Determination of the Lunar Ground Characteristics Using Bistatic Radar
International journal of geosciences
At present, an investigation of the lunar ground at great depths is of paramount importance. This investigation can be carried out using decameter and meter waves. This article aims to analyze the variations of the reflection coefficient at decametric, meter and decimeteric bands. A possibility of determination of lunar ground characteristics by bistatic radar using powerful ground-based transmitters at VHF and UHF bands and a receiver aboard a Moon's satellite is analysed. Appropriate
... ppropriate algorithms are considered for determination of the regolith layer thickness, dielectric permittivity, loss tangent, and density of the regolith and bedrocks. Expected results of measurements have been presented for a two-layer model of lunar ground, consisting of an upper layer with the loose porous rocks (regolith), and the rocks situated more deeply. Revealed regularities are a basis for determining the distribution of the permittivity in subsurface layer. Keywords Bistatic Radar, Lunar Ground, Regolith, Reflection Coefficient, Permittivity O. I. Yakovlev et al. 1268 the Earth, and the reverse side. Similar experiments are planned to carry out in the framework of the mission Luna-Glob using modulated radio signals in the frequency bands of 20 MHz and 200 MHz . The investigation of ground on the visible side of the Moon up to great depth is possible by method of bistatic sounding using powerful ground-based transmitters operating in the HF, VHF and UHF frequency bands, and a multichannel receiver aboard a lunar satellite. The soil explorations are fulfilled now by NASA's Mini-RF monostatic radar installed on the Lunar Reconnaissance Orbiter (LRO), which used also the Arecibo transmitter (emitting 200 kW at wavelength 13 cm) for bistatic studying of the lunar regolith  . Experiences of bistatic sounding the Moon realised by means of the first lunar missions, have shown, that frequency selection of signals accepted on the Earth allows us to separate the reference and reflected signals and to define the reflection coefficient and dielectric properties of surface rocks   . The main regularities of the radio waves scattering by a rough lunar surface have been studied in papers -, where it is shown, that this method allows estimating density of the surface rocks and statistical characteristics of the relief irregularities. The layered structure of the ground was not considered for the interpretation of experiment results. In reviews   there are presented the results of the first stage of developing the method for bistatic sounding of the heavenly bodies. The idea of bistatic location of the Moon and planets using of high-power ground-based transmitters decameter and natural sources of radio emission has been proposed in  . The study of the Moon ground at the great depth, which can be carried out at present by radar-tracking methods using decameter and meter waves, became relevant. The purpose of this article is the analysis of possibilities of sounding ground on the big depth by method of bistatic radar using powerful ground-based transmitters of meter and decameter radio waves and a receiver located on the lunar satellite. It is necessary to define the reflection coefficient for several wavelengths for the layered model of the ground depending on the position of the satellite and to solve a direct problem of bistatic sounding the lunar ground. For definition of ground characteristics, it is necessary to develop a method of solving an inverse problem, i.e. to find the horizontal and vertical distribution of the dielectric permittivity and density on a basis of the experimental values of the signal characteristics.