Artificial Space Objects Research Articles

Satellites state vectors refinement based on international laser ranging system using machine and deep learning

With the increasing number of space objects in near-Earth space, the necessity of high-precision determination of space objects state vectors, as well as its classification by size, velocity, and potential danger to active satellites and space stations is becoming increasingly important for space flight safety services. In case of necessity of taking decisions of satellites orbit corrections and avoiding space emergency situations in real time mode artificial intelligence services could be used. The results proposed in this study show that machine and deep learning models can significantly improve the accuracy of determining the space objects state vector for classical numerical models and space catalogs, that is very essential task for safety space flights. The parameters of the Two-Line-Elements catalog and the model of it convertation to state vector are considered as input data to process, International Laser Ranging Service data from ground stations is considered as the ground truth measurements. The methodology considered here can be applied to any artificial space objects with various orbit parameters, thus, helps to provide space flights safety assurance.

On the need to assess and mitigate the risk from uncontrolled re-entries of artificial space objects in view of the current and future developments in space activities

From 1 January 2010 to 24 August 2023, 566 orbital stages and 511 spacecraft with a radar cross section >1 m2 have re-entered without control the Earth's atmosphere. The total returned mass was 1650 metric tons, corresponding to a mean of 115 metric tons per year. 77% of the mass belonged to orbital stages, 23% to spacecraft. The uncontrolled re-entries of orbital stages are currently dominated by China, accounting for more than half of the decaying mass, while for spacecraft 2/3 of the mass belongs to American satellites. 60% of the re-entries occurred within 2 years of the launch. The ground casualty expectancy due to orbital stages was always predominant over that from spacecraft, by an average factor of nearly three. From 2010 to 2018, the total casualty probability remained substantially stable, with a mean annual value just over 1%. Since 2019, instead, the annual casualty probability of both spacecraft and orbital stages progressively increased, reaching a total value of around 3% in 2022 and 2023 (extrapolated). Even assuming a stable launch activity, in the coming years, when many of the recently launched spacecraft will start to re-enter, the casualty expectancy of orbital stages will remain basically the same, while that of spacecraft might progressively increase by a factor of 20. This would lead to an annual casualty probability of about 20%, even more in case of a further growth in launch activity, very likely based on current forecasts. The quick implementation of widespread and effective mitigation measures, like controlled de-orbiting and design for demise, is therefore necessary, to prevent the situation from deteriorating too much.

Environmental impacts of increasing numbers of artificial space objects

For much of their existence, the environmental benefits of artificial satellites, particularly through provision of remotely sensed data, seem likely to have greatly exceeded their environmental costs. With dramatic current and projected growth in the number of Earth‐observation and other satellites in low Earth orbit, this trade‐off now needs to be considered more carefully. Here we highlight the range of environmental impacts of satellite technology, taking a life‐cycle approach to evaluate impacts from manufacture, through launch, to burn‐up during de‐orbiting. These include the use of renewable and nonrenewable resources (including those associated with the transmission, long‐term storage, and distribution of data), atmospheric consequences of rocket launches and satellite de‐orbiting, and impacts of a changing nighttime sky on humans and other organisms. Initial estimations of the scale of some impacts are sufficient to underscore the need for more detailed investigations and to identify potential means by which impacts can be reduced and mitigated.

Selection of a given space object from the multitude observed by a specialized spacecraft

Introduction: For the detection of most dangerous artificial space objects (space junk) in near-earth space, it is planned to use specialized spacecraft equipped with optoelectronic devices. In relation to this a problem arose when selecting the most dangerous object from the observed multitude, based on the measurements of inhomogeneous selective features that characterize these objects. Purpose: To form a composite non-dimensional indicator that depends on the quantity and quality of measurement information about the observed space objects, and that determines the decision rule for selecting the most dangerous object to maximize the probability of making the right decision. Results: A method is proposed for selecting the most dangerous space object under the condition of the limited amount of measurement information about physically inhomogeneous selective features of space objects located in the area which is observed by a specialized spacecraft. It should be noted that the measurement data on individual selective features of space objects may be absent. The proposed decision rule for the selection of the most dangerous space object takes into account not only inaccuracies and errors, but also the number of measurements of the selective characteristics of each object. The efficiency of the method has been demonstrated on a relevant example. Practical relevance: The simplicity of the determination of composite indicators characterizing space objects that are located in the area observed by a specialized spacecraft, and of the decision rule for selecting the most dangerous object makes it possible to solve this problem on board a specialized spacecraft in real time.

Potential hazards analysis of the space debris over 10 cm in size based on their orbital parameters

The increasing population of artificial space objects every year triggers a polemic about the safety of launching satellites into orbit as well as the safety of satellites operating in space. The artificial space object also provides a potential danger when it re-entry and then falls to Earth. Indonesia as a country that has the 2nd longest coastline in the world and has a span of 1/8 of the world’s circumference (± 5000 km) is very vulnerable to experience atmospheric re-entry of which these space objects might fall to the Earth. Space objects that have the potential to experience re-entry and then fall to the Earth originate from space objects with a size of more than 10 cm. Until 2020, there are 6560 space objects with size 0.1<RCS<1 m2 and 9526 space objects with size RCS>1 m2. There are 5678 pieces of space debris with 4435 pieces with size 0.1<RCS<1m2 and 1236 pieces over 1m2. Of all space debris, only those with an altitude below 200 km potentially fall to the Earth which is around 1517 pieces. In addition, the most dangerous debris over the Indonesia region commonly has a low inclination with the passage around 12 to 16 times a day. However, there are only 15 objects which satisfy this category with a small number. Hence, the need of space debris surveillance should be done for mitigation purposes.

MONITORING THE ARTIFICIAL SPACE OBJECTS WITH UKRAINIAN NETWORK OF OPTICAL STATIONS

The article describes the successes and challenges of the Ukrainian network of optical stations (UMOS) in recent years in the field of astrometric observations of artificial space objects both in low-Earth orbit (LEO) and geostationary Earth orbit (GEO). UMOS was established in 2012 as a joint partnership of organizations interested in satellite observations for scientific purposes and practical near Earth space monitoring. The main purpose of the UMOS has been (and still is) to combine scientific and technical means with regular optical (positional and / or non-positional) observation. The short list of equipment of the UMOS members are given in the tables. The programs for observations, used methods and obtained results are described in the paper. In conclusion, the advantages of observations of artificial space objects by means of a network are summarized. The experience of UMOS and main results obtained by UMOS can be considered as the first step to create the SSA system of Ukraine.

Application limitations of a laser guide star in adaptive optoelectronic systems caused by its jitter in the atmosphere

Application limitations caused by the jitter of a laser guide star used for the compensation of atmospheric phase distortions are considered for Earth-based adaptive optoelectronic systems for the observation of natural and artificial space objects. The spatial coherence radii (Fried parameter) for which a laser beam remains within the isoplanatic angle under the jitter effect during guide star formation are estimated using locally homogeneous and isotropic atmospheric turbulence models. Beam deflections in two mutually orthogonal directions are considered to be distributed normally, and the probability of the beam remaining within the isoplanatic angle is considered to be subject to the Rayleigh law. The angular divergence of the deflected beam is estimated for a short exposure with a duration less than the atmosphere freezing time for the far and near fields of the emitting laser aperture.

Comparison of Deterministic Methods to Estimate Sidereal Rotation Period from Light Curves

The importance of determining the sidereal rotation period of an astronomical object on future investigations pertaining to said object has been well documented in the literature. Researchers, however, have differed in their techniques used to estimate and model objects in the space catalog. In this paper, several period-estimation methods will be explored ranging across Fourier and phase-folding techniques. These methods will be tested using ground-based observations of light curve data for various resident space objects that fall under a rigid body context (i.e., asteroids, satellites, probes, rocket bodies) and celestial objects like stars and extrasolar planets. The effect of varying sample size, the inadequacies in unevenly sampled data processing, autonomy of the method, and complexity of parameters are investigated. For the models of artificial space objects that are not open source, a simulation is used to generate synthetic light curves with which all of the above-mentioned techniques are also employed. To account for heterogeneity in method parameters, each technique is tested with a range of values to optimize the rotational period. Results for uniformly sampled asteroid data as well as nonuniformly sampled stellar objects and generic sinusoidal data show variances in accuracy of the methods, but certain methods stand out.

Theoretical Foundations Development of Space Adaptive Video Information Systems Synthesis

The main provisions and principles of the synthesis of adaptive video information systems designed for recording and analyzing images of dynamic scenes at the stages of long-range detection of artificial space objects, ballistic and controlled approach to them in the middle and near zone of cooperation are considered. Based on the principle of dominant information, it is shown that the basis for the development of methods and algorithms for processing video information in on-board surveillance systems is the joint adaptive processing of video information in photo-detector matrices and in digital processors in order to maximize the quality of information issued to the consumer by suppressing background and noise information by adaptive hysteresis control of the frame frequency, frame resolution and signal accumulation time in the photodetector matrix, as well as the use of parametric neural network detectors-classifiers.

On the choice of the aperture diameter of the probe laser in ground-based adaptive optoelectronic systems in the formation of a sodium reference star

Subject of study. The authors propose an integrated approach to the problem of determining the aperture diameter of a probe laser that forms a laser reference star used in ground-based adaptive optoelectronic systems. The relevance of this study is due to the fact that modern large-aperture optical systems for tracking natural stars and artificial objects (spacecraft or fragments of space debris) widely implement the technology of forming laser stars and use them as reference sources for correcting phase distortions of a turbulent atmosphere. The choice of the energy and spatiotemporal characteristics of laser guide stars is related both to the parameters of the probe laser (radiation power and aperture diameter), which forms the guide star, and to the spatiotemporal characteristics of the atmosphere. Method. The diameter of the probe laser aperture (for the near and far radiation zones) is estimated taking into account the spatial coherence radius of the atmosphere r0, the radiation intensity and angular divergence of the laser beam, its random root-mean-square angular deviation (jitter) with respect to the calculated direction to the space objects. Main results. The estimation of the angular divergence of a laser beam is based on a comparative analysis and generalization of theoretical results obtained by calculating the optical resolution in systems for acquiring images of natural space objects. It is shown, in particular, that when determining the size of the aperture along with the value of the angular divergence of the probe beam, it is necessary to take into consideration the decrease in its radiation intensity with an increase in the diameter with respect to the radius of atmosphere coherence. The practical significance. The results are essential, firstly, for the development of ground-based adaptive optoelectronic systems for tracking artificial space objects, and secondly, for determining the geographic locations of the optoelectronic systems taking into account the astronomical climate.

Контроль працездатності НВЧ-каналів приймання телеметричної інформації за непрямими параметрами

The paper presents an analysis of existing methods of controlling the efficiency of multipart radio engineering systems and their individual components. The authors consider the situations when traditional methods do not allow controlling the efficiency of the system in operational mode. The study substantiates the practicability and possibility of estimating the efficiency of microwave channels for receiving telemetry information from artificial space objects according to indirect criteria. The principle of forming a list of indirect control criteria is demonstrated on the example of the functional diagram of the radio receiver system of the RT-32 C, X, K radio telescope. The study formulates the principles of creating a system designed to control the parameters of the information channel of such a microwave radio receiver system by controlling indirect parameters which correspond to the chosen criteria and the list of the basic parameters. A list of indirect parameters affecting the performance of the entire system by controlling the characteristics of its main parameters has been created. The paper carefully considers the problems that arise when equipping the radio receiver system with built-in tools for controlling and managing the indirect parameters. A system of nominal equations is designed for estimating the state of the basic parameters of the components of the radio receiver system. Each of the indirect parameters is codified in digital form. An example of a block diagram of a distributed control and management system for complex radio devices is presented. The authors determine acceptable deviations for the indirect parameters relative to the nominal values of the direct parameters for controlling the state of both individual devices and the whole multipart system. It is proposed to implement a control and management system of a complex system by using a specialized controller-based circuit board built into each functional device of the radio receiver system. One possible version of such board, its design and all functional units are considered in detail. The proposed methods of controlling and managing the state of a multipart radio-technical system when receiving telemetric information directly in the working mode has been successfully approved during a series of radio astronomical studies on RT-32 C, X, K radio telescope at the Space Researches and Communications Center of the State Space Agency of Ukraine.

Участь Харківської астрономічної обсерваторії та її представників у радянській космічній програмі у 1960-х роках

The article is devoted to the studying of documentary facts on the history of astronomy of the 1960s. Its purpose is to highlight the events related to the participation of the Kharkiv astronomical observatory in the Soviet space program in a certain period. The chronology of involvement of Kharkiv astronomers in programs on development and functioning of objects «V-67», «Е-7», «Е-8», «L-3», «М-69», creation of artificial Lunodrome, processing of photographic materials, that were obtained by spacecraft «Lunar orbiter 2», «Ranger 7», «Surveyor 1», «Luna-9», «Luna-12», «Luna-13», and «Zond-3» are considered. The directions of scientific research in projects «Altai», «Atlas», «Luks», and others of the Astronomical observatory of O.M. Gorky Kharkiv State University are analyzed. The main tasks that the Kharkiv astronomical observatory carried out in the 1960s were found next: photometric studies of details on the reverse side of the Moon; study of the physical, mechanical, and chemical properties of the lunar soil and its optical properties; photometric analysis of certain areas of the lunar surface; photometric calculations necessary for the design of orientation systems of automatic interplanetary stations; study of the luminosity of the lunar surface. The retro-information resources, which were firstly involved into consideration, provided a chronological sequence of events related to the participation of the University observatory in the development and functioning of artificial space objects during the given period. These resources helped to specify the achievements of Kharkiv astronomers in the Soviet program of space exploration and to prove (or clarify) some little-known facts.

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

Reasons for change in artificial space objects own rotation

Purpose. Photometry in conjunction with positional observations is currently the main method of controlling the operation of artificial space objects in orbit with which radio communication is lost. This paper presents an analysis oflong-range photometric observations of low-orbital artificial Earth satellites of various functionality class.Methods. A methodological approach to determining the dynamic characteristics of the behavior of space objects in orbit using photometric information in the form of light curves is considered. It is based on studies of the characteristics of the object’s own rotation and their causes.Results. 40 years of experience in such studies has made it possible to evaluate virtually all possible factors affecting its functional dynamics by changes in the light of an object. The paper presents six reasons for the occurrence of a satellite’s own rotation in the Earth’s orbit. They cover both natural factors and the effects of human intervention.Conclusions. If the size and mass of the destabilized satellites are known, then this satellite can be used as an indicator of the course of physical processes in the Earth’s atmosphere at the height of the satellite’s orbit. The variants of finding the period of own rotation of the object in manual and automatic modes are described.

Three-dimensional image creation for artificial space object by laser ranging

Subject of Research. The paper presents a novel method for creation of an artificial space object “depth map”. The analysis of methods for creation of three-dimensional image of an artificial space object by laser locator is performed and the experimental study results are presented. The following television location methods form the basis for development. The first method of television location proposed by P. S. Vargin was developed in “Television Scientific Research Institute” (St. Petersburg, Russia). The method provides for creation of a “depth map” for remote artificial space object in a double flight time of one light pulse from the observation point to the object. The second method is used in the pulse range determination system and is based on flash-lidar performance. This system irradiates the space area of interest where the object of observation is supposed to be located; the reflected signal from the object is first recorded by a photodiode and the distance to the object is estimated. Then the object three-dimensional image is built on a certain number of points. The third method is a multi-pulse system of television laser locator based on the use of multi-pulse illumination for the study of the object under observation. Thus, it is possible to increase significantly the resolution in depth up to 10–50 mm and reduce the peak power of the laser radiation. Method. A novel method of multi-pulse illumination of an artificial space object is proposed on the basis of the considered methods in order to increase the energy of the optical signal. The method is based on the use of the charge-coupled device matrix in the mode of ultra-short accumulation time (up to 200 ns). This method enables rapid high-precision measurement of angular resolution (0.25 ang. min), range to the target (100–2000 m) and a “depth map” creation. Main Results. A laser system model was developed consisting of a television camera based on the charge-coupled device with a resolution of 752×582 pixels, a frame frequency of 50 Hz, and a laser diode with minimum pulse duration of 40 ns and a pulse repetition rate of 1 kHz. Control and synchronization of the laser is carried out by FPGA installed in the television camera ensuring the synchronization of the camera and the emitting laser. The system gives the possibility to realize interchangeable relations of distance measurement accuracy, angular and time resolution. The simulation has showed that the measurement error at small distances is less than 20 mm, and at a distance of 2000 m is less than 160 mm. Practical Relevance. The obtained results determine the characteristics of the television laser system necessary to solve the location problem for artificial space objects at a range from 100 m to 2000 m. Analysis of studies shows that modern lasers are aimed at operating in the spectral range of 1.54–1.57 μm, that reduces significantly the efficiency of the television laser system from 2 to 10 times. Therefore, it is necessary to implement laser systems with wavelengths of 0.86–1.06 microns to improve the tactical and technical properties for space inspection.

Using convolutional neural networks to automatically select small artificial space objects on optical images of a starry sky

This article discusses the use of convolutional neural networks to solve the problem of automatically selecting moving objects on a moving starry background when their images exhibit speed blur. The article gives the results of testing several networks that have substantially less structural complexity than does the prototype. The estimates obtained for the accuracy and selection rate of several of the networks studied here are evidence that it is promising to use such networks to detect, classify, and estimate the location of two types of objects in the instrument’s coordinate system when resources are severely limited.

Discovering the smallest observed near-earth objects with the space surveillance telescope

The Space Surveillance Telescope (SST) is an advanced optical sensor designed and tested by MIT Lincoln Laboratory for the Defense Advanced Research Projects Agency (DARPA), which is currently in the process of being integrated into the Space Surveillance Network. By operating the telescope in a manner normally intended for the discovery of small, artificial space objects, SST is serendipitously sensitive to the detection of very small asteroids as they traverse close to the Earth, passing rapidly through SST's search volume. This mode of operation stands in contrast to the standard approach for the search and discovery of asteroids and near-Earth objects (NEOs), in which longer revisit times restrict survey sensitivities to objects moving no faster than about 20 °/day. From data collected during SST's observation runs in New Mexico, we detail the discovery of 92 new candidate objects in heliocentric orbit whose absolute magnitudes range from H = 26.4 to 35.9 (approximately 18-m to 25-cm in size). Some of these discoveries represent the smallest natural objects ever observed in orbit. We compare the candidate objects with bolide observations (Brown et al., 2016).

A Proposal of Alternative Models to Replace the South Korean Space Object Response Models

This article reviews South Korea's response model for space object impacts, re-entries, and collisions. These are countermeasure models that are prepared for natural or artificial space objects falling in South Korea or colliding in space, and they employ the Ministry of Science and ICT (MSIT) to perform 4 stages that include prevention, preparation, response, and restoration. However, the article suggests that this process is inefficient given that the MSIT specializes in research and development but is expected to perform disaster response tasks in the event of natural or manmade space object impacts and re-entries. The research presents 2 alternative models to the current ones: the first model specifies that the MSIT and the Ministry of the Interior and Safety (MOIS) work together, and the second model designates the MOIS as the only agency responsible for the disaster response. These alternative models would more effectively handle disaster management than would the current models.

Application of convolutional neural networks for automatic selection of small-sized artificial space objects on optical images of the starry sky

Application of convolutional neural networks for automatic selection of small-sized artificial space objects on optical images of the starry sky

3D Reconstruction of Space Objects from Multi-Views by a Visible Sensor.

In this paper, a novel 3D reconstruction framework is proposed to recover the 3D structural model of a space object from its multi-view images captured by a visible sensor. Given an image sequence, this framework first estimates the relative camera poses and recovers the depths of the surface points by the structure from motion (SFM) method, then the patch-based multi-view stereo (PMVS) algorithm is utilized to generate a dense 3D point cloud. To resolve the wrong matches arising from the symmetric structure and repeated textures of space objects, a new strategy is introduced, in which images are added to SFM in imaging order. Meanwhile, a refining process exploiting the structural prior knowledge that most sub-components of artificial space objects are composed of basic geometric shapes is proposed and applied to the recovered point cloud. The proposed reconstruction framework is tested on both simulated image datasets and real image datasets. Experimental results illustrate that the recovered point cloud models of space objects are accurate and have a complete coverage of the surface. Moreover, outliers and points with severe noise are effectively filtered out by the refinement, resulting in an distinct improvement of the structure and visualization of the recovered points.