On October 22nd, the lamp housing (including the sl/hg lamps) in Brewer #066 was replaced. The zenith constants (zenith offset, sighting, UV offset) changed
a bit. The R6 and R5 values dropped by about 10 units. In order to prevent the Brewer Processing Software from introducing a fictious trend 
(the R6/R5 variations are not representative of an instrument change, here), a new ICF file (ICF2010300) was created with the actual ETC values (3092/3019). 
The latter were calculated considering the ETCs and the SL value at the time of last calibration (in 2009, they were respectively 3090/3015 and 1869/3410)
and the average SL value some days before the lamp housing replacement (1862/3414).

Henri Diémoz
ARPA Valle d'Aosta