The large antenna that is shared by both radar and radiometer is SMAP’s most prominent feature. It operates just like a satellite dish, only is much larger, where a reflector collects all of the radio waves which focuses them into the feed horn. The feed horn collects the echoes from the radar and the surface emissions from the ground and sends them to the radar and radiometer electronics for processing. The feed horn is a large cone visible on the outside of the spacecraft.  The antenna reflector is a mesh antenna 6 meters (about 20 feet) in diameter.
NASA
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