Technical report | High Range Resolution Backscatter Sounder Ionograms

Abstract

Backscatter ionograms have been routinely collected for thirty years in support of the Jindalee Over-The-Horizon-Radar and Jindalee Operational Radar Network. Backscatter sounder ionograms display the power received as a function of time delay (usually expressed as group range) and transmitted frequency after radio-wave signal transmission from an antenna, propagation via the ionosphere, backscattered reflection from the Earth's surface and further propagation via the ionosphere to the receive antenna. Routine practice has been to process and retain data at a range resolution of 48.8 km and frequency resolution of 200 kHz. This resolution was set to accommodate equipment, signal processing, communications and data storage capability at the time (the 1980s). This paper describes methods used for high range resolution processing (6.1 km for 3 frequencies per 100 kHz) of the same raw data including superior radio frequency interference rejection. These superior ionograms make many additional propagation features more clearly visible.

Executive Summary

Backscatter ionograms have been routinely collected for thirty years in support of the Jindalee Over-The-Horizon-Radar (OTHR) and Jindalee Operational Radar Network (JORN). Backscatter sounder (BSS) ionograms display the radio-wave signal power received, as a function of range, after backscattered reflection from the Earth's surface for frequencies in the high frequency (HF) band. Routine practice has been to process and retain data at a resolution of 48.8 km and 200 kHz. This resolution was set to accommodate equipment, signal processing, communications and data storage capability at the time.

This paper describes methods used for high range resolution processing (6.1 km for 3 frequencies per 100 kHz) of the same raw data including superior radio frequency interference rejection. These superior ionograms make many additional propagation features more clearly visible.

The techniques described here were completed in 2008 and are being further developed for inclusion in a programme of enhancements to JORN.