arXiv subjects

Alexis Carlotti

Publications and source records attributed to Alexis Carlotti.

38 records · Page 3Linked to original sources

arXiv2012

Scientific Design of a High Contrast Integral Field Spectrograph for the Subaru Telescope

Ground-based telescopes equipped with adaptive-optics (AO) systems and specialized science cameras are now capable of directly detecting extrasolar planets. We present the expected scientific capabilities of CHARIS, the Coronagraphic High Angular Resolution Imaging Spectrograph, which is being built for the Subaru 8.2 m telescope of the National Astronomical Observatory of Japan. CHARIS will be implemented behind the new extreme adaptive optics system at Subaru, SCExAO, and the existing 188-actuator system AO188. CHARIS will offer three observing modes over near-infrared wavelengths from 0.9 to 2.4 microns (the y-, J-, H-, and K-bands), including a low-spectral-resolution mode covering this entire wavelength range and a high-resolution mode within a single band. With these capabilities, CHARIS will offer exceptional sensitivity for discovering giant exoplanets, and will enable detailed characterization of their atmospheres. CHARIS, the only planned high-contrast integral field spectrograph on an 8m-class telescope in the Northern Hemisphere, will complement the similar instruments such as Project 1640 at Palomar, and GPI and SPHERE in Chile.

astro-ph.IM↗

arXiv2011

Design of PIAA coronagraphs over square apertures

The purpose of this paper is to present the results of a theoretical study pertaining to the feasibility of PIAA units using Deformable Mirrors. We begin by reviewing the general derivation of the design equations driving PIAA. We then show how to solve these equations for square apertures and show the performance of pure PIAA systems in the ray optics regime. We tie these design equations into the study of edge diffraction effects, and provide a general expression for the field after a full propagation through a PIAA coronagraph. Third, we illustrate how a combination of pre and post apodisers yields to a contrast of 10^10 even in the presence of diffractive effects, for configuration with neither wavefront errors or wavefront control. Finally we present novel PIAA configurations over square apertures which circumvent the constraints on the manufacturing of PIAA optics by inducing the apodisation with two square Deformable Mirrors (DM). Such solutions rely on pupil size smaller than currently envisioned static PIAA solutions and thus require aggressive pre and post-apodizing screens in order to mitigate for diffractive effect between the two mirrors. As a result they are associated to significant loss in performance, throughput in particular.

astro-ph.IM↗