Summary
The Transponders for Ionospheric Measurement (TIM) program will aim to create distributable channel sounding and test instrumentation that will measure and respond to radio frequency (RF) signals in the high frequency (HF) band. The goal of this effort is to leverage commercial communications devices to create test instruments.
Sky-wave and surface-wave radar commonly use transponders to create test responses that verify sensor calibration and sensor signal processing, and to provide information on the radio propagation channel. The development of low-cost software defined radio (SDR) provides an opportunity to expand that utility. Low-cost dual-frequency global positioning system/global navigation satellite system (GPS/GNSS) receivers have enabled dense sampling of the ionosphere over land.
Deploying a dense network of HF transceivers complements the GPS measurements and directly informs an understanding of the propagation determined by the bottom side of the ionosphere.