Cooperative Satellite Research Articles

Dynamic Inversion Method of Calculating Large-Scale Urban Building Height Based on Cooperative Satellite Laser Altimetry and Multi-Source Optical Remote Sensing

Building height is a crucial indicator when studying urban environments and human activities, necessitating accurate, large-scale, and fine-resolution calculations. However, mainstream machine learning-based methods for inferring building heights face numerous challenges, including limited sample data and slow update frequencies. Alternatively, satellite laser altimetry technology offers a reliable means of calculating building heights with high precision. Here, we initially calculated building heights along satellite orbits based on building-rooftop contour vector datasets and ICESat-2 ATL03 photon data from 2019 to 2022. By integrating multi-source passive remote sensing observation data, we used the inferred building height results as reference data to train a random forest model, regressing building heights at a 10 m scale. Compared with ground-measured heights, building height samples constructed from ICESat-2 photon data outperformed methods that indirectly infer building heights using total building floor number. Moreover, the simulated building heights strongly correlated with actual observations at a single-city scale. Finally, using several years of inferred results, we analyzed building height changes in Tianjin from 2019 to 2022. Combined with the random forest model, the proposed model enables large-scale, high-precision inference of building heights with frequent updates, which has significant implications for global dynamic observation of urban three-dimensional features.

LEO Satellite Navigation Based on Optical Measurements of a Cooperative Constellation

Autonomous, anti-jamming, and high-precision satellite navigation are of great importance to current and future space technologies. This paper proposes a cooperative constellation navigation system for low Earth orbit (LEO) satellites that use only the optical measurements of cooperative satellites. Based on photometry, an optical transmission link model of the system is built. With the pixel coordinates of the cooperative satellites on the optical images, the line of sight (LoS) vectors of the cooperative satellites with respect to the LEO spacecraft are first calculated, and a single-point positioning method based on the LoS vectors’ inner products is proposed. The single-point positioning results are then fed into a least square batch filter to estimate a high-precision spacecraft orbit. Simulations are conducted to evaluate the potential navigation accuracy. With a cooperative satellite ephemeris error of 100 m and an optical measurement noise level of 5 arcsecs, position accuracies of single-point positioning and dynamic orbit determination in the order of hundreds of meters and eight meters, respectively, are realized. In addition, the influences of the orbital altitude of the cooperative constellation, the ephemeris error of the cooperative satellite, the noise level of the optical measurements, and the Earth’s gravitational model on navigation accuracy are investigated via comparative simulations.

Optimized Higher-Order Polarization Weight Incremental Selective Decoding and Forwarding in Cooperative Satellite Sensor Networks

An optimized higher-order polarization weight (HPW) incremental selective decoding and forwarding (ISDF) scheme is proposed for cooperative transmissions in satellite sensor networks (SSNs). First, an HPW method is designed with subchannel power allocation in encoding to enhance the antiinterference. Second, a cooperative decision in the destination is used to avoid error propagation for better outage probability (OP) and bit error rate (BER) performance. It switches between direct and cooperative transmissions alternatively by channel state information (CSI). Finally, the HPW coding information, cyclic redundancy codes (CRCs), and four special frame structures of polar subcodes are jointly fast successive cancellation list (FSCL) decoded to improve efficiency and BER performance. Finally, we apply the optimized polarization encoding and decoding to the relay system to form a new ISDF relay system for better coding efficiency, BER, and OP performance. Simulation results show that the proposed scheme obtains approximately 0.8 and 1 dB performance gains at OP of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${{10}^{-{2}}}$ </tex-math></inline-formula> and BER of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${{10}^{-{6}}}$ </tex-math></inline-formula> , respectively, when compared with those of the current ISDF scheme. Therefore, the cooperative scheme possesses efficient decoding and cooperation, which endows it a promising candidate relay scheme in SSNs.

Efficient Polar Coded Selective Decode-and-Forward with Cooperative Decision Threshold in Cooperative Multi-Relay Transmissions

In some satellite Internet of Things (IoT) devices with terrain shielding, the qualities of the direct source-destination (S-D) channel are poor, requiring cooperative communications with multi-relays to be employed. In order to solve error propagation of current decode-and-forward (DF) on such occasions, an efficient polar coded selective decode-and-forward (SDF) cooperation method is proposed with a new decision threshold derived from channel state information (CSI). First, the proposed threshold is derived from the CSI by exploiting the channel gain ratio of optimal relay-destination link (R-D) with source-relay (S-R) link. The above R-D link possesses good channel quality among all links in the system. Second, when the channel gain ratio of certain relay links is larger than the aforementioned decision threshold, the source and all these relays cooperatively send messages together to the destination to accomplish perfect SDF transmission. Otherwise, all relays are frozen and the messages are directly transmitted through the S-D link. If it fails anyway, a retransmission is subsequently tried in the next transmission cycle. In addition, a polar code for fading channels is designed and adaptively adjusted to a proper code rate according to channel quality to attain good bit error rate (BER) performance. Simulation results show that the proposed scheme achieves about 0.9 and 0.5 dB gain at BER of 10-4, respectively, in multi-relay cooperative communications with multi-path fading channels compared with those of non-cooperation and existing polar coded cooperation channels. Therefore, the proposed polar coded SDF (PCSDF) scheme can improve both the BER and the outage probability (OP) performance in multi-relay cooperative systems, making it quite suitable for heterogeneous network applications in cooperative satellite IoT systems involving sixth-generation (6G) communications.

A blockchain-based and privacy-preserved authentication scheme for inter-constellation collaboration in Space-Ground Integrated Networks

Space-Ground Integrated Networks (SGINs) make it convenient for users to access services anywhere. In the space segment, satellite constellations can cooperate to provide better space services. However, due to the lack of trust among different constellations, communication security and privacy protection are important issues that need to be solved during inter-constellation cooperation. In this work, with recent advances of blockchain, we present a trusted and privacy-preserved authentication scheme for inter-constellation collaboration. To preserve privacy, we design permanent and temporary identities for each satellite. The permanent one is used for inner-constellation communication, and the temporary identity is for inter-constellation cooperation, respectively. Meanwhile, satellites generate temporary identities for themselves to avoid privacy leakage. A consortium blockchain is introduced for sharing information among cooperative satellite constellations. Furthermore, to achieve efficient authentication under limited resources, a replica storage node method is proposed, where well-resourced satellites cache the replicated information shared through the blockchain. The replica storage node selection is formulated as an integer programming problem and solved with a branch and bound algorithm. Security analysis, including formal analysis using BAN Logic and informal verification, shows that the proposed authentication scheme is secure against various potential attacks. A comparative analysis among the proposed scheme and other blockchain-based schemes shows that the proposed scheme achieves efficiency in signaling, computation, and communication overheads with more functionality attributes. In addition, evaluations also demonstrate that the proposed on-board caching scheme achieves low communication latency and storage cost.

Analysis of binate hop cascaded satellite terrene link with correlated LOS constituents

In this study, a binate hop cooperative satellite–terrene link with correlated line-of-sight (LOS) components has been considered. The satellite–terrene link is assumed to follow shadowed-Rician fading. Specifically, higher-order moments of the considered system have been derived. Using the expression of higher-order moments, the expressions of the amount of fading and channel quality estimation index of the considered cooperative complex have been obtained. The symbol error rate of the considered cooperative satellite–terrene link for M-ary phase-shift keying constellation has been derived and the denouement of signal-to-noise ratio and inclination angle has been scrutinised as well. Moreover, outage probability and average channel capacity of the considered system have been derived with the help of the Meijer-G approach. It has been manifested by simulation and analysis that the performance of the considered system enhances with the inflation in the aggregate of antennas and inclination angle.

Space of solutions to ocean surface wind measurement using scatterometer constellations

Satellite wind vector data are integral to atmospheric models and forecasts, but current measurement limitations make some synoptic, mesoscale activities difficult to observe. Using miniaturized electronics and advanced deployable mechanisms, new satellite wind scatterometers may be possible that increase spatial, temporal, and wind resolution and coverage. We propose a simple parametric model of the space of satellite wind scatterometer designs, their performances, and the transformation between design and performance, together called a solution space model. We explore two applications of this model: understanding how advances have expanded the design space and searching for alternative approaches to satellite wind scatterometry. Recent advances enable a greater capability-to-volume ratio, which enables constellations of small, low-cost scatterometers that co-operate in a variety of modes. We present two example concepts for constellations of co-operative satellite wind scatterometers. We estimate that a constellation of CubeSat scatterometers may affordably measure global ocean vector winds every three hours.

The Application of Power-Domain Non-Orthogonal Multiple Access in Satellite Communication Networks

Satellite communication networks are expected to be indispensable as part of an integrated complement for the upcoming 5G networks since they can provide the most comprehensive coverage and reliable connection for areas where are economically unviable and/or difficult to deploy terrestrial infrastructures. Meanwhile, the power-domain non-orthogonal multiple access (NOMA), which can serve multiple users simultaneously within the same time/frequency block, has been viewed as another promising strategy used in the 5G network to provide high spectral efficiency and resource utilization. In this paper, we introduce a general overview of the application of the NOMA to various satellite architectures for the benefits of meeting the availability, coverage, and efficiency requirements targeted by the 5G. The fundamental and ubiquitous features of satellite link budget are first reviewed. Then, the advantage and benefit of introducing the NOMA scheme in various satellite architectures, such as conventional downlink/uplink satellite networks, cognitive satellite terrestrial networks, and cooperative satellite networks with satellite/terrestrial relays, are provided, along with the motivation and research methodology for each scenario. Finally, this paper reviews the potential directions for future research.

Joint cooperative spectrum sensing and channel selection optimization for satellite communication systems based on cognitive radio

Cognitive radio has attracted considerable attention because of its ability to make full use of the available spectrum resources for wireless terrestrial communication networks. In addition, the satellite communication scenario, which requires a transparent air interface to integrated/hybrid Satellite-Terrestrial communication systems and provides a supplement for other multimedia services, will cause frequency scarcity. Satellite communication systems based on cognitive radio are available under scenarios that involve transmission with changing communications. In this paper, a cooperative spectrum-sensing algorithm based on a time or bandwidth-based cooperative spectrum-sensing model of an integrated/hybrid cooperative satellite communication system is proposed. Moreover, the concept of weighted cooperative spectrum sensing is introduced. Compared with the traditional single-user spectrum-sensing algorithm, the cooperative spectrum sensing is able to cope with the interference to the primary user caused by a secondary user better. In addition, multiple earth stations that use some part of the bandwidth cooperatively to perform spectrum sensing throughout the whole frame can detect the presence of primary user in time. The satellite component combines the sensing results from earth stations to reach a final decision, and the optimal combination weights to maximize the detection probability of the secondary user are obtained. Numerical results that demonstrate the performance of the proposed algorithm are presented. Copyright © 2015 John Wiley & Sons, Ltd.

Vision-based localization for on-orbit servicing of a partially cooperative satellite

This paper proposes ground-in-the-loop, model-based visual localization system based on transmitted images to ground, to aid rendezvous and docking maneuvers between a servicer and a target satellite. In particular, we assume to deal with a partially cooperative target, i.e. passive and without fiducial markers, but supposed at least to keep a controlled attitude, up to small fluctuations, so that the approach mainly involves translational motion. For the purpose of localization, video cameras provide an effective and relatively inexpensive solution, working at a wide range of distances with an increasing accuracy and robustness during the approach. However, illumination conditions in space are especially challenging, due to the direct sunlight exposure and to the glossy surface of a satellite, that creates strong reflections and saturations and therefore a high level of background clutter and missing detections. We employ a monocular camera for mid-range tracking (20–5m) and stereo camera at close-range (5–0.5m), with the respective detection and tracking methods, both using intensity edges and robustly dealing with the above issues. Our tracking system has been extensively verified at the facility of the European Proximity Operations Simulator (EPOS) of DLR, which is a very realistic ground simulation able to reproduce sunlight conditions through a high power floodlight source, satellite surface properties using multilayer insulation foils, as well as orbital motion trajectories with ground-truth data, by means of two 6 DOF industrial robots. Results from this large dataset show the effectiveness and robustness of our method against the above difficulties.

Navigation Solution to Maneuver a Spacecraft Relative to a Sphere Centered on a Cooperative Satellite

A differential correction algorithm is presented to deliver an impulsive maneuver to a satellite to place it within a sphere, with a user defined radius, centered around a non-maneuvering satellite within a constrained time. The differential correction algorithm develops and utilizes the State Transition Matrix along with the Equations of Motion and multiple satellite׳s state information to determine the optimum trajectory to achieve the desired results. The results from the differential correction algorithm are very accurate for prograde orbits, as presented. The results allow for orbit design trade-offs, including satellites׳ initial inclinations, semi-major axes, as well as the ballistic coefficients. The results also provide an empirical method to determine the optimum ΔV solution for the provided problem. Understanding that the minimum fuel solution lies with a semi-major axis ratio of 1, a very accurate empirical approximation is presented for semi-major axis ratio values less than and greater than 1. This work ultimately provides the generalized framework for applying the algorithm to a unique user defined maneuvering spacecraft scenario.

Prospects and challenges of context-aware multimedia content delivery in cooperative satellite and terrestrial networks

Cooperative satellite cells and terrestrial wireless communication networks (comprising macrocells, picocells, and the Internet) are much anticipated access technologies to enable users to seamlessly access rich multimedia content (e.g., TV broadcasting, VoD streaming, and other services) on their devices. Furthermore, context awareness has become popular to accompany these services not only to enhance the users' perceived service quality but also to improve the overall utilization of such cooperative networks. However, delivering context-aware multimedia content through these cooperative networks is associated with a significant research challenge due to the inherently different satellites and terrestrial networks technologies. For example, to provide context-specific TV programs to a user, a satellite needs to adopt unicast-style delivery. This may be an expensive operation since satellites are intrinsically useful for broadcasting or multicasting services to a wide audience. In contrast, terrestrial communication networks can be better suited to perform unicast-based context-aware content delivery. In this article, we address these challenges, and propose a dynamic bandwidth allocation method to effectively utilize the satellite and terrestrial networks for providing context-aware contents to many users. Computer-based simulation results are presented to demonstrate the effectiveness of our proposed method.

An Energy-Efficient Coding in Mobile Satellite Communications

Diversity gains are believed to improve the transmission reliability in fading mobile satellite channels. Considering that the traditional Space-Time Coding (STC) is not suitable for the cooperative mobile satellite communication, in this paper a new cooperative mobile satellite communication system is proposed based on the Dynamic Space-Time Coding (D-STC). The transmit energy of the propose scheme is saved by avoiding forwarding erroneous signals in cooperative users. Meanwhile, the system benefits from diversity gains and the transmission is robust. Finally, the analytical result is validated by numerical simulations.

Relative Navigation of Satellites in Formation Using Monocular Model-Based Vision

Abstract This paper describes the techniques of navigation of formation flying satellites at geostationary altitudes using monocular model-based vision. The uniqueness of this method is in the very fact that it utilizes the circular model features on the co-operative satellite in the formation. There are many papers on the point or line features but no known paper addresses the application of the circular features with regard to co-operative formation flying. This novel circular features based technique is applied to determination of the 3-D position of a satellite in the formation. This novel methodology can be used to determination of orientation of the satellites as well. The signal from the model-based vision sensor is used to control the relative navigation and control of the two satellites in the formation in geostationary orbits.

Distributed estimation and control of multi-agent systems in uncertain environment

Due to the wide applications in wireless sensor networks, multi-robot cooperative control and satellite formation flying, etc., distributed control and estimation of multi-agent systems (MASs) are now a hot topic in the system control community. In practice, when carrying out distributed tasks, MASs are often subject to various uncertainties, which can make significant macro-influence to the whole systems via affecting each agents microscopic decisions. The interaction among uncertainties and distributed information pattern may bring essential difficulty to the design and analysis of MASs. This paper is aimed at seeking more robust and more effective distributed estimation and control protocols to achieve global estimation and control tasks under various uncertainties including stochastic noises, signal loses, quantization errors and unknown system structures, etc. Specifically, distributed estimation, distributed control and distributed adaptive control are investigated.

An Approach to Cooperative Satellite Communications in 4G Mobile Systems

In this paper we focus our attention in the main two methods of Cooperative Communications: Decode and Forward, and Amplify and Forward, and how they can be used in a new concept of Cooperative Satellite Communications. We present an analysis of both in terms of Symbol Error Rate and Power Allocation and analyze which would be more efficient when relaying information from the satellite to a mobile node in the terrestrial network. We propose a protocol that combines Selective and Incremental Relaying to optimize the cooperative scheme.

COMPARATIVE PHYLOGENETIC ANALYSIS OF MALE ALTERNATIVE REPRODUCTIVE TACTICS IN RAY-FINNED FISHES

Using comparative phylogenetic analysis, we analyzed the evolution of male alternative reproductive tactics (MARTs) in ray-finned fishes (Actinopterygii). Numerous independent origins for each type of MART (involving sneaker males, female mimics, pirates, and satellite males) indicate that these behaviors have been highly labile across actinopterygiian evolution, consistent with a previous notion that convergent selection in fishes can readily mold the underlying suites of reproductive hormones into similar behaviors. The evolutionary appearance of MARTs was significantly correlated with the presence of sexually selected traits in bourgeois males (P = 0.001) but not with the presence of male parental care. This suggests that MARTs often arise from selection on some males to circumvent bourgeois male investment in mate monopolization, rather than to avoid male brood care per se. We found parsimony evidence for an evolutionary progression of MARTs wherein sneaking is usually the evolutionary precursor to the presumably more complex MARTs of female mimicry and cooperative satellite behavior. Nest piracy appears not to be part of this evolutionary progression, possibly because its late onset in the life cycle of most ray-finned fishes reduces the effects of selection on this reproductive tactic.

COMPARATIVE PHYLOGENETIC ANALYSIS OF MALE ALTERNATIVE REPRODUCTIVE TACTICS IN RAY-FINNED FISHES

Using comparative phylogenetic analysis, we analyzed the evolution of male alternative reproductive tactics (MARTs) in ray-finned fishes (Actinopterygii). Numerous independent origins for each type of MART (involving sneaker males, female mimics, pirates, and satellite males) indicate that these behaviors have been highly labile across actinopterygiian evolution, consistent with a previous notion that convergent selection in fishes can readily mold the underlying suites of reproductive hormones into similar behaviors. The evolutionary appearance of MARTs was significantly correlated with the presence of sexually selected traits in bourgeois males (P = 0.001) but not with the presence of male parental care. This suggests that MARTs often arise from selection on some males to circumvent bourgeois male investment in mate monopolization, rather than to avoid male brood care per se. We found parsimony evidence for an evolutionary progression of MARTs wherein sneaking is usually the evolutionary precursor to the presumably more complex MARTs of female mimicry and cooperative satellite behavior. Nest piracy appears not to be part of this evolutionary progression, possibly because its late onset in the life cycle of most ray-finned fishes reduces the effects of selection on this reproductive tactic.

Geotail Mission to explore Earth's magnetotail

The cooperative satellite mission, Geotail, was launched recently by the Institute of Space and Astronautical Science of Japan and NASA. This satellite will investigate the magnetotail region of the Earth's magnetosphere, reaching distances as large as 220 RE (1 Earth radii = 6378 km). In this orbit, Geotail will yield an increased understanding of fundamental processes taking place in this relatively unexplored portion of geospace.The Geotail satellite was designed and developed by ISAS and was launched by NASA on a DELTA II expendable launch vehicle on July 24, carrying scientific instruments provided by both space agencies. This article describes briefly the Geotail mission objectives, as well as the mission design.

Space Applications of GPS

The country's space systems ground command and control network is rapidly becoming antiquated, and will not be able to handle the expansion of space traffic projected for the twenty-first century. There is a heavy reliance on vulnerable overseas ground locations that are not guaranteed. A cooperative satellite system architecture based on GPS would significantly alleviate the complexity of a future command and control structure. Specifically, if each satellite were to carry a GPS receiver as part of its telemetry, tracking, and command subsystem, all space vehicles could maintain accurate and reliable time, ephemeris, and pointing estimates. This satellite navigation and status data could then be transmitted on a regularly scheduled basis to a ground monitoring station or a Tracking and Data-Relay Satellite System (TDRSS) Satellite. In this way, normal operations would be reduced to merely reviewing the telemetered data. In case of anomalies in the data or a space emergency, a dwell mode would be initiated in which the ground segment would begin active tracking of the space vehicle. This paper outlines the structure of such a GPS-based cooperative satellite monitoring system.