SEARCH · Search NASA
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Key millimeter wave propagation experiments and analytical results were summarized. The experiments were performed with the Ats-5, Ats-6 and Comstar satellites, radars, radiometers and rain gage networks. Analytic models were developed for extrapolation of experimental results to frequencies, locations, and communications systems.
Several techniques are investigated for making short conical tips on wires (whiskers) used for contacting millimeter-wave Schottky diodes. One procedure, using a phosphoric and chromic acid etching solution (PCE), is found to give good results on 12 microns phosphor-bronze wires. Full cone angles of 60 degrees-80 degrees are consistently obtained, compared with the 15 degrees-20 degrees angles obtained with the widely used sodium hydroxide etch. Methods are also described for cleaning, increasing the tip diameter (i.e. blunting), gold plating, and testing the contact resistance of the whiskers. The effects of the whisker tip shape on the electrical resistance, inductance, and capacitance of the whiskers are studied, and examples given for typical sets of parameters.
An optical diplexer for injection of a local oscillator into a mixer, useful in the submillimeter and short millimeter range, is described. It has very low insertion loss for both the signal and local oscillator (LO) and high rejection of LO noise. The measured performance of a unit tested at 337 GHz indicates a loss of about 0.2 dB for both inputs and 20-dB noise rejection.
Real time control, data collection, and data reduction of an earth-satellite millimeter wave system are discussed. Experiment control and data processing requirements are considered with attention to signal data acquisition, weather data acquisition, support and control functions, task classifications, the fundamental data acquisition procedure, and the computer-experiment interface. The general analysis is applied to a description of the Communications Technology Satellite system and its hardware.
NASA is currently conducting a series of millimeter wave satellite system market studies to develop 30/20 GHz satellite system concepts that have commercial potential. Four contractual efforts were undertaken: two parallel and independent system studies and two parallel and independent market studies. The marketing efforts are focused on forecasting the total domestic demand for long haul telecommunications services for the 1980-2000 period. Work completed to date and reported in this paper include projections of: geographical distribution of traffic; traffic volume as a function of urban area size; and user identification and forecasted demand.
A millimeter-submillimeter transmitter and receiver system for propagation studies with an optically pumped laser as a source and a quasi-optical superheterodyne receiver is described. Topics are discussed in the areas of extended microwave techniques, quasi-optical devices and methods, radiometry, and measurements of importance to spectroscopy and propagation. Measurements obtained with operational systems are highlighted and their significance to physical questions and future system applications discussed.
The status of incoherent detectors and coherent receivers over the infrared wavelength range from one micrometer to one millimeter is described. General principles of infrared receivers are included, and photon detectors, bolometers, coherent receivers, and important supporting technologies are discussed, with emphasis on their suitability for low background astronomical applications. Broad recommendations are presented and specific opportunities are identified for development of improved devices.
Identification of technologies for millimeter satellite communication systems, and assessment of the relative risks of these technologies, were accomplished through subsystem modeling and link optimization for both point-to-point and broadcast applications. The results, in terms of annual cost per channel to the user from a commercial view point, are described.
The Five College Radio Astronomy Observatory system, located in western Massachusetts, is described. It is suggested that high sensitivity in the three-millimeter wavelength band facilitates detection and monitoring of a number of trace molecules in the earth's atmosphere as well as astonomical observation at radio wavelengths. Line formation and radiative transfer in the earth's atmosphere are discussed, and the receiver sensitivity is considered.
Results are reported for observations of a quiet region at the center of the sun with an interferometer operating at a wavelength of 8.33 mm and with an east-west baseline giving a maximum angular resolution of 28 arcsec. It is found that strong fluctuations occur over time scales of approximately 10 to 30 min and dominate the data at large hour angles, that smaller and more rapid fluctuations in both amplitude and phase are detected at all hour angles, and that the strong fluctuations are consistent with those that may be produced by the natural time variation of the fringe pattern during observation of a fixed source distribution. The weaker and more rapid fluctuations are tentatively attributed to antenna-tracking variations and the observation of features in a greatly extended source. The results are compared directly with those of two other interferometric studies of the quiet sun at millimeter wavelengths.
Methodology has been developed for identifying viable and appropriate technologies for future NASA millimeter wave research as based upon the technical requirements of potential space communication services. Applicability of the methodology has been verified through its use with two conceptual communications systems. The subsystem cost and weight models are the appropriate level of detail for this study. Application of the methodology to the detailed design of a satellite system would require further model refinement.
A computer accessible catalogue of submillimeter, millimeter, and microwave spectral lines in the frequency range between O and 3000 GHz (such as; wavelengths longer than 100 m) is discussed. The catalogue was used as a planning guide and as an aid in the identification and analysis of observed spectral lines. The information listed for each spectral line includes the frequency and its estimated error, the intensity, lower state energy, and quantum number assignment. The catalogue was constructed by using theoretical least squares fits of published spectral lines to accepted molecular models. The associated predictions and their estimated errors are based upon the resultant fitted parameters and their covariances.
Three millimeter-wavelength transitions of ClO were searched for in the stratospheric emission spectrum during May-August 1977 using aircraft-based instruments. The measurements indicate that if stratospheric ClO has a vertical distribution of the form predicted by present photochemical models, then the ClO volume mixing ratio at the profile peak did not exceed 10 to the -9th at the time and place of the measurements. The observed spectra suggest the presence of ClO in the stratosphere but do not provide a definitive detection.
A piecewise uniform rain rate distribution model is introduced as a quasi-physical model of real rain along earth-space millimeter wave propagation paths. It permits calculation of the total attenuation from specific attenuation in a simple fashion. The model predications are verified by comparison with direct attenuation measurements for several frequencies, elevation angles, and locations. Also, coupled with the Rice-Holmberg rain rate model, attenuation statistics are predicated from rainfall accumulation data.
Research and development needs for millimeter-wave space communication systems are presented. Assumed propagation fade statistics are investigated along with high data rate diversity link and storage. The development of reliable ferrite switches, and high performance receivers and transmitters is discussed, in addition to improved tolerance of dish and lens fabrication for the antennas. The typical cost for using a simplex voice channel via a high capacity 40/50 GHz satellite is presented.
Parametric tests were conducted with a 35 millimeter bore, angular contact ball bearing having a single outer land guided cage. Lubrication was achieved by flowing oil through axial grooves and radial holes machined in the inner ring of the bearing. Test conditions were a thrust load of 667 N (150 lb), shaft speeds from 48,000 to 72,000 rpm, and an oil inlet temperature of 394 K (250 F). Data from tests where the distribution of the total oil supplied to the inner ring was 50 percent for bearing lubrication and 50 percent for bearing inner ring cooling were compared with those where the distribution pattern was 25 percent lubrication and 75 percent cooling. Successful operation was experienced with both the 50-50 and 25-75 percent flow distribution patterns to 2.5 million DN. The 50-50 percent flow pattern provided the cooler bearing operation of the two inner ring lubricated bearings. The jet lubricated bearing had lower outer ring and higher inner ring temperatures than the inner ring lubricated bearings. Maximum power loss of 2.8 kW (3.7 hp) was experienced with the 25-75 percent flow distribution, and maximum percent cage slip of 7.0 occurred at 72,300 rpm with the 50-50 percent flow distribution.
A computer accessible catalogue of submillimeter, millimeter and microwave spectral lines in the frequency range between 0 and 3000 GHZ (i.e., wavelengths longer than 100 mu m) is presented which can be used a planning guide or as an aid in the identification and analysis of observed spectral lines. The information listed for each spectral line includes the frequency and its estimated error, the intensity, lower state energy, and quantum number assignment. The catalogue was constructed by using theoretical least squares fits of published spectral lines to accepted molecular models. The associated predictions and their estimated errors are based upon the resultant fitted parameters and their covariances. Future versions of this catalogue will add more atoms and molecules and update the present listings (133 species) as new data appear. The catalogue is available as a magnetic tape recorded in card images and as a set of microfiche records.
This literature survey was conducted to examine the field of millimeter wave remote sensing of the environment and collect all relevant observations made in the atmospheric windows near 90, 140, and 230 GHz of ocean, terrain, man-made features, and the atmosphere. Over 170 articles and reports were examined; bibliographic references are provided for all and abstracts are quoted when available. Selected highlights were extracted from the pertinent articles.