The SPICA infrared space telescope has just been pre-selected by the European Space Agency (ESA) to participate in the final competition, which in September 2021 will see the choice of ESA’s next medium-sized mission (mission M5).
SPICA is a large infrared telescope (diameter 2.5 m) fully cooled to a temperature of only a few degrees above absolute zero. This concept was proposed to ESA in the competition for the M5 mission of the “Cosmic Vision” programme (25 proposals submitted) by a consortium of European research laboratories led by the Netherlands in close collaboration with the Japanese space agency (JAXA), and involving in France the CEA, the CNRS and their associated universities with the support of the CNES.
The selection of SPICA is a crucial step towards answering the major questions raised by astronomy in the 21st century: the growth and evolution of galaxies during cosmic ages can be fully characterized in the distant universe, and in our Galaxy the processes that determine the formation of stars and planetary systems such as ours can be elucidated.
The Universe Unveiled
SPICA has been designed to be extremely sensitive to light in the infrared range. These, unlike visible light, are not stopped by the cosmic dust that fills the Universe. The observation of infrared radiation therefore literally reveals whole sections of the Universe that are hidden from us, allowing us to see deep into the depths of galaxies, star-forming clouds and planet-forming systems.
One of the great questions of modern astronomy is to understand the processes that regulate the formation and evolution of galaxies. Early in the history of the Universe, about 12 billion years ago, the first stars and galaxies began to form. Over the next few billion years, this process of galaxy formation accelerated and became more and more efficient until it reached its peak about 9 billion years ago. Since that time, galaxy formation has steadily decreased. The reasons for this rise in power, the saturation of the galaxy formation process and its current decline are still widely debated. SPICA will record the spectral footprint of several thousands of galaxies distributed over this key period. This unique footprint will allow us to probe precisely the physical conditions prevailing in and around these galaxies, and thus determine the factors governing their formation and evolution.
In the Near Universe SPICA will give us a unique view of the processes that govern the formation of stars and planetary systems by combining the power of spectrometry with the power of polarimetry deep in dense regions of dust and gas that can only be explored in the infrared. Polarimetry of dust emission in nearby interstellar clouds will make it possible to characterize for the first time the morphology and strength of the magnetic field at the critical scales that trigger the collapse of gas into stars and planets within molecular filaments. Infrared spectroscopy of ions, atoms, molecules, dust grains and ice particles is a unique tool. Not only does it allow us to characterize the physical conditions in and around protoplanetary disks, but also to draw precisely the critical line that separates water vapour from the ice within them. By combining these studies with those of the dust disks and dust belts present around older planetary systems, the link can be made with our own solar system and its surrounding cloud of debris and dust, the Oort cloud, and SPICA will provide unique information about the formation of our own solar system.
The SPICA Space Observatory
SPICA will be possible thanks to the combination of several cutting-edge technological innovations. A key element will be the large 2.5-metre diameter telescope cooled to a temperature a few degrees above absolute zero in order to radically reduce the level of radiation emitted by the telescope itself. In this way, detectors that are ultra-sensitive to infrared wavelengths can be used to their maximum detection potential. The combination of the cryogenic telescope with novel detectors will make SPICA the most powerful observatory ever built for the far-infrared range – a sensitivity gain of a factor of 100 compared to the Herschel Space Observatory which has been in service from 2009 to 2013. With this extreme sensitivity SPICA is expected to revolutionize our understanding of the formation of stars, planets and galaxies.
The SPICA observatory will be developed under the project management of the European Space Agency (ESA) in partnership with the Japanese Space Agency (JAXA). It will be equipped with three focal instruments covering the entire range of infrared wavelengths between 12 and 350 micrometers. A mid-infrared spectrometer-imager (12 – 35 micrometres) will be built by a Japanese consortium led by Nagoya University under the aegis of the Institute of Space and Astronautical Science (ISAS); a far-infrared spectrometer (35 – 210 micrometres) will be built by a European consortium under the aegis of the SRON in the Netherlands; and a compact polarimetric imager will be supplied by an international consortium under the responsibility of the CEA in France.
Like all world-class observatories, on the ground or in space, SPICA will be available for use by astronomers around the world. Observing programs will be selected on the basis of scientific merit by independent experts. Proposers will be granted a one-year exclusivity to exploit their observations. After this period the data will be made public.
France is one of the founding countries of the SPICA project. In partnership with CNES, its laboratories (CEA, CNRS and Universities) will contribute to the instrumentation of the observatory through the control and characterization of key technologies: cryo-refrigerator and sub-kelvin detector arrays, electronic systems for the control of superconducting detector arrays. These achievements will be developed under the responsibility of the DAp-AIM (involving Irfu and LETI/DOPT) and the INAC/SBT of CEA, LAB (Bordeaux), IRAP (Toulouse) and IAS (Paris-Saclay). France has a very large scientific community interested in SPICA, with unique expertise in this field thanks to the Herschel and Planck space missions and the PILOT stratospheric balloon project. The French space industry, the Airbus and Thales groups, has a unique know-how for the construction of large space astronomy telescopes. It is therefore particularly well placed to win the prime contractorship for the satellite and its telescope in ESA calls for tenders.
- Martin GIARD, Directeur de recherche au CNRS, Institut de Recherche en Astrophysique et Planétologie Toulouse – IRAP, firstname.lastname@example.org