Improved constraints on Neptune's atmosphere from submillimetre-wavelength observations

We describe observations of Neptune carried out using the James Clerk Maxwell Telescope (Mauna Kea, Hawaii) during September 1998. High-quality data for the sub-mm-wavelength rotational transitions of HCN (J = 4-3) and CO (J = 3-2 and 4-3) were obtained, and we use the data to make improved determinations of the abundances of these trace species and the temperature profile of Neptune's atmosphere.