Prof. Niranjan Thatte

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.

Abstract:

HARMONI is a proposed visible and near-infrared integral field spectrograph for the European Extremely Large Telescope. We are exploring the merits of adding a coronagraphic capability to HARMONI, specifically targeted at enabling observations of faint, nearby companions (primarily extra-solar planets) that require high contrast. Although HARMONI is not fed by extreme adaptive optics, we show that substantial contrasts can be achieved by post-processing of the hyperspectral data cube using spectral deconvolution. We make predictions of achievable contrast as a function of coronagraph design, based on realistic models of the telescope's aberrations. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Abstract:

Presently, dedicated instruments at large telescopes (SPHERE for the VLT, GPI for Gemini) are about to discover and explore self-luminous giant planets by direct imaging and spectroscopy. The next generation of 30m-40m ground-based telescopes, the Extremely Large Telescopes (ELTs), have the potential to dramatically enlarge the discovery space towards older giant planets seen in reflected light and ultimately even a small number of rocky planets. EPICS is a proposed instrument for the European ELT, dedicated to the detection and characterization of Exoplanets by direct imaging, spectroscopy and polarimetry. ESO completed a phase-A study for EPICS with a large European consortium which - by simulations and demonstration experiments - investigated state-of-the-art diffraction and speckle suppression techniques to deliver highest contrasts. The paper presents the instrument concept and analysis as well as its main innovations and science capabilities. EPICS is capable of discovering hundreds of giant planets, and dozens of lower mass planets down to the rocky planets domain. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Abstract:

HARMONI has been conceived as a workhorse visible and near-infrared (0.47-2.45 microns) integral field spectrograph for the European Extremely Large Telescope (E-ELT). It provides both seeing and diffraction limited observations at several spectral resolutions (R= 4000, 10000, 20000). HARMONI can operate with almost any flavor of AO (e.g. GLAO, LTAO, SCAO), and it is equipped with four spaxel scales (4, 10, 20 and 40 mas) thanks to which it can be optimally configured for a wide variety of science programs, from ultra-sensitive observations of point sources to highangular resolution spatially resolved studies of extended objects. In this paper we describe the expected performance of the instrument as well as its scientific potential. We show some simulated observations for a selected science program, and compare HARMONI with other ground and space based facilities, like VLT, ALMA, and JWST, commenting on their synergies and complementarities. © 2010 Copyright SPIE - The International Society for Optical Engineering.

Abstract:

We describe the results of a Phase A study for a single field, wide band, near-infrared integral field spectrograph for the European Extremely Large Telescope (E-ELT). HARMONI, the High Angular Resolution Monolithic Optical & Nearinfrared Integral field spectrograph, provides the E-ELT's core spectroscopic requirement. It is a work-horse instrument, with four different spatial scales, ranging from seeing to diffraction-limited, and spectral resolving powers of 4000, 10000 & 20000 covering the 0.47 to 2.45 μm wavelength range. It is optimally suited to carry out a wide range of observing programs, focusing on detailed, spatially resolved studies of extended objects to unravel their morphology, kinematics and chemical composition, whilst also enabling ultra-sensitive observations of point sources. We present a synopsis of the key science cases motivating the instrument, the top level specifications, a description of the opto-mechanical concept, operation and calibration plan, and image quality and throughput budgets. Issues of expected performance, complementarity and synergies, as well as simulated observations are presented elsewhere in these proceedings[1]. © 2010 Copyright SPIE - The International Society for Optical Engineering.