GEOSAT Follow-On Water Vapor Radiometer: Performance With a Shared Active/Passive Antenna

The GEOSAT Follow-On mission marks the first time that an Earth-orbiting microwave radiometer and radar have shared the same antenna. The antenna design must simultaneously accommodate the radar´s high-gain requirement and the high beam efficiency needed by the radiometer. Guaranteeing sufficiently high isolation between the radar transmitter and the radiometer receivers is also a critical part of the antenna design. The radiometer receiver includes a transmitter blanking circuit to further mitigate possible radar interference. Preflight and on-orbit tests of the antenna and radiometer receivers and an evaluation of end-to-end radiometric accuracy are presented. Together, they demonstrate that the shared-antenna approach can be implemented without compromising radiometric performance