SPHERE IFS: the spectro differential imager of the VLT for exoplanets search

Abstract

The SPHERE is an exo-solar planet imager, which goal is to detect giant exo-solar planets in the vicinity of bright stars and to characterize them through spectroscopic and polarimetric observations. It is a complete system with a core made of an extreme-Adaptive Optics (AO) wavefront correction, a pupil tracker and diffraction suppression through a variety of coronagraphs. At its back end, a differential dual imaging camera and an integral field spectrograph (IFS) work in the Near Infrared (NIR) Y, J, H and Ks bands (0.95 - 2.32μm), and a high resolution polarization camera covers the optical range (0.6 - 0.9 μm). The IFS is a low resolution spectrograph (R~50) working in the near IR (0.95-1.65 microns), an ideal wavelength range for the detection of giant planet features. In our baseline design the IFU is a new philosophy microlens array of about 145x145 elements designed to reduce as much as possible the cross talk when working at diffraction limit. The IFU will cover a field of view of about 1.7 x 1.7 square arcsecs reaching a contrast of 10 -7 , providing a high contrast and high spatial resolution imager able to search for planet well inside the star PSF.