A study of the ground illumination footprint of meteor scatter communication
An examination is made of the ground illumination footprint of meteor trails and its effect on the simultaneous reception of meteor scatter transmissions by multiple receivers. A technique for calculating the ground illumination footprint of individual trails which provides added insight into the physical mechanisms is presented. The probability of adjacent station reception as a function of location on the ground is calculated by computing the ground illumination footprint of individual trails at different locations and orientations within the common volume and weighting each footprint by the number of trails at that location and orientation. Two different models for the spatial arrival pattern of meteor trails are considered: the first model assumes that trails arrive uniformly over the common volume, and the second calculates the number of arrivals from the spatial distribution of meteor orbits, antenna patterns, time of day, and season. The effect of antenna patterns on the ground illumination footprint of meteor scatter communication is examined. >
Large scale space diversity in a widely spaced network of meteor scatter communication systems and its application to mobile communications
A model is developed for predicting the inherent spatial multiplexing or diversity in a widely dispersed network of meteor scatter receivers. The primary measure, network diversity, is defined as the ratio of the arrival rate of useful trails observed by the entire network to the arrival rate at an average node and is less than the number of receivers in the network. Network diversity is calculated from the ground illumination footprint of individual meteor trails and weighted by the spatial arrival pattern of trails. Predictions using the model are compared to an experiment conducted in the western US. Ramifications on the design of meteor scatter communication systems for very large network applications such as automatic vehicle location and tracking are discussed. >
A Phenomenological Theory of Radar Echoes from Meteors
The Dominion Observatory and the National Research Council, Ottawa, Canada, have undertaken a program of combined visual, photographic, and radar observations of meteors. The observational data is summarized, and general conclusions have been drawn. The radar echoes obtained from meteors have been classified into basic types according to their appearance on the range-time record of the radar display. These types include echoes indicating approach, or recession, or both. Other observed features are: durations of echoes up to several minutes, complexity of structure for echoes from brighter meteors, and appreciable delays in the appearance of the echoes. A phenomenological theory is proposed, involving a number of postulates concerning the physical conditions in an M region in the upper atmosphere. A kinetic-energy mechanism, together with an ultraviolet radiation mechanism, are suggested to account for the ionization produced by the meteor. In the M region are visualized striae, or patches, which form a fine structure such that, within the striae, the physical properties of the atmosphere emphasize the creation and maintenance of meteoric ionization as compared to the ionization produced in the intervening spaces. A qualitative explanation for all the observed echo forms is advanced on the above hypothesis. The results of other investigators on different wavelengths are consistent with this analysis.