Thomas Widemann, Pedro Machado and colleagues are in the control room of the Canada-France Hawaii Telescope, located at 4200 m on the summit of Mauna Kea, Hawaii.

At this altitude, there only 60% as much oxygen as there is at sea level - and it is very cold, typically around freezing. The long journey, jet lag and night shifts add to difficulties for the observers.

In this video, Thomas and Pedro are preparing to observe Venus with the ESPADONS spectrograph. This is a high-resolution spectrograph which allows determination of the Doppler shift of solar light reflect from the Venus cloud-tops; the magnitude of this shift is used to calculate how fast the clouds are moving, i.e. the wind speed at the cloud tops of Venus.

This wind speed measurement will be performed on several consecutive night; on each night, winds will be measured in different parts of the Venus atmosphere (a range of latitudes and longitudes), to get a picture not only of how the wind varies spatially (from place-to-place), but also how the wind varies temporally (from hour-to-hour and day-to-day).

Within the EuroVenus consortium, others have been studying wind speeds on Venus by tracking the motions of clouds as seen in images from the Venus Express orbiter; these are complementary to the direct measurement of velocities from telescopes like the CFHT.

Thomas and Pedro are getting ready for a few days observing. The weather forecast is good - let's hope it stays that way!