  The SAGACE experiment consists of a mm/sub-mm telescope with a 3-m diameter
primary mirror, coupled to a cryogenic multi-beam differential spectrometer.
SAGACE explores the sky in the 100-760 GHz frequency range, using four
diffraction-limited bolometer arrays. The instrument is designed to perform
spectroscopic surveys of the Sunyaev-Zeldovich effects of thousands of galaxy
clusters, of the spectral energy distribution of active galactic nuclei, and of
the [CII] line of a thousand galaxies in the redshift desert. In 2008 a full
phase-A study for a national small mission was completed and delivered to the
Italian Space Agency (ASI). We have shown that taking advantage of the
differential operation of the Fourier Transform Spectrometer, this ambitious
instrument can operate from a Molniya orbit, and can be built and operated
within the tight budget of a small mission.
