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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Ariane is less costly than the space shuttle

'Ariadne', the European rocket, was found to be less costly than the American space shuttle, judging by the price proposals sent to Intelsat for the orbiting of its three latest telecommunications satellites in the Intelsat 5 series. The 'Ariadne' is being offered by the ESA and CNES at a ceiling price of $20 million, while the shuttle is priced by NASA at $22.5 million under the same condition. Neither the U. S. nor ESA have endorsed these prices officially. They are being presented as estimates. The 'Ariadne' has a ceiling price, which can only be adjusted downwards, if need be. The launching prices of both of these spacecraft do not include the cost of adapting the Intelsat 5 satellites, designed for the Atlas Centaur rocket.

Langereux, P.↗
NASA NTRS1977

X-band antenna gain and system noise temperature of 64-meter deep space stations

A set of measured data on the X-band performance of the three 64-meter deep space stations was obtained for use in future mission telecommunication design and predictions. The test configuration and measurement procedure is described. A method of modelling attenuation due to the atmosphere is given. Radio source brightness temperature and flux density are reviewed.

Benjauthrit, B.↗
NASA NTRS1977

Prediction of attenuation of the 28 GHz COMSTAR beacon signal using radar and measured rain drop spectra

Disdrometer measurements and radar reflectivity measurements were injected into a computer program to estimate the path attenuation of the signal. Predicted attenuations when compared with the directly measured ones showed generally good correlation on a case by case basis and very good agreement statistically. The utility of using radar in conjunction with disdrometer measurements for predicting fade events and long term fade distributions associated with earth-satellite telecommunications is demonstrated.

Goldhirsh, J.↗
NASA NTRS1977

A forecast of broadcast satellite communications

This paper presents forecasts of likely changes in broadcast satellite technology, the technology of ground terminals, and the technology of terrestrial communications competitive with satellites. The impacts of these changes in technology are then assessed, using a cross-impact model of U.S. domestic telecommunications, to determine the consequences of various possible changes in communications satellite technology. These consequences are discussed in terms of various possible services, for households, businesses, and specialized customers, which might become economically viable as a result of improvements in satellite technology.

Martino, J. P.↗
NASA NTRS1978

A design for a 1984 Mars rover

A Mars rover is planned for the mid-1980's as a follow-up to the Viking program, and as a prelude to a return-to-earth mission of Martian samples in the late eighties or early nineties. An overall view of the rover's configuration is presented with a summary of basic design parameters. Six subsystems are outlined: computing, with a 10 to the 8th bit bubble memory; mobility, designed for a journey of 100 km in 2 earth years; science sample acquisition, including a soil auger and hard rock drill; power, supplied by an RTG and stored in batteries; telecommunication, with 50 K bit UHF transmission relayed through an orbiter; and visual imaging, employing two television cameras, each with an 800 x 800 pixel charge coupled device. Scientific research goals include information about Martian seismic characteristics, magnetic field, surface heat flow, chemical composition, geology along a transverse, and meteorology. Attention is given to the necessity of rover autonomy from earth commands.

Dobrotin, B. M.↗
NASA NTRS1978

System design of an ion drive spacecraft

As electric propulsion technology has improved and mission requirements have changed, a series of Ion Propulsion Module (IPM) design concepts have evolved. The most recent iteration occurred in the NASA-sponsored Halley Comet Rendezvous Mission (HCRM) study of ion drive. Spacecraft system design considerations introduced by the integration of such an IPM as the primary propulsion source are described with reference to the synthesis of the HCRM spacecraft and spacecraft design considerations for other interplanetary applications. IPM interactions with the system (especially telecommunications and science) are found to be manageable. The spacecraft design developed for the HCRM indicates the interface simplicity between the IPM and the spacecraft. Methods are shown for readily applying this IPM to a variety of planetary missions. Methods are also described for the IPM to provide up to 5 kW to the spacecraft for increasing the mission science return

Stuart, J.↗
NASA NTRS1978

Pioneer 10 and 11 mission support

Estimates of the Deep Space Network performance capability in tracking Pioneer 10 to the telecommunications limit and for Pioneer 11 Saturn encounter are discussed. Graphs of downlink performance estimates giving geocentric range, antenna elevation, and time are included.

Miller, R. B.↗
NASA NTRS1978

Composite oscillator systems for meeting user needs for time and frequency

Frequency standards are used in most navigation and telecommunications systems to provide a long term memory of either frequency, phase, or time epoch. From a systems point of view, the performance aspects of the frequency standard are weighed against other systems characteristics, such as overall performance, cost, size, and accessibility; a number of examples are very briefly reviewed. The theory of phase lock and frequency lock systems is outlined in sufficient detail that total oscillator system performance can be predicted from measurements on the individual components. As an example, details of the performance of a high spectral purity oscillator phase locked to a long term stable oscillator are given. Results for several systems, including the best system stability that can be obtained from present commercially available 5-MHz sources, are shown.

Stein, S. R.↗
NASA NTRS1979

Costas loop demodulation of suppressed carrier BPSK signals in the DSN environment: Experimental results obtained at TDL

Suppressed carrier binary phase-shift keyed (BPSK) signalling is currently being considered as a design alternative for future DSN telemetry in the multimegabit range. Carrier tracking of such signals is usually achieved by a Costas loop, as opposed to the ordinary phase lock loop. A Costas loop capable of demodulating BPSK signals with data rates up to 1 Msps was designed and constructed and its Doppler tracking performance with respect to a Block 3 receiver was tested at the Telecommunications Development Laboratory (TDL). The compatibility of suppressed carrier signalling with the current radiometric system, specifically Doppler tracking and ranging, was investigated. The experimental results obtained to-date with respect to Doppler tracking are presented.

Reasoner, R.↗
NASA NTRS1978

Onboard processing for future space-borne imaging systems

There is a strong rationale for increasing the rate of information return from imaging class experiments aboard both terrestrial and planetary spacecraft. Future imaging systems will be designed with increased spatial resolution, broader spectral range and more spectral channels (or higher spectral resolution). The data rate implied by these improved performance characteristics can be expected to grow more rapidly than the projected telecommunications capability. One solution to this dilemma is the use of improved onboard data processing. The use of onboard classification processing in a multispectral imager can result in orders of magnitude increase in information transfer for very specific types of imaging tasks. Several of these processing functions are included in the conceptual design of an Infrared Multispectral Imager which would map the spatial distribution of characteristic geologic features associated with deposits of economic minerals.

Wellman, J. B.↗
NASA NTRS1978

Emerging markets for satellite data communications in the public service

The paper discusses some of the current and potential markets for satellite data communications as projected by the Public Service Satellite Consortium (PSSC). Organizations in the public service sector are divided into three categories, depending on their expected benefits and organizational changes due to increased satellite telecommunications use: A - modest institutional adjustments are necessary and significant productivity gains are likely; B - institutional requirements picture is promising, but more information is needed to assess benefits and risk; and C - major institutional adjustments are needed, risks are high but possible benefits are high. These criteria are applied to the U.S. health care system, continuing education, equipment maintenance, libraries, environmental monitoring, and other potential markets. The potential revenues are seen to be significant, but what is needed is a cooperative effort by common carriers and major public service institutions to aggregate the market.

Potter, J. G.↗
NASA NTRS1979

Voyager high gain antenna calibration and pointing

A mathematical description of the data reduction technique used in analyzing Voyager calibration data is presented. To achieve the required telecommunication link performance, highly accurate pointing of the Voyager high gain antenna boresight relative to earth is necessary. To provide the optimum pointing, in-flight calibrations of the high gain antenna pointing mechanism are regularly made, and the design of the calibration and the antenna error models is delineated. It is shown that due to the use of wide angle sun sensors for celestial attitude control, the Voyager antenna error model differs from those of previous missions. Results of the in-flight calibrations and their implementation in improving the antenna pointing are also presented.

Jahanshahi, M. H.↗
NASA NTRS1979

Application of non-attenuating frequency radars for prediction of rain attenuation and space diversity performance

In order to establish transmitter power and receiver sensitivity levels at frequencies above 10 GHz, the designers of earth-satellite telecommunication systems are interested in cumulative rain fade statistics at variable path orientations, elevation angles, climatological regions, and frequencies. They are also interested in establishing optimum space diversity performance parameters. In this work are examined the many elements involved in the employment of single non-attenuating frequency radars for arriving at the desired information. The elements examined include radar techniques and requirements, phenomenological assumptions, path attenation formulations and procedures, as well as error budgeting and calibration analysis. Included are the pertinent results of previous investigators who have used radar for rain attenuation modeling. Suggestions are made for improving present methods.

Goldhirsh, J.↗
NASA NTRS1979

The 30/20 GHz fixed communications systems service demand assessment. Volume 2: Main report

A forecast of demand for telecommunications services through the year 2000 is presented with particular reference to demand for satellite communications. Estimates of demand are provided for voice, video, and data services and for various subcategories of these services. The results are converted to a common digital measure in terms of terabits per year and aggregated to obtain total demand projections.

Gamble, R. B.↗
NASA NTRS1980

An advanced domestic satellite communications system

An updated traffic projection for U.S. domestic satellite communications service covering a period of 15 years; mid-1980 to mid-1995 was prepared. This model takes into account expected technology advances and reductions in transmission costs, legislative and regulatory changes permitting increased competition, and rising energy costs which will encourage more extensive substitution of telecommunications for travel. The historical development and current status of satellite systems are discussed as well as the characteristics of follow-on systems. Orbital arc utilization, spacecraft configuration for single shuttle launch, Earth station configuration, and system costs are examined. Areas which require technology development include multiple beam frequency reuse antennas, on-board switching, intersatellite links, and ka-band operation. Packing and deployment schemes for enclosing the satellite within the shuttle orbiter bay must also be devised.

Source record↗
NASA NTRS1979

Time dissemination in the Hydro Quebec network

The ever increasing complexity of electrical networks combined with the increasing cost of power losses during a network failure has led public utilities to become equipped with more powerful and precise tools for pinpointing the causes of such a fault. Hydro Quebec has developed and is now using a time dissemination system which uses a modified IRIG B code transmitted on its own telecommunication network. The reasons for using such a system and the way it was carried out are discrete.

Missout, G.↗
NASA NTRS1980

A quantitative analysis of inter-island telephony traffic in the Pacific Basin Region (PBR)

As part of NASA's continuing assessment of future communication satellite requirements, a study was conducted to quantitatively scope current and future telecommunication traffic demand in the South Pacific Archipelagos. This demand was then converted to equivalent satellite transponder capacities. Only inter-island telephony traffic for the Pacific Basin Region was included. The results show that if all this traffic were carried by a satellite system, one-third of a satellite transponder would be needed to satisfy the base-year (1976-1977) requirement and about two-thirds of a satellite transponder would be needed to satisfy the forecasted 1985 requirement.

Evans, D. D.↗
NASA NTRS1979

The ion drive program - Comet rendezvous issues for SEPS developers

Preliminary steps have been taken in a joint high-priority project between NASA and the European Space Agency, whereby a Solar Electric Propulsion System (SEPS), using ion drive of a 25-30 kilowatt power level, will be utilized for the first time, as part of the Space Transportation System, in powering a probe to be deployed toward Halley's comet in 1985 and a separate spacecraft which will rendezvous with the Temple 2 comet in 1988 and study it for one year. Unlike ballistically-launched vehicles, an unprecedented long-term interaction between the SEPS, the primary source of power and attitude control, and the spacecraft, responsible for data handling (at a rate of 10-120 kilobits per second), and command and telecommunications to earth (requiring capabilities at both X- and S-band frequencies, for dual-frequency navigational tracking), is required, as mission phases alternate between powered flight and science data-taking. Different design sensitivities are presented graphically.

Atkins, K. L.↗