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About ASCAT   Once MetOp is in its polar orbit 800 kilometres above the surface of the Earth and the solar panels are in position, the Advanced Scatterometer (ASCAT) two three-metre long antenna arms are gently deployed into a fixed V-shaped position at +135° and -135° with respect to the spacecraft flight direction. Each of the antenna arms provides the fore-beam of one swath and the aft-beam of the other. ASCAT uses radar to measure electromagnetic backscatter from the wind-roughened ocean surface, from which data on wind speed and direction can be derived.  Winds travelling over the surface of the oceans influence the radar backscattering properties of the surface of the sea in a way that is related to wind speed and direction. ASCAT will exploit this fact by transmitting pulses of microwave energy at 5.255 GHz (C-band) towards the surface of the Earth and then records the resulting echoes. These data will be used to derive wind speed and direction over the oceans for use in operational weather forecasting and climate research.
ASCAT's two sets of antennae provide two 550 kilometres wide swathes. Observations for each swathe are made sequentially so that each point on the ground is viewed three times, first by the fore-beam, then by the mid-beam and finally by the aft-beam. Last update: 28 June 2006 |