During 1997, the group has been invited to participate in two of the instruments on FIRST (Far InfraRed and Sub-millimetre Space Telescope). FIRST is the natural continuation of ISO, as it extends the wavelength coverage into the sub-mm range, improves the spatial resolution in the far infrared, and introduces high spectral resolution with heterodyne techniques. The actual instruments are a bolometer camera/spectrometer (SPIRE) and a heterodyne spectrometer (HIFI). In the present planning, we are responsible for the software simulator for SPIRE and we have also suggested a Swedish solution of the auto-correlators for HIFI (a further development of the Odin auto-correlators). FIRST is expected to be launched in 2007.