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Leroy, B. E.

Publications and source records attributed to Leroy, B. E..

13 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Alternatives for satellite sound broadcast systems at HF and VHF

The National Aeronautics and Space Administration and the United States Information Agency (USIA) are currently engaged in a joint program to assess the technical and economic feasibility of direct sound broadcast satellite systems to meet USIA mission needs. The cooperative effort calls for a series of interrelated studies to provide the respective Agency managements with information on the potential role of direct broadcast satellites. Initial studies focused on HF propagation phenomena and broadcast coverage requirements. These studies served as the basis for parallel systems studies currently in progress. The systems studies are to provide a data base on various satellite configurations and systems concepts capable of supporting potential broadcast requirements ranging from a small fraction to a substantial addition to USIA requirements. Antenna concepts for LEO and GEO orbits are briefly described.

Leroy, B. E.↗
NASA NTRS1982

Satellite-aided land mobile communications system implementation considerations

It was proposed that a satellite-based land mobile radio system could effectively extend the terrestrial cellular mobile system into rural and remote areas. The market, technical and economic feasibility for such a system is studied. Some of the aspects of implementing an operational mobile-satellite system are discussed. In particular, two key factors in implementation are examined: (1) bandwidth requirements; and (2) frequency sharing. Bandwidth requirements are derived based on the satellite antenna requirements, modulation characteristics and numbers of subscribers. Design trade-offs for the satellite system and potential implementation scenarios are identified. Frequency sharing is examined from a power flux density and modulation viewpoint.

Leroy, B. E.↗
NASA NTRS1982

Satellite-aided land mobile communications system implementation considerations

It was proposed that a satellite-based land mobile radio system could effectively extend the terrestrial cellular mobile system into rural and remote areas. The market, technical and economic feasibility for such a system is studied. Some of the aspects of implementing an operational mobile-satellite system are discussed. In particular, two key factors in implementation are examined: (1) bandwidth requirements; and (2) frequency sharing. Bandwidth requirements are derived based on the satellite antenna requirements, modulation characteristics and numbers of subscribers. Design trade-offs for the satellite system and potential implementation scenarios are identified. Frequency sharing is examined from a power flux density and modulation viewpoint. Previously announced in STAR as N82-25290

Leroy, B. E.↗
NASA NTRS1980

An economics systems analysis of land mobile radio telephone services

The economic interaction of the terrestrial and satellite systems is considered. Parametric equations are formulated to allow examination of necessary user thresholds and growth rates as a function of system costs. Conversely, first order allowable systems costs are found as a function of user thresholds and growth rates. Transitions between satellite and terrestrial service systems are examined. User growth rate density (user/year/sq km) is shown to be a key parameter in the analysis of systems compatibility. The concept of system design matching the price/demand curves is introduced and examples are given. The role of satellite systems is critically examined and the economic conditions necessary for the introduction of satellite service are identified.

Leroy, B. E.↗
NASA NTRS1980

An economic systems analysis of land mobile radio telephone services

This paper deals with the economic interaction of the terrestrial and satellite land-mobile radio service systems. The cellular, trunked and satellite land-mobile systems are described. Parametric equations are formulated to allow examination of necessary user thresholds and growth rates as functions of system costs. Conversely, first order allowable systems costs are found as a function of user thresholds and growth rates. Transitions between satellite and terrestrial service systems are examined. User growth rate density (user/year/km squared) is shown to be a key parameter in the analysis of systems compatibility. The concept of system design matching the price demand curves is introduced and examples are given. The role of satellite systems is critically examined and the economic conditions necessary for the introduction of satellite service are identified.

Leroy, B. E.↗
NASA NTRS1979

Global disaster satellite communications system for disaster assessment and relief coordination

Global communication requirements for disaster assistance are analyzed in the light of operationally feasible satellite system concepts and associated system parameters. Present and planned commercially available systems are considered, together with an assessment of the associated global disaster communication yearly service costs. It is concluded that a likely number of transportable terminals required for long distance relief communications activities would be less than 10, with the transportation costs not expected to exceed 25% of the annual systems' cost. Consequently, no sound economic justification is seen for ground terminal development for the global disaster communications system.

Leroy, B. E.↗
NASA NTRS1979

Global disaster satellite communications system for disaster assessment and relief coordination

The global communication requirements for disaster assistance and examines operationally feasible satellite system concepts and the associated system parameters are analyzed. Some potential problems associated with the current method of providing disaster assistance and a scenario for disaster assistance relying on satellite communications are described. Historical statistics are used with the scenario to assess service requirements. Both present and planned commercially available systems are considered. The associated global disaster communication yearly service costs are estimated.

Leroy, B. E.↗
NASA NTRS1977

Spacecraft design sensitivity for a disaster warning satellite system

A disaster warning satellite (DWS) is described for warning the general public of impending natural catastrophes. The concept is responsive to NOAA requirements and maximizes the use of ATS-6 technology. Upon completion of concept development, the study was extended to establishing the sensitivity of the DWSS spacecraft power, weight, and cost to variations in both warning and conventional communications functions. The results of this sensitivity analysis are presented.

Maloy, J. E.↗
NASA NTRS1975

Spacecraft attitude control for a solar electric geosynchronous transfer mission

A study of the Attitude Control System (ACS) is made for a solar electric propulsion geosynchronous transfer mission. The basic mission considered is spacecraft injection into a low altitude, inclined orbit followed by low thrust orbit changing to achieve geosynchronous orbit. Because of the extended thrusting time, the mission performance is a strong function of the attitude control system. Two attitude control system design options for an example mission evolve from consideration of the spacecraft configuration, the environmental disturbances, and the probable ACS modes of operation. The impact of these design options on other spacecraft subsystems is discussed. The paper presents a discussion of the factors which must be considered in determining the ACS actuation and sensing subsystems. The effects of the actuation and sensing subsystems on the mission performance are also considered.

Leroy, B. E.↗
NASA NTRS1975

Spacecraft attitude control for a solar electric geosynchronous transfer mission

A study of the Attitude Control System (ACS) is made for a solar electric propulsion geosynchronous transfer mission. The basic mission considered is spacecraft injection into a low altitude, inclined orbit followed by low thrust orbit changing to achieve geosynchronous orbit. Because of the extended thrusting time, the mission performance is a strong function of the attitude control system. Two attitude control system design options for an example mission evolve from consideration of the spacecraft configuration, the environmental disturbances, and the probable ACS modes of operation. The impact of these design options on other spacecraft subsystems is discussed. The factors which must be considered in determining the ACS actuation and sensing subsystems are discussed. The effects of the actuation and sensing subsystems on the mission performance are also considered.

Leroy, B. E.↗
NASA NTRS1974

Performance of the SERT 2 spacecraft after 4 and one-half years in space

The SERT 2 satellite, launched in February, 1970, has recently been reactivated after being dormant for a year. The satellite orientation was changed to spin stabilization in 1973 and the satellite is now coning such that the active side of the solar arrays move into and out of the sun every 23 days. There is sufficient power to operate the ion thrusters for seven days of this cycle. The 2 ion thruster system was successfully operated; the electrical short in the accelerating grids had cleared during the year long dormant phase.

Ignaczak, L. R.↗