SeaWinds Scatterometer

The SAS consists of a one-meter parabolic reflector antenna mounted to a spin activator assembly, which causes the reflector to rotate at 18 Rpm's (revolutions per minute). The activator assembly provides very accurate spin control and precise position or pointing information to the CDS. Optical encoders, glass disks with small patterns printed on the surface, tell the CDS exactly where the antenna is pointing to about 10/1000 of a degree. The antenna spins at a very precise rate, and emits two beams about 6 degrees apart, each consisting of a continuous stream of pulses. The two beams are necessary to achieve accurate wind direction measurements. The pointing of these beams is precisely calibrated before launch so that the echoes may be accurately located on the ground from space.