SPIRou spectrograph

Artist’s impression of the habitable planet in the Gliese 581 system. Credit: ESO/L. Calçada.

The infrared spectropolarimeter (SPIRou) is an instrument developed in partnership with a number of institutions, including the Université de Montréal and researchers from Toulouse, Grenoble, Geneva, Taipei and Victoria. It is a spectrograph that will be able to take radial velocity measurements of low-mass stars with sufficient precision to detect Earth-size planets in their habitable zones. SPIRou is deployed on the Canada-France-Hawaii telescope in 2018 and carries an ambitious survey of exoplanets, the SPIRou Legacy Survey-Planet Search (SLS-PS).

The instrument will also provide valuable support for space missions searching for exoplanet transits, like TESSDiscovering an exoplanet during its transit gives us information about its radius and orbital period. Measurements with an instrument like SPIRou are needed to determine its mass and estimate its density and constrain its composition, however.

SPIRou will be the only instrument in the world to combine these features:

  • Stability of 1 m/s, sufficient to detect a planet in the habitable zone around a low-mass star
  • Sensitivity in the near-infrared (0.98 to 2.40 µm), covering the domain in which low-mass stars are the brightest
  • Measurement of spectral polarization, making it possible to differentiate between planet signatures and the different signals caused by the presence of spots on the star
  • Located at one of the top astronomical sites in the world, atop Mauna Kea in Hawaii

Planetary system discovered around the red dwarf Gliese 581. One of the planets in this system has a surface temperature comparable with that of Mars. Credit : Franck Selsis (CNRS) / ESO.

In addition to detecting a large number of planets in the solar neighbourhood, SPIRou is to be used for numerous other scientific projects, including:

  • Detecting the magnetic fields of stars in formation
  • Studying the atmosphere of certain exoplanets transiting in front of their stars
  • Studying the surface cloud models of brown dwarfs


The SPIRou team consists of world leaders in the instrument’s key themes:

  • The Institute team, that has designed a number of infrared instruments, many of them for the CFHT (WIRCAM, CFHTIR, MONICA) and other observatories.
  • The Research Institute in Astrophysics and Planetology and the Obseratoire Midi-Pyrénées (IRAP/OMP), based in Toulouse, designed the CFHT spectropolarimeter (ESPADONS), which operates in the optical domain, one of the most-used instruments at the CFHT at the moment. SPIRou’s spectropolarimetric module is largely based on that of ESPADONS, but adapted to infrared.
  • The Geneva and Grenoble teams consist of renowned experts in the radial velocity technique for detecting planets. HARPS, an instrument designed in Geneva and operating in Chile, is the world’s most stable radial velocity measurement instrument. It is the benchmark in this field. SPIRou’s operating mode and design are largely inspired by the success of HARPS.

The l’IRAP/OMP team hosts the official SPIRou webpage where you will find more details about the advancement of the project, the latest news and numerous pictures of parts being assembled.