  We present an overview of SPICA, the Space Infrared Telescope for Cosmology
and Astrophysics, a world-class space observatory optimized for mid- and far-IR
astronomy (from 5 to ~210um) with a cryogenically cooled ~3.2m telescope (<6
K). Its high spatial resolution and unprecedented sensitivity in both
photometry and spectroscopy modes will enable us to address a number of key
problems in astronomy. SPICA's large, cold aperture will provide a two order of
magnitude sensitivity advantage over current far-IR facilities (lambda>30 um
wavelength). In the present design, SPICA will carry mid-IR camera,
spectrometers and coronagraph (by JAXA institutes) and a far-IR imager
FTS-spectrometer, SAFARI (~34-210 um, provided by an European/Canadian
consortium lead by SRON). Complementary instruments such as a far-IR/submm
spectrometer (proposed by NASA) are also being discussed. SPICA will be the
only space observatory of its era to bridge the far-IR wavelength gap between
JWST and ALMA, and carry out unique science not achievable at visible or submm
wavelengths. In this contribution we summarize some of the scientific advances
that will be made possible by the large increase in sensitivity compared to
previous infrared space missions.

Instrumentation and Methods for Astrophysics