When integrated, the Raman Spectrometer will be located on the rover's robotic instrument arm, where it can be positioned to examine rock and soil samples. The spectrometer transmits a red light laser beam at the sample and receives returned light. Due to the Raman effect, a small (one part in a million) fraction of the light is shifted to longer wavelengths. A spectrometer records signal strength as a function of wavelength shift. The resulting spectrum is diagnostic of the mineralogy.
The Athena Payload website contains more information about the Raman Spectrometer flight model.