The contamination levels for EIS are measured by the following:

1. The sensitivity loss due to contamination is measured by monitoring the intensities of specific solar spectral lines in the quiet sun, for more information see the EIS nugget "Sensitivity Performance of the Extreme-ultraviolet Imaging Spectrometer (EIS) on Hinode", available here.

2. QCM (Quartz Crystal Microbalance)
Measurements are taken on a weekly basis and the results (up to July 2011) are reported here:
EIS_QCM_july2011.pdf

3. Flat-field intensity levels using the EIS LEDs
The flat-field data is taken on a monthly basis and the results (up to July 2011) are reported here:
EIS_LED_flat_intensity_july2011.pdf

For the June 2011 EIS nugget "Contamination levels of EIS (as measured by QCM and LED flat-field intensity levels) click here.

--Louisa Bradley, 21-Jul-2011