## 1 Introduction
### Pulsars as the Probing Signal Sources  
Radio-astronomy observations, due to the specific nature of radiation in the ranges reaching the Earth's surface, require a very specific approach and specialized tools used for observation. [PERSON] et al. (2018) presented good and detailed documentation for this issue. One of the key elements in the gallery of techniques listed above (GNSS, Formosat-3/COSMIC, and others) is to be implemented and integrated in the IGS Ionospheric Working Group. To use them as well as to apply a new, independent methods of investigations of ionosphere state. From the point of view of long-wave radio astronomy, it is necessary to find a link between the dynamics of the ionosphere and astrophysical objects observation (masers, pulsars, quasars, SNRs). The combination of the already existing ionosphere (satellite) techniques with astrophysical measurements will create a comprehensive tool for ionosphere research with unprecedented precision. The first pulsar, marked today as PSR B1919+21, was detected in 1967 at the frequency of 81 MHz by [PERSON] et al. (2018). Quite quickly it turned out that a rotating neutron star is responsible for the specific variable and very stable signal. The history of pulsar investigations as well as the methods of observation and pulsar physics is described in detail by [PERSON] et al. (2018). Half a century of pulsar research conducted with the use of radio astronomical methods (both single dish and interferometric) as well as studies in other regimes of the electromagnetic spectrum allowed us to develop a model explaining the properties of pulsar radiation. Below we briefly explain the key physical properties of pulsars which are relevant for the purposes of our project. Pulsars are rotating neutron stars, which are exotic objects with extremely strong magnetic field (up to \(10^{14}\) gauss) and can rotate up to a few hundred times per second (although a typical pulsar has a rotational period between 0.1 and 1.0 s). These objects are the final products of evolution of massive stars (at least 8 times more massive than the Sun up to about 20 solar masses [PERSON] et al. (2018)). The final stage in the life of such stars is a supernova explosion. In extreme conditions during the supernova explosion the protons and electrons merge, forming neutrons. The collapse of interior is halted only when the core shrinks to about 20 km diameter, when the density becomes high enough for the inter-neutron forces to provide an additional source of pressure. The unusual conditions within neutron stars as well as their internal structure are still an area of advanced research. The lack of any possibility of testing the theory of neutron star structure apart from studying them with astrophysical methods results in the existence of several models (see e.g., [PERSON] et al. (2018); [PERSON] et al. (2018)). The origin of a neutron star from a collapsed stellar core is what causes its extreme properties. The rapid rotation is a simple result of the conservation of angular momentum, and the strong dipolar magnetic field is a result of the compression of stellar one. The closed lines of force of the magnetic field surrounding the neutron star form the so-called \"light cylinder\". The magnetic field lines outside this structure may be open [PERSON] et al. (2018), because to be closed they would have to travel faster than the speed of light. The region on the surface of neutron star where those open field lines originate is called a \"polar cap\". The particles in the magnetosphere emitted from a \"polar cap\" are accelerated along the open field lines only. The mechanisms of particle emission and acceleration as well as radiation flux formation are still under investigation, see details [PERSON] et al. (2018); [PERSON] et al. (2018); [PERSON] et al. (2018). Pulsars' signal can also be used as tools for other fields of astrophysical research.