HARPS Line Drift Monitoring
Th lamp line drift and flux change over one night
Following is the plot of the time evolution of the reference lamp line drift and flux change over one night. Drift and flux ratio are measured with respect to the afternoon calibrations. Points in the drift plot outside +-0.5 m/s are related to specific instrument problems, which were later solved, and should not be considered as normal behaviour.
One CCD pixel has linear dimension of 15 microns and with the present instrument resolving power (~115000) and spectral bin width (3.5 pixel) corresponds to about 880 m/s. Therefore a drift of 0.5m/s would correspond to a movement of the light beam of about 10nm on the CCD surface.