Development, Challenges, and On-Orbit Deployment of a Large Flexible Antenna on Communication Satellite

A mechanism has been developed for a tubular structure antenna operating in UHF band for a communication satellite. The antenna of diameter 0.5 m and height 3 m is required to be positioned away from the satellite to a distance of 1.3 m to avoid RF signal interference with the metallic components present on the spacecraft deck. During launch, the antenna was required to be rigidly held to the satellite deck and encapsulated within the launch vehicle envelope to safeguard the fragile antenna structure against the launch loads. After deployment in the geostationary orbit, the antenna had to be positioned and oriented with its central cylindrical axis parallel to the spacecraft axis with an accuracy of ± 0.25°. It was suggested to use only RF transparent material and minimum metallic components over the antenna to reduce noise associated with data transmission. The RF transparent materials are non-metallic and have inherent limitations of stiffness and strength. Thus, load bearing members could not be made up of non-metals which led to the innovation in the antenna hold-down design. Moreover, the positioning requirement had to be met and tested on ground. This also required development of variety of gravity compensation systems for various test conditions. The mechanism for the hold-down release and deployment of this antenna has been designed, realized, and extensively tested to qualify for space use. The complete mechanism has undergone vibration test along with antenna on the simulator deck as well as with the Spacecraft. This paper summarizes the configuration and design considerations, various characterization and qualification tests performed on all the sub-systems including thermo-vacuum test. It also highlights the modifications and challenges faced during the sub-system as well as spacecraft level testing phases including the fixture and test-setup details. Final on-orbit performance of the complete mechanism has been summarized at the end. The paper helps the readers to understand the complete life cycle of a newly developed mechanism and its associated challenges.