Unveiling the obscured universe with SPICA, A joint infrared space observatory

The mid/far infrared hosts a wealth of spectral information that allows direct determination of the physical state of matter in a large variety of astronomical objects, unhindered by foreground obscuration. Accessing this domain is essential for astronomers to much better grasp the fundamental physical processes underlying the evolution of many types of celestial objects, ranging from protoplanetary systems in our own milky way to 10-12 billion year old galaxies at the high noon of galaxy formation in our universe. The joint ESA/JAXA SPICA space mission will give such access for the astronomical community at large, by providing an observatory with unprecedented mid- to far-infrared imaging, polarimetric and spectroscopic capabilities. With a launch expected to happen in 2032, it will be the ideal complement of the space based (ATHENA) and ground based facilities available at this time (ELT, TMT, ALMA, SKA), so that the entire high energy to radio electromagnetic spectrum will be accessible to world astronomers with unprecedented power and sensitivity. The SPICA mission, under development as a joint ESA/JAXA project, will combine a 2.5-meter diameter telescope cooled to below 8 K with instruments employing state-of-the-art ultra-sensitive detectors. Instead of using liquid cryogen, a combination of passive cooling and mechanical coolers is employed to cool both the telescope and the instruments, allowing the mission lifetime to extend significantly beyond the required three years. SPICA offers spectroscopy instruments with spectral resolving power ranging from R~50 through 11000 in the 17-230 μm domain as well as R~28.000 spectroscopy between 12 and 18 μm. The state-of-the-art Transition Edge Detectors in the 35-230 μm detectors in the SAFARI spectrometer will provide an unprecedented sensitivity of ~5×10−20 W/m2 (5σ/1hr) - at least two orders of magnitude improvement over what has been attained to date. With the 10'x12' large Field of View SMI imager SPICA will be able to very efficiently do sensitive large area 30-37 μm broad band mapping. In addition the B-BOP instrument will provide accurate polarimetric imaging at 70, 220 and 350 μm With this exceptional leap in performance, new domains in infrared astronomy will become accessible, allowing us, for example, to unravel definitively galaxy evolution and metal production over cosmic time, to study dust formation and evolution from very early epochs onwards, and to trace the gas, dust and ice evolution in planetary systems