A Prototype Of A Portable Coherent Ionosonde Model

Vertical sounding of the ionosphere (VSI) is the oldest and still one of the most widely used methods of diagnostics of the Earth atmosphere's plasma. Today there exists a worldwide network of the VSI sounders developed by different research groups; however, the existing coverage is still not sufficient for modern scientific and operational purposes. Primarily this is because of the limited temporal and spatial resolution provided by the available VSI systems. Thus, establishing a denser global network of the VSI stations with better operational characteristics is an important topic in the ionospheric community. Being a country with an active space research program, Ukraine will benefit from having near real-time specification of the state of the ionosphere, through which the communication with satellite systems is performed and which can be affected by the presence of the ionospheric disturbances. As of today, there is not a single routinely operating VSI system in Ukraine. Establishing a system of ionospheric monitoring will be an important step in advancing national space research. This paper deals with developing and prototyping of a portable digital ionosonde that allows carrying out continuous ionospheric diagnostics without significant financial expenditures. The designed system is based on the software-defined radio (SDR) technology which offers benefits of flexibility, small form factor, low power, and low cost. The system consumes less than 50 W of input power. Operation takes advantage of using the long phase coded transmit pulse, which provides additional SNR improvement by implementing a pulse compression technique. As a result, we developed a prototype of a low-cost, low-power portable coherent ionosonde. First laboratory and field tests of the new vertical sounder have been made in Ukraine and Antarctica. In April 2017, the system was installed at the Ukrainian Antarctic station "Akademik Vernadsky" (UAS). A comparison of the ionogram measurements made at the UAS with the developed prototype system and with a conventional analog ionosonde IPS-42 showed a high quality and higher resolution of the new VSI instrument. This paper describes the principles of operation, a functional diagram, and main technical characteristics of the ionosonde. We present also the examples of ionograms and diurnal altitude dependences of ionospheric plasma frequencies, Doppler frequency shifts and intensities of the reflected sounding signals from the measurements made at the UAS and near Kharkiv. The initial tests of two identical VSI system prototypes in Antarctica and Ukraine showed the reliability and efficiency of their application for the diagnostics of the ionosphere. The developed sounder can be used as a base prototype for manufacturing of a limited number of ionosondes and their installation in Ukraine. An important advantage of the new system is its simplicity, low production cost and low power consumption, which are the most critical factors for continuous operation, especially at the remote locations like Antarctica. The authors recommend equipping several observatories in Ukraine with this kind of sounding system as the first step towards establishing the National network for monitoring ionospheric conditions and space weather.