Satellite Mesh Research Articles

Novel constant-height deployable mechanisms with only revolute joints and constructed deployable ring trusses for satellite mesh reflector antennas

Deployable mechanisms play an increasingly crucial role in aerospace, yet their design still faces challenges: 1) The folded height increases while its deployed height decreases, which is not conducive to improving the folding performance; 2) Compared with revolute joints, prismatic joints have relatively weak reliability in complex space environments. To address the above challenges, novel constant-height deployable mechanisms with only revolute joints are proposed in this paper. The deployable mechanisms exhibit one degree of freedom, enabling them to attain modular expansion. Subsequently, the mobility properties of these deployable mechanisms are substantiated through screw theory. Assembly strategies for constant-height deployable mechanisms are proposed, and deployable ring trusses are further constructed to provide support structures for satellite mesh reflector antennas. The kinematics are analyzed to investigate the deployable characteristics of the proposed deployable mechanisms and ring trusses. The prototypes of a deployable mechanism and a ring truss are established to validate the designed deployable mechanisms. This work contributes novel types of deployable mechanisms with potential advantages, aiming to function as valuable references for the design and analysis of deployable trusses.

Federated Learning-Assisted Distributed Intrusion Detection Using Mesh Satellite Nets for Autonomous Vehicle Protection

Federated Learning-Assisted Distributed Intrusion Detection Using Mesh Satellite Nets for Autonomous Vehicle Protection

Wind resistance calculation of large rotary mesh antenna and its influence on dynamic balance precision

Due to the wind resistance which acts on the main reflector of large rotary mesh antenna, the correct balancing result of satellite antenna is difficult to be gotten in the ground dynamic balancing test. In order to solve this problem, the dynamic balance method of large rotary mesh antenna which is under the influence of wind resistance in both low pressure environment and standard atmospheric pressure environment on the ground is studied. Based on the theoretical analysis and the experimental data of two-dimensional flow around circular cylinder, a new method of the large rotary mesh antenna wind resistance calculation is proposed, according to the CFD analysis of the three dimensional flow field. Through the dynamic equivalent method, the distributed wind resistance acted on the main reflector of the mesh antenna in the rotating state is equivalent to the principal vector and principal moment of the action point in each quadrant, and then transformed into the eccentric mass on the distribution plane. It provides a feasible and innovative way to estimate the influence of wind resistance on the dynamic balance accuracy of large mesh antenna, so as to compensate the wind resistance effect. Combined with the ground dynamic balancing requirements of a certain type of satellite mesh antenna, the whole finite element model of the mesh antenna is established, the simulation of ground dynamic balancing test is carried out, and the influence of wind resistance on the ground dynamic balancing results of the antenna is analyzed in this study, which provides important data for compensating the influence of wind resistance and ensuring the on-orbit balancing accuracy of the antenna.

Active vibration control of a hoop truss structure with piezoelectric bending actuators based on a fuzzy logic algorithm

Active vibration control of large flexible space structure is a challenging topic in the system dynamics and control of spacecraft. This paper proposes a novel approach for vibration control on a large hoop truss structure, typically used as mesh satellite antenna. First, to suppress the first-order bending modal response of the hoop truss structure with an initial disturbance, a piezoelectric bending actuator with excellent bending actuation performance was carefully designed as a key component of an active vibration control system. Then, the actuating characteristics of the actuator and the dynamic equations of the active structure were analyzed and formulated based on a finite element method. In order to improve the vibration-attenuating effect of the control system, a Mamdani-type fuzzy logic algorithm was employed in a closed-loop control system. Finally, simulations and experiments were implemented to validate the effectiveness of the proposed active control approach and structure. The experimental results showed that the decay time of first-order bending modal response (around 0.34 Hz) of control system reduces by 75% compared with that of the uncontrolled system. The results demonstrate that the proposed active vibration control system has good application potential in controlling the bending modes of a large flexible spacecraft.

Editoral: Special Issue on Photonic and RF Communications Systems

Editoral: Special Issue on Photonic and RF Communications Systems

Energy efficient continuous phase modulation signals for satellite intelligent transportation systems

In this study, performance of intelligent transportation systems (ITS), which consists of satellite mesh networks, is investigated. These networks are characterised by the absence of the on ground satellite gateway and many power limited user terminals with small antennas which are able to direct connection with a satellite. In such scenario, energy efficiency signals, for example, continuous phase modulation (CPM) should be used for transmission. The authors analyse performance of a mesh ITS which apply multiuser frequency division multiplexed (FDM) transmission with coded CPM via computer simulations. The spectral efficiency of investigated system is improved by reducing the inter-carrier frequency (ICI) spacing and using simple iterative ICI cancellation algorithm at the receiver. The results suggest that FDM CPM transmission might constitute a desirable option in ITS satellite mesh, ad-hoc networks.

Wheatstone Project

Background The $29 billion Wheatstone Project is one of Australia’s largest resource projects, located 12 km west of Onslow on the Pilbara coast of WA. Objective NewSat was selected to provide vital communication services to the Wheatstone Project as the supplier of the Operations Satellite System to deliver remote internet, voice, video, and data services for LNG operations, OH&S compliance, backup communications, and onsite staff welfare. A project as large and complex as the Wheatstone Project required a range of solutions to overcome multiple communication challenges due to the large and varied number of users and diverse and harsh onsite weather conditions. With long standing relationships with Australian oil and gas service providers, NewSat had the reputation and experience to deliver the satellite services required. Solution NewSat worked closely with the Wheatstone engineering and design team to ensure the project had the best possible satellite service available and the highest amount of design options as the Project matured. The final design was a meshed satellite network, linking the onshore production facility at Onslow, the offshore platform, and the Perth head office. As a 24 x 7 x 365 operation, the project required an always-on satellite service. NewSat’s wide range of satellites provided line-of-site and satellite diversity to ensure there was no single point of failure across the satellite network. As well as providing the best infrastructure, NewSat integrated Adaptive Coding and Modulation (ACM) into the network to overcome the varying atmospheric challenges inherent in the region.

Net‐centric satellite mesh architecture for emergency communication

AbstractThis paper introduces a net‐centric architecture based on ETSI and TIA Regenerative Satellite Mesh‐A (RSM‐A) standard that uses satellites with on‐board packet switching. An Internet Engineering Task Force (IETF) IP protocol family‐based extension of RSM‐A for enhanced user interoperability, combined with multiple spot beam satellite implementation facilitates higher capacity, easy deployment and full mesh terminal‐to‐terminal operation that is required for managing emergency situations. This Net‐centric Satellite Mesh (NSM) architecture adequately addresses the current and evolving networking needs for emergency‐management information systems that can generate high data rate and real‐time multi‐media traffic. The NSM architecture supports the evolving IETF Emergency Telecommunications Service standards with packet flow‐level admission control for guaranteed packet quality‐of‐service needed by real‐time unicast and multicast traffic over satellite networks. The multi‐plane architectural discussion is supported with measurements of selected end‐to‐end application behavior that validate the technical capabilities of NSM by using a pioneering Ka band satellite system, based on RSM‐A, which has recently been deployed in North America. Copyright © 2010 John Wiley & Sons, Ltd.

A native IP satellite communications system

≪ In the framework of ESA's ARTES-5 program the Institute of Applied Systems Technology (Joanneum Research) in cooperation with the Department of Communications and Wave Propagation has developed a novel meshed satellite communications system which is optimised for Internet traffic and applications (L*IP—Local Network Interconnection via Satellite Systems Using the IP Protocol Suite). Both symmetrical and asymmetrical connections are supported. Bandwidth on demand and guaranteed quality of service are key features of the system. A novel multi-frequency TDMA access scheme utilises efficient methods of IP encapsulation. In contrast to other solutions it avoids legacy transport network techniques. While the DVB-RCS standard is based on ATM or MPEG transport cells, the solution of the L*IP system uses variable-length cells which reduces the overhead significantly. A flexible and programmable platform based on Linux machines was chosen to allow the easy implementation and adaptation to different standards. This offers the possibility to apply the system not only to satellite communications, but provides seamless integration with terrestrial fixed broadcast wireless access systems. The platform is also an ideal test-bed for a variety of interactive broadband communications systems. The paper describes the system architecture and the key features of the system.

Satellite-friendly protocols and standards

Due to the exponential growth of the Internet, the protocol suite of the Internet has become dominant. In the past, satellite communications systems used proprietary protocols. More recently, satellite multimedia architectures have been based on ATM as well as MPEG transport and multiplexing mechanisms. When the traffic is however mostly IP, then the transmission overhead will be significant in both cases. Therefore native IP satellite systems are preferable. In this paper a meshed satellite communications system is presented which is optimised for IP. An important feature is the support of quality of service. Typical applications are fast Internet access and multimedia services. Due to its flexible architecture it can be easily adapted for different standards.

3322 衛星搭載用メッシュアンテナの鏡面精度

3322 衛星搭載用メッシュアンテナの鏡面精度

Satellite Mesh Reflector Temperature Measured by Using Fine Thermocouples

iments performed in a test cell with aspect ratio LIH =16 have shown that steady thermal distortions arise in the presence of relatively large g-jitter at relatively high frequencies. These distortions depend on the value of the vibrational Rayleigh number (proportional to the temperature difference and to the velocity of the g-jitter oscillations). An experimental proposal is being considered for the International Space Station, where the steady residual gravity is reduced by several orders of magnitude, compared with Earth conditions, so that a fluid cell with unitary aspect ratio could be used and relatively small g-jitter will be sufficient to induce measurable thermofluiddynamic distortions.