Planned maintenance: [**Cosmos**](https://www.cosmos.esa.int) portal infrastructure upgrade on Mon December 16th from 7:00am CET - Tue December 17th 9:00am CET.
ESA uses cookies to track visits to our website only, no personal information is collected.
By continuing to use the site you are agreeing to our use of cookies. OK Find out more about our cookie policy.
The optical module of the radial-velocity spectrometer (RVS), containing a grating plate (middle), four fused-silica prismatic lenses, as well as a bandpass-filter plate (far right).