near-Earth Space Research Articles

Progress and Enlightenment of Intelligent On-orbit Operation of International Space Station

The mission of a space station that is known as the big platform of near-earth space is to enable long-term flight to explore space. As the ever-increasing number of on-orbit missions, it is a challenge to manage an effective on-orbit project. With the deep integration of artificial intelligence and space technology, the on-orbit operation of a space station has gradually developed to be intelligent. Therefore, the intelligent operation of spacecraft has become an inevitable trend. This paper focuses on the development of on-orbit intellectualization at the International Space Station (ISS) and the application of artificial intelligence technology in its health management, mission planning and scheduling, mission operation and human-computer interaction. It is hoped that the research will contribute to the intelligent on-orbit operation in China.

Method of forming a rational set of test trajectory options to increase the reliability of performance evaluation during testing of radar information tools

To get an objective picture of the state of near-earth space, it is necessary to update the fleet of information tools in a timely manner, which is characterized by the introduction of new tools and the modernization of old tools, while changing the system in stages as the funds are ready. The continuous build-up of the system's assets as they are ready allows us to improve its performance without waiting for all newly introduced and upgraded assets to be ready. To test monitoring systems in conditions of a large number of heterogeneous elements combined in a system to achieve a single goal, an experimental and theoretical method of evaluating effectiveness based on mathematical modeling is used. The essence of this method is to simulate information at the input of programs of the system tools using mathematical models implemented directly on the system tools themselves. In this case, the quality of test trajectories that would allow evaluating the characteristics of radar information tools and the capabilities of monitoring systems is of particular importance. The purpose of the study is to increase the reliability of the results of tests of radar information tools for monitoring space debris by selecting a rational set of trajectory options that allow for the worst possible implementation of the capabilities of radar information tools, taking into account the functioning of each specific radar information tool participating in the tests. Based on the features of the factor space for finding solutions to the problem of forming test trajectories, the algorithm for forming the initial population and the algorithm for generating a new generation should be supplemented with blocks for checking the observability and feasibility of trajectories. The developed method of forming a rational set of variants of test trajectories using genetic algorithms differs from the known ones in that it generates a set of variants of test trajectories optimized from the point of view of obtaining the worst implementations of the capabilities of radar systems during its testing, under conditions of restrictions on the feasibility and observability of trajectories, the application of the methodology allows automating the process of preparing initial data for testing space debris monitoring systems in order to evaluate their characteristics. The application of the developed method allows to obtain the maximum errors in determining the parameters of the trajectory of space debris elements.

The Speed of Movement of Artificial Space Objects and Its Determination Using Incoherent Scatter Radar

Methodological features of registration and separation of coherent radar reflections from space objects and elements of “space debris” operating in orbit are considered. Registration occurs against the background of signals that are scattering of the probe radio wave on particles of the ionospheric plasma. Methods of how to obtain information about the components of the velocity vector of these objects in near-earth space with the help of specialized ground-based radar facilities are analyzed. Their disadvantage is the unreliable control of weak reflections from the elements of “space debris” if they have a small (up to centimeters) scattering cross section. The authors proposed to use the existing high-energy radar installations. Using the signals after the analog-to-digital conversion generated in quadrature, it is proposed to calculate the phase characteristics of the coherent reflection. The radial velocity of the objects along the radar beam is calculated by isolating the Doppler phase difference and statistically averaging these values ​​in the time of reflection. Similarly, by analyzing the time spent in the radar beam, the velocity component associated with the horizontal movement along the Earth’s surface is calculated. Real examples are given, when in one of the observation sessions on the reflection of a signal from a space object, the phase shift in each of its periods is calculated, and then, using the formula, proposed by the authors, the vertical component of the velocity of this object is calculated. Analyzing the observation time of this object in the beam of the transmitter antenna, an example of the calculation and the component of its horizontal velocity is shown. The block diagram of the radar used to calculate the specified parameters of the movement of space objects is presented. The developed approach is an effective solution of many practical problems in those industries that ensure the operation of spacecraft, ensuring the safety of space stations, optimal placement of objects in orbit, etc. Keywords: Incoherent scatter radar, space objects, coherent reflection, signal phase characteristics, radial and horizontal speed

Investigation of the ionosphere over Antarctica under quiet space weather conditions: results of vertical sounding of the ionosphere September 14–24, 2020

We present observational results of variations in the ionospheric parameters hmF2 and NmF2 over the Ukrainian Antarctic station “Akademik Vernadsky” for magnetically quiet conditions. The results of comparative analysis of observational data and the International Reference Ionosphere-2016 model predictions are presented. The main objective of this study is to investigate the temporal variations of two key ionospheric parameters – the F2 layer peak height and electron density – during very quiet space weather conditions using data of vertical sounding of the ionosphere obtained over the Ukrainian Antarctic station “Akademik Vernadsky” and comparison the observation results with model values. Methods: The temporal variations of the F2 layer peak height and electron density were calculated from ionograms obtained with ionosonde installed at the Ukrainian Antarctic station “Akademik Vernadsky” with subsequent electron density profile inversion. Diurnal variations of hmF2 and NmF2 were calculated using a set of sub-models of the IRI-2016 model for comparison with results of observational studies. Results: We found that for the Antarctic region option of IRI-2016 model for the F2 layer peak height SHU-2015 provides a better fit for hmF2 through the investigated period compare to the AMTB-2013 model predictions. Electron density models (URSI, CCIR) generally well reproduce the observed variations of NmF2 during periods of absence non-standard manifestations of space weather, which are possible for quiet conditions too. Hypotheses regarding the possible reasons for experimental and model differences in variations of NmF2 are discussed. The analysis of effect of geomagnetic storm on September 24, 2020 on NmF2 variations was carried out. Conclusions: The obtained results demonstrate peculiarities of the state of the ionosphere-plasmasphere system over Antarctica under very quiet space weather conditions and provide evaluation of predictive capabilities of modern international reference ionosphere models. New knowledge about the features of electron density variations in the ionosphere for magnetically quiet conditions over the Antarctic region has practical value for specialists which are engaged in the study of the near-Earth space environment, in particular, at high latitudes, and also work on correction of global ionospheric models. Keywords: electron density, F2 layer peak height, ionosonde, quiet space weather, models of the ionosphere, downward plasma flux

Comparative analysis of global optical observability of satellites in LEO

With a growing number of resident space objects (RSOs), the facilities for near-Earth space surveillance have to cope with increasing workload. It also applies to low-cost small optical surveillance facilities which may present regional, national and global networks. Improved methods of planning and scheduling optical telescopes are required to use these instruments efficiently. Today, optical observations are only feasible if the following quite stringent requirements are met: the object should be illuminated by sunlight, and it should be above while the Sun is below the observer’s horizon. For different orbits, these preconditions result in varying degrees of the space object observability at various ground-based sites. Certainly, satellites in low Earth orbit (LEO) are particularly difficult to observe. This study aims at developing a new technique for assessing observability of a satellite in different types of orbits – namely, low, medium and high Earth orbits, imaging of the opportunity for its visibility in respective diagrams and their analysing for the existing near-Earth population of RSOs. Unlike other researches, wherein one or several observational stations have been chosen as target sites for in-depth analyses of visibility of all the satellites or just the selected ones, the present study focuses on examining the probability of optical surveillance of satellites in a certain orbit from any locations worldwide. It offers considerable scope for automation of surveillance planning and scheduling optical surveillance networks.

Experimental development onboard the ISS Russian segment of the prototype system for quick localization of a puncture in the space station pressure shell

Improving safety of space station operations at the time when the near-Earth space is getting increasingly littered with space junk is one of the principal problems in space station design. Along with the measures to reduce the risk of the station pressure shell penetration resulting from a collision with a meteoroid or a piece of space debris that involve protection of the module pressure shells with shields, there is also a need for developing measures and equipment aimed at mitigating catastrophic consequences of the penetration. One of the key factors allowing successful recovery from an emergency situation caused by station depressurization in case of a puncture is the time needed to locate the puncture, which determines possible scenarios for crew actions during recovery operations and their result. The Immediate Puncture Localization System (IPLS) presented in this paper provides reliable and virtually immediate detection of the time and location of the penetration. The proposed concept for the IPLS architecture is based on the use of piezoelectric sensors of acoustic emissions distributed over the inner surface of the pressurized shell of the module that are connected to an electronic unit for processing signals from the sensors. The paper presents the results of studies of the scientific and engineering feasibility of the IPLS operating principles conducted at RSC Energia and TsNIIMash, as well as results of developmental tests on a prototype of such a system in the Service Module of the International Space Station (ISS) in the space experiment Otklik conducted under the Applied Research Program of the ISS Russian Segment. Key words: International space station, ISS Russian Segment, meteoroid, space debris, pressure shell, immediate puncture localization system, piezoelectric sensor, space experiment, high-velocity impact, penetration.

ON THE CHARACTER OF AN ARTIFICIAL SATELLITE DRAG UNDER VARIOUS STATES OF SOLAR AND GEOMAGNETIC ACTIVITY

Purpose: The artificial satellites drag in the atmosphere remains an urgent problem to date. In this work, the artificial satellites data are used in order to study the atmosphere state under various manifestations of solar and geomagnetic activity. The selected satelites were moving uncontrollable being good indicators of the upper atmosphere state. The B-star (drag term) drag coefficient is used in this work. This term is used in the SGP and SDP models to take into account the resistance of the atmosphere to the satelite orbital motion. The data of the drag of two artificial satellites, one moving in elliptical and the other in circular orbits at midlatitudes (orbital plane angles of 58°-60°) were considered. These data include the end of the 23rd solar activity cycle, as well as the growth, the maximum and the decay phases of the 24th solar cycle (years 2005–2017). Seven periods of anomalous drag of the satellites were analyzed. They are: 4 monthly periods (two in 2005 and two in 2011) and 3 yearly periods (within 19.07.2014 to 22.08.2015), five-year long (2005–2010) and six-year long (2011–2017) periods. Design/methodology/approach: The periodogram analysis was made. This allowed to reveal the periodic processes in changes in the state of the atmosphere of different duration. The correlation coefficients of the B-star drag term with the indices of solar and geomagnetic activity were calculated. The analysis of extreme drag of the satellites in the periods of the increased solar and geomagnetic activity (intervals of observation lasting a month) was made. Findings: Using the solar and geomagnetic data we found that some month-long part of the anomalous drag periods were followed by flares on the Sun and the arrival of the coronal mass ejections into the near-Earth space. At time intervals of yearlong observations the highest values (0.5-0.7) were obtained for the coefficients of the B-star parameter correlation with the solar activity indices – solar radiation at the wavelength of 10.7 cm, F10.7, and Lyman alpha radiation, Lα. At monthly time intervals, the largest values of the correlation coefficients were obtained for the B-stars with the electron fluxes with energies above 0.6 and 2 MeV, E, (0.3-0.5), the Lyman alpha radiation, Lα, (0.58–0.73 for a сircular orbit satellite), and the solar constant, TSI, (0.3–0.6), as well as the geomagnetic storms intensity index, Dst , (0.66–0.69). Periodogram calculations show the presence of a whole spectrum of periods in the deceleration of a circular orbit satellite and a dedicated period for an elliptical orbit satellite. Conclusions: The B-star drag term dependences on the indices of solar and geomagnetic activity during some periods of their intensification for the 23–24 cycles of solar activity are considered. The periodogram analysis made together with the analysis of the conditions and parameters of space weather allows to see the general and more detailed picture of the solar and geomagnetic activity influence on the change in the motion of the satellite in the atmosphere. The B-star drag term helps to consider only the atmosphere influence on the artificial satellite movement in the near-Earth space. Key words: artificial satellite, atmosphere, artificial satellite drag, solar activity, geomagnetic activity, space weather

Equivalent Flux Function Smoothing in the Problem of Solar Cells Radiation Degradation Minimization During a Low-Thrust Geostationary Orbit Insertion

The paper describes a modified smooth approximation method for smoothing the dependence of the equivalent fluence of charged particles of the Earth’s Van Allen radiation belts on time and position in near-Earth space. It is shown that this method can be effectively used to solve the problems of minimizing radiation-induced degradation of spacecraft solar cell arrays. The latter problems involve the variation of the trajectory that the spacecraft follows during an electric propulsion transfer from an initial orbit to a geostationary one.

Analysis of the Karma asteroid family

ABSTRACTThe Karma asteroid family is a group of primitive asteroids in the middle part of the main belt, just at the outer edge of the 3J:1A mean-motion resonance. We obtained the list of the family members with 317 asteroids, and estimated that it was formed by the catastrophic disruption of a parent body that was between 34 and 41 km in diameter. Based on the V-shape method, age of the Karma family is estimated to be about 137 Myr. A detailed dynamical map of the region combined with numerical simulations allowed us to reconstruct the long-term dynamical evolution of the family, and to identify the mechanisms responsible for this evolution. The numerical simulations successfully reproduced the main features in the orbital distribution of the family members but also showed that some regions of the Karma family could be missing. A more detailed analysis revealed that these regions likely consist of very dark objects, fainter than absolute magnitude H = 17, that have not yet been detected. Based on the obtained results, we concluded that magnitude–frequency distribution of family members up to H = 16 mag is neither affected by dynamical erosion nor observational incompleteness, and therefore represents the result of collisional grinding of the original family population. Finally, we found that the Karma family have been supplying some asteroids to the near-Earth region via the 3J:1A resonance. Currently, there should about 10 family members larger than 1 km in diameter, orbiting in the near-Earth space.

Focusing plasma jets to achieve high current density: Feasibility and opportunities for applications in debris removal and space exploration

Rapid emergence of satellite-based economy coupled with the current renaissance in space exploration and aspirations for the Moon and Mars colonization drive strong interest in various techniques that may be adapted to space conditions and utilized for space debris disintegration and removal, as well as device maintenance and repair operations in open space. Dense plasma jets are a promising tool for many advanced applications. These can range from material processing to applying powerful effects of plasmas to targets to facilitate e.g. repair of material components in devices under field conditions or in space, as well as to enable destruction of objects for removal of debris from near-Earth space. Although there has been some effort in the use of strongly focused plasma jets in the aerospace technology, to date such a use is not widespread. In this work, we describe the experiments that demonstrate the possibility of focusing plasma jets into very high-current spots, where the current density reaches 5,000A×m−2 in a spot of about 5 mm. Depending on a specific configuration of focusing magnetic coils, the footprint of the focusing spot could be controlled over a wide range, from millimetres to centimetres, and the current density could be varied from hundreds to thousands A×m−2. We also briefly outline the possible applications of such systems, emphasising the possible use of such focused plasmas in space exploration technology. We expect that the suggested approach would be of considerable interest to many experts working in aerospace technology, and will stimulate new research directions in these fields.

Space-based pulse laser removal of near-earth small debris

The aim of this article is to reveal the dynamic response rules of removing near-earth small space debris using space-based pulse laser. A dynamic model of debris deorbit was established by space-based laser irradiation. For different area-mass ratio debris, the evolution process of debris deorbit was addressed in the process of orbital parameters with the number of laser pulses. The results indicated that the true anomaly, the major semi-axis of the debris and the action distance between the debris and the laser platform were gradually decreased with the increase of the number of laser pulses, but the eccentricity was rapidly increased with the increase of the number of laser pulses. Furthermore, the effect of debris deorbit was also analyzed when the debris entering into the best clearance windows. The optimal action angle was decreased with the increase of true anomaly, and the laser platform was within the available range of laser irradiation in the best window period. In a word, the results will provide efficient guidance to grasp the evolutionary process of clearance near-earth small debris by means of space-based pulse laser.

The impact of satellite constellations on space as an ancestral global commons

Near-Earth space is becoming increasingly privatized, with the number of satellites in low-Earth orbits predicted to grow dramatically from about 2,000 at present to over 100,000 in the next decade due to the launch of planned satellite constellations. In addition to their direct impact on astronomy, the manner and pace of ‘occupying’ near-Earth space raises the risk of repeating the mistakes of colonization on a cosmic scale. We must consider the impact of satellite constellations, and related future initiatives, on the essential human right to dark skies and on cultural sky traditions across all peoples. We must also include all stakeholders for near-Earth space in the process of developing new policies for space treaties and planetary protection, the consequences of which will reach far beyond this century. We advocate for a radical shift in the policy framework of international regulatory bodies towards the view of space as an ancestral global commons that contains the heritage and future of humanity’s scientific and cultural practices. In the context of near-Earth space becoming increasingly privatized and crowded due to the launch of satellite constellations, space must be viewed as an ancestral global commons that contains the heritage and future of humanity’s scientific and cultural practices.

Observation of Disturbed Plasma Structures in the Environment of the Sun and Near-Earth Space with Radio Sounding and Local Measurements

An experiment on radio sounding of the circumsolar plasma by signals from the Mars Express spacecraft in 2013 was carried out in the period from March 4 through May 31. The investigated characteristics were the frequency of signals in the centimeter and decimeter ranges and the differential frequency. A number of events were recorded in which the intensity of the frequency fluctuations of the signals probing the plasma was several times higher than the background values. As shown by the analysis of observations of solar activity, such as an increase in the flux of X-rays and SOHO LASCO coronagraph data, this is explained by the passage of disturbed plasma streams generated in the solar corona through the spacecraft radio communication path with the Earth. The comparison of the radio transmission data with the results of measurements of the parameters of the near-Earth plasma using the Wind spacecraft in adjacent periods of time. As a result of the analysis of the data on the proton concentration, it became clear that sharp increases in both the average values and fluctuations of this characteristic were also observed near the Earth. The time lag between the events observed in the circumsolar and near-Earth plasma shows that the cause of the disturbances is the increased activity of the same coronal region rotating with the Sun.

Launch Vehicle Rendezvous to Catalogued Orbital Debris while Injecting into Highly-Inclined Orbits

Introduction. A constant increase in the amount of space debris already constitutes a significant threat to satellites in nearEarth orbits, starting with the trajectory of their launch vehicle injection. Problem Statement. Design and development of various modern methods of protection against space debris requires knowledge of the statistical characteristics of the distribution of the kinematic parameters of the simultaneous motion of a launch vehicle injecting satellite and a group of space debris objects in the area of its trajectory. Purpose. Development of a mathematical model of a launch vehicle rendezvous with a group of observable orbital debris while injecting a satellite into near-earth orbits with an altitude of up to 2100 km and an inclination from 45 to 90 degrees. Materials and Methods. The following methods are used in the research: analysis, synthesis, comparison, simulation modeling, statistical processing of experimental results, approximation, correlation analysis, and the least squares method. Results. The simultaneous motion of a launch vehicle and a group of space debris objects has been studied. The distributions of relative distance, relative velocity, angle of encounter, and moments of time of approach of a launch vehicle to a group of the observed space debris at a relative distance of less than 5 km have been obtained. The dependence of the average rendezvous concentration on the distribution of space debris across the average altitude of the orbit and the inclination of the target orbit of the launch vehicle has been determined. The dependence of the average probability of rendezvous in the launch on the inclination of the target orbit, the number of orbital debris, and the relative distance of the rendezvous has been determined. Conclusions. The obtained mathematical model of rendezvous of a launch vehicle with a group of observed orbital debris can be used while designing means of cleaning the near-Earth space and systems to protect modern satellite launch vehicles from orbital debris. In addition, the results of the research can be used to assess the impact of unobserved orbital debris on the flight of a launch vehicle.

Bennu's near-Earth lifetime of 1.75 million years inferred from craters on its boulders.

An asteroid's history is determined in large part by its strength against collisions with other objects1,2 (impact strength). Laboratory experiments on centimetre-scale meteorites3 have been extrapolated and buttressed with numerical simulations to derive the impact strength at the asteroid scale4,5. In situ evidence of impacts on boulders on airless planetary bodies has come from Apollo lunar samples6 and images of the asteroid (25143) Itokawa7. It has not yet been possible, however, to assess directly the impact strength, and thus the absolute surface age, of the boulders that constitute the building blocks of a rubble-pile asteroid. Here we report an analysis of the size and depth of craters observed on boulders on the asteroid (101955) Bennu. We show that the impact strength of metre-sized boulders is 0.44 to 1.7 megapascals, which is low compared to that of solid terrestrial materials. We infer that Bennu's metre-sized boulders record its history of impact by millimetre- to centimetre-scale objects in near-Earth space. We conclude that this population of near-Earth impactors has a size frequency distribution similar to that of metre-scale bolides and originates from the asteroidal population. Our results indicate that Bennu has been dynamically decoupled from the main asteroid belt for 1.75±0.75 million years.

Spaceborne Radar Sensor Architecture for Debris Detection and Tracking

This article delves into a novel spaceborne radar payload transceiver for augmenting space-based monitoring capabilities for near-Earth space situational awareness. The sensor complex data hypercube structure and sensor timing hierarchies in surveillance mode are addressed along with a suitable low pulse repetition frequency range and range-rate search with a pause while scan collection strategy. A bespoke active electronically scanned array-based Pulse Doppler Radar sensor in the Ka-band is then defined in order to cope with the significant Doppler stress characterizing a burst of echoes from hypervelocity debris targets. Before feeding the onboard Bayesian tracker, the complex data hypercube is processed by means of a Doppler filter bank including pulse compression in cascade with a constant false alarm rate-like block.

Environmental Aspects of Using Space Solar Power Plants to Create Information in Orbit

Considered a proposal to combat global warming, which consists in placing the creation of information in near-earth space. It is shown that instead of a space solar power plant that transmits energy to terrestrial consumers, it is more profitable to organize an orbital territorial-production complex, in which a new information and communications energy production cycle is implemented: the energy received from the Sun is used on site to create and store valuable information, and instead of an unused technology of wireless energy transmission to Earth, using a well-functioning space communication technology. Using the simplest mathematical model, it was demonstrated that the profitability of orbital information must be considered taking into account the anthropogenic impact on the climate of ground data centers. The dependence of the profitability of an information orbital product in comparison with a ground-based analogue on the cost of emission quotas for waste heat and greenhouse gases is discussed.

Coherence of Coronal Mass Ejections in Near-Earth Space

Interplanetary coronal mass ejections (ICMEs) primarily move radially as they propagate away from the Sun, maintaining approximately constant angular width with respect to the Sun. As ICMEs have typical angular widths of around 60^{circ }, plasma elements on opposite flanks of an ICME separate in the non-radial direction at a speed, v_{mathrm{G}}, roughly equal to the ICME radial speed. This rapid expansion is a limiting factor on the propagation of information across an ICME at the local Alfvén speed, v_{mathrm{A}}. In this study, the 1-AU properties of ICMEs are used to compute two measures of ICME coherence. The first is the angular separation for which v_{mathrm{G}} exceeds the local v_{mathrm{A}}. The second measure is the angular extent over which a wavefront can propagate as an ICME travels from a given heliocentric distance to 1 AU. For both measures, ICMEs containing magnetic clouds show greater coherence than non-cloud ICMEs. However, even for magnetic clouds, information is unable to propagate across the full span of the structure. Thus interactions of ICMEs with other solar wind structures in the heliosphere are likely to lead to localised distortion, rather than solid-body like deflection. For magnetic clouds, the coherence length scale is significantly greater near the centre of the spacecraft encounter than at the leading or trailing edges. This suggests that magnetic clouds may be more coherent, and thus less prone to distortion, along the direction of the magnetic flux-rope axis than in directions perpendicular to the axis.

Azide Method for Generating Metal Vapors in Space

Modern methods of rocket research of the upper layers of the atmosphere and near-Earth space cannot be imagined without the use of glowing artificial clouds (GAC). Traditional pyrotechnic methods for generating vapors of alkali and alkaline earth metals, used for the formation of GAC in space, are ineffective and require, as a rule, the use of metals with high chemical activity. The article presents the results of studies on the development of an alternative method for generating vapors of alkali and alkaline earth metals to create GAC in near-Earth space using inorganic azides of the corresponding metals. The long-term use of pyrotechnic metal vapor generators to create GAC in the upper atmosphere, equipped with azide pyrotechnic compositions, confirmed their high efficiency, reliability and safety of use.

Very-Low-Frequency transmitters bifurcate energetic electron belt in near-earth space

Very-Low-Frequency (VLF) transmitters operate worldwide mostly at frequencies of 10–30 kilohertz for submarine communications. While it has been of intense scientific interest and practical importance to understand whether VLF transmitters can affect the natural environment of charged energetic particles, for decades there remained little direct observational evidence that revealed the effects of these VLF transmitters in geospace. Here we report a radially bifurcated electron belt formation at energies of tens of kiloelectron volts (keV) at altitudes of ~0.8–1.5 Earth radii on timescales over 10 days. Using Fokker-Planck diffusion simulations, we provide quantitative evidence that VLF transmitter emissions that leak from the Earth-ionosphere waveguide are primarily responsible for bifurcating the energetic electron belt, which typically exhibits a single-peak radial structure in near-Earth space. Since energetic electrons pose a potential danger to satellite operations, our findings demonstrate the feasibility of mitigation of natural particle radiation environment.