Ristretto project #
RISTRETTO is an instrumental project to detect the reflected light of nearby exoplanets using the spectroscopic coronagraphy technique.
Once ready this instrument will be proposed as a visitor instrument for the ESO VLT/AOF facility.
In the first phase a single-mode high-resolution spectrograph with 7 spaxels will be built and tested on the Euler 1.2m telescope in La Silla with the KalAO adaptive optics system.
High-contrast imaging in the visible
In order to achieve its goal, the instrument needs a XAO system in the visible giving at the same time the highest possible Strehl (to efficiently couple to the single-mode fibers that feed the spectrograph) and a high raw contrast in order to be able to detect the planet light. The average target value for the contrast is 10-4.
In order to achieve the required total contrast (in the 10-7 range) to detect the reflected light of the planet one will use a high-resolution spectrograph coupled to an integral-field unit in order to locate the planet. The additional gain in contrast is obtained thanks to the radial velocity difference between the planet and its host star.