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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Applications of Microwave Photonics in Radio Astronomy and Space Communication

An overview of narrow band vs wide band signals is given. Topics discussed included signal transmission, reference distribution and photonic antenna metrology. Examples of VLA, ALMA, ATA and DSN arrays are given. . Arrays of small antennas have become more cost-effective than large antennas for achieving large total aperture or gain, both for astronomy and for communication. It is concluded that emerging applications involving arrays of many antennas require low-cost optical communication of both wide bandwidth and narrow bandwidth; development of round-trip correction schemes enables timing precision; and free-space laser beams with microwave modulation allow structural metrology with approx 100 micrometer precision over distances of 200 meters.

microwave↗
NASA NTRS1993

Reduced cost alternatives to premise wiring using ATM and microcellular technologies

The cost of premises wiring keeps increasing due to personnel moves, new equipment, capacity upgrades etc. It would be desirable to have a wireless interface from the workstations to the fixed network, so as to minimize the wiring changes needed. New technologies such as microcellular personal communication systems are promising to bring down the cost of wireless communication. Another promising technology is Code Division Multiple Access (CDMA), which could dramatically increase the bandwidth available for wireless connections. In addition, Asynchronous Transfer Mode (ATM) technology is emerging as a technique for integrated management of voice, data, and video traffic on a single network. The focus of this investigation will be to assess the future utility of these new technologies for reducing the premise wiring cost at KSC. One of the issues to be studied is the cost comparison of 'old' versus 'new,' especially as time and technology progress. An additional issue for closer study is a feasible time-line for progress in technological capability.

Gejji, Raghvendra R.↗
NASA NTRS1980

A digitally implemented communications experiment utilizing the communications technology satellite, Hermes

Developments which will reduce the costs associated with the distribution of satellite services are considered with emphasis on digital communication link implementation. A digitally implemented communications experiment (DICE) which demonstrates the flexibility and efficiency of digital transmission of television video and audio, telephone voice, and high-bit-rate data is described. The utilization of the DICE system in a full duplex teleconferencing mode is addressed. Demonstration teleconferencing results obtained during the conduct of two sessions of the 7th AIAA Communication Satellite Systems Conference are discussed. Finally, the results of link characterization tests conducted to determine (1) relationships between the Hermes channel 1 EIRP and DICE model performance and (2) channel spacing criteria for acceptable multichannel operation, are presented.

Jackson, H. D.↗
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

On-Board Fiber-Optic Network Architectures for Radar and Avionics Signal Distribution

Continued progress in both civil and military avionics applications is overstressing the capabilities of existing radio-frequency (RF) communication networks based on coaxial cables on board modem aircrafts. Future avionics systems will require high-bandwidth on- board communication links that are lightweight, immune to electromagnetic interference, and highly reliable. Fiber optic communication technology can meet all these challenges in a cost-effective manner. Recently, digital fiber-optic communication systems, where a fiber-optic network acts like a local area network (LAN) for digital data communications, have become a topic of extensive research and development. Although a fiber-optic system can be designed to transport radio-frequency (RF) signals, the digital fiber-optic systems under development today are not capable of transporting microwave and millimeter-wave RF signals used in radar and avionics systems on board an aircraft. Recent advances in fiber optic technology, especially wavelength division multiplexing (WDM), has opened a number of possibilities for designing on-board fiber optic networks, including all-optical networks for radar and avionics RF signal distribution. In this paper, we investigate a number of different novel approaches for fiber-optic transmission of on-board VHF and UHF RF signals using commercial off-the-shelf (COTS) components. The relative merits and demerits of each architecture are discussed, and the suitability of each architecture for particular applications is pointed out. All-optical approaches show better performance than other traditional approaches in terms of signal-to-noise ratio, power consumption, and weight requirements.

Alam, Mohammad F.↗
NASA NTRS1996

A Cost Comparison of Alternative Approaches to Distance Education in Developing Countries

This paper presents a cost comparison of three approaches to two-way interactive distance learning systems for developing countries. Included are costs for distance learning hardware, terrestrial and satellite communication links, and designing instruction for two-way interactive courses. As part of this project, FSEC is developing a 30-hour course in photovoltaic system design that will be used in a variety of experiments using the Advanced Communications Technology Satellite (ACTS). A primary goal of the project is to develop an instructional design and delivery model that can be used for other education and training programs. Over two-thirds of the world photovoltaics market is in developing countries. One of the objectives of this NASA-sponsored project was to develop new and better energy education programs that take advantage of advances in telecommunications and computer technology. The combination of desktop video systems and the sharing of computer applications software is of special interest. Research is being performed to evaluate the effectiveness of some of these technologies as part of this project. The design of the distance learning origination and receive sites discussed in this paper were influenced by the educational community's growing interest in distance education. The following approach was used to develop comparative costs for delivering interactive distance education to developing countries: (1) Representative target locations for receive sites were chosen. The originating site was assumed to be Cocoa, Florida, where FSEC is located; (2) A range of course development costs were determined; (3) The cost of equipment for three alternative two-way interactive distance learning system configurations was determined or estimated. The types of system configurations ranged from a PC-based system that allows instructors to originate instruction from their office using desktop video and shared application software, to a high cost system that uses a electronic classroom; (4) A range of costs for both satellite and terrestrial communications was investigated; (5) The costs of equipment and operation of the alternative configurations for the origination and receive sites were determined; (6) A range of costs for several alternative delivery scenarios (i.e., a mix of live-interactive; asynchronous interactive;use of videotapes) was determined; and (7) A preferred delivery scenario, including cost estimate, was developed.

Ventre, Gerard G.↗
NASA NTRS1996

Capabilities of Printed Reflectarray Antennas

This article presents an advanced antenna technology, namely the printed reflectarray, that has the potential for providing an enhanced communication capability with relatively low cost, small size and small mass. It has applicaiton in the commercial and military arenas as well as in space exploration.

advanced↗
NASA NTRS1991

Use of low orbital satellite communications systems for humanitarian programs

Communication and information exchange play a decisive role in progress and social development. However, in many parts of the world the communication infrastructure is inadequate and the capacity for on-line exchange of information may not exist. This is true of underdeveloped countries, remote and relatively inaccessible regions, sites of natural disasters, and of all cases where the resources needed to create complex communication systems are limited. The creation of an inexpensive space communications system to service such areas is therefore a high priority task. In addition to a relatively low-cost space segment, an inexpensive space communications systems requires a large number of ground terminals, which must be relatively inexpensive, energy efficient (using power generated by storage batteries, or solar arrays, etc.), small in size, and must not require highly expert maintenance. The ground terminals must be portable, and readily deployable. Communications satellites in geostationary orbit at altitudes of about 36,000 km are very expensive and require complex and expensive ground stations and launch vehicles. Given current technology, it is categorically impossible to develop inexpensive satellite systems with portable ground terminals using such satellites. To solve the problem of developing an inexpensive satellite communications system that can operate with relatively small ground stations, including portable terminals, we propose to use a system with satellites in low Earth orbit, at an altitude of 900-1500 km. Because low orbital satellites are much closer to the Earth than geostationary ones and require vastly less energy expenditure by the satellite and ground terminals for transmission of messages, a system using them is relatively inexpensive. Such a system could use portable ground terminals no more complex than ordinary mobile police radios.

Vlasov, Vladimir N.↗
NASA NTRS2004

Autonomous and Autonomic Systems: A Paradigm for Future Space Exploration Missions

NASA increasingly will rely on autonomous systems concepts, not only in the mission control centers on the ground, but also on spacecraft and on rovers and other assets on extraterrestrial bodies. Automomy enables not only reduced operations costs, But also adaptable goal-driven functionality of mission systems. Space missions lacking autonomy will be unable to achieve the full range of advanced mission objectives, given that human control under dynamic environmental conditions will not be feasible due, in part, to the unavoidably high signal propagation latency and constrained data rates of mission communications links. While autonomy cost-effectively supports accomplishment of mission goals, autonomicity supports survivability of remote mission assets, especially when human tending is not feasible. Autonomic system properties (which ensure self-configuring, self-optimizing self-healing, and self-protecting behavior) conceptually may enable space missions of a higher order into any previously flown. Analysis of two NASA agent-based systems previously prototyped, and of a proposed future mission involving numerous cooperating spacecraft, illustrates how autonomous and autonomic system concepts may be brought to bear on future space missions.

Truszkowski, Walter F.↗
NASA NTRS1990

Establishing a communications-intensive network to resolve artificial intelligence issues within NASA's Space Station Freedom research centers community

MITRE Corporation's, A Review of Space Station Freedom Program Capabilities for the Development and Application of Advanced Automation, cites as a critical issue the following situation, extant at the NASA facilities visited in the course of preparing the review: The major issues noted with regard to design and research facilities deal with cooperative problem solving, technology transfer, and communication between these facilities. While the authors were visiting lab and test beds to collect information, personnel at many of these facilities were interested in any information they could collect on activities at other facilities. A formal means of gathering this information could not be identified by these personnel. While communication between some facilities was taking place or was planned, for technology transfer or coordination of schedules (e.g., for SADP demonstrations), poor communication between these facilities could lead to a lack of technical standards, duplication of effort, poorly defined interfaces, scheduling problems, and increased cost. Formal mechanisms by which effective communication and cooperative problem solving can take place, and information can be disseminated, must be defined. A solution is proposed for the communications aspects of the issues addressed above; and offered at the same time a solution which can prove effective in dealing with some of the problems being encountered with expertise being lost via retirement or defection to the private sector. The proffered recommendations are recognizably cost-effective and tap the rising sector of expert knowledge being produced by the American academic community.

Howard, E. Davis, III↗
NASA NTRS1990

ACTS Multibeam Communications Package - Technology for the 1990S

To maintain its competitive position in the 1990s, satellite communications must evolve to provide new services and to reduce the costs of supplying existing services. NASA's Advanced Communications Technology Satellite (ACTS) program is directed toward developing the technology base that will support this evolution. The ACTS communications payload is optimized for digital communications using a time-division multiple access format. Scanning spot-beam antennas provide high-performance on-demand service to the earth communication stations. On-board processing and switching allow full connectivity in a single-hop network architecture. ACTS employs Ka-band (30/20 GHz) links for communications traffic and includes techniques for mitigating rain fades. Scheduled to be launched by a Space Shuttle in 1992, ACTS will provide in-orbit technology verification and support experimental communications networks for up to four years.

Graebner, John C.↗
NASA NTRS1992

ACTS Multibeam Communications Package - Description and Performance Characterization

To maintain its competitive position in the 1990s, satellite communications must evolve to provide new services and to reduce the costs of supplying existing services. NASA's Advanced Communications Technology Satellite (ACTS) program is directed toward developing the technology base that will support this evolution. The ACTS communications payload is optimized for digital communications using a time-division multiple-access format. Scanning spot-beam antennas provide high-performance, on-demand service to communications earth stations. On-board processing and switching allow full connectivity in a single-hop network architecture. ACTS employs Ka-Band (30/20 GHz) links for communications traffic and includes techniques for mitigating rain fades. The prelaunch test program has verified that all critical payload performance requirements have been realized, including G/T, EIRP, beam coverage, AM/AM, AM/PM, and BER vs. E(b)/N(o). Scheduled to be launched by a Space Shuttle in 1993, ACTS will provide in-orbit technology verification and support experimental communications networks for up to four years.

Cashman, William F.↗
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 NTRS1986

Network design consideration of a satellite-based mobile communications system

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.

Yan, T.-Y.↗
NASA NTRSDate not supplied

Flight and Direct to Earth/Space Relay Communication System Architecture for GSFC CubeSat Missions

The CubeSat platform is finding increasing use in space science applications due to its low cost and comparative ease of launch. It is becoming a key scientific discovery tool in low Earth orbit (LEO) and beyond, including geosynchronous equatorial orbit (GEO), the Lagrange Points, Lunar missions, and more. The increasing complexity of these missions and their scientific goals must be supported by equal advancements in communications technology. Higher data rates and greater reliability are required every year. However, the reduced Size, Weight, and Power (SWaP) constraints of CubeSat platforms introduce unique challenges in the area of satellite communications. There is currently a lack of communication equipment tailored specifically to the CubeSat platform. This lack of standardized, tested equipment extends development time and reduces mission confidence. Furthermore, missions utilizing the CubeSat platform are often subject to more difficult design constraints. Antenna placement, size, and pointing are often subordinate to the requirements of the payload instruments and mission goals. Traditional link margin estimation techniques are insufficient in these cases, as they emphasize worst case scenarios. In reality the actual link parameters may vary widely even during a single pass. This presents new challenges in predicting communications performance and scheduling ground station contacts, but also new opportunities for improving efficiency. This paper presents the integration, testing, and validation process for a new software defined radio (SDR) designed for the CubeSat platform in conjunction with Vulcan Wireless, Inc. The SDR is planned for use on 5 upcoming CubeSat missions at NASAs Goddard Space Flight Center (GSFC) including a Geosynchronous Transfer Orbit (GTO) mission and it may also serve as a standard and well-tested option for future missions by enabling a standardized, rapid and low cost CubeSat communication system network integration process. Detailed simulations have been developed to estimate the communication performance of these missions, taking the unique antenna placements and attitude behavior of each satellite into account. These simulations allow a much more accurate analysis of the expected link margin, which varies considerably during each pass for the NASA Space Relay (SR) and Direct to Earth (DTE) network. The modelling procedures are outlined, and the results are used to predict communications performance of the missions.

Space Networks↗
NASA NTRS2013

Demonstration of Space Optical Transmitter Development for Multiple High Frequency Bands

As the demand for multiple radio frequency carrier bands continues to grow in space communication systems, the design of a cost-effective compact optical transmitter that is capable of transmitting selective multiple RF bands is of great interest, particularly for NASA Space Communications Network Programs. This paper presents experimental results that demonstrate the feasibility of a concept based on an optical wavelength division multiplexing (WDM) technique that enables multiple microwave bands with different modulation formats and bandwidths to be combined and transmitted all in one unit, resulting in many benefits to space communication systems including reduced size, weight and complexity with corresponding savings in cost. Experimental results will be presented including the individual received RF signal power spectra for the L, C, X, Ku, Ka, and Q frequency bands, and measurements of the phase noise associated with each RF frequency. Also to be presented is a swept RF frequency power spectrum showing simultaneous multiple RF frequency bands transmission. The RF frequency bands in this experiment are among those most commonly used in NASA space environment communications.

Nguyen, Hung↗