With the campaign to launch ESA’s Aeolus wind satellite on 21 August well underway, the satellite’s telescope has been opened and expected to make sure it is perfectly clean and shiny.
While Aeolus’ novel laser technology is arguably the sexy part of the instrument, its telescope, which measures around 1.5 m across, it pretty dominant and equally important. It is used to collect backscattered light from the atmosphere and direct it to the receiver. In short, the laser system generates a series of short pulses of ultraviolet light which are beamed down into the atmosphere. The telescope collects the light backscattered from particles of gas and dust in the atmosphere. The time between sending the light pulse and receiving the signal back determines the distance to the ‘scatterers’ and therefore the altitude above Earth. As the scattering particles are moving in the wind, the wavelength of the scattered light is shifted by a small amount as a function of speed. The Doppler wind lidar measures this change so that the velocity of the wind can be determined.
It is clearly important to make sure that the instrument is absolutely spotless, so engineers at the launch site in Kourou have first turned to the telescope and given it a close inspection.