  Context. The variability of Solar Spectral Irradiance over the rotational
period and its trend over the solar activity cycle are important for
understanding the Sun-Earth connection as well as for observational constraints
for solar models. Recently the SIM experiment on SORCE has published an
unexpected negative correlation with Total Solar Irradiance of the visible
spectral range. It is compensated by a strong and positive variability of the
near UV range. Aims. We aim to verify whether the anti-correlated
SIM/SORCE-trend in the visible can be confirmed by independent observations of
the VIRGO experiment on SOHO. The challenge of all space experiments measuring
solar irradiance are sensitivity changes of their sensors due to exposure to
intense UV radiation, which are difficult to assess in orbit. Methods. We
analyze a 10-year time series of VIRGO sun photometer data between 2002 and
2012. The variability of Spectral Solar Irradiance is correlated with the
variability of the Total Solar Irradiance, which is taken as a proxy for solar
activity. Results. Observational evidence indicates that after six years only
one single long-term process governs the degradation of the backup sun
photometer in VIRGO which is operated once in a month. This degradation can be
well approximated by a linear function over ten years. The analysis of the
residuals from the linear trend yield robust positive correlations of spectral
irradiance at 862, 500 and 402 nm with total irradiance. In the analysis of
annual averages of these data the positive correlations change into weak
negative correlations, but of little statistical significance, for the 862 nm
and 402 nm data. At 500 nm the annual spectral data are still positively
correlated with Total Solar Irradiance. The persisting positive correlation at
500 nm is in contradiction to the SIM/SORCE results.
