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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Future satellite systems - Market demand assessment

During 1979-80, a market study was performed regarding the future total demand for communications services, and satellite transmission service at the 4/6 GHz, 12/14 GHz, and 20/30 GHz frequencies. Included in the study were a variety of communications traffic characteristics as well as projections of the cost of C and Ku band satellite systems through the year 2000. In connection with the considered study, a total of 15 major study tasks and subtasks were undertaken and were all interrelated in various ways. The telecommunications service forecasts were concerned with a total of 21 data services, 5 voice services, and 5 video services. The traffic volumes within the U.S. for the three basic services were projected for three time periods. It is found that the fixed frequency allocation for domestic satellites combined with potential interference from adjacent satellites means a near term lack of orbital positions above the U.S.

Reiner, P. S.↗
NASA NTRS1993

Modem Handles Data At 160 Mb/s

Trellis-coded octal-phase-shift-keying modem transmits and receives continuous or bursted digital data for satellite applications. Helps satisfy increasing demands for communication of high-speed digital data from sources like high-performance computers and high-definition television transmitters, as well as multiplexed signals from slower signal sources. Increases maximum effective bit rate accommodated in standard 72-MHz-wide commercial satellite-transponder radio channel from 120 Mb/s to 160 Mb/s. Principal advantages: spectral efficiency and power efficiency.

Budinger, James M.↗
NASA NTRS1994

The advantages of cost plus award fee contracts

A Cost Plus Award Fee contract is the best procurement vehicle for the high-tech, one-of-a-kind, development projects that constitute most of NASA'S projects. The use of this type of contract requires more government and contractor effort than any other forms of contracts. An award fee contract is described as an arrangement whereby the government periodically awards a fee consistent with the cost, schedule and technical performance that is achieved by a contractor during a preset period with preset award fee pools. It's the only contracting method where both the government and contractor goals are closely linked. It also has a built-in mechanism to conveniently alter and emphasize program events in order to current external and internal situations. The award fee process also demands good communication between government and contractor participants.

Keathley, William C.↗
NASA NTRS1997

Using Superconducting Thin Films in Microwave Lines

High temperature superconductors(HTS) and microwaves devices form the ideal partnership. The application of superconductors in microwave devices, components and systems allows the reduction in size, power consumption and insertion loss. The surface resistance of high-Tc superconductors has been found to be two orders of magnitude lower than normal conducting copper materials. The reduction in size and power requirements, which together both lead to a reduction in system mass, coupled with reasonably accessible operating temperatures, suggest that HTS microwave components should find ready application in satellite communications systems. At present, multi- channeling communication networks demand filters with narrow bandwidth in order to allow the available RF frequency spectrum to be partitioned into small frequency bands, -and possible variation of dielectric constant from substrate to substrate is undesirable. Microwave multiplexers demand the fabrication of two identical filters in each channel. Thus, the filter with tuning function is preferable. Tunable filters are the critical component for phased array antennas in order to electronically steer the radiated beam. To fabricate a tunable filter that uses an electric field for operation, one would like a material that provides a large change on dielectric constant for a given electric field, yet has a relatively low tangent in order to minimize the insertion loss of the device. Ferroelectrics have been the materials of choice. Their large dielectric constant sufficiently increases the coupling between microwave resonators and its dependence on electric field provides timability. Development of technology promises to diminish tangent loss. The use of thin ferroelectric films sufficiently decreases insertion losses keeping considerable potential for applications. NASA Lewis Research Center is the one of the leading centers in investigation of superconductors/ferroelectric tunable components for microwave devices. A large number of possible microwave devices were fabricated and tested on the basis of thin film multilayer superconductor-ferroelectric structures. In major cases the systems with edge-coupling scheme were investigated. Dr. Genkin has recently focused on the new potentialities which implements the using of thin ferroelectric films in filters fabricated with end-coupled microstrip lines. Numerical modeling shows that these systems have large potential for application in tunable narrow- and wide-bandpass filters in the frequency range 10-20 GHz. The phase shifter with end-coupled resonant sections was fabricated and tested. Experimental results show large tunability, particular in low voltages. The possible optimization of this structure promises to improve the obtained result and to reach the low level of insertion losses.

Genkin, Varery↗
NASA NTRS2016

On the Performance of Adaptive Data Rate over Deep Space Ka-Bank Link: Case Study Using Kepler Data

Future missions envisioned for both human and robotic exploration demand increasing communication capacity through the use of Ka-band communications. The Ka-band channel, being more sensitive to weather impairments, presents a unique trade-offs between data storage, latency, data volume and reliability. While there are many possible techniques for optimizing Ka-band operations such as adaptive modulation and coding and site-diversity, this study focus exclusively on the use of adaptive data rate (ADR) to achieve significant improvement in the data volume-availability tradeoff over a wide range of link distances for near Earth and Mars exploration. Four years of Kepler Ka-band downlink symbol signal-to-noise (SNR) data reported by the Deep Space Network were utilized to characterize the Ka-band channel statistics at each site and conduct various what-if performance analysis for different link distances. We model a notional closed-loop adaptive data rate system in which an algorithm predicts the channel condition two-way light time (TWLT) into the future using symbol SNR reported in near-real time by the ground receiver and determines the best data rate to use. Fixed and adaptive margins were used to mitigate errors in channel prediction. The performance of this closed-loop adaptive data rate approach is quantified in terms of data volume and availability and compared to the actual mission configuration and a hypothetical, optimized single rate configuration assuming full a priori channel knowledge.

Gao, Jay L.↗
NASA NTRSDate not supplied

Efficient Mirrorlet Array Based Integral Field Spectrometer (IFS) for HWO

Habitable World Observatory (HWO) is a NASA strategic mission recommended by 2020 astronomical decadal survey. Integral field spectrometers play an important role to verify if the observed exoplanet is habitable. The traditional lenslet array based IFS has the advantage of simplicity and compactness. However, it does not use detector pixels efficiently in order to prevent wavelength crosstalk among adjacent spectra. The efficient lenslet/mirrorlet IFS combines the advantages from both lenslet based and imager slicer based IFSes—keeping lenslet IFS’s simplicity and compactness, and adding slicer IFS’s detector efficiency. This paper discusses the principle of efficient lenslet/mirrorlet IFS, design philosophy, and efficient spectral trace layout ideals. It uses HWO NIR IFS requirement as an example to provide an efficiency mirrorlet IFS optical design. The high detector efficiency not only reduces needed detector pixel numbers, but also reduces the high communication rate demanding for such a large multiple instrument mission.

Qian Gong↗
NASA NTRSDate not supplied

Efficient Mirrorlet Array Based Integral Field Spectrometer for HWO

Habitable World Observatory (HWO) is a NASA strategic mission recommended by 2020 astronomical decadal survey. Integral spectrometers play an important role to verify if the observed exoplanet is habitable. The traditional lenslet array based Integral Field Spectrometer (IFS) has the advantage of simplicity and compactness. However, it does not use detector pixels efficiently in order to prevent wavelength crosstalk among adjacent spectra. The efficient lenslet/mirrorlet IFS combines the advantages from both lenslet based and imager slicer based IFSes—keeping lenslet IFS’s simplicity and compactness, concurrently adding slicer IFS’s detector efficiency. This paper discusses the principle of efficient lenslet/mirrorlet IFS, design philosophy, and efficient spectral trace layout ideals. It uses HWO NIR IFS requirement as an example to provide an efficiency mirrorlet IFS optical design. The high detector efficiency not only reduces Needed detector pixel numbers, but also reduce the high communication rate demanding for much a large multiple instrument mission. The basic idea of the efficient lenslet/mirrorlet array IFS is to design a lenslet/mirrorlet array in such a way that the images from multiple mirrorlets are grouped and aligned as a spectrum from a single slit. Therefore, the number of detector rows used to prevent wavelength crosstalk is no longer needed. This paper is also going to address how to lay the traces on the detector and what is the difference from the traditional lenslet IFS. Our goal is to show that such an IFS is capable to lay all spectral traces onto a 2k x 2k detector array using HWO NIR requirement that has a higher spectral resolving power R = 70 and a large Field of View (FOV) of 96 λ/D.

Exoplanet↗
NASA NTRS1981

The Quad aperture /hoop/column/ antenna for advanced communications missions in the 1990's

The possibility of meeting increased demand on the communications satellite system by utilizing a single satellite placed in geosynchronous orbit for service to the U.S. using the 4-6 GHz band and the 12-14 GHz band is discussed. To meet continental U.S. coverage requirements, approximately 220 spot beams 100 miles in diameter must be used. An F/D of 2.0 will be used in order to eliminate coma distortion effects, meet the low off-axis scan requirement, and fulfill design tradeoffs. Improvement on the best case crossover level of -9 dB can be accomplished by using a co-boresighted multiple reflector system and interleaving the beams from each offset reflector antenna. Shown are the illumination surfaces and the corresponding feed arrays in the quad aperture design and the reflector/feed system configuration for simultaneous operation in the two bands.

Sikes, L. D.↗
NASA NTRS1995

Architecture of the TELEDESIC satellite system

There is a significant worldwide demand for broadband communications capacity. Teledesic plans to meet this demand using a constellation of 924 low-Earth orbit (LEO) satellites operating in Ka-band (30/20 GHz). The Teledesic network will provide 'fiber-like' service quality, including low transmission delay, high data rates, and low bit error rates, to fixed and mobile users around the world starting in 2001.

Sturza, Mark A.↗
NASA NTRS1988

A satellite system for land-mobile communications in Europe

There exists a great unsatisified demand for land mobile communications in Europe, particularly in sectors of business activity such as the road transport industry. This demand could best be satisfied by means of satellite-based private networks providing voice and data communications in a hub configuration. The potential market is estimated to encompass several hundred thousand road vehicles and the transmission capacity required would be several thousand channels. ESA is currently demonstrating the potential of satellite communications for this type of application, using a system called PRODAT. System studies are being performed with the aim of defining the architecture of a regional satellite system for Europe.

Bartholome, P.↗
NASA NTRSDate not supplied

Development of an Airspace Simulation and Modeling Tool for Enhanced Spectrum Management

The emergence of new aerial vehicles into the National Airspace System creates an increased demand for aeronautical communications to support aviation operations. However, the issue of spectrum scarcity remains an ever-present concern, and the growing demand cannot be supported using existing spectrum allocation strategies. As a result, a new spectrum management approach is required, and the National Aeronautics and Space Administration (NASA) is investigating advanced concepts to modernize the management and use of aviation spectrum by leveraging the latest advancements in wireless communications, big data and machine learning. This research proposes an autonomous spectrum allocation concept, which allocates communications resources, such as spectrum and power, based on the predicted communications and air traffic demands throughout the airspace, as opposed to the use of fixed allocations as is done today. This approach will result in improved spectrum utilization efficiency and enhanced airspace capacity. The autonomous spectrum allocation concept decomposes into three research areas: demand prediction, resource allocation, and use case evaluation. As part of the use case evaluation effort, a modeling and simulation capability is currently under development. This simulation capability includes the implementation of various features, including visualization of both live or virtually-generated airspace traffic, simulation scenario development, simulation management with data collection, and flight plan creation with corresponding trajectory generation. This modeling and simulation capability will continue to evolve as new and advanced airspace applications are introduced into existing and emerging operational environments.

Eric J. Knoblock↗
NASA NTRS1993

Odyssey personal communications satellite system

The spectacular growth of cellular telephone networks has proved the demand for personal communications. Large regions of the world are too sparsely populated to be economically served by terrestrial cellular communications. Since satellites are well suited to this application, TRW filed with the FCC on May 31, 1993 for the Odyssey construction permit. Odyssey will provide high quality wireless communication services worldwide from satellites. These services will include: voice, data, paging, and messaging. Odyssey will be an economical approach to providing communications. A constellation of 12 satellites will be orbited in three, 55 deg. inclined planes at an altitude of 10,354 km to provide continuous coverage of designated regions. Two satellites will be visible anywhere in the world at all times. This dual visibility leads to high line-of-sight elevation angles, minimizing obstructions by terrain, trees and buildings. Each satellite generates a multibeam antenna pattern that divides its coverage area into a set of contiguous cells. The communications system employs spread spectrum CDMA on both the uplinks and downlinks. This signaling method permits band sharing with other systems and applications. Signal processing is accomplished on the ground at the satellite's 'Gateway' stations. The 'bent pipe' transponders accommodates different regional standards, as well as signaling changes over time. The low power Odyssey handset will be cellular compatible. Multipath fade protection is provided in the handset.

Spitzer, Christopher J.↗
NASA NTRS1977

Developing satellite communications for public service: Prospects in four service areas

The Public Service Satellite Consortium evaluated prospects for satellite telecommunications in four areas of the public service: the U.S. health care system, elementary and secondary education, American libraries, and that sector of the public service which is concerned with the provision of continuing education to health professionals. Three important conclusions were reached. First, throughout the public service there are three recurring needs: improved access, cost containment, and maintenance of quality. Appropriate application of communication satellite systems could ameliorate each of these concerns. Second, there appears to be an enormous latent demand for data communication services throughout the public service. The potential demand in 1982 to support requirements in hospital administration, library services and other information-retrieval activities, equipment maintenance, and environmental monitoring may be in excess of $300 million a year. Third, administrative applications of data communication networks show particular promise, especially in rural areas.

Source record↗
NASA NTRS1995

Helicopter Human Factors

Even under optimal conditions, helicopter flight is a most demanding form of human-machine interaction, imposing continuous manual, visual, communications, and mental demands on pilots. It is made even more challenging by small margins for error created by the close proximity of terrain in NOE flight and missions flown at night and in low visibility. Although technology advances have satisfied some current and proposed requirements, hardware solutions alone are not sufficient to ensure acceptable system performance and pilot workload. However, human factors data needed to improve the design and use of helicopters lag behind advances in sensor, display, and control technology. Thus, it is difficult for designers to consider human capabilities and limitations when making design decisions. This results in costly accidents, design mistakes, unrealistic mission requirements, excessive training costs, and challenge human adaptability. NASA, in collaboration with DOD, industry, and academia, has initiated a program of research to develop scientific data bases and design principles to improve the pilot/vehicle interface, optimize training time and cost, and maintain pilot workload and system performance at an acceptable level. Work performed at Ames, and by other research laboratories, will be reviewed to summarize the most critical helicopter human factors problems and the results of research that has been performed to: (1) Quantify/model pilots use of visual cues for vehicle control; (2) Improve pilots' performance with helmet displays of thermal imagery and night vision goggles for situation awareness and vehicle control; (3) Model the processes by which pilots encode maps and compare them to the visual scene to develop perceptually and cognitively compatible electronic map formats; (4) Evaluate the use of spatially localized auditory displays for geographical orientation, target localization, radio frequency separation; (5) Develop and flight test control/display concepts; (6) Quantify, model, predict, and improve pilots, workload-management strategies; and (7) Design computer-game trainers to reduce training time and cost.

Hart, Sandra G.↗
NASA NTRS1993

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

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.

Ohmori, Shingo↗