is that this infrastructure will: 1) eliminate the need of these assets to carry Direct to Earth (DTE) communications equipment, 2) significantly increase data return and connectivity, 3) enable small mission exploration of Mars without DTE equipment, 4) provide precision navigation i.e., 10 to 100m position resolution, 5) supply timing reference accurate to 10ms. This paper in particular focuses on two CCSDS recommendations for that infrastructure: CCSDS Proximity-1 Space Link Protocol and CCSDS File Delivery Protocol (CFDP). A key aspect of Mars exploration will be the ability of future missions to interoperate. These protocols establish a framework for interoperability by providing standard communication, navigation, and timing services. In addition, these services include strategies to recover gracefully from communication interruptions and interference while ensuring backward compatibility with previous missions from previous phases of exploration.

Kazz, G. J.↗

NASA NTRS2001

Satellite Communications for Aeronautics Applications: Technology Development and Demonstration

The National Aeronautics and Space Administration (NASA) is performing research and development to improve the safety and increase the capacity of the National Airspace System (NAS). Improved communications, especially to and from the aircraft flight deck, has been identified as an essential enabling technology for future improvements to the air traffic management system and aviation safety. NASA's Glenn Research Center is engaged in research and development of satellite communications technologies for aeronautical applications. A mobile aero terminal has been developed for use with Ku band commercial communications satellites. This experimental terminal will be used in mobile ground and air-based tests and demonstrations during 2000-2004. This paper will describe the basic operational parameters of the Ku Band aero terminal, the communications architecture it is intended to demonstrate, and the key technology issues being addressed in the tests and demonstrations. The design of the Ku Band aero terminal and associated ground testbed, planned tests and demonstrations, and results to date will be presented.

Kerczewski, Robert J.↗

NASA NTRS2001

Communication System Architecture for Planetary Exploration

Future human missions to Mars will require effective communications supporting exploration activities and scientific field data collection. Constraints on cost, size, weight and power consumption for all communications equipment make optimization of these systems very important. These information and communication systems connect people and systems together into coherent teams performing the difficult and hazardous tasks inherent in planetary exploration. The communication network supporting vehicle telemetry data, mission operations, and scientific collaboration must have excellent reliability, and flexibility.

Braham, Stephen P.↗

NASA NTRS1996

Man-Machine Interaction Design and Analysis System (MIDAS): Memory Representation and Procedural Implications for Airborne Communication Modalities

The Man-Machine Interaction Design and Analysis System (MIDAS) has been under development for the past ten years through a joint US Army and NASA cooperative agreement. MIDAS represents multiple human operators and selected perceptual, cognitive, and physical functions of those operators as they interact with simulated systems. MIDAS has been used as an integrated predictive framework for the investigation of human/machine systems, particularly in situations with high demands on the operators. Specific examples include: nuclear power plant crew simulation, military helicopter flight crew response, and police force emergency dispatch. In recent applications to airborne systems development, MIDAS has demonstrated an ability to predict flight crew decision-making and procedural behavior when interacting with automated flight management systems and Air Traffic Control. In this paper we describe two enhancements to MIDAS. The first involves the addition of working memory in the form of an articulatory buffer for verbal communication protocols and a visuo-spatial buffer for communications via digital datalink. The second enhancement is a representation of multiple operators working as a team. This enhanced model was used to predict the performance of human flight crews and their level of compliance with commercial aviation communication procedures. We show how the data produced by MIDAS compares with flight crew performance data from full mission simulations. Finally, we discuss the use of these features to study communications issues connected with aircraft-based separation assurance.

Corker, Kevin M.↗