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January 18th 2019

Space telescope SPICA studies the Universe in infrared light. This radiation shoots straight through space dust, which is present all across space and blocks the view for telescopes that are sensitive to visible light. Using infrared light we peek through the dust veils, deep into the inner reaches of galaxies, starforming clouds and planet forming systems.

Astronomers want to study galaxies with SPICA (SPace Infrared telescope for Cosmology and Astrophysics) to find out which processes regulate their origin and evolution. Early in the history of the Universe, about twelve billion years ago, the first stars and galaxies started to form. In the next few billion years the process of formation and evolution sped up, becoming increasingly more efficient, until that activity peaked about nine billion years ago. Since then, the production of these megastructures has been slowing down continuously. The cause for the increase, peak and subsequent decrease of galaxy formation efficiency is still the subject of speculation. SPICA takes spectral ‘fingerprints’ of many thousands of galaxies spread over cosmic time. From these, we will be able to accurately probe the physical conditions in and around these galaxies, and thus determine the factors that govern their formation and evolution.

Within our own Galaxy, SPICA will provide detailed insight into the formation process of stars and planetary systems. This happens deep inside dense dusty clouds and can only be traced well in the infrared. Also here we use a spectral fingerprint, to determine the physical conditions in and around the planet forming disk. It reveals which atoms and molecules are the essential ingredients for planet formation. In addition, SPICA will allow us to establish where in the planet forming disk water is solid or gaseous, so we can chart the 'snowline'. For more evolved planetary systems, SPICA characterizes the outer asteroid ring - the 'construction waste'. In our Solar System we call this ring the Oort cloud. It gives direct insight into the origins of our own Solar System.

A consortium led by SRON is responsible for SPICA's biggest and most complex instrument: the far-infrared spectrometer SAFARI. Transition Edge Sensors (TES) form SAFARI's heart. These detectors are developed by SRON and only reach their maximum potential if there is minimum background noise from the telescope. Therefore SPICA is constantly cooled to six degrees above absolute zero. It makes SPICA the most sensitive telescope ever in the mid- and far-infrared.

Almost twenty institutes from fifteen countries work on the SAFARI project. Each institute brings its own expertise. SRON is system architect, carries final responsibility and delivers together with the United States and the United Kingdom the TES expertise. France provides the cooling system, Spain the optics and instrument structure and Canada an interferometer. Other contributions come from Austria, Belgium, Denmark, Germany, Ireland, Italy, Japan, Sweden, Switzerland and Taiwan.

SAFARI covers the wavelength area between 34 and 230 micrometer using over three thousand TES detectors. The telescope focusses the far-infrared radiation on the SAFARI instrument, which disperses it into different colors using a grating. For more detail in the spectral fingerprint, SAFARI has a so-called Martin-Puplett interferometer, which can be inserted into the light path. SAFARI also has a dedicated cooler to cool the TES detectors to fifty milliKelvin. The instrument can study sources weaker by more than two orders of magnitude than was possible ever before.

Apart from SAFARI, the SPICA telescope contains an additional two instruments to cover the spectrum between mid- and far-infrared: radiation of 12 to 350 micrometer wavelength. Japan provides a combination of a mid-infrared camera and spectrometer, while a European consortium led by France builds a small far-infrared camera and polarimeter.

SPICA is a collaboration between ESA and the Japanese space agency JAXA. ESA is responsible for the mission, the telescope, building the satellite support systems and integrating all parts. Japan provides the cooling system and is responsible for integrating the 'payload' - the platform with the cold telescope and instrument. Moreover, Japan takes care of launching the satellite, with an H3 rocket. The three instruments are built by consortia of scientific research institutes, with contributions from all over the globe.

In 2016, an international consortium led by SRON submitted the SPICA proposal to ESA as part of the fifth call for medium class missions (M5) in the Cosmic Vision program. A total of 25 proposals competed for the M5 budget of 550 million euro. Together with two other missions, THESEUS and EnVision, SPICA is now selected for the final round, in which three parallel detailed studies will determine the best proposal. ESA is expected to select its M5 mission in 2021. The mission should be launched around 2030.

More information
Peter Roelfsema, SAFARI Principal Investigator, SPICA Lead Proposer, +31 50 363 40 43 or  +31 o6 23 46 17 42.
Erik Arends, outreach officer SRON, +31 88 777 58 93.