ASCAT instrumentation

Apart from the solar panels, the Advanced Scatterometer (ASCAT) antennae arms are probably the most conspicuous assemblies on the MetOp spacecraft. The two deployed arms form a V-shape at the rear of the satellite with respect to the flight direction. Each arm houses one fore- and one aft-antenna. The shorter, wider mid-antennae are fixed underneath the payload module parallel to each other.

All six antennae are slotted-waveguide arrays manufactured from aluminium that transmit well characterised pulses of microwave energy at 5.255 GHz (C-band) via slots cut longitudinally in the waveguide. Each mid-antenna consists of three panels of eight waveguides and has an overall length of around 2.2 metres. Each side antenna consists of four panels of six waveguides and has an overall length of 3 metres.

ASCAT uses radar to measure electromagnetic backscatter from the wind-roughened ocean surface, from which data on wind speed and direction can be derived.