Design Methodology of Solid State C-Band Transponder for Radar Calibration

C Band Tracking Radars play a pivotal role in tracking ISRO launch vehicles. The real time trajectory data of the launch vehicle provided by the Radars is used for Range Safety decision making process. Calibration of Radars is highly essential since any inaccuracy in the tracking data will reflect as error in Instantaneous Impact Point of the Vehicle, which can result in a wrong decision. Hence, periodic calibration of Radars needs to be carried out to ascertain the Radar accuracy specifications. Of the various techniques available to calibrate Radars, satellite based calibration is found to be the most accurate and advantageous. Satellite based Radar calibration is carried out in conjunction with Transponder onboard the satellite. The performance of the Transponder in space environment is very important for this application. This paper outlines the design methodology adopted for the development of highly reliable Solid State C Band Transponder (SCBT) which is the onboard segment in satellite. SCBT, developed in a highly innovative approach has been successfully flown in SARAL and Resourcesat-2A satellites and is regularly used for Radar calibration.