Optimum Hold-Down Configuration Design for Satellite Dual Gimbal Antenna Mechanism Using FEA

The design of hold-down system for a satellite Dual Gimbal Antenna mechanism plays a crucial role in ensuring that the system’s natural frequency characteristics are away from that of spacecraft during launch phase. This paper focuses on identification of an optimum hold-down configuration design in case of DGA for five different satellite missions. The novelty of this work lies in identification of minimum modifications required in the flight-qualified DGA mechanism, through iterative Finite Element Analysis (FEA) studies, in order to fulfill different mission specifications. Toward this, the analysis has been carried out in a modular manner on the DGA, and accordingly, a hold-down system specific to an antenna has been identified to fulfill the satellite vibration specification that is more or less similar in all the five variations considered. The hold-down configuration identified is optimal from the perspective of quantity (number of units) as well as from the notion of satellite interfacing (ease of assembly and design heritage). The latter aspect is important in systems like spacecrafts where factors like independent sub-system-level functionality, minimal time, and efforts for integration of different sub-systems need to be considered during configuration design. The paper presents the analysis carried out on the five variants along with the reasoning for adoption of that specific modifications related to hold-down module and interface modules. This approach helped in synergizing the benefits related to heritage-based design as well as the requirements of different satellite missions. The work involves an analysis of modal characteristics of the DGA mechanism to gain insights into its dynamic behavior. By studying the mode shapes and natural frequencies, the system's stiffness characteristics have been evaluated, and accordingly, improvements have been made in the configuration design of the mechanism. The paper consolidates DGA analysis results for five different satellites and compares hold-down requirements based on antennae parameters. The hardware vibration test results, indicating first natural frequency, for one of the DGA mechanisms have been mentioned as an indication of correctness of analysis. The paper serves as a guideline for configuration design of hold-down for DGA mechanism in further spacecrafts.