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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 1,315 records · Page 73

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NASA NTRS1977

Transient response measurements on a satellite system

A set of instruments designed to detect the occurance of electrical breakdown was flown on a synchronous-orbit satellite. The LeRC sensors were installed on cables inside the vehicle. Accordingly, they respond to signals coupled into the satellite wiring system. The SRI sensors were located on the exterior of the vehicle and detected the RF noise pulses associated with surface breakdowns. The results of the earlier SRI program are being used to design and develop a set of intrumentation suitable for inclusion as a general piggy-back package for the detection of the onset of satellite charging and breakdowns on synchronous orbit satellites.

Nanevicz, J. E.↗

NASA NTRS1977

An introduction to orbit dynamics and its application to satellite-based earth monitoring systems

The long term behavior of satellites is studied at a level of complexity suitable for the initial planning phases of earth monitoring missions. First-order perturbation theory is used to describe in detail the basic orbit dynamics of satellite motion around the earth and relative to the sun. Surface coverage capabilities of satellite orbits are examined. Several examples of simulated observation and monitoring missions are given to illustrate representative applications of the theory. The examples stress the need for devising ways of maximizing total mission output in order to make the best possible use of the resultant data base as input to those large-scale, long-term earth monitoring activities which can best justify the use of satellite systems.

Brooks, D. R.↗

NASA NTRS1977

Solar power satellite system definition study. Part 2, volume 5: Space operations (construction and transportation)

Construction and transportation systems and operations are described for the following combinations: (1) silicon photovoltaic CR=1 satellite constructed primarily in low earth orbit (LEO); (2) silicon photovoltaic CR=1 satellite constructed in geosynchronous earth orbit (GEO); (3) Rankine thermal engine satellite constructed primarily in LEO; and (4) Rankine thermal engine satellite constructed in GEO.

Miller, K.↗

NASA NTRS1978

Assessment of needs for satellite tracking of birds and suggestions for expediting a program

Equipment development and testing, animal-instrument interphase or attachment methods, and the evaluation of various feasibility-tracking experiments with raptors are described as well as suggestions for expediting a future program. Results of animal-instrument interphases work indicate that large free-flying birds can be successfully instrumented with radio packages comparable in weight to satellite-transmitter packages. The 401 MHz frequency proved satisfactory for a combination of satellite and ground tracking of migrating birds. Tests run for nearly a year with the Nimbus 6 satellite and a miniaturized, one-watt prototype RAMS transmitter produced encouraging results in regard to location accuracy, frequency of contact with satellite and use of whip antennas. A future program is recommended with priority given to development of six operational transmitters for feasibility experiments.

Craighead, F. C., Jr.↗

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 NTRS1977

The 1977 WARC on broadcasting satellites - Spectrum management aspects and implications

Broadcasting satellites are allocated as a primary service in the band 11.7-12.2 GHz (11.7-12.5 GHz in Europe, Africa, and the USSR), but the band is also allocated on a primary basis (equal sharing) to other services - fixed, mobile, broadcasting, and fixed satellite. Presented with these difficult sharing situations, delegates from over 100 countries met at an ITU World Administrative Radio Conference in 1977 to develop a plan for broadcasting satellites. Many nations wanted a plan that would assign to them now, reserved orbital locations and channel asignments for their future use. Other countries wanted a plan adopted now for future broadcasting satellites which assigned specific channels to specific areas on the ground so that they could use the remaining frequencies to provide terrestrial service right away. This paper describes the 'Plan' developed at the conference and points out how the principles of spectrum management were employed. It also discusses the implications for future international management of the spectrum growing out of this meeting.

Gould, R. G.↗

NASA NTRS1977

Multilaterating the GEOS-3 satellite

It is demonstrated by means of rigorous simulations with an operational software system that multilateration of the GEOS-3 satellite is possible. This operation, i.e., the processing of simultaneous range measurements from the satellite to a real world constellation of stations using strictly geometric reduction of the observables, will result in the determination of the interstation coordinates to accuracies approaching those of the data measurements obtained at the stations. The satellite-to-satellite link between the GEOS-3 and ATS-6 can be used to further enhance the station covariance matrix.

Escobal, P. R.↗

NASA NTRS1977

Advanced spacecraft tracking techniques using the Tracking and Data Relay Satellite System /TDRSS/

The TDRSS will consist initially of two geosynchronous satellites and a common ground station at White Sands, New Mexico. According to current schedules, operations are to begin in November 1980. The overall TDRSS will provide high and low bit-rate telemetry, commands, and satellite-to-satellite tracking services. Each Tracking and Data Relay Satellite (TDRS) will have four antenna systems for NASA use. The common ground station at White Sands will have three 18-meter K-band antennas. The tracking equipment at the ground station is required to meet the following specifications: (1) 0.1-radian root-mean-square (rms) phase noise on nondestruct Doppler measurements; (2) 10-nanosecond rms range noise; (3) 50-nanosecond maximum systematic range error. Attention is given to two-way range and Doppler measurements, the bilateration tracking of TDRS, and an experiment using differenced one-way Doppler measurements.

Teles, J.↗

NASA NTRS1978

The calculated and observed ionospheric properties during Atmospheric Explorer-C satellite crossings over Millstone Hill

Results are presented for calculated and observed incoherent scatter radar data on ionospheric and atmospheric properties during the crossings of the Atmospheric Explorer-C satellite over the Millstone Hill, Massachusetts incoherent scatter radar station. The incoherent scatter radar measured electron density vertical profiles and electron and ion temperatures. These values yielded the exospheric temperature and the vertical distribution of neutral gas temperature. The satellite measured electron and ion temperatures and densities, neutral gas composition, and photoelectron spectra. Measurements were also made of solar UV and EUV fluxes, the vertical profile of the NO number density, and the vertical profile of the 6300 A airglow-volume emission rate. The results are compared to those of a time-dependent coupled model of the ionospheric E- and F-regions. Good agreement is found between satellite results, incoherent scatter radar measurements, and model calculations. Along the orbital path satellite measurements show significant latitudinal gradients in the measured properties.

Roble, R. G.↗

NASA NTRS1978

Mutual phenomena of Saturn's satellites in 1979-1980

Using two sets of orbital elements and the radii of the Saturnian satellites 1 (Mimas) through 7 (Hyperion), we find that from October 1979 until August 1980 nearly 300 mutual eclipses and occultations involving these bodies will occur. To allow for the expected errors in the satellite ephemerides, we repeat these calculations in order to obtain the additional events that occur when all satellite radii (save Titan's) are increased by 1000 km. A third listing predicts eclipses of satellites by (the shadow of) the ring. Photometric observations of a large number of these events will add much precise information to our knowledge of the Saturnian system at a critical time.

Aksnes, K.↗

NASA NTRS1978

The Earth Radiation Budget Satellite System

The scientific objectives of an Earth Radiation Budget Satellite System (ERBSS) are discussed along with the associated data analysis methods, mission analysis, and the instrument systems. High resolution data on the scale of about 250 km over the entire globe are essential to gain insight into such features as the development of sea-surface temperature anomalies, radiation effects of ice and snow cover on the atmospheric circulation, albedo variation in the desert-vegetation boundaries, and major long-period circulation phenomena. The ERBSS experiment is also viewed as a precursor of an operational satellite system for monitoring the earth's radiation budget. Various numbers of satellites and orbit inclinations have been analyzed to define the satellite combination which provides sufficient coverage of the earth for spatial and temporal radiation sampling.

Woerner, C. V.↗

NASA NTRS1978

Meteorological satellites in support of weather modification

During the past several years, many weather modification programs have been incorporating meteorological satellite data into both the operations and the analysis phase of these projects. This has occurred because of the advancement of the satellite as a mesoscale measurement platform, both temporally and spatially, and as the availability of high quality data has increased. This paper surveys the applications of meteorological satellite data to both summer and winter weather modification programs. A description of the types of observations needed by the programs is given, and an assessment of how accurately satellites can determine these necessary parameters is made.

Reynolds, D. W.↗

NASA NTRS1978

The Martian satellites - 100 years on

Studies of Phobos and Deimos, the two satellites of Mars, may provide the best observations yet of the material populating the asteroid belt. Viking observations of Phobos showing crater chains and striations are analyzed, and Mariner-9 photometry exhibiting the albedo of the satellite is discussed. A mass determination for Phobos results in a value of 1.1 times 10 to the 19th power g; the mean density of the satellite is set at about 2 g per cu cm, a value suggesting formation of the satellite from material in the asteroid belt.

Hunt, G. E.↗

NASA NTRS1978

The evolution of icy satellite interiors and surfaces

The results obtained by Consolmagno (1975) with regard to the interiors of the smaller icy satellites are presented and the evolution of the surfaces of these objects in the light of the considered models is discussed. In the discussion the icy satellites are divided into two groups. Those with radii larger than 1000 km are composed primarily of high-pressure phases of ice. In the case of satellites of this group, internal heating may produce significant melting and solid-state convection may not be important. Those satellites with radii less than 1000 km will be composed primarily of ice I and rock. They will not significantly melt and internal convection is likely to be important.

Consolmagno, G. J.↗

NASA NTRS1978

The Galilean satellites and the Jovian magnetic field

Alfven and Arrhenius (1974, 1976) have proposed that satellites may be formed by the condensation of plasma in partial corrotation in the dipole magnetic field of the central body. They conclude that the final orbit distance of the condensed material will be two-thirds of the orbit distance of the plasma. Since the Jovian field is strongly distorted beyond about 40 Jupiter radii, it is expected (assuming that plasma and magnetic field conditions have not changed significantly with time) that the first Galilean satellites would appear at about two-thirds 40 Jupiter radii or about 27 Jupiter radii. In fact Callisto, the outermost Galilean satellite, is found at 26.47 Jupiter radii. This generally supports the Alfven-Arrhenius hypothesis that the central-body dipolar magnetic field plays a role in major satellite formation and, more, specifically, that the two-thirds law has validity.

Freeman, J. W.↗

NASA NTRS1978

Low cost satellite land mobile service for nationwide applications

A satellite land mobile system using mobile radios in the UHF band, and Ku-band Communications Routing Terminals (earth stations) for a nationwide connection from any mobile location to any fixed or mobile location, and from any fixed location to any mobile location is proposed. The proposed nationwide satellite land mobile service provides: telephone network quality (1 out of 100 blockage) service, complete privacy for all the users, operation similar to the telephone network, alternatives for data services up to 32 Kbps data rates, and a cost effective and practical mobile radio compatible with system sizes ranging from 10,000 to 1,000,000 users. Seven satellite alternatives (ranging from 30 ft diameter dual beam antenna to 210 ft diameter 77 beam antenna) along with mobile radios having a sensitivity figure of merit (G/T) of -15 dB/deg K are considered. Optimized mobile radio user costs are presented as a function of the number of users with the satellite and mobile radio alternatives as system parameters.

Weiss, J. A.↗

NASA NTRS1978

A two satellite technique for measuring atmospheric surface pressure

A two-satellite system configuration is designed in which one satellite transmits a signal which is reflected from the sea surface and received by the other satellite. The time delay of the signal is measured. By selecting the geometry such that the signal path makes a small grazing angle with the sea surface, the amount of troposphere passed through and hence the magnitude of the tropospheric effect is maximized; requirements on timing accuracy are thus relaxed. The vacuum path length of the radar signals must be subtracted from the measured path length in order to compute the tropospheric effect, which is highly correlated to the atmospheric surface pressure. This is done by measuring the time delays along three additional paths. The use of an operational constellation of several satellites further decreases sensitivity to geoidal errors.

Goldfinger, A. D.↗

NASA NTRS1978

The solar power satellite concept - A space program perspective

The Space Shuttle will reduce the cost of transportation to space from thousands of dollars per pound to hundreds of dollars per pound. Studies of future systems indicate that these costs may be further reduced to tens of dollars per pound by using large space freighters, which would be required to build solar power satellites. It is pointed out that the Space Shuttle will provide a versatile tool in the 1980's to support the exploration of the solar power satellite concept as well as other space programs of the future. Three apparently different applications, related to materials processing in space, advanced satellite communications, and solar power satellites, have a number of common requirements. These include the need for large solar power arrays in space and/or the need to construct large systems in space. Consequently, a space program which includes development of the techniques for large power supplies and structural systems provides the basis for selecting and implementing any or all of these promising applications.

Kraft, C. C., Jr.↗