Scatterometer
（重定向自Scatterometry）
![](/Images/godic/202502/09/Scattometer_principle0920.GIF")
![A snapshot of Typhoon Soulik while at Category 4 intensity captured by Eumetsat's ASCAT (Advanced Scatterometer) instrument on board the Metop-A satellite](/Images/godic/202502/09/Soulik_2013_July_10_Scatterometer_Ascending_Pass0920.png")
A radar scatterometer is designed to determine the normalized radar cross section (sigma-0) of the surface. Scatterometers operate by transmitting a pulse of microwave energy towards the Earth's surface and measuring the reflected energy. A separate measurement of the noise-only power is made and subtracted from the signal+noise measurement to determine the backscatter signal power. Sigma-0 is computed from the signal power measurement using the distributed target radar equation. Scatterometer instruments are very precisely calibrated in order to make accurate backscatter measurements.