This animation shows the alignment of the solar panels that makes Venus Express twist in the upper atmosphere of Venus. It is known as the torque technique and allows scientists to measure the density of the atmosphere at the North Pole of Venus, which Venus Express can be made to skim.

The technique requires the solar panels on board Venus Express to be positioned at an angle to each other. The effect is maximum when the angle corresponds to 90 degrees, with one of the panels perpendicular to the incoming flow and the other seeing it edge on.

Due to this difference, the atmosphere causes the spacecraft to turn. Instruments called reaction wheels inside Venus Express compensate for the twist, keeping the spacecraft in the right attitude. The readings from the reaction wheels are recorded so that scientists on Earth can translate them into a density estimate.

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