The Colour and Stereo Surface Imaging System (CaSSIS) is the high-resolution camera on the ExoMars Trace Gas Orbiter. It is capable of acquiring colour stereo images of surface features possibly associated with trace gas sources and sinks in order to better understand the range of processes that might be related to trace gas emission.
This image shows the principle of stereo image acquisition. It takes an image looking slightly forwards, and then the camera is rotated to look ‘back’ to take the second part of the image, in order to see the same region of the surface from two different angles. By combining the image pair, information about the relative heights of the surface features can be seen.