Prof. Niranjan Thatte

Abstract:

ATLAS is a generic Laser Tomographic AO (LTAO) system for the E-ELT. Based on modular, relatively simple, and yet innovative concepts, it aims at providing diffraction-limited images in the near infra-red for a close to 100 percent sky coverage.

Abstract:

Many of the proposed science cases for extremely large telescopes (ELT) are only possible because of the unprecedented sensitivity and spatial resolution due to advanced, e.g. tomographic and multi conjugate, adaptive optic (AO) systems. Current AO systems on 8-10 m telescopes work best at wavelengths longward of 1 μm with Strehl ratios ≥ 15%. At red-optical wavelengths, e.g. in the I band (0.8 μm), the Strehl ratio is at best a few percent. The AO point spread function (PSF) typically has a diffraction-limited core superimposed on the seeing halo, however, for a 5% Strehl ratio the core has a very low intensity above the seeing halo. At an ELT, due to a 3-4 times higher angular resolution, the diffraction limited PSF core of only 5% Strehl ratio stands more prominently atop the shallow seeing halo leading to almost diffraction limited image quality even at low Strehl ratios. Prominent ELT science cases that use the Calcium triplet can exploit this gain in spatial resolution in the red-optical: stellar populations in dense environments or crowded fields; and the case of intermediate mass black holes in nuclear and globular stellar clusters, as well as (super-) massive black holes in galaxies.

Abstract:

We present the results of a design study for an integral field spectrograph as the "back-end" instrument for spectroscopy of exoplanets carried out in the context of the EPICS Phase A study. EPICS is the planet finder imager and spectrograph for the E-ELT. In our study we investigated the feasibility of an image slicer based integral field spectrograph and developed an optical design for the image slicer and the necessary pre-optics, as well as the spectrograph optics. We present a detailed analysis of the optical performance of the design. © 2010 Copyright SPIE - The International Society for Optical Engineering.