The paper presents the results of statistical modeling of the entry of near-Earth asteroids (NEAs) into near-Earth space (NES)—a sphere with a radius of 0.01 AU around the Earth. Distributions of asteroids by direction and velocity of entry into NES are constructed. The NEA population was modeled using the NEOMOD software with subsequent integration of the dynamic evolution for 110 years using the REBOUND package. It is shown that: 1) the number of asteroids larger than 10 m entering NES is approximately 1000 per year; 2) up to half of the asteroids can enter NES from the dayside hemisphere; 3) the asteroid flux density is increased in the solar and antisolar directions. Typical velocities of approach to the Earth when entering the NES are approximately 7.5 km s ^-1 (the velocities range is from 0 to 30 km s ^-1 ). The distribution of entries by distance and velocity relative to an observer located at the Lagrange point L_1 of the Sun–Earth system is also calculated. These distributions can be useful in designing the System of Observation of Daytime Asteroids (SODA).

Тема малых тел Солнечной системы — это гигантская область научных исследований. Малые тела несут инфор- мацию обо всех уголках Солнечной системы. Важно, что многие фундаментальные исследования малых тел имеют очень тесную связь с практическими вопросами нашей жизни. В частности, происхождение и эволюция популя- ции ОСЗ (объектов, сближающихся с Землей) тесно связаны с проблемой астероидно-кометной опасности. Ранее в проектe OTN (Optical Transient Network) [1], получившего затем название BITDN (BRICS Intelligent Telescope and Data Network), предагалось создать сеть из нескольких широкоугольных телескопов 1-метрового класса и включить в список задач сети помимо наблюдений транзиентных астрофизических явлений также и тематику ОСЗ. В данной работе анализируются перспективы инструментов для наблюдений ОСЗ и делается вывод, что наряду с 1-м теле- скопами необходима широкая сеть малоапертурных инструментов, позволяющих очень быстро (за часы) провести обзор всего неба для обнаружения малых (декаметровых) астероидов в околоземном пространстве. Предлагается мультиапертурный вариант такого инструмента. The topic of the Solar System small bodies (SSSB) is a gigantic field of scientific research. Small bodies carry information about all corners of the Solar system. It is important that many fundamental studies of small bodies have significant connections with the practical issues of our lives. In particular, the origin and evolution of the population of NEOs (near- Earth objects) are closely related to the problem of asteroid-comet hasard. Earlier, the OTN (Optical Transient Network) project [1], now called BITDN (BRICS Intelligent Telescope and Data Network), proposed to create a network of several 1-meter wide-angle telescopes and include in the list of network tasks, in addition to observations of transient astrophysical phenomena, also the subject of NEOs. In this paper, the prospects of instruments for observing NEOSs are analyzed and it is concluded that, along with 1-m telescopes, a wide network of low-aperture instruments is needed, allowing very quickly (in hours) to survey the entire sky and detect small (decameter) asteroids in the near-Earth space. A multi-aperture version of such a telescope is proposed.

The paper presents the results of statistical modeling of the entry of near-Earth objects (NEOs) into the near-Earth space - a sphere with a radius of 0.01 AU around the Earth. The distributions of asteroids in the direction and velocity of approach to the Earth are constructed. The NEO population was modeled using the NEOMOD package and integrated for 110 years using the REBOUND package. The main results are: 1) the number of asteroids larger than 10 m in size entering to near-Earth space is approximately 1000 per year; 2) up to half of the asteroids can enter the near-Earth space from the side of the day-time-hemisphere; 3) there is anisotropy in the flux density of incoming asteroids. Typical velocity of approach to the Earth at the entrance to the near-Earth space is approximately 7.5 km/s (maximum speed can reach up to 30 km/s). These distributions can be useful in the design of a System of Observation of Day-time Asteroids (SODA).

The ``Milky Way'' space safety program is under development in Russia. A part of the program implies the launch of a special spacecraft aimed to detect decameter asteroids coming from the day sky (from the sunward hemisphere) as well as to predict space weather and monitor the Sun's activity. The spacecraft will be launched to the Sun–Earth L1 point. The payload SODA (System for Observation of Daytime Asteroids) is under development at INASAN. The SODA concept is based on the results of the previous, conceptual, phase of the project. We present a general outline of SODA and give some new features in more detail. IKI RAS is responsible for the second part of the spacecraft payload related to space weather and solar activity.

Planned for the launch in late 20s Spektr-UF space observatory, being created in Russia, is designed to obtain images and spectra of space objects in the ultraviolet region of the electromagnetic spectrum (115 - 310 nm). An important part of the observatory is a special software - an exposure time calculator ( ETC). This software is necessary for planning and implementing the observatory's scientific program. It allows not only to evaluate the possibility of registering a signal from an astronomical object of interest, but also to prepare and select applications, as well as draw up an observation program. In preparation for the launch of Spektr- UF, an exposure calculator for this observatory was developed, with which users can plan photometric and spectral observations of various astronomical objects. When developing this program, the experience of other missions, primarily the Hubble Space Telescope (HST), was used. The work reviews the main capabilities of the Spektr-UF ETC and also presents a mathematical model of this calculator that characterizes the signal recording process. Based on real examples, the possibility of implementing photometry and spectroscopy modes for astronomical objects using various scientific instruments of the observatory is discussed. And some observational limits are shown. Plans for the improvement of the ETC are discussed too.

Создаваемая в России крупная космическая обсерватория «Спектр-УФ» предназначена для получения изображе- ний и спектров космических объектов в недоступном для наблюдений наземными инструментами ультрафиолетовом участке электромагнитного спектра: 115–310 нм. Обсерватория планируется к запуску в конце 20-х годов, и уже начата подготовка потенциальных пользователей к эффективной работе с ней. Необходимой составляющей обсерва- тории для планирования и реализации научной программы (подготовка заявок и составление программы наблюде- ний) является специальное программное обеспечение, которое позволяет оценить возможность регистрации сигнала от интересующего астрономического объекта. Исторически такое программное обеспечение называют калькулято- ром экспозиций. В рамках подготовки к запуску обсерватории «Спектр-УФ» создана первая версия калькулятора экспозиций с возможностью работы через web-интерфейс. При разработке данного программного обеспечения ис- пользовался опыт других миссий (прежде всего космической обсерватории «Хаббл» (HST)). В работе представлены основные возможности калькулятора экспозиций «Спектр-УФ». Поскольку это первая публикация о калькуляторе, в ней приведена краткая справка по научным приборам обсерватории и лежащие в основе программ калькулятора математические выражения, характеризующие процесс регистрации сигнала. На основе реальных примеров обсужда- ется возможность осуществления режимов фотометрии и спектроскопии точечных и протяженных астрономических объектов с использованием различных научных приборов обсерватории. Также обсуждаются планы развития дан- ного калькулятора. The large space observatory Spektr-UF, being created in Russia, is designed to obtain images and spectra of space objects in an ultraviolet region of the electromagnetic spectrum (115–310 nm) that is inaccessible to observations by ground-based instruments. The observatory is planned to be launched in the late 20s and the training of potential users for effective work with it has already begun. A necessary component of the observatory for planning and implementing a scientific program (preparation of applications and preparation of an observation program) is special software that allows one to evaluate the possibility of registering a signal from an astronomical object of interest. Historically, such software is called an exposure calculator. In preparation for the launch of the Spektr-UF observatory, the first version of the exposure calculator has been created with the option to work via a web interface. The experience of other missions (primarily the Hubble Space Telescope, HST) was used to develop of this software. The paper presents the main features of the Spektr-UF exposure calculator. Since this is the first publication about the calculator, it provides a brief reference to the scientific instruments of the observatory and the mathematical expressions underlying the calculator programs that characterize the signal registration process. Based on real examples, the possibility of implementing photometry and spectroscopy modes of point and extended astronomical sources using various scientific instruments of the observatory is discussed. Plans for the improvement of this calculator are discussed too.

The study of small bodies of the Solar system provides the key to understanding the processes of its formation and evolution. Basic science here is closely related to the applied aspects. First of all, this is true in relation to Near-Earth Objects (NEOs). The brief overview focuses on the discussion of such links. In particular, the following two topics connecting fundamental and practical issues are considered: origin, characteritics, and evolution of the NEO population $\leftrightarrow$ the problem of asteroid-comet hazard; meteoroids of both cometary and asteroid origin $\leftrightarrow$ safety of space activities in near-Earth space. The issues of coordination of research on small bodies topic both at the domestic and international levels are briefly discussed too. Special attention is paid to the prospects for coordinating research work on small bodies within the framework of the federal project ``Mlechny Put'' (Milky Way).

На основе данных третьего выпуска каталога КА Gaia, содержащих спектры отражения астероидов, были проведены исследования астероидов, сближающихся с Землей (АСЗ). Спектры отражения около 100 представителей групп Атона, Аполлона и Амура были использованы для определения их спектрального класса. Для 47 астероидов такая оценка была сделана впервые. Для удобства классы были сгруппированы в более широкие спектральные группы (по Толену). Распределение по спектральным группам (в среднем 60% S-группа, 20% C-группа, 20% другие) соответствует результатам, полученным ранее с использованием других данных по большей выборке объектов. Такое распределение остается похожим на то, что известно для АСЗ разных размеров. Несмотря на численное преобладание в выборке АСЗ астероидов группы S, астероиды примитивных типов (группы С) обнаруживаются и на очень малых перигелийных расстояниях, что косвенно может подтверждать массовость явления сублимационной активности астероидов.

Как показало Челябинское событие 15 февраля 2013 г., столкновения малых (декаметровых) тел с Землей могут представлять опасность для жителей нашей планеты. Такие тела малозаметны и могут быть систематически обна- ружены только в околоземном космическом пространстве. Необходима всемирная сеть наземных оптических телеско- пов, позволяющая очень быстро обследовать все ночное небо для обнаружения небольших астероидов в околоземном космическом пространстве. Однако значительная часть объектов, сближающихся с Землей (ОСЗ), приближается к Земле в дневное время, и их можно обнаружить только с помощью специальных космических средств. В предыду- щих статьях мы предложили космический проект СОДА (Система обнаружения дневных астероидов), направленный на обнаружение таких ОСЗ на короткой шкале времени (часы). В этой статье мы кратко представляем обновленную информацию о проекте СОДА в сравнении с другими аналогичными космическими проектами. Особое внимание уделяется рассмотрению синергии наземных и космических телескопов для эффективного обнаружения ОСЗ де- каметрового класса. Обсуждаются перспективы международного сотрудничества по проекту SODA, в частности, в рамках сотрудничества стран БРИКС в области астрономии. As demonstrated by the Chelyabinsk event on February 15, 2013, collisions of the small (decameter class) near-Earth objects (NEOs) with the Earth can pose a threat to the inhabitants of our planet. Such bodies are faint and can be systematically detected only in near-Earth space. A world-wide network of ground-based instruments is needed, allowing quick survey of the entire night sky to detect small asteroids in near-Earth space. However, a significant portion of NEOs approach the Earth from the day-time sky and they can only be detected with special space-based facilities. In previous papers we suggested the space project SODA (System of Observation of Day-time Asteroids) aimed to detect such NEOs on a short-time scale (hours). In this paper we briefly present updated information about the SODA project in comparison with other similar space projects. Special attention is drawn to considering the synergy of ground-based and space telescopes in exhaustive discovery of decameter class NEOs. The prospects for international cooperation on the SODA project are discussed, in particular, within the framework of the BRICS countries collaboration on astronomy.

Based on the data from the third edition of the Gaia catalog, containing the reflectance spectra of asteroids, studies of near-Earth asteroids (NEAs) were carried out. The reflectance spectra of about 100 representatives of the Aten, Apollo and Amor groups were used to determine their spectral class. For 47 asteroids such an assessment was made for the first time. For convenience, the classes were grouped into broader spectral groups (according to Tholen). The distribution by spectral groups (average 60

A model of dynamical evolution of meteoroid swarm is applied to study the problem of difference in mass spectra of meteoric bodies during meteor showers and for sporadic meteors. It is demonstrated that mass spectra forms within meteoroid stream. Qualitative behavior of mass index in model is consistent with observational data.

The current state of the problem of the origin and transport of `heavy' (A > 4) chemical elements in the Universe is discussed. The beginning of stellar nucleosynthesis (SNS) dates apparently to z greater than or similar to 20 redshift epochs (age of the Universe t(U) less than or similar to 180 Myr). Presently, SNS traces are observed in some cases in galaxies at redshift z similar to 10-15 (t(U) -500-270 Myr). A massive redistribution of chemical elements from galaxies over the entire Universe became possible, primarily under the action of powerful explosions, in the reionization period at z less than or similar to 6 (t(U) greater than or similar to 940 Myr). A correct interpretation of observational data requires an in-depth understanding of the transport and mixing dynamics of chemical elements in the Universe. Theoretical models predict their extremely nonuniform distribution in a range from the interstellar medium on spatial scales of a few hundred light years to the intergalactic medium spanning tens of millions of light years. This is observed in absorption spectra of quasars up to redshift z similar to 6 and results in observational selection. The review focuses on the early stages of the history of the Universe's chemical enrichment as it is currently understood given the observational selection effects. Observational data and theoretical ideas underlying the modern understanding of the complex process of the Universe's chemical evolution are outlined.

Chemical abundance variations in the ISM provide important information about the galactic evolution, star-formation and enrichment histories. Recent observations of disk galaxies suggest that if large-scale azimuthal metallicity variations appear in the ISM, they are linked to the spiral arms. In this work, using a set of chemodynamical simulations of the Milky Way-like spiral galaxies, we quantify the impact of gas radial motions~(migration) in the presence of a pre-existing radial metallicity gradient and the local ISM enrichment on both global and local variations of the mean ISM metallicity in the vicinity of the spiral arms. In all the models, we find the scatter of the gas metallicity of \approx0.04-0.06 dex at a given galactocentric distance. On large scales, we observe the presence of spiral-like metallicity patterns in the ISM which are more prominent in models with the radial metallicity gradient. However, in our simulations, the morphology of the large-scale ISM metallicity distributions significantly differs from the spiral arms structure in stellar/gas components resulting in both positive and negative residual~(after subtraction of the radial gradient) metallicity trends along spiral arms. We discuss the correlations of the residual ISM metallicity values with the star formation rate, gas kinematics and offset to the spiral arms, concluding that the presence of a radial metallicity gradient is essential for the azimuthal variations of metallicity. At the same time, the local enrichment alone is unlikely to drive systematic variations of the metallicity across the spirals.

This work examines the formation and evolution of meteoroid streams formed during collisions of near-Earth asteroids (NEAs) with objects in the Main Asteroid Belt (MAB). This collision scenario is considered more likely compared to collisions between NEAs, since many NEAs, by virtue of their origin, intersect the MAB region, in which the density of objects is significant compared to the inner regions of the Solar System. The resulting meteoroid streams have a number of differences from streams of cometary origin, both in terms of the formation of the stream and during further dynamic evolution. In this paper, estimates are obtained for the rate of meteoroid formation as a result of collisions of NEAs with MAB asteroids. Based on high-speed collision models and data from the DART experiment, possible particle size and velocity distributions are obtained. Numerical modeling of the dynamics of the resulting meteoroid stream was carried out, considering gravitational disturbances and radiation forces, and the influence of the initial emission velocity on the evolution of the stream was studied. An analysis of the rate of dust production was carried out considering the distribution of the current NEA population, and it was concluded that the rate of influx of meteoroids of asteroid and comet origin (in mass terms) can be quite comparable.

As was shown in papers [1, 2] and other studies of these authors, sublimation–dust activity in some primitive-type asteroids of the Main asteroid belt (MAB) correlates with the near-perihelion position of asteroids in orbit. These results suggest that activity of this kind is induced by the sublimation (cometary) mechanism, i.e., release of dust particles from the surface of evaporating ice-bearing layers. It is considered that these layers become bared due to collisions between asteroids in the MAB. However, collisions may also directly result in ejecting the dust matter (the impact mechanism). Here, we consider the both mechanisms. The frequency and effectiveness of impacts have been quantitatively estimated. It has been shown that the collision frequency of projectile asteroids (impactors), the kinetic energy of which is higher than (1−3) × 10 10 J (sufficient to eject a significant amount of dust), with a target asteroid ~100 km across (by an example of asteroid 145 Adeona) is up to ~2 yr –1 . For the characteristic time of dust activity assumed at 0.01 yr, we found that, at any given time moment, among ~300 MAB asteroids larger than 100 km in diameter, several asteroids may be active due to the impact mechanism action. It is noted that this estimate is consistent with observations. To make the cometary mechanism effective, the collisions should be more powerful (the characteristic energy is 10 13 J) for excavating the ice-bearing layers over a sufficiently large area (up to 0.1 km 2 ). The frequency of powerful collisions is low, but the regions of uncovered ice-bearing layers exist for a long time. Outbursts of solar activity and heating during the asteroid’s passage along the perihelion part of the orbit may provide for the observed frequency of sublimation activity in large primitive asteroids of the MAB (there are about 200 of them). According to our model, approximately one large asteroid is active at any given time moment. Further observations are required to confirm this estimate.

The history of crater formation on the Moon idicates that the number of NEAs larger than 50 m practically did not change over the past 2–3 Gyr. On the other hand a dynamic scale of the NEA population, which could be characterized by the depletion time by half t NEA , is many orders of magnitude shorter. There are significant variations of t NEA estimates by other authors. It is important to know this value more precisely, since this knowledge imposes restrictions on the mechanisms of replenishment of the NEAs, the lifetime of the Main Asteroid Belt, etc. In the Zolotarev & Shustov (2021) we have estimated t NEA as 3.5 million years. We noted either that t NEA for subgroups of NEAs depends on the initial orbital parameters of the subgroups. In the current study we considered this dependence quantitively. We have integrated orbits of 10 000 asteroids larger than 1 km and q <1.72 AU over 20 Myr. These sample essentially includes all large NEAs (>1km). The NEA subsample is considered to be complete. We made integrations with the REBOUND software package using the MERCURIUS hybrid scheme (Rein et al. (2019)). To reveal dependence of t NEA on orbital parameters t NEA (a, e, i) we divided the NEA subsample into 18 subgroups according to their orbital parameters. We found that t NEA is substantially higher for subgroups with higher i and e . There is strong dependence of t NEA on a . All these dependencies are explained by a different number of close approaches of asteroids from NEA subgroups to planets. We found that depletion of total NEO population can be approximated remarkably well with the following expression: N(t)/N 0 = exp (−0.5× t 0.33 )where N 0 is an initial number and N(t) – a current number of NEAs.

-The brief review summarizes data on the chemical and mineral composition, as well as on the physical properties, of the first extrasolar comet 2I/Borisov, obtained from observations that were carried out from September 2019 to the end of March 2020. It is noted that the qualitative chemical composition of the volatile and mineral components comet 2I/Borisov is similar to the composition of comets in the Solar System, but there are differences that indicate the specific conditions for the formation of its nucleus in a circumstellar gas and dust disk. Different release rates of CO and H2O molecules in the vicinity of perihelion indicate the possible heterogeneity of the comet's nucleus, which was formed from more homogeneous ice blocks, but differing in composition. These constituent blocks could have formed over a wide range of radial distances: from the snow line of H2O to the CO snow line. Their accumulation in the comet's nucleus indicates large-scale mixing of protocometary bodies in the circumstellar disk. No spectra of finely crystalline magnesium silicates were found in cometary coma of 2I/Borisov, which can be interpreted as the absence of a significant amount of gas and dust transfer from the inner hot regions of the disk to the outside, into the zone of formation of protocometary bodies.

The mission Ultraviolet Researcher to Investigate the Emergence of Life (URIEL) is designed to carry out low dispersion (600-1,000) UV spectropolarimetry in the 140-400 nm spectral range to investigate the formation of planetary systems, its interaction with stellar winds and search for signatures of prebiotic molecules by remote sensing of small bodies in the Solar System (comets and meteorites) in near Earth orbit. URIEL is conceived as a 50cm primary telescope with a RitcheyChrétien mounting. The telescope is equipped with a single instrument, the ultraviolet spectropolarimeter, whose low dispersion will enable resolving the main spectral features whilst guaranteeing enough flux per resolution element for the Stokes parameters to be measured to an accuracy of 500 ppm in the full range. According to recent calculations based on the chemical analysis of meteorites, this accuracy suffices for the remote detection of alanine by its optical activity at 180 nm in nearby minor bodies. In this sense, URIEL is a pathfinder mission to the technology that will enable remote sensing of amino acids and addressing the source of the chirality imbalance in Earth's bio-molecules.

The calculation results of the evolution of meteoroid streams obtained using the model described by Shustov and Zolotarev (2022) are presented. The model was implemented using the REBOUND software package. The evolution of model meteoroid streams associated with comets 96P/Machholz and 2P/Encke was considered. It was shown that the distribution of mass spectra is formed in the meteoroid stream: the mass index at the center of the stream s < 2, while at the edge of the stream s may exceed 2. There are two causes of such changes in the structure of the meteoroid stream: (1) the initial velocity of particle ejection from the comet nucleus strongly depends on the particle size, and small particles move away from the nucleus faster; (2) small particles are more exposed to the action of radiation forces and therefore scatter in space faster than large particles, so the mass index at the center of the stream decreases. These results are consistent with the results obtained by other authors from observations of meteor streams, in particular, the Arietids stream.

The World Space Observatory–Ultraviolet mission (Spektr-UF, WSO-UV) is an efficient multipurpose orbital observatory for high- and low-resolution spectroscopy, high sensitivity imaging and slitless spectroscopy in the ultraviolet wavelength range. It will open new opportunities in (exo)planetary science, extragalactic astronomy, stellar astrophysics and cosmology. The observatory is based on a complex of scientific instruments including the T-170M telescope (aperture 170 cm), spectrographs and imagers. The payload should be ready in 2025. We briefly describe the current status of the mission.