Authors

Natalia Yaitskova(1), Kjetil Dohlen(2), Patrick Rabou(3), Anthony Boccaletti(4), Marcel Carbillet(5), Jean-Luc Beuzit(3), Markus Kasper(1), Norbert Hubin(1)

Affiliations

(1) ESO; (2) LAM; (3) LAOG; (4) LESIA; (5) FIZEAU

Abstract

SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research) is VLT instrument for the discovery and study of new extra-solar giant planets orbiting nearby stars by direct imaging of their circumstellar environment. SPHERE is a complex instrument containing more than 50 optical surfaces. The optical imperfections of each of these surfaces might influence the final contrast. SPHERE has several observing modes in Visible and Infrared, and therefore several optical paths.

FOROS is an end-to-end optical propagation code for SPHERE, which includes almost all surfaces of the instrument. It models the instrument by the sequential blocks: VLT, Foreoptics, Corrective Optics, Coronagraph and so on, such that the beam quality can be studied at several selected locations. The Vis and IR paths are separated in the model. It incorporates the real data of surface measurement, according to the availability of this data; otherwise the surface error is simulated according to the existing specifications. Each surface error can be switched on and off; therefore the influence of each surface on the contrast can be studied independently.

FOROS is an IDL-PROPER-based code, the main power of which is Fresnel propagation. Therefore it represents a numerical tool to study the Fresnel diffraction effects in SPHERE. In the paper we describe the structure and philosophy of the code, and present some results of the end-to-end modeling.