FIRST - FAR-INFRARED AND SUBMILLIMETER SPACE TELESCOPE, A MAJOR SCIENTIFIC PROJECT OF THE EUROPEAN-SPACE-AGENCY

As one of the four cornerstones of its scientific program Horizon 2000, the European Space Agency is studying a far-infrared and submillimeter space telescope (FIRST) that will open to astronomical observations the 100-mum to 1-mm spectral region, virtually unexplored with a subarcminute angular resolution. The 3- to 4-m-diam telescope will be diffraction limited at lambda = 300 mum or less. The expected lifetime of this system in orbit is five years or more. The model payload is composed of two focal instruments. The multifrequency heterodyne spectrometer will give a very high spectral resolution in the 400- to 630-mum wavelength range and around 300 mum. The far-infrared receiver (FIR) will be an imaging spectrometer covering the 100- to 400-mum range with spectral resolutions ranging from 3 to 10(4) obtained with a set of Fabry-Perot interferometers and filters. Arrays of photoconductors and bolometers are cooled at 1.5 and 0.15 K, respectively, by an open-cycle He-3/He-4 dilution+Joule-Thomson expansion system developed to operate at zero gravity.