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At least 469 records · Page 26

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NASA NTRS1972

Very long baseline interferometry observations of radio emissions from geostationary satellites.

Review of the results of very long baseline interferometry (VLBI) observations of L-band emissions of the ATS-5 geostationary satellite, performed over a transcontinental baseline in 1970, as part of a more comprehensive program using radio stars as sources. Although the data were not sufficient to demonstrate fully the capability of the method for determining the orbital elements of a satellite and its inertial position, the analysis of the ATS observations show the presence of interference fringes related to the modulation waveform emitted by the satellite and to the various motions of the satellite. The measured VLBI time delays are in agreement with the geometry of the observations and with the instrumental delay, both determined independently.

Michelini, R. D.↗

NASA NTRS1972

Trends in NASA communication satellites.

Discussion of the potential applications of satellite communications technology in meeting the national needs in education, health care, culture, and data transfer techniques. Experiments with the NASA ATS 1, 3 and 5 spacecraft, which are conducted in an attempt to satisfy such needs, are reviewed. The future needs are also considered, covering the requirements of multiple region coverage, communications between regions, large numbers of ground terminals, multichannel capability and high quality TV pictures. The ATS F and CTS spacecraft are expected to be available in the near future to expand experiments in this field.

Sivo, J. N.↗

NASA NTRS1972

Millimeter wave space communications - Recent experimental results and present development programs.

Major results of millimeter wave propagation measurements conducted with the ATS-5 satellite are reviewed, and their impact on the design of operational millimeter wave communications systems is evaluated. Statistical results show attenuation probabilities in different localities at various intervals of observation in an attempt at correlation with precipitation conditions. Advanced millimeter wave propagation experiments currently under development for the ATS-F satellite are also discussed.

Ippolito, L. J.↗

NASA NTRS1973

Millimeter wave propagation measurements from an orbiting earth satellite.

Major results of the millimeter wave propagation measurements conducted with the ATS-5 satellite are reviewed. The impact of these results on millimeter wave communications systems design is outlined. Advanced millimeter wave flight experiments currently under development for the ATS-F satellite are also discussed, and their main characteristics are summarized.

Ippolito, L. J.↗

NASA NTRS1974

Millimeter wavelength propagation studies

The investigations conducted for the Millimeter Wavelength Propagation Studies during the period December, 1966, to June 1974 are reported. These efforts included the preparation for the ATS-5 Millimeter Wavelength Propagation Experiment and the subsequent data acquisition and data analysis. The emphasis of the OSU participation in this experiment was placed on the determination of reliability improvement resulting from the use of space diversity on a millimeter wavelength earth-space communication link. Related measurements included the determination of the correlation between radiometric temperature and attenuation along the earth-space propagation path. Along with this experimental effort a theoretical model was developed for the prediction of attenuation statistics on single and spatially separated earth space propagation paths. A High Resolution Radar/Radiometer System and Low Resolution Radar System were developed and implemented for the study of intense rain cells in preparation for the ATS-6 Millimeter Wavelength Propagation Experiment.

Hodge, D. B.↗

NASA NTRS1973

Vanguard/PLACE experiment system design and test plan

A system design and test plan are described for operational evaluation of the NASA-Goddard position location and aircraft communications equipment (PLACE), at C-band (4/6 GHz), using NASA's ship, the USNS Vanguard, and the ATS-3 and ATS-5 synchronous satellites. The sea test phase, extending from Mar. 29, 1973 to Apr. 15, 1973 has been successfully completed; the principal objectives of the experiment were achieved. Typical PLACE-computed, position-location data are shown for the Vanguard. Position location and voice-quality measurements were excellent; ship position was determined within 2 n mi; high-quality, 2-way voice transmissions resulted as determined from audience participation, intelligibility and articulation-index analysis. A C-band/L-band satellite trilateration experiment is discussed.

Taylor, R. E.↗

NASA NTRS1973

Satellites for the citizen

Applications Technology Satellite ATS-F scheduled for launch in 1974 will be the last of its type sponsored by NASA. In the years that these satellites have served the practical needs of prototype development programs for space technology, immense benefits have accrued to the general public in the fields of communications, navigation, meteorology, and a host of related areas. If the public is to continue to benefit from this extremely successful series of launchings, private enterprise will have to assume the cost of future ATS experiments when NASA withdraws from the field.

Metzger, E.↗

NASA NTRS1975

Plasma clouds and auroral arcs

Correlation techniques for magnetospheric observations of various types by instrumented spacecraft in synchronous orbit are discussed. Emphasis is placed on ideas for possible use in studies with GEOS satellite during the International Magnetospheric Study, and comparison of auroral and magnetospheric plasma features are considered. Correlation between ATS-5 particle detector measurements with ground based measurement and other spacecraft such as Explorer 45 is described. Observations from ATS-6 instrument are briefly mentioned.

Deforest, S.↗

NASA NTRS1974

Applications Technology Satellite 6 - Upgrading the life style of millions of people

The primary objective of the ATS-6 is to demonstrate the feasibility of operating a high-powered geosynchronous communications satellite capable of relaying color TV and other high-quality signals on multiple frequencies to relatively simple and inexpensive ground receivers. Other capabilities include providing a link between ships, aircraft, or other earth satellites (e.g., low-orbit meteorological satellites) and the ground. The ATS-6 flight-objective accomplishments and subsystem performance for its first 30 days in orbit are summarized. Success is predicted for most of the experiments carried.

Thole, J. M.↗

NASA NTRS1975

A relationship between synchronous altitude electron fluxes and the auroral electrojet

Simultaneous observations during four substorms are reported from the Lockheed auroral particle spectrometer on ATS 5 and the University of Alberta meridian magnetometer chain. During the four events studied there was a good correlation between the magnitude of the trapped electron fluxes in the energy range from 1.8 to 53 keV and the magnitude of the electrojet current as measured by a station in the magnetometer chain at a latitude close to that expected for the ATS conjugate point. A model electrojet is constructed based on the work of Coroniti and Kennel (1972) which gives a good absolute agreement between the two measured quantities. The results are consistent with the convection electric field's remaining approximately constant during a substantial portion of each of the substorms studied. The temporal variations of the electrojet were apparently controlled by conductivity changes in the ionosphere as determined by the precipitating auroral electrons.

Sharp, R. D.↗

NASA NTRS1975

Satellite broadcasting - Capabilities for public service

Satellite broadcast services to support health-care and educational transmissions must work with small, low-cost terminals in allocated radio-frequency bands. The ATS-6 spacecraft has successfully demonstrated such capability in the bands of non-technical users. It supports interactive television broadcasting to simple, low-cost terminals in a nationwide series of experiments in the delivery of health-care and educational services. ATS-6 achieves this capability with a very large antenna and moderate transmitter power. The coverage limitations inherent in this approach will be overcome by the joint U.S.-Canadian Communications Technology Satellite to be launched in December 1975. The CTS will demonstrate broadcast capability with new, high-power technology in a newly-allocated radio-frequency band. This will make it possible to use smaller antennas, greatly enlarging the area coverage available to the many nontechnical experimenters using CTS for their own needs. A practical application of these technologies is now in development for operational broadcasting services in Japan.

Marsten, R. B.↗

NASA NTRS1975

A relationship between synchronous-altitude electron fluxes and the auroral electrojet, appendix A

Simultaneous observations during four substorms are reported from the Lockheed auroral particle spectrometer on ATS-5 and the University of Alberta meridian magnetometer chain (Canada). During the four events studied, there was a good correlation between the magnitude of the trapped electron fluxes in the energy range from 1.8 to 53 keV and the magnitude of the electrojet current as measured by a station in the magnetometer chain at a latitude close to that expected for the ATS conjugate point. The Hall effect was studied and a model electrojet was constructed which gave a good absolute agreement between the two measured quantities. The results are consistent with the convection electric field remaining approximately constant during a substantial portion of each of the substorms studied. The temporal variations of the electrojet were apparently controlled by conductivity changes in the ionosphere as determined by the precipitating auroral electrons.

Sharp, R. D.↗

NASA NTRS1975

The Comsat 13 and 18 GHz propagation experiment

The ATS-6 Comsat Propagation Experiment, designed to gather statistical data on attenuation by rain and snow at 13 and 18 GHz, is discussed. Signals from unattended ground transmitters at 25 locations in the eastern U.S. operating at 18 GHz and 13 GHz were transmitted to ATS-6, where the transponder converted the carriers to frequencies around 4150 MHz. These signals were then transmitted to the Comsat large horn antenna/data acquisition and receiving facility at Bangor, Maine, where each carrier was calibrated and digitally recorded once per second. Attenuation statistics for 40 carriers have been plotted. The experiment was conducted from July 1974 to May 1975 with excellent performance of the transponder.

King, J. L.↗

NASA NTRS1976

Plasma injection at synchronous orbit and spatial and temporal auroral morphology

Analysis of ATS 5 particle spectrograms and simultaneous meridian-scanning photometer data obtained at the base of the ATS field line has revealed systematic relationships between temporal and spatial auroral morphology and particle-injection events. The details of these relationships depend on previous injection events, the local time of the observatory with respect to current-injection events, and the extent and magnitude of current injections. A persistent zone of weak aurora is related to steady plasma-sheet drizzle, and the equatorward edge of this aurora delineates field lines threading the inner edge of the plasma sheet. Auroras associated with injection events superimpose on this preexisting pattern, with the lowest latitude of new precipitation depending on local time. In general, plasma energization is not required between the equatorial plane and the ionosphere to account for observed auroral intensities. The data indicate occasional occurrence of enhanced loss-cone fluxes, suggesting low-altitude field-aligned acceleration. A summary figure shows how various characteristic auroral-precipitation regions are related to the shape, extent, and orientation of the substorm injection boundary and to the subsequent drift paths of injected plasma.

Eather, R. H.↗

NASA NTRS1975

Health education telecommunications experiment

The Health/Education Telecommunications Experiment (HET) was conducted jointly by NASA and HEW on NASA's ATS-6 communications satellite. This experiment actually consisted of six experiments testing health and education applications of a communication spacecraft producing a broadcast of color television directly from space to over 120 low-cost receivers located in remote rural areas throughout the U.S. (including Alaska). The experiments were conducted over the period from 2 July 1974 to 20 May 1975 and operated on an almost daily basis. The overall telecommunications system to support these experiments consisted of many elements: The ATS-6 spacecraft; five different types of earth stations consisting of 120 video receive terminals, 51 telephony tranceivers and eight video originating terminals of three different types. Actual performance of the equipment as measured in the field was shown to equal or exceed predicted values.

Whalen, A. A.↗

NASA NTRS1976

OSU participation in the CTS communications link characterization experiment

A four element self phased array was developed for propagation measurements utilizing the Communication Technology Satellite 11.7 GHz downlink. The parameters of interest in measurements were attenuation, amplitude scintillation, and angle of arrival variability. Simultaneous scintillation measurements were also conducted at 360 MHz, 2.075 GHz, and 30 GHz utilizing ATS-6. The unique movement of ATS-6 during 1976 permitted extensive measurement of scintillation characteristics as a function of path elevation angle.

Hodge, D. B.↗

NASA NTRS1976

A statistical study of Pc 1 magnetic pulsations at synchronous orbit

The statistical properties of Pc 1 magnetic pulsations at synchronous orbit are examined by using measurements obtained with the UCLA flux-gate magnetometer on board ATS 1. In 1967, 121 intervals of Pc 1 activity occurred. These events typically had amplitudes of 1-7 gamma and periods of 2-5 sec. Most events lasted less than 30 min and occurred in the afternoon sector. Pc 1 waves were more probable during the main phase of a geomagnetic storm, within 1 hour of a substorm expansion. While they do not have the signature of IPDP (intervals of pulsations of diminishing periods) events at ATS, simultaneous ground records show the occurrence of rising frequency tones characteristic of IPDP events in seven out of ten cases. The wave frequency ranged principally from 0.1 to 0.2 of the local proton gyrofrequency, similar to observations of electron cyclotron waves. The observed Pc 1 activity is consistent with the generation by cyclotron resonance of 30-keV protons in a 30/cu cm plasma.

Bossen, M.↗

NASA NTRS1977

Satellite communication for public services

Public service programs using NASA's ATS-6 and CTS satellites are discussed. Examples include the ATS-6 Health and Education Telecommunications experimental program and the use of CTS to enable students in one university to take courses presented at another distant university. Possible applications of satellite communication systems to several areas of public service are described, and economic and political obstacles hindering the implementation of these programs are considered. It is suggested that a federally sponsored program demonstrating the utility of satellites accomodating a large number of small terminals is needed to encourage commercial satellite operations.

Cooper, R. S.↗