  The COMPASS experiment at the CERN SPS is dedicated to hadron physics with a
broad research programme, including the study of the nucleon spin structure
using muons as a probe and a variety of issues in meson spectroscopy using
hadron beams. The two stage fixed target spectrometer with electromagnetic (em)
and hadronic calorimetry in both stages provides photon detection in a wide
angular range. As discussed in this paper, the COMPASS em calorimetry plays a
crucial r\^{o}le for the Hadron programme started in 2008 as well as for the
planned COMPASS future programme of measuring GPDs via exclusive DVCS photons.
We present the photon detection coverage foreseen, and first, preliminary
results characterising the present performances of both existing COMPASS
electromagnetic calorimeters, based on test beam data taken at CERN T9 facility
end of 2007.
