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Vol 61, No 4 (2023)
Articles
Оценки параметров западного аврорального электроджета во время сильных суббурь
Abstract
Продолжается разработка простой “прямоугольной” модели западного аврорального электроджета, основанной на наблюдениях магнитного поля вдоль разреженной меридиональной цепи станций в полярной зоне. Модель имеет три параметра: две границы и постоянную плотность электрического тока. Работа модели показана на примере суббурь, наблюдаемых на цепочке станций CARISMA (англ. Canadian Array for Realtime Investigations of Magnetic Activity). Был введен дополнительный параметр, позволяющий менять меридиональный профиль тока от прямоугольного к колоколообразному, но его влияние на работу модели оказалось слабым. В заключение проведено сравнение оценок полной силы электроджета, полученных по этой модели, с оценками суббуревого токового клина, полученными по среднеширотным станциям. Обе оценки имеют схожие амплитуды и изменяются согласованно в течение развития взрывной фазы суббури. Величины тока в определенные моменты времени могут различаться в два раза, но схожие различия наблюдаются и для других моделей западного аврорального электроджета. Последнее предполагает, что реальная геометрия тока электроджета и тока клина могут значительно отличаться от используемых относительно простых моделей.
267-276
Simultaneous Ground and Satellite Measurements of the Polarization Jet at the Yakutsk Station Meridian
Abstract
The data of simultaneous measurements of the polarization jet from the Yakutsk ground-based vertical radio sounding station and satellite observations of narrow electron density dips or fast westward drifts of the ionospheric plasma from satellites of the Defense Meteorological Satellite Program (DMSP) series. The events are based on ground-based ionospheric measurements and cover the time interval from March 1989 to December 2015, i.e. about 26 years. The simultaneity of observations is ensured by a time period of approximately ±1.5 h from the time of registration of signs of a polarization jet according to the data of a ground-based ionospheric sounding station or by the an orbital period of DMSP satellites around the Earth. Based on data of long-term simultaneous satellite and ground-based measurements (126 events), it was shown and confirmed that the presence of characteristic additional traces of reflections on ionograms indicates the presence of narrow and fast drifts of ionospheric plasma or a polarization jet near the zenith of the observation station. It is also shown that the quasi-instantaneous longitude extent of a polarization jet at subauroral latitudes can in some cases reach 8 h or 120° by longitude.
277-284
Time Series of Space Observations: Analysis of Local Meteorological and Solar Series
Abstract
A range of issues related to the results of the analysis of some meteorological and solar series of satellite observations in the Kara-Dag area (Crimea) is considered. A qualitative and quantitative picture of changes in the total insolation falling on the Earth’s surface, air temperature at a height of 2 m, and the Earth’s surface temperature in Kara-Dag over the past 38 years is presented. A numerical model has been constructed that makes it possible to predict the most powerful fluctuation with a period of 1 year in the analyzed data. The following methods were used in the work: the method of wavelet analysis, statistical methods for extracting Gaussian and non-Gaussian noise, an iterative method for constructing and estimating the accuracy of model approximations. Coherent variations in the analyzed and some global geodynamic and solar time series were established using two-channel autoregressive analysis. A qualitative characteristic of the process of changing the main variations in the analyzed time series was obtained using the analysis of phase trajectories on the Poincaré plane.
285-301
On Libration Points in the Asteroid–Research Probe System
Abstract
This paper is dedicated to a study of relative motion in the field of homogeneous spheroid bodies. It is assumed that an asteroid’s satellite does not affect its translational and rotational motion by inertia. The latter motion has the form of rotation in the mode of regular precession. The case in which the asteroid is an ellipsoid of revolution is considered. A system of conditions that the libration points must satisfy is constructed; it is shown that its solution is two types of libration points, which differ in their location with respect to the constant vector of the angular momentum and the axis of symmetry of the ellipsoid. Thereafter, the stability of libration points is investigated numerically and analytically in the first approximation.
302-310
A Lunar Printer Experiment on Laser Fusion of the Lunar Regolith in the Luna-Grunt Space Project
Abstract
This paper presents the results of laboratory studies on the use of a new technology of selective laser melting to obtain experimental products from the lunar regolith without special additives. The main properties of the natural regolith, which significantly affect the fusion process, are determined. The first samples of a given geometry were obtained from labradorite and gabbro-diabase powders, which are natural analogues of lunar regolith, using this technology. The research results are planned to be used in the preparation of initial data for the development of the Lunar Printer space device as part of the complex of scientific equipment of the promising lunar project Luna-Grunt.
311-321
Predicting the Parameters of the Orientation of the Earth in Problems of Navigation Taking into Account the Phenomenon of the Development of Irregularity in the Earth’s Rotation
Abstract
This article discusses the application of a previously proposed [1] methodology for predicting the Earth’s orientation parameters (EOPs) that provides high accuracy as a result of optimizing a special procedure of processing historical data using the least-mean-squares method. The results of investigating the accuracy characteristics of the obtained EOP estimations are presented in relation with a predictive task in the interval from 2019 to 2022, when, for the first time in the history of observing the Earth’s daily rotation, a change was recorded in the difference trend between Universal Time and Coordinated Universal Time was recorded, caused by the length of day decreasing. The influence of the length of the day trend changing and related problems on the accuracy of EOP prediction in various navigation tasks using classical polynomials describing EOP evolution is discussed. A comparative analysis of the EOP prediction made by the International Earth Rotation and Reference Systems Service for a similar time period is carried out.
322-331
The Effect of Products Released from the Structural Materials of a Spacecraft on the Optical Properties of Its Thermal Control Coatings
Abstract
In this paper, we report on our experimental findings regarding the release of easily condensing substances from certain structural materials utilized in spacecraft, and we evaluate the impact of thin condensate films on the integral optical coefficients of external thermal control coatings (TCCs) of spacecraft. To simulate the space environment and solar radiation, the experiments were conducted in a vacuum. We found that the flux densities of the components released from the materials’ surfaces reach 5.4 × 10–7 g cm–2 s–1 and exhibit an exponential decrease over time. Furthermore, thin condensate films with a thickness of 100 Å can significantly degrade the integral optical coefficients of TCCs by tens of percent. These effects can alter the heat balance of the spacecraft. The experimental research methods used in this study can be applied to a broad range of materials, and the results have implications for the design and construction of various types of spacecraft.
332-338
A Study of the Motion of Four Linked Satellites Controlled Using Lorentz Forces
Abstract
This paper considers four satellites connected to each other by electrodynamic tethers, which are assumed to be rigid in the mathematical model of the system’s motion. In the Earth’s magnetic field, current-carrying conductors are affected by Lorentz forces, which are used to control the motion of the system’s center of mass and the angular motion. The paper presents an algorithm for calculating the magnitude of the current to stop the drift of the center of mass of a tetrahedral formation relative to the desired orbital reference frame in low Earth orbit and spin the system up to a constant angular velocity relative to the center of mass. A numerical study of the convergence time to achieve the required motion is carried out depending on the maximum possible current and initial conditions.
339-352