Diffuse interstellar dust emission at wavelengths between 0.5 and 2 mm
has been detected by the ARGO 1993 balloon borne telescope. This inst
rument scanned the Galactic plane in Aquila and several cirrus clouds
in Aries, Taurus and Hercules. The data are spatially consistent with
the IRAS 100 mu m sky maps, and the spectral behaviour is consistent w
ith a single temperature thermal spectrum with T-d similar to 21 K and
a spectral index of emissivity alpha similar to 1.5.