Dynasonde 21 Data Processing: Principles and First Results Obtained with the new 
8-Channel HF Radar System at Wallops Island, Virginia 
 
N.A. Zabotin, J.W. Wright, T.W. Bullett 
 
Dynasonde is a generic name for a unique ideology of ionospheric radio sounding 
which commenced development in the mid ‘60s at NOAA's forerunner in Boulder, 
Colorado, the Institute for Telecommunication Sciences and Aeronomy. The name 
itself was chosen in 1969 to denote a system competent to sound the full range 
of dynamic variation of the ionosphere. The distinguishing properties of this 
ideology are: 
 
a) Limited impact to other uses of the radio spectrum. The Dynasonde avoids 
application of long sequences of pulses at the same base frequency. Instead, 
short sequences (3 to 8) of narrowband (30 kHz) pulses are used. In these pulse 
sets the radio frequencies are slightly offset (by 1-4 kHz) from the base 
frequency in a carefully designed pattern to enable precision range measurements 
(to within a few meters) by the Stationary Phase principle. 
 
b) Direct attention to physical properties of the raw data. Mathematical 
procedures which can have undesirable consequences, such as Fourier transforms, 
pulse coding, or coherent summation, are not used. Instead, the phase and 
amplitude of received signals (from raw I&Q) are used directly. As a 
consequence, low-level Dynasonde data processing yields excellent statistics of 
recognized echoes characterized by accurate physical parameters, each with its 
individual error estimate. The same echo recognition and characterization 
process rejects false echoes and noise. 
 
c) Diverse and sophisticated methods of higher-level data processing. Owing to 
the quality and the quantity of the echoes, an autonomous classification of the 
echoes into traces is accomplished; subsequent inversion procedures address the 
appropriate traces more efficiently. Another important benefit of the Dynasonde 
data analysis is its use of physics-based criteria rather than using indirect 
procedures (such as image processing). Unique Dynasonde products include: 
dependable autonomous scaling of standard ionospheric parameters, 3-D plasma 
density inversion (NeXtYZ), small-scale irregularity diagnostics, and vector 
velocities, all obtained directly from ionogram data. 
 
Development of Dynasonde methods has benefited continuously from the excellent 
hardware design of NOAA’s last HF Radar, circa 1975-1983. Significant features 
of the old hardware included high-resolution receivers with wide dynamic range 
I&Q digital output; extensive calibration capabilities; careful attention to 
minimizing radiated interference; excellent linear performance throughout signal 
generation, transmitter amplification, antenna characteristics, receiver 
qualities, and digital data definition. The new HF Radar designed by Scion 
Associates Inc. and recently installed at NASA’s Wallops Flight Facility in 
Virginia, builds upon success of the old instrument, adding many new features. 
It is a fully digital radar system that allows very flexible programming. For 
the first time in Dynasonde practice it provides as many parallel receivers as 
receiving antennas (8 each). This means that the frequency-time (group range, 
Doppler) and spatial (echolocations, polarization) partit 
 ions of the total measurement activity, are solved for by least squares, 
entirely independently. 
 
Dynasonde 21 is a comprehensive software suite that integrates all of the 
Dynasonde data analysis methods. It has been tested in a multi-year real-time 
operation with the data from old Dynasondes. Since November 2007, real-time data 
produced by the new radar at Wallops are processed with this software. We report 
in this paper the features of the data analysis that were made possible by the 
new radar system at Wallops, and its first results. 
 
The new radar system at Wallops has provided possibilities to test the Dynasonde 
21 software in non-standard and varying operational conditions. The data 
analysis performs very dependably when the number of active channels is reduced 
from 8 to 6, 4, or even 2, and also when the effective power of the system is 
decreased by tens of decibels. The Dynasonde 21 analysis methods prove to be not 
only accurate and adaptable for many research purposes, but also extremely 
robust, the quality important for operational applications of ionospheric 
sounding systems.