Characterizing the near field strength of ISS-RapidScat reflector antenna from measurement data using spectral back projection method

A newly developed instrument, known as the Rapid Scatterometer (ISS-RapidScat), has been designed to replace QuickScat and SeaWinds in measuring ocean surface winds. The new design utilizes much of the engineering model hardware from SeaWinds. ISS RF safety requirements necessitated a blanker circuit that was designed to manage ISS-RapidScat interference on sensitive nearby objects such as spacecraft and humans. This required a detailed knowledge of the antenna near-field distribution and absolute strength, which can be challenging to obtain experimentally. This paper outlines a procedure to determine the near-field values with the knowledge of the measured far-field patterns and the radiated power. The accuracy of the method has been validated through many simulations.