LEO Satellite Research Articles

Tropospheric Attenuation in GeoSurf Satellite Constellations

In GeoSurf satellite constellations, any transmitter/receiver, wherever it is located, is linked to a satellite with zenith paths. We have studied the tropospheric attenuation predicted for some reference sites (Canberra, Holmdel, Pasadena, Robledo, and Spino d’Adda), which also set the meridian along which we have considered sites with latitudes ranging between 60° N and 60° S. At the annual probability of 1% of an average year, in the latitude between 30° N and 30° S, there are no significant differences between GEO slant paths and GeoSurf zenith paths. On the contrary, at 0.1% and 0.01% annual probabilities, large differences are found for latitudes greater than 30° N or 30° S. For comparing the tropospheric attenuation in GeoSurf paths with that expected in LEO highly variable slant paths, we have considered, as reference, a LEO satellite constellation orbiting in circular at 817 km. GeoSurf zenith paths “gain” several dBs compared to LEO slant paths. The more static total clear-sky attenuation (water vapor, oxygen, and clouds) in both GEO and LEO slant paths shows larger values than GeoSurf zenith paths. Both for rain and clear-sky attenuations, Northern and Southern Hemispheres show significant differences.

A Blockchain-Based Authentication Protocol Using Cryptocurrency Technology in LEO Satellite Networks

With the rapid development of satellite technology and the high transmission efficiency of LEO satellites, LEO satellite communication has received increasing attention. However, the frequent switching of satellite-earth links imposes a great challenge in LEO communication authentication. To tackle this challenge, this paper proposes a Blockchain-based Authentication Protocol Using Cryptocurrency Technology (BAPC), which solves the problem of a long pause time of satellite services caused by user access authentication in a scenario of frequent switching between satellites and ground users. First, we design three stages of the authentication process and introduce the cryptocurrency technology. Using currency transactions as the certificate of authentication improves not only the security of authentication, but also the efficiency of switching authentication. Next, in the network topology, the satellite cluster is divided into multiple regions to improve the efficiency of block consensus. Finally, the protocol is tested through extensive NS2-based simulations, and the results verify that BAPC can greatly shorten the response time of switching authentication and significantly reduce the time of block generation and the network throughput. As the number of users increases, the block generation time and network throughput can be further reduced.

The performance analysis of NOMA in LEO satellite rain attenuation and fading hybrid channel

SummaryIn the fifth‐generation (5G) and future sixth‐generation (6G) networks, improving spectral efficiency and system capacity is still the main concern. Adding LEO satellite to the construction of 5G and 6G can make the network structure three‐dimensional, which lets the network construction get rid of the limitation of ground space propagation distance and makes the wider area enjoy the convenience of 5G and 6G. However, due to the large link distance between space and the ground, the communication of LEO satellite in Ka band is greatly affected by rain attenuation and shadow fading. In order to improve the ergodic capacity of LEO satellite downlink, this paper attempts to apply nonorthogonal multiple access (NOMA) to hybrid channels with rainfall fading and shadow fading. In the simulation results, the ergodic capacity of orthogonal frequency division multiple access (OFDMA) and NOMA is compared, and it is found that the system capacity of hybrid channel can be improved by increasing the power allocation factor of NOMA. The experiments have studied the influence of LEO satellite's orbital height, fading degree, and transmission power in the communication link on the performance of LEO satellite system in this paper. The experimental results show that the lower the orbit height is, the better system performance will become under the same fading degree. Moreover, the energy consumed gradually decreases with the transmission power becoming small.

Reduction of side lobes in the entire azimuth plane in a planar elliptical array antenna

SummaryA novel synthesis method to reduce the maximum side lobe in the entire azimuth plane and for achieving a desired value of directivity of a concentric elliptical array antenna is addressed in this paper. Three well‐performing meta‐heuristic optimization algorithms, teaching learning‐based optimization (TLBO), symbiotic organism search (SOS), and quantum particle swarm optimization (QPSO), are employed to optimize the cost function and to obtain the desired radiation pattern. Different simulation‐based experiments are performed to obtain the best possible set of angular positions and the distribution of isotropic antennas across the ellipses by rigorously maintaining non‐overlapping constraints. The major benefit of the proposed design is the deprecation of interference in all phi planes. The statistical analysis of the simulation results demonstrate perceptible improvement compared with that of a uniformly spaced concentric elliptical array and hence show the efficiency of the proposed algorithms. In both simulation studies, the results obtained using TLBO, SOS, and QPSO are compared. Analysis of the results exhibits that for the stated objective, the TLBO‐ and SOS‐based side lobe reduction approach performs superior to QPSO method. Proposed multi‐objective research work could lead to reduce payload and can simultaneously achieve isoflux coverage in entire azimuth plane on the earth surface which can essentially be utilized in (Low Earth Orbit) LEO and (Geostationary Earth Orbit) GEO satellites applications.

Design Coverage Optimization Based on Position of Constellations and Cost of the Launch Vehicle

This research will analyze the tradeoffs between coverage optimization based on Position dilution of precision (PDOP) and cost of the launch vehicle. It adopts MATLAB and STK tools along with multiple objective genetic algorithms (MOGA) to explore the trade space for the constellation designs at different orbital altitudes. The objective of optimal design solutions is inferred to determine the economic and efficient LEO, MEO, HEO or hybrid constellations and simulation results are presented to optimize the design of satellite constellations. The benefits of this research are the optimization of satellite constellation design, which reduces costs and increases regional and global coverage with the least number of satellites. The result of this project is the optimization of the number of constellation satellites in several orbital planes in LEO orbit. Validations are based on reviewing the results of several simulations. The results of graphs and tables are presented in the last two sections and are taken from the results of several simulations.

Improved LORA Modulation Output in LEO Satellite Internet of Things

Improved LORA Modulation Output in LEO Satellite Internet of Things

Self-deployable drag sail folded nine times

• Folding method for 9 folds of the Highly Flexible Frames and the ability to deploy. • Experiments with the HFF in the pocket reviled the need for heat treating the steel. • Uncoiling of the HFF accrued, this was redeemed with a tight pocket depth. Increased focus on space debris push regulations by the UN and thereby the demand for debris removal systems to be implemented in future spacecraft. This research focuses on debris removal of post-mission satellites in LEO using drag augmented deorbit into the earth's atmosphere. By using gossamer sails (drag sails), aerodynamic breaking can effectively be achieved in LEO up to 700 km. The presented work supplements the research performed in the H2020 project Technologies for Self-Removal of Spacecraft (TeSeR), in which the Self-Deployable Deorbiting Space Structure (SDSS) has been further developed. It is devised how to obtain a self-deployable drag sail folded nine times for use in debris removal for a 6U CubeSat, i.e. an SDSS/9. Achieving nine folds of Highly Flexible Frame (HFF) is essential to maximize the drag sail area when it is unfolded and hereby increasing drag force. The nine times folded HFF has been modeled in computer simulations and demonstrated in a lab. From lab-based research, several issues have been identified when folding the HFF nine times. Of these, two main issues are addressed in this paper, i.e. relaxation and uncoiling. When folded nine times, the von Mises stresses computed by FEM reach 1857 MPa. Combined with residual stresses, this is causing yield and relaxation in the HFF and reducing the deployability. A minimum drag sail diameter is identified for this setup, and the high-strength stainless steel should be heat treated to relieve residual stresses before folding. A side-mounted design is chosen for the configuration of the SDSS. This reduces friction during the release and deployment of the drag sail. From thorough testing, it is observed that the uncoiling of the HFF during storage in the pocket significantly reduces the deployability of the SDSS. To mitigate both radial and axial uncoiling of the HFF in the pocket, the pocket diameter and height should be designed with an exact fit to the folded diameter and height of the ideally folded HFF with the drag sail included. Based on this research, a new design of the SDSS/9 for CubeSats is devised, and preliminary testing indicates good consistencies more test is necessary to determine the reliability of the side mounted SDSS. Hence, from the research, it is concluded that SDSS/9 is a feasible solution for a low-cost add-on debris removal system. Furthermore, the side-mounted design allows integration with additional collision protection of the spacecraft.

Distributed MIMO System Design and Channel Capacity Analysis Based on Polar Orbit LEO Constellation

Distributed MIMO System Design and Channel Capacity Analysis Based on Polar Orbit LEO Constellation

Adaptive Predictive Functional Control of X-Y Pedestal for LEO Satellite Tracking Using Laguerre Functions

In this paper, Predictive Functional Control (PFC) is used for X-Y pedestal control for LEO satellite tracking. According to the nonlinear characteristics of the X-Y pedestal and pedestal model variation caused by its operating point change, the use of system identification algorithm, which is based on special types of orthonormal functions known as Laguerre functions, is presented. This algorithm is combined with PFC to obtain a novel adaptive control algorithm entitled Adaptive Predictive Functional Control (APFC). In this combination, Laguerre functions are utilized for system identification, while the PFC is the control law. An interesting feature of the proposed algorithm is its desirable performance against the interference effect of channel X and channel Y. The proposed APFC algorithm is compared with Proportional Integral Derivative (PID) controller using simulation results. The results confirm that the proposed controller improves the performance in terms of the pedestal model variations; that is, the controller is capable of adapting to the model changes desirably.

Multilayer radiation shield for satellite electronic components protection

In this paper, various multi-layer shields are designed, optimized, and analyzed for electron and proton space environments. The design process is performed for various suitable materials for the local protection of sensitive electronic devices using MCNPX code and the Genetic optimization Algorithm. In the optimizations process, the total ionizing dose is 53.3% and 72% greater than the aluminum shield for proton and electron environments, respectively. Considering the importance of the protons in the LEO orbits, the construction of the shield was based on designing a proton source. A sample shield is built using a combination of Aluminum Bronze and molybdenum layers with a copper carrier to demonstrate the idea. Comparisons of radiation attenuation coefficient results indicate a good agreement between the experimental, simulation, and analytical calculations results. The good specifications of the proposed multi-layer shield prove their capability and ability to use in satellite missions for electronic device protection.

The Effect of Atmospheric Drag Force on the Elements of Low Earth Orbital Satellites at Minimum Solar Activity

Researching and modeling perturbations is essential in astrodynamics because it gives information on the deviations from the satellite's normal, idealized, or unperturbed motion. Examined the impact of non-conservative atmospheric drag and orbital elements of low-earth-orbit satellites under low solar activity. The study is consisting of parts, the first looks at the effects of atmospheric drag on LEO satellites different area to mass ratios, and the second looks at different inclination values. Modeling the impacts of perturbation is included in each section, and the final portion determines the effects of atmospheric drag at various node values. The simulation was run using the Celestial Mechanics software system's SATORB module (Beutler, 2005), which solves the perturbation equations via numerical integration. The findings were examined using Matlab 2012. Conclusion that the impacts are stronger for retrograde orbits, which is due to the fact that the satellite moves in the opposite direction. The atmospheric drag effects for all orbital elements were increased by increasing the area to mass ratio. When the node value rises, the size parameter changes slightly, but the other orbital elements change. At varying inclinations, it is found that the changes in orbital elements due to atmospheric drug.

A Dynamic Service Reconfiguration Method for Satellite–Terrestrial Integrated Networks

Satellite–terrestrial integrated networks (STINs) are regarded as a promising solution to meeting the demands of global high-speed seamless network access in the future. Software-defined networking and network function virtualization (SDN/NFV) are two complementary technologies that can be used to ensure that the heterogeneous resources in STINs can be easily managed and deployed. Considering the dual mobility of satellites and ubiquitous users, along with the dynamic requirements of user requests and network resource states, it is challenging to maintain service continuity and high QoE performance in STINs. Thus, we investigate the service migration and reconfiguration scheme, which are of great significance to the guarantee of continuous service provisioning. Specifically, this paper proposes a dynamic service reconfiguration method that can support flexible service configurations on integrated networks, including LEO satellites and ground nodes. We first model the migration cost as an extra delay incurred by service migration and reconfiguration and then formulate the selection processes of the location and migration paths of virtual network functions (VNFs) as an integer linear programming (ILP) optimization problem. Then, we propose a fuzzy logic and quantum genetic algorithm (FQGA) to obtain an approximate optimal solution that can accelerate the solving process efficiently with the benefits of the high-performance computing capacity of QGA. The simulation results validate the effectiveness and improved performance of the scheme proposed in this paper.

Machine Learning-Based Resource Allocation in Satellite Networks Supporting Internet of Remote Things

Satellite networks have been regarded as a promising architecture for supporting the Internet of remote things (IoRT) due to their advantages of wide coverage and high communication capacity in remote areas, which further promotes the development of the satellites for IoRT networks (SIoRTNs). The effectiveness of multi-dimensional resource collaboration has significant impacts on the IoRT data downloading performance. However, the environment ’ s dynamics, e.g., channel conditions and solar infeed process, are unknown in practical scenarios, which poses daunting challenges in making efficient utilization of multi-dimensional resources. Motivated by this fact, we model the joint resource scheduling and IoRT data scheduling problem with the aim of maximizing the amount of the IoRT data of the overall network by applying the model-free reinforcement learning framework. To overcome the limitations of traditional reinforcement learning algorithms, we propose several feature functions by investigating the natural attributes of the multi-dimensional resources of the SIoRTNs, and further exploit the concept of function approximation to approximate the expected downloaded IoRT data given the network state. Furthermore, we propose a state-action-reward-state-action (SARSA) based actor-critic reinforcement learning (SACRL) resource allocation strategy to achieve the optimal resource allocation and IoRT data scheduling with casual information at LEO satellites. Simulations validate the convergence property and the effectiveness of the proposed SACRL algorithm in terms of the amount of the downloaded IoRT data. Particularly, we investigate the impact of typical network parameters on network performance to further provide guidance for future SIoRTN system design.

Retrieval of Raindrop Size Distribution Using Dual-Polarized Microwave Signals from LEO Satellites: A Feasibility Study through Simulations.

In this paper, a novel approach for raindrop size distribution retrieval using dual-polarized microwave signals from low Earth orbit satellites is proposed. The feasibility of this approach is studied through modelling and simulating the retrieval system which includes multiple ground receivers equipped with signal-to-noise ratio estimators and a low Earth orbit satellite communicating with the receivers using both vertically and horizontally polarized signals. Our analysis suggests that the dual-polarized links offer the opportunity to estimate two independent raindrop size distribution parameters. To achieve that, the vertical and horizontal polarization attenuations need to be measured at low elevation angles where the difference between them is more distinct. Two synthetic rain fields are generated to test the performance of the retrieval. Simulation results suggest that the specific attenuations for both link types can be retrieved through a least-squares algorithm. They also confirm that the specific attenuation ratio of vertically to horizontally polarized signals can be used to retrieve the slope and intercept parameters of raindrop size distribution.

Lagrange Point Missions: The Key to next Generation Integrated Earth Observations. DSCOVR Innovation

A new perspective for studying Earth processes has been soundly demonstrated by the Deep Space Climate Observatory (DSCOVR) mission. For the past 6 years, the first Earth-observing satellite orbiting at the Lagrange 1 (L1) point, the DSCOVR satellite has been viewing the planet in a fundamentally different way compared to all other satellites. It is providing unique simultaneous observations of nearly the entire sunlit face of the Earth at a relatively high temporal resolution. This capability enables detailed coverage of evolving atmospheric and surface systems over meso- and large-scale domains, both individually and as a whole, from sunrise to sunset, under continuously changing illumination and viewing conditions. DSCOVR’s view also contains polar regions that are only partially seen from geostationary satellites (GEOs). To exploit this unique perspective, DSCOVR instruments provide multispectral imagery and measurements of the Earth’s reflected and emitted radiances from 0.2 to 100 µm. Data from these sensors have been and continue to be utilized for a great variety of research involving retrievals of atmospheric composition, aerosols, clouds, ocean, and vegetation properties; estimates of surface radiation and the top-of-atmosphere radiation budget; and determining exoplanet signatures. DSCOVR’s synoptic and high temporal resolution data encompass the areas observed during the day from low Earth orbiting satellites (LEOs) and GEOs along with occasional views of the Moon. Because the LEO and GEO measurements can be easily matched with simultaneous DSCOVR data, multiangle, multispectral datasets can be developed by integrating DSCOVR, LEO, and GEO data along with surface and airborne observations, when available. Such datasets can open the door for global application of algorithms heretofore limited to specific LEO satellites and development of new scientific tools for Earth sciences. The utility of the integrated datasets relies on accurate intercalibration of the observations, a process that can be facilitated by the DSCOVR views of the Moon, which serves as a stable reference. Because of their full-disc views, observatories at one or more Lagrange points can play a key role in next-generation integrated Earth observing systems.

Inter-satellite load balancing routing algorithm for LEO satellite constellation based on regional-traffic-detour

Inter-satellite load balancing routing algorithm for LEO satellite constellation based on regional-traffic-detour

The new generation of attitude determination sensor for LEO satellite based on Induced electric field

Abstract For carrying out their missions, many satellites use closed-loop attitude control. For closing the control loop, they use several sensors, such as sun sensors, magnetometer, and star tracker. Sun sensors are not operational during the eclipse; therefore, one of the observed vectors is lost. For this reason, attitude determination in eclipse can be a challenging issue for control engineers. This paper presents a novel idea for producing a new generation of sensors that can measure the induced electric field vector not only in eclipse but also in the whole orbit. This electric field comes from the high velocity of the spacecraft in the magnetic field of the Earth. This vector is always perpendicular to the magnetic field; thus, it is never aligned with the magnetic vector and never causes singularity and accuracy decreasing. The induced electric field is measured by three RC circuits that are actuated by sinusoidal voltage. The dielectrics of the capacitors are made of ferroelectric materials; therefore, the induced voltage affects the permittivity and voltage of the capacitor. By measuring and calibrating this effect in three perpendicular axes can measure the three components of the electric field vector. The theory of the proposed sensor has been developed, and simulation studies validate the results.

The future of data communication in Aviation 4.0 environment

Currently experienced the dawn of the Aviation 4.0 era is transforming the contemporary technological environment, throughout the whole aeronautical industry, by creating cyber-physical systems. Following the evolutionary path, incorporating advanced automated and first autonomy systems, the applications involved are becoming increasingly data- oriented. The need for progressive data analytics, massive adoption and operation of IoT devices, delivering advanced monitoring and machine learning opportunities, building the core structure for artificial intelligence, will put a significant pressure on data communication and connectivity itself. In the near future, the problems may especially arise in datalink used in civil aviation. This research paper briefly studies the contemporary systems used for datalink, determines dominant aspects of Aviation 4.0 and their overall impact on the performance requirements of the data communications network, and proposes the possible solution to the problematics, with newly emerging LEO satellite mega-constellations providing Internet connectivity. The conclusion of this paper highlights the requirements for future data communication systems and determines whether the existing and proposed datalink subnetwork technologies are capable of meeting the demands established by Aviation 4.0.

Vehicle detection base on Road Segmentation for surveillance satellites video

With the development of data acquisition ability, the LEO satellites can work with a surveillance camera on board by focusing a particular area for dozens of seconds, so it drives us to develop some applications based on this data. In this paper, a data preparation method named DERS (Density Estimation based Road Segmentation) is proposed to divide the road from background to reduce the worse impact from relative-motion and then improve the precession and recall for vehicles for surveillance satellite video sequence. DERS has three main steps: frame difference, morphology, pyramid iteration, segmentation. Our experiments with the satellite videos from SkySat-1, and compared between Gaussian Mixture Model (GMM) and GMM with Ders shows that the precision rate and recall has improved of the traditional method with Ders, the precision of GMM with Ders has been improved from 64.42% to 88.71, the recall of GMM with Ders is from 76.21% to 74.16%, and the F-Score has been improved from 69.82% to 80.79%.

A satellite-based quantum key distribution using decoy-state protocol

An ideal QKD implementation that provides the promising unconditional security using single photon laser source is not practically easy, also sending these photons over a fiber channel affects the maximum distance of link up to few hundreds of kilometers because of the receiver’s detectors losses. Therefore, the achievement of a global quantum network is not easy, and the need to use LEO satellites [1,2] for establishing quantum links makes the job easier as quantum free space link provides much less losses to the link than fiber links. Nowadays, a quantum communication link can be established by satellites through free space. in this paper, we propose an implementation [3] of a satellite-based quantum key distribution using decoy-state protocol [4], we then compare this protocol with the BB-84 protocol [3] against security and the key length of the generated shared key.