The possibility of controlling the motion of a solar sail in a vicinity of a collinear libration point of the Sun–Earth system is investigated. An approach is proposed to constructing laws for controlling the orbital motion of a solar sail in the vicinity of a collinear libration point using nonlinear links of “output signal limitation” type. The approach is based on the use of a stable invariant manifold and elements of the theory of automatic regulation. It allows controllers to be constructed for the task of solar-sail keeping near the libration point. The control is implemented in two cases: changing the orientation of the sail or changing its reflectivity. Numerical examples with the solar sail model from the IKAROS project (2010) are considered.
The isotopic composition of water is an important indicator of its quality and determines its suitability for human use in space missions. The features of the infrared (IR) spectra in the middle region of various isotopic forms of water (–OH, –OD, H2O, HDO, and D2O) included in the crystal structure and adsorbed on the surface of the main rock-forming mineral of the lunar crust, anorthite, are considered. The results of numerical simulation of the main molecule’ vibrations using the ALT/CUSTEP module (Biovea Materials Studio) and experimental studies using an FT-801 IR Fourier spectrometer (Simex, Novosibirsk), as well as an inVia Reflex Raman spectrometer (Renishaw, United Kingdom), are presented. Numerical calculations of the lattice stability have shown that anorthite can contain both hydroxyl groups –OH(D) and molecular water H(D)2O in its crystal structure. The possibility of retaining various isotopic forms of molecular water by anorthite has been experimentally verified, and the corresponding mid-IR spectra of mineral grains with an aqueous film have been obtained. The presence of “light” isotopic forms of water on the lunar surface is confirmed by data from the SOFIA Stratospheric Infrared Observatory (NASA/GAS), but additional research will be required to detect “heavy” water.
The paper presents the results of experiments on board the Avion 6U CubeSat satellite to observe the effects of space weather, hard X-rays and gamma radiation from solar flares and cosmic gamma-ray bursts. The structure and main parameters of the Avion spacecraft, its onboard systems and payload are considered. New data on the dynamics of subrelativistic electron fluxes in the areas of precipitation from the inner and outer belts, as well as the results of observations of processes leading to a significant change in radiation conditions in the near-Earth space are analyzed. In particular, such phenomena include changes in the spatial structure of the distribution of subrelativistic electron fluxes in the outer belt due to magnetic storms and the penetration of solar cosmic rays into the polar cap regions, leading to a significant restructuring of radiation fields in the inner magnetosphere. Examples of detecting bursts of hard X-ray and gamma radiation from solar flares and cosmic gamma-ray bursts are given.
Dynamics of two passively gravitating small bodies of equal mass (planets or asteroids) in the gravitational field of two main bodies (stars) is studied. Stars of equal mass move in a circular orbit with the center at the origin, small bodies are mutually attracted and move in the plane of stars. Relative equilibria of small bodies have been found, and it is shown that all of them are unstable. Internal motions of the system are considered. They are determined by the fact that the center of mass of small bodies always coincides with the origin, and small bodies are so close to each other that gravitational forces between them exceed the gravitational forces from the stars. Equations in Keplerian osculating elements describing the perturbed motion of small bodies are written down. They are reduced to a dimensionless form and then averaged. An explicit formula for the averaged perturbation function is obtained. Bifurcations of phase portrait of the averaged system are investigated.
A lunar eclipse occurs on the Earth orbiting satellite when the Sun, Moon and the satellite are aligned in such a way that shadow of the Moon falls on the satellite. In 2015, Srivastava et al. (2015) extended the well-known Earth shadow models: projection map and line of intersection models for predicting the lunar shadow eclipses of the Earth orbiting satellites. In this paper, we extend other existing available Earth conical shadow models such as algorithm 34 of Vallado (2013), Wertz (2002), and Hubaux (2012) for the lunar shadow eclipses of the Earth orbiting satellites. The extended lunar shadow models are simulated on Indian LEO and GEO satellites: Oceansat-2 and INSAT-4CR. Further, an assessment of the extended models is studied with the lunar shadow model given by Escobal and Robertson (1967) and commercial software package, Systems Tool Kit (STK) of Ansys Inc.
This paper studies the accuracy characteristics of algorithms for the flexible spacecraft structural elements oscillatory motion determination using various sensor sets. The spacecraft body is considered as a rigid body to which flexible elements are attached using cantilever fastenings. Algorithms based on the nonlinear least-squares method for model parameters identification are developed, as well as algorithms based on the extended Kalman filter for real-time estimation of the state vector, which includes the parameters of the angular motion of the spacecraft body, as well as current deviations of the equilibrium position of flexible elements and their velocities in normal coordinates for a set of modes with the lowest frequencies. For flexible motion estimation, the use of a number of measurement sources is considered: attitude sensors mounted on the spacecraft body; accelerometers attached to non-rigid structural elements; and measurements obtained as a result of processing video images from a camera mounted on the satellite body, whose field of view includes the flexible structural elements. The paper provides a comparative analysis of the algorithms' performance using various measurement sources.
An important task and logical conclusion of the work of the ground–space project RadioAstron was the creation of a complete Project Data Archive, which ensures storage and organized access to all scientific and service information obtained during the experiment. The data archive is unique and allows reprocessing of data when new ideas and calculation algorithms appear. The data archive includes a database that allows one to navigate this information and to carry out selection and statistical studies. This article describes the information content of the RadioAstron Project Data Archive and hardware and software complex. The web interface allows the researcher to interact with the database. The web interface includes several sections and allows one to create one’s own pages for user requests. The data archive is a developing system, which in the future may become part of the Space Missions Data Center.
A method has been developed for analytical determination of the conditions of long-term retention in the Earth’s vicinity and the areas of spatial localization of artificial nanoparticles with sizes of the order of 10 nm, which are the products of degradation of the surface material of a large orbital object (a so-called “parent body” (PB)) moving in the Earth’s magnetosphere along a high circular orbit. The method is based on the construction of so-called “allowed” regions of motion of nanoparticles separating from the PB surface at different points of its orbit using the generalized Störmer method. Using this method, the possibility of capturing aluminum oxide nanoparticles with a radius of 10 nm by the Earth’s magnetic-gravity trap under conditions of average geomagnetic activity was shown in the case of their insertion into near-Earth space on circular orbits with heights from 50 000 to 60 000 km and small inclination angles to the equatorial plane.
Interplanetary flights are considered in which a spacecraft performs two successive flybys of a single planet. The trajectory of the spacecraft before and after such a double gravity assist maneuver is considered given. It is also assumed that, between flybys of the planet, the spacecraft moves along a passive trajectory and that during the flybys active maneuvers are possible. The requirements that the trajectory between flybys must satisfy are determined. In cases in which such a trajectory is not the only one, a method for its optimization (i.e., minimization of the total impulse) is indicated.
During magnetospheric perturbations a relatively thin current sheet with thickness about several proton gyroradii forms in the Earth’s magnetotail. In a framework of the kinetic model describing current sheet thinning in the magnetotail, the processes of its formation are investigated depending on the normal magnetic field magnitude which affects both the current sheet structure and particle dynamics within it. The critical value of the ratio of the normal to tangential components magnitudes at current sheet edges is determined above which the formation of a stationary thin current sheet does not occur. The reason for this is the high density of trapped plasma particles around the sheet, which contribute to its magnetotail structure and finally lead to its destruction. It is shown that this ratio can be the important factor influencing quasi-equilibrium state of magnetotail current sheet as a whole and determining the characteristic parameter range at which the formation of a long-lived current structure with small thickness is possible.
A new method for recording and analyzing variations in the structure of the interplanetary magnetic field is considered. It is based on the synthesis of 3D profiles of three mutually orthogonal projections of the matrix of the number of state realizations constructed in the GSE coordinate system. Spatial statistical moments of lower and higher orders are considered, which make it possible to separate the drift of projection centers, the variation of diffusion characteristics relative to the centroid axes, and multimodal realizations in the observation time interval. The monitoring data set is based on experimental samples from the WIND apparatus for four significant 18-day time intervals in January, August, September, and October 2024. A detailed analysis of the observed variation in the second spatial statistical moments is carried out using the cubic spline interpolation method. The high information capacity of the proposed method makes it possible to control a wide range of central spatial statistical moments realized in the system and to create secondary kinematic parameters of the processes under study. The proposed set of primary metrics for analyzing the structure of distortions based on moments from the first to the fourth order allows creating signatures for recognizing the type of observed distortions of the interplanetary magnetic field, detecting transient processes in the heliosphere generated by solar activity.
The purpose of this work was to find out why not all type II bursts, usually observed in the meter wavelength range, switch to the longer wavelength range (decameter, hectometer, and kilometer). Most of the statistical work only partially addressed this issue. Many authors assumed that all shock waves are of the piston type and only high-frequency type II bursts can be associated with explosive shock waves that fade before they reach interplanetary space. At the same time, the authors did not take into account the mechanism of radio emission generation. In this paper, a number of type II bursts are considered and it is established that the conditions for generation are preserved if the shock front has no obstacles to propagation at the boundary of the transition from frequencies around 20 MHz to a range less than 14–16 MHz, and the radiation can already be detected by spectrometers of the WIND/WAVES and STEREO spacecraft. Bursts can be generated in separate sections of the shock front, where certain conditions are met: exceeding the critical Mach number and the perpendicular of the shock front. Such conditions may also explain the patchy structure of type II radiation bands. These conclusions are in good agreement with the conditions for the development of the Buneman instability of particles in the front of a collisionless shock wave. It is also important to take into account the interaction of the shock front with the coronal mass ejection.
The paper is dedicated to the study of sidereal-diurnal variations of galactic cosmic ray intensity. The existence of such variations is due to a combination of a number of factors, the main ones being the asymmetry of the heliosphere structure and the anisotropy of the spatial-angular distribution of galactic cosmic rays in the interstellar medium. The characteristics of stellar-diurnal variations observed on Earth can be conditionally divided into two energy regions: for cosmic ray energies above TeV, the observed stellar-diurnal variations have an amplitude and maximum time of about 0.1
We analyze the dynamics of solar energetic particles during the extreme solar activity interval of May 8–11, 2024, when a large number of M- and X-ray flares accompanied by several halo-type coronal mass ejections (CMEs) were observed on the Sun in the active region 13664. The propagation of solar protons occurred against the background of a strongly disturbed interplanetary medium. A comparison the time profile of particle fluxes measured at the Earth’s orbit and in the vicinity of the L1 libration point made it possible to identify some characteristic features associated with the generation of particles near the Sun and with the modulation of particle fluxes by solar wind structures. The paper discusses a slow increase in proton fluxes during the interval of May 8–10, which can be associated with three stages of acceleration: (1) on the shock wave in front of a CME; (2) during the approach of the fast CME to the slow one; and (3) on the shock wave propagating inside the interplanetary CME. The influence of shock waves observed near the Earth on proton fluxes on May 10 is shown. It is found that accelerated protons can accumulate inside magnetic clouds of interplanetary CME. We also studied a solar proton event (SPE) of May 11, 2024, when an SPE ground level enhancement was observed—GLE 74, which was caused by protons with E > 1 GeV. It is shown that a dispersionless enhancement at the beginning of the SPE can be explained by the modulation of proton fluxes by a tube-type structure bounded by two magnetic clouds and connected to the acceleration region on the Sun.
To perform station keeping of a platform connected by a massless extra-long tethered sailcraft with respect to (w.r.t.) the Earth in the Sun–Earth system enables envisaged space missions. The position of the platform could be balanced and controlled exploiting the nature of the dumbbell tethered system in the three-body dynamical environment by placing the platform and sailcraft with modulatable lightness number within and beyond the Sun–Earth L1 point respectively. This propulsionless scheme merely utilizing surrounding gravitational environment and modulatable solar pressure for station keeping is worth exploring. In this work, nonlinear dynamics considering positions of the platform and sailcraft along the Sun–Earth line is established in the Sun–Earth elliptical restricted three-body system (SEER3BS). Equilibria of the tethered system are analyzed parametrically as a reference for parameter selection for performing closed-loop dynamic analysis. Sliding mode control scheme is applied to station keeping of the platform. The tether’s tension is a force directly applied to the platform, and is determined by the platform-sail distance, which is adjustable by varying the sailcraft’s lightness number. Transient and steady-state dynamic responses of closed-loop system are investigated respectively. Specific time histories of physical variables such as the Earth-platform and Earth-sail distances, the elastic elongation, tension and strain of the tether, and the sailcraft’s lightness number, are presented to verify the effectiveness of the controller. Moreover, influences of the system’s dimensionless circular frequency on transient dynamic responses are studied as an example to show the existence of feasible/infeasible parameter ranges. Furtherly, envelopes of elastic tensions and strains, the Earth-sail distance, and the required lightness number are given in steady-state closed-loop dynamic responses. Influences of parameters such as the platform’s mass, the dimensionless circular frequency, the natural length of the tether, and the Earth-platform distance on the envelopes of the preceding physical variables are explored to give the feasible parameter ranges in a comprehensive manner. The corresponding discussion and suggestions on parameter selection are also given.
As a part of the Ionosonde-2025 satellite system development for space weather monitoring, LAERT topside ionosondes were installed onboard the four Ionosphere-M satellites. The devices can operate in several modes, including the passive mode, as an HF radio spectrometer in the 0.1–20 MHz frequency band, and the active sounding mode. During sounding sessions, the radio noise intensity at every frequency is measured before and after the pulse emission. It allows determination of the characteristic frequencies and excitation levels of plasma waves in the undisturbed conditions as well as in the environment, excited by the ionosonde. Thus, in addition to the sounding mode, the device operates in the relaxation sounder mode. This mode has been used on a number of foreign satellites in the ionosphere and magnetosphere (for example, the Whisper instrument on the Cluster satellites). In addition to emission at the characteristic frequencies of the surrounding plasma, the Ionosphere-M satellites recorded signals from external sources: solar radio bursts and signals from ground-based radio transmitters penetrating the ionosphere at frequencies above the ionospheric critical frequency foF2. In addition, the devices observed emissions in the whistler range (f < fhe) and upper hybrid range (fpe ≤ f ≤ fuh), generated by the beams of energetic electrons in the auroral region (fhe is gyrofrequency, fpe – the electron plasma frequency and fuh – the upper hybrid frequency). This provides an opportunity to monitor the position of the auroral oval and its dynamics. Monitoring the local plasma frequency along the satellite’s orbit provides global electron density maps at an altitude of approximately 820 km.
This study presents a numerical simulation of the interaction of protons (2–200 MeV) and electrons (50 keV–5 MeV) with the KODIZ-2 (Combined Radiation Detector) system using the Geant4 environment. A simplified detector model was developed for simulation purposes, and a series of computational experiments were conducted using an isotropic particle distribution. The threshold energies for proton (3.1 MeV) and electron (300 keV) detection were determined, along with the characteristics of their energy losses in the detector system. The study demonstrates that the differences in the responses of silicon detectors and scintillators enable effective particle classification and separation of proton and electron fluxes. A method for separating particles in the detector response space by constructing a dividing surface is proposed, which makes it possible to achieve 99.81
Compact instruments on nanosatellites provide a valuable alternative to large heliophysical observatories, enabling rapid replacement of nonfunctional facilities and low-cost testing of new technologies. At the same time, development of imaging instruments for nanosatellite platforms involves specific technical challenges. This paper discusses the general operating principles of extreme ultraviolet (EUV) solar telescopes, the main challenges associated with their miniaturization, and potential design solutions, demonstrating the feasibility of their practical implementation by the example of a small-sized coronagraph telescope and a high-resolution telescope. One of the instruments described—the SOL EUV coronagraph—became the first imaging instrument for solar observations deployed on a nanosatellite. The paper provides a detailed description of its design and presents the results of in-orbit testing on the NORBY-2 nanosatellite, as well as discusses the prospects for its further application and the scientific significance of the data it can provide.
A calculation is performed of ion-velocity and energy-distribution functions in plasma occupied by ion-acoustic compressive and rarefactive solitons. The pseudopotential method and ergodic hypothesis are used. A two-electron model of plasma with cold ions is considered. Formulas valid for arbitrary amplitude are obtained. It is shown that the perturbed distribution functions have a beamlike form. The results are compared with previously obtained analytical calculations and modeling results.
The present work was to figure out whether intense current structures are formed in the quiet Plasma Sheet (PS) of the Earth’s magnetotail, or whether they are observed only in the presence of Bursty Bulk Flows (BBFs). We had statistically analyzed absolute value of electric current density | 𝐣| , the magnitude of the nonideal electric field ( 𝐄 1pt ' = 𝐄 + [ 𝐯_e×𝐁] , where 𝐯_e is electron bulk velocity, 𝐁 and 𝐄 are magnetic and observed electric fields, respectively) and the energy conversion rate ( 𝐣·𝐄 1pt ') observed by MMS spacecraft in 19 quite (the X-component of the ion bulk velocity | 𝐯_i,x| < 200 km/s) and 23 active (peak value of | 𝐯_i,x| in each interval reaches at least 500 km/s) intervals. All observations were made in the midnight sector of the magnetotail ( | Y_GSE| ⩽ 13 R_E ) and within the Sun–Earth direction range X ≈ - (15 -28) R_E . It is shown that intense current structures with current density | 𝐣| > 30 nA/m2 are observed only within the BBFs and are absent in the PS during quite intervals. The probability density distributions of | 𝐄 1pt '| , | 𝐄_||^'| and 𝐣·𝐄 1pt ' , 𝐣_||·𝐄_||^' demonstrate similar behavior. Thus, during the quiet intervals, the typical values of | 𝐄'| , | 𝐄_||'| , and the parameters 𝐣·𝐄 1pt ' and 𝐣_||·𝐄_||^' do not exceed a few mV/m and tens of pW/m3, respectively. On the other hand, during the active intervals, | 𝐄 1pt '| and | 𝐄_||^'| can exceed 10 mV/m, and the parameters | 𝐣·𝐄 1pt '| and | 𝐣_||·𝐄_||^'| can exceed 100 pW/m3.
