La Silla - Science Operation Department
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 above 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 (110000) and spectral bin
width (3.5 pixel) corresponds to about 800 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.