Electrical performance of wire mesh for spacecraft deployable reflector antennas
Mobile satellite communications systems require large, high gain antennas at the spacecraft to minimize the antenna gain and power requirements for mobile user elements. The use of a deployable reflector antenna for these applications provides a lightweight system that can be compactly stowed prior to deployment on orbit. The mesh surface material is a critical component in the deployable reflector antenna design. The mesh is required to provide the desired electrical performance as well as the mechanical properties that are necessary to deploy and maintain the reflector surface on orbit. Of particular interest in multi-channel communications applications is the generation of Passive InterModulation (PIM) products at the reflector surface that can result in interference in the receive band. Wire mesh was specifically identified by some as having a high potential for PIM generation based solely on the existence of nonpermanent metal to metal contacts at the junctions that are inherent in the mesh design. There are a number of other factors, however, that reduce the likelihood of PIM occurring at the mesh reflector surface. Experimental data presented demonstrate that mesh PIM generation is not significant for typical applications. PIM and reflectivity performance of wire mesh composed of gold plated molybdenum wire in a tricot knit are described. This type of mesh was successfully used for the deployable Single Access Antennas of the Tracking and Data Relay Satellite System.