Astronomičeskij vestnik

Ground testing results are presented for the landing platform television system (TSPP) within the complex of scientific payloads onboard the ExoMars-2022 spacecraft. In the course of the ground testing, the different operation modes have been checked and the camera characteristics have been measured and calibrated. The Space Research Institute (IKI RAS) has obtained photographic material from each camera, with the cameras being installed on a stand that simulates in full scale the ExoMars-2022 landing platform. In addition, special measurements have been collected for the cameras’ most important characteristics: horizontal and vertical angular field of view, distortion, focal length, resolution, dynamic range, vignetting coefficient, and absolute sensitivity.

There are serious contradictions between the geophysical and geochemical classes of models of the chemical composition and internal structure of the Moon, associated with the assessment of the abundance of the main oxides. The search for a potential consensus between the models was carried out on the basis of a set of geophysical and geochemical data using the Monte-Carlo method using the Markov chain scheme in combination with a method of minimization of the Gibbs free energy. The influence of the chemical composition and mineralogy of several conceptual models on the internal structure of the Moon has been studied. Two classes of chemical composition models are considered—the E models with terrestrial values of Al₂O₃ and CaO and M models with their higher content, as well as two classes of the most popular geochemical models, the Taylor Whole Moon (TWM) and Lunar Primitive Upper Mantle (LPUM) models, with ~45 wt % SiO₂, but with different concentrations of refractory oxides and FeO. In both classes of E and M models, the lunar mantle is enriched in silica (~50 wt % SiO₂) and FeO (11–13 wt %, Mg# 79–81) relative to the bulk composition of the silicate Earth (BSE, ~45 wt % SiO₂, ~8 wt % FeO, Mg# 89). Such high concentrations of SiO₂ and FeO become the determining factors for understanding the features of the mineral, velocity, and density structure of the lunar mantle. For the E and M models and geochemical models TWM and LPUM, the speed of sound and the density of stable phase associations are calculated. For E and M models, good agreement was obtained between the velocities of P- and S-waves and seismic sounding data from the Apollo program, which supports the idea of a silica-rich (olivine-pyroxenite) upper mantle. Unlike the Earth’s upper mantle, the dominant mineral in the Moon’s upper mantle is low-calcium orthopyroxene, not olivine. In contrast, the sound velocities of silica-unsaturated compositions, both FeO and Al₂O₃ enriched (TWM) and depleted (LPUM) models, do not match the seismic signatures. Thermodynamically justified restrictions on the chemical composition, mineralogy, and physical characteristics of the mantle based on the E and M models make it possible to eliminate some contradictions between the geochemical and geophysical classes of models of the internal structure of the Moon. Simultaneous enrichment in ferrous iron and silica is difficult to reconcile with the hypothesis of the formation of the Moon as a result of a giant impact from the substance of the Earth’s primitive mantle or from the substance of a shock body (bodies) of chondrite composition. Limitations on lunar concentrations of FeO and SiO₂ probably correspond to the parent bodies of some achondrites.

Modern ideas about objects approaching the Earth are discussed. This population includes near-Earth asteroids (NEAs), including potentially hazardous asteroids, short-period comets, meteoroid streams, and large sporadic meteoroids. An overview is given of the currently available information on the dynamic and physical properties of NEAs and comets. Almost 5% of the currently known NEAs are extinct cometary nuclei or their fragments. Being outwardly similar with true asteroids, they differ markedly in their dynamic and physical properties. In order to distinguish between these groups of objects, it is necessary to study both their dynamic and physical parameters. Some of the known meteoroid streams are shown to contain, along with the countless small meteoroids, also large extinct fragments of cometary nuclei, which are classified as NEAs. A meteoroid stream and such bodies belonging to it form together an asteroid–meteoroid complex. Observational and theoretical data are presented to confirm the modern understanding of near-Earth objects.