Digital Data Processing In Ionospheric Sounding

Data collection in the field of environmental science using analog methods has become highly problematic due to the immense information density of most measurements. One possible solution to this problem is the selection of parameters prior to the recording of the data. Certain aspects of the proposed solutions, as well as modern data analysis methods, require preprocessing and digital recording of the information. A sounding system comprising an airborne Granger 3905-1 Ionospheric Sounder and a Pulse Amplitude Digitizer uses the approach of parameter selection. Up to six arbitrarily selected frequencies can be monitored simultaneously; one ionospheric echo per frequency can be gated out and recorded in digital form on tape. This system, together with automatic calibration is the ideal basis for multi-frequency absorption and drift measurements. As a part of an airborne ionospheric laboratory, this equipment has been successfully used for absorption measurements during two eclipse expeditions, for investigations of the South Atlantic Magnetic Anomaly, and for the study of the influence of the albedo on the D-region ionization. Further experiments such as the study of ionospheric irregularities and the ground reflectivity are considered. (Author).

A system for the automated collection of ionospheric backscatter sounding and HF noise measurement data is described. The system was configured around a PDP 11/40 minicomputer and modified Barry Research FMCW sounding equipment. The real time digital signal processing associated with the backscatter sounder and noise measurement systems is discussed. The data are displayed and recorded in a calibrated mode, and examples are presented. Deficiencies noted in the operation of the system, and plans for the introduction of oblique and vertical incidence sounding conclude the report. (Author).

For the specific goal to control or predict man-made ionization effects the Defense Department has stimulated research in some areas and particularly in ionospheric physics. The results are reviewed with the implication that most of them are significant only within the larger pool of knowledge being produced by basic research. The review covers recent results gained by means of rockets and satellites on various atmospheric parameters and on the various particle inputs. Further, it reports on conjugate phenomena, on geographical features of particle influx and of electric fields and on progress in radio propagation measuring techniques. Finally, it reviews the observed effects on the ionosphere during the coordinated 12 November 1966 solar eclipse expedition. (Author).

This introductory text replaces two earlier publications (Davies 1965, 1969). Among the topics: characteristics of waves and plasma, the solar-terrestrial system, the Appleton formula, radio soundings of the ionosphere, morphology of the ionosphere, oblique propagation, importance of amplitude and phase, earth-space propagation. Annotation copyrighted by Book News, Inc., Portland, OR