Spectro-Polarimetric High-contrast Exo-planet REsearch



SPHERE is a project to directly image extra-solar planets on a VLT unit telescope (UT) on ESO's Paranal observatory. This ambitious goal will be achieved by constructing an instrument that offers a unique combination of eXtreme Adaptive Optics (XAO), coronography, and three differential imaging-capable focal plane instruments:

  • ZIMPOL, an innovative and state-of the art differential polarimeter working at visual to very near infra-red wavelengths.
  • IRDIS, a dual imager working in the NIR band J, H, and K.
  • IFS, an integral field spectrograph working in J-band, the concept of which will allow to exceed the contrast limits of conventional differential imaging by a factor of 10.
The instrument will be operated in survey mode and spent about 500 nights searching the sky for nearby exo-planets of Jupiter-size and at ages ranging from a few million years to some gigayears.

Science The search for other planetary systems, evidence for life on other planets and the fundamental understanding how planets form are key questions of modern astrophysics. The detection of extrasolar planets by the Doppler wobble of their host star has been one of the greatest astronomical achievements of the last century. The detection of direct light from extrasolar planets and the characterization of their atmospheres is the next great challenge in this field. SPHERE is our answer to this vision. SPHERE has the primary science goal to image and characterize extrasolar planets around nearby stars ranging in age from 10 Myrs to 10 Gyrs.

Consortium The consortium to conduct the SPHERE project consists of 12 major european astronomy institutions plus a number of smaller partners. The head institute is the Laboratoire d'Astrophysique de l'Observatoire de Grenoble (France). Key personnel of the consortium are

  • Jean-Luc Beuzit (P.I., LAO Grenoble)
  • Markus Feldt (Co-P.I., MPIA Heidelberg)
  • David Mouillet (Project Scientist, LAO Grenoble)
  • Pascal Puget (Project Manager, LA Marseille)
  • Kjetil Dohlen (System Engineer, LA Marseille).
ESO is also part of the consortium, as well as its primary client.

Instrument The SPHERE instrument will consist of 4 major subsystems:

  • An eXtreme AO system (SAXO) using a 1600 actuator DM, thus controlling up to 1200 modes at loop frequenciws up to 1.2kHz. The system also provides a stabilized pupil for the coronagraphic system and extra-stable PSFs during calibration procedures.
  • The dual-band imaging camera IRDIS, providing simultaneous imaging in two channels throughout the J, H, and K NIR bands.
  • The 3D spectroscopic imager IFS, providing low spectral resolution imaging in J-band. This will allow to increase the contrast achievable by differential imaging by a factor of 3-10 with respect to IRDIS in certain cases.
  • The differential imaging polarimeter ZIMPOL. Its innovative lock-in technique will allow to detect terrestrial planets in orbit around α Cen by polarimetric differential imaging in Z-band

mfeldt.php, 08/2007