SPICA/SAFARI will provide the next step in far-infrared astronomical research after the Herschel-HIFI mission. The mirror of the joint European-Japanese space telescope will be cooled to almost absolute zero (-273 °C). As a result the detectors will no longer be ‘blinded' by the thermal radiation coming from the mirror itself, and therefore the SPICA instruments can detect infrared sources two orders of magnitude weaker than Herschel.
SPICA will be able to look far deeper into space than Herschel, for instance to investigate how the first galaxies were formed. SAFARI, the 'nerve center' of the space telescope, is being developed under the leadership of SRON.
SAFARI will be an infrared spectrometer that will be able to fully utilize the sensitivity of the extremely cool mirror. Not only to search for the first and oldest galaxies in the far infrared but also for ice and water vapor in protoplanetary discs. Before reaching this goal, several important milestones have to be passed first.
Late 2016 the SPICA team submitted a proposal in response to ESA's call for a medium-size mission opportunity (M5). Results of this call are expected in the near future. Meanwhile the SAFARI team faces the technological challenge of developing the ultra-sensitive detectors, which will form the heart of SAFARI.
Understanding the origin and evolution of galaxies, stars, planets and life itself is a fundamental objective of astronomy. Although impressive advances have been made, our knowledge of how the first galaxies and stars formed, and how they evolved into what we see around us today, is still far from complete. A major reason for this is that the birth and much of the growth of galaxies, stars and planets occurs in regions that are hidden by a thick blanket of dust – virtually inaccessible to the optical instruments that have been the main tools of the trade since the invention of the telescope. In the infrared, it is possible to penetrate this obscuring dust and trace a vast array of spectral diagnostics both in the local universe and at high redshift.
SPICA's science goals
A prime goal of SPICA is to reveal the physical processes that govern the formation and evolution of galaxies and black holes over a significant fraction of cosmic time. With sensitive infrared spectroscopy astronomers will obtain the first accurate measurement of both the star formation and black hole accretion rates in dusty galaxies over more than 90% of the age of the Universe.
SPICA will furthermore, for the first time, resolve the far-infrared polarization, and therefore the magnetic field, of galactic filaments which play a critical role at the onset of the star-formation process. Additionally, the spectroscopic capabilities of SPICA will shed light on the nature of the turbulent gas and the way in which the compressional energy is dissipated through filament and core assembly, providing the experimental basis to advance theories of star formation within molecular clouds.
A third key objective of SPICA is the understanding of the formation and evolution of planetary systems. Planet formation is deeply linked to the evolution of the gas reservoir, which can be uniquely traced in planet-forming systems with observations of the HD molecule. SPICA will characterize the warm gas disc mass down to the gas dispersal stage. Thanks to SPICA's mid-IR high spectral resolution capabilities, the gas dispersal in planet forming systems will be measured using a unique set of molecular/atomic and ionised gas tracers. Furthermore, SPICA will uniquely probe multiple phases of water (warm and cold vapour, and ice), which cannot be observed from Earth, through the entire planet forming reservoir. The study of water, throughout the evolution of planet forming systems, will also help us understand the emergence of water in the Solar System and its delivery to the still-forming Earth.
SPICA's two instruments, SAFARI, a joint European-Canadian-US contribution, and SMI from Japan, together provide several modes of operation with high resolution R~28000 spectroscopy in the mid-infrared (12-18μm) and low (R~150) to medium (R up to 11000) resolution spectroscopy instantaneously over the full 17 to 35 μm and 35 to 230 μm ranges, at a sensitivity of a few times 10-20 Wm-2 (5σ, 10hr). Additionally, SMI provides 10’×12’ wide field imaging in the mid-infrared at 34 μm and SAFARI delivers imaging polarimetry in the far infrared.
The SPICA telescope design and manufacture builds directly on the legacy of Herschel, further enhancing the mission’s reliability. SRON has been playing a leading role in the SAFARI project largely based on SRON's prominent role in the development of infrared detectors. Gaining maximum benefit from the low infrared emission of SPICA’s cooled mirror, requires the use of detectors that are several orders of magnitude more sensitive than those of Herschel.
SAFARI is a very different instrument from HIFI. HIFI 'sees' just a small part of the cosmos but with a very high spectral resolution. SAFARI is, in effect, a multicolor infrared camera with about 6000 pixels that can make real ‘photos’ of the cosmos at a range of different wavelengths.