Aeolus data overview

The ALADIN instrument transmits raw data to the ground segment consisting of the accumulated spectra from the Mie receiver and the flux intensities from the Rayleigh receiver. This data is transmitted every 3.5 km. Alternatively, the instruments can provide data every 1 km for specific areas when required, and for each altitude bin (-1 km to 16.5 km height for the Mie channel, 0.5 km to 26.5 km for the Rayleigh channel). In addition to this data, Aeolus will also be transmitting attitude data, as well as data used maintain optimum calibration levels.

Cloud detection is performed in order to separate the samples of clear air and those affected by cloud. Even in cases where clouds are present the wind profile above the cloud is still obtained. Ground (or sea) echo is also searched in order to calibrate the ‘zero wind’ when possible. If there is no echo, satellite sensor data will be used to estimate Doppler shift due to the attitude of the satellite.

In order to transform raw data into wind measurements, processing has to be performed for Mie and Rayleigh channels. This requires taking the radiance background and the spectrometer spectral response, as well as calibration data, into account. The decision to use Mie or Rayleigh channel data can be based on a signal-to-noise ratio threshold. Finally, each wind measurement for each altitude layer is located in an Earth reference frame, using satellite sensor data.