ASCAT > Advanced ScatterometerscatterometerInstrument Type: scatterometer, Operational Mode: , Collection Type: radar, Other Information: ASCAT is a real aperture radar operating at 5.255 GHz (C-band) and using vertically polarized antennae. It transmits a long pulse with Linear Frequency Modulation ('chirp'). Ground echoes are received by the instrument and, after de-chirping, the backscattered signal is spectrally analysed and detected. In the power spectrum, frequency can be mapped into slant range provided the chirp rate and the Doppler frequency are known. The above processing is in effect a pulse compression, which provides range resolution. Its use of six antennas allows the simultaneous coverage of two swaths on either side of the satellite ground track and hence provides twice the information of the earlier instruments. The width of each double swath is 550 km with a gap around satellite track of 700 km. On an experimental basis, ASCAT also provides measurements at a higher than nominal resolution. The ASCAT instrument may operate in three different modes, Measurement, Calibration and Test. Additionally, in Measurement mode the instrument occasionally generates special source packets for Gain Compression Monitoring. The nominal instrument mode, and the only one that generates science data for the users, is Measurement mode.