A Python data analysis and synthesis toolbox for PSWS Doppler data: A time-of flight case study

A prototype Python toolbox is available to aid HamSCI Personal Space Weather Station (PSWS) data interpretation1. The toolbox currently has two themes. First, a set of frequency- (FFT) and time-domain (autocorrelation) scripts for estimating and plotting Doppler frequency, Doppler spread and signal level of PSWS digital_RF data. For bimodal spectra an experimental script estimates Doppler of two peaks, assigns to propagation modes and tries to track even if they cross. Second, a set of scripts invoking PyLap 2D and 3D ray tracing to obtain synthetic spectrograms of one- and two-hop E and F region, low and high ray, propagation modes. Time series of take-off angle, reflection apogee and time of flight (ToF) are derived from automated PyLap simulations. Novel ToF measurements between WWV and KD7EFG, Utah, provide an interpretation challenge case study. Apogee height simulation time series show expected propagation modes, importantly showing periods with two co-propagating modes, and, by omission, suggesting when sporadic E (Es) was present. 5 MHz Es propagation, with minimal vertical height variability, and ToF of 2.12 ms, provided the benchmark to show consistent ToF measurements within 60 us. The more dynamic F region gave rise to commensurate variations in ToF. However, ToF estimates became scattered with two co-propagating modes from WWV (e.g. 5 MHz E and F). 15 MHz Es propagation showed consistent ToF of 2.19 ms from a weak signal 50 dB below one-hop F2. Fascinatingly, an interval with ToF of 14 ms reducing to 8 ms from a weak but strengthening signal was attributed, with certainty, to two-hop sidescatter using 3D PyLap simulation. One-hop via F region only occurred briefly, with correct ToF of 2.81 ms. As the 15 MHz path from WWVH opened, with a strong signal seen in Doppler shift, ToF measurements on the path from WWV, of weak two hop sidescatter, became very scattered. This case study shows the importance of being able to use PSWS Doppler analysis to interpret new ToF measurements. In conclusion, these results herald a significant advance in the HamSCI Community's ability to characterize ionospheric propagation channels.