LEO Satellite Research Articles

Воздействие операций сближения на космический мусор на пути к устойчивой космической деятельности

Abstract. In the last thirty years, the encounter and approach of Rendezvous Proximity Operations (RPO) of human made space objects have developed. This development indicated by the developments in field of technology. The focus of this study is regarding RPO as a mission that has potential to increase the amount of space debris. This study aims to analyze the RPO activity as a potential hazardous mission in increasing the space debris population. Moreover, this research aims to analyze RPO activity as a potentially vulnerable mission to increase the space debris population. In this study, the method was carried out descriptively, by exploring data and information about RPO. The results of this study indicated that RPO activity still limited to LEO due to the high difficulty level for the GEO orbit. The results of this study indicate that RPO activity is still limited to LEO due to the high difficulty level for the GEO orbit. This is actually because in LEO orbit have more space debris (75%) than GEO orbit and it has a higher risk of falling to Earth. Based on the results obtained, it can be concluded that RPO activities are double-edged and therefore greater supervision needs to be carried out especially to safeguard Indonesia’s interests in space.

Design of LEO Constellations with Inter-satellite Connects Based on the Performance Evaluation of the Three Constellations SpaceX, OneWeb and Telesat

The idea of designing LEO’s satellite constellations has become very important for internet access. Several LEO satellite constellations have been designed and used for global communications. In this paper, by examining three LEO satellite constellations, namely SpaceX’s 4425 satellites Ku-Kaband system, OneWeb’s 720 satellites Ku-Ka-band system, Telesat’s 117 satellites Ka-band system. And evaluating the power of data transmission and their telecommunications, we come close to a conceptual design area. First with the mathematical modeling and formulation and the design of inter-orbital communications for satellites, intersatellite communications, inter-orbital communications, we get a complete design based on the genetic algorithm for LEO satellite constellation design. And then, using simulations and design software, the final results of the designed model are obtained. Finally, we compare the results of the designed model with other existing LEO satellite constellations.

Ultra-Dense LEO Satellite Based Formation Flying

In this article, we consider a downlink ultra-dense LEO-based multi-terminal satellite system where multiple satellites fly in formation to serve a number of ground terminal stations for data transmission. Benefited from the dense satellite constellation, high channel capacity can be achieved via the massive virtual antenna array formed by multiple satellites. We aim at exploring how the satellite distribution and formation size influence the channel capacity in this case. We first derive the upper bound of the channel capacity in the general multi-antenna satellite networks. The single-antenna satellite case is considered where we present the specific forms of the derived capacity bounds to prove that the capacity first increases linearly then increases more and more slowly with the satellite formation size, and there exists an optimal LEO satellite distribution to achieve the maximum capacity of the system. Simulation results verify our theoretical analysis and show that such statements also hold for the general multi-antenna satellite case.

Investigation and feasibility study of using components with different categories from the perspective of radiation damage in LEO and GEO orbits

Space radiation can affect the performance and reliability of components in space systems. This paper focuses on the investigation of three types of radiation damage including ionizing dose, displacement damage, and single event damage using OMERE software. Considering the outputs of this software, how to use and use a variety of electronic components with different commercial, military and space grades in LEO and GEO satellites is discussed. These components have the least risk of displacement damage. Mass budget constraints should also be considered when using commercial components in the GEO circuit. The maximum thickness for the safety of components in LEO and GEO circuits is 2.6 mm and 9.5 mm respectively. Given the inability of SEE damage to increase in thickness, the best solution to this damage is to use radiation-resistant solutions, especially software issues.

Chaotic attitude dynamics of a LEO satellite with flexible panels

This paper deals with the attitude motion of LEO satellites with deployable side panels designed for passive aerodynamic stabilization in a rarefied atmosphere. The influence of the aerodynamic and gravitational torques on the planar attitude motion near the unstable and stable equilibrium positions is studied. The presence of the unstable equilibrium position and small perturbations such as the oscillations of the flexible panels is the cause of chaos. A critical altitude is found above which the chaos is possible. The equations of planar attitude motion of the satellite with deployed flexible panels are obtained. The chaotic behavior of the system is demonstrated through numerical simulations of the attitude motion of a 3U CubeSat. The results of this paper can be used to analyze the applicability of passive aerodynamic stabilization for LEO satellites.

Airborne GNSS-R: A Key Enabling Technology for Environmental Monitoring

Weather forecast using GNSS-R relies, to a large extent, on data acquired by airborne and spaceborne platforms due to the extended coverage that can be achieved. GEO satellites can retrieve measurements over large areas but with spatial resolutions on the order of thousands of meters per pixel. LEO satellites with polar orbits can provide measurements over the entire world, but they cannot provide good spatial or high temporal resolutions by themselves. LEO constellations of small satellites have the same coverage with improved spatial resolution and revisit times by using data fusion techniques. High-altitude pseudo-satellites offer an excellent temporal and spatial resolution but only over limited areas. In this article, the potential of using hosted GNSS-R payloads on commercial aircraft is explored as an alternative and cost-effective means to achieve a very high resolution and a very low revisit time for regional environmental applications. Finally, a case study of soil moisture monitoring over Europe is presented, including an analysis of the expected performance.

Mechanical stress induces a scalable circularly polarized LEO satellite antenna with Quadrifilar spiral.

This paper investigates a left-hand circularly polarized (LHCP) antenna and a right-hand circularly polarized (RHCP) antenna on LEO Satellite, which is based on the phase-tuning metasurface. We overcome its inherent limitations in size, weight and power, and designed a high-gain, ultra-lightweight, scalable antenna for small satellite communications. The antenna can generate continuous and large tunability of subwavelength, with low-Q resonators. The simulated and experimental results verify that different capacitance and inductance modes can be effectively generated by rotating the spiral arms of single-arm spiral antennas with corresponding degrees, which greatly simplify the feeding network. The maximum gain of the normal position within the angle of the uplink and downlink is 4~9 dBi higher than that of the ordinary polarized antenna. In addition, the design method proposed to this article is superior to the reference system in terms of impedance bandwidth, axial ratio bandwidth, and operation frequency. The performance achievements of this paper are implemented within the bandwidth of 3 MHz of uplink and downlink, such as impedance bandwidth is 3 MHz with impedance of 50, axial ratio bandwidth is 2.5 MHz, operation frequency of uplink is 240-243 MHz, downlink is 320 MHz and 401 MHz, and the voltage standing wave ratio (VSWR) is less than 2 dB which is so called S parameter, the above parameters can meet the performance index design requirements.

Connectivity Mode Management for User Devices in Heterogeneous D2D Networks

Device-to-Device (D2D) paradigm is one of the key enablers for boosting the energy efficiency (EE) of networks. For the actualization of EE in multi-mode heterogeneous D2D networks, resource allocation should be executed accordingly. In that regard, we study resource allocation management in heterogeneous D2D networks where there is a LEO satellite and a cellular base station (BS) with multi-mode user devices (satellite, BS and D2D connectivity modes) dispersed in the terrestrial cell. We formulate the EE optimization of mode selection constrained by a designated total network service capacity threshold. We also implement a sub-optimal pattern search algorithm (PSA) with the aim of enhancing EE while keeping total system service capacity at an acceptable level and compare it to alternative resource management schemes. Based on our simulation results, PSA achieves the most beneficial EE value in contrast to other schemes while still managing to meet the goodput threshold. Additionally, we discuss the multi-mode nature of our heterogeneous network from EE and goodput perspectives.

Multi­level model of terrestrial and non­terrestrial telecommunications using optical wireless technologies

Non-terrestrial communication technologies will become a key component for the development of future 6th generation (6G) networks. Potentials, implementation prospects, problems and solutions for non-terrestrial telecommunications remain open areas for future research. The article discusses the use of millimeter and optical wavelengths in various configurations of multilevel space communications using LEO satellites, stratospheric platforms and unmanned repeaters. Wireless communication in MMW and OR has great potential for use in space communication systems. These technologies have the advantages of using azimuth line-of-sight channels in comparison with terrestrial ones. For example, the total zenith attenuation can be much less than the linear attenuation in the lower atmosphere. It also has advantages in terms of reconfiguration virtuality, coverage area and energy (spectral) efficiency. A sudden drop in communication quality due to atmospheric phenomena, including severe atmospheric turbulence, leads to the need for adaptive dynamic beam steering, which also leads to a decrease in the use of resources, both frequency and energy. Wireless and fiber optic communication systems have similarities in the operating wavelength range, processing methods. The methods of radio-photonics can be applied to wireless communication systems, where the technology of converting radio waves into optical, including the terahertz range, can be used. The comparison of the capacity of the Shannon channel for various multi-level scenarios of the satellite communication line is carried out. The directions of research to ensure the continuity of communication, adaptation to weather conditions, and the achievement of throughput up to 100 Gbit/s are analyzed.

A Reliable Separation Algorithm of ADS-B Signal Based on Time Domain

With the development of Aerospace Science and technology, automatic dependent surveillance-broadcast has become a core technique in the field of air surveillance. Installing ADS-B receiver on LEO satellite can solve the problem of small coverage of ground receiver, to realize global coverage and monitoring. However, the satellite ADS-B system is faced with serious collision and overlap problems, which has a serious impact on the signal decoding, leading to the wrong decoding or even loss of important information. In this paper, a time-domain ADS-B blind signal separation algorithm is proposed. When there is a certain power difference between the two source signals, the overlap signals are offset by the high-power signal and low-power signal to get the corresponding cancellation signals. According to the superposition mode of different pulses, different bit decision results are obtained according to the amplitude, to recover the source signal. Simulations demonstrate that the proposed algorithm is feasible and has a lower bit error rate.

Convective System Observations by LEO and GEO Satellites in Combination

The combination of Low Earth Orbit (LEO and GEO stationary (GEO satellites brings significant advantages to observe, monitor, and understand convective systems (CSs and the associated vertical and horizontal dynamics. Two LEO, C-band Sentinel-1 Synthetic Aperture Radar (SAR and L-band SMAP radiometer, are used to observe surface wind patterns, while the other LEO (Aeolus lidar instrument offers the measurements of intense convective downdrafts. Meteosat GEO is used to detect deep convective clouds. Four case study examples of LEO and GEO combination illustrate here the matching in location and observation time between deep convective clouds, intense downdrafts, and strong surface wind gusts. In particular, the 2D deep convective cloud patterns and surface wind patterns have the same direction displacement. The observations of surface wind patterns by two different LEO (Sentinel-1 and SMAP indicate that the high-intensity radar backscattering on Sentinel-1 images should be induced by convective wind gusts rather than hydrometeors or convective precipitation at the sea surface as suggested in previous references. Finally, the convective wind gusts estimated from Sentinel-1 and SMAP data correspond to those obtained by the high-frequency radars, small-scale numerical models, and in-situ measurements.

Анализ применимости стандартных протоколов динамической маршрутизации в сетях спутниковой связи на основе низкоорбитальных космических аппаратов

One of the key components of communication networks, which determines the principles of their operation, are traffic routing protocols. The purpose of this article is to consider the possibility of using widely used dynamic routing protocols in LEO satellite communication systems. Based on the available publications, the analysis of the initial data was carried out and the conditions for the functioning of routing protocols in low-orbit satellite communication systems, as well as the basic requirements for such protocols, were formulated. The analysis of the functioning of the dynamic routing protocols in the given conditions is carried out. The disadvantages of the considered protocols are highlighted and characterized. The main conclusion of the article is the inexpediency of using the considered protocols in low-orbit satellite communication networks due to the high resource requirements and the insufficient speed of propagation of changes. The results can be used to substantiate technical solutions in the design of low-orbit satellite communication networks.

Max Completion Time Optimization for Internet of Things in LEO Satellite-Terrestrial Integrated Networks

In this article, we investigate max completion time optimization for Internet of Things (IoT) in LEO satellite-terrestrial integrated networks (STINs), in which IoT devices use non-orthogonal multiple access (NOMA) scheme to transmit data to central earth stations (CESs), and orthogonal multiple access (OMA) scheme is used for data transmission from CESs to LEO satellite. We decouple this problem into two subproblems: 1) max completion time optimization in terrestrial networks and 2) max completion time optimization among satellite beams. Different from the existing works about NOMA data transmission in terrestrial networks, we propose a cooperative NOMA scheme, and derive the closed expressions of the optimal cooperative data and the optimal transmit power of IoT devices. Based on the closed-form expressions, a joint subcarrier assignment and cooperative NOMA pairing (JSACNP) approach is proposed to minimize the max completion time in terrestrial networks by utilizing matching theory. Then, to minimize the max completion time among satellite beams, the optimal linear receiver expression is derived with fixed transmit power. Convex optimization is utilized to solve transmit power optimization, we propose an algorithm to solve it by CVX tool. An iterative algorithm is proposed for improved performance. Finally, numerical results are provided to evaluate our proposed algorithms, compared with some other proposed approaches or algorithms.

Correction to “Beam Coverage Comparison of LEO Satellite Systems Based on User Diversification”

In the above article <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> , the authors inadvertently did not include the affiliation of the first author. The name of the organization is “University of Chinese Academy of Sciences.”

Joint Rate Control and Load-Balancing Routing with QoS Guarantee in LEO Satellite Networks

Joint Rate Control and Load-Balancing Routing with QoS Guarantee in LEO Satellite Networks

Experiences with the GPS in Unstabilized CubeSat

The paper summarizes the experiences with the operation of the piNAV GPS receiver in a 1U unstabilized CubeSat operated on LEO orbit. piNAV L1 is a GPS receiver developed by an author for small satellite missions. The receiver is equipped with the 15 GPS L1 C/A channels and acquisition accelerator that shortens the cold start of the receiver on LEO to 65 s. The typical power consumption is 120 mW. Lucky-7 is a private 1U technological CubeSat with power budget 1 W that operates on the quasisynchronous polar orbit at altitude 520 km. One of its scientific missions is to test the operation of GPS. The space experiments proved the successful operation of the GPS receiver. The position information was available for approximately 80% of the time, where the position outage was caused by a satellite rotation and relatively long navigation signal reacquisition. The experimental data proved that the position availability can be improved by a higher-performance signal acquisition engine.

Equilibrium models of the Milky Way mass are biased high by the LMC

ABSTRACT Recent measurements suggest that the Large Magellanic Cloud (LMC) may weigh as much as 25 per cent of the Milky Way (MW). In this work, we explore how such a large satellite affects mass estimates of the MW based on equilibrium modelling of the stellar halo or other tracers. In particular, we show that if the LMC is ignored, the MW mass within 200 kpc is overestimated by as much as 50 per cent. This bias is due to the bulk motion in the outskirts of the Galaxy’s halo and can be, at least in part, accounted for with a simple modification to the equilibrium modelling. Finally, we show that the LMC has a substantial effect on the orbit Leo I which acts to increase its present-day speed relative to the MW. We estimate that accounting for a $1.5\times 10^{11} \, \mathrm{M}_\odot$ LMC would lower the inferred MW mass to $\sim 10^{12} \, \mathrm{M}_\odot$.

Service‐oriented routing with Markov space‐time graph in low earth orbit satellite networks

AbstractLow earth orbit (LEO) satellite network has been more and more widely used because of its advantages of low delay, low overhead, and flexible networking. However, the reliability and effectiveness of data transmission are affected by the specific characteristics of LEO satellite networks (LSN), such as time‐varying topology, uneven distribution of service demands, and multiple types of service. In this article, a service‐oriented routing with Markov space‐time graph (SOR‐MSG) in LSN is proposed to improve the reliability and effectiveness of information transmission. First, for the time‐varying topology, a Markov space‐time graph (MSG) model is constructed by calculating the connectivity time and connectivity probability between satellite node states. Then, in light of the uneven distribution of service demands, the space‐time factor (STF) is defined to balance the network load by scheduling the intersatellite link with lower loads. After that, we formulate the general routing problem caused by different quality of service (QoS) requirements for multimedia services and uneven load distribution and propose a multi‐QoS optimization objective function according to delay, remaining bandwidth, packet loss rate, and STF. Following this, based on the established MSG, the state transition rule and pheromone updating rule are optimally adjusted to select the next hop node, so as to finally determine the best information transmission path. Finally, the simulation results show that the SOR‐MSG algorithm can not only adapt to dynamically changing topologies and meet multiservice QoS requirements but also well balance the network load.

Multi-structure non-linear semi-parametric optimal weighting parameters estimation algorithm based on adaptive sparse representation deconstruction model and integrative COD comprehensive model

For the combined orbit determination (COD) satellite-network system which is made of GEO-IGSO-MEO satellite-constellation and LEO satellites, the satellites-trajectory are not precise enough, because the meticulous satellite dynamics model, credible observation data model and optimal parameters estimation method are not taking into consideration. The high-level adaptive sparse-deconstruction dynamics model, non-linear semi-parametric combined orbit determination comprehensive model is put forward. By using the above models, adaptive weighting iterative wavelets decomposition algorithm of sparse-representation deconstruction model and multi-structure non-linear semi-parametric optimization weighted estimation algorithm of integrative combined orbit determination comprehensive models are designed. Simulated calculation results show that results showed that the high-precision sparse representation method and the optimization model estimation method can improve COD precision, and when comprehensive model systematic & random error parameters and adaptive sparse-representation deconstruction model parameters are estimated by integrative nonlinear semi-parametric comprehensive model synchronously, COD ultimate trajectory calculation estimation precision can get significant improvement.

DebriSat fragment characterization: Quality assurance

The DebriSat project is a joint NASA and DoD project to generate data to update orbital debris models. The DebriSat test article, designed and fabricated to be representative of a modern-day LEO satellite, was subjected to a laboratory hypervelocity impact (HVI) test to emulate a catastrophic on orbit event. The items generated from the HVI test were collected and transported to the University of Florida for debris fragment extraction and characterization. During the characterization process, fragments are qualitatively (material, shape, color) and quantitatively (mass and size) assessed. The quantitative assessments are performed on mass balances and imaging systems by a student technicians that vary during the academic year. To ensure quality data and system operation by a group of varying technicians, a series of modified Gage Repeatability and Reproducibility (R&R) testing methods were created and implemented. This paper summarizes the DebriSat post-HVI activities and discusses the Gage R&R testing methods implemented to ensure high quality quantitative data.