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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

An experimental 20/30 GHz communications satellite conceptual design employing multiple-beam paraboloid reflector antennas

An experimental 20/30 GHz communications satellite conceptual design is described which employs multiple-beam paraboloid reflector antennas coupled to a TDMA transponder. It is shown that the satellite employs solid state GaAs FET power amplifiers and low noise amplifiers while signal processing and switching takes place on-board the spacecraft. The proposed areas to be served by this satellite would be the continental U.S. plus Alaska, Hawaii, Puerto Rico, and the Virgin Islands, as well as southern Canada and Mexico City. Finally, attention is given to the earth stations which are designed to be low cost.

Goldman, A. M., Jr.↗
NASA NTRS2019

Flexible Modem Interface (FMI) in Space - Extending Standardized Commercial Satellite Communications Services to Space Users

Recent innovations are producing a multitude of advanced commercial satellite communications (COMSATCOM) systems that could deliver massive amounts of SATCOM capacity at a fraction of current cost while also offering reliability and availability that is critical to achieving mission success for orbiting assets. Recognizing the alignment of commercial capabilities with the National Aeronautics and Space Administration's (NASA) diverse mission requirements, the agency is proactively engaging industry to formulate strategies leading towards a NASA communications architecture that includes advanced commercial capabilities. To fully leverage the expanded space resources, NASA must also address the integration of commercial waveforms into its space terminals. In pursuit of similar goals, the United States Department of Defense (DoD) is leading the standardization of the flexible modem interface (FMI) to address service integration for their tactical terminals in pursuit of a DoD Wideband SATCOM Enterprise.This paper describes how NASA is adapting this FMI standard to work with the Space Telecommunications Radio System (STRS) software-defined radio (SDR) framework to address the challenging size, weight, and power resource requirements for terminals in space. A full adaptation would include waveform compatibility with modular baseband processing, frequency compatibility with a wideband front end, and radiated beam control with an electronically steerable antenna to enable multi-provider commercial service capability in a feasible package for space terminals. Security is also a key aspect to be addressed for this integration since data will flow through commercial networks, commercial service providers have their own security mechanisms, and space terminals must be able to securely load proprietary software and firmware needed to access the commercial networks on demand. Success of this effort means commercial partners will be able to allow network-compliant implementations to be hosted on STRS-compliant SDRs in space for reliable and capable network access.

COMSATCOM↗
NASA NTRS1979

Developing the next phase in NASA's satellite communications program

Since 1973, NASA has conducted hundreds of user experiments and demonstrations using the Applications Technology Satellites ATS-1, -3, and -6, and the Communications Technology Satellite CTS. Now, projections show that the commercial demand will continue to increase, soon exceeding the current technology's capacity. The next phase in NASA's satellite communication program include 30/20 GHz Ka-band technology, extending the current work in advanced multibeam antennas; a narrow-band system and technology study that could lead to mobile and transportable communication developments; and studies of future uses of technology in communications.

Dement, D. K.↗
NASA NTRS1980

A satellite communications system for electric utilities

This paper presents the results of a study into the feasibility of using satellite communications for a country-wide system of electric distribution system monitoring and control. The concept selected for study involves the use of a geostationary satellite with a large multi-beam antenna to provide a major part of the communications and control network between participating utilities and various elements of their power distribution networks, including customer loads. Electric utility communications requirements are projected through 1995 in order to size the required capacity of the system. Two basic systems are examined: a one-way system for load control, and a two-way system for distribution system monitoring and control, including customer meter reading. An operating protocol is proposed for each system. Preliminary cost estimates are identified element by element. Finally, expansion of the basic system to include a set of ancillary communications functions is briefly discussed.

Vaisnys, A.↗
NASA NTRS1978

Public service satellite communications

It is suggested that the high effective isotropic radiated power provided by high-power satellite transmitters and high-gain antennas could be used in conjunction with economical ground receivers to furnish public services in remote areas of the U.S. Applications to health care, education and public safety are mentioned. A system concept involving a communications satellite operating in the Ku-band (12-GHz down, 14-GHz up) and either 100/30 watt stationary earth terminals with 1-1.8 m antennas or mobile terminals with omnidirectional antennas is presented.

Wolff, E. A.↗
NASA NTRS1983

Requirements for a mobile communications satellite system. Volume 1: Executive summary

Three types of satellite-aided mobile communications are considered for users in areas not served by (terrestrial) cellular radio systems. In System 1, mobile units are provided a direct satellite link to a gateway station, which serves as the interface to the terrestrial toll network. In System 2, a terrestrial radio link similar to those in cellular systems connects the mobile unit to a translator station; each translator relays the traffic from mobile units in its vicinity, via satellite, to the regional gateway. It is not feasible for System 2 to provide ubiquitous coverage. Therefore, System 3 is introduced, in which the small percentage of users not within range of a translator are provided a direct satellite link as in System 1. While System 2 can operate with leased satellite capacity, Systems 1 and 3 require a dedicated satellite. A major portion of this study is concerned with the design of a satellite for System 1. A weight limit of 10,000 lbs, corresponding to the projected 1990 STS capability, is imposed on the design. Frequency re-use of the allocated spectrum, through multiple satellite beams, is employed to generate the specified system capacity. Both offset-fed and center-fed reflectors are considered. For an assumed 10-MHz allocation and a population of 350,000 subscribers, a two-satellite system is required. The reflector diameters corresponding to offset-fed and center-fed geometries are 46 m and 62 m, respectively. Thus, large-space-structure technology is inherent to the implementation of System 1. In addition to establishing the technical requirements for the three types of satellite systems, the monthly service charge needed to provide a specified return on invested capital is computed. A net present value analysis is used for this purpose.

Source record↗
NASA NTRS1983

Requirements for a mobile communications satellite system. Volume 2: Technical report

Three types of satellite aided mobile communications are considered for users in areas not served by (terrestrial) cellular radio systems. In system 1, mobile units are provided a direct satellite link to a gateway station, which serves as the interface to the terrestrial toll network. In system 2, a terrestrial radio link similar to those in cellular systems connects the mobile unit to a translator station; each translator relays the traffic from mobile units in its vicinity, via satellite, to the regional gateway. It is not feasible for system 2 to provide obiquitous coverage. Therefore, system 3 is introduced, in which the small percentage of users not within range of a translator are provided a direct satellite link as in system 1.

Horstein, M.↗
NASA NTRS1983

Ni-H2 batteries for communications satellites

Ni-H2 batteries are just now being put into service. All of the remaining INTELSAT V satellites (approximately 10), starting with the next to be launched in early 1983, will use Ni-H2 batteries. In addition, the next generation of INTELSAT VI satellites, and probably INTELSAT VII and VIII, will use Ni-H2 batteries. This means that international telecommunications satellites will use Ni-H2 batteries through the 1990's. It is projected that the lifetime of these batteries will be greater than 10 years at deep depth-of-discharge (DOD), and that the battery subsystem will no longer limit satellite lifetime or communications capability during eclipse periods. This paper discusses the advantages of the Ni-H2 battery, as compared with the Ni-Cd battery, for telecommunications satellites.

Dunlop, J. D.↗
NASA NTRS1992

Future communications satellite applications

The point of view of the research is made through the use of viewgraphs. It is suggested that future communications satellite applications will be made through switched point to point narrowband communications. Some characteristics of which are as follows: small/low cost terminals; single hop communications; voice compatible; full mesh networking; ISDN compatible; and possible limited use of full motion video. Some target applications are as follows: voice/data networks between plants and offices in a corporation; data base networking for commercial and science users; and cellular radio internodal voice/data networking.

Bagwell, James W.↗
NASA NTRS1978

Preliminary benefits study for a public service communications satellite system: Task order 2

The economic and social benefits to accrue from an operational public service communications satellite system are estimated for the following applications: teleradiology, emergency medical services, teleconferencing for both civilian and defense agencies, data transfer, remote cardiac monitoring, teleconsultation, continuing education for professionals, and severe storm warning. The potential impact of improved communication on the cost and quality of services are assessed for various agencies, professions, and industries.

Source record↗
NASA NTRS1972

Small-angle stability analysis of a linear control system for a high power communication satellite

A small angle stability analysis is presented for one particular configuration of a high power communication satellite having a linear control system. Both the central body and the solar array are treated as rigid bodies. The control system studied consists of three-axis control of the central body and one-axis control of the solar array rotation relative to the central body. The results yield preliminary indications of the relation of stability to satellite inertias and control gains.

Omalley, T. A.↗
NASA NTRS1979

An overview of the NASA satellite communications program

This overview sets the framework for five descriptive papers from NASA Field Centers where satellite communications research and development is being conducted. A review of events of 1973-78 in the Federal Government, in industry, and in professional organizations are shown to have contributed to the formulation of new policy supporting the establishment of renewed efforts within NASA toward improved use of the spectrum and orbit for communications. The work will focus on the development of 'frequency re-use' technology, including multi-beam antennas and on-board switching for future spacecraft. This paper treats the planning issues and the approaches taken toward forming a coherent program from the sustaining efforts of the recent past. Companion papers highlight the methods, the technology, and the activities that are assisting in the transition to a new program.

Dement, D. K.↗
NASA NTRS1981

The impact of pulsed RFI on the coded BER performance of the nonlinear satellite communication channel

An examination is conducted of the coded bit error rate (BER) performance of a satellite communication system in which binary phase-shift-keyed (BPSK) modulation is employed, pulsed CW or pulsed noise RFI is present, and the transponder contains a nonlinearity characterized by arbitrary AM/AM and AM/PM characteristics; the RFI pulse duration is further assumed to exceed that of the information symbol. Computed performance curves consider several hypothetical RFI scenarios in which either a hard limiter or an 8 dB clipper represent the transponder amplitude nonlinearity. Results demonstrate the potential seriousness of RFI duty cycles as low as 2 percent, and the fact that CW represents the most severe form of interference.

Weinberg, A.↗
NASA NTRS1983

The NASA satellite communication 20 x 20 matrix switches

The characteristics of two matrix switches designed for high capacity satellite communications systems are described. The switches provide routing between 20 input and 20 output ports at an IF frequency during TDMA operations. Switching speeds of 10 nsec are projected for dual gate GaAs FETs. The two designs differed in the coupling configurations, bandwidth (2.69-1.2 GHz), off-state isolation (-54 to -40 dB), switching speeds (16-37 nsec), and gain ripple (5.3-2.2 dB). Both designs achieved a 2 nsec reconfiguration rate. Further development is required to reduce the ripple effects and attain the potential 2 nsec switching speed offered by the GaAs FETs.

Saunders, A. L.↗