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Aerospace and Electronic Systems Magazine, IEEE

Issue 1 • Date Jan. 1990

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Displaying Results 1 - 4 of 4
  • Large area solar cells for future space power systems

    Page(s): 25 - 29
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (343 KB)  

    Space silicon solar cell technology has matured to the extent that large-area planar silicon cells can be fabricated in sizes up to 8 cm*8 cm with efficiencies up to approximately 15%. In order to achieve substantially higher efficiencies, cells based on GaAs are required. It is shown that, subject to certain boundary conditions, the efficiency of GaAs/Ge cells can reach 24% when used in the dual-junction configuration or approximately 19.5% if the Ge substrate is passive. The electrooptical properties of these cells are reviewed, and prospects for achieving these efficiency goals are presented. Experimental performance data are given.<> View full abstract»

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  • Design of the Space Station Freedom power system

    Page(s): 19 - 24
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (447 KB)  

    The design of Space Station Freedom's electric power system (EPS) is reviewed, highlighting the key design goals of performance, low cost, reliability, and safety. The EPS design is divided into three separate areas: power generation and storage, power distribution, and power management and control. Both photovoltaic and solar dynamic power generation and storage systems are used. Tradeoff study results that illustrate the competing factors responsible for many of the more important design decisions are discussed. Reliability and maintainability, as well as verification and testing, are addressed.<> View full abstract»

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  • Potential interference sources to GPS and solutions appropriate for applications to civil aviation

    Page(s): 3 - 9
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (639 KB)  

    When the GPS (Global Positioning System) is subjected to interference, the system performance gradually deteriorates as the interfering levels increase. Two modes of interference are discussed in detail, namely, that from transmissions at frequencies close to the GPS frequencies and that from transmissions with a harmonic in the GPS band. It is argued that the former requires RF filtering in the receiver with a quality better than that generally specified. The latter cannot be dealt with in such a way. Measurements carried out on the harmonic levels transmitted by one UK TV transmitter and several hundred aircraft VHF transmitters are reported. The measurements show there is a measurable level of harmonics in the GPS band. The UK TV transmitter does not, however, represent a threat to aviation unless the aircraft is so close as to represent a physical danger. The probability that one aircraft's VHF transmitter will interfere with the GPS receiver on another aircraft is tolerably small, but there is a significant probability that a GPS receiver can suffer when there is a VHF transmission from the same aircraft. Several recommendations are made, including an international effort to ensure that spurious emissions are both quantified and kept at a level significantly lower than that achieved today.<> View full abstract»

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  • An overview of a Global Positioning System Mission Planner implemented on a personal computer

    Page(s): 10 - 18
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (772 KB)  

    The Global Positioning System (GPS) Mission Planner (GMP) program, which has been implemented on an IBM PC, is described in terms of its features and architecture, and sample outputs are presented. The GMP was written to permit operational units to plan missions and to accomplish survivability and navigation assessments based on realistic trajectories, GPS almanac data, broadband jammer specifications, and digital terrain elevation data (DTED). GMP supports trajectory generation for generic air, land, or naval vehicles and has 'sanity' checks for altitude acceleration, terrain slope, and velocity limits. A survivability measure is computed based on exposure time to various threat types. Yuma-type almanac data are used to support the GMP to define GPS satellite orbits. Jammers, threats, and trajectory wavepoints may be defined by either keyboard entry (e.g. longitude, latitude, and altitude) or via mouse and cursor on a displayed pseudo-color DTED map on the PC monitor. Satellite visibility and best dilution-of-precision (DOP) are computed using DTED. jammer visibility and power levels at the vehicle are similarly computed. A realistic body masking and antenna gain model is used to compute carrier-to-noise densities for each visible satellite. A navigation assessment program emulates a multichannel receiver to generate position and velocity measurement uncertainties. An integrated Kalman filter generates position and velocity navigation estimates. Results are graphically displayed to the operator.<> View full abstract»

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Aims & Scope

The IEEE Aerospace and Electronic Systems Magazine publishes articles and tutorials concerned with the various aspects of systems for space, air, ocean, or ground environments.

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Editor-in-Chief
Teresa Pace, PhD EE
Chief Engineer SenTech
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