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We consider the construction of the spacecraft's return trajectories from the Moon to the Earth for delivering regolith to a specified region of the Russian Federation. During ballistic mission design, we first use a simplified motion model to define the initial approximation for the return trajectory, moving along which the spacecraft enters the dense layers of the atmosphere at a certain angle and lands at a specified region of our planet. Further, the trajectory is refined taking into account the perturbations from the gravitational fields of the Earth, the Moon and the Sun. Numerical and graphical results are presented. It is shown that the restrictions on the satellite's entry angle into the Earth's atmosphere cannot be met for each flight date. [ABSTRACT FROM AUTHOR]

This paper aspires to contribute to the limited field of neorealist scholarship on security affairs in outer space by conducting a case study of the Russian Federation's security policy in the celestial sphere. In recent years, Russia has emerged as one of the key players in the international politics of outer space. However, Russia's strategy of developing its space defense assets, while in parallel launching diplomatic initiatives in international organizations calling for the avoidance of an arms race in outer space, is ambiguous. I argue that the neorealist paradigm elucidates this case by highlighting the intensifying balancing trajectories of contemporary outer space security affairs. In a first step, hypotheses on states' behavior in the field of outer space armament and arms control are derived from the body of neorealist scholarship on terrestrial international politics. This is followed by hypothesis testing against the case of Russia's space security politics. It is contended that Russia is engaging in a predominantly competitive endeavor vis-à-vis the United States by utilizing a hybrid approach of internal and external balancing, as well as a pragmatic instrumentalization of international institutions to leverage its own economically disadvantaged position in outer space. [ABSTRACT FROM AUTHOR]

• An encounter trajectory that meets the needs of Deep Space Mission ASTER was identified and is presented. • Expected results achievable in a successful exploration of asteroid 2001SN263 are presented. • ALR_Sim_Tracks – A mission analysis simulation tool dedicated to optical instruments in this mission was created. In cooperation with Russia, the Brazilian deep space mission ASTER plans to send a small spacecraft to investigate the triple asteroid 2001-SN263. The nearest launch opportunities for this project include June 2022 and June 2025. One main exploration campaign is being planned with focus on the largest asteroid (Alpha). Among the instruments under development, a laser altimeter (named ALR) was preliminarily designed and presented in 2010–2011. Many studies to define mission and instruments requirements were performed aiming at the characterization of important issues for the successful realization of the mission. Among them, the identification of a suitable trajectory that could be followed by the ASTER spacecraft in the encounter phase, when the main campaign will take place. This paper describes the effort undertaken with focus on the laser altimeter operation. Possible encounter trajectories were modelled and simulated to identify suitable approach parameters and conditions allowing the accomplishment of the intended investigation. The simulation also involves the instrument operation, considering approach geometry, attitude, relative motion, time/date, and the dynamics of the main asteroid. From the laser altimeter point of view, keeping in mind the desired coverage results (50% minimum surface coverage of asteroid Alpha, complying with horizontal and vertical resolution requirements), results point out crucial features for the encounter trajectory, like the need for a small inclination (10-6 degrees; with respect to the asteroid's orbit), the most favourable spacecraft positioning (between the Sun and the asteroid) and pointing condition (back to the Sun), the minimum amount of achievable surface coverage (58%, focused on central areas), and the most proper time to conduct the main campaign (January 2025). Concerning the instrument, results offer refined values for divergence angle (500 to 650 μrad, half-cone), pulse repetition frequencies (from 1/20 to 1 Hz), and consequent data generation rates. A simulation tool that can use any 3D generated trajectories as input data was created for the analyses presented here. Although created for the ALR in this mission, this simple analysis tool can be adapted to other instruments in this or other missions. [ABSTRACT FROM AUTHOR]

Abstract: HF radio wave observations have been carried out with an oblique ionospheric sounding (OIS) method on the radio path from St. Petersburg to Longyearbyen (Svalbard), and experimental ionograms were obtained for December 2001. These ionograms have been analysed to investigate the impact of the main ionospheric trough (MIT) and magnetic disturbances on the signals on this path. The observations during weakly disturbed (K р =2) magnetic conditions on 14–15 December 2001 were compared with predictions from ray-tracing through a numerical model of the ionosphere. The ray-tracing computer program synthesizes the OIS ionograms by means of the “shooting method”. This method calculates trajectories of HF radio waves for different values of elevation angle and transmission frequency. There was a variety of calculated trajectories, from which we choose those which reach the receiver, and the selected paths provide a synthesis of the oblique ionograms. To simulate HF radio wave propagation, we apply a three-dimensional distribution of the electron density calculated with the mathematical model of the high-latitude ionosphere developed in the Polar Geophysical Institute (PGI). These numerical simulations permit us to interpret specific peculiarities of the OIS data such as abnormal propagation modes, increased delays of signals, enhanced MOF (maximum observed frequency) values etc. New results of the study are summarised as follows. (1) An unusual feature of the propagation along the path is the change of propagation mechanism during substorms on entering a path midpoint (or 1-hop reflection point) to the MIT. (2) Even weak substorms, having the distinguished intensities, lead to the appearance of different types of irregularities observed by the CUTLASS radar and therefore to the different propagation modes and F2MOF values. (3) The PGI model of the ionosphere was first used for ray-tracing at high latitudes. The model results are basically in a good qualitative agreement with experimental observations. This model provides the satisfactory agreement between the calculated and experimental F2MOF values while not correctly representing the fine structure of the experimental OIS ionograms at night. An agreement between the calculated and experimental data is better for day and evening hours than at night. [Copyright &y& Elsevier]