Apart from the solar panels, the 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. The mid-antennae each consists of three panels of eight waveguides and have an overall length of around 2.2 metres, the side antennae each consists of four panels of six waveguides and have an overall length of 3 metres.