The Invariant Measure for the Satellite Ground Station View Period Problem
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Engineering topics
Publications and source records attributed to Lo, Martin W..
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Typical LEO networks use constellations which provide a uniform coverage. However, the demand for telecom service is dynamic and unevenly distributed around the world. We examine a more efficient and cost effective design by matching the satellite coverage with the cyclical demand for service around the world. Our approach is to use a non-uniform satellite distribution for the network. We have named this constellation design NUONCE for Non Uniform Optimal Network Communications Engine.
The Mars Mapper Program (MOm) is an interactive tool for science and mission design developed for the Mars Observer Mission (MO). MOm is a function of the Planning and Sequencing Element of the MO Ground Data System. The primary users of MOm are members of the science and mission planning teams. Using MOm, the user can display digital maps of Mars in various projections and resolutions ranging from 1 to 256 pixels per degree squared. The user can overlay the maps with ground tracks of the MO spacecraft (S/C) and footprints and swaths of the various instruments on-board the S/C. Orbital and instrument geometric parameters can be computed on demand and displayed on the digital map or plotted in XY-plots. The parameter data can also be saved into files for other uses. MOm is divided into 3 major processes: Generator, Mapper, Plotter. The Generator Process is the main control which spawns all other processes. The processes communicate via sockets. At any one time, only 1 copy of MOm may operate on the system. However, up to 5 copies of each of the major processes may be invoked from the Generator. MOm is developed on the Sun SPARCStation 2GX with menu driven graphical user interface (GUI). The map window and its overlays are mouse-sensitized to permit on-demand calculations of various parameters along an orbit. The program is currently under testing and will be delivered to the MO Mission System Configuration Management for distribution to the MO community in 3/93.
Some geometric characteristics of the ground tracks of periodic orbits are examined. In particular, two theorems are proved concerning points on the ground tracks that are invariant with respect to two periodic orbits. An application of the results to the Topex/Poseidon mission is presented.
The Alaska Synthetic Aperture Radar (SAR) Facility Mission Planning Subsystem is an interactive mission planning software system on the VAXStation 2000. This system has the capability to generate satellite ephemerides and mission parameters related to synthetic aperture radar missions. The mission data can be viewed as overlays on the world map in various projections and zooms. The system also provides schedule planning capabilities, using the INGRES DBMS to keep track of the various plans and schedules generated by the mission planner.