  Comet C/2006 W3 (Christensen) was observed in November 2009 at 3.3 AU from
the Sun with Herschel. The PACS instrument acquired images of the dust coma in
70- and 160-micrometers filters, and spectra covering several H2O rotational
lines. Spectra in the range 450-1550 GHz were acquired with SPIRE. The comet
emission continuum from 70 to 672 micrometers was measured, but no lines were
detected. The spectral energy distribution indicates thermal emission from
large particles and provides a measure of the size distribution index and dust
production rate. The upper limit to the water production rate is compared to
the production rates of other species (CO, CH3OH, HCN, H2S, OH) measured with
the IRAM 30-m and Nancay telescopes. The coma is found to be strongly enriched
in species more volatile than water, in comparison to comets observed closer to
the Sun. The CO to H2O production rate ratio exceeds 220%. The dust to gas
production rate ratio is on the order of 1.
