Deployable Reflector Antenna Research Articles

Numerical Investigation on the Thermal Characteristics of Lightweight Metal Mesh-Based Reflector Antenna with Various Knitting Conditions

Proper prediction of the temperature variation in a metallic wire mesh for spaceborne large deployable reflector antennas is essential for evaluating the dimensional stability of the antenna under extreme on-orbit thermal environments. However, predicting the temperature of a mesh is difficult because of its complex yarn configuration. To analyze the thermal behavior of the spaceborne mesh antenna reflector, the thermal optical characteristics with various knitting methods of the metallic mesh were obtained experimentally in this study. Subsequently, to analyze the thermal sensitivity of the reflector based on its optical properties, an on-orbit thermal analysis of the mesh reflector was performed based on measurements of the mesh specimen. We also investigated the influence of deployable solar panels on the thermal gradient of the reflector.

Development of Deployable Reflector Antenna for the SAR-Satellite: Part 1. Design and Analysis of the Main Reflector Using Honeycomb Sandwich Composite Structure

The deployable reflector antenna based on the synthetic aperture radar is a satellite component that consists of a unit structure in the form of a folded reflector. During the launch process, this satellite antenna is in the stowed condition to improve storage efficiency. It is then deployed to perform the space mission in the on-orbit condition. Due to these structural characteristics of the deployable reflector antenna, the reflector is possible to be loaded in the limited volume of the launch vehicle with the reduced size. Additionally, because the deployable reflector antenna is made by the lightweight material of the carbon fiber reinforced polymer and honeycomb core, it can reduce the launching cost and improve the revisit interval. In this paper, the conceptual design of the main reflector of the deployable reflector antenna was conducted. The main reflector was designed as the honeycomb sandwich composite structure. To design the main reflector, the stacking sequence of the composite material and honeycomb core was investigated to maximize the structural stiffness and minimize the antenna’s mass. Subsequently, finite element analyses including modal, quasi-static, structural–thermal coupling, and transient response were performed to numerically evaluate the structural performance of the lightweight composite reflector antenna.

Dynamics and attitude control of space-based synthetic aperture radar

Abstract This work tackles the problem of attitude control of a space-based synthetic aperture radar with a deployable reflector antenna, representing a lightly damped uncertain vibratory system with highly nonlinear dynamics. A control strategy based on two identifiable in-orbit vector parameters is proposed to make the robust controller less conservative. The first parameter is used in the feedforward loop to achieve a trade-off between the energy efficiency of maneuvers and the amplitudes of the oscillatory response. The feedback loop utilizes the second parameter to accurately handle the controller-structure interactions by adaptive notch filters. The notch filters are included in the augmented plant at the design stage to guarantee closed-loop robustness against disturbances, unmodeled dynamics, and parametric uncertainty. The system’s robustness and specified requirements are confirmed by formal criteria and numerical simulations using a realistic model of the flexible spacecraft.

Analysis of Cross-Polarized Field by Panel Misalignment Errors in a Deployable Reflector Antenna

This paper analyzes the generation mechanism of a cross-polarized field resulting from panel misalignment errors in a solid-surface deployable antenna. Misalignment of the panel in a deployable antenna results in path length error and rotation of the unit normal vector on the reflector surface. However, in terms of the analysis of cross-polarization (cross-pol) generation, rotational error is a more significant factor. In the aperture field, the distributions of cross-pol components are calculated to identify the polarization characteristics of the radiated field. For uniform misalignment, the peak-to-cross polarization (XPOL) is found to be smaller than -50 dB for misalignment angles less than 3°. Furthermore, when the panels are non-uniformly misaligned with a sinusoidal distribution, the cross-pol level depends on the angular position of the maximum misalignment.

Surface accuracy analysis and optimization design of rib-mesh paraboloidal antenna reflectors

For deployable paraboloidal antenna reflectors, a rib-mesh structure configuration is suitable owing to its high packing efficiency and reliability. In this configuration, the only supporting members are the ribs. Achieving a sufficient surface accuracy is the primary challenge. In this paper, the rib-mesh antenna reflector structure is divided into two types: a fold-rib structure with a rigid boundary and a wrap-rib structure with an elastic boundary. For each type, a form finding method based on the finite element method (FEM) as well as a rib shape optimization method for enhancing the surface accuracy using a genetic algorithm (GA) are proposed. For the fold-rib structure, the geometric parameters and prestress changes in the mesh shape are analyzed. It is found that the stress ratio influenced the surface accuracy, but the number of ribs is the decisive factor. For the wrap-rib structure, parametric analyses of rib deformation and surface accuracy are conducted. It is found that several parameters significantly affect the deformation, but their influence on the surface accuracy can be almost eliminated by optimization. Following the proposed design method, a prototype of a wrap-rib antenna reflector with a 0.5 m aperture and 16 ribs is designed and fabricated. The accuracy values of the measured surfaces are close to the expected values. It is concluded that the whole design process for rib-mesh structure configuration can be considered to be effective and operable.

Review and evaluation of warp-knitted patterns for metal-based large deployable reflector surfaces

A large deployable reflector antenna (LDA) is comprised of numerous components. One of the key components of this reflector antenna is the reflector surface. Several types of reflector surfaces have been developed and used, namely, metal mesh-based reflector surfaces, membrane-based reflector surfaces, etc. The benefits presented by warp-knitted metal mesh-based reflector surfaces are their foldability and light weight structural characteristics. Typical metal mesh-based reflector surfaces are produced using a warp knitting textile manufacturing process. A warp-knitted metal mesh reflecting surface is an elastic, open structured knit with a low bending stiffness produced on a high gauge knitting machine (E26 or higher gauge) consisting of a compatible metal yarn (typically tungsten or molybdenum). This paper gives an overview about the requirements for mesh reflector surfaces stated in the literature. Afterwards, an overview of different patterns currently investigated by the LDA community is given. The names given to the various types of patterns in the literature often differ. The construction of the various patterns is therefore first optical analysed and compared. Subsequently, the different patterns are evaluated on the basis of the requirements. Based on the requirements and the possibilities of the warp knitting machine, new possible patterns are identified and evaluated. For the development of a new reflector surface, the identified patterns are developed as a warp-knitted spacer fabric. This decision increases the stiffness of the knitted fabric. This new concept for an advanced reflector surfaces is introduced by Large Space Structures GmbH (LSS) (concept) and ITA (production technology).

Digital Beamforming for Spaceborne Reflector-Based Synthetic Aperture Radar, Part 1: Basic imaging modes

Deployable reflector antennas illuminated by a digital feed array enable spaceborne synthetic aperture radar (SAR) systems to image an ultrawide, continuous swath at a fine azimuth resolution. This is facilitated by the use of dedicated imaging modes and by multidimensional digital beamforming (DBF) techniques. This article is part 1 of a tutorial trilogy, where a focus is put on the required onboard functionality, operational techniques, and DBF aspects, for which a rigorous mathematical description is included. To maintain general validity, the functional implementation for the various modes is detailed, thus avoiding restricting the description to a specific realization. The reader is assumed to be familiar with the general concept of SAR and, otherwise, referred to the literature on the topic. The approach followed in the trilogy is to start with a basic imaging concept and then move to more advanced modes, thus successively increasing the complexity; the mathematical description follows the same approach.

Modified design of the deployable mesh reflector antenna for mini satellites

This paper is devoted to the development of a light-weight deployable mesh reflector antenna for mini satellites with synthetic aperture radar (SAR) payload. The analyses of the electromagnetic and mechanical properties of the multi-beam deployable reflector antenna are performed for the space-borne dual-band (X- and S-bands) synthetic aperture radar (SAR) system based on digital beam forming (DBF). The reflector antenna is of offset type with a diameter of 3.35 m and weight of 7.8 kg. The DBF-SAR system is designed for mini satellites of total mass < 150 kg.

Investigation on design methods for cable mesh configuration of deployable space antenna reflector

Mesh reflectors are always a preferable option for large size deployable antenna reflector over solid surface reflectors due to their flexibility of adjustment in minimum possible space and ability to get deployed to full configuration in space. Maintaining surface properties and accuracy are two important requirements in the design of the mesh reflector for the performance of cable network antenna reflectors. The present work considers the various design approaches for cable mesh configuration of space deployable antenna reflectors. The equal force density shape forming criteria such is applied for obtaining the desired parabolic curvature of the mesh configuration. The ring structure for the deployable mechanism is considered as rigid linkages for designing mesh configuration. A generalized numbering scheme for nodes and cable mesh link is formulated for carrying forward various shapes forming criteria which help in making an algorithm. The algorithm for a better understanding of these methods is developed using MATLAB with nodal coordinates and its connection. Mesh configuration is developed with a different number of divisions. A study is also carried out for finding the required number of divisions for a highly accurate parabolic profile for a particular band frequency. A demonstration model is developed and a comparison of the coordinates of the prototype is made with those arrived at using the model.

Structural Dynamic Improvement for Petal-Type Deployable Solid-Surface Reflector Based on Numerical Parameter Study

Petal-type Deployable Solid-surface Reflector (PDSR) is a kind of important structure widely applied in deployable reflector antennas in aerospace engineering. The dynamic properties of this reflector structure in deployed state are significant to the reflector accuracy for antennas. However, the study of the dynamic evaluation of deployable structure with revolute joints is difficult and seldom concerned by researchers. In order to study dynamic properties of the PDSR, the Cable Replacement Method (CRM) was utilized to equivalently simulate the nonlinear structural stiffness of the revolute joint for numerical analyses. The Finite Element Model (FEM) of this reflector structure was established by commercial software ANSYS (ANSYS Inc., Canonsburg, PA, USA) and verified by the theoretical analysis and dynamic test of actual prototype model. The natural frequencies and mode shapes of deployed reflector were computed to study the influence of drag spring design parameters as stiffness, pre-tensioned force, and distance of two adjacent linkage butts. Finally, the analysis results were concluded that the drag springs between two adjacent petals can essentially improve the dynamic performance of reflector structure in deployed state. It can be a useful technical system for future engineering applications of PDSR antennas.

New design modifications of the supporting ring for a large deployable space reflector

Though theoretical and experimental studies of the design of large deployable antenna reflectors have already been carried out for quite a long time, the results obtained in this area of research still attract a lively interest and have good application prospects. In the present paper, two novel design modifications are described for the symmetric (i.e. with circular apertures) radio telescopes. The novelty consists in that improved stiffness and stability have been obtained by combining two conical pantograph systems and thus getting the whole hinged-bar structure consisting of cylindrical and sliding hinges only. Three FE models of the supporting ring structure are constructed and compared with one another using the NASTRAN FEA software. The degrees of freedom of hinges are simulated in local coordinate systems. A static, modal and buckling analysis had been done to investigate, strength and stiffness characteristics.

전개형 반사판 안테나의 패널 불완전 전개에 의한 편파특성 영향

In this study, we analyzed the effects of panel misalignment on the polarization performance of a deployable reflector antenna. If panel misalignment occurs in a parabola-type deployable reflector antenna, the antenna shape is distorted compared with the original parabola. The shape distortion causes the degradation of co- and/or cross-polarization performance. We investigated the difference in performance degradation for the cases of symmetric and asymmetric misalignments. The cross-polarization is small when the misalignment is symmetric, and approximately 68 dB higher for asymmetric misalignment than that in symmetric case. It was confirmed that the cross-polarization mainly arises from the asymmetry of the antenna.

연료 슬로싱 효과를 고려한 위성 기동 간의 SAR 안테나 반사판의 진동 분석

Sloshing refers to the movement of a liquid free surface caused by disturbances of a liquid partially filled in a container. Sloshing generates forces and moments owing to the pressure distribution on the liquid free surface, which affect the dynamic stability of the vessel. An equivalent mechanical model that exerts the same amount of force and moment on the vessel wall as sloshing is used to analyze the sloshing effect on the vessel. This phenomenon also occurs in the fuel tank of a satellite structure that controls the attitude using a propulsion system with a liquid propellant. A satellite with a deployable synthetic-aperture radar (SAR) antenna, which is made of a thinner and lighter material, is likely to be more susceptible to various disturbances, including liquid sloshing. In this study, an analysis of a deployable SAR antenna reflector vibrating from the liquid fuel sloshing between the changes in the satellite’s attitude was conducted. The equivalent mechanical model is used to simulate the sloshing effect, and the vibrations of the reflector are compared and analyzed with and without the sloshing effect for the specified torque input.

Form-Finding Design of Cable–Mesh Deployable Reflector Antennas Considering Wire Mesh Properties

The wire mesh is a key component of a cable–mesh deployable antenna; it is laid on the cable net to reflect electromagnetic waves. The knitting form, mesh size, and wire mesh ductility directly affect the accuracy of the reflector. In this paper, a form-finding design method that considers wire mesh properties is proposed for cable–mesh deployable reflector antennas. First, a three-dimensional geometric model of the wire mesh is established. Based on the augmented Lagrange multiplier method, the finite element method model of the wire mesh is derived, and its accuracy is verified by experimental data. Second, to simplify the computation for a large-scale flexible wire mesh structure, the mechanical model is made equivalent to an anisotropy membrane. Third, based on the nonlinear finite element method, the form-finding design method of the cable–membrane composite structure is proposed. The simulation and experimental results demonstrate the significant influence of the mechanical properties of wire mesh and the validity of the proposed design method.

Geometrical-optics computer model of metal-knitted mesh for calculations of solar pressure on space deployable antenna reflectors.

A novel computer 3D model is presented for calculations of optical parameters (transmittance, reflectance, and absorbance) of a metal-knitted mesh textile as a structural element of deployable antenna reflectors for space satellites. The model is based on geometrical-optics ray tracing upon diffuse scattering of a broadband light source (Sun) at a complex knitted mesh structure with different inclinations to the radiative source. The proposed computer model is built for the special type of metal-wire textile (two-bar large void tricot) possessing extremely high transmittance and is verified by comparison with the experimental measurements of light scattering parameters of real antenna mesh samples of data-relaying satellites (Russian series "Loutch"). The model is used for calculations of solar radiation pressure exerted on a knitted mesh antenna reflector and gives the maximal pressure value of about 0.28 μN/m2.

Investigation of ultraviolet radiation effects on thermomechanical properties and shape memory behaviour of styrene-based shape memory polymers and its composite

In recent years, shape memory polymers (SMP) have been researched extensively for space applications, such as deployable solar panels and antenna reflectors. Space applications cause SMP components to be severely exposed to ultraviolet (UV) light which may results in material degradation which may causes catastrophic failures and costs substantial amount of public money. This paper investigates the effect of UV light exposure on thermomechanical properties and shape memory effect (SME) of the Styrene-based SMP and its Glass fibre shape memory polymer composites (SMPC). Dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA), have been used to investigate the thermomechanical properties, SMEs and thermal stability before and after the UV exposure. Further, Fourier transform infrared spectroscopy (FTIR) was performed to analyse the after effect of UV exposure on the polymer's chemical structure. Results have revealed that UV exposure had different impacts on the SMP samples. UV exposure have degraded the mechanical properties, lowered the glass transition temperature (Tg), considerably reduced shape recovery rate, and programming and recovery stresses in all samples. However, the exposure had no considerable effect on the fixity ratio and relaxation modulus of the neat SMP sample, and it slightly increased the fixity ratio of the SMPC samples.

Cyclic Tensile Loading Test for a Quartz Fiber Cable of a Deployable Antenna Reflector on Satellite

Cyclic tensile tests were performed to evaluate the mechanical performance of a quartz fiber cable assembly that is part of the mesh and cable network system of a deployable antenna reflector. The cable assembly was a non-twisted quartz fiber yarn covered with a Nomex knitted fiber tube, and both ends were bent back to form loops. The cable assembly demonstrated nonlinear tensile behavior in the first cycle, which caused a large residual displacement after unloading. In the following cycles, relatively linear tensile behavior was observed. However, displacement at the maximum allowable loading, i.e., incremental displacement, increased with increasing number of cycles. The quartz fiber cable assembly was divided into a straight segment and a loop segment, and those were tested individually. The loop segment showed nonlinear tensile behavior. The incremental displacement of the loop segment was almost the same as that of the cable assembly. Cross-sectional observation of the loop segment revealed that incremental displacement developed due to flattening of the cable at the loading points. Total displacement due to flattening of the cable was consistent with the incremental displacement of the cable assembly.

Insensitivity Characteristics in the Dual Polarization of Deployable CFRP Reflector Antennas for SAR

A large deployable reflector antenna is considered and designed for the application of a synthetic aperture radar system requiring high gain for the high resolution of a detected image within a distance of a few hundred kilometers. For its lightweight and strong characteristics, carbon fiber reinforced polymer (CFRP) is introduced as a composite material and fabricated for conductivity evaluation. Effective electrical characteristics are obtained as a function of carbon fiber direction, using measured S-parameters in a rectangular waveguide. By taking into account the changes of the effective electrical characteristics that depend on the fiber direction of reflector antenna, the radiation pattern is investigated at X-band in terms of gain and polarization variation effects. The proposed reflector antenna made of quasi-isotropic CFRP panel can realize the insensitive characteristics depending on the incident polarization.

Analytical modeling of the flexible rim of space antenna reflectors

This paper presents a geometrically nonlinear analytical model of the flexible cylindrical rim of a deployable precision large space antenna reflectors made of shape-memory polymer composites. A nonlinear boundary-value problem for the rim in the deformed (folded) configuration is formulated and exact analytical solutions in elliptic functions and integrals describing the deformation modes of the rim are obtained. Exact analytical solutions based on the geometrically nonlinear model are obtained and can be used to determine preliminary geometric dimensions and optimal shape of the flexible rim along with the estimation of the accumulated energy.

Uniform-tension form-finding design for asymmetric cable-mesh deployable reflector antennas

Space antennas with high gain and high directivity are in great demand for future communication and observation applications. Deployable cable-mesh reflector antennas are required to be tensioned in a self-equilibrated state through form-finding design. In order to ensure the cable-mesh reflector antennas’ high performances, both surface accuracy requirements and tension uniformity should be considered in the form-finding design process. To effectively implement the form-finding design for asymmetric cable-mesh antennas, a two-step uniform-tension form-finding approach is presented. In step 1, with the cable tension and membrane stress being considered simultaneously, an iterative design technique which combines force density method and surface stress density method is presented. In step 2, considering the asymmetry between the rear and front nets, the nodal z-coordinates and cable tensions of the rear net are designed with the combination of the equilibrium matrix method and force density method. Finally, an offset AstroMesh antenna is designed using the proposed method. For the obtained antenna, the cable tension and membrane stress of the front net are completely uniform, and the maximum tension ratio of the rear cable net is 1.06, which are very satisfactory.