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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Spread spectrum communications. Volume 1, 2 & 3

The design and operation of spread-spectrum (SS) communication systems are examined in an introductory text intended for graduate engineering students and practicing engineers. Chapters are devoted to an overview of SS systems, the historical origins of SS, basic concepts and system models, antijam communication systems, pseudonoise generators, coherent direct-sequence systems, noncoherent frequency-hopped systems, coherent and differentially coherent modulation techniques, pseudonoise acquisition and tracking in direct-sequence receivers, time and frequency synchronization of frequency-hopped receivers, low-probability-of-intercept communication, and multiple-access communication. Graphs, diagrams, and photographs are provided.

Simon, M. K.↗
NASA NTRS1977

Signal-to-noise ratio estimation in digital computer simulation of lowpass and bandpass systems with applications to analog and digital communications, volume 3

Techniques are developed to estimate power gain, delay, signal-to-noise ratio, and mean square error in digital computer simulations of lowpass and bandpass systems. The techniques are applied to analog and digital communications. The signal-to-noise ratio estimates are shown to be maximum likelihood estimates in additive white Gaussian noise. The methods are seen to be especially useful for digital communication systems where the mapping from the signal-to-noise ratio to the error probability can be obtained. Simulation results show the techniques developed to be accurate and quite versatile in evaluating the performance of many systems through digital computer simulation.

Tranter, W. H.↗
NASA NTRS1988

ISAAC: Inflatable Satellite of an Antenna Array for Communications, volume 6

The results of a study to design an antenna array satellite using rigid inflatable structure (RIS) technology are presented. An inflatable satellite allows for a very large structure to be compacted for transportation in the Space Shuttle to the Space Station where it is assembled. The proposed structure resulting from this study is a communications satellite for two-way communications with many low-power stations on the ground. Total weight is 15,438 kilograms which is within the capabilities of the Space Shuttle. The satellite will have an equivalent aperture greater than 100 meters in diameter and will be operable in K and C band frequencies, with a total power requirement of 10,720 watts.

Lodgard, Deborah↗
NASA NTRS1991

The impact of cockpit automation on crew coordination and communication. Volume 1: Overview, LOFT evaluations, error severity, and questionnaire data

The purpose was to examine, jointly, cockpit automation and social processes. Automation was varied by the choice of two radically different versions of the DC-9 series aircraft, the traditional DC-9-30, and the glass cockpit derivative, the MD-88. Airline pilot volunteers flew a mission in the simulator for these aircraft. Results show that the performance differences between the crews of the two aircraft were generally small, but where there were differences, they favored the DC-9. There were no criteria on which the MD-88 crews performed better than the DC-9 crews. Furthermore, DC-9 crews rated their own workload as lower than did the MD-88 pilots. There were no significant differences between the two aircraft types with respect to the severity of errors committed during the Line-Oriented Flight Training (LOFT) flight. The attitude questionnaires provided some interesting insights, but failed to distinguish between DC-9 and MD-88 crews.

Wiener, Earl L.↗
NASA NTRS1981

Pacific Basin Communications Study, Volume 1

The Pacific Basin Communications Study describes and assesses extent telecommunications systems in the Pacific Islands region. The study examines user needs in terms of the development of social services and commercial activities. Alternative technological solutions to communications problems are proposed and described. Recommendations include the augmentation and improvement of existing systems allowing for increased communications capacity. Regional cooperation will be required to accommodate the specific, unique requirements of individual nations. Questions of financing, implementation, management, costs and benefits of a regional telecommunications system are discussed.

Young, E. L.↗
NASA NTRS1979

Concepts for 18/30 GHz satellite communication system, volume 1

Concepts for 18/30 GHz satellite communication systems are presented. Major terminal trunking as well as direct-to-user configurations were evaluated. Critical technologies in support of millimeter wave satellite communications were determined.

Jorasch, R.↗
NASA NTRS1979

TMS communications software. Volume 1: Computer interfaces

A prototype bus communications system, which is being used to support the Trend Monitoring System (TMS) as well as for evaluation of the bus concept is considered. Hardware and software interfaces to the MODCOMP and NOVA minicomputers are included. The system software required to drive the interfaces in each TMS computer is described. Documentation of other software for bus statistics monitoring and for transferring files across the bus is also included.

Brown, J. S.↗
NASA NTRS1979

TMS communications software. Volume 2: Bus interface unit

A data bus communication system to support the space shuttle's Trend Monitoring System (TMS) and to provide a basis for evaluation of the bus concept is described. Installation of the system included developing both hardware and software interfaces between the bus and the specific TMS computers and terminals. The software written for the microprocessor-based bus interface units is described. The software implements both the general bus communications protocol and also the specific interface protocols for the TMS computers and terminals.

Gregor, P. J.↗
NASA NTRS1979

TMS communications hardware. Volume 1: Computer interfaces

A prototpye coaxial cable bus communications system was designed to be used in the Trend Monitoring System (TMS) to connect intelligent graphics terminals (based around a Data General NOVA/3 computer) to a MODCOMP IV host minicomputer. The direct memory access (DMA) interfaces which were utilized for each of these computers are identified. It is shown that for the MODCOMP, an off-the-shell board was suitable, while for the NOVAs, custon interface circuitry was designed and implemented.

Brown, J. S.↗
NASA NTRS1974

Crew/computer communications study. Volume 2: Appendixes

The software routines developed during the crew/computer communications study are described to provide the user with an understanding of each routine, any restrictions in use, the required input data, and expected results after executing the routines. The combination of routines to generate a crew/computer communications application is also explained. The programmable keyboard and display used by the program is described, and an experiment scenario is provided to illustrate the relationship between the program frames when they are grouped into activity phases. Program descriptions and a user's guide are also presented. For Vol. 1, see N74-18843.

Johannes, J. D.↗
NASA NTRS1979

TMS communications hardware. Volume 2: Bus interface unit

A prototype coaxial cable bus communication system used in the Trend Monitoring System to interconnect intelligent graphics terminals to a host minicomputer is described. The terminals and host are connected to the bus through a microprocessor-based RF modem termed a Bus Interface Unit (BIU). The BIU hardware and the Carrier Sense Multiple Access Listen-While-Talk protocol used on the network are described.

Brown, J. S.↗
NASA NTRS1987

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

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.

Young, S. Lee↗
NASA NTRS1974

Crew/computer communications study. Volume 1: Final report

Techniques, methods, and system requirements are reported for an onboard computerized communications system that provides on-line computing capability during manned space exploration. Communications between man and computer take place by sequential execution of each discrete step of a procedure, by interactive progression through a tree-type structure to initiate tasks or by interactive optimization of a task requiring man to furnish a set of parameters. Effective communication between astronaut and computer utilizes structured vocabulary techniques and a word recognition system.

Johannes, J. D.↗