The far infrared and submillimetre range remains one of the last major spectral windows still to be fully exploited. This is because of the poor transmission of the atmosphere combined with strong thermal emission, and of the technical difficulties to carry out high sensitivity observations in this window. Ground-based, air- and space borne observations have so far shown that this spectral domain is extremely rich in continuum and line radiation primarily sensitive to cool matter in the Universe such as for example dense interstellar clouds and embedded protostellar condensations, planets, comets, outer atmosphere of evolved cool stars, nuclei of active galaxies and protogalaxies.
From such general considerations it is clear that the next major advance in far infrared and submillimetre astronomy requires a space-based observatory combining good spatial resolution and very high sensitivity over the entire wave band.
In its long-term programme for space science "Horizons 2000", ESA has
identified the Far InfraRed and Submillimetre Telescope (FIRST) as its
fourth major mission (cornerstone) devoted to high throughput spectroscopy
and photometry in the wavelength range 85-900 
m.
Two ESA colloquia have been held on the subject: in Segovia in 1986 and in Liège in 1990. Various studies of the main scientific goals and mission concepts and subsequently system level studies have been carried out by ESA.
In preparation for the confirmation of the mission in June 1997 FIRST is presently in its pre-phase B activities. These include the study of payload cooling concepts (cryocooler and cryostat), the optimisation of the scientific payload (photoconductor, bolometer and heterodyne instruments), the development and qualification of the 3 m telescope and the definition and rationalisation of the science operations concept.
The purpose of the symposium will be to provide an opportunity for the community to exchange information on the many and varied scientific and technical aspects of the mission, to review the status of evolution of the field considering rapid advances and future plans of ground-based and space-based far infrared and submillimetre astronomy. A particular goal of the meeting will be to focus on the unique scientific targets and possible optimisation of the payload complement of FIRST.