Prof. Niranjan Thatte

Abstract:

We describe the current status of the HARMONI instrument design, which will form the basis for the first-light integral field spectrograph on the European Extremely Large Telescope. We review the phase A design, and highlight current on-going work to evolve the design in-line changing telescope requirements and lessons learned during the Phase A work. We also outline the key science drivers for the instrument, and describe briefly the requirements for the laser tomographic adaptive optics system which is expected to feed HARMONI.

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.