  We present millimetre photometry and submillimetre imaging of the central
core and two hotspots in the radio lobes of the galaxy Cygnus-A. For both
hotspots and the central core the synchrotron spectrum continues smoothly from
the radio to a frequency of 677 GHz. The spectral index of the hotspots is
constant over our frequ ency range, with a spectral index of about -1.0, which
is steeper than at lower frequencies and represents the emission from an aged
population of electrons. The core is significantly flatter, with a spectral
index of -0.6 +/- 0.1, suggestive of an injected spectrum with no ageing, but
some evidence for steepening exists at our highest observing frequency.
Although IRAS data suggest t he presence of dust in Cygnus-A, our 450 um data
show no evidence of cold dust, therefore the dust component must have a
temperature lying between 85 K and 37 K, respectively.

Astrophysics