In this paper, study and analysis of S Band microstrip antenna system mounted on square body for onboard telemetry applications are presented with simulated and measured results. Microstrip antennas characteristics have been studied by placing on square body. In this study, antenna system consists of two antennas in array configuration to get quasi isotropic coverage. This antenna is flush with the surface of the square body. The antenna requires dielectric cover over radiating portion to provide the protection from heat, physical damage and other environment etc. This design is very useful for onboard Telemetry application. This type of antenna configuration is mostly useful in applications like missiles, aircrafts, spacecrafts, satellites etc. The proposed antenna is designed, simulated and optimized by using HFSS simulation software. The radiation pattern measurement of single antenna as well as two element array mounted on square body is carried out at S Band frequency.