Application of non-standard signal processing to ELF noise characterization for the TSS1-OESEE programme

Within the framework of the TSS1 (Tethered Satellite System)-Project, a measurement program on the electromagnetic background noise was performed. This program, called OESEE (Observation on the Earth Surface of Electromagnetic Emissions), intends to carry out a number of passive detections of possible emissions by the orbiting tethered system. From theoretical considerations on the cold plasma theory in the ionosphere, the expected frequency band of these emissions should be in the order of about 1 Hz up to 60 Hz. In order to design an optimal receiver of such a signal, the noise statistical characteristics have to be taken into account. From the literature, it was shown that this noise is characterized, from the statistical viewpoint, by a non-gaussian and non-stationary behavior. This paper outlines some recently proposed applications of non-gaussian and non-stationary signal processing techniques which can be usefully applied to ELF (Extremely Low Frequency) electromagnetic noise characterization for detection and parameter estimation purposes. Some simulation examples are presented together with some results obtained from experimental data of natural background noise in the ELF range recorded at Canary Islands as a preliminary test of the TSS1 mission. The TSS1 (Tethered Satellite System) is a NASA/ASI (Agenzia Spaziale Italiana) research project.