The proposed Tri-band antenna design for Radio astronomy service, earth exploration satellite service and space research service 1.42 GHz, GSM for 1.8 GHz and Wi-Fi band 2.4 GHz. The RAS and EESS (passive) requirements differ in terms of geographic location, timing, and other details. The micro strip technology is widely used for commercial applications as like conversional antennas. The antenna is required to have a return loss (S11) below than 10 dB, and gain> 2 dB respectively. The dielectric substrate use is the FR4 (ϵR= 4.7) of thickness is 1.6 mm. The complete analysis results of Return loss, Gain and Bandwidth are discussed in this article. Here optimized the various parameters for better performance of the designed antenna using computer simulation technology (CST).