Orbital Antenna Research Articles

Thermal Deformation Measurement of the Surface Shape of a Satellite Antenna Using High-Accuracy Close-Range Photogrammetry.

To determine both the size of a satellite antenna and the thermal deformation of its surface shape, a novel high-accuracy close-range photogrammetric technique is used in this study. The method is also applied to assess the performance of the antenna in orbit. The measurement principle and solution method of close-range photogrammetry were thoroughly investigated, and a detailed measurement test scheme was developed. A thermal deformation measurement of the surface shape of a satellite antenna was then carried out. The results show that the measurement error using close-range photogrammetry was smaller than 0.04 mm, which meets the accuracy requirement. Thanks to the high accuracy, it was discovered that both the surface shape and the rib precision of the satellite antenna deteriorate with decreasing temperature. The accuracy of the surface shape and ribs was lowest when the temperature node was -60 °C. The maximum root mean square errors (RMSEs) reached 0.878 mm and 0.761 mm, respectively. This indicates that the surface shape deformation error of the antenna caused by high and low temperatures is relatively high. However, the requirement for the technical design index (RMSE ≤ 1 mm for the surface shape accuracy of the antenna) is still met. Furthermore, for temperature differences of 40 °C and 80 °C, the measured RMSEs for the surface shape deformation were 0.216 mm and 0.411 mm, respectively. Overall, the technical design indicators (RMSE ≤ 0.3 mm and RMSE ≤ 0.5 mm, respectively) for the surface shape deformation of the antennas are met.

Composite anisogrid lattice toroidal shell: Application to a load-carrying rim of the spacecraft reflectarray antenna

A novel design of the composite transformable/foldable rim of the spacecraft reflectarray antenna is presented in the paper. The rim is made in the form of anisogrid lattice toroidal shell split into six parts that are jointed using hinges containing helical springs. The springs create the moments required to deploy the antenna in orbit. A dielectric flexible flat membrane with reflective radiating elements generating a radio signal with required directivity is stretched on the rim. An algorithm of the finite-element model generation is developed for the toroidal rim using a typical finite-element unit cell of lattice structure. The lattice toroidal shell is modelled as a three-dimensional frame composed of curvilinear ribs. The results of design analysis of the lattice rim delivering a minimal mass to its structure subject to constraints imposed on the fundamental frequency, values of stress, and the buckling load factor are presented in this work. The corresponding set of design parameters of lattice structure, including the angle of orientation of helical ribs, number of helical ribs of one orientation, and size of the ribs’ cross section are identified based on these results.

Dynamic analysis of the effect of mesh tension on the deployment process of loop antenna

In orbit deployment and profile maintenance are the most important functional requirements in the development of loop antenna If the antenna cannot be deployed in orbit, it will lose the signal transmission function, and the profile in orbit holding function is related to whether the antenna can stably transmit electromagnetic signals. The mesh tension (main mesh tension, rear mesh tension and tension arrays tension) is the key means to maintain the profile stability in orbit. At the same time, it is also closely related to the rod load and the maximum motor driving force in the process of antenna deployment. Based on the theory of flexible multi-body dynamics, the dynamic modeling of the deployment process of ten meter loop deployable antenna is established in this paper On this basis, the influence of mesh tension on the deployment dynamics of loop antenna is analyzed by using the control variable method, and its related variation law is obtained. This study can provide guidance for the tension adjustment in the profile adjustment stage of the ring antenna, so as to shorten the development cycle, and can also predict the deployment of the antenna in orbit.

The influence of gravity load on the accuracy of mesh reflector antenna

Space large deployable mesh antennas are the focus of research in the aerospace field. There is a high requirement for the reflector surface accuracy of the mesh antenna in orbit. Due to the low stiffness of the truss cable net system, the deformation of the flexible mesh surface under the ground gravity load cannot be ignored. Therefore, it is the key technology to ensure the accuracy of on orbit cable network reflector that accurately predict the difference of reflector under gravity load and microgravity load. This study establishes the mechanical model of the cable-truss system. The Newton Iterative Method is used to solve the nodal nonlinear equilibrium equation in the gravity load, and the deformation of the antenna mesh surface under the gravity load is obtained.

Gravity compensation system of mesh antennas for in-orbit prediction of deployment dynamics

Large deployable mesh antennas are central components of high gain satellites that are used for gathering electromagnetic signals. Deploying such antennas in-orbit is a delicate and precise process, and any failure in their unfolding can result in satellite malfunction. Thus, on-ground experiments have been used to attempt to predict the in-orbit deployment performance of mesh antennas. However, Earth's gravitational field presents a great obstacle in achieving this goal, and how best to design a gravity compensation system for the flexible webs of mesh antennas remains unclear despite various proposed gravity compensation techniques. In this paper, we attempt to address this problem via flexible multibody simulations. The results first reveal that, if the webs are not offloaded at all, the weight of the webs causes the driving forces of the motors and the bending moments of the truss members obtained during on-ground tests to deviate from those experienced by the antenna in-orbit. To counteract this problem, two different gravity suspension systems for the webs of mesh antennas were designed and evaluated. In particular, the different numbers and positions of the suspension nodes were investigated. The results show that no matter which of the two proposed designs is adopted, the number and location of suspension nodes should be carefully selected to achieve well-behaved compensation performance. Furthermore, the proposed modeling and analysis methods can also be applied to other flexible mechanical systems requiring gravity compensation.

Thermal Analysis of Deployable Truss Antenna in Orbit

Using conduction-radiation theory,considering the orbit of the antenna,temperature fields of a deployable truss parabolic antenna in orbit can be calculated at different local time.Using Visual Fortran,a finite element program based on the theory above is built,and temperature fields of antennas in different orbits can be calculated at different local time.The result is useful to thermal displacement analysis and thermal control design.

In-orbit electrical performance evaluation of large satellite-borne antenna

The satellite-borne antenna is large due to the requirement for a high gain and a multibeam operation. The construction is soft to reduce the weight as much as possible. Therefore, it is difficult to carry out the performance evaluation test on the ground with the configuration in the orbit. This paper presents a method for accurate evaluation of a large antenna in orbit. First, the electrical test results on the ground with a weight deformation made as small as possible is compared with the numerical results based on the measured values of the manufacturing errors so that the evaluation error is obtained. Next, the performance in orbit is obtained by adding the evaluation error to the values computed from the measured fabrication error and assembling error and thermal deformation analysis value. The present procedure was applied to a Ka-band multibeam antenna with an aperture diameter of 3.5 and 2.5 m on board the ETS-VI satellite. It is shown that the evaluation can be done with sufficient accuracy.