The DST group ionospheric sounder replacement for JORN

Abstract

The Jindalee Over-the-horizon Radar Network (JORN) is an integral part of Australia's national defense capability. JORN uses a real-time ionospheric model as part of its operations. The primary source of data for this model is a set of 13 vertical-incidence sounders (VIS) scattered around the Australian coast and inland locations. These sounders are a mix of Lowell digisonde portable sounder (DPS)-1 and DPS-4. Both of these sounders, the DPS-1 in particular, are near the end of their maintainable life. A replacement for these aging sounders was required as part of the ongoing sustainment program for JORN. Over the last few years the High-Frequency Radar Branch (HFRB) of the Defence Science and Technology (DST) Group, Australian Department of Defence, has been developing its own sounders based on its successful radar hardware technology. The DST Group VIS solution known as PRIME (Portable Remote Ionospheric Monitoring Equipment) is a 100% duty cycle, continuous wave system that receives the returned ionospheric signal while it is still transmitting and operates the receiver in the near field of the transmitter. Of considerable importance to a successful VIS is the autoscaling software, which takes the ionogram data and produces an ionogram trace (group delay as a function of frequency), and from that produces a set of ionospheric parameters that represent the (bottomside) overhead electron density profile. HFRB has developed its own robust autoscaling software. The performance of DST Group's PRIME under a multitude of challenging ionospheric conditions has been studied. In December 2014, PRIME was trialed at a JORN VIS site collocated with the existing Lowell Digisonde DPS-1. This side-by-side testing determined that PRIME was fit for purpose. A summary of the results of this comparison and example PRIME output will be discussed. Note that this paper compares PRIME with the 25 year old Lowell Digisonde DPS-1, which is planned to be replaced. Our future plans include PRIME comparisons with the much newer Digisonde DPS-4D located at Learmonth in Western Australia.

Separation of O/X Polarization Modes on Oblique Ionospheric Soundings

“…During two separate data collection periods (July 2011 and December 2011) the receive antenna was set up at Edinburgh (34.73°S, 138.65°E), with a collocated VIS transmit system, similar to the transmit system used in PRIME (Harris et al, ). The first series of vertical soundings were taken with the tilt axis parallel to one of the antenna arms (corresponding to Figure ).…”

“…Measurements were taken at different angles from horizontal, from 0° to 60°. The ionograms were processed using the standard PRIME software (Harris et al, ), and the phase separation between the O and X modes was recorded. Figure shows the ionograms and phase histograms from each rotation angle.…”

“…In order to separate the two canonical propagation modes of the ionosphere, VIS systems use a pair of orthogonal receive antennas; this allows the measurement of the polarization of the incident waves. For instance, the PRIME system developed by Harris et al () uses a pair of small, vertically oriented magnetic loops in a perpendicular configuration. For a vertically incident circularly polarized wave, each loop will receive the same amplitude but there will be a ±90° phase difference between the two received signals.…”

A Robust Feature Extraction and Parameterized Fitting Algorithm for Bottom‐Side Oblique and Vertical Incidence Ionograms

“…Along with a low‐power (frequency‐modulated continuous‐wave) HF transmitting system, also developed by DST Group, this offers a complete point‐to‐point sounding capability. A customized configuration of the DST Group system for VI measurements with o / x separation has previously been reported (Harris et al, ). DST Group has also developed a solution for the reliable automatic separation of oblique o / x returns using twin‐polarized antennas (Harris et al, ), although it is not part of the standard DORS configuration.…”

A Robust Automatic Ionospheric O/X Mode Separation Technique for Vertical Incidence Sounders

“…This algorithm can provide high-quality separation even in difficult ionospheric conditions. In this paper we describe the algorithm and demonstrate its consistency and reliability in successfully separating 99.4% of the ionograms during a 27 day experimental campaign under sometimes demanding ionospheric conditions.As part of support to the Jindalee Operational Radar Network (JORN), the High-Frequency Radar Branch (HFRB) of the Defence Science and Technology (DST) Group developed a VIS solution called PRIME (Portable Remote Ionospheric Monitoring Equipment) (Harris et al, 2016). PRIME is a continuous wave system with a 100% duty cycle, allowing for good signal-to-noise ratio at very low peak transmitter power.…”